TREATISE   ON 
GENERAL   AND    INDUSTRIAL 

ORGANIC    CHEMISTRY 


ALSO  BY  DR.  MOLINARI 
TREATISE  ON 

GENERAL  AND  INDUSTRIAL 
INORGANIC   CHEMISTRY 

TRANSLATED  BY 

DR.  ERNEST  FEILMANN 

B.Sc.,  Ph.D.,  F.I.C. 
With  280  Text-Figures  and  3  Plates 


TREATISE   ON 

GENERAL  AND  INDUSTRIAL 

ORGANIC  CHEMISTRY 


BY 

DR.    ETTORE   MOLINARI 

Professor  of  Industrial  Chemistry   to  the  Society   for  the 

Encouragement  of  Arts  and  Manufactures  and 

of  Merceology  at  the  Luigi  Bocconi 

Commercial  University,  Milan 


TRANSLATED  FROM  THE  SECOND  ENLARGED  AND  REVISED 
ITALIAN  EDITION  BY 

THOMAS   H.    POPE 
B.Sc.,  A.C.G.I.,  F.I.C. 

School  of  Malting  and  Brewing, 
University  of  Birmingham 


WITH  506  ILLUSTRATIONS 


PHILADELPHIA 
P.  BLAKISTON'S  SON  &  CO. 

1012  WALNUT  STREET 
1913 


T  P  I 


Ml**.  MM    O  • 


Printed  in  Great  Britain 


'  * 

.  .*  -  • 

->   • 


TRANSLATOR  S  PREFACE 

FOR  the  purposes  of  this  English  translation  of  his  "  Trattata  di  Chimica 
Organica,"  the  author  has  made  a  number  of  alterations  in  and  additions  to 
the  text  of  the  second  Italian  edition,  these  consisting  principally  in  ampli- 
fications of  the  statistical  data  referring  to  Great  Britain  and  the  United 
States. 

It  has  been  deemed  undesirable  to  convert  the  metric  weights  and  measures 
into  those  of  the  English  system,  but,  in  general,  prices  are  given  in  British 
currency,  twenty-five  lire  being  taken  as  the  equivalent  of  one  pound  sterling. 
Where  quantities  are  given  in  tons,  the  latter  are  to  be  read  as  metric  tons  of 
1000  kilograms  or  2204' 6  Ib.  avoirdupois. 

The  abbreviations  employed  for  the  different  units  of  weights  and  measures 
are  those  in  common  use,  and  temperatures  are  expressed  in  degrees  Centigrade 
in  all  cases. 

THOMAS  H.   POPE 
BIRMINGHAM 


267544 


PREFACE   TO   THE    SECOND   ITALIAN 

EDITION 

THE  first  edition  of  this  treatise  on  Organic  Chemistry  was  published  in 
two  volumes  in  1908  and  1909,  and  rapidly  exhausted,  the  second  edition 
being  now  published  in  one  volume.  The  distribution  of  the  matter  is  similar 
to  that  of  the  first  edition,  but  many  chapters  have  been  brought  up  to  date, 
others  have  been  considerably  amplified  and  others  again  have  been  introduced 
for  the  first  time.  The  largest  additions  have  been  made  in  the  chapters 
dealing  with  the  treatment  of  tar,  with  colouring-matters,  with  alkaloids,  &c. 

The  statistics  of  production,  exportation,  and  importation  have  been 
brought  up  to  the  year  1910  and,  where  possible,  to  1911.  Special  attention 
has  been  devoted  to  this  characteristic  feature  of  the  book,  as  experience  has 
shown  the  author  that  among  the  most  important  factors  in  deciding  the 
possibility  or  convenience  of  starting  new  or  of  extending  existing  industries 
are  those  governed  by  the  laws  of  economics  and  statistics. 

The  author  will  be  grateful  to  any  readers  or  colleagues  who  may  point  out 
omissions  or  errors,  which  are  unavoidable  in  a  work  of  this  character  with 
such  varied  contents  in  so  condensed  a  form. 

This  second  edition  is  in  course  of  translation  into  English  and  German. 


E.  MOLINARI 
MILAN 


PREFACE   TO   THE   FIRST   ITALIAN 
EDITION 

A  NEW  treatise  on  Organic  Chemistry  might,  in  view  of  the  existence  of  the 
excellent  works  of  Bernthsen  and  Holleman,  be  considered  superfluous. 

But  both  of  these  books,  which  differ  little  in  the  manner  in  which  the 
subject  is  developed,  are  confined  to  a  theoretical  and  systematic  exposition 
of  the  many  organic  compounds,  the  industrial  side  of  the  question  and  the 
applications  of  these  compounds  being  almost  entirely  neglected.  It  is  hence 
difficult  for  the  student  to  ascertain  which  of  the  thousands  of  substances 
described  are  really  of  practical  importance. 

Modern  teaching  of  chemistry  adheres  in  a  too  one-sided  manner  to  the 
old  but  fruitful  idea  of  Liebig,  that  "  to  obtain  a  sound  practical  man  it  is 
necessary  to  train  a  good  theorist."  This  conception  was  taken  too  literally, 
although  it  gave  good  results  when  chemical  industry  was  in  its  infancy, 
since  in  those  days  any  theorist  could  easily  introduce  new  and  important 
methods.  But  to-day,  when  the  industry  has  attained  the  adult  stage — has 
advanced  to  such  an  extent  and  become  so  varied  and  complex,  being  stimulated 
incessantly  by  keen  national  and  international  competition,  which  demands 
rapid  changes  and  improvements — the  valuable  time  of  the  young  technician 
cannot  be  wasted  in  a  protracted  and  sometimes  sterile  apprenticeship.  Present- 
day  conditions  require,  therefore,  some  such  expansion  of  Liebig's  maxim  as  the 
following  :  In  order  to  produce,  rapidly  and  with  increased  certainty,  a  sound, 
practical  man,  it  is  necessary  to  train  a  good  theorist  and  to  initiate  him  into 
both  the  theoretical  and  practical  study  of  the  more  salient  industrial  problems. 

It  does  not  suffice  that  the  young  chemist,  about  to  begin  his  industrial 
or  teaching  career,  should  have  a  thorough  knowledge,  for  instance,  of  the 
various  syntheses  and  constitutional  formulae  of  the  sugars.  He  should  also 
be  acquainted  with  at  least  the  general  outlines  of  the  industrial  processes  and 
of  the  technique  of  the  manufacture  of  sugar,  beginning  with  the  slicing  of  the 
beets  and  proceeding  to  the  exhaustion  of  the  pulp,  defecation,  saturation, 
filtration  with  filter- presses,  boiling,  and  vacuum  concentration  in  multiple- 
effect  apparatus,  refining  and  centrifugation  of  sugar  crystals,  utilisation  of 
residues,  and  so  on.  He  should,  indeed,  understand  the  plant  and  chemical 
processes  of  the  more  important  industries,  as  these  often  find  application 
in  the  manufacture  of  products  of  a  secondary  or  entirely  new  character. 

What  would  avail  a  study  of  the  wonderful  artificial  colouring-matters 
derived  from  coal-tar,  with  the  inexhaustible  syntheses  composing  their  theo- 
retical basis,  if  it  were  limited  to  a  simple  mnemonic  exercise  for  the  student 
and  no  notice  were  taken  of  the  interesting  practical  applications  to  the  dyeing 
of  the  various  textile  fibres  ? 

Nor  should  the  young  student  ignore  statistics  of  production  ;  he  should 
be  able  to  appreciate  the  importance  of  variations  in  the  exportation  and 
importation  of  the  principal  chemical  products,  and  to  judge  of  the  economic 
and  social  conditions  with  which  such  variations  correspond. 

After  a  brief  novitiate,  he  should  be  in  a  position  to  point  out  the  more 
striking  technical  defects  and  the  more  marked  difficulties  met  with  in  par- 
ticular industrial  processes  and  to  suggest  rational  and  not  fanciful  remedies 


viii  PREFACE 

It  is  this  space,  the  vacant  region  representing  a  suitable  fusion  of  theoretical 
with  applied  chemistry,  which  requires  filling.  This  I  have  attempted  in  the 
present  work,  which  of  itself  is  certainly  insufficient  to  cover  the  whole  of  the 
ground. 

The  difficulties  encountered  in  preparing  the  volume  on  Inorganic 
Chemistry  are  multiplied  in  dealing  with  Organic  Chemistry,  and  this  is  the 
case  not  only  as  regards  the  collection  and  confirmation  of  the  statistical 
data  but  of  the  chemical  processes  giving  the  best  results  in  practice.  For  in 
any  particular  industry  it  has  often  been  found  that  the  results  of  investigations 
are  in  such  disaccord  with  the  practical  data  as  to  render  it  a  matter  of  great 
uncertainty  what  conclusions  should  be  presented  to  the  reader. 

Inquiries  addressed  to  manufacturers  resulted  in  aggravation  of  this 
uncertainty,  what  was  confirmed  on  the  one  hand  being  denied  on  the  other, 
and  plant  guaranteed  by  one  firm  to  be  the  best  being  decried  by  a  competing 
firm.  It  hence  became  necessary  to  apply  directly  to  the  operatives  working 
a  given  process  and  to  draw  conclusions  from  the  whole  of  the  data  and 
information  thus  obtained. 

It  is  thus  that  readers  may  explain  the  contradictions  between  different 
authorities  on  one  and  the  same  subject,  and  also  the  fact  that  the  conclusions 
reached  by  the  author  with  reference  to  certain  industrial  processes  are  not 
always  in  accord  with  those  given  in  other  treatises. 

The  intention  has  certainly  not  been  to  prepare  a  complete  treatise  on 
technological  chemistry  and  still  less  on  chemical  technology.  The  work 
having  to  be  restricted  within  limits  of  space  approximating  to  those  of  vol.  i, 
the  author  has  descended  to  details  only  with  some  of  the  principal  industries 
and  especially  with  those  best  adapted  to  give  a  general  idea  of  the  different 
applications  of  chemical  processes  and  of  chemical  technics. 

To  this  end  the  author  has  dwelt  preferably  on  the  industries  of  illuminating 
gas,  sugar,  alcohol,  beer,  acetic  acid,  dyeing,  textile  fibres,  fats  and  soaps, 
explosives,  &c. 

From  these  examples  the  student  may  gather  much  instruction  applicable 
to  many  other  industries  not  dealt  with  in  detail. 

Repetition  has  been  avoided  and  time  and  space  saved  by  frequent  references 
to  arguments  already  developed  in  vol.  i,  "  Inorganic  Chemistry." 

Advice  and  collaboration  are  desired  from  readers  and  colleagues  in  order 
that  gaps  in  the  present  work  may  be  filled  and  inaccuracies  and  defects 
remedied. 

E.  MOLINARI 

MILAN 


CONTENTS 
PART  I.    GENERAL 

PAOE 

PURIFICATION  OF  ORGANIC  COMPOUNDS  2 

Crystallisation,    2 ;     sublimation,    boiling-point,    fractional    distillation,    2 ; 
rectification,  3  ;   melting-point,  5  ;   specific  gravity,  6. 

ANALYSIS  OF  ORGANIC  COMPOUNDS  6 

Qualitative  composition,  6 ;  quantitative  estimation :  of  carbon  and 
hydrogen,  7  ;  of  nitrogen,  10 ;  of  halogens,  11;  of  sulphur  and  phos- 
phorus, 12. 

CALCULATION  OF  EMPIRICAL  FORMULA  12 

DETERMINATION  OF  MOLECULAR  WEIGHT  BY  CHEMICAL  MEANS  13 

POLYMERISM  14 

VALENCY  OF  CARBON,  CONSTITUTIONAL  FORMULA,   ISOMERISM  14 

Theory  of  radicals  and  types,  14 ;  structural  formulae,  16 ;  rational 
formulae,  17. 

METAMERISM,  PSEUDOISOMERISM,  TAUTOMERISM,  DESMOTROPY  17 

STEREOISOMERISM  OR  SPACE  ISOMERISM  18 

Stereoisomerism  in  derivatives  with  doubly  linked  carbon  (alloisomerism), 
21  ;  Stereoisomerism  of  nitrogen,  22  ;  separation  and  transformation  of 
stereoisomerides,  22. 

HOMOLOGY  AND  ISOLOGY  23 

PHYSICAL  PROPERTIES  OF  ORGANIC  COMPOUNDS  IN  RELATION  TO 
THE  CHEMICAL  COMPOSITION  AND  CONSTITUTION  23 

Crystalline   form,    24 ;     solubility,    24 ;     specific   gravity,    24 ;     molecular 

volume,  24  ;    melting-point,  24  ;    boiling-point,  24  ;    heat  of  combustion  and 

of  formation,  25  ;  heat  of  neutralisation,  25.   Optical  Properties  :  colour,  26  ; 

refraction,  26  ;  influence  on  polarised  light,  26  ;  magnetic  rotatory  power,  27. 

Electrical  conductivity,  27. 

CLASSIFICATION  OF  ORGANIC  COMPOUNDS  28 

OFFICIAL  NOMENCLATURE  28 


PART  II.     DERIVATIVES  OF  METHANE 

AA.  HYDROCARBONS 

(a)  SATURATED  HYDROCARBONS  30 

Natural  formation  and  general  methods  of  preparation,  30  ;  table  of  satu- 
rated hydrocarbons,  31  ;  Methane,  32  ;  properties,  preparation,  fire-damp, 
detonating  mixtures,  industrial  preparation,  33-34 ;  Ethane,  34  ;  Propane, 
35  ;  Butanes,  35  ;  Pentanes,  35 ;  Hexanes,  35 ;  Higher  Hydrocarbons,  36. 


x  CONTENTS 

PA  OK 

Illuminating  Gas  Industry  :  history,  36 ;  components,  38 ;  pro- 
perties, 38 ;  retorts,  38 ;  furnaces,  41  ;  hydraulic  main,  43  ;  washing,  44  ; 
purification,  46  ;  exhausters,  48  ;  pressure  regulators,  48  ;  gasometers,  48  ; 
pressure  regulators,  49  ;  gas-meters,  50  ;  yield,  51  ;  statistics,  52  ;  physical 
and  chemical  testing  of  illuminating  gas,  53 ;  comparison  of  different 
sources  of  light,  57  ;  Oil  Gas,  57. 

Petroleum  Industry  :  localities  of  production,  58 ;  hypotheses  on  the 
origin  of  petroleum,  59  ;  composition  and  properties  of  crude  petroleum,  62  ; 
industrial  extraction  and  working  of  petroleum,  64  ;  distillation,  66  ;  chemical 
purification,  68 ;  storage  tanks,  69 ;  statistics,  70.  Treatment  of  crude 
benzine,  73. 

Treatment  of  Petroleum  Residues  :  A.  Mineral  lubricating  oils,  74 ; 
requirements  and  analysis  of  lubricating  oils,  77.  B.  Vaseline,  gelatinised 
vaseline  oil,  80.  C.  Paraffin  wax,  80;  different  sources:  (1)  pyropissite, 
81  ;  tar,  81  ;  photogen,  82  ;  tar,  asphalt,  pitch,  and  bitumen,  83  ; 
(2)  bituminous  shale,  83  ;  (3)  ozokerite  and  cerasin,  85. 

(ft)  UNSATURATED  HYDROCARBONS  87 

T.  Ethylene  Series  (alkylenes  or  olefines),  CraH2n,  87 ;  official  nomen- 
clature, 87 ;  constitution,  methods  of  preparation,  88.  Ethylene,  propylene, 
butylenes,  amylenes,  cerotene,  and  melene,  89-90. 

II.  Hydrocarbons  of  the  Series  CwH2n_2  :   A.    With  two  double   Unkings 
(diolefines  or  allenes) :  allene,  erythrene,  isoprene,  piperylene,  diallyl,  conylene, 
90.     B.    With  a   triple  linking  (acetylene  series)  :    metallic  acetylides,  acety- 
lene, 90-94. 

III.  Hydrocarbons  of  the  Series  CnH2M_4  and  Cn~H2n-6'  94. 


BB.  HALOGEN  DERIVATIVES  OF  HYDROCARBONS 

Table  of  the  halogen  derivatives  f)5 

I.  Halogen  Derivatives  of  Saturated  Hydrocarbons  :    properties,   94  ; 
preparation,     95-96.      Methyl     chloride,     96.      Methyl    iodide,     97.      Ethyl 
chloride,  97.     Isopropyl   iodide   and    butyl   iodides,  97.     Methylene,  ethylene, 
and  ethylidene  halogen  derivatives,  98.     Chloroform,  98-100.     lodoform,  100. 
Polychloro-derivatives,  101. 

II.  Halogen  Derivatives    of  Unsaturated  Hydrocarbons,    102;    allyl 
chloride,  102. 

CC.  ALCOHOLS 

I.  SATURATED  MONOHYDRIC  ALCOHOLS  103 

Nomenclature,  102.  Methods  of  formation  of  monohydric  alcohols.  104. 
Table  of  monohydric  saturated  alcohols,  105.  Methyl  Alcohol,  106-108. 
Ethyl  Alcohol,  108.  Solid  alcohol,  109.  Bacteriology,  110.  Enzymes,  111. 
Oxydases,  peroxydases,  112.  Biogen  hypothesis,  toxins,  liquid  crystals, 
origin  of  life,  114.  Industrial  preparation  of  alcohol :  prime  materials,  116. 
Alcoholic  fermentation,  121.  Yeasts  and  ferments,  122.  Factors  facilitating 
or  retarding  fermentation,  126.  Losses  and  yields,  128.  Table  for  the 
calculation  of  the  attenuation  of  fermented  saccharine  worts,  130.  Dis- 
tillation of  fermented  liquids,  132.  Rectification  of  alcohol,  138.  Other 
raw  materials  for  alcohol  manufacture,  140.  Alcohol  from  fruit,  141. 
Alcohol  from  woody  matter,  142.  Alcohol  from  wine,  lees,  withered  grapes, 
143.  Refining  and  depuration  of  spirit,  144.  Fusel  oil,  144.  Alcohol 
meters,  146.  Alcoholometry  and  tests  for  alcohol,  146.  Windisch's  table, 
148.  Alcoholism  and  alcohol-free  wines,  150.  Statistics,  149.  Denatured 
alcohol  for  industrial  purposes,  152.  Distillery  residues,  153. 


CONTENTS  xi 

PAGE 

Alcoholic  Beverages  :  Wine,  155.    Marsala,  159.    Vermouth,  159.    Cider,"] 
159.     Liqueurs,  159.     Fermented  milk  (kephir,  koumiss),  160. 

Beer,  161  :  barley,  hops,  water,  germination,  kilning  of  malt,  mashing, 
Balling's  table,  161-168  ;  infusion  and  decoction  mashing,  168 ;  boiling  of 
the  wort  with  hops,  170 ;  fermentation,  171  ;  attenuation,  174.  The 
Nathan-Bolze  rapid  process,  175  ;  racking,  pitching  of  casks,  176  ;  pasteurisa- 
tion, 177  ;  alcohol-free  beer,  178  ;  composition  of  beer,  178  ;  analysis  of 
beer,  178;  statistics,  179. 

Higher  Alcohols,  180  ;   propyl,  butyl,  amyl,  &c.,  180. 

II.  UNSATURATED    MONOHYDRIC    ALCOHOLS  :    vinyl,  allyl,   propargyl, 

&c.,  182. 

III.  POLYHYDRIC  ALCOHOLS.    (A)  Dihydric  Alcohols  or  glycols,  182.    (B)  Tri- 
hydric  alcohols.-  glycerol,  183.     (C)  Tetra-  and  poly-hydric  alcohols:    acetyl 
number,  188.     Erythritol,  arabitol,  mannitol,  dulcitol,  sorbitol,  189-190. 


DD.  DERIVATIVES  OF  ALCOHOLS 

(A)  DERIVATIVES  OF  MONOHYDRIC  ALCOHOLS  190 

I.  Ethers,  190  ;    methyl   ether,  192  ;    ethyl  ether :    properties,  industrial 
preparation,  192. 

II.  Thioalcohols  and  Thioethers,  195. 

III.  Alkyl  Derivatives  of  Inorganic  Acids,  196:    (1)  of  sulphuric  acid, 
197  ;   (2)  of  sulphurous  acid,  197  ;   (3)  of  nitric  acid,  197  ;   (4)  of  nitrous  acid, 
197  ;    (5)  nitro-derivatives  of  hydrocarbons,   197  ;    (6)  various  acids,   198  ; 
(7)  Derivatives  of  hydrocyanic  acid  :  (A)  Nitriles  ;   (B)  Isonitriles,  198-199. 

IV.  Alkyl  Nitrogenous  Basic  Compounds  (amines),  200  ;  methylamine, 
dimethylamine,    ethylamine,    201  ;     triethylamine,    202 ;     alkylhydrazines, 
azoimides,  a-  and  /3-alkylhydroxylamines,  diazo- compounds,  202. 

V.  Phosphines,   Arsines,   and    Alkyl-metallic  Compounds.      Grignard 
reaction,  202-203. 

VI.  ALDEHYDES  AND  KETONES  204 

(a)  Aldehydes :  Functions,  constitution,  chemical  properties,  204. 
Aldoximes,  hydrazones,  semicarbazones,  hydroxamic  acid,  206.  Form- 
aldehyde :  preparation,  properties  and  analysis,  206.  Acetaldehyde, 
acetal,  208.  Higher  aldehydes,  209.  Chloral  and  its  hydrate,  209. 
Aldehydes  with  unsaturated  radicals :  acrolei'n,  crotonaldehyde,  citral, 
&c.,  209. 

(6)  Ketones :  Properties,  preparation,  210.  Acetals,  sulphonal, 
thioketones,  ketoximes,  phenylhydrazones,  isonitrosoketones,  210. 
Acetone,  211  ;  mesityl  oxide,  phorone,  butanone,  212.  JCetenes,  212. 

(B)  DERIVATIVES  OF  POLYHYDRIC  ALCOHOLS  213 

Glycolsulphuric  acid,  Ethylenecyanohydrin,  Ethylene  oxide,  213;  Taurine, 
Glycide  alcohol,  Glycerophosphoric  acid,  214.     Nitric  ethers  of  glycerol,  215. 

Explosives  :  Theory  of  explosives,  215.  Chemical  reactions  of  explosives  : 
heat  of  explosion,  216  ;  temperature  of  ignition,  217  ;  mechanical  work  of 
'  explosives,  217  ;  pressure  of  the  gases,  218  ;  charging  density,  218  ;  crushers, 
219;  specific  pressure,  219.  Velocity  of  explosion,  219;  shattering  and 
progressive  explosives,  219  ;  velocity  of  combustion,  219  ;  initial  shock 
and  course  of  explosion,  220  ;  determination  of  explosion,  220  ;  explosive 
wave,  221  ;  explosion  by  influence,  221.  Classification  of  explosives,  222. 
Nitroglycerines,  222.  Trinitroglycerine,  223.  Manufacture  of  nitroglycerine, 
225.  Dynamites,  229  :  with  inactive  bases,  230  ;  with  active  bases,  230. 


xii  CONTENTS 

PAGE 

Nitrocellulose,  232.  Guncotton :  preparation,  manipulation,  compression, 
233-239.  Collodion  cotton  for  gelatines,  239.  Smokeless  powders,  240. 
Powders  with  picrate  bases,  245.  Explosives  of  the  Sprengel  type,  245. 
Safety  explosives,  246.  Black  powder,  248.  Various  powders,  254.  Deto- 
nators, 255.  Mercury  fulminate,  255.  Caps,  cartridges,  fuses,  255.  Destruc- 
tion of  explosives,  256.  Storage  and  preservation  of  explosives,  258.  Analysis 
of  explosives,  259.  Ballistic  tests  of  explosives,  261.  Uses,  263.  Statistics, 
263. 

EE.  ACIDS 

I.  MONOBASIC  SATURATED  FATTY  ACIDS,  CnH2n02  264 

Table,  265.  General  methods  of  preparation,  264.  Coefficients  of  affinity, 
266.  Separation,  267  ;  constitution,  268.  Formic  Acid,  268.  Acetic  Acid, 
270  :  Oudemann's  table  of  specific  gravity,  271  ;  tests  and  manufacture,  272  ; 
distillation  of  wood,  272  ;  utilisation  of  wood-waste,  274  ;  pyroligneous  acid, 
276  ;  calcium  acetate,  277.  Uses,  statistics,  and  price  of  acetic  acid,  279. 
Manufacture  of  vinegar,  280.  Analysis  of  vinegar,  284.  Salts  of  Acetic  Acid  : 
potassium,  sodium,  ammonium,  calcium,  ferrous  and  ferric  acetates,  285 ; 
neutral  and  basic  aluminium  acetates,  silver  acetate,  neutral  and  basic  lead 
acetates,  chromic,  stannous,  and  copper  acetates,  286-287.  Propionic  Acid, 
288.  Butyric  Acids  :  (1)  Normal  butyric  acid,  288  ;  (2)  isobutyric  acid,  288. 
Valeric  Acids  :  (1)  Normal  valeric  acid  ;  (2)  isovaleric  acid  ;  (3)  ethylmetliyl- 
acetic  acid  ;  (4)  trimethylacetic  acid,  288.  Higher  Acids  :  Caproic,  heptylic, 
caprylic,  nonoic,  undecoic,  lauric,  myristic,  289.  Palmitic  Acid,  289.  Margaric 
acid,  293.  Stearic  acid,  290.  Cerotic  acid,  290. 

II.  MONOBASIC  UNSATURATF.D  FATTY  ACIDS  291 

A.  OLEIC  OR  ACRYLIC  SERIES  :  Table,  291.  General  method  of 
formation,  291  :  general  properties,  292.  Acrylic  Acid,  C3H402,  294. 
Crotonic  Acids,  C4H602  :  (a)  vinylacetic  acid  294 ;  (bn)  solid  crotonic  acid, 
295 ;  (bft)  liquid  crotonic  acid,  295 ;  (c)  methylmethyleneacetic  acid,  296. 
Pentenoic  Acids,  C5H8O2 :  (a)  angelic  acid,  296 ;  (b)  tiglic  acid,  296. 
Pyroterebic  Acid,  C6H1002,  297.  -y-Allylbutyric  Acid,  C7H1202,  297. 
Teracrylic  Acid,  C8H1402,  297.  Citronellic  Acid,  C10H18O2 :  rhodinic 
acid,  298.  Undecenoic  Acid,  C11H2002,  298.  Hypogseic  Acid,  C16H30O2, 
298.  Oleic  Acid,  C18H34O2,  298 ;  Elaidic  Acid,  298 ;  Iso-oleic  Acid, 

299  ;   Aa0-oleic   acid,    299.     Erucic  Acid,  C22H4202,  300 ;    Brassidic  Acid, 

300  ;  Isoerucic  Acid,  300. 

B.  UNSATURATED  ACIDS  OF  THE  SERIES  CnH2n_4O2  300 

(a)  Acids  with  a  Triple  Linking  (propiolic  series) :   Table,  300.     Pre- 
paration, 300 ;    properties,    301.     Propiolic    Acid,    C3H202.      Tetrolic 
Acid,  C4H4O2.      Dehydroundecenoic  Acid,  CUH1802,  301.     Undecolic 
Acid,    302.      Stearolic    Acid,    C18H32O2.     Tariric    Acid.      Behenolic 
Acid,  C22H4002,  302. 

(b)  Acids  with  two  Double  Linkings  (diolefine  series),  302.     /3-Vinyl- 
acrylic  Acid,  C6H6O2.      Sorbinic  Acid,   C6H802.     Diallylacetic   Acid, 
C8H1202.     Geranic  Acid,  C18H3202.     Linolic  Acid  ;    Drying  oils,  303. 
a-Elaeostearic  Acid,  304. 

C.  ACIDS  WITH  THREE  DOUBLE  LINKINGS,  CnH2w_602.  Citrylidene- 
acetic  Acid,  C12H18O2.  Linolenic  and  Isolinolenic  Acids,  C18H3002. 
Jecorinic  Acid,  C28H3002,  304. 

ITI.  POLYBASIC  FATTY  ACIDS  304 

A.  SATURATED  DIBASIC  ACIDS,  CMH2w(C02H)2,  304;  Table,  305; 
preparation,  properties,  305.  Oxalic  acid,  C2H204,  306.  Salts  of  oxalic  acid, 
307.  Malonic  Acid,  C3H4O4,  308.  Table  of  malonic  acid  derivatives,  308. 


CONTENTS  xiii 

PACE 

Ethyl  Malonate,  its  use  in  syntheses,  308.  Succinic  Acid,  C4H6O4,  310. 
Homologous  derivatives,  310.  Isosuccinic  Acid,  311.  Pyrotartaric  acids, 
C4H9O4 :  glutaric  acid,  pyrotartaric  acid,  311.  Higher  Homologues,  311. 

ft-Methyladipic  and  azelaic  acids,  311. 

B.  UNSATURATED  DIBASIC  ACIDS,  CwH2n_4O2  312 

OLEFINEDICARBOXYLIC  ACIDS:  Table,  312.  Fumaric  Acid,  313. 
Maleic  Acid,  C4H404.  Itaconic  Acid,  C5H604.  Mesaconic  Acid,  C5H6O4. 
Citraconic  Acid,  C5H604.  Glutaconic  Acid,  C5H6O4.  Pyrocinchonic 
Acid  and  Anhydride,  C6H804.  Korner  and  Menozzi  reaction  of  amino- 
acids.  Hydromuconic  Acid,  C6H8O4.  Diolefinedicarboxylic  Acids. 
Acetylenedicarboxylic  Acids,  313-315. 

C.  TRIBASIC  ACIDS,  &c.  315 
Tricarballylic    Acid,     C3H5(COOH)3.      Camphoronic     Acid,     C9H14O6. 

Aconitic  Acid,  C6H606,  315. 

D.  TETRABASIC  ACIDS  31 G 


FF.  DERIVATIVES  OF  ACIDS 

I.  HALOGEN  DERIVATIVES  310 

(a)  Halogenated  Acids,  316.     Cyano-acids.     Monochloracetic  Acid,  317. 
Table  of  the  halogenated  acids,  318. 

(b)  Acid  Halides :    chloranhydrides ;  acetyl  chloride ;   acetyl  iodide,  &c., 
317-319. 

II.  ANHYDRIDES  319 

Properties,  preparation,  Table,  319-320.     Acetic  Anhydride,  320. 

III.  HYDROXY-ACIDS  320 

A.  SATURATED  DIVALENT  MONOBASIC  ACIDS 

Preparation,  properties,  constitution  ;   lactides  ;   lactones,  321. 

Glycollic  Acid,  OH-CH2-COOH,  and  its  derivatives  (anhydride,  glycollide, 
&c.),  322.  Glycocoll,  322. 

Lactic  Acids,  C2H4(OH)(COOH) :  (1)  i-Ethylidenelactic  acid  (of  fermen- 
tation), 323  ;  Alanine,  325.  (2)  d-Ethylidenelactic  (or  sarcolactic)  acid. 
(3)  1-Ethylidenelactic  acid.  (4)  Ethylenelactic  acid,  325. 

Hydroxybutyric  Acids,  C3H6(OH)(COOH) :  a-Hydroxybutyric  acid. 
a-Hydroxyisobutyric  acid.  /3-Hydroxybutyric  acid,  326. 

Higher  Hydroxy-Acids:  Hydroxy  valeric,  hydroxycaproic,  hydroxy- 
myristic,  hydroxypalmitic,  hydroxystearic,  326. 

B.  UNSATURATED  MONOBASIC  HYDROXY-ACIDS  32(5 
a-,  ft-,  y,  and  8-Hydroxyolefinecarboxylic   acids  :    Ricinoleic   acid  ;    ricino- 
leinsulphonic  acid  and  Turkey-red  oil  (sulphoricinate),  326-328. 

C.  POLYVALENT  MONOBASIC  HYDROXY-ACIDS  328 
Glyceric  Acid,  02H3(OH)2(COOH).     Dihydroxystearic  acid,  C17H33(OH)2- 

COOH,  Erythric  Acid,  C3H4(OH)3-COOH.    Penfonic  acids.     Arabonic  Acid. 
Hexonic  Acids,  328.     Heptonic  Acids,  329. 

D.  MONOBASIC    ALDEHYDIC    ACIDS    (Aldehydic    Alcohols    and 
Dialdehydes)  329 

Glyoxylic  Acid  C02H  -CHO.  Glycuronic,  Forrnylacetic,  and  /3-Hydroxy- 
acrylic  Acids,  329. 


xiv  CONTENTS 

PAGE 

Glycollic  Aldehyde,  OH -CH2-CHO.  Glyceraldehyde.  Aldol.  Glyoxal,  321). 

E.  MONOBASIC   KETONIC    ACIDS    (Keto-alcohols,  Diketones,  and 
Keto-aldehydes)  330 

General  properties.  Methods  of  preparation,  a-,  ft-,  and  y-Ketonic  acids. 
Syntheses  with  ethyl  acetate,  330-331.  Pyruvic  Acid,  331.  Acetoacetic  Acid. 
Ethyl  Acetoacetate,  332.  Levulinic  Acid,  333. 

KETONIC  ALCOHOLS  :  Acetonealcohol.  Dihydroxyacetone. 
Butanolone,  333. 

DIKETONES  :    Diacetyl.     Acetylacetone,  333-334. 

KETO-ALDEHYDES  :  Pyruvic  Aldehyde  and  Acetoacetaldehyde. 
Hydroxymethyleneacetone.  334. 

F.  POLYVALENT     DIBASIC      HYDROXY-ACIDS      AND      THEIR 
DERIVATIVES  334 

Tartronic  Acid,  334.     Malic  Acid  and  higher  homologues,  335. 

TARTARIC  ACIDS:  (1)  d-Tartaric  Acid,  335.  (2)  1-Tartaric  Acid. 
(3)  Racemic  Acid.  (4)  Mesotartaric  Acid,  336. 

TARTAR  INDUSTRY  :  Manufacture  of  Tartar,  337.  Analysis  of 
tartar,  337.  Statistics,  340.  Manufacture  of  tartaric  acid,  341  ;  uses  and 
statistics,  343.  Artificial  tartaric  acid,  343.  Trihydroxyglutaric  Acid, 
343.  Saccharic  and  Mucic  Acids,  344. 

DIBASIC  KETONIC  ACIDS,  344.  Mesoxalic  Acid.  Oxalacetic  Acid. 
Acetonedicarboxylic  Acid.  Dihydroxytartaric  Acid,  344. 

G.  POLYVALENT  TRIBASIC  HYDROXY-ACIDS  345 
Tricarballylic    Acid.      Aconitic    acid.      Citric  Acid    and    its  Industry, 

345.     Tests  for  citric  acid,  346.     Salts  of  citric  acid,  346.     Citrates,  346-347. 
Citrus  industry,  347.     Statistics,  349.     Higher  polybasic  hydroxy-acids,  351. 

IV.  THIO-ACIDS  AND  THIO-ANHYDRIDES  351 

Thioacetic  Acid.  Ethanthiolic  Acid.  Acetyl  Sulphide.  Ethyl  Thioacetate. 

V.  AMIDO-ACIDS,   AMINO-ACIDS,   IMIDES,   AMIDINES,  THIOAMIDES, 

IMINO-ETHERS  AND  ANALOGOUS  COMPOUNDS  351 

A.  Amido-Acids  and  their  Derivatives  :  Primary,  secondary,  and  tertiary 
amides  ;  alkylated  amides.     Preparation  and  properties  of  amides,  351-352. 

Formamide  ;  Acetamide,  diacetamide ;  Oxamic  Acid ;  Oxamide ; 
Succinamic  Acid ;  Succinamide  ;  Glycollamide,  diglycollimide ;  Malamic 
Acid,  malamide,  352-353. 

B.  IMIDES     AND     IMINO-ETHERS:     diacetamide,     iminohydrin    of 
glycollic    acid ;     Oximide,    Succinimide,    pyrrole,    pyrrolidine,    succinanil ; 
Glutarimide,  353-354. 

C.  AMINO-ACIDS   AND   THEIR    DERIVATIVES:    Glycocoll,  sarco- 
sine,    betaine,    aceturic    acid ;  Serine ;   Leucine ;   Aspartic  Acid,  glutamic 
acid  ;   Ethyl  Diazoacetate  ;  Lysine,  ornithine,  putrescine,  taurine,  cysteine, 
cystine  ;   Asparagine,  Aspartamide,  homoaspartic  acid  and  homoasparagine, 
354-356. 

D.  AMIDO-  AND  IMIDO-CHLORIDES  :  acetamido-chloride,  acetimino- 
chloride,  356. 

E.  THIOAMIDES  :  thioacetamide,  367. 


CONTENTS  xv 

PAGE 

F.  IMINOTHIOETHERS  :    acetiminothioinethyl  hydriodide,  357. 

G.  AMIDINES  :    acetamidine,  357. 

H.  HYDRAZIDES   AND   AZIDES  :    diaccthydrazide,  358. 

I.  HYDROXYLAMINE  DERIVATIVES  OF  ACIDS  :  hydroxamic  acids, 
amidoximes,  isuret,  358. 

VI.  CYANOGEN  COMPOUNDS  358 

Cyanogen  :  paracyanogen ;  rubeanhydric  acid  and  flaveanhydric  acid. 
Cyanogen  Chloride,  358-359.  Cyanic  Acid :  potassium  and  ammonium 
cyanates,  359.  Ethyl  Isocyanate,  359.  Cyanuric  Acid  :  Ethyl  cyanurate 
and  isocyanurate,  359.  Fulminic  Acid,  360. 

THIOCYANIC  ACID  AND  ITS  DERIVATIVES,  360.  Potassium, 
Ammonium,  Mercuric,  Silver,  and  Ferric  Thiocyanates,  361.  Ethyl 
Thiocyanate.  Allyl  Thiocyanate,  361. 

MUSTARD  OILS  :   methyl,  ethyl,  propyl,  Allyl,  361. 

CYANAMIDE  AND  ITS  DERIVATIVES,  362.  Calcium  cyanamide,  362. 
Diethylcyanamide.  Dicyanodiamide.  Melams  :  Melamine,  Ammeline, 
Ammelide,  362. 

VII.  DERIVATIVES  OF  CARBONIC  ACID  362 

Esters  of  carbonic  acid.  Ethyl  carbonate,  ethylcarbonic  acid,  363. 
Chlorides  of  Carbonic  Acid.  Chlorocarbonic  acid,  ethyl  chlorocarbonate 
and  chloroformate,  363.  Amides  of  Carbonic  Acid.  Carbaminic  acid, 
urethane,  urea,  semicarbazide,  acetylurea,  allophanic  acid,  ureides,  biuret, 
hydantoic  acid,  hydantoin,  363-364. 

DERIVATIVES  OF  THIOCARBONIC  ACID  :  thiophosgene,  trithio- 
carbonic  acid,  potassium  xanthate,  xanthonic  acid,  dithiocarbamidic  acid, 
diethylthiourea.  Thiourea,  364-365. 

GUANIDINE  AND  ITS  DERIVATIVES  :  nitroguanidine,  aminoguani- 
dine,  diazoguanidine,  hydrazo-  and  azo-dicarbonamide,  glycocyamine,  sar- 
cosihe,  creatine,  creatinine,  365-366. 

URIC  ACID  AND  ITS  DERIVATIVES  :  ureides,  uro-acids,  diureides ; 
parabanic  acid,  barbituric  acid,  dialuric  acid,  alloxan,  oxaluric  acid,  alloxanic 
acid,  cholestrophane,  methyluracil,  alloxanthine,  murexide,  allantoin,  purine, 
dimethylpseudouric  acid,  theophylline,  caffeine,  theobromine,  hypoxanthine, 
xanthine,  adenine,  guanine,  uric  acid,  adenine,  366-369. 

VIII.  ESTERS  (Oils,  Fats,  Waxes,  Candles,  Soaps)  309 
Preparation :    theory  of  the  formation  of  esters  ;    fruit  essences :    ethyl 

formate,  ethyl  acetate,  amyl  acetate,  ethyl  butyrate,  isoamyl  isovalerate,  cetyl 
and  melissyl  palmitates,  ceryl  cerotate,  369-372. 

Glycerides,  Fatty  Oils,  Waxes,  Candles,  Soaps,  372. 

Tripalmitin,  tristearin,  triolein,  lecithin  ;  serum-lipase,  drying  oils,  varnishes  ; 
rancidity  of  oils,  blown  oils,  372-376. 

Waxes :  beeswax,  virgin  wax,  white  wax,  carnauba  wax,  Japanese 
wax,  376-377. 

Saponifi cation  of  Fats  and  Waxes,  377.  Table  of  physical  and  chemical 
constants,  378. 

ANIMAL  OILS  AND  FATS,  379 :  tallow,  380  5  oleomargarine,  382  ; 
margarine,  383;  butter,  385;  milk,  385;  bone  fat,  388;  lard,  388;  fish  oils, 
sperm  oil,  cod-liver  oil,  spermaceti,  389  ;  degras :  wool-fat,  389. 

VEGETABLE  OILS,  390 :  Table,  391 ;  extraction  by  pressure,  hydraulic 
press,  extraction  by  solvents,  refining,  emulsor-centrifuges  and  centrifugal 
separators,  391-395 ;  olive  oil,  395 ;  castor  oil,  398 ;  linseed  oil,  39$ ;  oil 


xvi  CONTENTS 

varnishes  and  lacs,  400  ;  palm  oil,  palm-kernel  oil,  401  ;  coco-nut  oil,  402 ;  vege- 
table tallow,  403  ;  cotton-seed  oil,  403  ;  maize  oil,  403 ;  sesame  oil,  404 ;  arachis, 
soja  bean,  grape-seed  and  tomato-seed  oils,  404-405. 

TREATMENT  OF  FATS  FOR  CANDLES  AND  SOAPS:  (1)  saponi- 
fication  with  lime,  magnesia,  or  zinc  oxide  ;  (2)  decomposition  with  sulphuric 
acid  ;  oleine  of  distillation  ;  transformation  of  oleic  acid  into  solid  fatty  acids  ; 
(3)  saponification  with  water ;  (4)  biological  process ;  (5)  catalytic  process 
(Twitchell),  405-411. 

MANUFACTURE  OF  CANDLES,  412.  De  Schepper  and  Geitcl's 
Table,  413. 

MANUFACTURE  OF  SOAP,  415.  Theory  of  saponification,  416.  Fatty 
acid  or  oleine  soap,  419.  Resin  soap,  420.  Mottled  soap,  421.  Transparent 
soap,  422.  Soft  soap,  422.  Statistics,  424.  Analysis  of  soap,  425. 


GG.   ALDEHYDIC   OR   KETONIC   POLYHYDRIC   ALCOHOLS 

CARBOHYDRATES 

A.  Monoses  426 
Aldohexoses,    ketohexoses,    osazones,    hydrazones ;     general    methods    of 

formation  of  monoses,  426-428.  Tetroses  and  Pentoses  :  pentosans, 
arabinose,  xylose,  rhamnose,  &c.,  429-431.  Hexoses  :  glucose,  caramel ; 
fructose  ;  mannose  ;  galactose,  431-437.  Glucosides,  437. 

B.  Hexabioses  438 
Maltose,  lactose,  438.     Sucrose  :   calcium  sucrate,  440. 

C.  Trioses.    Raffinose  442 

INDUSTRIAL  PREPARATION  OF  SUCROSE  442 

I.  Acer  saccharinum  nigrum,  443.  II.  Sugar-cane,  443.  III.  Sugar  beet, 
445 :  cultivation,  composition,  446 ;  extraction  of  sugar  from  beet,  448 ;  extraction 
by  diffusion,  450  ;  extraction  by  the  Steffen  process,  456  ;  filter-presses,  459  ; 
concentration  of  the  juice,  461  ;  boiling  of  the  concentrated  juice,  466  ;  centri- 
fugation  of  the,  massecuite,  468  ;  refining,  470  ;  revivification  of  animal  charcoal, 
470  ;  utilisation  of  molasses :  osmosis,  lime,  strontia,  baryta  processes,  473. 
Yield,  476.  Statistics,  477.  Fiscal  relations,  477.  Density  table,  482. 
Quantitative  analysis  of  saccharine  materials,  481.  Stammer's  table,  482. 
Polarimeters  and  saccharimeters,  483.  Scheibler's  table,  483.  Chemical  tests, 
486.  Non-sugar,  apparent  and  real  densities,  quotient  of  purity,  487.  Purifi- 
cation of  waste-liquors  from  sugar  factories,  489. 

D.  Tetroses  489 

E.  F.  Higher  polyoses  .  489 

Starch,  489.  Analysis,  500.  Dextrin,  501.  Gums,  502 ;  glycogen,  503. 
Cellulose,  503.  Hydro-  and  oxy- cellulose.  504-506.  Artificial  parchment, 
506.  Paper  industry,  506.  Statistics,  517. 


PART  III.    CYCLIC  COMPOUNDS 

A  A.  ISOCYCLIC  COMPOUNDS  520 

I.  Cydoparajfins  and  cyclo-olefines  or  polymethylene  compounds,  520. 
II.  Benzene  derivatives  or  aromatic  compounds :  the  formula  of  benzene, 
521.  Isomerism  in  benzene  derivatives,  523.  General  character  and  forma- 
tion of  benzene  derivatives,  524-525, 


CONTENTS  xvii 

PAGE 

A.  AROMATIC  HYDROCARBONS  526 

Distillation  of  tar,  526.  Table,  527.  Lampblack,  528.  Tar  oils,  531. 
Preservation  of  wood,  532.  Benzene,  533.  Toluene  and  xylenes,  534. 
Hydrocarbons  with  unsaturated  side-chains,  535. 

B.  HALOGEN  SUBSTITUTION  DERIVATIVES  OF  BENZENE  536 
Table,  537. 

C.  SULPHONIC  ACIDS  538 

Benzenesulphonic  acid,  538.  ' 

D.  PHENOLS  539 

(a)  Monohydric  phenols,  539.  Table,  540.  Carbolic  acid,  541.  Antiseptics, 
541.  Homologues,  543.  (b)  Dihydric  phenols :  pyrocatechol,  resorcinol, 
hydroquinone,  orcinol,  eugenol,  isoeugenol,  543.  (c)  Trihydric  phenols : 
pyrogallol,  hydroxyhydroquinone,  phloroglucinol,  545.  (d)  Polyhydric 
phenols  :  hexahydroxybenzene,  quercitol,  inositol,  546. 

E.  QUINONES  546 

F.  NITRO-DERIVATIVES  OF  AROMATIC  HYDROCARBONS  547 

Table,  548.  Nitrobenzene,  dinitrobenzenes,  nitrotoluenes,  trinitrotoluenes, 
phenylnitromethane,  pseudo-acids,  649-654. 

G.  AMINO-DERIVATLVES  OF  AROMATIC  HYDROCARBONS  554 
Table  of  Aromatic  Amines,  555:    (1)  primary  monamines  ;  (2)  secondary 

monamines  ;  (3)  tertiary  monamines;  (4)  quarternary  bases;  (5)  diamines, 
Iriamines,  tetramines.  Aniline,  nitraniline,  methylaniline,  diphenylamine 
acetanilide,  exalgin,  phenylsulphaminic  acid,  554—560.  Homologues  of  aniline  : 
toluidines,  xylidines,  benzylamine,  phenylenediamine,  560-562. 

H.  NITROPHENOLS,  AMINOPHENOLS,  AND  THIOPHENOLS  562 

Nitrophenol,  picric  acid,  aminophenols,  thiophenols,  562-564. 

I.  AZO-       DIAZO-        AND       DIAZOAMINO-COMPOUNDS      AND 

HYDRAZINES  565 

(1)  Azo- derivatives  ;    (2)  diazo-derivatives  ;    (3)  diazoamino- derivatives 
(4)  hydrazines,  565-570. 

L.  AROMATIC   ALCOHOLS,  ALDEHYDES,  AND  KETONES  570 

Benzyl  alcohol,  benzaldehyde  and  its  homologues,  cinnamaldehyde, 
570-572.  Aromatic  ketones,  572.  Aromatic  oximes,  572.  Beckmann 
rearrangement,  573. 

M.  HYDROXY  -  ALCOHOLS,        HYDROXY  -  ALDEHYDES,      AND 

KETONIC  ALCOHOLS  673 

Salicylaldehyde,  anisaldehydei  vanillin,  573.  Aromatic  hydroxy-alde- 
hydes,  674. 

N.  AROMATIC  ACIDS  57  £ 

General  methods  of  preparation  and  properties,  575. 

(a)  MONOBASIC  AROMATIC  ACIDS,  576.  Table,  677.  Benzole 
anhydride,  benzoyl  chloride,  benzamide,  hippuric  acid,  chlorobenzoic  acid, 
m-nitrobenzoic  acid,  azobenzoic  acids,  aminobenzoic  acids  (anthranilic 
acid),  diazobenzoic  acids,  anthranil,  sulphobenzoic  acids,  saccharin, 
toluic  acids,  phenylacetic  acid,  xylic  acids,  cuminic  acid,  cinnamic  acid, 
phenylpropiolic  acid,  578-580. 
II  b 


xviii  CONTENTS 

PAGE 

(6)  DIBASIC  AND  POLYBASIC  AROMATIC  ACIDS,  580 .  phthalic 
acid,  phthalic  anhydride,  phthalide,  phthalophenone,  phenolphthalein, 
fluorescein,  eosin,  phthalimide,  isophthalic  acid,  terephthalic  acid ; 
polybasic  acids  :  mellitic  acid,  580-581. 

(c)  HYDROXY- ACIDS  OR  PHENOLIC  ACIDS,  582;  salicylic 
acid,  m-  and  p-hydroxybenzoic  acids,  gallic  acid,  ink,  cumaric  and 
mandelic  acids.  Tannin,  tanning  of  skins,  commercial  data,  582-591. 

0.  HYDROGENATED  BENZENE  COMPOUNDS  591 

Hydrophthalic  acids.  Terpenes,  cymene,  carvene,  1-limonene,  sylvestrene, 
terpinolene,  terpinene,  dihydrocymene,  phellandrene,  menthene,  menthane, 
591-596.  Complex  Terpenes,  pinene,  oil  of  turpentine,  colophony,  camphene, 
fenchene,  camphane ;  rubber,  ebonite,  guttapercha,  ionone,  596-600 ;  camphors, 
terpane,  menthol,  pulegone,  carvone,  terpenol,  terpineol,  terpin,  cineol ; 
camphor,  artificial  camphor,  600-605. 

P.  CONDENSED  BENZENE  NUCLEI  605 

(1)  Diphenyl  and  its  derivatives  :  diphenyl,  benzidine,  carbazole,  di- 
hydroxyphenyl,  &c.,  605.  (2)  Diphenylmethane  and  its  derivatives  :  dihy- 
droxybenzophenone,  diphenylethano,  tolylphenylmethane,  benzoylsulphonic 
acids,  fluorene,  606.  (3)  Triphenylmethane  and  its  derivatives  :  leuco-bases, 
malachite  green,  pararosaniline,  rosaniline,  fuchsine,  methyl  violet ;  rosolic 
acid,  phthalophenone,  hexaphenyle thane,  and  pentaphenylethane,  607. 
(4)  Dibenzyl  and  its  derivatives,  609.  (5)  Naphthalene  and  its  derivatives : 
naphthalene,  hydronaphthalene,  perinaphthalenecarboxylic  acid,  a-nitro- 
naphthalene,  a-naphthylamine,  naphthalenesulphonic  acids,  o-  and  /3- 
naphthols,  dinaphthol,  betol  :  naphthionic  acid,  a-  and  /3-naphthaquinones, 
naphthalic  acid,  dinaphthyl,  acenaphthene,  610-614.  Addition  products  of 
naphthalene.  Indene,  614.  (6)  Anthracene  group :  anthracene,  carbazole, 
anthraquinone,  alizarin,  614-618.  Phenanthrene,  phenanthraquinone,  fluor- 
anthrene,  pyrene,  chrysene,  picene,  retene,  618-619. 

Q.  HETEROCYCLIC  COMPOUNDS  <Hfl 

(1)  Furfuran  :  furfural,  furfuryl  alcohol,  pyromucic  acid,  619.  (2)  Thio- 
phene,  620  ;  thioxene,  indophenin.  (3)  Pyrrole  :  iodol,  pyrocoll,  nitrosopyrroles, 
hydropyrroles ;  pyrazole,  pyrazolone,  antipyrine,  620-623.  (4)  Pyridine 
ani  its  derivatives  (alkaloids)  :  pyridine,  picoline,  lutidine,  collidine,  pyridones, 
pyridinecarboxylic  acids,  hydropyridines,  piperidine,  623-626.  Alkaloids  : 
Separation  and  tests,  627  ;  Table,  628 ;  synthesis  of  alkaloids  and  medicine ; 
anaesthetics ;  coniine,  nicotine  (tobacco),  atropine.  morphine,  cocaine,  narco- 
tine,  strychnine,  brucine,  curarine  quinine,  627-635.  (5)  Quinoline  and 
its  derivatives  :  quinaldine  ;  isoquinoline.  I  satin.  Indoxyl.  Skatole.  Indole. 
Indazole,  635-639.  Indigo,  natural  and  artificial ;  analysis ;  various  syntheses ; 
statistics,  639-646. 

R.  COLOURING-MATTERS  (Xfi 

Dichroic  substances ;  chromophores,  chromogens,  auxochromes.  Rosani 
line.  Process  of  dyeing.  Basic,  acid,  and  neutral  colouring- matters.  Lakes. 
Mordants,  646-651.  Behaviour  of  colouring- matters  with  respect  to  various 
fibres  and  mordants,  according  to  Noelting,  651.  Manufacture  of  colouring- 
matters,  652.  Statistics  of  production,  653.  Classification  of  colouring-matters : 
I.  Nitro-  colouring- matters.  II.  Azo-  colouring- matters.  III.  Derivatives 
of  hydrazones  and  pyrazolones.  IV.  Hydroxyquinones  and  quinoneoximes. 
V.  Diphenyl-  and  triphenyl- methane  colouring- matters.  *  VI.  Derivatives  ot 
quinonimide.  VII.  Aniline  black.  VIII.  Quinoline  and  acridine  derivatives. 
IX.  Thiazole  colouring- matters.  X.  Oxyketones,  xanthones,  flavones,  and 
coumarins.  XI.  Indigo  and  similar  and  other  natural  colouring-matters  : 
indanthrene  group  ;  logwood  ;  archil ;  cochineal  ;  yellow  wood  (Cuba  wood)  ; 
quercitron;  natural  Indian  yellow ;  redwood  (Brazil  wood);  sandal  wood 
catechu;  gambier;  chlorophyll.  XII.  Sulphur  colouring-  matters,  654— 671. 


CONTENTS  xix 

P.UiE 

TESTING  OF  COLOURING-MATTERS  671 

Examination  of  mixtures  of  colouring-matters,  671-680. 
Recognition  of  the  principal  colouring. matters  on  dyed    fibres  (Table), 
674-679. 

TEXTILE  FIBRES  «8I 

Wool :  different  breeds  of  sheep ;  combed  and  carded  wool ;  shoddy ; 
statistics  ;  count  of  yarn  ;  imports  and  exports  ;  chemical  properties  of  wool, 
681-684.  Cotton:  mercerised  cotton;  statistics,  684-686.  Flax,  686. 
Hemp,  688.  Jute,  689.  Silk :  rearing  of  the  silkworm ;  treatment  of 
cocoons  ;  spinning  and  twisting  ;  silk  waste  ;  cleansing  and  dyeing  ;  deter- 
mination of  the  weighting  of  silk  ;  statistics  of  silk  and  cocoons,  690-698. 
Sea  silk,  698.  Artificial  silk  :  history  ;  dyeing  ;  output,  698-703. 

QUALITATIVE  TESTS  FOR  DIFFERENT  TEXTILE  FIBRES  703 

QUANTITATIVE  ANALYSIS  OF  MIXTURES  OF  TEXTILE 
FIBRES:  conditioning;  moisture;  dressing;  mixed  cotton  and  wool ;  cotton 
and  silk ;  natural  and  artificial  silk  ;  cotton  and  linen,  704-705. 

DYEING  AND  PRINTING  TESTS  ON  TEXTILE  FIBRES  705 

FASTNESS  TESTS  707 

THEORY  OF  DYEING  708 

MACHINERY  USED  IN  DYEING  AND  FINISHING  TEXTILE 
FIBRES,  711.  Washing  and  preparation;  bleaching;  milling;  carbonisation  ; 
fixing  of  fabrics  ;  crabbing  ;  dyeing  plant ;  jiggers  ;  dryers  ;  tentering 
frames  ;  raising  gigs  ;  calendars  ;  cutters  ;  steaming  ;  dressing  ;  finishing  ; 
pressing  ;  mercerisation  ;  printing  of  fabrics  and  yarns  ;  oxidation  chamber 
for  aniline  black;  polishing  of  silk,  711-713. 

S.  PROTEINS  OR  ALBUMINOIDS  733 

Characteristic  reactions  of  the  proteins ;  hydrolysis  and  synthesis ; 
polypeptides,  733-735.  I.  Natural  Proteins  :  (1)  Albumins  (egg-  and 
blood-),  egg-industry.  (2)  Globulins.  (3)  Nucleo-albumins.  (4)  Proteins 
which  coagulate.  (5)  Histones.  (6)  Protamines,  735-737.  II.  Modified 
Proteins  :  (1)  Albumoses  and  peptones.  (2)  Salts  of  proteins,  737. 
III.  Conjugated  Proteins  (Proteids) :  (1)  Haemoglobin.  (2)  Nucleo- 
proteins.  (3)  Glucoproteins,  737-739.  IV.  Albuminoids:  (1)  Elastin. 
(2)  Keratin.  (3)  Collagens.  Manufacture  of  glue  and  gelatine,  739. 
V.  Various  Proteins,  740. 

GLUCOSIDES  AND  OTHER  SUBSTANCES  OF  UNCERTAIN  OR 
UNKNOWN  COMPOSITION  :  Amygdalin  ;  saponin  ;  digitalin  ;  salicin  ; 
aesculin  ;  populin  ;  hesperidin  ;  phloretin ;  iridin  ;  arbutin  ;  coniferin  ; 
sinigrin  ;  santonin ;  aloin ;  lecithin ;  cerebrin ;  iodothyrin ;  taurocholic, 
glycocholic,  and  cholic  acids ;  biliverdin,  bilif uchsin,  and  bilirubin ;  cantharidin ; 
chitin ;  cholesterol,  740-742. 

INDEX  743 


ERRATUM 

Page  386,  line  28,  for  gallatite  read  gallalith 


PART  I.   GENERAL 

IN  vol.  i  of  this  treatise l  is  given  a  brief  summary  of  the  history  of  chemistry 
and  of  those  portions  of  physico-chemical  theory  which  are  necessary  for  the 
interpretation  of  chemical  phenomena. 

Hence,  this  course  of  organic  chemistry  assumes  in  the  reader  a  knowledge 
of  the  fundamental  chemical  laws  and  ideas,  methods  of  determining  molecular 
weights,  and  so  on. 

The  separate  treatment  of  the  carbon  compounds,  which  is  termed  organic 
chemistry,  is  a  purely  didactic  convenience  and  somewhat  of  a  habit,  there 
being  no  sound  foundation  to  justify  a  distinction  between  organic  and  inorganic 
chemistry. 

This  division  of  the  subject  dates  back  to  the  time  of  Lemery,  who,  in 
1675,  regarded  the  substances  of  the  animal  and  vegetable  kingdoms  as  distinct 
from  those  of  the  mineral  kingdom,  and  to  1820,  when  Berzelius  justified  the 
separation  by  stating  that  the  preparation  of  organic  compounds  required  the 
intervention  of  vital  force,  whilst  inorganic  compounds  could  be  prepared 
artificially  in  the  laboratory.  But  this  view  was  abandoned  in  1828,  when 
Wohler  succeeded  in  preparing  urea  (found  in  urine)  from  inorganic  material 
in  the  laboratory,  and,  later,  when  acetic  acid  was  prepared  artificially.  Sub- 
sequently, the  number  of  so-called  organic  compounds  which  have  been 
obtained  synthetically  has  increased  almost  without  limit. 

There  exists  to-day  no  reason  for  a  distinction  between  organic  and  inorganic 
compounds  ;  the  first  comprise  a  group  of  carbon  compounds  ^  embracing  an 
immense  number  (over  150,000)  of  substances,  which  exhibit  certain  common 
characters  and  are  conveniently  studied  by  themselves. 

It  had  already  been  recognised  by  Lavoisier  that  all  so-called  organic 
compounds,  originating  in  organised  bodies,  contain  carbon,  hydrogen,  and 
oxygen,  and  that  many  of  them,  especially  those  of  the  animal  kingdom, 
contain  also  nitrogen  and  sometimes  sulphur,  phosphorus,  halogens,  and 
metals. 

The  study  of  organic  compounds  is  as  old  as  the  human  race,  which,  from 
the  most  remote  times,  has  prepared  alcohol  and  acetic  acid  from  vegetable 
juices  (the  must  of  the  grape  and  other  fruit,  &c.). 

After  the  discoveries  of  Lavoisier  and  the  investigations  of  Berzelius, 
organic  chemistry  began  to  acquire  a  special  importance.  And  Liebig,  by 
introducing  simple  and  exact  methods  for  the  analysis  of  organic  compounds, 
rendered  most  valuable  help  to  the  wonderful  theoretical  and  practical 
development  which  has  been  shown  by  this  branch  of  chemistry  during  the 
past  fifty  years,  and  which  has  been  largely  responsible  for  the  impulse  given 
to  progress  and  civilisation  in  the  nineteenth  century. 

In  order  to  study  the  innumerable  derivatives  of  carbon,  to  be  able  to  obtain 
separate  individuals  and  to  characterise  them  by  means  of  their  chemical  and 
physical  properties,  then  to  group  and  classify  them  and  to  deduce  in  a  more 
or  less  general  way  the  laws  they  obey,  it  was  necessary  to  isolate  and  prepare 
in  the  pure  state  these  separate  chemical  individuals. 

1  E.  Molinari,  "Inorganic  Chemistry";  Translated  by  E.  Feilmann,  1912. 


2  ANIC    CHEMISTRY 


OF  ORGANIC  SUBSTANCES 

The  purification  of  organic  substances  is  not  so  easy  to  effect  as  might  appear  at  first 
sight.  Pure  substances  are  characterised  by  certain  physical  constants  (boiling-point, 
melting-point,  crystalline  form,  &c.),  which  serve  to  show  if  a  substance  is  in  a  suitable 
condition  for  chemical  analysis. 

The  chemical  processes  of  purification  may  be  deduced  from  the  chemical  properties 
of  the  substances  themselves,  as  described  in  Parts  II  and  III  of  this  treatise  ;  general 
physical  methods  effect  purification  by  means  of  suitable  solvents  (water,  alcohol,  ether, 
light  petroleum,  acetic  acid,  benzene,  acetone,  chloroform,  carbon  disulphide,  &c.),  which 
separate  certain  substances  from  others  more  or  less  soluble  ;  or,  in  many  cases,  purifica- 
tion is  brought  about  by  crystallisation,  a  solution  of  the  impure  substance  in  a  suitable 
hot  solvent  depositing  —  on  gradual  cooling  or  partial  evaporation  of  the  solvent  —  the 
pure  substance  in  characteristic  and  well-defined  crystalline  forms,  which  can  be  controlled 
by  measuring  the  angles  and  determining  the  axial  ratios  of  the  crystals. 

Impurities  separate  sometimes  before  and  sometimes  after  the 
crystallisation  of  the  substance  under  examination,  so  that  recourse 
is  had  to  fractional  crystallisation,  which,  when  repeated,  may  give 
excellent  results. 

In  certain  cases,  substances  are  purified  by  sublimation.1  When 
pure,  a  liquid  has  a  constant  boiling-point  for  a  definite  pressure 
(vol.  i.  p.  81),  and  this  is  determined  by  distilling  the  liquid  in  a 
flask  with  a  lateral  tube,  a  thermometer  being  arranged  in  the  neck 
of  the  flask  without  its  bulb  dipping  into  the  boiling  liquid.  The 
temperature  of  the  vapour  gives  the  boiling-point  of  the  liquid  ;  the 
vapour  escapes  from  the  side  -tube  and  is  condensed  by  means  of  a 
Liebig's  condenser,  formed  of  an  inclined  glass  tube  surrounded  by 
a  wider  tube  through  which  water  circulates  from  the  lower  to  the 
upper  end  (Fig.  2^- 

The  boiling-point  of  a  very  small  quantity  of  substance  can  be  accurately  determined 
by  means  of  the  arrangement  shown  in  Fig.  3  :  a  few  drops  of  the  liquid  are  introduced 
into  a  small  tube,  d,  closed  at  the  bottom  and  drawn  out  into  a  narrowed  part.  Into  the 
liquid^dips  a  capillary  tube,  sealed  at  the  point  a  by  fusing  the  glass.  The  tube  is  attached 
to  the  thermometer,  c,  and  the  whole  immersed,  to  the  depth  of  a  few  centimetres,  in  a 
liquid  having  a  boiling-point  higher  than  that  of  the  liquid  under  examination.  Heat 
is  now  gradually  applied,  superheating  being  prevented  by  the  air-bubbles  issuing  from 
the  lower  end  of  the  capillary  tube.  When  the  boiling-point  is  reached,  bubbles  form 
very  rapidly  at  the  bottom  of  .the  liquid,  and  the  boiling-point  is  read  off  on  the 
thermometer. 

Certain  substances  which  readily  decompose  on  boiling  at  the  ordinary  pressure  can 
be  distilled  unchanged  at  a  constant,  but  somewhat  lower,  temperature  by  lowering  the 
pressure,  i.e.  by  distilling  in  a  vacuum  (see  later).  For  this  purpose  use  is  made  of  a 
mercury  or  water  pump  (Sprengel). 

When  two  liquids  are  mixed,  they  can  be  separated  almost  completely  by  fractional 
distillation,  if  there  is  a  wide  interval  of  temperature  between  their  boiling-points.  In 
consequence  of  the  partial  pressure  of  the  components,  at  different  temperatures  mix- 
tures distil  over  which  contain  varying  proportions  of  these  components  ;  the  liquid  with 
the  lower  boiling-point  first  preponderates  in  the  distillate,  while  at  higher  temperatures 
that  with  the  higher  boiling-point  preponderates.  On  repeated  redistillation  of  the  two 
extreme  fractions  separately,  the  two  liquids  can  be  obtained  in  the  pure  state.  In  certain 
cases,  however,  a  mixture  of  two  liquids  does  not  exhibit  a  regular  progression  in  the 
vapour  pressure  corresponding  with  the  preponderance  of  one  or  other  of  the  two 
components.  There  are,  indeed,  liquids  which,  when  mixed  in  certain  proportions,  show 
a  minimum  vapour  pressure  —  lower  even  than  that  of  the  less  volatile  component  —  whilst, 

1  Sublimation  takes  place  with  many  solid  substances  and  consists  in  the  passage  from  solid  to  vapour  on  gentle 
heating,  and  from  the  state  of  vapour  to  the  solid  crystalline  condition  wtjen  the  vapours  come  into  contact  with 
a  cold  body  :  these  changes  taking  place  directly  and  not  by  way  of  the  liquid  state.  Usually  the  substance  is 
placed  on  a  clock-glass,  covered  by  a  perforated  filter-paper  and  by  a  funnel  ;  on  heating  the  clock-glass  on  a  sand- 
bath,  the  pure  sublimed  crystals  collect  on  the  walls  of  the  funnel  (Pig.  1).  In  some  cases,  the  sublimation  is  carried 
out  in  a  vacuum. 


RECTIFICAT ION 


3 


on  the  other  hand,  a  mixture  of  two  liquids  sometimes  has  a  vapour  pressure  greater  than 
that  of  its  more  volatile  constituent  ;  the  two  liquids  cannot  then  be  separated  by  fractional 
distillation,  especially  when  their  boiling-points  are  not  far  apart.1  In  these  cases  good 
results  are  obtained  practically  by  employing  so-called  rectification,  this  consisting  in 
distilling  the  liquid  mixture  through  a  Le  Bel  and  Henninger  (1874)  rectifying  tube 


Tic 


FIG.  2. 


FIG.  3. 


(Fig.  4),  which  is  fitted  at  regular  intervals|  with  discs  of 
platinum  gauze,  and  above  these  takes  the  form  of  a  series 
of  two  or  more  bulbs,  a  lateral  tube  being  so  placed  as  to 
lead  the  liquid  condensing  in  any  bulb  back  to  the  bulb 
below  it.  When  the  liquid  boils,  the  mixed  vapours  pass 
up  the  tube  and  meet  the  first  gauze  disc,  where  the  vapour 
of  the  less  volatile  liquid  is  condensed^in  greater^  proportion 
than  the  other,  so  that  the  vapour  reaching^  the  second 
gauze  is  richer  in  that  of  the  more  volatile  liquid ;  a  similar 
process  occurs  at  the  successive  gauzes  and  in  the  bulbs 
above  them,  so  that  the  vapour  passing  through  the  upper- 
most bulb  is  that  of  the  more  volatile  liquid,  and  this  passes 
down  the  side-tube  (at  the  mouth  of  which  the  thermo- 
meter is  placed)  to  the  condenser.  During  this  rectification 
the  cooling  produced  by  the  outer  air  and  the  consequent 
condensation  of  the  vapours  result,  in  the  rectifying  tube, 
in  a  stream  of  liquid  flowing  down  the  walls  of  the  tube  ; 
this  liquid  meets  the  ascending  vapours  and  gives  up  to 
them  its  more  volatile  constituent  and  takes  up  from  them 
their  less  volatile  component,  so  that  only  the  vapour  of 
the  more  volatile  liquid  reaches  the  top  of  the  tube,  while 
the  less  volatile  liquid  is  returned. 

Similar  results  are  obtained  by  Hempel's  rectifying  column  (1881),  which  is  filled  with 
glass  beads  (Fig.  5).  With  this  also  the  phenomenon  of  rectification  which  goes  on  often 

1  Theory  of  Fractional  Distillation.  We  shall  see  later  the  relations  existing  between  the  boiling-point  and  the 
composition  and  chemical  constitution  of  organic  substances  (homologous  series,  isomerides,  &c.).  Of  interest 
at  the  present  juncture  is  the  behaviour  on  distillation  of  a  mixture  of  two  liquids  which  dissolve  one  in  the  other 
in  all  proportions. 

According  to  Wanklyn  and  Berthelot,  when  a  mixture  of  equal  weights  of  two  liquids  is  distilled,  the  propor- 
tions of  the  two  in  the  distillate  depend  not  only  on  their  proportions  in  the  original  liquid  and  on  their  vapour 
pressures  at  the  boiling-point  of  the  mixture  itself,  but  also  on  the  reciprocal  adbesion  of  the  constituent  liquids 


FIG.  4. 


FIG.  5. 


4T-  '.  -  ORGANIC    CHEMISTRY 

permits  of  the  separation  of  liquids  with  boiling-points  quite  close  together.  This 
phenomenon  has  important  applications  in  the  alcohol  industry  (see  later),  in  the  manu- 
facture of  oxygen  and  nitrogen  from  liquid  air,  in  the  preparation  of  liquid  sulphur  dioxide 
(vol.  i,  pp.  245  and  295),  and  in  many  other  industries. 


FIG.  6. 

In  many  cases  substances  (liquid  or  solid)  are  purified  by  distilling  in  a  current  of 
steam,  certain  of  them  being  volatile  under  these  conditions  even  when  their  boiling- 
points  are  above  that  of  water  ;  in  the  distillate  the  substance  often  separates  owing  to 
its  insolubility  in  water.  An  arrangement  used  in  the  laboratory  is  shown  in  Fig.  6, 
steam  being  generated  in  A  and  passing  through  the  substance  to  be  distilled  in  the 
flask,  B,  which  can  be  heated  directly  with  a  flame. 

In  some  instances  the  distillation  is 
effected  by  means  of  superheated  steam  (150°- 
350°),  which  is  obtained  by  passing  steam 
through  a  coil  of  iron  or  copper  tubing 
heated  with  a  bunsen  burner  (Fig.  7). 

A  number  of  substances  decompose  when      .  . 
heated  at  the  ordinary  pressure,  whilst  they 


FIG.  7. 


FIG.  8. 


distil  unchanged  hi  a  more  or  less  perfect  vacuum,  owing  to  a  marked  lowering  of  the 
boiling-point.  Of  the  many  different  forms  of  apparatus  employed  in  the  laboratory  for 

and  on  their  vapour  densities.  When  a  mixture  of  two  miscible  liquids,  in  equal  weights,  is  distilled,  the  quantity 
of  each  component  which  distils  can  (disregarding  certain  exceptions)  be  calculated  by  multiplying  the  vapour 
pressure  (at  the  boiling-point  of  the  mixture)  by  the  vapour  density.  Hence  it  can  be  understood  how,  in  some 
cases,  the  less  volatile  substance  distils  in  greater  quantity.  Even  if  the  vapours  that  distil  over  contain  equal 
volumes  of  the  two  vapours  (that  is,  equal  numbers  of  molecules),  the  condensed  liquid  will  contain  a  greater 
proportion  by  weight  of  the  constituent  with  the  higher  molecular  weight.  This  explains  why  water,  with  a  low 
vapour  density,  causes  substances  with  higher  boiling-points  (ethereal  oils,  naphthalene,  &c.)  to  distil,  since, 
although  the  latter  have  low  vapour  pressures,  their  molecular  weights  are  high. 

On  distilling  a  mixture  of  two  liquids  not  soluble  one  in  the  other,  the  corresponding  vapours  do  not  influence 


MELTING-POINTS 


this  purpose,  that  of  Bredt  is  illustrated  in  Fig.  8.  An  ordinary  thick-walled  distilling 
flask,  A,  is  used,  its  side-tube  being  connected  with  the  condenser  a  and  with  the  collecting 
apparatus,  which  consists  of  a  flask,  d,  and  three  tubes,  e,  of  thick  glass,  and  is  joined  to 
the  condenser  by  means  of  a  perforated  stopper  ;  the  pump  by  which  the  air  is  withdrawn 
from  the  whole  apparatus  is  connected  with  the  tube,  c,  which  communicates  also  with 
a  manometer  to  show  the  extent  of  the  vacuum  attained.  Superheating  and  consequent 
bumping  of  the  liquid  are  avoided  by  the  insertion  of  the  tube  b,  the  lower  end  of  which 
is  drawn  out  to  a  capillary  and  dips  below  the  surface  of  the  liquid,  while  the  upper  end 
is  closed  with  a  piece  of  rubber  tubing  fitted  with  a  screw-clip  ;  by  means  of  this  tube,  into 
which  also  the  thermometer  may  be  introduced,  a  slow  current  of  air  or  other  inert  gas, 
controlled  by  means  of  the  screw-clip,  is  allowed  to  bubble  through  the  liquid.  The 
flask  is  heated  in  a  bath  of  oil  or  fusible  alloy,  and,  if  the  distillate  is  very  dense,  no  water 
need  be  passed  through  the  condenser.  The  first  portion  distilling  over  at  a  definite 
temperature  is  collected  in  d,  and  when  the  temperature  rises  suddenly,  the  collecting 
apparatus  is  rotated  so  that  the  distillate  is  collected  in  one  of  the  tubes,  e  ;  when  the 
thermometer  no  longer  indicates 
a  constant  temperature,  another 
of  the  tubes,  e,  is  employed,  and 
so  on. 

MELTING-POINTS.  Whilst 
with  liquids  the  boiling-point  is 
generally  used  as  a  criterion  of 
purity,  for  solids  the  melting-point 
is  mostly  employed  for  this  pur- 
pose, and  in  certain  cases  also 
the  boiling-point.  So  long  as  the 
substance  is  impure,  the  melting- 
point  is  usually  too  low.  The 
melting-point  is  determined  by 
introducing  a  few  centigrams  of 
the  substance  into  a  very  narrow, 
almost  capillary  glass  tube  closed 
at  the  bottom  (Fig.  9),  the  tube 
being  attached  to  the  bulb  of  a 
thermometer  dipping  into  a  beaker 
of  concentrated  sulphuric  acid, 
oil,  or  paraffin,  which  serves  to 
transmit  heat  to  the  substance.  A  small  glass  stirrer  serves  to  prevent  superheating  of 
the  liquid,  and,  when  the  substance  is  pure,  it  melts  entirely  within  a  degree  and  generally 
becomes  transparent.  When  the  temperature  of  the  bath  approaches  the  melting-point 
the  flame  is  lowered  and  the  bath  heated  gently  so  that  the  temperature  rises  half  a 
degree  every  four  or  five  seconds  ;  only  in  exceptional  cases  should  rapid  heating  be 
continued. 

To  determine  the  melting-point  of  a  fat,  a  tube  drawn  out  to  a  capillary  and  sealed 
at  the  lower  end  (Fig.  10a)  is  held  in  an  inclined  position,  and  one  or  two  drops  of  the  fused 
and  filtered  fat  introduced  into  the  enlarged  part  (A,  Fig.  10a).  When  the  fat  is  solidified, 
the  tube  is  kept  in  a  cool  place  for  twenty -four  hours,  after  which  it  is  attached  vertically 
to  the  bulb  of  a  thermometer  ;  it  is  then  heated  in  a  suitable  bath,  note  being  taken  of 
the  temperature  at  which  (1)  fusion  begins,  (2)  the  fat  flows  down  and  obstructs  the 
capillary  (Fig.  106),  and  (3)  the  completion  of  fusion  is  indicated  by  the  entire  liquefaction 
and  transparency  of  the  fat. 

one  another,  and  the  total  pressure  of  the  vapours  is  given  by  the  sum  of  the  pressures  of  the  two  liquids  at  the 
temperature  of  distillation.  The  boiling-point  of  the  mixture  is  the  temperature  at  which  the  sum  of  the  vapour 
pressures  of  the  components  equals  the  atmospheric  pressure  ;  it  should  be  mentioned  that  the  boiling-point  of 
such  a  mixture  is  necessarily  lower  than  that  of  the  more  volatile  liquid,  since  here  also  Dalian's  law  of  partial 
pressures  (vol.  i,  pp.  71,  38.3,  491)  holds.  Naumann  (1877)  showed  that,  in  the  vapour  distilling  from  such  a  mixture 
the  ratio  between  the  volumes  of  the  components  corresponds  with  the  ratio  between  the  vapour  pressures  of  the 
two  liquids  at  the  boiling-point  of  the  mixture ;  and  hence  the  weights  of  the  two  components  are  obtained  by 
multiplying  these  ratios  by  the  corresponding  densities  (or  molecular  weights).  By  means  of  this  rule,  Naumann 
succeeded  in  determining  the  molecular  weights  of  various  substances  simply  by  distilling  mixtures  of  them.  A 
mixture  of  water  and  isoamyl  alcohol  (b.pt.  135°)  has  a  constant  boiling-point  of  96°,  and  distils  continuously 
in  the  ratio  of  two  volumes  of  water  and  three  volumes  of  the  alcohol. 


6 


ORGANIC    CHEMISTRY 


The  melting-point  of  a  fat  can  also  be  determined  by  drawing  it  in  the  fused  condition 
into  a  capillary  tube  blown  out  at  the  middle  into  a  bulb,  which  is  half  filled  with  the  fat 
(Fig.  11)  ;  the  upper  end  of  the  tube  is  kept  closed  with  the  finger  until  the  fat  becomes 
solid,  the  empty  part  of  the  tube  being  then  bent  round  as  shown  and  attached,  upside 
down,  to  a  thermometer,  the  whole  being  afterwards  gradually  heated  in  a  beaker  of  water. 
When  the  fat  begins  to  melt  it  flows  into  the  lower  part  of  the  bulb  (Fig.  11  A  b,  right-hand 
view),  and  when  it  is  completely  fused  it  becomes  transparent. 

For  fats  and  paraffins,  or  waxes  in  general,  and  for  soft  fats  (for  example,  lubricants) 
especially,  an  important  determination  is  that  of  the  dropping -point,  which  is  carried  out, 

according  to  Ubbelohde's  method  (1905),  by 
filling  with  the  fat  a  glass  capsule,  e  (Fig.  12, 
natural  size),  10  mm.  long  and  7  mm.  wide, 
with  an  orifice  3  mm.  in  diameter  in  the  base  ; 
a  very  small  thermometer  bulb  is  immersed  in 
the  fat  and  the  capsule  then  affixed  to  the 
thermometer  with  a  metal  sheath  having  an 
aperature  at  c,  and  three  points,  d,  which 
determine  the  position  of  the  capsule  ;  the 
thermometer  is  then  fixed  in  a  test-tube 
4  cm.  in  diameter,  dipping  into  a  beaker  of 
water,  which  is  heated  so  that  the  temperature 
rises  one  degree  per  minute.  At  the  orifice  of 
the  capsule  a  drop  begins  to  form  at  a  certain 
time,  and  when  this  falls  the  temperature  is 
read,  and  is  usually  corrected  by  subtracting 
0-5  to  obtain  the  real  instead  of  the  apparent 
dropping-point. 

This  method  has  been  adopted  for  the 
examination  of  lubricating  oils  supplied  to  the 
Italian  navy  and  railways. 

The  specific  gravity  of  liquids  also  serves  to  determine  their  purity,  and  the  various 
forms  of  apparatus  used  for  measuring  it  are  described  in  vol.  i,  p.  72. 


FIG.  11. 


FIG.  12. 


ANALYSIS  OF  ORGANIC  SUBSTANCES 

As  will  be  seen  later,  many  so-called  organic  substances  are  composed 
of  carbon  and  hydrogen  combined  in  various  proportions  ;  a  large  number  of 
them  also  contain  oxygen,  while  nitrogen  is  often  present  and  sometimes 
sulphur,  halogens,  metalloids,  and  metals. 

Analysis  of  these  compounds  may  be  merely  qualitative,  when  only  a 
knowledge  of  the  constituent  elements  is  required,  or  it  may  be  quantitative 
when  the  percentage  amount  of  each  of  the  elements  present  is  determined. 

QUALITATIVE  COMPOSITION.  When  organic  substances  are  heated  on  platinum 
foil  they  either  burn  with  a  flame  or  leave  a  carbonaceous  residue.  The  presence  of 
carbon  and  hydrogen  may  be  demonstrated  by  heating  a  little  of  the  substance,  mixed 
with  cupric  oxide,  in  a  test-tube  fitted  with  a  delivery  tube,  the  gas  evolved  being  passed 
into  a  clear  solution  of  barium  hydroxide :  if  the  latter  becomes  turbid,  owing  to  the 
formation  of  barium  carbonate,  the  presence  of  carbon  is  proved,  and  if  drops  of  water 
condense  in  the  cold  upper  part  of  the  tube  the  substance  must  contain  hydrogen. 

The  presence  of  nitrogen  can,  in  many  cases,  be  shown  by  the  smell  of  burning  wool 
or  nails  developed  when  a  little  of  the  substance  is  heated  on  platinum  foil.  A  more 
general  and  certain  test  is  that  devised  by  Lassaigne  (1843) :  2-3  centigrams  of  the  sub- 
stance are  fused  with  a  piece  of  metallic  potassium  or  sodium  (0-2-0-3  grm.)  in  a  test-tube, 
which  is  broken  by  plunging  it  while  still  hot  into  a  beaker  containing  10-12  c.c.  of  water. 
The  alkaline  solution  of  potassium  cyanide  formed  is  filfered,  mixed  with  a  few  drops  of 
ferrous  sulphate  and  ferric  chloride  solutions  and  boiled  for  two  minutes,  by  which  means 
potassium  ferrous  cyanide  is  formed  (when  nitrogen  is  present  in  the  substance)  ;  the 
liquid  is  acidified  with  hydrochloric  acid,  which  dissolves  the  ferrous  and  ferric  oxides, 


ELEMENTARY  ORGANIC  ANALYSIS     7 

the  resulting  ferric  chloride  reacting  with  the  potassium  ferrocyanide  to  form  the 
characteristic  Prussian  blue,  or  at  least  a  green  solution  which  deposits  Prussian  blue  on 
standing.  In  absence  of  nitrogen,  only  a  yellow  colour  is  obtained.  To  certain  nitrogenous 
substances  this  test  is  not  applicable  (e.g.  to  diazo -compounds,  which  evolve  nitrogen  too 
readily),  and  in  such  cases  either  the  potassium  is  replaced  by  a  mixture  of  potassium 
carbonate  and  powdered  magnesium  (Castellana,  1904),  or  the  substance  is  fused  with 
sodium  peroxide  and  the  mass  tested  for  nitrate  by  means  of  diphenylamine  (vol.  i,  p.  214). 

The  presence  of  halogens  (Cl,  Br,  I)  is  determined  by  heating  the  substance  with  pure 
lime,  dissolving  in  water  and  nitric  acid  and  precipitating  the  halogen  with  silver  nitrate. 
Also,  in  many  cases,  the  substance  can  be  heated  with  fuming  nitric  acid  and  silver 
nitrate  in  a  sealed  tube  (s  -e  later,  Quantitative  Analysis),  by  which  means  the  silver 
halogen  salt  is  formed  dir  ;ct1y  (Carius). 

Sulphur  also  can  be  detected  by  the  Carius  method,  the  substance  being  heated  in  a 
sealed  tube  with  fuming  nitric  acid  and  the  sulphuric  acid,  formed  from  the  sulphur  of  the 
organic  compound,  precipitated  with  barium  chloride  ;  or  by  heating  the  substance  with 
pure  sodium  peroxide,  a  sulphate  is  formed.  By  heating  the  substance  in  a  test-tube 
with  metallic  sodium  and  dissolving  the  mass  in  a  little  water  a  solution  of  sodium  sulphide 
is  obtained  which  blackens  a  piece  of  silver  foil  or  a  silver  coin. 

Phosphorus  and  other  elements  are  detected  by  the  Carius  method,  -the  substance 
being  oxidised  with  fuming  nitric  acid  and  the  liquid  tested  for  the  corresponding  acid 
(phosphoric,  &c.) 

QUANTITATIVE  COMPOSITION  (ELEMENTARY  ANALYSIS).  Lavoisier  first 
of  all  devised  an  apparatus  for  analysing  organic  substances  by  burning  them  with  oxygen 

&>  6  «       d  .#  £    9 

FIG.  13. 

a  —  5  cm.  free  ;  b  =>  12  cm.  spiral  of  oxidised  copper  gauze  ;  c  =  8-10  cm.  for  the  boat ; 
d  —  3  cm.  copper  spiral ;  e  =  40-45  cm.  granulated  cupric  oxide ;  /  =  3  cm.  oxidised  copper 
spiral  or  12  cm.  of  reduced  copper  spiral  for  nitrogenous  substances  ;  g  «=  5  cm.  free. 

under  a  bell-jar  ;  while  Gay-Lussac,  Thenard,  and  Berzelius  successively  improved  this 
process  by  burning  the  substance  in  presence  of  potassium  chlorate.  Gay-Lussac,  how- 
ever, showed  that  certain  nitrogenous  substances  cannot  be  burned  with  the  chlorate,  and 
suggested  as  a  general  and  more  certain  oxidising  agent  cupric  oxide,  which  when  hot 
gives  up  its  oxygen,  transforming  the  carbon  and  hydrogen  of  any  organic  compound  into 
carbon  dioxide  and  water  respectively,  while  the  nitrous  compounds  are  reduced  to  free 
nitrogen  by  passing  the  products  of  combustion  over  red-hot  copper  turnings.  But  it  is 
to  Liebig  that  the  credit  is  due  of  rendering  this  method  of  organic  analysis  simple  and 
exact  and  of  devising  simple  and  ingenious  forms  of  apparatus  for  absorbing  the  products 
of  combustion.  Even  to-day — disregarding  improvements  in  combustion  furnaces  and 
modifications  of  the  absorption  apparatus — the  determination  of  carbon  and  hydrogen 
(the  oxygen  is  estimated  by  difference)  is  carried  out  by  what  is  virtually  the  method 
employed  by  Liebig. 

The  method  most  commonly  used  is  as  follows  :  0-15-0-30  grm.  of  the  substance  is 
weighed  in  a  small  porcelain  boat,  which  is  then  filled  with  powdered  cupric  oxide, 
previously  heated  to  redness  and  perfectly  dry  ;  the  boat  is  then  introduced  into  the 
position  c  of  the  hard  glass  combustion  tube  (Fig.  13),  this  being  70-90  cm.  long,  or 
10-12  cm.  longer  than  jthe  combustion  furnace,*,  which  is  heated  by  25-30  gas  flames 
(Fig.  14). 

The  other  parts  of  the  tube  are  reserved  for  the  previously  heated  copper  spirals  and 
granulated  cupric  oxide  (Fig.  13).  When  a  fresh  combustion  is  to  be  made,  all  that  it 
is  necessary  to  do  is  to  remove  the  spiral  b  and  the  boat  and  to  introduce  the  new  substance 
into  the  tube,  which  is  already  charged  in  d,  e,  and  /  and  is  not  allowed  to  cool  below 
40°-60°. 

The  combustion  is  carried  out  in  the  furnace  shown  in  Fig.  14,  the  tube  being  closed 
at  a  with  a  good  cork  and  a  glass  tap  which  can  be  connected  at  will  with  a  gasometer 
containing  air  or  one  containing  oxygen,  which  should,  however,  before  reaching  the 
combustion  tube,  pass  through  tubes  containing  potassium  hydroxide  to  remove  the 


8    . 

carbon  dioxide,  and  then  through  drying  tubes  containing  calcium  chloride.  At  the 
other  end  the  combustion  tube  communicates  at  b,  first  with  a  tared  tube,  c,  containing 
granulated  calcium  chloride  to  absorb  the  water  formed  during  combustion  ;  then 
follows  the  tared  apparatus  d,  containing  potassium  hydroxide  solution  (30-35  per  cent.), 
which  absorbs  the  carbon  dioxide  from,  the  burnt  substance  and  is  furnished  with  a 
calcium  chloride  tube  to  retain  the  moisture  given  off  by  the  potassium  hydroxide  solution. 
Finally  follows  a  calcium  chloride  tube,  e,  which  is  not  weighed;  and  prevents  moisture 
entering  the  apparatus  from  the  air. 

Before  the  combustion  is  started  the  apparatus  is  tested  to  ascertain  if  it  is  perfectly 
air-tight.  This  is  done  by  closing  the  tap  a,  and  sucking  into  e  eight  or  ten  bubbles  of 
gas  ;  the  slight  rarefaction  produced  in  the  interior  of  the  combustion  tube  causes  the 
potash  solution  to  rise  in  the  first  large  bulb  to  a  level  which  should  remain  constant  for 
some  minutes.  The  burners  at  the  end  b  are  then  gradually  lighted  until  the  portion  / 
and  almost  all  of  the  portion  e  are  heated  to  redness.  The  spiral  b  is  then  gradually  heated 
from  the  a  end,  the  heating  being  gradually  extended  under  the  boat  so  that  the  substance 
is  completely  burnt.  During  the  combustion  bubbles  of  air  are  passed  into  the  tube 
from  the  gas-holder  so  as  to  transport  the  gases  produced  into  the  absorption  apparatus  ; 
during  the  last  10-15  minutes  a  gentle  current  of  oxygen  is  passed  through,  and  then  the 
flames  are  extinguished  and  air  again  passed  .for  10-15  minutes.  In  this  way  all  the 
gases  from  the  combustion  are  removed  from  the  combustion  apparatus  and  the  copper 
oxide  is  completely  reoxidised,  so  that  the  tube  is  ready  for  the  next  combustion. 


FIG.  14. 

The  increases  in  the  weights  of  the  potash  and  calcium  chloride  apparatus  give  the 
amounts  of  carbon  dioxide  and  water  respectively  formed  during  the  combustion,  and, 
since  44  parts  of  carbon  dioxide  correspond  with  12  parts  of  carbon  and  18  parts  of  water 
with  2*of  hydrogen,  the  quantities  or  percentages  of  carbon  and  hydrogen  in  the  substance 
can^be^calculated.  The  sum  of  these  two  percentages,  when  subtracted  from  100,  gives 
that  of  the  oxygen,  excepting  where  the  substance,  contains  nitrogen,  which  is  determined 
directly  by  methods  given  later.  In  this  way  the  percentage  composition  is  determined. 

For  determining  carbon  and  hydrogen  in  nitrogenous  substances  the  above  method  is 
modified  only  by  inserting  in  the  combustion  tube,  in  place  of  the  spiral  /  (Fig.  13),  one 
of  reduced  copper  gauze  x  about  15  cm.  long,  this  serving  to  fix  the  oxygen  from  the 
oxides  of  nitrogen  resulting  from  the  combustion  and  to  liberate  the  nitrogen,  which 
passes  unchanged  through  the  absorption  apparatus. 

If  the  substance  to  be  analysed  contains  sulphur  or  a  halogen,  the  combustion  is  made 
with  lead  chromate  in  place  of  the  granular  copper  oxide,  and  the  heating  is  more  gentle 
to  avoid  fusion  of  the  chromate.  By  this  means  the  sulphur  remains  fixed  in  the  tube 
as  lead  sulphate  and  the  halogens  as  halogen  salts  of  lead.  Halogens  can  also  be  fixed 
on  a  spiral  of  silver  foil  about  10  cm.  long  placed  at  /  (Fig.  13),  the  substance  being 
combusted  as  usual  with  cupric  oxide  ;  if  both  nitrogen  and  a  halogen  are  present  the 
copper  and  silver  spirals  are  used  together. 

A  new  apparatus,  which  admits  of  the  combustion  of  organic  substances  being  very 
rapidly  carried  put,  is  that  devised  by  Carrasco  and  Plancher  (1904-1906).  It  consists  of 

1  The  reduction  is  effected  in  a  separate  glass  tube,  through  which  a  current  of  hydrogen  is  passed  while  the 
spirals  are  heated  ;  when  the  copper  has  assumed  its  characteristic  red  colour,  the  flames  are  extinguished  and  the 
spirals  allowed  to  cool  in  the  current  of  hydrogen,  being  afterwards  kept  in  desiccators  ready  for  use  ;  or,  better, 
when  reduction  is  complete  and  the  spirals  are  still  hot,  the  tube  is  exhausted  and  is  kept  so  until  cold,  so  as  to  a  void 
t,ho  danger  of  hydrogen  being  occluded  by  the  copper. 


RAPID    ELEMENTARY    ANALYSIS 


9 


a  small  external  combustion  tube,  c  (Fig.  15),  of  hard  glass  and  about  20  cm.  long  and 
2  cm.  wide  and  slightly  expanded  at  the  lower  closed  end.  The  tube  is  closed  at  the  top 
by  a  rubber  stopper,  /,  through  which  passes  a  porcelain  tube,  e,  wound  round  with  an 
electric  resistance  formed  of  platinum-iridium  wire,  d  ;  along  the  interior  of  the  porcelain 
tubes  passes  a  thick  silver  wire,  which  starts  from  d,  the  negative  pole,  and  ends  in  a 
small  platinum  wire  loop  and  serves  to  convey  the  current  (3  amps,  at  20  volts).  The 
oxygen  for  the  combustion  traverses  OS  and  the  upright  tube  of  the  stand,  and  passes 
through  the  porcelain  tube  to  the  bottom  of  the  combustion  tube.  In  the  stopper,  /,  is 
fastened  a  piece  of  nickel  tube,  &,  which  is  united  to  the  +  pole  and  to  the  platinum 
spiral,  d,  and  serves  at  the  same  time  for  the  escape  of  the  gases  formed  by  the  combustion 
to  the  tube  r.  The  gases  are  absorbed  by  the  usual  tared  apparatus  (M=calcium  chloride, 


FIG.  15. 

p=  concentrated  potassium  hydroxide  solution),  but  with  nitrogenous  or  halogenatcd 
substances  the  gases  are  first  passed  through  a  U  -tube  containing  lead  dioxide  heated  to 
180°  by  means  of  a  small  furnace,  TO.  The  connections  a  and  b  are  insulated  from  one 
another  by  porcelain  and  rubber.  When  the  current  passes  through  the  resistance  the 
glass  tube  is  heated  to  redness,  and  the  substance  (0-12-0-20  grm.),  mixed  with  cupric 
oxide  or,  better,  with  platinised  porous  porcelain  powder,  and  placed  at  the  bottom  of 
the  glass  tube,  is  burned  by  heating  the  outside  of  the  tube  directly  with  a  Bunsen  flame. 
The  combustion  is  very  soon  completed,  the  platinum-iridium  spiral  apparently  accelerating 
the  oxidation  catalytically  ;  apart  from  the  time  occupied  by  the  weighings,  this  method 
requires  15-20  minutes,  and  usually  gives  good  results.  For  the  analysis  of  fairly 
volatile  liquids  or  of  substances  which  readily  sublime,  the  lower  part  of  the  combustion 
tube  is  drawn  out  almost  horizontally,  and  the  substance  is  mixed  with  platinised  porcelain 
powder  (2-3  per  cent,  of  platinum)  ;  liquids  can  be  heated  in  a  separate  tube  and  the 
vapour  then  injected  into  the  combustion  tube. 

An  electrical   method  for   determining   carbon,    hydrogen,    and   sulphur   in   organic 
subtances  was  also  proposed  by  Morse  and  Gray  in  America  in  1906. 


10 


ORGANIC    CHEMISTRY 


QUANTITATIVE  DETERMINATION  OF  NITROGEN.  (1)  Dumas'  Method. 
The  nitrogenous  organic  substance  (0-2-0-3  grm.)  is  heated  in  a  hard  glass  tube  similar 
to  that  shown  in  Fig.  1 3,  but  closed  at  the  end,  a.  The  portions  a  and  6  contain  sodium 
hydrogen  carbonate  or  magnesium  carbonate  ;  between  b  and  c  is  placed  a  small  plug  of 
copper  gauze,  in  c  granulated  copper  oxide,  and  in  d  powdered  copper  oxide.  Then  follows 
a  space  10  cm.  in  length  in  which  is  placed  the  substance  to  be  analysed,  this  being  weighed 
and  mixed  with  powdered  cupric  oxide  ;  next  comes  granulated  cupric  oxide,  and  in  / 
a  spiral  of  reduced  copper,  10-12  cm.  long.1 

The  extremity,  g,  of  the  tube  is  connected  by  means  of  a  gas  delivery  tube  with  a 
graduated  tube  (25  or  50  c.c.),  placed  upside  down  in  a  basin  of  mercury  and  filled  half 
with  mercury  and  half  with  concentrated  potassium  hydroxide  solution.  This  graduated 
tube  may  have  the  form  devised  by  Dumas  and  shown  in  Fig.  16  ;  the  gas  from  the 
combustion  tube  passes  into  the  tube  a,  furnished  with  a  clip,  m, 
thence  through  a  little  mercury  in  the  bottom  of  the  tube  b, 
which  is  filled  with  potassium  hydroxide  solution  and  is  in  com- 
munication with  a  reservoir,  c,  of  this  solution.  The  operation 
is  begun  by  heating  the  combustion  tube  at  the  point  where 
the  magnesium  carbonate  lies  ;  the  carbon  dioxide  thus  evolved 
expels  the  air  from  the  apparatus  into  b,  whence  it  is  driven  by 
raising  the  reservoir,  c,  and  opening  the  cock  at  the  top  of  b. 
The  carbon  dioxide  is  absorbed  by  the  potash  solution,  and 
when  no  more  air  collects  in  6  the  magnesium  carbonate  is  no 
longer  heated.  The  copper  spiral  and  the  copper  oxide  are  now 
gradually  heated  in  the  same  way  as  for  the  estimation  of  carbon 
and  hydrogen,  the  heating  being  slowly  extended  until  it  reaches 
the  substance  itself.  Oxides  of  nitrogen  are  decomposed  by  the 
copper  spiral,  so  that  all  the  nitrogen  is  evolved  in  the  free  state 
and  collects  in  b.  Finally  the  nitrogen  remaining  in  the  com- 
bustion tube  is  driven  into  b  by  means  of  carbon  dioxide  formed 
by  again  heating  the  magnesium  carbonate. 

At  the  end  of  the  operation,  in  order  to  measure  the  nitrogen, 
a  graduated  tube  filled  with  water  is  inverted  over  d,  and  the  cock 
at  the  top  of  b  having  been  opened,  the  reservoir,  c,  is  raised  until 
all  the  gas  passes  into  the  graduated  tube.  The  latter  can  then 
be  removed  to  a  large  cylinder  full  of  water  and  when,  after  a 
few  minutes,  the  gas  has  assumed  the  temperature  of  the  water  (shown  by  an  accurate 
thermometer)  the  tube,  grasped  by  a  clip  (the  hand  would  warm  it),  is  arranged  so  that 
the  level  of  the  liquid  inside  it  coincides  with  that  outside  and  the  volume  (v)  of  the  gas 
read  off.  At  the  same  time  the  atmospheric  pressure  (b)  is  read,  and  the  exact  tempera- 
ture (t)  of  the  water.  The  percentage  of  nitrogen  (p)  in  the  substance  is  then  calculated 
by  means  of  the  following  formula  : 

v.  (b  -w).  0-12511 
P  =  s.760(l  +  0-00367-0 

where  s  indicates  the  weight  of  substance  taken,  w  the  pressure  of  water  vapour  expressed 
in  mm.  of  mercury  (see  vol.  i.  p.  34)  and  0-0012511  grm.  the  weight  of  1  c.c.  of  moist 
nitrogen  at  0°  and  760  mm.  (Rayleigh  and  Ramsay). 

When  several  determinations  of  nitrogen  are  to  be  carried  out  the  procedure  is  some- 
times simplified  by  using  a  combustion  tube  open  at  both  ends,  like  that  of  Fig.  13,  the 
magnesium  carbonate  or  sodium  bicarbonate  being  omitted  and  the  combustion  tube 
being  connected  at  a  with  a  small  Kipp's  apparatus  for  the  evolution  of  carbon  dioxide 
(marble  and  hydrochloric  acid),  care  being  taken  to  free  the  apparatus  from  all  air  by  a 
prolonged  current  of  carbon  dioxide. 

|(2)  KjelddhVs  Method  (Dyer's  modification).  0-5-1  grm.  of  the  substance  is  placed  in 
a  hard  glass  flask  (200-300  c.c.)  with  a  long  neck,  into  which  penetrates  the  stem  of  a  funnel 
used  to  cover  the  flask  (Fig.  17).  20  c.c.  of  concentrated  sulphuric  acid  (66°  Be.)  and 

1  In  this  case  the  copper  spiral  can  be  rapidly  reduced  by  heating  it  over  a  large  non-luminous  gas  flame  and 
dropping  it  into  a  thick-walled  test-tube  containing  \  c.c.  of  ethyl  or,  better,  methyl  alcohol ;  the  tube  is  immediately 
closed  by  a  rubber  stopper  through  which  passes  a  glass  tube.  The  latter  is  connected  with  a  pump  until  the  spiral 
is  cold. 


FIG.   16. 


ESTIMATION    OF    NITROGEN 


11 


a  drop  of  mercury  (which  acts  as  a  catalytic  oxidising  agent)  are  added,  and  the  contents 
of  the  flask  are  heated,  at  first  gently  and  finally  more  strongly,  until  vigorous  boiling 
sets  in.  10  grms.  of  potassium  sulphate  are  then  added,  a  little  at  a  time,  the  heating 
being  continued  until  the  liquid  is  decolorised,  by  which  time  the  whole  of  the  nitrogen  is 
transformed  into  ammonium  sulphate.  After  the  flask  has  been  allowed  to  cool,  its 
contents  are  washed  out  with  water  into  a  flask  already  containing  200-300  c.c.  of  water. 
3-4  grms.  of  zinc  dust  (which  decomposes  ammoniacal 
compounds  of  mercury  and  prevents  bumping  by  the 
evolution  of  hydrogen)  are  then  added,  and  the  flask 
closed  with  a  rubber  stopper  through  which  passes  a 
tapped  funnel  containing  120-160  c.c.  of  concentrated 
sodium  hydroxide  solution  (30-35  per  cent.)  and  a  glass 
bulb  (Figs.  18  and  19)  communicating  with  a  simple 
condensing  tube  dipping  into  a  flask  containing  a  mea- 
sured volume  of  standard  sulphuric  acid  and  a  drop  of 
methyl  orange.  In  order  to  prevent  spurting  of  the 
caustic  soda  and  its  introduction  into  the  condenser 
tube,  the  glass  bulb  is  fitted  with  a  delivery  tube  curved 
towards  the  wall  of  the  bulb  ;  it  is,  however,  as  well 
to  push  into  this  tube,  almost  as  far  as  the  bulb,  a  small 
plug  of  glass-wool  or  asbestos.  Solutions  of  soda  more 
concentrated  than  35  per  cent,  often  lead  to  spurting. 
About  one-half  the  liquid  is  distilled  and  the  excess 
of  sulphuric  acid  remaining  in  the  collecting  flask 
determined]by  titration  with  alkali.  Hence  the  amount  of  ammonia  fixed  by  the  acid  can 
be'calculated  and  so  the  percentage  of  nitrogen  in  the  substance  analysed.  In  Figs.  17  and 
19  are  shown  forms  of  apparatus  with  which  it  is  possible  to  carry  out  several  determina- 
tions simultaneously. 


FIG.  17. 


FIG.  18. 


FIG.  19. 


Kjeldahl's  method  cannot  be  used  for  the  analysis  of  organic  substances  which  contain 
nitrogen  either  united  to  oxygen  (nitro  compounds)  or  forming  part  of  a  pyridine  or  similar 
nucleus  (quinoline,  &c.) 

(3)  Will  and  Varrentrapp's  Method.  This  method  is  based  on  the  principle  that 
almost  all  nitrogenous  organic  substances  (which  do  not  contain  nitrogen  linked  to  oxygen, 
such  as  the  nitro-compounds),  when  they  are  heated  with  an  alkali  hydroxide  or,  better, 
with  soda  lime  (see  vol.  i,  p.  490),  yield  hydrogen,  which  transforms  the  nitrogen  into 
ammonia.  Little  use  is  made  of  this  method  to-day. 

QUANTITATIVE  DETERMINATION  OF  THE  HALOGENS.  The  method  most 
commonly  used  is  that  of  Carius.  The  substance  (0-15-0-2  grm.)  is  weighed  out^in  a 
small  tube,  which  is  then  introduced  into  a  large,  hard  glass  tube  30-40  cm.  long  and 
2-3  cm.  wide,  closed  at  one  end  and  containing  about  2  c.c.  of  fuming  nitric  acid  and  about 
0-5  grm.  of  solid  silver  nitrate  ;  this  introduction  is  effected  in  such  a  way  that  the  acid 
does  not  enter  the  small  tube.  The  large  tube  is  then  softened  near  the  open  end  by  heating 
in  the  blow-pipe  flame  andjjradually  drawn  out  to  a  point,  the  walls  of  the  tube  being 


12 


allowed  to  thicken  during  the  fusion  (Fig.  20,  B,  shows  the  upper  part  of  the  tube  on  a 
larger  scale).  After  being  allowed  to  cool  in  a  vertical  position,  the  tube  is  introduced 
into  a  thick -walled  iron  sheath,  which  is  closed  with  a  screw-cap.  It  is  then  safe  to  incline 
the  tube  and  introduce  it  into  a  bomb-furnace  (Fig.  21),  which  holds  four  or  more  tubes 
and  is  raised  slightly  at  one  end  ;  this  is  heated  for  4-6  hours,  the  temperature  being 
raised  gradually  to  about  250°.  Sometimes  the  tubes  burst  owing  to  the  great  internal 
pressure,  but  without  danger  from  flying  fragments  of  glass  owing  to  the  protection  of 
the  iron  sheaths  and  of  the  folding  shutters  at  the  ends  of  the  furnace,  these  being  lowered 
during  the  heating. 

At  the  end  of  the  operation,  when  the  tube  is  cool,  it  is  taken  from  the  iron  sheath, 
held  in  a  vertical  position  and  its  point  (Fig.  20,  A  a)  softened  in  a  Bunsen  flame.  When 
the  pressure  in  the  tube  has  been  thus  relieved,  a  scratch  is  made  with  a  file  at  the  point 
marked  6,  and  the  file-mark  touched  with  a  red-hot  glass,  with  the  result  that  the  upper 
part  of  the  tube  breaks  off.  The  tube  is  then  carefully  emptied  and  washed  out  into  a 
beaker  with  water,  the  small  tube,  held  in  pincers  or  a  piece  of  platinum  wire,  being  well 
washed  inside  and  outside  before  removal.  The  liquid  is  heated  and  the  precipitated  silver 


FIG.  20. 


FIG.  21. 


halogen  compound  is  then  collected  on  a  filter,  washed,  dried  in  an  oven,  detached  from 
the  filter  and  heated  in  a  weighed  porcelain  crucible  until  it  just  begins  to  melt.  After 
being  allowed  to  cool  in  a  desiccator,  the  crucible  is  weighed  and  the  amount  of  halogen 
contained  in  the  organic  substance  calculated  from  the  weight  of  silver  haloid. 

QUANTITATIVE  DETERMINATION  OF  SULPHUR  AND  PHOSPHORUS. 
This  is  carried  out  by  the  Carius  method  in  the  same  way  as  for  halogens,  except  that 
no  silver  nitrate  is  introduced  into  the  tube.  At  the  end  of  the  heating,  the  sulphur  is 
obtained  as  sulphuric  acid  or  the  phosphorus  as  phosphoric  acid,  estimation  of  the  amounts 
of  these  acids  being  effected  by  the  ordinary  methods.  The  halogens,  sulphur  and 
phosphorus,  may  also  be  determined  after  fusion  of  the  substance  with  pure  sodium 
peroxide.  ' 


CALCULATION  OF  THE  EMPIRICAL  FORMULA.  From  the 
results  of  the  elementary  analysis  of  an  organic  substance  can  be  calculated 
the  percentage  composition,  i.e.  the  quantity  of  each  component  in  100  parts 
of  substance.  To  deduce  the  chemical  formula,  that  is,  the  proportions  in 
which  the  different  atoms  enter  into  the  molecule,  the  percentage  weight  of 
each  component  is  divided  by  the  corresponding  atomic  weight,  the  numbers 


MOLE. CULAR    WEIGHTS  13 

thus  obtained  giving  the  proportions  between  the  numbers  of  atoms  of  the 
different  elements. 

These  numbers  sometimes  give  directly  the  numbers  of  atoms  contained 
in  the  molecule,  but  in  other  cases  they  represent  multiples  or  submultiples  of 
the  real  numbers  of  atoms. 

If,  for  example,  lactic  acid  is  analysed,  the  percentage  composition  is  found 
to  be  :  C,  40  per  cent.  ;  H,  6-6  per  cent.  ;  0,  53-4  per  cent  ;  by  dividing  these 
numbers  by  the  corresponding  atomic  weights,  the  following  numbers  are 
obtained:  C,  3-3  (i.e.  -*-£);  H,  6-6  (*-£);  and  0,  3-3  (^*-).  These  pro- 
portions have  a  common  factor,  3-3,  and  division  by  this  gives  1C,  2H, 
and  10,  i.e.  CH2O,  which  is  an  empirical  minimum  or  formula,  the  simplest 
formula  expressing  the  proportions  between  the  numbers  of  atoms  of  the 
different  elements. 

This  minimum  formula  does  not,  however,  represent  the  molecular  magni- 
tude, and,  in  fact,  analyses  of  formaldehyde,  acetic  acid,  grape  sugar,  &c., 
give  the  same  percentage  composition  and  the  same  minimum  formula,  CH20, 
which  must  hence  be  a  submultiple  of  the  formulae  of  these  substances. 

^  knowledge  of  the  percentage  composition  is  not  sufficient  to  determine 
the  true  molecular  formula  ;  the  molecular  magnitude,  i.e.  the  molecular 
weight,  must  also  be  known  in  order  to  permit  of  a  choice  between  the  various 
multiples.  By  making  use  of  one  of  the  methods  described  in  vol.  i,  •"  Inorganic 
Chemistry  "  (pp.  39,  81  et  seq.),  the  molecular  weight  of  lactic  acid  is  found  to  be 
90,  so  that,  of  the  various  possible  formulae,  CH20  (mol.  wt.  30),  C2H402 

(mol.  wt.  60),  C3H603  (mol.  wt.  90),  C4H804  (mol.  wt.  120) C6H1206 

(mol.  wt.  180),  &c.,  only  C3H603  corresponds  with  lactic  acid.  But  even 
this  formula  and  the  empirical  formula  tell  nothing  concerning  the  grouping 
of  the  atoms  in  the  molecule  which,  as  is  explained  in  the  following  pages,  is 
given  by  the  constitutional  formula. 

DETERMINATION  OF  THE  MOLECULAR  WEIGHT  BY 
CHEMICAL  MEANS 

In  lactic  acid  one-sixth  of  the  hydrogen  can  be  substituted  by  a  metal,  so  that  there 
must  be  at  least  six  (or  a  multiple  of  six)  atoms  of  hydrogen  in  the  acid,  the  empirical 
formula  being  necessarily  at  least  trebled,  giving  C3H603.  To  ascertain  if  this  is  the  true 
formula,  a  derivative  of  the  acid  is  prepared,  such  as  the  silver  salt,  which  can  easily  be 
obtained  pure.  Analysis  of  this  salt  shows  it  to  contain  54-8  per  cent,  of  silver,  and  the 
atomic  weight  of  silver  being  107-7,.  calculation  indicates  that  the  residue  of  the  lactic 
acid  combined  with  107-7  parts  of  silver  weighs  89.  Assuming  that  only  1  atom  of  silver 
has  entered  the  lactic  acid  in  place  of  1  of  hydrogen  (as  can,  indeed,  be  deduced  from  the 
fact  that  the  quantity  of  hydrogen  in  the  salt  is  five -sixths  of  that  originally  present  in 
the  acid),  the  weight  of  the  lactic  acid  would  be  89  +  1,  or  90.  The  true  formula  of  the 
acid  would  hence  be  that. corresponding  with  a  molecular  weight  of  90,  i.e.  C3H6O3. 

For  acid  substances  in  general  this  chemical  method  may  be  employed  for  determining 
the  molecular  weight,  making  use  of  the  silver  salt  and  determining  if  the  acid  is  mono-, 
di-,  or  tri-basic  (that  is,  ascertaining  if  the  silver  replaces  1,  2,  or  3  atoms  of  hydrogen), 
the  calculation  being  then  based  on  the  presence  of  1,  2,  or  3  atoms  of  silver  in  the  salt. 

For  basic  substances,  the  molecular  magnitude  may  be  determined  chemically  by 
analysing  the  platinichlorides,  the  formulae  for  which  are  always  of  the  type  of  that  of 
ammonium  platinichloride  :  PtCl^NHg-HCl^,  the  ammonia  being  replaced  by  the  organic 
base,  which  is  mono-  or  di-acid,  according  as  it  replaces  one  or  two  molecules  of  ammonia 
in  the  platinichloride. 

For  other  (indifferent)  organic  substances  derivatives  are  prepared  by  substituting 
chlorine  atoms  for  one  or  more  hydrogen  atoms,  the  proportion  of  chlorine  being  then 
estimated  ;  the  calculation  is  then  similar  to  that  described  above. 

The  chemical  method  for  determining  the  molecular  magnitude  does  not  always  give 
certain  results  :  experimental  difficulties  sometimes  occur  and  often  entail  great  labour. 


14  ORGANIC    CHEMISTRY 

Consequently  the  determination  of  molecular  weights  is  usually  effected  by  physical 
methods :  vapour  density  method,  cryoscopic  method,  ebullioscopic  method,  &c.,  these 
being  all  described  and  illustrated  in  vol.  i  (Part  I). 

POLYMERISM 

It  sometimes  happens  that  the  analysis  of  different  substances  shows  them 
to  have  the  same  percentage  composition,  although  their  chemical  and  physical 
properties  are  different ;  thus,  for  example,  acetic  acid,  lactic  acid,  glucose,  &c., 
contain  the  same  elements,  C,  H,  and  0,  in  the  same  proportions,  there  being 
2n  hydrogen  atoms  and  n  oxygen  atoms  for  every  n  carbon  atom.  Accurate 
study  of  these  compounds  and  determination  of  the  molecular  magnitude 
(molecular  weight)  shows  that  the  differences  depend  on  the  true  formulae 
being  multiples  of  the  minimum  or  empirical  formula.  Thus,  whilst  the 
molecule  of  acetic  acid  is  represented  by  C2H402,  that  of  lactic  acid  corre- 
sponds with  C3H603,  and  that  of  glucose  with  C6H1206.  These  molecules  are 
hence  all  multiples  of  a  hypothetical  complex  CH20,  the  ratios  (but  not  the 
absolute  quantities)  between  carbon,  hydrogen,  and  oxygen  being  the  same 
(1:2:1)  in  all  cases.  These  compounds  are  termed  polymerides  and  the 
phenomenon  is  known  as  polymerism. 

In  some  instances,  however,  it  happens  that  the  molecular  magnitude  is 
not  sufficient  to  differentiate  certain  compounds,  which,  besides  containing  the 
same  elements  in  the  same  proportions  (equal  percentage  compositions),  have 
also  the  same  molecular  magnitudes,  although  differing  in  their  physical  and 
chemical  properties.  To  explain  the  existence  of  these  isomeric  compounds, 
the  chemical  nature  of  carbon  must  be  studied  more  in  detail. 


VALENCY  OF  CARBON,   ISOMERISM,   AND 
CONSTITUTIONAL  FORMULA 

On  the  foundation  of  multivalent  radicles,1  discovered  by  Odling,  and  of 
the  investigations  of  Frankland  (1852),  which  showed  that  nitrogen,  phos- 
phorus, and  other  elements  easily  formed  compounds  with  three  or  five 
equivalents  of  other  elements,  Kekule,  in  1857  and  1858,  accurately  developed 
the  true  conception  of  valency,  showing  the  constant  tetravalency  of  carbon 
and  thus  widening  the  horizon  of  organic  chemistry  and  originating  the 
remarkable  theoretical  and  practical  development  of  the  past  half -century. 

1  Theory  of  Radicles  and  Types.  In  the  first  twenty  years  of  last  century,  various  compounds  were 
discovered  which  stood  in  apparent  contradiction  to  the  electro-chemical  theory  of  dualistic  formulae,  put 
forward  by  Berzelius  (vol.  i.  p.  44) ;  in  fact,  in  certain  compounds,  the  hydrogen  (electro-positive)  was  replaced  by 
chlorine  (electro-negative)  without  appreciably  changing  the  chemical  characters  of  the  original  compounds.  It 
was  then  that  chemical  combinations  came  to  be  represented  by  unitary  formulae,  no  account  being  taken  of  the 
grouping  of  the  atoms  in  the  molecule. 

But  gradually,  as  the  number  of  new  organic  substances  increased,  certain  analogies  became  evident  in  their 
chemical  behaviour.  In  studying  cyanogen  Gay-Lussac  (1815)  had  indeed  met,  in  various  reactions  and  in  various 
substances,  the  residue  or  radicle  CN,  which  behaved  as  a  monovalent  element  (like  the  halogens),  combining  with 
one  atom  of  different  monovalent  metals,  &c.  In  1832  Liebig  and  Wohler  discovered  and  studied  a  monovalent 
atomic  group  or  radicle,  benzoyl,  C,H6O,  which  was  found  in  oil  of  bitter  almonds  combined  with  an  atom  of 
hydrogen  (C7H,O) ;  on  oxidation  by  the  air,  this  essence  became  transformed  into  benzoic  acid,  C,H6O2,  which 
with  PC15  gave  benzoyl  chloride,  C7H6OC1,  and  this,  in  its  turn,  gave  the  aldehyde  C7H6O,  when  treated  with 
nascent  hydrogen,  or  benzoic  acid  under  the  action  of  water.  All  these  compounds  contain  the  monovalent 
benzoyl  nucleus,  C7H5O,  which  passes  unchanged  from  one  to  the  other  by  combining  with  monovalent  atoms  or 
groups.  In  1833,  in  a  classic  work,  Bunseu  studied  another  radicle,  cacodyl,  which  is  a  monovalent  organic  arsenic 

residue,  As<C^pTT*.    Later,  in  1837,  Dumas  advanced  and  developed  the  theory  of  radicles,  studying  and  classifying 

organic  compounds  with  reference  to  the  different  radicles  contained  in  them,  these  radicles  thus  coming  to  be 
considered  almost  as  the  elementary  substances  of  organic  chemistry.  The  condensation  of  simple  radicles  then  leads 
to  a  compound  radicle,  forming  a  complex  which  can  unite  with  other  atoms  or  atomic  groups.  Liebig  supported 
this  new  theory,  whilst  Berzelius  strenuously  opposed  it,  reproaching  Dumas  for  regarding  all  chemical  combinations 
as  due  to  reciprocal  interchanges  of  radicles. 

Dumas  and,  still  more  so,  Laurent,  as  a  consequence  of  the  discovery  of  new  substances,  arrived  logically  at 
the  theory  of  substitution,  which  admits  the  possibility  of  replacing,  one  by  one,  the  elements  forming  the  radicle  or 


RADICLES:    SUBSTITUTION  15 

Kekule  and,  independently  of  him,  Cooper  brought  to  light  another  most 
important  property  of  carbon,  resulting  from  its  four  equivalent  valencies  ; 
they  showed  that  carbon  atoms  possess  also  the  property  of  combining  directly 
one  with  another,  in  a  greater  or  less  number,  mutually  saturating  one,  two, 
or  even  three  valencies  and  forming  varying  chemical  compounds.  For 
convenience,  we  represent  these  compounds  graphically,  placing  the  carbon 
atoms  in  an  open  or  closed  chain  and  saturating  the  valencies  remaining  free 
with  other  elements  (usually  hydrogen  and  oxygen).  We  have  thus  a  series 
of  groups  differing  according  as  the  atoms  united  in  a  chain  are  few  or  many 
(even  more  than  30),  according  to  whether  the  chain  is  branched  by  means 
of  lateral  chains,  and  also  according  as  the  valencies  saturated  between  carbon 
and  carbon  are  1,  2,  or  3. 

If  we  represent  the  valencies  of  carbon  by  strokes,  the  valencies  of  the  different  carbon 

nucleus  of  certain  compounds  by  other  elements  or  by  radicles  of  other  compounds  (Dumas  termed  this  phenomenon 
of  substitution  metalepsy). 

Not  only  the  hydrogen  and  oxygen  but  also  the  carbon  of  the  radicles  could,  according  to  Laurent,  be  replaced 
by  other  radicles  or  other  elements,  e.g.  by  chlorine,  without  the  fundamental  characters  of  the  original  substances 
being  substantially  changed. 

These  last  consequences  of  the  theory  of  substitution  in  radicles  (Dumas)  or  in  nuclei  (Laurent)  were  combated 
not  only  by  Berzelius,  but  even  by  Liebig,  who  attempted  to  cover  these  new  conceptions  with  ridicule  and  pub- 
lished in  his  "  Annalen  "  (1840)  a  pungent  satire  in  the  form  of  a  letter  from  Paris  which  was  signed  "  S.  C.  H. 
Windier  "  (Schwindler  being  the  German  for  swindler  I),  and  which  made  the  astonishing  statement  that  it  had 
been  found  possible  to  replace  all  the  atoms  of  the  molecule  of  manganese  acetate  by  the  corresponding  number 
of  chlorine  atoms,  the  resulting  substance  retaining  the  characters  of  the  original  salt,  although  formed  of  chlorine 
alone ;  further,  on  the  basis  of  the  new  theory,  it  was  concluded  that  the  chlorine  used  in  England  to  bleach 
textiles  replaced  the  hydrogen,  oxygen,  and  carbon,  and  that  already  chlorine  was  being  spun  for  the  manufacture 
of  nightcaps,  which  were  greatly  appreciated  !  ! 

Nevertheless,  the  new  conceptions  triumphed  with  the  aid  of  numerous  discoveries,  which  served  to  confirm, 
more  and  more,  the  ideas  of  Laurent  and  Dumas  And  with  the  studies  of  Gerhardt,  new  horizons  were  opened  to 
organic  chemistry,  which  for  so  many  years  found  a  solid  bo.sis  in  Laurent  and  Gerhardt's  (1852)  theory  of  types, 
these  clearing  up  the  nebulous  i4eas  then  still  held  on  the  atom  and  the  molecule  ;  and  it  is  due  to  these  two 
investigators  that  Avogadro's  work,  denied  by  everybody,  finally  assumed  the  important  position  accorded  to  it 
in  modern  chemistry. 

All  organic  and  inorganic  compounds  were  explained  by  comparing  them  with  simple  types  of  inorganic  sub- 

TT  \       TT  "1 

stances  of  well-known  constitutions.    The  fundamental  types  of  Gerhardt  were  four  in  number:  „[-,  fjr« 

N  S±J       {jlJ 


It  was  supposed  that  all  the  principal  chemical  compounds  then  known  were  derived  from  these  types  by 
simple  substitution  of  the  hydrogen  by  other  elements  and  radicles.    Fro  in  the  first  type  can  be  derived,  for 

ON"    I  ft    TT      "i  ft    TT     ~\ 

example  :  hydrocyanic  acid,    -    (  ,  ethane,     *  T?  f,  ethyl  cyanide,    L.J  f,  &c. ;  from  the  second,  sodium  chloride, 
n.)  H)  UJN  } 

Na  1  CHI  CHOl 

*C1  / '  e("'kyl  chloride.    2  _?  j- ,  acetyl  chloride,    2    3™  | ,  and  so  on.    With  the  third  type  correspond,  for  example, 

sodium  hydroxide,    JJ  r  O,  nitric  acid,      ,J  f  O,  acetic  acid,   '2    *„  J-  O,  nitric  anhydride,  XTr.2  \  O,  acetic  anhydride, 

tlJ  Jtt  J  J±  J  JMUj-' 

C2HS0  I  Q   &c 

From  the  fourth  type,  Hofmann  and  Wurtz  deduced  theoretically  and  prepared  in  the  laboratory  a  large  number 
of  compounds,  part  or  all  of  the  hydrogen  atoms  of  ammonia  being  replaced  ;  for  example,  ethylamine      H  j-N, 

dicthylamine,  C2H6  ]-N,  trimethylamine,  CH3  J-N,  acetamide,          H  \~S,  &c. 

Hj  CH3J  Hj 

To  explain  the  existence  of  polybasic  acids  and  various  other  substances,  Odling,  Williamson,  and  Kckul6 

51°     HIO 

had  recourse  to  multiple  types,  sulphuric  acid  being  regarded  at.  derived  from  the  double  water  type  „        SO2  [  „, 

H)  0, 

and  similarly  succinic  acid  CjHjOj  f     ,  &c. ;  for  glycerol,  a  triple  type  was  assumed,  and  so  on. 
H'  U 

H 
In  1856  Kekule  introduced  another  very  important  type,  that  of  marsh  gas,  „  VC,  with  tetravalent  carbon, 


to  which  he  referred  numerous  organic  compounds  ;   also  certain  compounds  can  be  referred  both  to  marsh  gaa 


PTT  -v 
8 


H 


and  to  ammonia,  for  example,  methylamine,      H  [-N,  or      f;  VC,  and  from  these  different  methods  of  considering 


the  constitution  and  the  reference  to  different  types,  were  deduced  various  processes  for  preparing  one  and  the 
same  compound  from  different  starting  materials 


16 


ORGANIC    CHEMISTRY 


atom  chains  are  given  by  the  number  of  free  valencies  which  are  not  used  in  uniting  the 
carbon  atoms  among  themselves  and  which  can   be  saturated  by  different  elements 
(usually  H,  O,  N),  giving  rise  to  an  enormous  number  of  organic  compounds. 
The  following  are  some  of  these  hypothetical  carbon  atom  chains  : 


(1) 


C/  C— 

(2)   II  >;      (3)    HI 


c— 


Hexavalent        Tetravalent  Divalent 


HI      ;       (4)    C=;  (5)    C— ;  (6)    C      ;  (7)    C      ; 

c-  \/  \/  •          \/  \  / 

fir—  P—  P—  r1/ 

°\  C\  °\  °\ 


(8) 


(9)    —  C— Of-  ,  &c. 


(10) 


/c\ 

— C         C— 

(11)   II     I 

f"1  f-\ 


V 


(12) 


_  P  __  pi  _ 

||       II    ; 

—  C        C— 


(13) 


>c 
>c 


— C         C— 


(14) 


— C         C— 


A 


— c 


(15) 


-cx 
c       c- 

II     I 

C         C— 


Among  these  chains  are  two  (Nos.  8  and  9)  containing  four  carbon  atoms  and  having 
equal  numbers  of  free  valencies.  By  saturating  these  ten  free  valencies  with  ten  H  atoms 
two  compounds  are  obtained  (these  have  actually  been  prepared)  which  contain  equal 
numbers  of  C  and  H  atoms,  and  have  therefore  the  same  percentage  composition  and  the 
same  molecular  weight. 

The  physical  and  chemical  differences  of  these  two  compounds,  termed 
isomerides,  are  explained  by  the  different  grouping  or  linking  of  the  atoms 
in  the  molecule.  In  their  chemical  transformations,  isomerides  give  up  or 
exchange  quite  different  atomic  groups  or  atoms,  owing  to  the  different  functions 
and  positions  occupied  by  these  atoms  or  groups  in  the  molecule. 

It  is  hence  not  sufficient  to  represent  organic  compounds  by  an  empirical 
molecular  formula,  the  structural  or  constitutional  formula,  deducible 
from  the  graphic  representation  of  the  chains  illustrated  above,  being  necessary 
in  many  cases  to  distinguish  between  isomerides. 

To  decide  which  of  two  isomeric  formulae  should  be  assigned  to  a  given 
substance,  various  chemical  reactions  are  carried  out  with  the  substance, 
study  of  the  new  products  indicating  the  constitutional  formula. 

An  example  will  render  these  ideas  clear  :  It  is  found  that  ethyl  alcohol  (ordinary 
liquid  alcohol)  and  gaseous  methyl  ether  have  different  physical  and  chemical  properties, 
although  they  possess  the  same  percentage  composition  and  the  same  molecular  magnitude, 
represented  by  the  formula  C2H60.  The  constitutions  or  internal  molecular  structures 
of  the  two  compounds  are  determined  by  a  study  of  the  following  chemical  reactions  : 
treatment  of  the  alcohol  with  hydrochloric  acid  gives  first  a  compound  C2H6C1  (ethyl 
chloride),  one  atom  of  monovalent  chlorine  having  replaced  one  atom  of  oxygen  and  one 
of  hydrogen  or  a  hydroxyl  residue,  OH.  By  means  of  nascent  hydrogen,  the  chlorine 
atom  of  ethyl  chloride  can  be  replaced  by  a  hydrogen  atom,  giving  the  compound 
C2H6  (ethane).  These  reactions  are  hence  expressed  by  the  following  equations : 


CHEMICAL    CONSTITUTION  17 

(1)  C2H6.OH  +  HC1  =  H20  +  C2H5C1  ;    (2)  C2H5C1  +  H2  =  HC1  +  C2H6  ;    but  ethane 

H\         /H 

can  have  only  the  constitution,  H-^C  —  C~—  H,  i.e.  CH3  —  CH3,  so  that  the  alcohol  will 

H/  \H 

Hv  ,OH 

have  the  constitution  H-^C  —  0^—  H 
H/          \E 

On  the  other  hand,  it  is  found,  by  various  reactions,  that  the  six  hydrogen  atoms  of 
methyl  ether  present  no  difference  one  from  another,  and,  no  matter  under  what  conditions 
hydriodic  acid  acts  on  the  ether,  it  eliminates  the  oxygen  as  water,  and  another  product 
is  obtained  which  contains  only  one  carbon  atom  in  the  molecule  :  The  reaction  hence  takes 
place  according  to  the  equation  : 

G2H60  +  2HI  =  2CH3I  + 


It  is  evident,  then,  that  in  methyl  ether  the  six  hydrogen  atoms  are  united  homo- 
geneously to  the  two  atoms  of  carbon  and  that  the  carbon  atoms  are  joined,  not  directly, 
but  indirectly,  by  means  of  an  oxygen  atom,  which  is  readily  eliminated.  The  constitu- 
tional formula  of  methyl  ether  will  hence  be  : 

H 


H-)C—  0—  OH      or      CH3—  O—  CH3. 
H/  \H 

Use  is  not  always  made  of  constitutional  formulae,  since  they  are  not 
simple  and  are  often  inconvenient  to  write  ;  hence  attempts  are  made  to 
simplify  them  by  indicating  the  more  important  groups  or  residues  contained 
in  the  molecule  and  giving  at  the  same  time  an  idea  of  the  constitutions  and 
of  the  functions  of  these  groups  ;  this  is  done  by  means  of  the  so-called  rational 
formulce.  The  rational  formula  of  ethyl  alcohol  will  be  C2H5*OH,  in  which 
the  monovalent  OH  residue,  characteristic  of  all  the  alcohols,  is  separated  ; 
that  of  acetic  acid  will  be  CH3'COOH,  the  group  COOH  being  characteristic 
of  and  common  to  all  organic  acids,  &c. 

METAMERISM.  Constitutional  and  rational  formulae  explain  clearly 
isomerism  in  general  and  also  the  special  case  bearing  the  name  metamerism. 
When,  to  an  atom  of  a  polyvalent  element  are  united  one  or  more  groups  in 
their  different  isomeric  forms,  we  have  special  cases  of  isomerism  for  definite 
groups  of  substances. 

xC3H7 

For  example,  in  the  compound,  N^-H     ,  the  monovalent  group  —  C3H7  may   be 

\H 

xCH3 
present  in  its  isomeric  forms,  i.e,  either  as  —  CH2  —  CH2  —  CH3  or  as  —  C^-H    .    Although 


there  is  considerable  resemblance  between  these  two  compounds,  their  different  con- 
stitutions are  manifested    in    certain  chemical  and  physical  properties.      The  following 

xCH3  /CH3 

compounds  are  also  metameric  isomerides  :   N^-GyB*  and  N^-CH3  ;  in  fact,  although  the 


percentage  compositions  and  molecular  magnitudes  are  the  same  in  both  cases,  the  sub- 
stituent  groups  of  the  ammonia  molecule  are  different  and  the  compounds  belong  to 
different  categories  —  disubstituted  and  trisubstituted  ammonias. 

PSEUDOISOMERISM,  TAUTOMERISM,  DESMOTROPY.  A  sub- 
stance sometimes  contains  atomic  groups  that  occupy  a  very  precarious 
(labile)  position,  since  they  exert  certain  influences  one  on  the  other  and  under 
certain  given  conditions  can  react  in  different  ways,  giving  now  one  new 
substance  and  now  another  ;  this  explains  how  it  is  that  some  compounds 
having  a  well-defined  chemical  character  can,  under  some  conditions,  behave 
like  substances  with  other  chemical  characters,  without  it  being  necessary  to 

II  2 


18 

assume  a  true  change  of  constitution.  Thus,  for  example,  some  of  the  deriva- 
tives of  cyanic  acid,  CN  •  OH,  behave  like  derivatives,  sometimes  of  the  formula 
N=C — OH  and  sometimes  of  the  formula  NH  =  C  =  O,  when  the  hydrogen 
atom  is  replaced  by  a  given  radicle.  The  same  is  the  case'  for  derivatives  of 
cyanamide,  N^?C— NH2,  and  of  carbodiimide,  NH  =  C=NH  ;  and  of  the 

two  non-nitrogenous  types,  — C(OH)  =  C— CO  —  and  — CO— CH— CO,  where 
a  hydrogen  atom  oscillates  between,  the  two  carbon  atoms.  These  compounds 
exist  usually  in  only  one  form,  the  more  stable  one,  but  in  the  derivatives 
this  stable  form,  simply  on  heating,  is  transformed  into  the  labile  one.  For 
this  phenomenon  Baeyer  proposed  the  name  pseudoisomerism,  and  others 
that  of  desmotropy. 

These  forms  can  be  distinguished  sometimes  by  chemical  reactions,  but 
more  generally  by  the  molecular  refraction,  dielectric  constant,  magnetic 
rotation,  electrical  conductivity,  &c. 

In  various  substances,  where  several  hydroxyls  are  present  in  more  or  less 
adjacent  positions,  there  is  often  a  tendency  for  intramolecular  transformation 
to  take  place  with  condensation  of  two  of  these  groups  and  separation  of  a 
molecule  of  water,  giving  rise  to  isomeric  anhydrides,  ethers,  ketones,  or 
alcohols,  &c.  In  their  turn,  these  derivatives  or  isomerides,  which  can  be 
transformed  one  into  the  other,  give  rise  to  distinct  classes  of  compounds, 
and  this  species  of  isomerism  is  called  tautomerism. 

STEREOISOMERISM  OR  ISOMERISM  IN  SPACE.  We  have  already  seen  that, 
by  the  tetra valency  of  carbon  and  its  property  of  uniting  with  itself  to  form  various  chains, 
it  is  possible,  in  certain  cases,  to  explain  the  existence  of  isomerides,  which  have  the  same 
percentage  composition  and  molecular  magnitude,  but  different  groupings  within  the 
molecules.  Many  cases  of  isomerism,  foreseen  from  theoretical  considerations,  have 
since  been  actually  met  with  and  different  isomerides  have  been  prepared  artificially 
after  their  existence  had  been  foretold. 

For  a  long  time,  however,  certain  compounds  were  known  for  which  ordinary  isomerism 
did  not  provide  any  explanation  j  among  these  the  most  important,  from  an  historical 
point  of  view  also,  are  the  four  dihydroxysuccinic  acids  (tartaric  acids),  of  which  two 
(ordinary  tartaric  acid  and  racemic  acid)  were  studied  by  Berzelius  as  long  ago  as  1830. 
To  these  must  be  added  laevo  -rotatory  tartaric  acid  and  meso tartaric  acid  discovered  by 
Pasteur.  All  these  compounds  have  the  same  internal  grouping  of  the  atoms,  although 
they  are  isomerides  ;  it  is  not  possible  to  distinguish  between  them  by  chemical  reactions, 
but  they  can  be  clearly  differentiated  by  their  physical  behaviour  :  they  form  hemihedral, 
i.e.  symmetrical,  but  non-superposable  crystals  (related  as  an  object  to  its  image  in  a 
mirror) :  they  have,  too,  different  actions  on  polarised  light,  the  plane  of  which  is  turned 
to  the  right  by  some  and  to  the  left  by  others.  These  acids  are  hence  known  as  physical 
or  optical  isomerides. 

Pasteur  attempted  to  explain  this  isomerism  by  supposing  the  atomic  groups  to  be 
arranged  unsymmetrically  in  the  molecule,  in  some  cases  in  a  dextro-rotatory  spiral 
and  in  others  in  a  laevo -rotatory  spiral,  or  arranged  at  the  vertices  of  an  irregular  tetra- 
hedron. 

When  other  similar  isomerides — the  lactic  acids — had  been  discovered,  J.  Wislicenus, 
in  1873,  suggested  that  isomerism  of  this  kind  could  be  explained  only  by  regarding  the 
groups  or  atoms  of  these  compounds  as  arranged  in  space  so  as  to  form  distinct  configurations. 

This  isomerism  in  space  (stereoisomerism)  was  explained  by  van  't  Hoff  and  Le  Bel 
(1874),  independently,  by  means  of  the  hypothesis  of  the  asymmetric  carbon  atom.  The 
starting-point  of  this  hypothesis  was  Kekule's  idea  (1867)  of  regarding,  for  the  sake  of 
convenience,  the  carbon  atom  as  situated  at  the  centre  of  a  regular  tetrahedron,  and  its 
four  affinities  as  directed  towards  the  four  vertices,  i.e.  arranged  homogeneously  in  space 
(Figs.  22,  23).  If  these  affinities  are  satisfied  at  the  vertices  by  monovalent  atoms  or 
atomic  groups,  the  following  cases  present  themselves  :  no  isomerism  is  possible  in  the  com- 
pounds Ca3  b,  Caz  bz,  Caz  be,  and  Ca  bz  c,  where  a,  b,  and  c  indicate  either  atoms  other  than 
carbon  or  groups  of  atoms  (I,  H,  OH,  &c.) ;  the  compound  CH2I2  exists  in  only  one  form, 
and  if  we  put  the  four  atoms  (H2  and  I2)  at  tiie  apices  of  the  carbon  tetrahedion,  no  matter 


STEREOISOMERISM 


19 


how  their  positions  may  be  changed,  it  is  not  possible  to  find  two  different,  i.e.  non-super  - 
posable  arrangements.  If,  however,  the  four  groups  or  atoms  combined  with  the  carbon 
atom  are  all  different,  e.g.  Cabcd,  two  isomerides  are  possible  and  in  this  case  the  carbon 
atom  is  termed  asymmetric;  in  fact,  if  these  atoms  or  groups  are  arranged,  in  one  case, 
so  that  the  circle  a,  b,  c  has  a  sense  opposite  to  that  in  which  the  hands  of  a  clock  move 
(Fig.  24,  I)  (called,  therefore,  dextro-rotatory  isomerides,  and  indicated  by  d-  or  by  the 
8tgn  +)  and,  in  the  other,  in  the  opposite  sense  (Fig.  25  II)  (termed  Icevo-rotatory  isomerides, 
like  levulose  and  indicated  by  I-  or  — ),  two  non-congruent  configurations  are  obtained  ; 
these  cannot  be  superposed,  one  on  the  other,  so  that  the  same  groups  occupy  the  same 


positions  in  the  two  cases.  These  two  figures  represent  two  different  isomerides  and 
are  related  in  the  same  way  as  an  object  to  its  mirror-image  or  as  the  left  hand  to  the 
right.  This  isomerism  is  called  enantiomorphism. 

These  two  different  arrangements  of  the  atoms  round  the  asymmetric  carbon  atom 
also  explain  how  it  is  that  when  polarised  light  traverses  these  molecules,  its  plane 
of  polarisation  is  rotated,  in  one  case  to  the  right  and  in  the  other  to  the  left.  Van  't 
Hoff  and  Le  Bel  pushed  their  deductions  still  further,  and  showed  that  the  dextro-optical 
deviation  should  be  numerically  equal  to  the  laevo  -optical  deviation  of  the  corresponding 
isomeride.  This  has  been  confirmed  practically,  and  it  also  follows  that  when  a  pair  of 
such  isomerides  are  mixed  in  equal  proportions,  there  should  result  an  optically  neutral 
mixture,  thus  giving  rise  to  a  special  inactive  or  racemic  isomeride.  A  substance  with 
only  one  asymmetric  carbon  atom  always  gives  three  stereoisomerides  (for  example,  three 
lactic  acids). 

It  has  also  been  deduced  theoretically  and  proved  practically  that  all  optically  active 
compounds  contain  at  least  one  asymmetric  carbon  atom,1  although  not  all  compounds 
containing  asymmetric  carbon  atoms  are  optically  active,  since  the  molecules  may  contain 
groups  which  neutralise  each  other's  activity. 

Many  examples  illustrating  these  principles  will  be  discussed  later  in  the  special  part 
of  this  book  ;  meanwhile  mention  may  be  made  of  the  most  important  of  these  com- 


FIG.  27. 


FIG.  28. 


pounds  :  leucine,  asparagine,  coniine,  the  lactic  acids  (hydroxypropionic  acids),  &c.,  which 
contain  one  asymmetric  carbon  atom  and  give,  in  each  case,  three  stereoisomerides. 

These  cases  of  stereoisomerism,  and  those  which  follow,  will  be  understood  more 
easily  if  studied  by  means  of  cardboard  tetrahedra  with  differently  coloured  vertices. 

When  the  substance  contains  two  asymmetric  carbon  atoms,  the  number  of  stereo- 
isomerides increases  as  follows  : 

If  we  take  two  tetrahedra  like  that  shown  in  Fig.  26  I  and  Fig.  28  II,  representing 
two  similar  molecules  containing  only  one  asymmetric  carbon  atom  in  which  the  groups 

1  Or  else  an  asymmetric  atom  of  nitrogen  (see  later)  or  sulphur,  tin,  &c.  The  exceptions  to  this  rule  are  very 
rare  and  uncertain,  one  of  the  cases  most  discussed  during  recent  times  (1909-1910)  being  \-methylcyclohexylidene- 
1-acetic  acid,  which  does  not  appear  to  contain  an  asymmetric  carbon  atom,  but  is  optically  active. 


20 


ORGANIC    CHEMISTRY 


a,  6,  and  c,  satisfying  three  of  the^  valencies,  are  arranged  in  a  dextro-rotatory  sense,  and 
superpose  one  tetrahedron  on  the  other,  so  that  the  free  valencies  satisfy  one  another, 
there  results  a  new  isomeride,  i.e.  a  molecule  with  two  dextro-rotatory  asymmetric  carbon 
atoms,  as  shown  in  Figs.  27  and  29. 1 

If  we  join  two  Isevorotatory  carbon  atoms  (Fig.  28  II),  that  is,  the  mirror  images 
of  Fig.  26  I,  a  laevo -rotatory  isomeride  (Fig.  30  II)  is  obtained. 

Finally,  if  one  dextro-rotatory  (Fig.  26  I)  and  one  Isevo -rotatory  asymmetric  carbon 
atom  (Fig.  28  II)  are  united,  a  third  stereoisomeride  is  obtained,  which  is  permanently 
optically  inactive  (Fig.  31  III),  the  effect  produced  on  polarised  light  by  one  asymmetric 
carbon  atom  being  destroyed  by  the  effect  of  the  other. 


FIG.  29. 


FIG.  30. 


In  order  to  understand  these  stereochemical  speculations  better,  we  will  apply  them 
to  the  isomerism  of  tartaric  acid,  which  has  the  formula  C4H606,  and  contains  two  asym- 
metric carbon  atoms  (marked  with  asterisks)  to  which  are  joined  the  groups  OH,  C02H, 
andH: 

CO2H 


CO2H 

If,  for  the  letters  a,  6,  and  c  of  the  tetrahedra  considered  above,  we  substitute  the 
groups  OH,  C02H,  and  H,  and  if  the  tetrahedron  of  Fig.  26  I  (which  we  will  call  +  A) 

be  represented  as   if    projected  on  to  a  plane,  thus:    a  —  C  —  c  or  OH  —  C  —  H     (dextro- 

\1  \     I 

6  XC02H 

I  I 

rotatory),  and  that  of  Fig.  28  II  (  —  A),  thus  :    c  —  C  —  a  or  H  —  C  —  OH  (Isevo  -rotatory), 

I/  I       / 

6  C02H 

we  arrive  at  the  following  stereoisomerides  of  tartaric  acid  : 

I.  By  joining  two  +  A  atoms,  we  get  d-tartaric  acid  (Fig.  29  or  32  I). 

II.  By  joining  two  -  A  atoms,  we  get  Z-tartaric  acid  (Fig.  30  or  32  II). 

III.  By  joining  one   +  A  atom  with  one  —A  atom,  we  have  the  permanently  inactive 
mesotartaric  acid  (t-tartaric  acid),  as  can  be  seen  in  Fig.  31  III,  or  32  III. 

IV.  By  mixing,  mechanically,  equal  parts  of  acid  I  (  +  )  and  II  (  -  ),  there  results 
racemic  acid,  apparently  inactive,  but  from  which,  by  mechanical  means  (by  hand  with 
the  aid  of  a  lens),  the  two  forms  of  crystals  can  be  separated. 

It  is  often  assumed  that  the  two  asymmetric  carbon  atoms  can  rotate  independently, 
on  the  common  axis  joining  them,  so  that  if  the  groups  of  one  asymmetric  carbon  atom 
exert  an  attraction  or  influence  on  those  of  the  other,  a  most  favourable  position  could 
be  attained,  a  chemical  reaction  being  sometimes  possible  between  one  group  and  another 

1  Looking  at  the  order  in  which  the  letters  a,  b,  and  c  come  in  the  two  asymmetric  carbon  atoms,  it  would  seem 
that  these  are  not  dextro-rotatory,  but  this  is  because  the  upper  carbon  atom  has  been  turned  through  ISO"  from 
its  position  m  Fig.  26  ,  if  itn  base  is  brought  down,  its  identity  with  the  other  dextro-rotatory  atom  becomes 
evident. 


ALLOISOMERISM 


21 


with  separation  of,  say,  water  and  loss  of  the  freedom  of  rotation  ;  to  the  new  isomerism 
thus  created  we  shall  refer  shortly. 

STEREOISOMERISM  IN  DERIVATIVES  WITH  DOUBLY  LINKED  CARBON 
(ALLOISOMERISM).  By  means  of  the  tetrahedra,  we  can  show  a  double  linking  between 
two  carbon  atoms  by  arranging  one  side  of  one  tetrahedron  (carbon  atom)  in][contact 
with  a  side  of  the  other  (Fig.  33). 

With  such  an  arrangement,  even  without  asymmetric  carbon  atoms,  isomerism  is 

possible.     In  fact,   a  compound  />C=C<\  forms  the  following  isomerides  :     (1)  that 


CO,H 

CO,H  CT>,H 

H-'C-OH  HO-*C_H 

BO-'C-B  H-'C.OH 

co,n  CO,H 

I  II 

FIG.  32. 


CO,H 
•H-'C-OH 
H-'C-OH 

CO,H 

III 


FIG.  33. 


shown  in  Fig.  34,  where  the  two  similar  atoms  or  groups  of  atoms,  e.g.  a  and  a,  although. 

a— C— b 
united  to  two  different  carbon  atoms,  occupy  adjacent  positions :         ||       ,  or  ci's-posi'tions 

a—C—b 

(cis-isomerism)  ;  such  a  molecule  exhibits  plane-symmetry,  the  two  pairs  of  similar  groups 
lying  to  the  left  and  right,  respectively,  of  the  perpendicular  plane  containing  the  common 
side  (double  linking)  ;  (2)  that  shown  in  Fig.  35,  where  two  similar  groups  occupy  non- 

a— C— 6 
adjacent  or  diagonally  opposite  or  trans-positions  ,  this  form  exhibiting  centro- 

b—C—a 


Similarly,  a  compound  of  the  type,    ^>C=C<%,  forms  two  isomerides,  the  cis-form, 

a—C—b  a—C—b 

,  and  the  trans-torm, 
a — C — c  c — C — a 


_  HC  C02H 
~  HC.CO.jH 


__  HO,C.CH 

HO.C02H 


FIG.  36. 


FIG.  37. 


FIG.  38. 


The  best  illustration  of  this  type  of  isomerism  is  afforded  by  the  two  isomerides  : 
maleic  acid  (cis-form,  Fig.  36)  and  fumaric  acid  (trans-iorm,  Fig.  37). 

From  these  figures  it  is  seen  that  the  cis-form,  maleic  acid,  should  lend  itself  to  the 
ready  formation  of  anhydrides  (condensation  of  two  molecules  or  acid  groups  with  separa- 
tion of  one  molecule  of  water),  since  the  two  acid  groups,  CO2H,  are  very  near  to  one 
another,  and  it  is,  indeed,  found  that  maleic  acid  easily  gives  an  anhydride  with  separation 
of  one  molecule  of  water  (Fig.  38),  whilst  no  anhydride  of  fumaric  acid  is  known. 

Isomerism  of  this  kind  is  exhibited  by  various  substances,  e.g.  crotonic  and  isocrotonic 
acids  (CH3  •  CH  :  CH •  COOH);  metacommand  citraconic  acids  [CH3  •  C(COOH ) :  CH •  COOH], 
&c. 

Baeyer  found  that  cases  of  isomerism  similar  to  those  just  described  occur  also  with 
cyclic  compounds  (see  Part  III),  i.e.  closed-chain  compounds  with  simple  linkings  between 


22  ORGANIC    CHEMISTRY 

the  carbon  atoms.  He  distinguishes  with  the  sign  T  compounds  containing  true  asym- 
metric carbon  (absolute  asymmetry),  adding  the  sign  +  or  —  if  the  compound  is  optically 
active  ;  while  he  gives  the  name  relative  asymmetry  to  that  shown  by  compounds  with 
doubly  linked  carbon  atoms  (alloisomerism)  or  by  cyclic  compounds  with  simple  linkings, 
the  term  cis  or  trans  being  added  to  the  JP.  Thus,  to  the  name  tartaric  acid  would  be 
added  the  sign  F  +  or  T  —  according  as  the  acid  is  dextro-  or  Isevo -rotatory,  and  to 
the  name  maleic  acid  _Tcis,  to  fumaric  acid  J7"3"5,  &c. 

STEREOISOMERISM  OF  NITROGEN.  Le  Bel  attempted  to  explain  the  isomerism 
of  certain  nitrogen  compounds  (e.g.  methyl-ethyl-propyl-isobutyl-ammonium  chloride) 
by  assuming  absolute  asymmetry  for  the  nitrogen  atom.  A  more  plausible  explanation 
seems,  however,  to  be  afforded  by  the  idea  of  relative  asymmetry  of  the  nitrogen,  analogous 
to  that  of  carbon  atoms  when  united  by  double  linking  ;  in  this  way  V.  Meyer,  Hantzsch, 
Werner,  and  others  easily  explained  the  isomerism  of  the  oximes,  hydroxamic  acids, 

Cab 
phenylhydrazones,  &c.    In  general,  a  substance  of  the  constitution  ||         should  give  two 

Nc 
isomerides  which  can  be  represented  as  shown  in  Fig.  39  ;  the  s^n-series  (Fig.  39   I)  and 

the  anti-series  (Fig.  39  II). 
*.  ^^^^  These  investigators  also  studied  those  cases 

of  isomerism  in  which  the  nitrogen  behaves  as 

(II)  s"~&  a  Pentavalen*  element. 

SEPARATION  AND  TRANSFORM  A- 
TION  OF  STEREOISOMERIDES.  Stereo- 
isomerides  and,  in  general,  compounds  contain- 
ing asymmetric  carbon  atoms,  when  prepared 

p .  a— C  — b        artificially   in    the   laboratory  from   inactive 

it  ||  substances,  are  inactive,  the  racemic  configura- 

^ — jj  N — c        tion,  composed   of   a    mixture   of  the  optical 

YIG.  39.  antipodes  in  equal    quantities,  being  formed. 

When,  however,  these  substances  are  elabo- 
rated in  the  animal  or  vegetable  organism,  they  are  usually  optically  active. 

The  transformation  of  one  of  these  optical  antipodes  into  the  other  corresponding  with 
it  may  sometimes  be  effected  by  passing  through  halogen  derivatives,  separation  of  the 
halogen  from  which  results  in  the  formation  of  the  isomeride  of  opposite  optical  activity. 
The  separation  of  the  antipodes,  or  of  one  of  them,  from  the  racemic  isomeride  was 
carried  out  by  Pasteur  (1848)  in  various  ways.  The  following  are  the  methods  used  at 
the  present  time  : 

(1)  By  fractional  crystallisation  (see  above)  of  the  racemic  isomerides  or  of  some  of 
their  salts  at  various  temperatures  and  from  various  solvents,  the  antipodes  can  be  sepa- 
rated directly  or  else  they  crystallise  in  hemihedral  forms  which  can  be  readily  separated. 
For  some  substances,  it  is  convenient  to  prepare  compounds  with  alkaloids  (optically  active 
basic  compounds,  e.g.  strychnine,  cinchonine,  &c.),  which,  even  when  they  do  not  form 
well-defined  hemihedral  crystals,  can  be  easily  separated  by  fractional  crystallisation. 

(2)  By  means  of  enzyme  action  (maltase,  emulsin,  &c.  ;  see  section  on  Fermentation), 
Fischer  succeeded  in  resolving    certain    racemic    glucosides.     Much  earlier  than   this, 
Pasteur  discovered  that  certain  bacteria  or  moulds  (Penicillium  glaucum,  &c.)  are  capable 
of  developing  in  a  solution  of  the  racemic  substance  at  the  expense  of  one  of  the  optical 
antipodes,  the  other  being  left  unchanged.     This  phenomenon  is  explained  by  the  fact 
that  bacteria  owe  their  activity  to  certain  substances  which  they  produce  (enzymes), 
and  which  are  optically  active  and  behave  analogously  to  optically  active  solvents. 
Indeed,  in  many  cases,  stereoisomeric  antipodes  are  separated  by  virtue  of  their  different 
solubilities  in  an  optically  active  solvent. 

(3)  With  certain  racemic  compounds,  the  antipodes  are  separated  by  taking  advantage 
of  their  different  velocities  of  esterification  in  presence  of  an  optically  active  alcohol  ; 
e.g.  for  racemic  mandelic  acid,  menthol  (which  is  an  active  alcohol)  is  used.     For  inactive 
alcohols,  the  velocity  of  esterification  is  the  same  for  the  two  antipodes  composing  the 
racemic  compound. 

(4)  When  an  optically  active  substance  is  heated  within  certain  definite  limits  of 
temperature  (transformation  point,  see  vol.  i,  p.  190),  it  is  often  converted,  to  the  extent 


HOMOLOGY    AND    ISOLOGY  23 

of  one-half,  into  the  oppositely  active  isomeride,  so  that  an  inactive  mixture  (racemic 
compound)  is  obtained  ;  this  takes  place  readily,  for  example,  with  the  lactic  acids. 
Above  the  transformation  point  the  racemic  substance  may  form  inseparable  mixed 
crystals  (see  vol.  i,  p.  Ill),  the  substance  being  then  called  pseudo-racemic.  On  the  other 
hand,  it  has  been  shown  that,  with  certain  halogenated  compounds,  the  transformation 
occurs  even  at  ordinary  temperatures,  but  with  a  minimum  velocity  ;  thus,  with  isobutyl 
bromopropionate,  about  three  years  is  required. 

(5)  R.  Stoermer  (1909)  found  that  the  more  stable  form  with  the  higher  melting-point 
is  often  converted  into  the  more  labile  form  by  means  of  the  ultra-violet  rays. 

HOMOLOGY  AND   ISOLOGY 

Turning  to  the  more  simple  compounds,  those  formed  from  only  carbon 
and  hydrogen,  we  can  easily  see  what  procedure  is  necessary  to  arrive  at 
those  containing  longer  and  more  complex  chains  of  carbon  atoms.  If  we 
start  from  the  most  simple  compound,  methane  (or  marsh  gas),  CH4,  we  can 
substitute  an  atom  of  hydrogen  in  it  by  other  elements  or  even  condense  two 
of  the  monovalent  CH3  residues  into  one  compound,  CH3'CH3,  thus  obtaining 
ethane  (C2H6).  But  in  this  compound  we  can  also  replace  an  atom  of  hydrogen 
by  another  — CH3  residue,  forming  propane,  CH3— CH2 — CH3  or  C3H8,  and 
by  continuing  this  process  we  arrive  at  butane,  CH3 — CH2 — CH2 — CH3,  i.e. 
C4H,  , ;  pentane,  C5H12 ;  hexane,  C6H14,  &c. 

All  the  compounds  of  this  series  have  analogous  structures  and  have  also 
many  analogous  chemical  and  physical  properties  ;  such  a  series  is  called  a 
homologous  series. 

This  series  of  the  derivatives  of  methane  can  be  represented  by  the  general 
formula  CwH2w+2,  each  term  being  the  higher  or  lower  homologue  of  the  pre- 
ceding or  following  term  and  differing  from  it  by  having  one  CH2  complex 
more  or  less.  If  in  all  the  simple  compounds  of  this  homologous  series  of 
methane  we  replace  successively  one  hydrogen  atom  of  the  CH3  group  by  the 
hydroxyl  residue  OH  (characteristic  of  the  alcohols)  we  obtain  a  homologous 
series  of  alcohols :  CH3OH,  methyl  alcohol;  C2H5OH,  ethyl  alcohol,  <fec.,  and 
similar  series  can  be  obtained  of  aldehydes,  acids,  chloro-derivatives,  &c. 

The  homologous  compounds  of  each  of  these  series  differ  always  by  CH2 
or  by  a  multiple  of  it. 

There  are  also  other  series  with  chains  containing  double  linkings  (i.e. 
compounds  not  completely  saturated),  and  these  unsaturated  series  are  termed 
isologous  with  respect  to  the  first,  and,  for  an  equal  number  of  carbon  atoms, 
they  contain  less  hydrogen  (CWH2W  or  even  CnH2w_2). 

Thus,  ethane  is  isologous  to  the  two-carbon-atom  compounds  of  the 
unsaturated  series,  CH2=CH2  (ethylene)  and  CH=CH  (acetylene),  &c. 

Homology  is  determined  by  the  tetra valency  of  carbon,  and  in  consequence 
the  total  number  of  hydrogen  atoms  in  these  compounds  (hydrocarbons)  is 
always  even,  i.e.  divisible  by  two,  and,  if  any  of  the  hydrogen  atoms 
are  replaced  by  other  elements,  the  sum  of  the  atoms  with  odd  valencies 
(Cl,  P,  N,  As),  and  of  the  remaining  hydrogen  atoms  should  always  give  an 
even  number. 

PHYSICAL  PROPERTIES  OF   ORGANIC  SUBSTANCES  IN  RELATION 
TO   COMPOSITION   AND    CHEMICAL   CONSTITUTION 

In  many  cases,  certain  physical  properties  are  either  common  to  whole 
groups  of  homologous  or  isomeric  substances,  or  else  vary  gradually  with 
change  of  chemical  composition.  So  that  the  physical  properties  often  con- 
tribute to  the  establishment  of  the  true  chemical  constitutions  of  organic 
substances. 


24  ORGANIC    CHEMISTRY 

CRYSTALLINE  FORM.  The  crystalline  form  of  an  organic  compound  is  of  con- 
siderable importance,  since  it  often  serves  to  distinguish  clearly  and  accurately  between 
two  compounds.  Two  isomeric  substances  have  often  different  crystalline  forms. 

There  are,  however,  numerous  cases  of  dimorphism  or  polymorphism  (see  vol.  i),  one 
of  the  forms  always  being  more  stable  than  the  others. 

We  have  already  considered  the  relations  existing  between  the  crystalline  form  and 
chemical  constitution  in  those  stereoisomerides  differing  only  by  the  enantiomorphism 
of  their  crystals. 

P.  Groth  has  discovered  also  the  law  of  morpTiotropy,  according  to  which  a  regular 
change  is  produced  in  the  crystalline  form  of  compounds  by  gradual  substitution  with 
new  atoms  or  groups. 

The  relations  between  the  crystalline  forms  and  the  chemical  constitutions  of  sub- 
stances have  as  yet,  however,  been  little  studied. 

SOLUBILITY.  The  hydrocarbons  and  their  substitution  derivatives  are  but  slightly 
or  not  at  all  soluble  in  water,  but  are  almost  all  soluble  in  ether  and  in  alcohol.  Of  the 
alcohols,  the  acids,  and  the  aldehydes,  the  first  terms  of  every  homologous  series  are 
soluble  in  water,  the  solubility  gradually  decreasing  as  the  number  of  carbon  atoms  in 
the  molecule  increases  ;  these  compounds  are,  however,  relatively  readily  soluble  in 
alcohol  or  ether.  The  polyhydric  alcohols  (glycerol,  mannitol,  &c.),  are,  however,  soluble 
in  water,  but  not  in  ether. 

The  compounds  of  the  aromatic  series  are,  in  general,  rather  less  soluble  in  alcohol 
and  in  water  than  the  corresponding  compounds  of  the  fatty  series. 

In  contact  with  two  solvents  which  do  not  mix  (see  vol.  i,  p.  90),  a  substance  dis- 
solves in  them  both  in  a  constant  ratio,  independent  of  the  relative  volumes  of  the  two 
solvents,  but  depending  on  the  concentration  and  on  the  temperature  ;  thus,  in  separating 
by  means  of  ether  a  compound  dissolved  in  water,  a  better  and  more  rapid  result  is 
obtained  by  shaking  many  times  with  a  little  ether  each  time  than  by  using  fewer,  but 
larger,  quantities  of  ether. 

Of  two  isomerides,  that  with  the  lower  melting-point  is  the  more  soluble. 
SPECIFIC  GRAVITY.  Isomeric  compounds  have  different  specific  gravities,  but 
with  the  normal  hydrocarbons  (C,,H2,(_|_2)>  the  values  approach  one  another  as  the  number 
of  carbon  atoms  increases  :  at  about  C^H^  and  for  higher  terms,  the  specific  gravity 
becomes  about  0-78.  The  specific  gravity  of  the  monobasic  fatty  acids  is  greater  than 
1  for  the  first  terms  of  the  series,  but  it  diminishes  with  augmentation  of  the  number  of 
carbon  atoms  in  the  molecule. 

MOLECULAR  VOLUME.  It  was  thought  for  many  years  that  certain  important 
rules  could  be  deduced  from  the  molecular  volumes  of  organic  compounds,  that  is,  from 
the  quotients,  M/P,  obtained  by  dividing  the  molecular  weights  (M)  by  the  specific 
gravities  (P), 

In  1842  Kopp  had  found  that,  for  liquids  at  the  boiling-point,  the  molecular  volume 
is  very  approximately  equal  to  the  sum  of  the  atomic  volumes  of  the  component  elements. 
For  homologous  compounds,  the  molecular  volume  increases  by  about  22  for  every  added 
CH2  group.  More  recent  studies  (Lessen,  R.  Schiff,  Horstmann,  Traube,  &c.)  show, 
however,  that  these  regularities  are  only  relative  and  that  isomeric  compounds  do  not 
possess  equal  molecular  volumes.  In  unsaturated  series,  every  double  linking  increases  the 
molecular  volume  and,  with  closed-chain  compounds,  the  molecular  volume  is  less  than 
those  of  the  corresponding  open-chain  compounds  with  double  linkings.  So  that,  in 
general,  the  molecular  volume  depends  not  only  on  additive  factors  (e.g.  the  sum  of  the 
atomic  volumes),  but  also  on  constitutive  factors  (different  linkings  between  the  carbon 
atoms). 

MELTING-POINT.  Of  two  isomerides,  that  with  the  more  symmetrical  structure 
has  the  higher  melting-point.  The  members  of  a  series  have  varying  melting-points, 
those  with  odd  numbers  of  carbon  atoms  having  lower  melting-points  than  those  imme- 
diately below  them  with  even  numbers.  There  are,  in  addition,  other  less  important 
rules,  but  all  present  exceptions.  A  mixture  of  two  substances,  in  suitable  proportions, 
often  has  a  melting-point  lower  than  that  of  either  of  the  components. 

BOILING-POINT.  In  compounds  of  the  same  series,  the  boiling-point  rises  with 
increase  of  molecular  weight,  the  amount  of  the  increase  being  about  20°  per  CH2  in  the 
methyl  alcohol  or  formic  acid  series  and  about  30°  for  benzene  derivatives  with  methyl 


THERMAL    RELATIONS 


25 


groups  in  the  nucleus.  The  boiling-points  of  isologous  hydrocarbons,  that  is,  those  of 
the  same  number  of  carbon  atoms  but  of  different  series  (derivatives  of  methane,  ethylene, 
and  acetylene)  are  very  close  to  one  another. 

Of  the  isomeric  compounds  of  the  aliphatic  series,  the  normal  one  boils  at  the  highest 
temperature  and  the  boiling-point  is  increasingly  lowered  by  increase  in  the  branchings. 

The  substitution  of  hydrogen  by  halogens  and  by  hydroxyl  groups  raises  the  boiling- 
point.  The  ethers  boil  at  lower  temperatures  than  the  corresponding  isomeric  alcohols. 

HEAT  OF  COMBUSTION  AND  HEAT  OF  FORMATION  FROM  THE  ELEMENTS 
(see  vol.  i,  pp.  60,  109,  372).  The  Hess-Berthelot  law  states  that  the  difference  between 
the  heats  of  combustion  of  two  equivalent  chemical  systems  is  equal  to  the  heat  developed  in  the 
transformation  of  one  system  into  the  other,  that  is,  is  equal  to  the  heat  of  formation  from 
the  elements  of  this  latter.  In  general,  we  can  hence  calculate  the  heat  of  formation  from 
its  elements  of  an  organic  compound  by  subtracting  its  heat  of  combustion  from  the  sum 
of  the  heats  of  combustion  of  the  elements  composing  it.  As  an  example  :  the  heat  of 
combustion  of  methane,  CH4,  at  constant  volume  is  211,900  cals.  ;  the  heat  of  combustion 
of  carbon  (C  +  02  =  C02)  being  97,000  cals.  and  that  of  hydrogen  (H2  +  O '=  H20) 
68,400  cals.,  the  complete  combustion  of  methane  is  given  by  the  following  equation  : 
CH4  +  2O2  =  C02  +  2H2O  =  97,000  +  (2  x  68,400)  =  233,800  cals.,  the  sum  of  the 
heats  of  combustion  of  the  component  elements  of  methane.  The  heat  of  formation  of 
methane  will  then  be  given  by  :  233,800  -  211,900  =  21,900  cals.,  which  also  represents 
the  heat  necessary  to  resolve  methane  into  its  elements  in  order  to  initiate  its  combustion. 
The  heat  of  combustion  of  ethyl  alcohol  being  340,000  cals.,  that  of  acetic  acid  210,000, 
and  that  of  ethyl  acetate  554,000,  the  heat  of  formation  of  the  last  named  from  the  first 
two  will  be  :  340,OQO  +  210,000  -  554,000  =  -  4000  cals. 

In  the  analogous  paraffin  and  olefine  series,  a  difference  of  CH2  corresponds  with  a 
variation  of  150,000-160,000  cals.  in  the  molecular  heat  of  combustion. 

The  heats  of  combustion  of  isomeric  compounds  are  equal,  if  they  are  chemically 
similar,  for  example,  methyl  acetate  (CH3-CO2CH3)  and  ethyl  formate  (H'C02C2H5), 
but  different  if  the  compounds  are  of  different  molecular  character  (for  example,  allyl 
alcohol,  CH2  :  CH-CH2-OH,  and  acetone,  CH3-CO-CH3),  compounds  with  multiple 
linking  in  the  fatty  series  having  higher  heats  of  combustion  than  the  corresponding 
cyclic  isomerides. 

These  calculations  are  also  of  importance  for  the  evaluation  of  the  energy  produced  in 
organisms  by  the  transformations  of  various  foods  (see  also  later  in  the  section  on 
Explosives1). 

HEAT  OF  NEUTRALISATION.  With  the  organic  acids  this  is  the  same  for  all, 
namely,  13,700  cals.  (see  vol.  i,  p.  97),  as  long  as  the  resulting  salts  are  not  decomposed 
by  water  ;  with  the  phenols  (cyclic  compounds  containing  OH)  the  heat  of  neutralisation 
is  about  one-half  the  above  value,  or  more  if  the  acid  character  is  intensified  by  the 
presence  of  the  NO2  group  ;  with  the  alcohols  it  is  almost  zero. 

1  The  following  are  the  heats  of  formation  from  the  elements  of  certain  organic  compounds,  expressed  in  large 
calories  per  gramme-molecule : 

Naphthalene,  C10H8 :  solid     .         .         .  -42    Cals. 

Nitronaphthalene,  C10H,NO2  :  solid         .  —14-7 

Dinitronaphthalene,  C10H6(NO2)i  :  solid  —   5-7 
Trinitronaphthalene,  C10H6(NOji)3    solid.         3-3 

Acetylene,  C2H2  :  gas    ....  —61-4 

Ethylene  C2H  4  :  gas      .      '..'*".         .  —15-4 

Benzene, C,H,  :  gas       .          .         ....        .  —10-2 

Nitrobenzene,  C,H6N02  :  liquid      .          .         4'2 
Dinitrobenzene,  C,H4(NO2)2  :  solid          .       12-7 

Mannitol,  CeH140«  :  solid       .          .          .  320 

Nitromannitol,  CeH8N,O18  :  solid    .          .  179' 1 

Mercury  fulminate,  C2N2Os,Hg  :  solid       .  —62-9 
Anthracene,  C14H10  :  solid      .         . 


Methyl  alcohol,  CHSOH  :  liquid       .         .       62  Cals. 

Ethyl  alcohol,  C,H5OH  :  liquid        .         .       70-5  „ 

Phenol,  C,H6OH :  liquid         .         .         .       34-5  „ 
Trinitrophenol  (picric  acid),C,H2OH(NO2), 

solid 49-1  „ 

Sodium  picrate,   C«H2ONa(NO,)8 :    solid    117-5  „ 

80-]  „ 

65-3  „ 

72  „ 

Glycerol,  C3H6(OH),  :  liquid  .          .          .     165-5  „ 

Trinitroglycerol,  C,H,(ONO2)3  :  liquid      .     196  ,, 
Cellulose  (cotton),  C6H10O5  :  solid  .         .     227 


Ammonium  picrate,  solid 
Ether,  (C8H.)2o{**suid; 


Nitrocellulose,  solid 


624-696-706 


-42-4 

and  the  heats  oj  combustion  of  various  organic  compounds  are  as  follow :  ethyl  alcohol,  340  cals. ;  methyl 
alcohol,  182-2  ;  mannitol,  727  ;  cellulose,  680  ;  terephthalic  acid,  771 ;  diphenyl,  1494  ;  cane  sugar,  1355  ;  acetic 
acid,  210 ;  benzole  acid,  772  ;  ethyl  acetate,  554  ;  urea,  152  ;  benzene,  779-8  ;  dihydrobeniene,  848  ;  tetra- 
hydrobenzene,  892 ;  toluene,  933  ;  hexane,  991-2  ;  methane,  211-9  ;  ethane,  370-4  ;  propane,  529-2 ;  trimethyl- 
methane,  687-2  ;  ethylene,  333-4  ;  propylene,  492-7  ;  trimethylene,  499-4  ;  isobutylene,  650-6  ;  methyl  chloride, 
164-7  ;  ethyl  chloride,  321-9  ;  propyl  chloride,  480-2  ;  chloroform,  70-5  ;  dinitrobenzene  (o-,  m-,  and  p-),  about 
700 ;  trinitrobenzene,  666 — 681 ;  succinic  acid,  357  ;  azelaic  acid,  1141 ;  erucic  acid,  3297  ;  tribrassidinic  acid, 
10,236  ;  glucose,  674  ;  oxalic  acid,  60-2  ;  formic  acid,  62-8  ;  hydrocyanic  acid,  152-3  ;  naphthalene.  1233-6  ; 
phenol,  732  ;  pyrogallol,  639. 


26 


ORGANIC    CHEMISTRY 


OPTICAL  PROPERTIES.  (1)  Colour.  The  majority  of  organic  compounds  are 
colourless,  but  if  they  contain  iodine  or  the  nitro -group  or  doubly  linked  nitrogen  atoms 
( — N=N — ),  or  two  oxygen  atoms  directly  united,  they  are  generally  coloured,  especially 
in  the  aromatic  series. 

In  the  section  on  Dyes  are  given  detailed  illustrations  of  the  remarkable  relations 
between  the  chemical  constitution  of  organic  compounds  and  their  colour. 

(2)  Refraction.  This  is  the  deviation  produced  in  the  direction  of  a  ray  of  light 
(homogeneous  ;  for  example,  sodium  light)  on  passing  through  a  transparent  liquid,  and 
varies  with  the  substance.  The  index  of  refraction  n  varies  with  the  temperature,  and 
hence  with  the  specific  gravity  (d)  of  the  substance.  The  relation  between  these  two 

— 1     1 

R. 


values  which  gives  the  refraction  constant  R  (or  specific  refractivity)  is  : 
which  is  almost  independent  of  the  temperature. 


n2  +2.'  d 
By  multiplying  by  the  molecular 

n2— •  1      P 

weight  P,  the  molecular  refraction  is  obtained  :  M  =  -r ~  •  -5 ,  this  being  constant  for 

n    ~\~  £     d 

true  isomerides  and  changing  by  a  constant  amount  for  a  constant  change  in  the 
composition. 

The  molecular  refraction  of  a  compound  is  approximately  equal  to  the  sum  of  the 
elementary  atomic  refractions,  but  here  double  and  triple  linkings  have  an  influence,  so 
that  these  can  be  detected  in  an  organic  compound  by  means  of  the  refraction  (true  double 
linkings  of  the  aliphatic  series  are  often  distinguished  in  this  way  from  the  cyclic  linkings 
of  benzene). 

(3)  Polarised  Light.  Owing  to  the  importance  of  this  phenomenon  for  whole  groups 
of  organic  substances,  it  will  be  useful  to  recall  briefly  in  a  note  1  the  fundamental  ideas 
on  polarised  light. 


FIG.  40. 


1  The  luminous  waves  of  white  light  are  propagated  in  the  cosmic  ether  with  »  velocity  of  about  300,000  kilo- 
metres per  second,  and  there  are  physical  instruments  which  admit  of  the  measurement  of  the  time  required  for  a 

ray  of  light  to  traverse  a  few  metres ;  indeed,  Foucault  measured 

the  time  taken  by  light  to  pass  over  a  distance  of  120  metres. 
By  studying  the  phenomena  of  interference  of  light  rays,  it 

can  be  shown  that  the  vibrations  of  the  ether  in  them  are  not 

longitudinal,  i.e.  along  the  direction  of  propagation  of  the  ray, 

but  that  the  et'her  particles  vibrate  in  all  directions  in  a  plane 

perpendicular  to.  the  direction  of  the  ray  (a  transverse  section 

of  a  ray  is  shown  in  Fig.  40),  whilst  the  propagation  of  sound 

is  effected  by  means  of  longitudinal  vibrations  in  the  direction 

of  the  path  traversed  by  the  sound. 

A  ray  that  enters  a  liquid  or  a  non-crystalline  solid,  or  a  crystal  of  the  regular 
system  (cube  or  octahedron)  gives  only  one  refracted  ray ;  when  it  enters  a 
crystal  of  the  rhombohedral  system,  two  refracted  rays  are  formed,  one  extra- 
ordinary and  the  other  ordinary  ;  when  a  ray  enters  a  crystal  of  any  other  system, 
two  refracted  rays  are  formed,  but  these  rays  both  behave  likp  the  extraordinary 
ray,  and,  like  the  latter,  they  do  not  obey  the  laws  of  refraction,  according  to 
which  an  incident  ray,  perpendicular  to  a  medium  with  parallel  faces,  should  not 
be  deviated  or  refracted. 

If  a  ray  of  light,  J  i  (Fig.  41)  strikes  a  rhombohedral  crystal  of  Iceland  spar 
perpendicularly  to  the  face  ABCD,  the  ray  divides  into  two.  The  one,  ioO, 
continues  in  the  same  direction,  the  other,  ie,  is  deviated,  but  when  it  emerges 
from  the  crystal  assumes  the  direction  e  E,  parallel  to  the  original  direction.  The 
two  parallel  rays  leaving  the  crystal  have  equal  luminosities,  but  o  0  follows  the 


FIG.  41. 


O 


FIG.  42. 


FIG.  43. 


ordinary  laws  of  refraction  (vide 
supra)  and  is  called  the  ordinary 
ray,  whilst  the  other,  eE,  does  not 
obey  these  laws  and  is  termed  the 
extraordinary  ray. 

If  the  crystal  is  rotated  about 
the  incident  ray  Ji  as  an  imaginary 
axis,  the  position  of  the  ray  o  0  does 
not  change,  whilst  the  ray  e  E  moves 
in  the  sense  in  which  the  crystal  is 
rotated.  The  extraordinary  ray  i  E 

always  lies  in  the  plane  of  the  principal  axis  of  the  crystal  dbBD,  which  passes  through  the  principal  axis  of  the  crystal 
b  O  and  is  parallel  to  it.  These  two  rays  emerging  from  the  crystal  have,  however,  properties  different  from  those 
of  the  incident  ray  J  i  ;  in  fact,  if  either  of  the  two  refracted  rays  (eE  or  o  O)  is  passed  into  a  second  rhombohedron 
of  Iceland  spar,  two  new  rays  (double  refraction)  are  obtained,  but  the  intensities  of  the  two  rays  vary  according 
to  the  relative  positions  of  the  two  crystals.  Thus,  if  a  ray  emerging  from  the  first  crystal  passes  porpendiculaily 
into  the  second  crystal,  the  principal  section  cf  which  is  parallel  to  that  of  the  first,  no  double  refraction  is  observed, 
only  one  ray  leaving  the  second  crystal  (s  in  Fig.  42,  the  second  hypothetical  ray  n  not  being  visible  and  marked 
black  in  the  figure).  If,  however,  the  second  crystal  is  rotated  round  the  imaginary  axis,  o  O,  a  second  ray  (extia- 
ordinary)  suddenly  appears,  i.e.  double  refraction  takes  place,  and  whilst  the  luminosity  of  the  new  lay  increases, 


OPTICAL    ROTATION  27 

Those  organic  substances  are  called  optically  active  which  rotate  the  plane  of  polarised 
light.  Some  substances  are  optically  active  in  the  crystalline  state  (not  in  the  amorphous 
state  or  in  solution),  and  hence  the  action  on  polarised  light  is  due  in  these  cases  to  the 
peculiar  arrangement  of  the  molecules  ;  very  few  are  active  in  both  the  crystalline  and 
amorphous  states,  the  majority  exhibiting  activity  only  in  a  dissolved  condition  (sugars, 
&c.),  where  the  phenomenon  depends  on  the  arrangement  of  the  atoms  or  groups  of  atoms 
in  the  molecule.  This  holds  also  for  camphor  and  oil  of  turpentine,  which  are  active  even 
in  the  form  of  vapour. 

The  longer  the  layer  (I)  and  the  greater  the  concentration  of  the  solution  (p  =  grammes 
of  dissolved  substance  in  100  of  solution)  traversed  by  the  polarised  light,  the  greater 
will  be  the  rotation  of  the  plane  of  polarisation.  Referring  the  observed  rotation  a  to  a 
length  of  10  cm.  of  a  solution  containing  1  grm.  of  pure  substance  in  1  c.c.  (  =  pdjlOO, 
where  d  is  the  specific  gravity  of  the  solution),  we  get  the  specific  rotatory  power  of  the 
solution  for  the  yellow  sodium  light  (D  line  of  the  spectrum  x)  by  means  of  the  following 

1 00 

formula  :   fain  =  ; — ; — •      For    active    liquid    substances    examined    without    solvent, 
I'd-  p 

[a]D  =  -—— .     The  molecular  rotation  (for  a  molecular  weight  M)  is  given  by  :  [M]  =  • 

For  a  definite  solvent  and  given  concentration  and  temperature,  every  active  substance 
(and  such  are  almost  all  those  containing  asymmetric  carbon,  see  p.  26)  has  a  constant  and 
characteristic  specific  rotatory  power,  either  to  the  right  (  +)  or  to  the  left  (  -  ).  This 
varies  with  the  nature  and  degree  of  electrolytic  dissociation  of  the  solvent,  and  increases 
with  dilution  and  diminishes  with  rise  of  temperature  ;  for  purposes  of  comparison,  it  is 
usually  determined  at  20°,  and  is  then  indicated  thus  :  [a]  D.  By  repeating  the  determina- 
tions and  using  moderately  high  concentrations,  the  influence  due  to  the  solvent  is  deter- 
mined and,  on  subtracting  this,  the  true  specific  rotation  is  obtained.  Freshly  prepared 
solutions  of  certain  sugars  exhibit  the  phenomenon  of  muta-rotation,  which,  however, 
disappears  after  a  time  or  on  boiling  the  liquid,  the  normal  rotation  then  being 
given. 

This  important  property  of  optically  active  compounds  is  studied  by  means  of  special 
apparatus  termed  polarimeters,  which  are  used  particularly  in  the  analysis  of  sugars 
(and  hence  often  called  saccharimeters),  and  will  be  described  in  the  section  dealing  with 
this  group  of  substances. 

MAGNETIC  ROTATORY  POWER.  All  liquids  in  a  magnetic  field  produce  a  greater 
or  less  rotation  of  the  plane  of  polarised  light,  according  to  their  chemical  composition 
and  in  conformity  with  the  laws  governing  the  refractivity  of  light.  In  many  cases  the 
constitution  of  a  substance  has  been  determined  or  confirmed  by  determining  the 
molecular  magnetic  rotation. 

ELECTRICAL  CONDUCTIVITY.  We  must  refer  the  reader  to  the  detailed  treat- 
ment of  electrolytic  dissociation  and  the  theory  of  ions  in  vol.  i  (pp.  91  et  seq.),  as  the 
same  is  directly  applicable  to  organic  compounds,  especially  as  regards  the  conductivity 
of  salts,  acids,  bases,  &c. 

that  of  the  first  ray  becomes  weaker  and  when  the  principal  sections  of  the  two  crystals  form  an  angle  of  45°,  the 
two  rays  have  equal  intensities  («',  n') ;  if  the  crystal  is  rotated  still  more,  the  extraordinary  ray  becomes  more 
luminous,  whilst  the  first  (ordinary)  decreases  in  luminosity,  and  when  the  principal  sections  are  perpendicular  to 
one  another,  the  intensity  of  the  ordinary  ray  (*")  is  aero  (i.e.  it  is  not  seen),  only  the  extraordinary  ray  being 
seen  with  its  maximum  intensity  (n").  The  light  rays  emerging  from  the  second  rhombohedron  are  hence 
different  from  those  emerging  from  the  first,  these  latter  not  varying  in  intensity  when  the  prism  is  rotated,  whilst 
the  others  do  so. 

The  rays  leaving  the  first  prism  are  called  polarised,  and  are  distinguished  from  ordinary  light  rays,  since,  on 
passing  through  a  second  prism,  they  undergo  the  changes  described  above.  A  polarised  ray  passes  as  an  ordinary 
ray  through  a  second  rhombohedron  only  when  its  plane  of  polarisation  is  parallel  to  the  principal  section  of  the  new 
rhombohedron  It  ia  found,  then,  that  the  plane  of  polarisation  of  the  polarised  ordinary  ray  is  perpendicular  to 
the  plane  of  polarisation  of  the  extraordinary  ray.  Hence,  the  rays  E  and  O  vibrate  in  planes  perpendicular 
to  one  another  (Fig.  43). 

POLARISATION  BY  REFLECTION.  Polarised  light  rays  are  obtainable,  not  only  by  double  refraction,  but  also 
by  reflection  under  special  conditions,  namely,  when  a  light  ray  falls  on  a  plate  of  glass  at  an  incident  angle 
of  54°  35'. 

Polarised  light  is  also  obtained  by  simple  refraction,  by  passing  a  ray  of  light  through  a  series  of  superposed 
parallel  plates  or  sheets  of  tourmaline. 

1  The  angle  of  rotation  varies  with  the  length  of  the  light- wave  and  is  greater  for  violet  rays  (which  have  a  smaller 
wave-length  and  are  hence  refracted  more)  and  less  for  red  rays  (which  have  a  greater  wave-length  and  are  hence 
less  refrangible). 


28  ORGANIC    CHEMISTRY 

CLASSIFICATION    OF    ORGANIC    SUBSTANCES 

These  are  usually  divided  into  two  large  series  : 

(1)  That  of  the  open-chain  carbon  compounds  or  methane  derivatives,  termed 
also  compounds  of  the  fatty  or  aliphatic  series,  as  all  the  fats  and  many  of  their 
derivatives   belong  here.     This  series   embraces  two  groups   of  substances  ; 
that  of  the  saturated  compounds  or  derivatives  of  the  paraffins  (CnH2n  +  2)  and 
that  of  the  unsaturated  compounds  (olefines,  CnH2w  and  derivatives  of  acetylene, 

(2)  That  of  the  closed-chain  carbon  derivatives,  this  being  subdivided  into  : 

(a)  The  isocyclic  or  carbocyclic  compounds,  which  have  the  closed  chain 
formed  either  of  nuclei  of  six  carbon  atoms  with  six  available  valencies  to 
every  nucleus  (CnH2n_6,  benzene  derivatives  or  aromatic  compounds]  or  from 
nuclei  with  different  numbers  of  carbon  atoms,  but  more  highly  hydrogenated 
(cycloparaffins,  cyclo-olefines,  and  polymethylene  derivatives). 

(b]  The  heterocyclic  compounds,  the  closed  chain  of  which  contains  atoms 
(N,  P,  S,  0,  &c.)  other  than  carbon. 

The  hydrogenated  compounds  of'  carbon  are  called  hydrocarbons  and  are 
termed  saturated  when  the  carbon  atoms  are  joined  by  single  valencies,  and 
the  other  valencies  are  all  satisfied  by  hydrogen.  These  saturated  hydro- 
carbons cannot  combine  with  a  further  quantity  of  hydrogen. 

Hydrocarbons  containing  carbon  atoms  united  by  double  or  triple  linkings 
are  called  unsaturated  hydrocarbons,  and  these  can  combine  with  further 
quantities  of  hydrogen,  thus  becoming  saturated.  Other  important  hydro- 
carbons are  those  with  closed  chains,  which  we  shall  study  in  Part  III  of  this 
book. 

Usually  in  homologous  series,  with  increase  in  the  number  of  carbon  atoms, 
the  compounds  pass  from  the  gaseous  to  the  liquid  and  solid  states  ; 
e.g.  formic  acid,  with  one  carbon  atom,  is  a  liquid  and  boils  at  99°,  while  the 
homologous  acid  with  six  carbon  atoms  is  a  solid  and  boils  at  over  300°. 

OFFICIAL    NOMENCLATURE 

With  the  continuous  development  of  organic  chemistry  and  the  multiplication  of  new 
compounds,  the  need  was  often  felt  for  a  rational  method  of  naming  compounds  which 
would  facilitate  the  treatment  of  these  vast  numbers  of  compounds.  And  for  the  new 
nomenclature  to  be  the  more  efficacious  it  needed  to  be  international,  because  everywhere 
there  reigned  the  greatest  confusion  in  the  naming  of  chemical  compounds,  this  referring 
either  to  the  starting  substance  or  to  the  new  group  to  which  they  belonged,  or  to  the 
use  for  which  they  were  intended,  or  to  the  molecular  constitution,  and  so  on,  so  that 
the  same  substances  often  had  four  or  five  names. 

f»".  In  1892,  at  an  International  Convention  of  Chemists  at  Geneva,  a  general  system  of 
nomenclature  of  organic  compounds  was  agreed  on.  This  is  gradually  being  introduced 
into  chemical  literature,  and,  although  not  always  felicitous,  it  has  helped  to  simplify  the 
naming  of  compounds  and  to  reduce  the  confusion. 

Following  only  in  part  the  ideas  proposed  by  Kolbe  many  years  before,  the  new 
nomenclature  derives  the  names  of  all  compounds  from  the  names  of  the  fundamental 
hydrocarbons  to  which  the  compounds  can  be  referred,  taking  into  account  the  number  of 
carbon  atoms  present  as  well  as  the  nature  of  the  linking.  Thus,  to  the  fundamental 
names  of  the  saturated  hydrocarbons  :  methane,  ethane,  propane,  butane,  pentane, 
hexane,  heptane,  &c.,  the  addition  of  the  suffix  ol  indicates  the  presence  of  the  hydro xyl 
group  — OH,  and  thus  an  alcohol,  for  example,  methanol  (methyl  alcohol),  efhanol  (ethyl 

alcohol),  &c.  ;  the  suffix  al  serves  to  denote  the  aldehyde  group  (  —  C^  ) ,  thus,  e.g. 
methanal  =  formaldehyde,  ethanal  =  acetaldehyde,  &c.  ;  the  suffix  one  indicates  the 


OFFICIAL    NOMENCLATURE  29 

ketonic  group  (  —  CO  —  ),  thus,  propanone  (commonly  called  acetone),  &c.     The  suffix 
oic  is  used  to  indicate  the  organic  acids,  which  all  contain  the  characteristic  carboxyl 

(  /°     \ 

group  I  —  C02H,  i.e.  —  C<T  1,  and  thus  we  have  methanoic  (formic)  acid,  ethanoic 

V  X; 


acid,  propanoic  (propionic)  acid,  bwtanoic  acid,  pentanoic  acid,  &c. 

For  the  unsaturated  doubly  linked  hydrocarbons  the  fundamental  hydrocarbon 
ethylene  is  distinguished  with  the  name  of  ethene,  and  that  with  a  triple  bond  between  the 
two  carbon  atoms  (acetylene)  is  called  ethine. 

With  the  saturated  hydrocarbons,  isomerides  with  branched  chains  are  referred  to  the 
normal  hydrocarbon  (i.e.  non-branched)  with  the  longest  chain  present  in  the  molecule, 
numbering  progressively  its  carbon  atoms,  starting  at  the  end  nearest  to  the  point  where 
branching  occurs.  The  name  begins  with  that  of  the  residue  of  the  side-chain,1  then 
follow  the  successive  numbers  of  the  atoms  of  the  normal  chain  where  side-chains  join 
on,  and  finally  comes  the  name  of  the  normal  hydrocarbon. 

(1)      (2)      (3) 
CH3—  CH—  CH3 

CH3 

bears  the  official  name  methyl-2  -propane  (some  call  it  propyl-2  -methane),  and  isopentane, 

(1)       (2)        (3)       (4) 
CH3  —  Gii  —  O-fcla  —  CH3 

CH3 

that  of  methyl-2  -butane,  &c. 

When  there  are  also  secondary  ramifications  a  supplementary  numbering  is  used  ; 
thus,  with  isodecane, 

(1)       (2)       (3)      (4)      (5)      (6)       (7) 
CH3  —  CH2  —  CH2  —  CH  —  CH2  —  CH2  —  CH3 

(41  )  CH—  CH3 

(4n)  CH3 
the  official  name  would  be  metho-4I-ethyl-4-heptane. 

1  The  names  of  the  hydrocarbon  residues,  called  ateo  alkyl  groups,  are  formed  from  the  root  of  the  name  of  the 
corresponding  hydrocarbon,  with  the  suffix  yl  ;  thus,  with  methane  corresponds  the  methyl  residue  CH,  ;  with 
ethane,  ethyl.  —  C2H,  ;  and  then  follow  propyl,  —  :C,H,  ;  butyl,  —  04H,,  &c. 


PART  II.    DERIVATIVES  OF  METHANE 

AA.  HYDROCARBONS 

THE  hydrocarbons  form  a  very  large  and  important  group  of  organic 
substances,  which  are  composed  only  of  hydrogen  and  carbon,  and  give  rise 
to  other  most  varied  substances  by  replacement  of  part  or  all  of  the  hydrogen 
by  other  elements  or  groups. 

For  the  reasons  given  on  p.  28,  they  are  divided  into  two   main  groups  : 
saturated  and  unsaturated  hydrocarbons. 

(a)  SATURATED    HYDROCARBONS 

These  are  called  saturated  because  the  linkings  between  the  carbon  atoms 
are  simple  ones  and  ah1  the  valencies  are  saturated,  so  that  hydrogen,  chlorine, 
bromine,  iodine,  ozone,  &c.,  cannot  be  added  to  them  ;  the  halogens  do,  indeed, 
react  with  saturated  hydrocarbons  (fluorine  reacts  with  methane  even  at 
—  187°),  but  by  substitution  of  the  hydrogen  atoms. 

They  are  called  also  paraffins,  since,  like  the  common  solid  paraffins,  all 
the  saturated  hydrocarbons  resist,  in  the  cold,  the  action  of  chromic  acid, 
potassium  permanganate,  and  concentrated  nitric  and  sulphuric  acids,  and 
are,  in  general,  compounds  with  an  almost  indifferent  chemical  character. 
In  the  hot,  however,  energetic  oxidising  agents  convert  them,  more  or  less 
completely,  into  carbon  dioxide  and  water. 

As  a  general  rule,  these  hydrocarbons  are  insoluble  in  water  and  only 
some  of  them  dissolve  in  alcohol,  whilst  almost  all  are  soluble  in  ether. 

Of  the  direct  or  continuous  (normal)  and  branched  (isomeric)  open  chains , 
mention  has  already  been  made  on  pp.  15,  16,  and  28,  and  it  can  be  seen  how, 
starting  from  the  hydrocarbon,  04H10,  the  number  of  isomerides  rapidly 
increases  :  2  for  butane  ;  3  for  pentane,  C5H12  ;  5  for  hexane,  C6H14  (all 
known)  ;  while  for  C12H26  the  number  theoretically  possible  is  355  and  for 
C13H28,  892,  only  some  of  which  are,  however,  known.  All  the  terms  of  the 
paraffin  series  can  be  represented  by  the  general  formula  CMH2n  +  2,  and 
the  following  Table  (p.  31)  gives  the  name,  formula,  boiling-point,  and  melting- 
point  of  the  principal  known  paraffins.  The  official  nomenclature  is  described 
on  p.  28. 

The  first  members  of  the  series  are  gases,  then  follow  liquids  as  far  as 
C15,  and  beyond  that,  solids,  the  boiling-  and  melting-points  rising  with  increase 
of  the  molecular  weight  (see  p.  24). 

NATURAL  FORMATION  AND  GENERAL  METHODS  OF  PRO- 
DUCTION. These  hydrocarbons,  from  the  lowest  gaseous  members  to  the 
highest  solid  ones  (paraffin),  occur  abundantly  as  the  almost  exclusive  com- 
ponents of  petroleum  (especially  that  from  America),  and  it  is  not  difficult 
to  separate  single  individuals  from  these  complex  mixtures. 

In  many  natural  emanations  of  inflammable  gas,  methane  and,  to  some 
extent,  ethane  are  found  in  large  proportions,  and  the  solid  hydrocarbons 
occur  also  in  ozokerite  (which  see). 

30 


SATURATED    HYDROCARBONS 


31 


The  gaseous,  liquid,  and  solid  hydrocarbons  are  formed  abundantly  on  the 
dry  distillation  of  wood,  lignite,  bituminous  schists,  and  coal,  especially  boghead 
and  cannel  coals  which  are  relatively  rich  in  hydrogen  (see  Illuminating 

SATURATED   HYDROCARBONS,  CnH2n  +  2 
(After  hexane,  only  the  normal  ones  are  given) 


Melting-point 

Boiling-point 

Specific  Gravity 

CH4       Methane 

-184° 

-164° 

0-415  (-164°) 

(760  mm.) 

0-555 

(0°,  760  mm.) 

C2H6      Ethane  .          . 

-172-1° 

-84-1 

} 

0-446  (0°) 

(749  mm.) 

(0°at23-8atm.) 

C3H8      Propane           .      •    .          . 

-45° 

-44-5° 

0-535 

(0°at5atms.) 

(0°,  liquid) 

(  normal      .      .    „ 
C4H10     Butanes  i  . 
I  isobutane           •, 

— 

+  1° 
-17° 

0-600  (0°) 
0-6029  (0°) 

rnormal    . 

-200° 

+  36-3 

o 

0-454  (0°) 

C5H12     Pentanes-^  isopentane 

— 

+  30-4 

0 

0-622  ^ 

I  tertiary   . 

-20° 

+  9° 

at 

normal    .          . 

— 

69° 

0-6603  I** 
20 

dimethylisopropyl  - 

methane        .  . 

— 

58° 

0-666  J 

dimethylpropyl  - 

C6H14     Hexanes  J      methane 

— 

62° 

0-6766  (0°) 

methyldiethyl- 

methane 

— 

64° 

0-677  <^ 

trimethylethyl  - 

methane    '    . 



49-6 

o 

0-6488 

C7H16     Heptane           .         ,          . 

— 

98-3 

e 

0-683 

at 

C8H18     Octane             . 

—  . 

125-8 

o 

0-702 

C9H20     Nonane  .          .          .          . 

-51° 

150° 

0-718 

CioHaa    Decane  .          .          .       -  .          . 

-31° 

173° 

0-7467^ 

CnH24   Undecane        .          .          .          . 

-26° 

196° 

0-758L 

C12H26    Dodecane         .          . 

-12° 

215° 

0-7684 

Ci3H28  Tridecane        .        ,/.       ,  .. 

-   6° 

234° 

0-775 

CWHso  Tetradecane    .          ,          .          . 

+   4° 

252° 

0-775 

^15^32   Pentadecane   .          .          . 

+  10° 

270° 

0-776 

CieH34  Hexadecane    . 

18° 

287° 

0-775 

Qi7H36  Heptadecane  .          . 

22° 

303° 

0-777 

CigHss    Octodecane     .... 

28° 

317° 

0-777 

"5 

^19^40  Nonodecane    .          .          .          . 

32° 

330° 

0-777 

'o 

C20H42  Eicosane          , 

37° 

205°^ 

0-778 

bn 

C21H44  Heneicosane    .          .          .       *  „ 

40° 

215° 

0-778 

>45 

^22^46   Docosane         .... 

44° 

224° 

0 

0-778 

f  a 

^23^8  Tricosane         .... 

48° 

234° 

ft 
rr. 

0-779 

£ 

^WHso  Tetracosane     .          .                    . 

51° 

243° 

00 

0) 

0-779 

"^ 

C25H52   Pentacosane    .... 

53-5° 

— 

ft 

— 

a 

^26^54  Hexacosane     .... 

58° 



^a 



C27H56   Heptacosane  .... 

60° 

270° 

a 

>o 

0-780 

C2sH58   Octocosane      .... 

60° 

— 

1—1 

— 

^31^64  Hentriacontane 

68° 

302° 

•§ 

0-781 

^32^66  Dotricontane  (Dicetyl) 

70° 

310° 

0-781 

^35^12   Pentatricontane        .       "   . 

75° 

331  °) 

0-782  / 

C60H122  Hexacontane  .... 

101° 

— 

— 

32  ORGANIC    CHEMISTRY 

Gas)  ;  also  when  petroleum  residues  are  strongly  heated  under  pressure 
(cracking),  hydrocarbons  similar  to  petroleum  and  also  gaseous  ones  are 
formed. 

Of  the  numerous  synthetical  methods  of  preparation  of  the  saturated 
hydrocarbons,  the  following  more  important  ones  may  be  mentioned  : 

(a)  Any  member  of  the  series  can  be  obtained  by  reducing  the  halogen  derivatives 
of  the  hydrocarbon  (obtained  from  the  alcohols  and  the  halogen  hydracids)  by  means  of 
nascent  hydrogen  (generated  by  sodium  amalgam,  or  by  a  solution  of  sodium  in  absolute 
alcohol,  or  by  zinc  and  hydrochloric  acid,  or  by  heating  zinc  and  water  at  160°)  or  by 
hydriodic  acid,  especially  in  the  presence  of  red  phosphorus  (which  transforms  the  iodine 
into  hydriodic  acid) :  C2H5I  +  H2  =  HI  +  C2H6  ;   C2H5I  +  HI  =  I2  +  C2H6  (see  Table 
of  the  halogen  derivatives  of  the  hydrocarbons). 

(b)  The  alcohols  give  paraffins  on  being  heated  with  hydriodic  acid  : 

C2H6-OH  +  2HI  =  H2O  +  I2  +  C2H6. 

(c)  By  the  interaction  of  zinc  alkyls  and  water  : 

Zn(C2H6)2  +  2H20  =  Zn(OH)2  +  2C2H6. 

(d)  From  unsaturated  hydrocarbons  by  the  action  of  hydrogen,  e.g.  by  heating  acetylene 
and  hydrogen  at  400*-500°,  or  in  presence  of  platinum -black. 

(e)  By  eliminating  a  molecule  of  carbon  dioxide  from  the  organic  acids  and  salts  by 
heating  with  soda-lime  or  sodium  alkoxide  : 

CH3.COONa  (sodium  acetate)  +  NaOH  =  Na2C03  +  CH4. 

(/)  By  the  action  of  sodium  or  of  zinc  on  the  zinc  alkyls  or  alkyl  iodides  in  ethereal 
solution  in  a  closed  tube  (Wurtz),  two  alkyl  groups,  even  different  ones,  being  condensed  : 

(1)  2CH3I  +  Na2  =  2NaI  +  C2H6. 

(2)  C2H6I  +  C4H9I  +  Na2  =  2NaI  +  C2H5.C4H9. 

(3)  2CH3I  +  Zn(CH3)2  =  ZnI2  +  2C2H6. 

(g)  During  the  last  few  years  it  has  been  shown  that  magnesium  is  much  more  active 
than  zinc  in  many  organic  syntheses  (see  later,  Grignard  Reaction),  and  with  alkyl  iodides 
dissolved  in  absolute  ether,  magnesium  forms  magnesium  alkyl  salts  which,  on  decomposi- 
tion by  means  of  water  or  dilute  acid  or  ammonia  with  solid  ammonium  chloride,  yield 
the  saturated  hydrocarbons  :  C2H6I  +  Mg  =  C2H5MgI,  and  this  +  H2O  =  C2H6  + 
Mg(OH)I.  In  part,  however,  the  magnesium  fixes  the  halogen,  and  then  two  alkyl 
residues  condense,  forming  a  hydrocarbon  of  double  the  number  of  carbon  atoms  : 

2C2H6I  +  Mg  =  MgI2  +  C4H10. 

(h)  Sabatier  and  Senderens'  catalytic  process,  for  which  see  pp.  34  and  59. 
(i)  By  electrolysing  acetic  acid  : 

CH3— COOH  CH3 

+  2C02  +  H2 
CH3— COOH  CH3 

the  hydrogen  going  to  the  negative  pole  and  the  hydrocarbon  and  carbon  dioxide  to  the 
positive  one. 

METHANE  (MARSH  GAS),  CH4 

This  is  a  gas  which  is  often  found  ready  formed  in  nature,  and  in  former 
times  it  was  always  confused  with  hydrogen  .(inflammable  air).  Pliny  refers 
to  the  gases  which  exude  from  the  earth  in  certain  regions  and  are  inflam- 
mable (these  are  probably  the  sacred  fires  of  the  ancient  Chaldeans).  Basil 
Valentine  (1500)  records  fires  in  mines  preceded  by  the  emanation  of  asphyxi- 
ating, poisonous  vapours,  which  are  dispersed  and  rendered  innocuous  by  the 
fire  issuing  from  the  rock.  Also  Libavius  (1600)  speaks  of  the  inflammable 
and  explosive  gas  of  mines,  and  in  1700-1750  history  records  numerous 
explosions,  especially  in  coal-mines.  In  was  Volta  who,  in  1776,  when  studying 


METHANE  33 

the  same  gas,  which  is  also  evolved  in  marshes,  showed  that  it  differed 
from  hydrogen,  since  in  burning  it  requires  double  its  volume  of  oxygen  and 
forms  carbon  dioxide.  In  1785  Berthollet  proved  that  the  gas  is  formed  of 
carbon  and  hydrogen,  and  later  Henry,  Davy,  and  Berzelius  determined  its 
true  composition. 

It  occurs  abundantly  as  exhalations  from  the  earth  near  the  Caspian  Sea 
(sacred  fires  of  Baku)  and  in  the  peninsula  of  Apsheron  is  used  for  heating 
purposes. 

At  Pittsburg  there  are  great  wells  of  pure  methane,  and  it  is  found  also 
at  Glasgow,  in  the  Crimea,  and  also  in  Italy,  at  Pietra  Mala  (Bologna),  in 
Ferrarese,  in  Piacento  (Salsomaggiore),  &c.  It  always  occurs  in  coal-mines, 
being  formed  from  the  coal  by  slow  decomposition  and  remaining  occluded 
in  the  coal  under  great  pressure,  together  with  carbon  dioxide  and  nitrogen. 

It  is  invariably  developed  in  marshy  places,  where  there  is  organic  matter 
putrefying  under  water.  It  is  found  in  the  gas  of  the  intestines  of  man  and, 
still  more,  of  the  ruminants  (about  50  per  cent.  CH4),  being  produced  by  the 
action  of  enzymes  on  the  cellulose  of  vegetable  matter.  Illuminating  gas 
contains  up  to  40  per  cent,  of  it. 

PROPERTIES.  It  is  one  of  the  permanent  gases  (vol.  i,  p.  28)  ;  it 
liquefies  at  —164°  and  solidifies  at  —186°.  It  has  no  colour  or  taste,  but 
a  faint  garlicky  odour.  It  dissolves  slowly  but  appreciably  in  fuming  sul- 
phuric acid,  but  only  very  slightly  in  water  (0-05  per  cent.).  It  is  readily 
inflammable  and  burns  with  a  faintly  luminous  flame ;  mixed  with  oxygen 
it  forms  a  detonating  mixture  (inflammable  at  667°,  whilst  the  mixture 
with  ethane  inflames  at  616°  and  that  with  propane  at  547°),  the  maximum 
effect  being  obtained  with  1  vol.  of  methane  and  2  vols.  of  oxygen 
(CH4  +  202  =  C02  +  2H.JO).1  Mixed  with  air,  it  forms  the  firedamp  of 
coal-mines,  which  is  very  dangerous  owing  to  its  explosibility,2  although  it  is 
not  poisonous  since  miners  can  withstand  an  atmosphere  containing  9  per  cent, 
of  methane  ;  if  there  is  not  more  than  this  proportion,  it  produces  a  kind  of 
pressure  at  the  forehead,  which  ceases  immediately  on  breathing  pure  air. 

By  an  electric  charge  or  in  a  red-hot  tube,  it  decomposes  into  carbon  and 

1  Explosive  gas  mixtures  (Teclu,  1907) : 


Minimum  effect 

With  excess 

With  deficit 

Vols. 

Vols. 

Vols. 

100  volumes  of  air  +  hydrogen 

40 

170 

8-10 

,                        +  methane 

10 

— 

3-6 

,                         +  coal  gas  . 

17-20 

31 

4-7 

+  acetylene 

8-3 

130 

2-4 

+  ether  vapour 

3-3 

8 

1-5 

,                          +  alcohol  vapour 

6-5 

— 

3-4 

2  Since  the  methane  is  occluded  under  great  pressure  between  the  layers  of  coal,  its  development  and  hence 
also  the  danger  is  greater  when  the  atmospheric  pressure  diminishes  or  when  the  temperature  rises.  To  prevent 
explosions  of  firedamp,  the  miners  use  the  Davy  lamp  (vol.  i,  p.  377).  Considerable  danger  of  explosion  more 
often  exists  in  mines  owing  to  the  coal  dust  suspended  in  the  air  of  the  galleries  and  behaving  Jike  a  pyrophotic 
substance  (vol.  i,  p.  174) ;  as  a  precautionary  measure,  air  is  continually  circulated  through  the  galleries  by  powerful 
fans,  and  the  air  and  the  walls  are  moistened  by  means  of  pulverisers.  Hardy  has  constructed  an  apparatus  which 
allows  of  the  quantity  of  methane  being  determined  from  the  sound  produced  by  the  mixture  of  air  and  methane 
in  traversing  an  organ  pipe.  Mines  containing  much  dust  are  dangerous  even  if  the  atmosphere  is  moist  and  the 
Davy  lamp  is  used,  since  the  particles  of  coal  passing  through  the  gauze  into  the  lamp  may  issue  in  a  red-hot 
condition.  When  mines  are  being  excavated,  safety  explosives  (which  see)  are  used  to  avoid  fires  and  explosions. 
Sometimes  the  coal  ignites  in  certain  parts  of  the  mine  ;  in  such  cases,  work  is  not  suspended,  but  these  parts  are 
isolated  by  walls  and  if  the  fire  becomes  threatening,  recourse  is  had  (usually  with  success)  to  the  sealing  of  the 
mine  and  subsequent  inundation  with  water  or  filling  of  the  galleries  with  carbon  dioxide.  When  an  explosion 
occurs  in  a  mine,  a  large  amount  of  carbon  monoxide  is  formed  which  poisons  the  workers,  who  can,  however, 
sometimes  be  rescued  if  they  can  be  made  to  breathe,  sufficiently  promptly,  under  a  bell  containing  compressed 
air  (Mosso's  Method  ;  vol.  i,  p.  175). 

n  3 


34  ORGANIC    CHEMISTRY 

hydrogen,  and  a  few  unsaturated  hydrocarbons,  with  traces  of  benzene  and 
naphthalene. 

PREPARATION  IN  THE  LABORATORY.  Besides  by  the  general 
methods  given  above,  methane  is  formed  by  passing  a  mixture  of  carbon 
monoxide  or  dioxide  with  hydrogen  over  reduced  nickel  (catalyst)  heated  at 
250°  (Sabatier  and  Senderens)  :  CO  +  3H2  =  H20  +  CH4.  Attempts  have 
recently  been  made  to  put  this  method  on  an  industrial  basis,  by  transforming 
the  carbon  monoxide  and  dioxide  of  water-gas  into  methane  (Ger.  Pat. 
183,412).  Pure  methane  is  formed  by  passing  a  mixture  of  carbon 
disulphide  vapour  and  hydrogen  sulphide  over  red-hot  copper  (Bert helot) : 
CS2  +  2H2S  -f  8  Cu  =  4  Cu2S  +  CH4  ;  also  by  treating  aluminium  carbide 
with  water  :  C3A14  +  12H2O  =  4A1(OH)3  +  3CH4. 

In  the  laboratory  it  is  usually  prepared  from  an  intimate  mixture  of  one  part  of  crys- 
talline sodium  acetate  with  four  parts  of  soda  lime  (or  better,  with  four  parts  of  baryta  or 
with  a  mixture  of  anhydrous  sodium  carbonate  and  dry  powdered  calcium  hydroxide). 
This  is  heated  in  a  retort  or  in  a  hard  glass  tube  until  gas  begins  to  be  evolved,  the  tem- 
perature being  then  kept  constant.  As  impurities,  it  contains  a  little  hydrogen  and 
acetylene,  so  that,  before  collecting  the  methane,  the  gas  is  passed  over  pumice  moistened 
with  concentrated  sulphuric  acid. 

Chemically  pure,  it  can  be  obtained,  by  the  general  method,  from  zinc  ethyl  and  water. 

INDUSTRIAL  USES.  For  several  centuries,  the  inflammable  gases  issuing  from  the 
earth  and  from  petroleum  have  been  utilised  at  Baku  for  heating  lime-kilns.  In  North 
America,  as  far  back  as  1821,  these  natural  emanations  were  used  as  illuminating  gas. 
The  most  important  discoveries,  made  at  Pittsburg  in  1882,  resulted  in  98  per  cent,  of 
the  American  production  being  obtained  from  this  source  in  1900  ;  after  1905,  the  wells 
of  Louisiana  also  acquired  importance.  The  utilisation  of  the  gas  at  the  present  day 
is  carried  out  rationally  and  on  a  vast  industrial  scale,  the  gas  (issuing  from  suitably 
constructed  wells)  passing  to  large  gasometers  which  distribute  it  directly  to  over  500 
factories  and  40,000  houses,  where  it  is  employed  for  power,  heating,  and  lighting  (with 
the  Auer  mantle),  the  price  being  about  3^  cents  per  cubic  metre.  In  Canada,  400  wells 
are  being  used,  giving,  in  1907,  gas  of  the  value  of  £120,000.  In  England,  wells  have 
been  sunk  since  1900  which  yield  400,000  cu.  metres  of  gas  per  day.  The  spring  at 
Wels,  in  Austria,  which  gave  57,000  cu.  metres  of  gas  per  day  in  1894,  yielded  only  500 
cu.  metres  in  1901.  The  gas  utilised  in  the  United  States  of  America  represents  the 
following  values  in  pounds  sterling  :  in  1882,  40,000  ;  in  1890,  1,400,000  ;  in  1894, 
2,800,000  ;  in  1899,  4,000,000  ;  and  in  1906,  9,600,000.  These  gases  have  the  sp.  gr. 
0-624-0-645,  and  a  calorific  value  of  9000-10,000  cals.  per  cu.  metre.  The  composition 
varies  between  the  following  limits  :  CH4,  80-95  per  cent.  ;  H,  0-5-1-5  per  cent,  (some- 
times 15  per  cent.) ;  C2H4,  0-3-4  per  cent.  ;  CO,  0-0-6  per  cent.  ;  C02,  0-3-2-5  per  cent.  ; 
0,  0-35-0-80  per  cent.  ;  N,  0-5-3-5,  together  with  traces  of  H2S.  The  amounts  of  natural  gas 
used  at  Baku  were  46-5  million  cu.  metres  in  1905,  96-3  million  in  1906,  and  117  million 
in  1907,  the  composition  being:  C02,  3-3-8  per  cent. ;  C,,HW,  1-2-2-6  per  cent.  ;  0,  7-7-6 
per  cent.  ;  CH4,  54-8-60-2  per  cent.  ;  H,  13-58-0-8  per  cent.  ;  and  N,  20-4-25  per  cent. 

The  gas  which  is  used  at  Salsomaggiore  (Piacenza)  for  public  lighting  purposes  and  which 
issues  from  the  earth  together  with  petroleum  and  saline  waters  containing  iodine,  has  a 
specific  gravity  of  0-692,  and  the  following  composition  (Nasini  and  Anderlini,  1900) : 
CH4,  68  per  cent.  ;  C2H6,  21  per  cent.  ;  heavy  hydrocarbons,  1  per  cent.  ;  N,  8  per  cent. 
In  Italy,  1 ,520,000  cu.  metres  of  these  gases,  of  the  value  £2280,  were  used  altogether  in 
1902,  6,737,500  cu.  metres  in  1908,  and  8,270,000  cu.  metres,  of  the  value  £8760,  in  1909. 

Important  sources  of  these  gases  have  been  recently  discovered  in  Hungary,  England  (at 
Heathfield  a  well  gave  as  much  as  500,000  cu.  metres  per  day),  and  in  Denmark  (since  1872). 

ETHANE,  C2H6 

This  gas  is  found  dissolved  in  crude  petroleum  and  is  one  of  the  principal  constituents 
of  the  North  American  gas-wells  of  Delamater,  near  Pittsburg. 

It  is  a  gas  which  can  be  liquefied  at  0°  by  means  of  a  pressure  of  twenty-four  atmo- 
spheres and  then  has  a  sp.  gr.  0-446  ;  at  the  ordinary  pressure  it  becomes  liquid  and  boils 


PROPANE,  BUTANES,  PENTANES,  ETC.  35 

at  —84°  and  is  solid  and  melts  at  -172°.  It  is  almost  insoluble  in  water  ;  1  vol.  of 
absolute  alcohol  dissolves  1^  vol.  of  it.  It  burns  with,  a  faintly  luminous  flame,  and  is 
more  readily  soluble  than  methane.  In  the  laboratory  it  is  prepared  by  the  general 
methods  already  given  (p.  32). 

PROPANE,  C3H8  (METHYLETHYL,  CH'C2H5  or 
DIMETHYLMETHANE,    CH2(CH3)2) 

This  is  a  gas  like  ethane  and  becomes  liquid  at  -  44°,  or  at  0°  under  five  atmospheres 
pressure,  the  liquid  at  0°  having  a  sp.  gr.  0-535  ;  it  solidifies  and  melts  at  —45°.  It  is 
slightly  soluble  in  water,  and  absolute  alcohol  dissolves  6  vols.  of  it.  With  water  under 
pressure  and  at  temperatures  below  0°  it  forms  a  solid  hydrate,  which  decomposes  at 
+  8-5°.  The  illuminating  power  of  propane  is  about  1^  times  that  of  ethane.  It  is 
best  prepared,  in  the  laboratory,  by  reducing  isopropyl  iodide  by  means  of  the  copper- 
zinc  couple,  or  by  reducing  acetone  or  glycerol  with  hydriodic  acid  : 

C3H5(OH)3  +  6H  =  3H20  +  C3H8       or       CH3-COCH3  +  4H  =  H20  +  C3H8. 
glycerol  acetone 

BUTANES,   C4H10   (Two  Isomerides) 

(a)  Normal  Butane,  CH3  •  CH2  '  CH2  •  CH3  (diekhyl),  is  a  gas  which  liquefies  at    +  1°, 
and  at  0°  has  a  sp.  gr.  0-600.     It  is  found  in  Pennsylvanian  petroleum,  and  is  prepared 
in  the  laboratory  by  the  ordinary  methods  (p.  32). 

PTT 

(b)  Isobutane,   CH3  •  CH-c^Tj3   (trimethylmethane  or   methylpropane),  is   a   gas  which 

t^±±3 

becomes  liquid  at  —  115°  ;  it  is  contained  in  petroleum  and  is  prepared  by  the  usual 
methods  in  the  laboratory. 

PENTANES,  C5H12 

These  hydrocarbons  are  found  especially  in  the  petroleum  products  boiling  a  little 
above  0°,  and  are  placed  on  the  market  under  the  names  of  rhigolene  and  cymogen  for 
anaesthetic  purposes  and  for  the  manufacture  of  artificial  ice.  The  three  isomerides 
predicted  by  theory  are  known  : 

(a)  Normal  pentane,  CH3-  [CH2]3'CH3,  is  a  colourless,  mobile  liquid  boiling  at  +  37-3°, 
having  a  sp.  gr.  0-454  at  0°,  and  solidifying  only  at  about  —200°  ;   it  is  hence  used  for 
making  low-temperature  thermometers,  and  as  a  lubricant  in    the   Claude  liquid  air 
machine  (vol.  i,  p.  298).     It  occurs  abundantly  in  Pennsylvanian  petroleum. 

(b)  Isopentane,   CH3  •  CH  •  CH2  •  CH3   (methyl-2-butane  or  ethylisopropyl),  is  a    light 

CH3 

colourless  liquid  boiling  at  30-4°,  and  having  a  sp.  gr.  0-622  at  20°.  It  is  found  in  large 
quantities  in  petroleum,  and  can  be  prepared  artificially  from  isoamyl  iodide  by  the 
ordinary  methods  (p.  32). 

pTT  PTT 

(c)  Tetramethylmethane,  riT]3^>V<^nri3  (dimethyl-2-propane),  ie  found  in  the  gases  from 


petroleum,  and  is  liquid  at  +  9°  and  solid  at  —20°.  It  can  be  obtained  in  the  laboratory 
either  by  chlorinating  acetone,  CH3'CO'CH3,  by  means  of  phosphorus  pentachloride 
and  treating  the  dichloropropane  thus  formed  with  zinc-methyl  : 

CH3  Cl  CH3  _  CH3  CH3 

CH3>    <Cl  4       ^CHg  lU*  +  CH3^    ^CH-j' 

or  from  tertiary  butyl  iodide  by  the  action  of  zinc  methyl  : 

.CH3   „  ,   „   3   ,,  , 
Zn<    =       2    >  < 


CH3  .CH3       „  ,        „  CH3 

CH3  I        +  Zn<CH3  =  2  CH3  3 


The  constitutions  of  acetone  and  tertiary  butyl  iodide  having  been  determined  (see  later), 
that  of  tetramethylmethane  is  fixed.  And  since  the  reduction  of  butyl  iodide  yields 
isobutane,  the  constitution  of  the  latter  is  proved. 

HEXANES,  C6H14 

The  five  isomeric  hexanes  which  should  exist  are  all  known  (see  Table,  p.  31  )_     They 
are  found  particularly  in  petroleum  ether,  gasolene,  and  ligroin  (i.e.  in  the  portions  of 


36  ORGANIC    CHEMISTRY 

petroleum  boiling  below  150°),  together  with  heptanes  and  octanes.     They  are  formed  also 
from  shaly  coal  like  cannel  coal  and  boghead. 

HIGHER    HYDROCARBONS 

These  are  very  numerous  and  are  found  in  petroleum  and  in  its  residues  (vaseline, 
paraffin,  &c.)  ;  they  distil  unchanged  (after  C^)  only  in  a  vacuum,  the  boiling-point 
being  thus  lowered  by  about  100°. 

Many  of  these  higher  normal  hydrocarbons  were  prepared  synthetically  by  Krafft 
by  reducing  the  corresponding  fatty  acids,  alcohols,  and  ketones. 

HEPTACOSANE,  C27H56,  and  HENTRIACONTANE,  C31H64,  are  found  in  beeswax 
and  in  American  tobacco  (about  1  per  cent.),  the  former  being  also  found  in  soot. 

HEXACONTANE,  C60H122,  is  the  highest  term  of  the  paraffin  series  to  be  prepared 
synthetically  by  Hell  and  Hagele  in  1889  by  condensing  2  mols.  of  myricyl  iodide, 
C30H61I,  by  fusion  with  sodium,  which  removes  the  iodine  as  Nal.  It  melts  at  102°, 
is  slightly  soluble  in  alcohol  or  ether,  and  distils,  to  some  extent  unchanged,  in  a 
vacuum.  It  has  probably  the  normal  structure  and  thus  forms  the  longest  carbon 
atom  chain  as  yet  prepared  synthetically. 

Some  of  the  saturated  hydrocarbons  of  the  aliphatic  series  have  important 
practical  applications,  especially  as  sources  of  light  and  heat.  In  illuminating 
gas  are  found  the  gaseous  members,  in  petroleum  the  liquid,  and  in  paraffin 
the  solid  ones. 

A  brief  account  of  the  industrial  treatment  of  these  three  products  will 
now  be  given. 

ILLUMINATING    GAS1 

Illuminating  gas  and  the  other  products  of  the  dry  distillation  of  coal  vary  in  com- 
position with  the  nature  of  the  coal  employed.  In  gas  manufacture,  account  has  to  be 
taken  of  the  value  of  the  by-products  :  coke,  tar,  ammonia,  &c.,  which  sometimes  con- 
tribute largely  to  the  cost  of  manufacture.  So  that  mixtures  of  coal  are  used  which 
give  good  coke,  the  luminosity  of  the  gas  from  certain  coals  being  supplemented  by  mixing 
with  others  rich  in  hydrogen  and  fats,  such  as  some  of  the  very  expensive  English  coals, 
like  cannel  coal,  boghead,  various  shaly  coals,  &c.  In  general,  coals  used  for  making 
gas  have  compositions  varying  between  the  following  limits :  C,  78-85  per  cent.  ; 
H,  5-8  per  cent.  ;  O,  6-13  per  cent.  ;  N,  1-2-1-9  per  cent.  ;  and  S,  0-1-2  per  cent.,  a 
high  content  of  sulphur  being  harmful  ;  they  should  leave  little  ash  on  burning,  and 
preference  is  given  to  those  containing  considerable  quantities  of  volatile  products.  The 
more  hydrogen  there  is,  the  greater  will  be  the  useful  yield,  since  every  kilogram  of  hydro- 
gen can  gasify  4-5  kilos  of  carbon  (according  as  more  or  less  methane,  ethylene,  &c.,  is 
formed).  Gas-coal  giving  good  coke  contains  more  than  15  per  cent,  of  volatile  products 
and  less  than  35  per  cent. 

1  History.  This  industry  began  with  the  nineteenth  century,  its  apotheosis  being  reached  at  the  end  of  that 
century  with  the  application  of  the  incandescent  gas-mantle.  From  the  year  900  the  Chinese  have  employed 
petroleum  vapour,  distributed  by  wooden  pipes,  for  lighting  purposes.  It  was,  however,  only  in  1739  that 
James  Clayton,  in  investigating  the  causes  of  the  emanation  of  inflammable  gas  often  occurring  in  the  Lancashire 
mines,  heated  coal  in  closed  vessels  and  collected  the  gas  (illuminating  gas  !)  developed  in  large  bladders.  In 
1767,  Watson,  in  laboratory  experiments  on  a  small  scale,  obtained  gas,  ammonia,  and  coke  by  the  distillation  of 
coal.  This  was  the  time  when  coke  was  beginning  to  be  employed  in  metallurgical  operations,  and  in  1786  Lord 
Dundonald  used  the  gas  from  the  coke  furnaces  to  light  his  house,  and  Pickel  lighted  his  laboratory  with  the  gas 
formed  on  distilling  bones.  More  important  trials  were,  however,  made  in  England  by  W.  Murdock,  for  the 
illumination  of  large  works  by  distilling  coal.  Helped  in  his  undertaking,  first  by  Watt,  the  inventor  of  the  steam- 
engine,  and  afterwards  by  his  pupil  Clegg,  he  succeeded  in  1805  in  extending  lighting  by  gas  to  many  establish- 
ments. The  distillation  of  wood  was  studied  by  the  engineer  F.  Lebon,  in  France ;  and  in  1799,  a  patent  was  taken 
out  "  for  a  new  method  of  employing  combustibles  more  efficiently,  for  heating  or  lighting,  and  of  collecting  the 
various  products."  Some  days  later,  all  Paris  was  admiring  the  gas-lamp  which  Lebon  used  to  illuminate  the  gardens 
of  the  Hotel  Seignelay.  Probably  Lebon  did  not  then  foresee  the  wonderful  development  which  was  to  take  place 
in  gas  lighting  in  the  nineteenth  century  or  dream  of  the  monument  to  be  erected  to  him  many  years  later  in  his 
native  town,  Chaumont,  or  of  the  statue  which  was  dedicated  to  him  in  Paris  in  1905. 

It  was  when  the  use  of  large  plant  was  attempted  for  lighting  by  gas  that  technical  difficulties  cropped  up, 
inconveniences  which  were  negligible  on  a  small  scale  becoming  insurmountable  in  the  case  of  large  works.  It  was 
already  noticed  that  the  new  illuminating  gas  burned  with  a  rather  sooty  flame  and  disseminated  unpleasant 
odours,  whilst  in  the  works  the  piping  often  became  obstructed  owing  to  solid  distillation  products  being  carried 
by  the  gas.  If,  in  addition,  we  consider  the  popular  prejudice  to  any  innovation,  aggravated  by  the  fantastic 
propaganda  of  certain  scientific  men,  especially  in  France,  who  exaggerated  the  danger  of  explosion,  it  is  easy  to 
conceive  how  unpromising  the  conditions  of  this  industry  were  up  to  1812.  To  Clegg  is  due  the  elimination  of 
the  main  technical  difficulties,  the  tarry  matters  carried  along  by  the  gas  being  removed  by  means  of  a  number  of 


ILLUMINATINGGAS  37 

The  oxygen  present  in  coal  gives  rise  to  larger  or  smaller  quantities  of  carbon  dioxide 
and  monoxide,  and  it  cannot  be  denied  that  the  monoxide  is  a  powerful  poison.  Only 
10-15  per  cent,  of  the  nitrogen  present  in  the  coal  is  transformed  into  ammonia,  20  per 
cent,  being  found  in  the  gas  and  60  per  cent,  in  the  coke,  whilst  2-3  per  cent,  forms  hydro- 
cyanic acid  and  cyanides  in  the  gas  and  tar.  Moisture  in  the  coal  is  harmful,  since  water 
causes  an  increase  in  the  amount  of  carbon  dioxide  in  the  gas  and  also  absorbs  heat  for 
its  evaporation.  • 

In  order  to  judge  of  the  value  of  the  coal,  distillations  are  carried  out,  in  gasworks, 
in  small  laboratory  retorts  containing  a  weighed  quantity  of  coal  and  heated  at  a  very 
high  temperature  (900°  and  even  higher)  ;  the  gas  and  vapours  are  washed  in  bottles, 
first  with  lime-water  and  then  with  lead  acetate,  the  pure  gas  being  collected  in  a  cylinder 
over  mercury,  so  that  it  can  be  measured  and  its  composition  and  illuminating  power 
investigated.  To  judge  of  the  practical  value  of  a  coal,  use  is  made  of  the  product  of 
the  yield  of  gas  (that  is,  the  number  of  cubic  metres  from  100  kilos  of  coal)  and  its  candle- 
power.  For  any  given  coal,  this  product  is  almost  constant  ;  increase  of  the  temperature 
of  distillation  resulting  in  a  greater  yield  of  gas,  but  of  a  lower  illuminating  power. 
Naturally  this  rule  holds  only  between  certain  limits  of  temperature,  which  are  never 
exceeded  in  practice. 

Of  various  coals,  the  best  is  that  which  gives  the  highest  value  for  this  product,  but 
account  must  also  be  taken  of  the  yields  of  coke,  ammonia,  and  tar,  and  of  the  specific 
gravity  of  the  gas. 

The  temperature  of  carbonisation  varies  with  the  nature  of  the  coal  and,  in  general, 
with  fatty  coals  (bituminous)  the  evolution  of  gas  begins  at  50°,  and  at  a  red  heat  vapours 
of  liquid  products  pass  over  ;  at  a  higher  temperature,  gaseous  products  predominate. 

The  most  convenient  temperature  usually  lies  between  red  heat  (cherry-red)  and 
yellowish  white  heat.  In  general,  after  an  hour's  heating  (with  a  furnace  at  1400°),  the 
coal  in  the  retort  reaches  400°,  after  three  hours  950°,  and  after  five  hours  1075°.  On 
heating  1000  kilos  of  English  coal  at  different  temperatures  the  following  results  are 
obtained : 

At  red  heat         At  bright  orange  red 

(a)  Gas  obtained  (cubic  metres)  .  .  234  .  .  340 

(b)  Candle-power       ...  .  20-5  . .  15-6 

(c)  Candles  per  1000  kilos  =  a  x  b  .  .  4800  .  .  5300 

(d)  Composition :  Hydrogen        .  .  .  38-1  %  . .  48     % 

Carbon  monoxide     .  .  8-7  %  .  .  14     % 

Methane           .          .  .  42-7  %  . .  30-7  % 

Heavy  hydrocarbons  .  7-6  %  .  .  4-5  % 

Nitrogen          .          .  .  2-9%  ..  2-8% 

Gas  prepared  at  a  higher  temperature  has  a  lower  calorific  power. 

cooled  tubes,  and  further  purification  being  effected  by  lime,  the  gas  being  then  collected  in  large  gasometers, 
from  which  it  was  distributed  by  pipes  to  the  consumers.  Thus,  it  became  possible  in  1813  to  light  part  of  London 
with  coal  gas,  and  in  1815  Winsor  illuminated  certain  quarters  of  Paris.^ 

Nobody  on  the  Continent  dared  attempt  a  similar  industry  ;  everybody  was  distrustful,  not  foreseeing  its 
great  future  and  being  frightened  by  the  technical  difficulties  which  met  this,  the  first  great  chemical  industry, 
for  many  years  confined  to  England.  It  was  in  this  country  that  it  underwent  the  most  rapid  extension  and  per- 
fection (in  1823,  fifty-two  towns  were  lighted  by  gas),  the  scientific  and  practical  men  giving  it  their  entire  support. 
In  1810  a  powerful  English  company  was  founded  by  Clegg  and  became  later  the  famous  Imperial  Continental 
Gas  Association,  which  with  a  capital  of  £2,000,000  in  1824,  £3,500,000  in  1874,  £3,800,000  in  1897,  and  £5,000,000 
in  1908,  was  formed  with  the  view  of  undertaking  the  lighting  of  the  principal  European  towns.  Even  to-day 
many  towns  are  still  pledged  to  contracts,  as  yet  unexpired,  with  the  great  English  companies.  London  itself, 
within  the  last  few  years,  has  found  the  greatest  obstacle  to  the  introduction  of  electric  lighting  in  contracts  with 
gas  companies  which  have  already  made  fabulous  profits. 

In  Germany,  the  first  small  gas-plant  was  that  of  Lampadius  in  1816,  used  for  his  own  establishment,  extension 
being  subsequently  effected  as  a  result  of  the  work  of  Flashoff  and  Dinnendhal.  At  Berlin  the  first  attempt  was 
made  in  1829  ;  then  followed  Hanover,  and  in  1884,  557  German  towns  were  lighted  by  gas,  the  annual  consump- 
tion of  coal  being  1,700,000  tons.  In  Austria  the  first  plant  was  erected  in  1818  by  Prechtl.  In  America,  Baltimore 
was  illuminated  by  gas  in  1806,  Philadelphia  in  1822,  and  New  York  in  1834.  At  Milan  gas  lighting  was  introduced 
in  1832. 

After  1870  all  the  principal  populous  centres  and  even  the  small  towns  were  lighted  by  gas,  all  objection  to  this 
form  of  illumination  having  disappeared  ;  experience  had  shown  that  the  expected  terrible  explosions  of  mixtures 
of  gas  and  air  did  not  occur  and  that  the  small  accidents  which  did  happen  were  not  more  serious  than  those  occur- 
ring daily  with  paraffin  lamps.  The  victory  over  petroleum,  although  furiously  contested,  was  especially  complete 
in  the  case  of  public  lighting. 

To  this  success  have  contributed,  most  of  all,  the  incessant  improvements  of  methods  of  manufacture,  wlvoh 
have  resulted  in  the  supply  of  a  purer,  more  abundant,  and  more  economical  gas. 


38  ORGANIC    CHEMISTRY 

The  composition  of  gas  varies  also  according  as  the  heating  is  more  or  less  prolonged.1 
It  will  be  seen  that  the  diminution  of  luminosity  is  less  proportionally  than  the  increase 
in  volume  of  the  gas,  and  to-day  the  distillation  is  pushed  to  a  temperature  of  1100-1200°, 
this  resulting  in  greater  (absolute,  not  relative)  quantities  of  light,  luminous  hydrocarbons 
and  of  hydrogen  being  obtained.  It  is  hence  important  to  employ  suitable  mixtures  of 
coals,  so  that  these  may  be  impoverished  as  much  as  possible  at  a  high  temperature, 
the  relatively  low  luminosity  being  compensated  for  by  the  addition  of  special  fatty 
coals,  as  already  mentioned,  and  also,  at  the  present  day,  of  benzene. 

The  duration  of  the  distillation  varies  from  3  to  5  hours  ;  the  extra  amount  of  gas 
that  would  be  obtained  by  heating  further  would  be  insufficient  to  make  up  for  the  cost 
of  heating.  100  kilos  of  WestphaHan  coal  give  about  71  kilos  of  coke,  4  kilos  of  tar, 
5  kilos  of  ammonia  liquors,  and  17  kilos  (30-5  cu.  metres)  of  gas  ;  loss,  3  kilos. 

The  COMPONENTS  OF  ILLUMINATING  GAS  obtained  from  coal  are 
very  varied  and  can  be  embraced  in  three  groups  :  (a)  combustible  diluents  : 
H,  CH4,  CO  ;  (6)  light-yielding  gases  and  vapours  :  ethane,  ethylene,  butylene, 
acetylene,  crotonylene,  allylene,  pentylene,  benzene,  toluene,  xylene,  thiophene, 
styrene,  indene,  naphthalene,  acenaphthene,  fluorene,  propane,  butane,  pyri- 
dine,  phenols ;  (c)  inert  or  "harmful  impurities :  C02,  NH3,  HCN,  CS2,  COS,  and  N ; 
naturally  the  majority  of  these  substances  are  present  only  in  traces. 

The  quantitative  composition  by  volume  of  the  gas  usually  varies  between 
the  following  limits  :  C02,  1-25-3-20  per  cent.  ;  CO,  4-5-6-5  per  cent,  (for 
English  coals,  6-9  per  cent.,  and  for  German  coals,  occasionally  9-11  per 
cent.)  ;  H,  42-55  per  cent.  ;  CH4,  32-38  per  cent.  ;  N,  1-3  per  cent.  ;  0, 
0-0-5  per  cent.  ;  aromatic  hydrocarbons  (benzene,  &c.),  0-8-1-4  per  cent.  ; 
unsaturated  hydrocarbons  (ethylene,  2-2-5  per  cent.  ;  acetylene,  0-1-0-2  per 
cent.  ;  propylene,  0-2-0-5  per  cent.,  &c.)  The  specific  gravity  of  gas  varies 
from  0-350  to  0-500  (air  =  1)  and  1  cu.  ft.  of  gas  weighs  rather  more  than 
half  an  ounce.2  The  calorific  power  of  illuminating  gas  ranges,  as  a  rule, 
from  4000  to  5000  cals.  per  cubic  metre,  thus  producing  the  same  heating 
effect  as  3-43  kw. -hours.  The  illuminating  power  is  discussed  later. 

PROPERTIES  OF  ILLUMINATING  GAS.  In  addition  to  the  lighting 
power,  for  which  it  is  mostly  used,  to  the  heating  power  which  makes  it  a 
valuable  source  of  mechanical  energy  for  gas  motors,  to  the  relatively  low 
specific  gravity  which  renders  it  useful  in  aeronautics,  attention  must  be  paid 
to  the  explosive  properties  of  illuminating  gas  when  mixed  with  air  (see  p.  33), 
and  to  its  poisonous  properties  even  when  present  in  only  2  per  cent,  by  volume. 
Its  poisoning  effect  is  due  especially  to  the  carbon  monoxide  present,  but  also, 
to  some  extent,  to  other  components.  When  the  first  symptoms  of  poisoning 
are  observed,  fatal  consequerices  can  be  prevented  by  vigorous  respiration 
of  pure  air  or,  better,  oxygen,  while  the  use  of  compressed  air  according  to 
Mosso's  system  also  gives  good  results  (vol.  i,  p.  175). 

RETORTS.  Murdoch's  first  retorts  were  of  cast  iron,  placed  vertically  in  a  furnace 
(Fig.  44),  but  as  it  was  inconvenient  to  charge  them  Murdoch  introduced  inclined  retorts 
(Fig.  45),  which  he  changed  later  into  horizontal  retorts  of  cast  iron  (Fig.  46). 

1  Wright  analysed  the  gas  for  three  different  periods,  starting  from  the  beginning  of  the  distillation,  the  results 
being : 

After  After  After 

40  minutes.         three  hours.  six  hours. 

Per  cent.  Per  cent.  Per  cent. 

H,S  0-4  0-78  0-38 


CO, 

CO  . 

CH4. 

H     . 

Heavy  hydrocarbons 

N     . 


2-08  1-34                       0-59 

4-52  6-73                      7-52 

56-46  37-46  14-61 

25-36  48-36  91-94  (?) 

8-51  3-13                       2-78 

2-37  s    2-20                       2-18 


1  By  passing  ordinary  gas  into  a  retort  filled  with  coke  at  1200"  or  a  higher  temperature,  a  new  gas,  deprived 
of  heavy  hydrocarbons,  oxygen,  and  carbon  dioxide,  very  poor  in  methane  (6  per  cent.),  rather  richer  in  carbon 
monoxide  (7  to  8  per  cent.)  and  very  rich  in  hydrogen  (up  to  84  per  cent.)  is  obtained.  This  new  gas  can  be 
used  for  aeronautical  purposes  its  specific  gravity  bein«  about  0-23  (Continental  Gas  fiesetttchaft,  Dessau,  1910). 


GAS    RETORTS 


39 


In  1820  J.  Graf  ton  suggested  the  use  of  horizontal  retorts  of  fireclay,  since  these  resist 
heat  better,  cost  less  and  last  longer.  The  most  convenient  form  was  that  with  a  Q  -shaped 
or  elliptical  section  (Fig.  47),  and  the  most  suitable  dimensions  for  these  horizontal 
retorts  were  found  to  be  :  width  of  the  mouth,  43-53  cm.,  height  at  the  middle,  31-38  cm., 
and  length,  2-3  metres.  One  end  was  closed  and  the  mouth  was  swelled  at  the  edge, 


FIG.  44. 


FIG.  45. 


FIG.  46. 


which  carried  screws  serving  to  fix  the  metal  cover  fitted  with  the  delivery  tube.  These 
retorts  were  charged,  according  to  their  capacity,  with  100-200  kilos  of  coal,  broken  into 
uniform  -  lumps.  Various  mechanical  connections  were  devised  to  allow  of  the  retort 
being  charged  and  discharged  rapidly  and  with  the  least  expense  for  hand  labour,  and  one 
of  the  best  arrangements,  with  a  battery  of  retorts  placed  in  regenerator  furnaces  (see 
vol.  i,  p.  500),  is  that  shown  in  Pig.  48.  However,  since  1890  it  has  become  general  in 
the  principal  European  towns  to  use  inclined  retorts  of  elliptical  section,  which  were 
suggested  anew  by  Coze  and  are 
furnished  with  two  mouths  pro- 
jecting from  the  two  ends  of  the  fur- 
nace (double-ended  or  "through" 
retorts).  When  these  are  inclined 
at  an  angle  of  32°  and  are  charged 
automatically  from  above,  the  coal 
distributes  itself  in  a  layer  of  uni- 
form depth  along  the  whole  of  the 
retort  (Fig.  49).  The  gas-discharge 
tube  is  inserted  at  the  lower  mouth, 
which  at  the  end  of  the  operation 
is  opened,  the  coke,  while  still  hot, 
being  completely  and  immediately 
discharged  into  an  iron  truck  or 

on  to  a  moving  endless  perforated  FIG.  47. 

band,  the  pieces  of  coke  remaining 

alight  being  sprinkled  with  water  before  being  discharged  on  to  the  coke  ground.  Similar 
retorts  are  used  with  elliptical  mouths  ;  the  upper  one  is  rather  larger  (63  cm.  x  35  cm.) 
than  the  lower  (57  cm.  x  30  cm.),  and  the  length  is  about  3-8  metres.  At  the  present 
day  they  vary  from  this  length  up  to  6  metres. 

The  advantages  of  this  system  are  shown  by  the  following  results,  which  refer  to  three 
batteries  of  fourteen  (1)  inclined  and  (2)  horizontal  retorts : 


Duration  of  the  distillation          . 

Charge  per  retort 

Number  of  charges  per  8  hours 

Total  coal  distilled  in  8  hours 

Cost  of  labour  per  1000  kilos  of  coal 


Inclined 

3  hours 
165  kilos 
112 


Horizontal 

4^  hours 
152  kilos 

72 


18,500  kilos        11,000  kilos 


10  pence 


18  pence 


40 

The  pressure  in  the  interior  of  the  retorts  should  be  carefully  regulated,  since  if  it 
becomes  too  great,  escape  of  the  light  gases  and  vapours  readily  occurs  and  the  develop- 
ment of  vapours  and  gases  is  slackened,  the  hydrocarbons,  which  remain  for  a  long  time 
in  contact  with  the  red-hot  walls  of  the  retort,  undergoing  further  decomposition  with 
deposition  of  graphite  on  the  walls  and  liberation  of  hydrogen.  In  order  to  avoid  these 
inconveniences  the  retorts  are  to-day  put  in  indirect  communication  with  aspirators  or 
pressure  regulators  placed  beyond  the  washing  apparatus  (scrubbers,  &c.). 

The  layer  of  coal  in  the  retort  should  not  be  too  deep,  as  otherwise  the  gases  given  off 
are  decomposed  on  contact  with  the  upper  layers  of  hot  coke. 

With  the  view  of  avoiding  decomposition  of  the  more  luminous  gases  which  are  evolved 
principally  at  the  beginning  of  the  distillation,  Bentrup  (1903)  proposed  passing  a  con- 
tinuous current  of  water-gas  (see  vol.  i,  pp.  392,  393)  into  the  retort  to  remove  these 
products  rapidly  from  contact  with  the  hot  walls  of  the  retort  ;  the  water-gas  is  produced 
in  an  adjacent  retort  also  containing  red-hot  coke. 


As  often  happens  in  other  fields  of  work,  so  also  in  the  industries  a  return  to  older 
methods  often  offers  advantages.  Thus  it  appears  at  the  present  time  that  the  vertical 
retorts  again  brought  into  use  by  Settle  and  Padfield  are  destined  to  supplant  the  inclined 
ones.  In  1905  Dr.  J.  Bueb  made  works  experiments  with  a  battery  of  ten  retorts,  4  metres 
in  length,  placed  vertically  in  a  furnace  and  provided  with  an  upper  aperture  for  charging 
and  a  lower  one  for  discharging  (that  is,  the  furnace  surrounds  only  the  external  vertical 
surface  of  the  retort,  which  is  heated  by  hot  gases  circulating  through  numerous  channels, 
as  shown  in  Fig.  50).  In  this  way  a  larger  charge  (up  to  500  kilos)  is  used,  the  luminous 
gases  are  not  decomposed  and  the  yield  of  gas  is  higher,  as  the  temperature  of  the  retort 
reaches  1300-1400°  C.  ;  at  the  same  time  very  little  naphthalene  is  produced,  the  incon- 
venience caused  by  depositions  of  naphthalene  in  the  cold  parts  of  the  pipes  being  thus 
avoided.  In  addition,  the  yield  of  ammonia  is  increased  by  35  per  cent.,  the  separation 
of  the  tar  is  facilitated  and  the  cost  of  labour  diminished  ;  a  less  amount  of  a  harder  coke 
is  obtained,  and  the  quantity  of  tar  is  considerably  decreased,  while  the  production  of 
gas  is  increased  (Ger.  Pat.  155,742).  N 

Fig.  50  shows  a  double  battery  of  Bueb  vertical  retorts,  4  metres  high  and  slightly 
conical  in  shape,  the  wider  mouth  at  the  bottom.  By  means  of  the  elevator  A  the  coal 
is  introduced  into  the  hopper  B  C,  whence  it  passes  into  the  movable  scoops  D,  which 


FURNACES 


41 


carry  it  to  the  retorts.  At  the  end  of  the  distillation  (which  lasts  7-8  hours)  the  coke  is 
discharged  into  the  metal  hopper,  F,  and  thence  into  the  channel,  G,  where  a  band  running 
on  rollers  carries  the  spent  coke  to  the  store.  The  gas  issues  at  the  top  of  the  retort  and 
by  the  tubes,  E,  passes  into  the  hydraulic  main,  /,  and  so  into  the  piping,  L  ;  the  tar 
and  the  ammonia  liquors  are  discharged  from  the  hydraulic  main  into  the  tube,  M ,  leading 
to  the  depositing  tank. 

In  order  to  increase  the  yield  of  gas  by  10-15  per  cent,  it  has  recently  been  proposed 
to.  utilise  the  high  temperature  of  the  coke  (1400°  C.)  remaining  in  the  retorts  at  the  end 
of  the  distillation  to  produce  a  certain  quantity  of  water-gas  by  passing  a  current  of 
steam  in  at  the  bottom  of  the  retort  for  an  hour.  It  cannot,  however,  be  denied  that  by 
this  wet  process  the  proportion  of  carbon  monoxide  in  the  gas  is  increased.  In  any  case 
total  yields  of  360  cu.  metres  of  gas  per  1000  kilos  of  coal  have  been  obtained  in  this" way. 

The  economy  in  labour  effected  by  this  retort  is  very'great,  and  it  is  calculated  that, 
whilst  with  horizontal  retorts  every 
workman  produces  about  1600  cu. 
metres  of  gas  per  day,  with  the 
vertical  retorts  the  amount  reaches 
7000  cu.  metres. 

From  1906  to  1910  furnaces  with 
507  batteries  of  5500  vertical  re- 
torts, representing  a  total  daily 
production  of  2,200,000  cu.  metres 
of  gas,  have  been  manufactured  by 
one  single  firm  at  Dessau  (for  Berlin, 
Cologne,  Zurich,  Trieste,  Geneva, 
&c.). 

In  the  working  of  these  vertical 
retorts,  which  do  indeed  represent 
a  marked  advance  on  the  Coze 
inclined  retort,  certain  disadvan- 
tages have  been  observed,  the  coke 
formed  being  harder  than  the  ordi- 
nary and  not  so  well  suited  for 
domestic  purposes  ;  whilst  the  gas- 
discharge  tubes  soon  become 
obstructed  with  tarry  matters  so 
that  they  require  cleaning  every 
3-4  days  ;  distillation  with  steam 
during  the  last  phase  of  the  heat- 
ing relieves  this  inconvenience  to 
some  extent.  By  some  the  pro- 
duction of  water-gas  as  described  above  is  not  regarded  as  advantageous,  the  same 
quantity  of  water-gas  being  obtainable  more  economically  with  special  plant. 

A  further  and  more  recent  modification  consists  in  the  use  of  chamber  furnaces  (similar 
to  those  for  making  metallurgical  coke,  see  vol.  i,  p.  367). 

At  Monaco  in  1906  and  at  Vienna  in  1909  inclined  chamber  furnaces  were  employed 
(Kopper  system,  Fig.  51).  Coal  from  the  hopper,  2,  passes  down  an  inclined  plane  and 
fills  the  chamber,  5  ;  the  gas  is  led  into  the  trough,  1,  the  coke  is  discharged,  by  opening 
the  large  lower  door  with  a  crane,  on  to  an  inclined  plane  and  so  to  the  chain  transporter,  6, 
and  the  gasogen,  8,  passes  the  gas  to  the  dust-chamber,  7,  and  then  to  the  ascension  pipes 
under  the  chambers  ;  9  shows  another  battery  of  inclined  chambers.  With  chamber 
furnaces  a  better  gas  is  obtained  with  a  less  expensive  plant  and  a  decided  economy  in 
labour,  the  daily  yield  of  gas  per  workman  reaching  9000  cu.  metres.  A  plant  of  this 
kind  was  finished  in  1910  at  Padua. 

With  horizontal  or  inclined  retorts  the  coal  is  heated  for  4-6  hours  ;  with  vertical 
ones,  12  hours  ;  and  with  chamber  furnaces,  24  hours. 

FURNACES.  Retorts  were  first  of  all  heated  by  direct  flame,  but  in  this  way  the 
heat  is  inefficiently  utilised  ;  then  indirect  heating  by  flues,  just  as  for  steam  boilers,  was 
tried,  but  the  nearer  retorts  wore  out  very  rapidly,  so  that  later  several  retorts  were  placed 


FIG.  49. 


42 


ORGANIC    CHEMISTRY 


in  one  furnace  in  direct  contact  with  the  hot  gases,  these  being  so  interrupted  and  deviated 
that  the  surfaces  of  all  the  retorts  were  uniformly  heated  (Pig.  48). 

At  the  present  time  the  use  of  the  regenerator  gas  furnace  (gasogen,  see  vol.  i,  p.  501 ) 
has  become  general,  coke  (usually  waste)  being  employed,  and,  in  countries  where  there  is 


FIG.  50. 

little  demand  for  tar,  the  latter  being  used  as  fuel  by  injection  into  suitable  furnaces. 
The  coke  used  to  heat  the  furnaces  represents  about  25  per  cent,  or  30  per  cent,  of  the 
total  amount  produced.  In  some  works  (e.g.  at  Turin  since  1909)  the  heating  of  the 
furnaces  is  profitably  effected  by  9-10  per  cent,  of  tar  (on  the  weight  of  coal  distilled), 
burnt  in  special  gasogens. 

The  wear  of  the  furnaces  and  retorts  is  considerable,  and  their  cost  is  calculated  as 


PURIFICATION    OF    GAS 


43 


annual  expenditure  rather  than  as  cost  of  plant,  since  they  are  sometimes  remade  or 
renovated  twice  a  year. 

PURIFICATION  OF  GAS.  The  crude  products  obtained  directly  from  the  carbonisa- 
tion of  bituminous  coal  cannot  be  used  immediately  for  lighting  and  other  purposes.  The 
gas  issues  from  the  retorts  at  very  high  temperatures  (up  to  250°),  and  it  is  evident  that, 
as  it  gradually  cools,  various  products  separate,  first  of  all  those  which  are  solid  or  liquid 
at  ordinary  temperatures.  It  is  necessary  to  remove  the  tar,  naphthalene,  ammonia 
liquor,  and  the  cyanogen  and  sulphur  compounds  by  means  of  the  following  apparatus. 

HYDRAULIC  MAIN.  This  is  a  wide  circular  or  semi-circular  pipe  (diameter, 
30-60  cm.)  of  sheet-iron  or  cast-iron  (Fig.  48  V),  containing  water  and  tar,  and  placed 
above  the  retorts  so  that  the  ascension  pipes,  R  (12-18  cm.  in  diameter)  from  one  battery 
of  retorts  dip  into  it,  these  pipes  starting  from  the  lower  parts  of  the  retorts  and  carrying 
off  all  the  hot  gas  developed.  The  tubes,  R,  are  sealed  hydraulically  by  dipping  into  water 
in  the  hydraulic  main,  in  which  most  of  the  tar  and  a  little  of  the  ammoniacal  liquor 
condense.  The  hydraulic  main  falls  slightly  towards  one  end  so  as  to  facilitate  flow  of 
the  tar  to  the  store-tanks,  in  which  it  gradually  becomes  almost  entirely  separated  from 
the  ammonia  liquors,  being  sold  to  the  tar-distiller  with  a  content  of  not  more  than  5 
per  cent,  of  water  at  a  price  of  about  17  pence  per  cwt.  (lire  3,50  per  quintal). 


FIG.  51. 

The  still  very  impure  gas,  holding  in  suspension  large  numbers  of  tar  drops — which 
render  difficult  the  condensation  of  the  naphthalene — and  having  a  temperature  of 
60-100°  C.  is  gradually  cooled  to  12-15°  C.  by  causing  it  to  traverse  a  large  iron  pipe 
passing  round  inside  the  whole  of  the  works  and  cooled  by  the  air  ;  the  gas  then  reaches 
a  condenser  formed  either  of  a  battery  of  long  iron  tubes  (Fig.  52)  sprryed  outside  with 
water,  or  of  a  series  of  three  or  four  double-jacketed  cylinders  cooled  inside  and  outside  by 
the  air,  the  gas  passing  into  the  jacket  (Fig.  53)  ;  or  the  gas  may  be  circulated  round  a 
number  of  narrow  tubes  through  which  passes  a  continuous  stream  of  cold  water  (Fig.  54). 
The  cooling  thus  effected  is  gradual,  and  the  separation  of  the  naphthalene  and  tar  is 
more  complete,  while  there  is  no  danger  of  stoppages  from  the  naphthalene  ;  in  winter 
the  gas  enters  the  cooler  at  50-60°  C.  and  leaves  at  5-10°  C.,  while  in  summer  it  enters  at 
60-70°  C.  and  emerges  at  30-35°  C.  At  the  bottom  of  these  tubes  is  found  a  deposit 
of  tar — which  is  discharged  into  tanks — and  of  ammonia  liquors  at  7-8°  Be.  The 
consumption  of  water  in  these  coolers  is  from  3-4  cu.  metres  per  24  hours  per  1000 
cu.  metres  of  gas. 

If  an  obstruction  of  naphthalene  occurs  at  any  point,  the  pressure — indicated  by 
manometers  placed  along  the  tubes — shows  an  increase  at  that  point. 

The  gas  issuing  from  the  condensers  still  contains  suspended  tar,  which  it  is  necessarj 
to  separate.  To  this  end  serves  Audouin  and  Pelouze's  tar-separator,  shown  in  Fig.  55. 
The  gas  passes  along  the  tube  B,  which  opens  into  a  perforated  double-walled  bell,  D,  the 
pressure  in  which  is  regulated  by  a  compensating  weight  and  pulley,  G.  The  bell  is 
partially  sealed  hydraulically  and  rises  more  or  less,  leaving  open  a  greater  or  less  number 
of  apertures,  according  to  the  pressure  of  the  gas.  The  gas  is  thus  subjected  to  a  kind 


44 


ORGANIC    CHEMISTRY 


of  filtration  through  small  orifices,  the  fine  drops  of  tar  being  condensed  into  larger  drops, 
which  separate  and  collect  in  E,  whence  the  excess  is  run  off  at  F.  The  gas  thus  purified 
from  tar  passes  by  the  tube  C  to  the  ammonia-condensing  apparatus.  The  tar-separator 
should  not  be  kept  too  cold  (12-15°  C.) 

NAPHTHALENE  SEPARATORS.  Naphthalene  is  a  product  of  the  condensation 
by  heat  of  the  heavy  hydrocarbons  of  the  gas.  It  is  difficult  to  imagine  how  pertinaciously 
gas  carries  through  all  the  purifying  operations  considerable  quantities  of  naphthalene 
suspended  in  it,  and  how  slowly  this  naphthalene  is  deposited  in  town  mains,  ultimately 
stopping  them  and  causing  great  inconvenience  and  expense  to  consumers  and  manu- 
facturers. 

In  1899  Bueb,  on  the  basis  of  former  experiments  of  Young  and  Glover,  succeeded  in 
avoiding  this  trouble  to  a  great  extent  by  passing  the  gas  (first  washed  with  water  in 

the  "  Standard  "  washer-scrubber  to  separate  the 
ammonia)  into  a  drum  similar  to  the  "Standard" 
(see  below),  but  with  three  independent  chambers  in 
which  the  gas  is  washed  with  anthracene  oil  of 
medium  density  (prepared  by  the  distillation  of  tar 
and  having  a  b.pt.  350-400°  C.),  which  dissolves 


FIG.  52. 


FIG.  53. 


FIG.  54. 


and  fixes  almost  all  the  naphthalene.  When  the  oil  of  the  first  chamber  is  saturated  it 
is  removed,  and  that  of  the  second  chamber  passes  into  the  first  and  that  of  the  third 
into  the  second  ;  the  third  chamber  is  charged  with  fresh  oil,  containing  4  per  cent,  of 
benzene  in  order  to  avoid  loss  of  light-giving  products  from  the  gas.  The  anthracene  oil, 
saturated  with  naphthalene  (25  per  cent.)  can  be  utilised  as  such,  or  mixed  with 
ordinary  tar. 

According  to  U.S.  Pat.  968,509  of  1910,  naphthalene  can  be  separated  by  bubbling 
the  gas  through  an  aqueous  solution  of  picric  acid,  this  giving  rise  to  an  insoluble  naphtha- 
lene picrate,  from  which  the  naphthalene  can  be  distilled  by  means  of  steam,  the  picric 
acid  being  left. 

SEPARATION  OF  AMMONIA.  The  washing  of  the  gas  for  the  purpose  of  removing 
the  ammonia  may  be  effected  by  ordinary  water,  which  has  a  great  affinity  for  ammonia, 
or  by  the  dilute  ammonia  liquors  from  the  hydraulic  main  (1-2°  Be.),  but  not  with 
that  from  the  condenser,  which  is  too  concentrated  (7-8°  Be.).  The  most  common 
form  of  apparatus  used  for  this  washing  is  the  scrubber  or,  better  still,  the  "  Standard  " 
washer  -  scrubber. 

SCRUBBERS  are  usually  formed  of  a  series  of  coke-towers  through  which  water 
trickles  (Fig.  56).  The  gas  that  enters  the  bottom  of  the  first  tower  is  washed  with  dilute 
ammonia,  condensed  in  succeeding  tower?,  and  when  it  reaches  the  last  tower  it  is  washed 


PURIFICATION    OF    GAS 


45 


with  pure  water  which  dissolves  the  last  traces  of  ammonia  and  can  be  used  subsequently 
for  the  first  tower,  from  the  bottom  of  which  it  is  carried  off,  rich  in  ammonia,  by  small 
syphons.  These  towers,  which  are  of  cast-iron  sheets,  are  joined  in  twos  or  threes  in 
such  a  way  that  the  gas  is  conducted  from  the  top  of  the  first  tower  to  the  bottom  of  the 
second,  and  so  on.  The  interior  may  "be  fitted  simply  with  water  pulverisers,  or  it  may  be 
filled  with  coke,  chips  of  wood,  broken  bricks,  or,  what  are  more  efficient,  vertical  bundles 
of  sticks,  or  of  corrugated  and  toothed  iron  sheets. 

Scrubbers  are  1-3  metres  in  diameter  and  4-20  metres  in  height.  A  maximum  produc- 
tion of  1000  cu.  metres  of  gas  per  24  hours  requires  5-6  cu.  metres  of  scrubber,  the  gas 
taking  8-10  minutes  to  pass  through.  Before  entering  the  scrubber  the  gas  contains 
200^400  grms.  of  ammonia  per  100  cu.  metres,  whilst  afterwards  this  volume  contains 
only  1-10  grms. 

The  "STANDARD  "  washer-scrubber  consists  of  a  large  horizontal  fixed  cylinder  of 
iron-plate,  divided  into  seven  chambers  (Fig.  57).  This  cylinder  is  traversed  by  a  rotatable 


FIG.  55. 


FIG.  56. 


axis  carrying  seven  paddles  of  almost  the  same  diameter  as  the  chambers  and  each  consisting 
of  two  large  metal  plates  to  which  are  fixed  the  ends  of  superposed  wooden  laths  with 
spaces,  not  exactly  superposed,  between  (Fig.  58).  These  paddles  rotate  with  the  axis 
and  dip  into  water  which  fills  the  chambers  to  about  one-third  of  the  height  of  the  cylinder. 
The  pure  water  enters  chamber  VII  at  a  and  passes  from  chamber  to  chamber  until  it 
reaches  the  first,  the  walls  separating  the  chambers  being  successively  lower.  The  gas 
to  be  purified  moves  in  the  opposite  direction,  entering  chamber  I,  and  passing  between 
all  the  laths  of  the  paddle  from  the  centre  to  the  periphery,  then  descending  to  the  centre 
of  the  next  paddle  in  chamber  II  as  shown  by  the  arrows,  4  and  5,  again  issuing  at  the 
periphery,  passing  into  chamber  III,  and  so  on.  In  this  way  the  gas  is  perfectly  washed 
and  loses  also  part  of  its  C02  and  H2S.  The  water  leaves  chamber  I  with  a  density  of 
7-8°  Be. 

At  Monaco  the  ammonia  is  eliminated  in  the  dry  way  by  passing  the  gas  over  super- 
phosphate, which  fixes  it  and  then  serves  as  an  excellent  fertiliser  (with  7-8  per  cent,  of 
nitrogen) :  1000  kilos  of  superphosphate  are  sufficient  to  purify  32,000  cu.  metres  of  gas 
(with  3  per  cent,  of  NH3),  the  small  quantity  of  thiocyanate  (0-5-2-5  per  cent.)  which  it 
contains  having  no  injurious  action  on  [plants.  N.  Caro  (U.S.  Pat.  952,560,  March  22, 


46 


ORGANIC    CHEMISTRY 


1910)  cools  the  gas  from  coke  manufacture  to  20°  and  then  passes  it  through  a  solution 
of  ammonium  sulphate  of  29-35°  Be.  containing  5  per  cent,  of  free  sulphuric  acid  ; 
ammonium  sulphate  gradually  crystallises  out  and  the  gas  passes  off  free  from  ammonia. 
Generally,  however,  ammoniacal  liquors  are  distilled  with  lime  and  the  ammonia  fixed 
with  sulphuric  acid  (see  vol.  i,  p.  323).  Every  ton  of  coal  carbonised  yields  10-12  kilos 
of  commercial  ammonium  sulphate. 

FINAL  AND  COMPLETE  PURIFICATION  OF  GAS.  After  the  ammonia,  the 
following  gases  must  be  removed  :  H2S,  CO2,  HCN,  CS2,  thiocyanates,  sulphur  derivatives 
of  hydrocarbons,  &c.  This  is  especially  important  with  H2S  and  other  sulphur  compounds 
(about  1-1-5  per  cent,  by  volume  of  the  crude  gas),  since  they  partly  burn,  forming  SO2, 
and  partly  escape  unaltered  from  the  gas-jets,  decorations,  metal-work,  and  paintings  being 
discoloured  ;  also  the  poisonous  properties  of  these  compounds  are  considerable,  the  crude 
gas  containing  0-1-0-25  per  cent,  by  volume  of  hydrocyanic  acid.  The  test  employed  by 
large  consumers  to  detect  hydrogen  sulphide  is  very  rigorous  and  is  made  with  lead 
acetate  paper,  which  blackens  on  prolonged  exposure  to  impure  gas. 

The  final  purification  of  gas  has  been  in  use  ever  since  the  beginning  of  the  industry. 
In  1806  Clegg  purified  gas  partially  by  passing  it  through  milk  of  lime,  but  such  large 


volumes  of  liquid  were  required  that  their  preparation  was  difficult  and  the  purification 
was  not  complete.  He  then  proposed  the  use  of  powdered  slaked  lime,  which  fixes  carbon 
dioxide,  as  well  as  many  sulphur  compounds,  forming  calcium  sulphydroxide,  OH-Ca-SH  ; 
but  if  much  C02  is  present  the  sulphydroxide  is  decomposed  and  SH2  regenerated.  In 
1840  Mallet  suggested  the  use  of  manganese  oxide,  which  fixes  H2S  more  readily,  but  this 
method  did  not  give  good  results. 

At  the  present  time  use  is  largely  made  of  the  so-called  Laming  mixture,  which  is 
prepared  by  mixing  160  parts  of  lime,  180  of  sawdust  and  30  of  ferrous  sulphate  dissolved 
in  scarcely  sufficient  water  to  moisten  the  mass  ;  it  is  kept  turned  over  for  some  days  in 
the  air,  until  it  becomes  brown  owing  to  the  conversion  of  the  ferrous  sulphate  into  ferrous 
hydroxide  and  then  ferric  hydroxide,  calcium  sulphate  being  formed  at  the  same  time. 
The  latter  fixes  the  ammonium  salts  (such  as  have  not  been  already  separated),  while  the 
ferric  hydroxide  fixes  hydrogen  and  other  sulphides  :  2Fe(OH)3  +  3H2S  =  6H2O  +  F2S3 
(iron  sesquisulphide),  and  also  forms  iron  thiocyanate  from  hydrocyanic  acid  (i.e.  from 
ammonium  cyanide)  and  thiocyanates,  the  excess  of  lime  removing  the  carbon  dioxide. 

The  whole  of  the  iron  present  does  not  take  part  in  these  reactions,  but  when  the 
mixture  is  exhausted  it  can  be  regenerated  by  further  exposure  and  turning  in  the  air  for 
two  or  three  days,  the  whole  of  the  sulphur  being  liberated  : 

Fe2S3  +  3O  +  3H2O  =  2Fe(OH)3  +  3S. 

The  mass  can  be  thus  revivified  and  used  again  some  ten  or  more  times,  after  which 
it  is  rejected.  But  this  product  contains  35-50  per  cent,  of  free  sulphur,  10-15  per  cent, 
of  Prussian  blue,  1-4  per  cent,  of  ammonium  thiocyanate  and  1-4  per  cent,  of  ammonium 
sulphate,  and  nowadays  the  free  sulphur  is  often  extracted  by  carbon  disulphide,  while 


GAS    PURIFIERS 


47 


from  the  residue  cyanides  and  f errocyanides  can  be  obtained  ;  or  the  mass  is  first  extracted 
with  water  to  obtain  the  cyanides  and  the  ammonium  sulphate,  the  dried  residue  being 
used  in  place  of  pyrites  in  the  manufacture  of  sulphuric  acid  (see  vol.  i,  p.  650 ).1 

As  will,  however,  be  seen,  the  lime  takes  no  part  in  the  separation  of  the  hydrogen 
sulphide  (but  only  in  the  fixation  of  the  C02),  so  that,  in  the  last  few  years,  Laming 
mixture  has  been  replaced  by  hydrated  ferric  oxide  (minerals  such  as  limonite,  &c.)  mixed 
with  a  little  lime  and  sawdust  ;  by  using  natural  oxide  of  iron  alone,  the  reaction  becomes 
very  energetic,  the  mass  being  sometimes  almost  ignited.  These  mixtures  give  good 
results  and  are  placed  on  the  market  under  various  names  :  Deicke  mixture  with  66  per 
cent.  Fe2O3  and  Lux  mixture  with  51  [per  cent.  Fe203.  They  are' made  .by -mixing  the 
powdered  iron  residues  from  the  working  of  bauxite  with  soda  and  fusing  in  a  furnace, 
the  silicates  which  have  become  soluble  being  then  extracted  by  water  and  the  remaining 
ferric  hydroxide  mixed  with  double  its  volume  of  sawdust :  1  cu.  metre  of  this  "  Lux  " 
mixture,  at  an  initial  cost  at  the  Ludwigshafen  factory  of  about  15s.  per  ton,  purifies  more 
than  10,000  cu.  metres  of  gas,  whilst  natural  Silesian  ferric  oxide  costs  8-1 2s.  per  ton. 

The  purifying  mixture  is  arranged  in  several  layers,  all  of  which  are  traversed  by  the 
gas  (Fig.  59).  The  cover  to  the  chamber  is  water -sealed  (Fig.  60),  and  can  be  easily  raised 
by  means  of  a  crane  when  the  mass  is  to  be  removed  for  regeneration.  It  is  simpler  to 


FIG.  59. 


FIG.  60. 


use  a  single  layer  of  the  mass  50-60  cm.  deep,  the  gas'being  introduced  at  a  greater  pressure  ; 
it  is  then  easier  to  discharge  the  exhausted  mass  through  an  aperture  in  the  base  of  the 
reservoir.2  At  the  present  day  the  costly  labour  required  for  the  regeneration  is  avoided 
by  not  emptying  the  reservoir,  a  rapid  current  of  air  or  oxygen  being  passed  through  for 
several  hours,  this  operation  being  rapid,  complete  and  economical  ;  in  some  works,  how- 
ever, the  mass  is  kept  always  oxidised  by  mixing  about  2  per  cent,  of  air  with  the  gas 
before  passing  it  into  the  chamber. 

1  The  cyanogen  compounds  of  the  crude  gas  which  are  formed  from  ammonia  by  the  action  of  heat  and  cause 
corrosion  of  ironwork  are  best  separated  in  the  wet  way  by  Bueb's  process  (Ger.  Pat.  122,280,  May  1900),  in 
which,  before  being  freed  from  ammonia,  the  gas  is  passed  into  a  kind  of  "  Standard  "  containing  ammonia 
and  a  ferrous  sulphate  solution  of  20°  B6.  By  this  means,  ferrous  sulphide  first  gradually  separates 
[FeSO4  +  (NH4)2S  =  FeS  -i-  (NH^SOj],  and  is  then  slowly  converted,  under  the  action  of  ammonia  and 
hydrocyanic  acid,  into  an  insoluble  mass  composed  of  ammonium  ferrocyanide,  (NH4)4FeCy,,  and  of  a  ferrous 
ammonium  ferrocyanide,  (NH«),Fe(FeCy,)a.  This  sludge,  which  contains  all  the  cyanides,  corresponding  in 
amount  with  15  to  20  per  cent,  of  crystallised  potassium  ferrocyanide,  is  heated  to  render  insoluble  the  small 
quantity  of  cyanide  still  undissolved  and  to  drive  off  ammonium  carbonate,  and  is  then  passed  to  filter-presses ; 
the  nitrate  is  utilised  for  the  extraction  of  ammonium  sulphate,  while  the  cyanide  residue  is  heated  with  lime 
to  give  ammonia  and  calcium  ferrocyanide,  a  solution  of  the  latter  yielding  pure  sodium  ferrocyanide  when 
treated  wit  h  sodium  carbonate.  This  process  has  given  satisfactory  results  in  the  Turin  gasworks  and  many 
others  in  Europe,  but  is  already  beginning  to  lose  its  importance,  owing  to  the  discovery  of  new  synthetical 
methods  of  preparing  potassium  cyanide  (vol.  i.,  p.  435). 

a  This  exhausted  mass  is  often  utilised  for  the  sulphur  it  contains,  while  in  many  other  cases  the  cyanides, 
thiocyanates,  ferrocyanides,  &c.,  are  extracted  (see  vol.  i,  p.  650)  ;  it  is  also  sometimes  used  on  roads  as  a  weed- 
killer— cyanides  having  a  poisonous  action  on  plants — and,  finally,  it  has  been  proposed  as  a  nitrogenous  fertiliser 
(itcontainsonthe  average  5-6  per  cent,  of  nitrogen,  one-tenth  of  which  is  in  the  formof  ammonia  and  the  rest  as 
cyanide),  but  it  must  be  spread  on  the  naked  land  two  or  three  months  before  sowing  takes  place,  as  it  takes  time 
to  decompose  and  become  innocuous  to  vegetation. 


48 


ORGANIC    CHEMISTRY 


After  purification  the  gas  passes  through  large  meters  to  the  gasometers,  after  traversing 
a  glass  bell-jar  in  which  is  suspended  a  strip  of  moist  lead  acetate  paper  for  the  detection 
of  H2S. 

In  order  to  diminish  the  quantity  of  carbon  monoxide  in  gas,  L.  Vignon  (1911)  proposes 
to  heat  it  over  lime  and  with  steam,  by  which  means  non-poisonous  hydrocarbons  are 
formed. 

EXHAUSTERS.  To  regulate  the  pressure  of  the  gas  in  the  retorts  and  other  parts 
of  the  plant,  exhausters  are  placed  between  the  condensers  and  the  tar  separators,  or  even 
after  the  scrubbers.  Sometimes  a  bell-aspirator  is  used,  consisting  of  a  bell  immersed 
in  water  and  capable  of  being  raised  and  lowered  mechanically,  and  thus,  by  means  of 
suitable  valves  in  the  lid,  of  acting  both  as  exhauster  and  as  compressor.  There  are  also 
piston  exhausters,  others  similar  to  exhaustion  pumps  working  by  eccentrically  moving 
blades  (Beale  type),  &c.  The  so-called  Korting  injectors,  which  make  use  of  steam-jets, 
are  also  used  as  exhausters. 

PRESSURE  REGULATORS.  Since  the  development  of  gas  cannot  be  regulated 
in  the  retorts,  whilst  the  working  of  the  exhausters  is  uniform,  there  may  at  certain  times 

be  an  excess  pressure  generated,  espe- 
cially if  the  exhausters  cease  working 
owing  to  damage.  Hence,  so-called 
pressure  regulators  are  employed. 

To  give  an  idea  of  one  of  these 
simple  and  ingenious  devices,  it  is 
shown  in  Fig.  61  how  this  regulator 
is  combined  with  a  Korting  steam 
exhauster  :  d  is  the  exhauster,  which 
receives  steam  from  a  valved  tube, 
b,  connected  with  a  bell,  I,  with  a 
water-seal.  The  gas  from  the  tube  a 
passes  through  the  exhauster  to  the 
pipe  g.  If  an  excessive  pressure 
develops  in  the  main  a,  the  gas,  by 
means  of  the  tube  m,  raises  the  bell 

FIG.  61.  I,  which  in   its  turn   effects  a  wider 

opening  of    the  steam-valve  and  so 

increases  the  exhaustion.     If  the  pressure  exceeds  a  certain  limiting  value,  a  spring  valve 
or  partition  in  n  opens  automatically,  and  the  gas  discharges  also  by  n  into  the  pipe  g. 

GASOMETERS.  These  are  formed  of  large  sheet-iron  bells  fitting  one  in  the  other 
and  forming  a  perfect  water-seal  when  they  are  inverted  in  a  brick  and  cement  reservoir 
of  water.  To  economise  water,  the  reservoir  is  partially  filled  up  by  a  brickwork  cone 
(termed  the  "  dumpling  "),  starting  from  the  periphery  at  the  base  and  rising  towards 
the  centre,  as  shown  in  Fig.  62  ;  the  gas  exit  and  entry  pipes  project  a  little  above  the 
surface  of  the  liquid.  At  a  certain  point  (not  shown  in  the  figure)  these  two  pipes  can 
be  put  into  direct  communication,  so  that,  in  case  of  accident  to  the  gasometer,  the  gas 
can  still  be  led  to  the  mains  without  interrupting  the  work. 

To  economise  in  the  number  and  size  of  the  reservoirs  and  to  have  gasometers  of 
considerable  capacity,  so-called  telescopic  gas-holders  are  now  used.  These  consist  of 
several  concentric  bells  (five  or  six),  of  which  only  the  smallest  is  covered,  whilst  the  others 
are  caught  up  peripherally  during  the  rising  (or  filling  with  gas),  forming  a  water-seal  all 
round,  as  shown  in  Fig.  63.  In  order  that  the  bells  may  rise  centrally  they  are  furnished 
outside  with  pulleys  running  along  vertical  iron  guides.  The  pressure  of  gas  in  the  gaso- 
meter can  be  calculated  from  the  weight  of  the  bell  outside  the  water,  together  with  the 
surface  and  diameter  of  the  bell  itself. 

The  pressure  in  the  gasometer  or  mains  can  be  registered  automatically  by  placing 
them  in  communication  with  an  automatic  pressure-measure  like  that  shown  in  Fig.  64. 
In  this  the  gas  raises  or  lowers  a  bell  fitted  with  an  index  which  registers  the  different 
pressures  during  the  day  on  a  paper  wound  round  a  cylinder  rotated  once  in  24  hours 
by  clockwork. 

There  are  other  forms  of  pressure  indicators,  but  the  above,  although  old  (in  principle), 
is  still  largely  used,  being  simple  and  exact. 


GASOMETERS,    PRESSURE    REGULATORS     49 

In  order  to  avoid  the  serious  consequences  contingent  on  a  gasometer  reservoir  cracking 
or  leaking,  iron  reservoirs  built  above  ground  are  preferred  to-day,  the  slightest  escape 
being  then  observable  and  remediable  at  any  moment.  Such  a  suspended  telescopic 
gasometer  is  shown  in  Fig.  63. 

To  meet  the  enormous  daily  consumption  of  gas  in  large  cities  more  and  more  capacious 
gas-holders  are  required  —  sufficient  to  contain  3  or  4  days'  supply  and  so  avoid  the  incon- 

veniences of  an  interruption  of  work 
(from  damage,  stoppages,  &c.).  In 
Milan,  before  1908,  the  largest  of  the 
gasometers  (measuring  altogether  150,000 
cu.  metres)  had  a  capacity  of  26,000  cu. 
metres  ;  after  1908,  at  the  Bovisa  (Milan) 
wo*ks  a  new  one  was  brought  into  use 
which  holds  80,000  cu.  metres  and  cost 
little  less  than  £40,000.  The  firm  of 
Krupps  constructed  for  their  own  works 
a  gasometer  holding  37,000  cu.  metres  ; 
the  largest  at  Berlin  contains  80,000  cu. 
metres  ;  that  of  Chicago  120,000  cu. 
metres  ;  and  the  last  built  at  New  York 
has  a  cement  reservoir  and  a  capacity 
of  500,000  cu.  metres  ;  in  London  in 
1888  one  was  built  holding  230,000  cu. 
FIG.  62.  metres,  and  in  1892  another  with  six  bells, 

containing  345,000  cu.  metres  and  having 

a  diameter  at  the  base  of  95  metres.  Naturally  these  gas-holders  represent  large  amounts 
of  capital,  the  cost  even  for  capacities  of  30,000-40,000  cu.  metres  being  tens  of  thousands 
of  pounds.  Fig.  65  shows  diagrammatically  the  arrangement  of  a  gasworks  in  the  middle  of 
the  nineteenth  century. 

PRESSURE  REGULATORS  FOR  CONSUMERS.  In  order  that  consumers  may 
have  a  uniform  pressure  in  their 
pipes  and  obtain  regular,  non- 
oscillating  flames  with  a  normal 
consumption  of  gas,  it  is  necessary 
to  use  pressure  regulators  where  the 
principal  mains  .leave  the  works, 
these  regulating  the  pressure  auto- 
matically even  when  the  consump- 
tion is  at  its  maximum  or  minimum. 
Since  gas  is  lighter  than  air,  the 
pressure  is  regulated  more  easily 
and  the  flow  facilitated  by  con- 
structing the  works  at  the  lowest 
point  of  the  town.  In  the  gas-holder 
the  pressure  is  usually  15  cm.  of 
water,  whilst  in  the  mains  it  is 
about  2  cm. 

A    regulator   as    ingenious    as   it 


is  simple  was  devised  by  Clegg 
and  is  in  general  use  at  the  present 
time  (Fig.  66).  In  a  metal  cylinder,  a,  filled  with  water,  a  bell,  b,  can  be  raised  or 
lowered  according  as  the  gas  supplied  at  /  has  a  greater  or  less  pressure.  The  pressure 
in  the  bell  can  be  varied  by  altering  the  size  of  the  aperture  in  tube  /  by  which  the  gas 
is  admitted.  The  orifice  i  at  the  upper  end  of  /  can,  indeed,  be  closed  to  a  greater 
or  less  extent  by  a  metal  cone,  e,  attached  by  a  chain  to  the  bell,  with  which  it  rises  if  the 
pressure  is  excessive  —  thus  diminishing  i  and  hence  the  pressure  in  the  bell  —  or  falls  if  the 
pressure  diminishes  too  much,  more  gas  then  entering  through  i  and  the  normal  pressure 
being  thus  re-established.  This  normal  pressure  can  be  fixed  according  to  the  needs  of 
any  particular  time,  by  placing  on  the  bell  weights,  d,  calculated  tp  give  the  required 


FIG.  03. 


50 


ORGANIC    CHEMISTRY 


pressure.     By  means  of  this  simple  regulator  the  gas  issues  from  h  at  a  constant  pressure 
and  can  be  immediately  passed  into  the  mains. 

In  general,  however,  the  pressure  is  not  the  same  in  all  the  mains,  but  diminishes  as 
the  distance  from  the  works  increases.  But  it  is  not  advisable  to  have  the  pressure  too 
high,  since  the  losses  due  to  unavoidable  leaks  in  the  pipes  are  greater  the  higher  the 
pressure,  and  the  latter  is  usually  maintained  at  15-20  mm.  of  water  at  the  points  most 
remote  from  the  works. 

In  order  to  render  the  distribution  of  the  gas  to  considerable  distances  more  economical, 
attempts  have  been  made  to  employ  a  pressure  of  1-1-5  atmos.  on  the  gas,  the  latter 
being  preferably  from  vertical  retorts  and  as  free  as  possible  from  naphthalene. 

GAS-METERS.  These  are  used  to  measure  the  gas  in  factories  and  private  houses, 
since  nowadays  payment  is  according  to  the  volume  con- 
sumed and  not  according  to  the  number  of  burners,  as  was 
once  the  custom.  Dry  meters  have  disappeared  almost 
everywhere,  general  use  being  made  of  the  water  meters 
devised  by  Clegg  and  by  Malam,  and  since  improved  so 
that  they  are  now  perfect  gas-measurers.  The  principle 
on  which  their  working  is  based  is  shown  clearly  by  Fig.  67, 
representing  an  old  form  of  the  Malam  meter.  A  cylindrical 
chest,  X,  half -filled  with  water,  contains  a  drum  rotatable 
about  a  horizontal  axis  and  divided  into  four  chambers, 
A,  B,  C,  and  D,  communicating  at  the  centre  by  means  of 
the  narrow  slits  b,  and  opening  into  the  periphery  at  X  by 
the  slits  c.  The  gas  is  led  by  the  tube  a  into  the  central 
part  of  the  drum  and,  in  the  position  shown  in  the  figure, 
communicates  only  with  the  slit  b  of  the  chamber  D ; 
the  latter  is  thus  slowly  filled  with  gas  (which  has  a 
slight  pressure),  the  drum  being  thereby  raised  and  water 
caused  to  escape  from  c.  Thus  the  chamber  D  becomes 
filled  with  gas  in  the  position  occupied  by  C,  which  has 
allowed  its  gas  to  escape  gradually,  the  rotation  indicated 
by  the  arrow  having  caused  it  to  fill  with  water  through 
the  corresponding  slit,  b.  Subsequently  the  gas  fills  the  next 
chamber,  A,  which  displaces  Z),  and  so  on.  The  gas  passing 
through  this  apparatus  proceeds  along  the  tube  K  to  the 
consumer's  burners.  If  all  the  taps  are  turned  off,  the 
drum  cannot  allow  the  gas  to  escape  from  it,  and  hence 
does  not  turn.  The  chambers  have  definite  volumes,  and 
if  the  axis  of  the  drum  is  connected  with  a  suitable  mag- 
nifying apparatus  the  number  of  turns  of  the  drum  and 
consequently  the  volume  of  gas  traversing  it  can  be 
measured. 

This  apparatus  exhibits  many  structural  defects  which 
cause  inaccurate  measurements,  and  are  now  avoided  by 

the  meter  shown  in  Figs.  69,  70,  and  71.  Here  the  drum  has  transverse  walls  which 
are  inclined  and  not  parallel  to  the  axis  (Fig.  68,  V,  W),  so  that  the  filling  with 
the  gas  or  water  and  the  discharge  take  place  gradually  and  do  not  cause  oscillation 
of  the  flame.  The  gas  enters  by  the  tube  I  into  the  division  k  (Figs.  69  and  70)  and 
passes  into  E  through  the  orifice  i,  regulated  by  a  floating  valve,  h.  Thence  the  gas 
goes  to  the  anti-chamber,  B,  by  way  of  the  elbow-tube,  nx,  opening  above  the  level, 
W,  of  the  water.  The  aperture,  o,  connecting  the  tube,  x,  with  the  anti-chamber  is  large 
enough  to  admit  of  the  passage  of  the  axis  of  the  drum,  but  remains  closed  owing  to  the 
level  of  the  water  being  above  it.  As  the  slits  of  the  drum  gradually  present  themselves, 
the  gas  enters  successively  the  chamber  of  the  drum  from  one  side  and  issues  at  the  other 
into  the  outer  casing,  A,  then  passing  through  the  tube  g  to  the  gaspipes.  Water  (or  better, 
a  mixture  of  water  and  glycerine,  which  does  not  freeze)  is  introduced  by  the  opening  V, 
the  level  of  the  liquid  being  fixed  by  the  tube  n,  so  that  the  flow  of  gas  through  the  valve  i, 
is  regulated ;  the  excess  of  water  is  discharged  by  the  tube  n  and  passes  into  the  reservoir,  m, 
thence  by  the  tube-J  to  S,  the  orifice,  u,  of  which  is  left  open  while  the  water  is  being  added, 


FIG.  64. 


GAS-METERS 


51 


The  axis  of  the  rotating  drum  has,  at  one  end,  a  continuous  screw,  a  (Fig.  71 ),  which  moves 
a  toothed  wheel,  a  ;  the  latter,  by  means  of  the  axle,  e,  produces  rotation  of  a  clockwork 
arrangement  in  F,  so  constructed  that  one  wheel  indicates  litres  and  tens  of  litres,  another 
cubic  metres,  a  third  tens  of  cubic  metres,  and  a  fourth  hundreds  of  cubic  metres. 


FIG.  65. 

C  =  horizontal  retorts ;  B  =  hydraulic  main  for  separating  the  tar ;  D  =  tubes  for  cooling 
gas  ;  O  =  washing  towers  (scrubbers) ;  M  =  chambers  containing  Laming  mixture  for  purifying  ; 
O  =  single-lift  gasholder ;  S&i  =  entry  and  exit  gaspipes. 


FIG.  66. 


FIG.  67. 


FIG.  68. 


The  last  few  years  have  seen  the  successful  introduction  of  the  new  dry  meters  and  of 
automatic  meters,  of  which  alone  Berlin  contained  84,000  in  1905.  By  placing  a  10-pfennig 
piece  into  one  of  these  automatic  meters,  500  litres  of  gas  are  supplied.  In  1906  Berlin 
had  in  addition  191,000  ordinary  meters. 

YIELD,  VALUE,  AND  PRICE  OF  GAS.  These  vary  with  the  nature  of  the  coal  used 
and  with  the  conditions  of  carbonisation.  In  the  large  gasworks  of  the  principal  European 


52 


ORGANIC    CHEMISTRY 


towns  the  yields  usually  vary  between  the  following  limits  :  coke,  63-76  per  cent.,  more 
commonly  69-71  per  cent.  ;  tar,  4-6  per  cent.  ;  ammonia  liquors,  9-8-12-5  per  cent.  ; 
gas,  25-31  cu.  metres  (of  sp.  gr.  0-360-0-480).  At  Berlin  every  ton  of  coal  yielded  on 
the  average  287-3  cu.  metres  in  1900,  305  in  1901,  320  in  1902,  and  324-4  in  1904,  in  addition 
to  690  kilos  of  coke,  54  kilos  of  tar,  and  120  kilos  of  ammonia  liquors. 

In  many  gasworks  at  the  present  day,  instead  of  installing  new  plant,  increased  con- 
sumption of  gas  is  met  by  mixing  with  water-gas  (or  blue  gas),  and  as  the  calorific  value  of 
this  is  only  about  one-half  that  of  coal-gas,  benzene  or  heavy  petroleum  vapours  are  also 
added.  Water-gas  generators  give  a  rapid  production,  do  not  form  naphthalene  or  tar, 
and  yield  a  gas  costing  less  than  half  that  of  ordinary  gas  ;  this  is,  however,  very  rich  in 
carbon  monoxide,  which  has  caused  numerous  cases  of  poisoning  in  the  United  States,  so 
that  the  medical  men  are  now  (1910)  instituting  a  campaign  to  forbid  the  use  of  water- 
gas.1 

The  cost  of  manufacture  of  bituminous  coal-gas  varies  with  the  different  factors 
affecting  its  production,  especially  with  the  size  of  the  works,  the  prices  of  coal  and  labour 
and  the  greater  or  less  completeness  with  which  the  secondary  products  (ammonia, 


FIG.  69. 


FIG.  70. 


cyanides,  sulphur,  tar,  &c.)  are  utilised.  In  Berlin  the  mean  cost  of  manufacture  seems 
to  be  less  than  0-75^.  per  cubic  metre,  while  at  Milan  it  is  about  0-85d.2  Gas  varies  in 
price  in  different  towns  from  1-15  to  3-8d.  per  cubic  metre  (32-100d.  per  1000  cu.  ft.)  ;  in 
Paris  it  is  1-9,  in  Milan  1-25,  in  Oneglia  2-9,  in  Messina  3-2,  in  Venice  3-5,  in  Catania  3-8, 
and  in  Naples  3-ld.  per  cubic  metre.  [In  England  often  much  cheaper. — Translator.'] 

STATISTICS.  The  consumption  of  lighting  gas  (subject  to  tax)  in  Italy  in  1902  was 
139  million  cu.  metres,  and  exempt  from  taxation  (for  engines,  &c.)  56  million  cu.  metres. 
In  1898  the  total  production  was  198  million  cu.  metres  ;  in  1902,  211  million  cu.  metres  ; 
in  1908,  308  million  cu.  metres  obtained  from  1  million  tons  of  coal,  with  a  yield  of  51,000 

1  Water-gas,  reinforced  with  benzene  and  mineral  oils,  costs  about  15  per  cent,  more  than  ordinary  gas  but 
presents  various  advantages  :  without  expensive  plant,  a  production  higher  than  the  capacity  of  the  works 
can  be  supplied  ;  part  of  the  coke  is  utilised,  over-production  and  consequent  lowering  of  the  price  being  thus 
avoided  ;  less  consumption  of  coal  for  gas  and  hence  less  danger  of  rise  in  price  of  coal ;  less  labour  ;  rapid  pro- 
duction even  in  the  event  of  a  strike.  In  England  over  500,000,000  cu.  metres  are  produced  per  annum.  4  grins, 
of  benzene  per  cubic  metre  of  gas  increase  the  luminosity  by  one  candle.  A  mixture  of  two-thirds  of  illuminating 
gas  and  one-third  of  water-gas  gives  a  luminosity  of  sixteen  candles  when  treated  with  about  40  grms.  of  benzene, 
the  cost  of  the  latter  beins  about  0-6d.  per  cubic  metre. 

*  We  give  here  an  approximate  industrial  balance-sheet  referred  to  one  ton  of  coal  and  to  the  conditions  employed 
in  the  Milan  gasworks  : 

(a)  Receipts  :  264  cu.  metres  of  gas  (290  actually  produced,  less  9  per  cent,  for  escapes  and  consumption  in 
works)  at  0-13  lira  gives  34-32  lire  ;  700  kilos  of  coke,  22-40  lire  ;  45  kilos  of  tar,  1-35  lira  ;  9  kilos  of  ammonium 
sulphate,  2-70  lire  ;  cyanides,  graphite,  slag,  ashes,  0-06  lira.  Total  receipts,  60-83  lire. 

(6)  Expenditure  :  1  ton  of  coal,  30  lire  ;  coke  for  heating  the  furnaces  (160  kilos),  5-12  lire  ;  purifying  and 
Laming  mixtures,  0-37  lira  ;  sulphuric  acid  and  expenses  for  ammonium  sulphate,  1-44  lira  ;  salaries  and  wages, 
10-58  lire;  taxes,  0-67  lira  ;  fire  insurance,  0-091  lira  ;  workmen's  insurance,  0-175  lira  ;  general  expenses,  1-10  lira  ; 
maintenance  of  works,  private  and  public  expenses,  new  plant,  3  lire ;  maintenance  of  meters  and  sundry  other 
expenses,  0-090  lira  Total  expenditure,  53-23  lire. 

Net  profit,  about  7-60  lire. 


GAS    STATISTICS:     TESTING  53 

tons  of  tar  and  709,000  tons  of  coke  ;  in  1909  the  gas  produced  in  Italy  in  198  works 
amounted  to  318  million  cu.  metres  having  a  value  of  two  millions  sterling.  At  Milan 
in  1903,  40  million  cu.  metres  of  gas  were  produced,  in  1905  about  47  million  cu.  metres, 
in  1907  almost  58  million  cu.  metres,  and  in  1908  about  61  million  cu.  metres  (7000 
incandescent  gas  lamps  being  used  for  public  lighting).  Paris  alone  consumes  annually 
350  million  cu.  metres,  two-thirds  by  night  and  one-third  by  day  (for  engines,  &c.),  and 
Berlin  in  1908  about  250  million  cu.  metres  (in  this  city  gas  manufacture  is  municipalised, 
and  the  community  draws  an  annual  profit  of  about  £350,000).  From  1886  to  1904,  the 
consumption  in  Brussels  increased  from  15  to  39  million  cu.  metres,  that  is,  from  85  to 
204  cu.  metres  per  head  per  annum. 

The  various  sources  of  light  used  to  supply  the  needs  of  Paris  in  1889  were  in  the 
following  proportions  :  wax,  tallow,  stearin,  1-6  per  cent.  ;  vegetable  oils,  4-5  per  cent.  ; 
petroleum,  17-7  per  cent.  ;  electricity,  18-9  per  cent.  ;  gas,  57-3  per  cent.  In  Berlin, 
where  the  consumption  of  gas  in  1889  was  117  million  cu.  metres  and  where  54,000  tons 
of  petroleum  were  used  for  lighting  purposes,  the  proportions  were  as  follows  :  petroleum, 
50  per  cent.  ;  gas,  47  per  cent.;  electricity,  3  per  cent. 

England  carbonises  annually  1 6  million  tons  of  coal 
(in  1906)  to  procure  4500  million  cu.  metres  of  illumi- 
nating gas.  Germany,  in  1896,  distilled  2,727,000  tons 
and  consumed  also  one  million  tons  of  petroleum, 
equivalent  to  2000  million  cu.  metres  of  gas  ;  in  1905, 
310  large  gasworks  used  4,500,000  tons  of  coal,  of 
which  one-fourth  was  imported  from  England,  and 
700  other  small  works  carbonised  a  total  of  1,000,000 
tons  ;  in  1910,  the  total  coal  used  for  gas  in  Germany 
amounted  to  about  6,500,000  tons,1  one-half  the  total 
production  being  used  for  gas-engines,  of  which  there 
were  35,000  developing  170,000  horse-power  (in  1898 
there  were  about  22,000  gas-engines  using  33  per  cent, 
of  the  total  gas  produced). 

In  the  United  States  1640  million  cu.  metres  of  lighting  gas  were  produced  in  1907, 
the  value  being  £3,200,000.  In  1909  the  United  States  contained  1296  gasworks  with  a 
capital  of  £183,107,400,  the  number  of  officials  being  13,515  and  the  number  of  operatives 
37,215.  The  output  of  gas  and  other  products  was  valued  at  £33,400,000,  and  53  per 
cent,  of  the  total  production  consisted  of  water-gas.  In  Japan  the  industry  was  Started 
only  in  1901,  and  in  1907  the  production  had  reached  44  million  cu.  metres. 

The  manufacture  and  nature  of  air  gas,  producer  gas,  suction  gas,  Riche  gas,  water  gas, 
&c.,  are  described  in  vol.  i  (p.  393). 

PHYSICAL  AND  CHEMICAL  TESTING  OF  ILLUMINATING  GAS.  As  regards 
the  determination  of  CO,  CO2,  N,  and  O,  Orsat's  apparatus  (see  vol.  i,  p.  375)  gives  good 
results.  The  estimation  of  hydrogen  is  effected  with  the  ordinary  Hempel  burette  or 
simply  by  determining  the  diminution  in  volume  of  the  gas  after  passing  it  through  a 
capillary  tube  containing  palladinised  asbestos  heated  at  about  100°  (see  vol.  i,  p.  137). 
Then  comes  the  determination  of  unsaturated  and  aromatic  hydrocarbons,  which  are  all 
absorbed  by  fuming  concentrated  sulphuric  acid,  the  gas  being  measured  before  and 
after  the  absorption  in  the  Hempel  burette  (the  gas  being  washed  with  potash  after  the 
absorption).  The  methane  is  estimated  by  exploding  the  gas  remaining  in  the  burette 
with  a  known  volume  (in  excess)  of  oxygen  by  means  of  an  electric  spark,  2  vols.  of  the 
gaseous  mixture  (gas  +  oxygen)  disappearing  for  every  1  vol.  of  methane,  according  to 
the  equation  : 

CH4  +  2O2  =  C02  +  2H20. 
1  vol.      2  vols.      1  vol.     condenses 

1  For  the  production  of  gas  in  Berlin  352,000  tons  of  German  coal  and  397,000  tons  of  English  coal  were  used  ; 
at  the  English  ports  the  coal  cost  8s.  l%d.  per  ton  in  1904  and  11s.  4Jd.  in  1909.  The  cost  of  transport  from  the 
English  mines  to  Berlin  amounted  to  7*.  3id.  per  ton,  whilst  from  the  German  mines  at  Ruhr  to  Berlin  it  exceeded 
8s.  lid.  At  the  gasworks  in  Berlin  the  English  coal  cost  16a.  3d.  per  ton,  and  the  German  (from  Silesia)  20*.  4d. 
per  ton.  In  Germany  44  million  cu.  metres  of  gas  were  consumed  in  1859,  350  million  cu.  metres  in  1879,  about 
500  million  cu.  metres  in  1889,  almost  1200  million  cu.  metres  in  1899,  and  about  1800  million  cu.  metres  in 
1908,  there  being  1200  factories,  representing  a  capital  of  £80,000,000  (for  Berlin  alone  £12,000,000  and  for  Munich 
£640,000).  In  1880  only  one-half  of  the  gasworks  were  municipalised,  and  in  1909  two-thirds,  the  profit  amounting 
t<>  8  to  13  per  cent,  on  the  capital. 


54 


ORGANIC    CHEMISTRY 


To  estimate  the  ammonia  in  the  purified  gas,  200  litres  of  it  are  passed  through  10  c.c. 
of  an  N/10  solution  of  hydrochloric  acid,  the  excess  of  which  is  subsequently  determined 
by  titration. 

The  determination  of  the  total  sulphur  compounds  can  be  simply  effected,  according 
to  F.  Fischer,  as  follows  :  About  50  litres  of  the  gas  (measured  by  a  good  meter)  are 

burned  in  a  small  Bunsen  burner,  g  (Fig.  72), 
in  the  drawn-out  bulb,  A,  of  a  bulb-con- 
denser arranged  as  shown.  All  the  sulphur 
of  the  sulphur  compounds  burns,  forming 
sulphurous  and  sulphuric  acids  with  the 
water  from  the  combustion  of  the  gas,  this 
condensing  in  the  bulbs  of  the  condenser 
and  being  collected  at  the  bottom  in  a 
beaker  by  means  of  the  tube  e.  The  com- 
bustion is  regulated  so  that  gas  containing 
4-6  per  cent,  of  oxygen  escapes  at  o.  Water 
FIG.  72.  enters  the  condenser  at  z  and  leaves  at  n. 

At  the  end  of  the  operation,  the  bulbs  are 

rinsed  out  with  water  and  the  sulphurous  acid  in  the  liquid  oxidised  by  means  of  pure, 
neutral  hydrogen  peroxide  solution  ;  the.  sulphuric  acid  is  then  titrated  with  N/10  sodium 
hydroxide  solution.  If  the  sulphuric  acid  is  estimated  gravimetrically  with  barium 
chloride,  the  oxidation  of  the  sulphurous  acid  must  be  effected  with  hydrogen  peroxide 
free  from  sulphates.  The  quantity  of  sulphuric  acid  found 
gives  the  total  sulphur-content  of  the  gas.  A  well -purified  gas  f 
contains  less  than  0-5  grin,  of  sulphur  per  cubic  metre. 

The  hydrogen  sulphide  is  estimated  separately  by  passing  a 
known  volume  of  the  gas  through  ammoniacal  silver  nitrate 
solution,  which  is  afterwards  acidified  with  a  little  nitric  acid, 
the  silver  sulphide  being  filtered  off,  washed,  dried  at  100°,  and 
weighed. 

The   calorific   power   can    be   determined  fairly  rapidly  by 
means  of  the  Junker  calorimeter  (Fig.  73,  section,  and  Fig.  74), 
which  consists  of  a  metal  cylinder,  C  (the  letters  refer  in  all 
cases  to  Fig.  74),  which  is  mounted  on  three  feet,  and  inside 
which  a  known  volume  of  the  gas  is  burned  by  means  of  the 
Bunsen  burner,  n.    The  hot  products  of  combustion  pass  several 
times  up  and  down  the  calorimeter  and  issue  at  the  outlet  S, 
which  is  furnished  with  a  valve  and  also  regulates  the  air- 
draught.     Passing  in  a  direction  opposite  to  that  of  the  gases 
of  combustion  and  in  alternate  adjacent  chambers  is  a  current 
of  water  which  enters  by  w  the  small  reservoir  m,  the  excess 
being  carried  off  by  the  overflow,  6,  while  a   regular   stream 
passes  through  the  tap  e  (furnished  with  an  indicator)  into  the 
calorimeter  at  a  temperature  given  by  the  thermometer  x,  and 
flows  away  at  c  at  a  higher  temperature,  shown  by  the  ther- 
mometer y.      When  the  combustion  is  started,  the  entry  of 
water  is  regulated  by  means  of  e,  so  that  the  thermometers, 
x  and  y,  indicate  a  temperature  difference  of  10-20°  ;    when 
the  flow  of  both  gas  and  water  is  constant,  the  thermometer  y 
soon  shows  a  constant  temperature. 

The  gas  is  measured   by  the  meter,  G,  and   then   passes 

through  the  regulator,  P,  to  the  Bunsen  burner,  n,  which  is  drawn  from  the  calorimeter  to 
be  lighted  and  is  then  pushed  in  again  to  the  height  q  (about  6  in.  up).  If  the  apparatus 
is  in  order,  no  water  should  fall  from  d  into  the  cylinder,  v. 

When  water  is  discharging  from  b  and  from  c,  and  the  thermometer  remains  stationary, 
as  soon  as  the  index  of  the  meter  reaches  the  zero  mark  or  a  definite  number  of  litres, 
the  rubber  tube  c  is  instantly  placed  from  t  into  V,  which  is  a  graduated  cylinder  placed 
quite  close  to  the  discharge-funnel,  t.  In  the  cylinder  V  is  collected  all  the  water  which 
is  discharged  during  the  combustion  of  a  definite  volume  of  gas  (in  the  proportion  of 


FIG.  73. 


CALORIFIC    POWER    OF    GAS 


55 


100  to  200  litres  of  illuminating  gas  or  400  to  800  litres  of  suction  gas  or  Dowson  gas  per  hour). 
Exactly  at  the  moment  when  the  meter  indicates  the  volume  of  gas  fixed  upon,  the  rubber 
tube,  c,  is  removed  from  V  to  t.  During  the  course  of  the  experiment  the  small  variations 
in  the  indications  of  the  thermometer  y  are  noted  at  intervals,  the  mean  temperature 
being  subsequently  determined. 

The  graduated  cylinder,  v,  contains  the  condensed  water  (a  c.c.)  formed  during  the 
combustion  of  the  gas,  and  this,  in  condensing,  has  given  up  to  the  water  of  the  calori- 
meter a  certain  quantity  of  heat,  which  must  be  subtracted  before  calculating  the  net 
calorific  power.  The  gross  calorific  power,  U,  expressed  in  calories  per  cubic  metre,  is 

A.  T.  1000 
calculated  by  means  of  the  formula  :     U  =  — ,  where  A  indicates  the  quantity 

of  water  in  litres  collected  in  V,  and  Q 
the  volume  of  gas  burned.  If,  for 
example,  Q  =  3  litres,  A  =  0-900,  T  = 
18°  (that  is,  26-77°,  the  mean  of  six 
readings  of  the  thermometer  y,  less 
8-77°  shown  by  the  thermometer  x  to 
be  the  temperature  of  the  water  enter  - 

0-900.18.1000 

ing  at  e),  we  have  U  =   

=  5400  Calories  per  cubic  metre  of 
gas.  In  cases  where  the  gas  is  used  in 
engines  or  other  apparatus  from  which 
the  products  of  combustion  issue  at  a 
temperature  above  65°,  the  water-vapour 
does  not  condense  and  the  gross  calorific 
power  must  be  diminished  by.  the  heat 


FIG.  74. 


due  to  the  condensation  of  the  water -vapour  produced  by  the  combustion  of  the  gas  in 
the  calorimeter.  From  U  must  hence  be  subtracted  a  value  obtained  by  multiplying  by 
60  the  number  of  c.c.  of  water  condensing  during  the  combustion  of  10  litres  of  gas. 
This  net  calorific  power,  U1,  is,  for  illuminating  gas,  usually  10  per  cent,  lower  than  the 
gross  calorific  power,  U. 

The  specific  gravity  sometimes  serves  to  test  the  constancy  in  composition  of  gas  or 
to  compare  two  different  gases  ;  it  also  gives  a  rough  idea  of  illuminating  power,  since 
the  specific  gravities  of  the  more  highly  light-giving  hydrocarbons — acetylene  (0-920), 
ethylene  (0-976),  propylene  (1-490),  and  benzene  (2-780) — are  higher  than  those  of  the 
non-luminous  components — hydrogen  (0-0695),  methane  (0-559),  &c.  The  specific  gravity 
can  be  determined  rapidly  and  exactly  with  the  Bunsen  effusiometer  (see  vol.  i,  p.  39). 

ILLUMINATING  POWER.  There  is  no  absolute  measure  of  the  power  of  different 
sources  of  light,  but  these  can  be  compared  when  a  conventional  unit  has  been  chosen. 

This  standard  of  light  has  been  differently  chosen  in  different  countries  and  has  been 


56  ORGANIC    CHEMISTRY. 

continually  modified.  Thus  in  England  spermaceti  candles  are  used  of  such  size  that 
six  weigh  1  lb.,  while,  when  burned,  they  lose  7-78  grms.  (120  grains)  per  hour  with  a 
flame  45  mm.  in  height.  In  Germany  in  1872  a  paraffin  candle  20  mm.  in  diameter 
was  employed,  the  wick  having  24  threads  and  weighing  0-668  grm.  per  metre  and  the 
flame  being  50  mm.  high  ;  six  of  these  candles  weighed  1  lb.  Use  is  now  made  in  Germany 
of  the  more  rational  Hefner-Alteneck  lamp,  fed  with  a  liquid  of  constant  composi- 
tion, namely,  amyl  acetate,  the  compact  wick,  8  mm.  in  diameter,  protruding  25  mm. 


FIG.  75. 


FIG.  76. 


from  the  metallic  sheath  holding  it  ;  the  flame  is  40  mm.  high.  In  France  and  Italy 
the  Carcel  lamp  is  used,  this  consuming  42  grms.  of  purified  colza  oil  per  hour  and  having 
a  wick  which  is  23-5  mm.  in  diameter,  is  formed  of  75  threads,  and  weighs  3-6  grms. 
per  10  cm. 

The  relative  values  of  these  different  units  is  as  follows :    1  Carcel  =  9-600  English 
candles  (spermaceti)  =  8-768  German  candles  (paraffin)  =  10-526  Hefner-Alteneck  flames. 

The  luminous  unit  being 
fixed,  different  sources  of  light 
and  their  illuminating  powers 
can  be  compared  by  means  of 
photometers.  Of  these,  the  one 
most  largely  used  is  that  of 
Bunsen,  which  is  based  on  the 
principle  that  the  intensity  of 
light  produced  on  a  definite 
surface  by  a  source  of  light  is 
inversely  proportional  to  the 
square  of  the  distance.  If  the 
distance  between  the  source  of 
light  and  the  surface  illuminated 
is  trebled,  the  intensity  of  the 
illumination  is  diminished  to 
one-ninth  of  its  previous  value. 
The  luminosities  of  two  flames, 
/  and  /!,  which  illuminate  equally  a  given  screen  and  are  at  the  respective  dis- 
tances, L  and  Ll9  from  it,  are  directly  proportional  to  the  squares  of  these  distances  : 
/  :  /j  —  Lz :  Lj2,  and  if  II  is  the  unit  of  measurement,  the  intensity  of  the  other  source 

L2 

of  light  will  be  :  /  =  -=-'      The  Bunsen  photometer  (Fig.  75)  consists  of  a  horizontal  iron 

L\ 

photometer  bench  3  metres  long  and  divided  decimally  (into  half -centimetres  or  milli- 
metres) ;  at  one  end  is  placed  the  comparison  electric  or  candle  lamp  or  the  Carcel  lamp, 
the  consumption  of  oil  in  which  is  regulated  by  a  small  pump  actuated  by  a  clockwork 
mechanism,  weighing  on  a  balance  the  consumption  in  a  given  time  (indicated  by  a  bell) 
— this  corresponding  with  42  grms.  of  oil  per  hour.  A  screen  of  paper  can  be  moved 
backwards  and  forwards  along  the  bench  and  normally  to  it,  the  middle  of  the  screen 
being  rendered  translucent  by  means  of  a  grease  spot  (spermaceti)  ;  at  the  other  end 


FIG.  77. 


0  I  L  -  G  A  S  57 

of  the  bench  is  placed  the  light  to  be  examined.  When  the  screen  is  equally  illuminated 
on  its  two  faces,  the  grease-spot  is  no  longer  perceptible.  The  intensities  of  the  two 
sources  of  light  are  then  proportional  to  the  squares  of  their  distances  from  the  screen. 

The  measurement  is  made  in  a  dark  room  and,  in  order  to  render  more  evident  the 
disappearance  of  the  spot  on  the  two  surfaces,  the  screen  is  placed  between  two  mirrors 
arranged  at  an  angle  (Fig.  76).  An  improvement  on  the  Bunsen  photometer  has  been 
made  by  Lummer  and  Brodhun,  who  substitute  for  the  screen  with  the  grease-spot  a 
closed  box,  h  (Fig.  77),  in  which  are  two  opposite  circular  apertures,  these  illuminating  the 
two  faces  of  a  white  screen,  /,  by  means  of  light  from  the  standard  lamp,  and  that  to  be 
tested  placed  at  the  two  extreme  ends  of  the  photometer  bench.  By  means  of  a  system 
of  prisms,  A  B,  the  two  faces  of  the  white  screen  reflect  the  light  on  to  two  concentric 
zones  of  the  field  of  the  eye-piece,  r.  When  the  two  faces  of  the  screen  are  equally  illumi- 
nated, the  two  zones  of  the  field  also  appear  uniformly  lighted  .x 


OIL-GAS 

In  cases  where  the  installation  of  a  plant  for  the  carbonisation  of  coal  would  be 
inexpedient,  owing  to  the  small  consumption  of  illuminating  gas,  it  may  be  convenient 
to  prepare  oil-gas  by  dropping  into  a  red-hot  retort  (see  later,  "  Cracking  "  Process  in 
the  Petroleum  Industry)  fatty  residues,  tar  oils,  resins,  and  petroleum.  This  destruction 
by  heat  produces  a  gas  which  can  be  readily  compressed  without  separation  of  liquid, 
and,  enriched  with  25  per  cent,  of  acetylene,  is  used  for  the  illumination  of  railway  carriages. 
Oil-gas  can  also  be  prepared  easily  and  abundantly  by  dropping  oil  into  gasogens  con- 
taining red-hot  coke. 

As  early  as  1815  public  lighting  with  oil-gas  was  attempted  (Liverpool  used  it  for  some 
years),  but  it  was  only  after  1860-1870  that  this  industry  assumed  importance.  From 
100  kilos  of  lignite  paraffin  oil  are  obtained  60  cu.  metres  of  gas,  and  with  a  consumption 
of  35  litres  of  the  gas  per  hour,  7-5  normal  candles  (German)  are  obtained  ;  its  illuminating 
power  is  four  times  as  great  as  that  of  ordinary  lighting  gas.  If  a  greater  yield  of  the 
gas  is  obtained,  it  loses  in  illuminating  power.  The  purification  of  oil -gas  is  carried  out 
in  practically  the  same  way  as  that  of  coal-gas.  Mineral  oil  for  gas  and  for  engines  is 
produced  in  large  quantities  in  Galicia,  where  it  is  sold  for  less  than  19-5d.  per  cwt.  (4  lire 
per  quintal)  ;  Germany  alone  imported  30,000  tons  of  it  in  1909. 

1  Comparison  between  Various  Sources  of  Light.  To  produce  the  luminous  intensity  of  a  Hefner  candle- 
hour  (HK),  the  following  quantities  of  lighting  materials  must  be  consumed  : 

,-Stearine,  first  quality 

,,        third      „  ... 

-  Paraffin 

£»      Two  parts  of  paraffin  and  one   of 
\.    stearine      ..... 
'Carcel:   colza  oil     .... 
<a  I  Petroleum,  flat  wick 

9  -'         ,,        round  wick 

5 

I  Spirit :  incandescent 

^Petroleum  with  Auer  mantle 

It  is  easy  to  calculate  the  cost  from  the  prices  of  the  various  methods  of  lighting,  these  varying  from  town  to 
town  and  from  country  to  country.  In  1896  Lttpke  calculated  the  following  numbers  of  normal  candle-hours  to 
be  obtainable  for  one  mark  (one  shilling),  the  calculation  being  only  valid  for  that  period  and  for  Germany  :  wax, 
33 ;  stearini!,  77  ;  colza  oil,  150 ;  electric  lamp  with  incandescent  carbon  filament,  150  ;  fish-tail  gas-jet,  625  ; 
acetylene  and  air  with  an  edged  burner,  716 ;  oil-gas,  1660 ;  water-gas  with  benzene,  1666 ;  electric  arc  lamp, 
2232  ;  Auer  gas  lamp,  2300  ;  Auer  water-gas  lamp,  4350. 

From  gas  at  l-9d.  (0-2  lira)  per  cubic  metre,  as  a  source  of  heat.  1000  cals.  are  obtained  for  0-38<Z.  (0-04  lira), 
whilst,  using  electric  current  at  3-07<i.  (0-32  lira)  per  kilowatt-hour,  1000  cals.  would  cost  about  3-65d.  (0-38 lira). 
For  power  purposes,  the  electric  current  [at  2-4d.  (0-25  lira)  per  kilowatt-hour]  costs  more  than  double  as  much  as 
gas  [at  l-73tf.  (0-18  lira)  per  cubic  metre]. 

During  the  past  few  years  a  considerable  advance  has  been  made  by  the  use  of  incandescent  electric  lamps  with 
metallic  filaments  (tantalum,  tungsten,  osmium,  &c.),  which  reduce  the  consumption  of  electrical  energy  by  one- 
half.  But  at  the  same  time  gas  lamps  have  been  improved  by  the  use  of  high-pressure  gas,  and  those  with  inverted 
flames  are  still  decidedly  more  economical  than  metallic  filament  electric  lamps.  From  the  hygienic  point  of  view 
the  disadvantages  of  gas  lighting  have  been  exaggerated,  as  it  has  not  been  realised  that  the  use  of  gas  causes  cir- 
culation and  renewal  of  the  air,  and  that  the  production  of  water-vapour  and  carbon  dioxide  are  negligible  compared 
with  the  similar  effects  produced  by  the  respiration  of  human  beings. 


7-87  grms.         Acetylene      ....               0-6      litres 

9-58 

•Fish-tail          .         . 

19-0 

6-27 

<a   2 

Argand  .         .         .         .     ' 

10 

6-93 
3-99 

|  g  A  Auer      .... 
Millenium  (gas  under  pressure) 
^Auer  with  inverted  flame. 

1-60 
0-75 
0-70 

2-76 

ft 

/  Arc  lamp  of  small  power  . 

1-20  volt-amps. 

,  2-80  • 

|   I  Arc  lamp  of  high  power   . 

0-25 

(3-60 

~   I  Incandescent  Edison 

3-70 

1-90 

'E   |  Metallic      filament      (osmium 

0-50 

g         tantalum)    .                   . 

1-90 

§   ^Mercury  vapour 

0-50 

58  ORGANIC    CHEMISTRY 

PETROLEUM   INDUSTRY 

Crude  petroleum  also  goes  under  the  name  of  mineral  oil  or  naphtha,  and 
is  a  more  or  less  dark  liquid  (according  to  its  origin)  with  a  peculiar,  pro- 
nounced odour.  It  is  found  in  various  parts  of  the  earth  in  the  strata  of  the 
tertiary  epoch  and  also  of  preceding  epochs.  The  principal  centres  of  pro- 
duction are  Baku  (Russia)  and  the  United  States.1 

In  some  places  it  overflows  at  the  surface  of  the  earth  through  porous 
rocks  or  clefts  ;  in  others  it  is  found  accumulated  under  pressure  in  large 
cavities  or  pockets,  since  when  it  is  reached  by  borings  or  wells,  powerful  jets 
rise  above  the  surface  of  the  earth  often  to  the  height  of  100  metres,  thus 
forming  fountains  of  petroleum  which  last  from  a  few  weeks  up  to  seven  or 
eight  months  and  throw  up  also  large  quantities  of  inflammable  gases  and 
sand. 

Some  petroleum  deposits  have  been  gradually  evaporated  and  oxidised 

1  History  of  the  Petroleum  Industry.  The  use  of  petroleum  and  of  tar  goes  back  to  the  earliest  historical 
times  (the  Biblical  legend  relates  that  Noah  rendered  bis  ark  impermeable  by  means  of  tar,  and  in  the  construction 
of  the  Tower  of  Babel  a  mortar  was  used  prepared  with  naphtha  1  (?) ).  Certain  races  then  employed  naphtha 
as  a  combustible,  and  the  Egyptians  made  use  of  it  in  the  preparation  of  mummies. 

In  small  quantities  petroleum  is  found  in  nearly  all  countries,  but  95  per  cent,  of  the  total  production  is  given 
by  North  America  and  Russia.  Two  centuries  before  petroleum  was  used  in  America  that  from  Parma  in  the  Apen- 
nines was  used  for  lighting,  e.g.  at  Genoa,  Parma,  &c.  The  most  important  petroleum  wells  now  in  Italy  are  in 
the  Province  of  Piacenza  (at  Fioreniuola  d'Arda)  and  at  Salsomaggiore,  Borgo  S.  Donnino,  and  Montechino  ; 
less  important  deposits  are  found  also  in  Calabria.  At  Velleia  the  industry  has  been  worked  for  many  years  by 
a  French  company,  many  wells  200  to  450  metres  deep  having  been  sunk  along  the  right  bank  of  the  Chero  ;  this 
company  was  absorbed  by  an  Italian  syndicate  in  1907. 

In  Austria  the  region  richest  in  petroleum  is  Galicia.  In  1895,  when  a  well  300  metres  deep  was  bored,  a 
fountain  was  formed  which,  in  thirty-six  hours,  yielded  5000  barrels  of  petroleum  (1  barrel  =  42  gallons  = 
159  litres  =  145  kilos).  Still  more  important  wells  in  other  countries  are  mentioned  on  p.  66. 

In  Russia  the  most  important  sources  of  petroleum  are  found  in  the  province  of  1-aku  (99  per  cent,  of  the  whole 
production  is  obtained  from  an  area  of  6  sq.  kiloms.),  and  partly  at  Grosny,  to  the  north.  From  the  most  remote 
times,  before  Christ,  sacred  fires,  fed  by  petroleum  and  by  the  inflammable  gases  liberated  from  it,  have  been  kept 
burning  uninterruptedly  in  the  temples  (down  to  1880).  During  his  voyage  in  the  thirteenth  century  Marco  Polo 
visited  these  marvellous  springs  of  "  oil  not  good  to  use  with  food  but  good  to  burn  and  also  used  to  anoint  camels  that 
have  the  mange." 

In  1820  the  Baku  petroleum  wells  were  declared  the  property  of  the  Russian  State,  and  the  Government  made 
concessions  to  contractors  who  worked  them  in  a  primitive  manner  until  1872.  In  1873,  the  most  important 
wells  and  petroleum-bearing  lands  were  put  up  for  auction  by  the  Government,  who  levied  a  tax  on  the  petioleum 
extracted.  This  condition  of  affairs  was  less  favourable  than  that  holding  in  the  American  industry,  so  that 
in  1877  the  tax  was  repealed  and  the  Russian  petroleum  industry,  passing  into  the  hands  of  great  capitalists 
(Nobel,  Rothschild,  &c.),  underwent  extraordinary  development  and  often  competes  advantageously  with  that 
of  America. 

The  first  plant  installed  by  Baron  Thormann  for  the  distillation  of  petroleum  was  constructed  at  Baku  in  1858 
according  to  suggestions  and  plans  furnished  by  Liebig,  carried  out  by  one  of  his  assistants  (Moldei.hauer),  and 
improved  by  Eichler.  The  first  wells  bored  on  the  American  system  date  from  1869.  Before  1870,  the  production 
was  only  250,000  poods  (1  pood  =  16-38  kilo),  but  in  1872  it  reached  1,500,000  poods  and  then  grew  with  astounding 
rapidity  (see  later,  Statistics). 

There  are  also  important  petroleum  deposits  in  Japan,  but  the  production  is  still  limited  :  in  1874  it  amounted 
to  126,150  kwan  (1  kwan  =  3-78  kiloo),  in  1884  to  1,400,000  kwan,  and  in  1903  to  about  126,000  tons. 

During  recent  times  important  sources  of  petroleum  have  also  been  discovered  in  Canada. 

The  greatest  impulse  to  the  petroleum  industry  has  come  from  the  United  States  of  America,  where  important 
deposits  of  petroleum  have  been  found,  first  in  the  State  of  Pennsylvania  (in  a  strip  of  land  about  100  kiloms. 
long,  the  production  of  petroleum  increased  from  3180  hectolitres  in  1859  to  16,000,000  hectolitus  in  1874,  the 
price  per  barrel  falling  during  the  same  period  from  100  lire  or  £4  to  6-5  lire  or  5s.  2Jd. ;  these  deposits  arc  now 
apparently  becoming  exhausted),  and  then  in  Virginia,  Ohio,  Indiana,  California,  Louisiana,  and  'J  exas.  At  the 
present  time  the  most  important  sources  of  petroleum  in  the  United  States  are  in  the  Washington  district. 

The  first  studies  on  petroleum  in  America  were  made  by  Silliman  in  1854,  by  fractional  distillation,  and  these 
were  folio  wed  by  unsuccessful  industrial  efforts  caused  by  the  low  production  of  the  wells  utilised  and  by  many 
commercial  difficulties,  which  were  overcome  by  L.  Drake  in  1859  by  the  use  of  artesian  wells. 

The  first  petroleum  well  in  America  was  obtained  by  pure  chance ;  at  Titusville  in  Pennsylvania  a  well  was 
being  sunk  for  drinking  water  and  when  a  depth  of  22  metres  was  reached,  a  continuous  jet  of  petroleum 
appeared  yielding  4000  litres  of  naphtha  per  day. 

Just  as  America  was  taken  with  the  "  gold-fever  "  after  the  discovery  of  gold  in  California,  so  the  United 
States  caught  the  petroleum  fever.  Pennsylvania  was  invaded  by  adventurers,  and  borings  were  made  wherever 
the  geological  formation  of  the  earth  admitted  of  it;  all  had  faith  in  the  goddess  Fortune,  who,  as  always, 
favoured  some  and  drove  others  to  ruin  and  despair.  In  1861  the  number  of  derricks  (used  for  boring)  exceeded 
2000.  The  work  was  carried  out  hastily  and  without  thought,  usually  empirically,  the  idea  being  to  succeed  fiist. 
Much  petroleum  was  lost,  and  much  was  burnt,  causing  immense  losses  and  ruin  to  numerous  firms. 

Great  capitalist  companies  were  then  formed  and  these  studied xcaliuly  and  rationally  the  technical  and  com- 
mercial problem  and  very  soon  created  an  enormous  industry,  which  rapidly  brought  petroleum  into  common  use 
all  over  the  world.  Ships  and  railways  and  then  iron  pipes  ten  and  hundreds  of  kilometres  in  length  served  to 
transport  the  petroleum  rapidly,  continuously,  and  economically  from  the  wells  to  the  rcfiueiies  and  Irom  these  to 
the  seaports,  where  it  was  shipped  to  the  merchants. 


ORIGIN    OF    PETROLEUM  59 

during  the  lapse  of  ages,  leaving  a  black  deposit  of  mineral  tar  or  asphalte  (see 
section  on  Paraffin). 

ORIGIN  OF  PETROLEUM.  Various  hypotheses  have  been  put  forward  to  explain 
the  origin  of  petroleum,  and  even  to-day  opinions  are  divided,  probably  owing  to  the 
fact  that  petroleum  has  not  one  single  origin,  since,  in  different  parts  of  the  earth's  crust, 
it  has  different  qualities  and  compositions. 

(1)  Hypothesis  of  Inorganic  Origin.     A.  v.  Humboldt  supposed  petroleum  to  have 
originated  from  inorganic  gaseous  products  under  the  influence  of  volcanic  forces,  and  in 
1866    Berthelot   advanced   the   hypothesis   that,    by   the    action   of  carbon  dioxide  on 
alkali  metals  inside  the  earth's  crust,  acetylides  would  be  formed  which  with  hydrogen 
would  give  acetylene  derivatives,  these  then  undergoing  various  condensations  to  form 
petroleum  and  tar.     Byasson  in  1871  explained  the  formation  of  the  hydrocarbons  of 
petroleum  as  due  to  the  action  of  H2S,  CO2,  and  water-vapour  on  layers  of  red-hot  iron, 
this  action  being  produced  by  the  infiltration  of  sea-water,  through  clefts  at  the  bottom 
of  the  ocean,  in  such  a  way  that,  together  with  calcareous  matter,  it  was  brought  into 
contact  with  deposits  of  heated  iron  or  iron  sulphide.     Mendelejeff  (1877)  regarded  the 
hydrocarbons  of  petroleum  as  originating  in  the  igneous  strata  of  the  earth's  crust  by 
the  action  of  aqueous  infiltrations  on  pre-existing  deposits  of  carbide  of  iron  or  other 
metallic  carbides.     From  1877  to  1879  Cloe'z  obtained  support  for  Mendelejeffs  hypo- 
thesis by  showing  experimentally  that  saturated  hydrocarbons  are  formed  when  cast 
iron  or  spiegeleisen  (substances  which  contain  carbide  of  iron)  is  dissolved  in  acid.     In 
1891  Boss  brought  forward  again  and  modified  Byasson 's  hypothesis  ;  he  assumed  that 
volcanic  gases,  especially  H2S  and  SO2,  in  contact  with  heated  chalky  rocks,  would  form 
gypsum,  with  separation  of  sulphur  and  production  of  saturated  and  unsaturated  hydro- 
carbons (this  would  also  give  an  explanation  of  the  origin  of  sulphur,  yet  in  Sicily,  where 
sulphur  abounds,  no  petroleum  is  found  !). 

These  various  hypotheses  on  the  inorganic  origin  of  petroleum  assume  the  formation 
of  the  latter  in  igneous  primitive  (archaic)  geological  strata,  where  the  presence  of  organic 
compounds  is  excluded,  the  petroleum  then  finding  its  way  to  the  higher  layers  of  the  earth's 
crust  by  seismic  convulsions.  But  it  is  precisely  these  older  archaic  strata,  deprived  of 
water  and  of  organic  substances,  which  give  no  trace  of  petroleum.  On  the  other  hand, 
if  the  petroleum  were  formed  in  very  hot  strata,  it  should  issue  from  the  borings  at  a 
moderately  high  temperature,  and  there  should  have  been  separation  of  the  light  petroleum 
(more  volatile)  and  the  heavy  into  distinct  layers.  But  this  is  not  actually  the  case. 

However,  during  recent  years  this  hypothesis  has  again  come  into  favour,  owing 
to  the  interesting  work  of  Moissan  (1894-1896)  on  the  formation  of  saturated  hydro- 
carbons by  the  action  of  water  on  aluminium  carbide  (see  p.  34),  and  that  of  Sabatier 
and  Senderens  (1896-1902),  who  showed  experimentally  that,  in  presence  of  catalytic 
nickel  (obtained  by  reduction  of  the  oxide  with  hydrogen  at  300°),  hydrogen  and  un- 
saturated hydrocarbons  (ethylene,  acetylene,  &c.)  give  rise  to  saturated  hydrocarbons 
such  as  occur  in  petroleum  (p.  34).  But  even  these  syntheses  do  not  yield  very  high 
and  solid  hydrocarbons  like  those  present  in  crude  petroleum,  although  recently  (1908- 
1909)  A.  Brun,  Stieger,  and  Becker  showed  that  hydrocarbons  similar  to  paraffin  are 
formed  by  the  interaction  in  the  hot  of  iron  carbide  and  ammonium  chloride,  even  in 
absence  of  water. 

(2)  Hypothesis  of  the  Vegetable  Origin  of  Petroleum.     This  was  enunciated  at  intervals 
by  Binney  (by  distillation  of  peat),  by  Kobell  (by  distillation  of  coal),  and  by  Bischof, 
who  considered  petroleum  to    be   formed   by  the   action   of   sea-water  on  cellulose  and 
on  coal  included  in  the  geological  strata  of  the  earth's  crust.     This  hypothesis  of  the 
vegetable  origin  was  later  supported  or  attacked  by  various  writers,  and  to  the  fact 
that,  in  general,  carboniferous  strata  do  not  contain  petroleum,  is  opposed  the  discovery 
of   small   deposits  of   petroleum   in   the   coal-seams  near   Wombridge    and    of    certain 
petroliferous  substances  in  Japanese  coals  ;    but   Hofer   showed  that,  in  the  first   case, 
the  neighbourhood  of  bituminous  schists,  rich   in   the   remains   of   fishes,  could  not  be 
excluded,  and,  if  it  is    desired    to    explain    the    formation    of    petroleum  from  marine 
vegetable  organisms,  it  is  not  possible  to  conceive  of  a  sufficient  quantity  of  these  to 
give  rise  to  the  immense  amounts  of  petroleum  now  discovered.     Further,  other  more 
recent  geological  investigations  would  exclude  the  vegetable  origin  of  petroleum,  although 
the  most  recent  chemical  work  tends  to  render  such  origin  highly  probable.     It  is,  indeed, 


60  ORGANIC    CHEMISTRY 

found  that  petroleum  rotates  the  plane  of  polarisation  of  light  to  the  right  (see  later), 
as  do  most  optically  active  vegetable  substances,  whilst  substances  of  animal  origin  rotate 
it  preferably  to  the  left.  Engler,  however,  states  that  this  observation  is  not  very  con- 
clusive, since  these  active  substances  may  be  due  to  the  condensation  of  unsaturated 
products  originating  in  the  decomposition  of  the  prime  materials  (animals  or  possibly 
vegetables).  Kramer  and  Potonie(  1906-1 907)  point  out  that  all  petroleums  (also  certain 
lignites  and  ozokerite)  contain  algce  wax,  from  which,  _by  various  reactions  and  decom- 
positions, it  is  easy  to  pass  to  substances  like  petroleum,  and  simple  substances,  by  poly- 
merisation (by  heat  and  pressure),  form  more  complex  tarry  substances,  &c.  ;  the  presence 
of  wax  demonstrates  that  petroleum  is  not  formed  in  the  hot  by  distillation,  but  rather 
in  the  cold  and  at  high  pressures.  The  prime  material  of  petroleum  would  hence  probably 
be  the  enormous  formation  of  algce  which  have  been  produced  at  all  epochs  and  are  to -day 
accumulating  in  marshy  places.  These,  during  thousands  of  centuries  and  under  the 
action  of  pressure  and  heat,  could  undergo  the  same  transformations  and  putrefactions 
(mixed  sometimes  with  animal  remains),  leaving  the  wax  for  the  formation  of  petroleum  ; 
so  that  petroleum  would  be  formed  in  all  epochs  and  is  perhaps  being  formed  now  !  The 
varying  composition  of  petroleum  would  be  due,  according  to  Kramer,  to  filtration  through 
various  geological  strata,  which  would  have  removed  greater  or  less  quantities  of  bitu- 
minous products  so  as  to  produce  pale,  light  petroleums  like  those  of  Velleia  and  Montechino. 
Hence  the  greater  or  less  content  of  tarry  substances  cannot  serve  as  an  indication  of  the 
epoch  of  formation  of  a  petroleum,  since  part  of  these  substances  may  have  been  lost  during 
the  geological  nitrations. 

(3)  Hypothesis  of  the  Animal  Origin  of  Petroleum.  This  was  enunciated  and  vigorously 
upheld  by  Hofer,  and  supported  and  supplemented  by  Ochsenius  (1892),  Zaloziecki  (1892) 
Veith,  Dieckhoff  (1893),  Aisinmann  (1894),  Heusler  (1896),  Holde  (1897),  Aschan  (1902), 
and  Zuber  (1897,  who  supported  only  the  organic  origin),  and  more  especially  and  most 
exhaustively  by  Engler  (1888-1901). 

This  hypothesis  supposes  that  great  layers  of  various  fishes  and  molluscs,  formed  on 
the  ocean-bed  during  past  geological  epochs,  gradually  underwent  decomposition,  first 
losing  the  nitrogenous  components  (albuminoids)  as  gaseous  or  soluble  compounds,  the 
remaining  fats  being  slowly  transformed  partially  into  bituminous  substances.  These, 
together  with  the  residual  fats,  under  the  action  of  great  pressure  and  heat  (developed, 
in  part,  by  these  decompositions)  would  yield  glycerol,  which  would  generate  acrolein 
and  then  aromatic  hydrocarbons,  while  the  remaining  fatty  acids  (by  the  action  of  hydro- 
gen formed  in  all  these  decompositions)  would  give  rise  to  the  various  saturated  hydro- 
carbons constituting  petroleum,  C02  being  liberated. 

The  animal  origin  hypothesis  is  also  supported  by  the  observation  made  by  Fraas, 
that  petroleum  issues  from  the  coralliferous  banks  of  the  Red  Sea,  and  by  the  odour  of 
petroleum  exhibited  by  certain  phosphorites  which  are  undoubtedly  of  animal  origin. 

The  objection  has  been  raised  that,  if  petroleum  were  of  animal  origin,  it  should  contain 
nitrogenous  compounds.  Although  this  is  not  necessary,  yet  the  presence  of  nitrogen 
products  (ammonia  and  pyridine  bases,  free  nitrogen  and  ammonium  carbonate)  has 
been  shown  in  petroleum  and  in  gases  emanating  from  the  earth.  Texas  petroleum 
contains  up  to  1  per  cent,  of  nitrogen. 

Engler  showed  experimentally  that,  under  certain  conditions,  animal  fats  can  be 
transformed  into  defines  or  analogous  products  in  the  laboratory  (by  distilling  fish-oil 
under  4-10  atrnos.  pressure).  In  1909,  Engler,  Routala,  Aschan,  and  others  effected  the 
laboratory  production  of  naphthenes,  paraffins,  and  heavy  mineral  oils,  by  heating  amylene 
and  hexylene  under  pressure  and  in  presence  or  absence  of  aluminium  chloride  as  catalyst. 

Many  facts  support  the  view  that  the  petroleum  of  the  geological  strata  studied  has 
been  formed  at  a  low  temperature  and  by  slow  but  continuous  reactions  lasting  for 
thousands  of  years. 

To  the  doubt  that  may  be  raised  as  to  the  enormous  quantity  of  animal  remains 
necessary  to  explain  the  large  amounts  of  petroleum  being  raised  at  the  present  time,  it 
may  be  answered  that  if  the  annual  catch  of  herrings  on  the  coasts  of  the  northern  seas 
and  that  of  sardines  by  French  fishermen  were  to  accumulate  on  the  ocean-bed  for  2000 
years,  it  would  be  quite  sufficient  to  explain  the  petroleum  production  of  Russia.1 

1  In  1903  the  fish  caught  by  103,000  fishermen  along  the  6000  kiloms.  of  Italian  coast  weighed  62,000,000  kilos 
(15,000,000  in  Sicily)  and  had  a  value  of  about  £800,000  (in  1904,  only  £620,0(10).  In  the  valleys  of  Comacchio 
during  the  month  of  October  1905,  alone,  were  caught :  450,000  kilos  of  eels,  60,000  of  mullet,  50,000  of  various 


ORIGIN    OF    PETROLEUM  61 

It  would,  however,  be^  necessary,  for  the  preservation  of  this  enormous  cemetery  of 
fish,  that  the  corpses  should  not  be  eaten  by  other  larger  fish  ;  the  conditions  must  then 
be  such  that  fish  approaching  the  cemetery  are  killed.  And  this  is  highly  probable,  as 
the  existence  of  such  conditions  at  the  bottom  of  the  Black  Sea  has  recently  been  proved. 
In  fact,  below  a  certain  depth,  there  is  so  much  dissolved  hydrogen  sulphide  that  any 
animal  is  instantly  poisoned  there,  its  body  going  to  swell  the  vast  numbers  that  have 
preceded  it  at  the  bottom. 

With  these  proofs  is  connected  the  most  recent  and  most  rational  interpretation  of  the 
origin  of  petroleum.  It  is  supposed  that  the  decomposition  of  the  residual  animal  fats 
is  aided  by  certain  ferments  as  yet  not  studied — anaerobic  bacteria  analogous  to  those 
which  have  been  studied  in  the  cases  of  the  transformation  of  wood  into  coal,  the  fermenta- 
tion of  cellulose,  peat,  &c.  And  the  hydrogen  sulphide  formed  at  the  bottom  of  the 
sea  would  be  a  product  of  the  fermentations  due  to  these  bacteria. 

Rakusin  (1905  and  1906)  made  a  new  contribution  to  the  explanation  of  the  origin 
of  petroleum,  by  discovering  in  various  petroleums  a  slight  optical  activity,  undoubtedly 
due  to  substances  of  organic  origin  (animal  or  vegetable).  Neuberg  (1905-1907)  has 
shown  that,  in  the  putrefaction  of  protein  substances,  pronounced  quantities  of  optically 
active  acids  and  amino -acids  are  formed,  and  by  heating  under  pressure  or  dry-distilling  a 
mixture  of  oleic  acid  with  a  little  valeric  acid,  a  product  is  obtained  which,  after  purification, 
has  the  characters  of  naphtha  as  regards  the  optical  rotation,  boiling-point,  and  other 
properties.  All  this  supports  the  organic — probably  animal — origin  of  petroleum,  and 
even  if  the  fats  do  not  give  an  optically  active  petroleum,  the  activity  would  be  imparted 
by  the  decomposition  products  of  the  proteins.  The  optical  activity  of  petroleum  was 
recognised  as  far  back  as  1835  by  Biot,  who,  however,  drew  no  practical  or  theoretical 
conclusions  from  the  observation.  Rakusin  observed  that  petroleums  exhibit  the  Tyndall 
phenomenon  (vol.  i,  p.  103)  to  a  more  or  less  marked  extent,  and  since  petroleums  arc 
sometimes  inactive  and  have  varying  chemical  composition,  he  regards  the  different 
hypotheses  concerning  their  origin  as  justified.  Petroleum,  as  a  liquid,  must  be  considered 
as  intermediate  to  natural  inflammable  gas  and  solid  asphalte  or  ozokerite.  Since  the 
white  cerasin  which  is  extracted  from  ozokerite  is  dextro-rotatory,  it  must  be  concluded 
that  ozokerite  is  of  organic  origin  (the  products  formed  by  synthesis  from  simpler  or 
artificial  substances  being  optically  inactive,  see  p.  22). 

The  petroleum  or  similar  substances  prepared  artificially  from  the  elements  possess  all 
the  properties  of  true  petroleum,  but  are  optically  inactive.  Hence  the  most  certain 
criterion  of  the  organic  origin  of  a  petroleum  is  its  optical  rotation.  If  a  petroleum  is 
optically  inactive,  it  may  have  originated  from  a  racemic  product  (optically  and  transitorily 
inactive,  see  p.  19)  of  organic  origin,  but  may  have  been  formed  from  inorganic  materials. 
However,  inactive  petroleums  are  rare  ;  Rakusin  (1907)  has  only  found  three  such  up 
to  the  present,  one  Russian  (Surakhany)  and  two  Italian  (Montechino  and  Velleia),  and 
he  states  that  not  only  the  degree  of  carbonisation  of  the  petroleum  (richness  in  carbon), 
but  also  its  degree  of  racemisation  must  be  taken  account  of  in  judging  its  geological  age. 

small  fish  (acquadelle),  whilst  in  October  1910,  985,000  kilos  of  eels  and  mullet  were  taken.  Italy  is,  however, 
considerably  behindhand  in  the  fishing  industry,  owing  to  insufficient  study  of  its  seas  and  to  the  great  technical 
deficiency  of  the  methods  employed  by  the  fishermen,  while  the  speculation  of  a  few  merchants  makes  fish  in  the 
great  cities  of  Italy  much  dearer  than  in  other  countries.  Consequently,  Italy  imports  continually  increasing 
quantities  of  fish  of  all  kinds,  the  value  of  that  imported  during  1907  being  over  £3,000,000.  In  Germany  in  1902, 
31,000,000  kilos  of  herrings  worth  £400,000  were  caught,  and  in  the  ports  of  the  Elbe  and  Weser  fish  of  the 
additional  value  of  £640,000  was  taken.  In  the  United  States  with  134,000  fishermen,  fish  of  the  value  of  £10,000,000 
was  caught  in  1903  ;  and  in  1909,  219,500  fishermen  took  1,000,000  tons  of  fish  of  the  value  of  £12,000,000,  including 
100,000  tons  of  oysters  worth  £3,100,000,  and  40,000  tonsof  cod  of  the  value  £480,000.  In  France  95,500  fishermen 
caught  fish  worth  about  £4,700,000  in  1902,  and  in  Norway  101,000  fishermen  took  £3,200,000  in  1905.  In 
Holland  21,000  fishermen  earned  £900,000 ;  in  England  106,500  fishermen,  £9,000,000 ;  and  in  Spain,  121,400 
fishermen  £1,800,000 

In  the  Caspian  Sea  during  the  winter  of  1906, 129,000  seals  were  killed,  the  yield  of  oil  being  2,245,000  kilos, 
and  its  value  £25,000,  without  considering  the  fat  and  skins,  each  of  which  costs  8s.  to  10s.  On  the  coast  of  Tonquin 
30,000,000  kilos  of  fish  were  taken  in  1893. 

To  obtain  an  idea  of  the  fertility  of  certain  fish,  the  shad,  a  fish  of  the  herring  family,  weighing  up  to  5  to  6  kilos, 
may  be  considered';  the  female  lays  as  many  as  100,000  eggs,  which  can  be  fertilised  artificially,  as  is  done  with  the 
salmon  and  trout. "  In  North  America  the  eggs  are  collected  and  despatched  to  the  Central  Pisciculture  Station  at 
Washington,  where  they  are  hatched  in  four  days  in  Macdonald  or  Weiss  tanks  with  flowing  water  at  18°  to  19°, 
and  are  immediately  placed  in  the  rivers,  where  they  grow  rapidly.  Every  year  more  than  100,000,000  eggs  are 
fertilised  in  this  way  and  from  1875  to  1890  the  shad  fishing  showed  an  increase  of  100  per  cent.,  corresponding 
with  £160,000.  The  female  cod  may  lay  as  many  as  6,000,000  eggs  during  its  lifetime,  and  the  turbot  even 
9,000,000.  In  Italy  there  are  only  two  schools  of  fishery,  whilst  in  Germany  there  are  thirty-four,  in  Franp 
seventeen,  and  in  Japan  one  for  each  maritime  province. 


62  ORGANIC    CHEMISTRY 

In  1908,  Zaloziecki  and  Klarfeld  held  that  the  optical  activity  of  petroleum  is  due  to 
the  presence  of  terpenes  or  colophony  ;  but  Neuberg  regards  it  a.s  due  to  decomposition 
products  of  amino-acids  (valeric  or  isocaproic  acid)  formed  from  the  proteins.  Marcusson 
(1908)  combats  these  last  two  hypotheses,  and  shows  that  it  is  more  probable  that  the 
activity  is  derived  from  decomposition  products  (dextro-rotatory)  of  Isevo-rotatory 
cholesterols  (and  hence  of  animal  origin,  whilst  the  vegetable  ones  are  dextro-rotatory 
and  yield  laevo -rotatory  decomposition  products).  By  distilling  olein  under  pressure, 
Marcusson  (1910)  obtained  hydrocarbons  which  had  an  optical  activity  equal  to  that  of 
natural  proteins  and  which  he  regarded  as  formed  from  the  original  cholesterols.  By  the 
action  of  ozone,  Molinari  and  Fenaroli  (1908)  showed  that  the  Russian  and  Roumanian 
petroleums  examined  by  them  contained  no  unaltered  cholesterol,  but  this  does  not  exclude 
the  presence  of  active  decomposition  products,  which,  however,  would  not  contain  double 
linkings.  In  addition  to  dextro-rotatory  compounds,  Java  and  Borneo  petroleums 
contain  Isevo-rotatory  substances  which  become  dextro-rotatory  at  350°  (as  happens  when 
laevo -rotatory  cholesterol  is  heated)  ;  also  certain  inactive  fractions  become  dextro- 
rotatory when  heated.  Rakusin,  Molinari,  and  Fenaroli  showed  that  the  optical  activity 
increases  in  those  portions  of  petroleum  that  have  the  highest  boiling-point. 

COMPOSITION  AND  PROPERTIES  OF  CRUDE  PETROLEUM. 

As  obtained  from  the  wells,  crude  petroleum  varies  in  colour  from  yellowish 
to  pale  brown,  or  even  black,  according  to  its  origin  ;  it  exhibits  a  marked 
greenish  fluorescence  and  a  characteristic,  garlic-like  odour.  The  dissolved 
gas  soon  separates  spontaneously,  and  sometimes,  on  oxidation  in  the  air, 
petroleum  deposits  dark,  bituminous  substances  (paraffin,  tar).  The  lighter 
petroleums  are  the  paler  and  have  an  agreeable,  ethereal  odour,  whilst  the 
heavier  ones  are  darker  and  have  an  unpleasant  odour. 

Certain  petroleums  have  recently  been  found  to  be  radioactive. 

The  presence  of  sulphur  in  petroleum,  even  if  much  less  than  1  per  cent., 
injures  its  odour  and  colour.  The  specific  gravity  of  petroleum  varies  from 
0-780  to  0-970.  Petroleum  obtained  from  Terra  di  Lavoro,  Italy,  has  a  high 
specific  gravity  (0-970)  and  certain  Roumanian  and  Indian  petroleums,  rich 
in  paraffins,  show  values  higher  even  than  this,  sometimes  as  much  as  1-3. 

Montechino  petroleum  has  the  sp.  gr.  0-740  ;  that  of  Velleia,  0-780  ; 
American,  0-800-0-870  ;  Russian,  0-850-0-900  ;  and  Galician,  0-827-0-890. 

Different  petroleums  are  composed,  as  a  rough  mean,  of  13  per  cent,  of 
hydrogen  and  87  per  cent,  of  carbon,  small  proportions  of  oxygen,  nitrogen, 
and  sulphur  compounds  being  also  present.  The  hydrocarbons  present  in 
petroleum  are  numbered  by  the  hundred,  and  they  belong  to  different  series, 
one  or  other  of  which  preponderates  according  to  the  source.  Thus,  Penn- 
sylvanian  petroleums  are  constituted  almost  exclusively  of  hydrocarbons  of 
the  saturated  series  CwH2w+2  (derivatives  of  methane),  which  are  also  found 
in  Galician  petroleums,  &c. 

Some  petroleums  contain  as  much  as  40  per  cent,  of  hydrocarbons  solid 
at  the  ordinary  temperature  (paraffin),  and  these  are  left  after  distillation 
(e.g.  Java  petroleum)  ;  usually,  however,  much  less  than  this  is  present, 
American  petroleums  having  only  2-5-3  per  cent.,  and  those  of  Baku  some- 
times only  0-25  per  cent.  Different  petroleums  can  be  distinguished  by  means 
of  the  ultra-microscope,  the  paraffin  being  dissolved  in  the  colloidal  condition. 

It  is  maintained  by  various  chemists  that  the  paraffin  is  not  pre-existent 
in  petroleum,  but  is  formed  during  its  distillation.  This  is  contradicted  by 
the  fact  that  some  petroleum  pipes  show  deposits  of  paraffin,  and  this  can 
also  be  separated  from  cold  petroleum  by  special  solvents. 

Hydrocarbons  of  the  unsaturated  ethylenv  series,  CnH2n,  preponderate  in 
the  petroleums  of  Burma  and  are  abundant  in  those  from  California  ;  Penn- 
sylvanian  petroleum  contains  about  3  per  cent.  Different  petroleums  can 
hence  be  distinguished  by  the  quantities  of  bromine  or  iodine  which  they  fix, 


COMPOSITION    OF    PETROLEUM  63 

by  the  amounts  of  hydrobromic  or  hydriodic  acid  then  formed  (Park  and 
Worthing,  1910)  or  by  the  quantities  of  ozone  they  take  up  (Molinari  and 
Fenaroli,  1908). 

Hydrocarbons  of  the  same  general  formula,  CnH2n,  but  saturated  (cyclic  com- 

,  CH2 — CH2 

pounds,  so-called  naphthenes,  or  derivatives  of  cyclopentane,  CH2\  |      , 

XCH2— CH2 
,CH2 — CH2 
or  cydohexane,  CH2\  j>CH2)  form  80  per  cent,  of  Baku  petroleums 

XCH2— CH/ 

and  occur  abundantly  in  those  of  Galicia,  together  with  about  10  per  cent, 
of  hydrocarbons  of  the  aromatic  series  (recently  (1910)  hexahydrocumene  has 
been  identified). 

In  a  Russian  petroleum  and  also  in  a  Roumanian  one,  Molinari  and  Fenaroli 
(1908)  found  hydrocarbons  derived  from  naphthenes  with  two  double  linkings 
and  having  the  general  formula  CnH2M  _14  (for  example,  C17H20). 

In  certain  petroleums  small  quantities  of  acetylene  derivatives  occur. 

It  is  found  that  petroleums  produced  in  localities  relatively  near  to  one 
another  often  have  different  compositions  ;  according  to  David  Day  this  is 
due  to  the  fact  that  the  unsaturated  hydrocarbons  diffuse  less  easily  through 
sandy  or  other  soils,  and  this  system  of  natural  filtration  gives  rise  to  various 
types  of  petroleum,  with  preponderance  of  saturated  hydrocarbons  in  some 
and  of  unsaturated  hydrocarbons  in  others.  This  explanation  is  more  reason- 
able than  that  the  separation  has  been  effected  by  distillation. 

The  products  that  distil  below  180°  are  almost  exclusively  saturated  and 
those  distilling  about  200°  mostly  unsaturated. 

The  very  small  quantities  of  oxygenated  substances  contained  in  petroleum 
(often  less  than  1  per  cent,  and  rarely  5  per  cent.)  are  composed  of  phenols 
and  organic  acids  (e.g.  in  Galician  petroleum). 

The  traces  of  nitrogenous  substances  found  in  various  petroleums  (see 
above)  support  the  hypothesis  of  the  organic  origin  of  petroleum. 

Almost  all  petroleums  contain  sulphur,  which  is  very  difficult  to  remove 
and  imparts  an  unpleasant  odour  and  bad  colour. 

Usually  the  proportion  of  sulphur  is  about  0-10-0-15  per  cent.,  but  the  petroleum 
of  Terra  dl  Lavoro  contains  as  much  as  1-3  per  cent.,  while  still  more  is  found  (up  to  3  per 
cent.)  in  those  of  Texas,  Ohio,  Indiana,  and  Virginia,  from  which  it  has  to  be  separated 
(see  later). 

The  nature  of  the  sulphur  compounds  present  has  not  yet  been  completely  denned, 
but  the  presence  of  mercaptans,  thio-ethers,  thiophene,  and  its  homblogues  (methyl- 
and  dimethyl-thiophene)  has  been  detected.  According  to  Heusler  it  is  only  necessary  to 
heat  a  little  of  the  petroleum  with  a  granule  of  aluminium  chloride  to  detect  the  presence 
of  sulphur,  hydrogen  sulphide  being  then  developed. 

Also  by  fractional  distillation  and  partly  by  the  specific  gravity,  the  four  princpal 
types  of  petroleum  can  be  distinguished.  The  products  distilling  below  150°  form  the 
b?nzinis  (see  later),  then  up  to  280°  are  obtained  illuminating  petroleums  or  solar  oil  (or 
kerosene),  and  after  300°  remain  products  used  for  the  extraction  of  paraffin  and  vaseline 
(American)  or  for  the  preparation  of  mineral  lubricating  oils  (Russian) : 

Crude  petroleum  Specific  gravity  Benzine  Solar  oil  Residue 

Pennsylvania     .          .        0-79-0-82  10-20%  55-75%  10-20% 

Ohio          .          .          .        0-80-0-85  10-20%  30-40%  35-50% 

Caucasus  . 
Roumania 
Galicia 
Piacenza  . 
Alsace 


0-85-0-90 

0-2-5    % 

25-30  % 

60-65  % 

0-85 

3-10  o/0 

70-80  % 

10-15% 

0-82-0-90 

5-30  % 

35-40  % 

30-50  % 

0-74-0-79 

25-40  % 

55-65  % 

4-8  % 

0-912 

5% 

35-70  % 

55-60  % 

64 


ORGANIC    CHEMISTRY 


In  some  of  the  islands  of  the  Caspian  Sea  (Tscheleken)  is  found  a  petroleum  resembling 
the  American  type,  with  a  large  proportion  of  paraffin  (5-5  per  cent.),  and  in  Columbia 
(S.  America)  petroleums  like  those  of  Russia  (Caucasus)  occur. 

The  Italian  'petroleums  vary  considerably  in  composition  and  those  of  Emilia  and 
Piacenza  are  so  pale  and  so  rich  in  benzine  and  poor  in  residues  that  it  is  supposed  that 
they  are  the  condensed  more  volatile  products  of  more  important  deposits  not  yet  dis- 
covered. In  the  distillation  of  the  Velleia  petroleums  at  Fiorenzuola  d'Arda  the  little 

residue  obtained  is  added 
to  the  crude  petroleum 
to  be  refined  and  thus 
becomes  distributed  in  the 
lighting  oil,  so  that  the 
less  remunerative  residues 
are  never  placed  on  the 
market.  The  absence  of 
optical  activity  in  the 
petroleums  of  Montechino 
and  Velleia  (see  above) 
seems  to  confirm  the  view 
that  they  are  derived  from 
more  important  deposits, 
in  which  optically  active 
products  would  probably 
be  found. 

EXTRACTION  AND 
INDUSTRIAL  TREAT- 
MENT OF  PETROLEUM. 
From  the  most  remote 
times  petroleum  has  been 
raised  in  China  by  means 
of  wells  similar  to  the  pre- 
sent artesian  ones,  which 
the  Chinese  used  many 
centuries  before  Europeans 
for  obtaining  drinking 
water.  In  other  regions 
in  times  gone  by  the 
petroleum  flowing  at  the 
surfaces  of  the  water- 
courses began  to  be  sepa- 
rated and  used  ;  then 
wide,  shallow  wells  were 
dug  and  the  petroleum 
raised  to  the  surface  in 
buckets.  Nowadays,  how- 
ever, petroleum  is  every- 
where obtained  by  wells 
bored  into  the  earth  like 
artesian  wells,  and  some- 
times the  petroleum  flows  up  to  the  surface  under  great  pressure,  so  that  it  forms 
a  fountain  (see  Note,  p.  65,  and  Fig.  78).  It  is  supposed  that  the  deposits  of  petroleum 
in  the  interior  of  the  earth's  crust  are  situated  in  large  cavities  or  pockets,  where  there 
is  often  a  lower  layer  of  salt  water  (Fig.  79,  W )  and  on  this  floats  a  more  and  less  abundant 
layer  of  petroleum,  E  ;  and,  in  general,  the  upper  part  of  the  pocket  is  filled  with  inflam- 
mable gas,  G,  which  exerts  great  pressure.  If  the  boring,  B,  reaches  one  or  the  other 
layer,  one  or  the  other  product  is  obtained  in  preponderance  or  even  exclusively,  and, 
after  exhausting  the  aqueous  layer,  the  same  well  may  yield  only  petroleum. 

xThe  sinking  of  a  well  is  begun  with  a  boring  35-40  cm.  in  diameter  by  means  of  suitable 
boring  tools  worked  by  long  rods  and  toothed  gearing,  or  by  compressed-air  drills  mounted 


BORING    FOR    PETROLEUM 


65 


FIG.  79. 


on  wooden  structures  termed  derricks  (Fig.  80)  ;    the  detritus  of  the  bored  rock  is  con- 
tinually carried  away  from  the  boring  by  a  current  of  water,  whilst  in  former  times  the 

much    slower    dry    boring    was    preferably   employed.      When    the    petroleum   layer   is 

approached,  the  water  of  the  well  or  tube  begins  to  show  drops  of  petroleum.      The 

power  is  often  supplied  by  portable  steam-engines,  which  should  not  be  placed  too  near 

the  boring,  since  if  the  petroleum  or  gas  escapes  accidentally  in  any  quantity  during  the 

boring,  it  may  ignite  and  cause  considerable  damage  by  fire  or  explosion. 

In  such  cases  it  is  hence  advisable  to  transform  the 
energy  on  the  site,  for  instance,  with  electric  motors. 
And  even  then  fires  and  explosions  have  been  caused 
by  the  accidental  ignition  of  the  gas  mixed  with  air,  by 
sparks  formed  by  stones,  issuing  violently  from  the  well 
along  with  sand  and  petroleum  and  striking  the  iron 
framework  or  the  rails  of  the  woodwork.1 

When  the  petroleum  is  not  exuded  under  pressure,  it 
is  often  raised  by  means  of  pumps,  but  this  is  not 
possible  where  much  sand  (up  to  30  per  cent.)  is  also 
extracted  and  has  to  be  allowed  to  deposit  ;  this  is 
the  case  at  Baku,  where,  however,  one-third  of  the 

petroleum  issues  under  pressure. 

During  recent  years  there  have  remained  relatively  few  "  fountains  "  at  Baku,  and 

the  petroleum  of  the  sandy  wells,  which  cannot  be  raised  by  pumps,  is  extracted  by  special 

"  bailers  "  made  of  a  cylinder  of  sheet- 
metal  terminating  in  a  cone  and  fitted 

in  the  lower  portion  with  a  valve  which 

opens  when  the  bailer  (called  a  shalonka) 

becomes  immersed  in  the  petroleum  and 

closes  on  raising   by  means  of  pulleys 

and   windlass,  the   steel  rope    carrying 

the  bailer  being  wound  round  a  large 

drum  a  short  distance  from   the  well. 

The  shalonka,  containing   some   hecto- 
litres  of    petroleum,   is   discharged    by 

inverting  it  over  a  channel. 

From  the  large  reservoir  near  the 

wells,  the  petroleum  passes  by  means 

of  iron  pipes  to  the  refineries  or  to  the 

despatching  stations  (suitable  trains  or 

vessels),  which  at  Baku  are  very  near, 

but    in     America    some    hundreds    of 

kiloms.  from  the  wells  ;  these  pipes  then 

traverse  plains,  mountains,  and  valleys, 

and    in    the    same  way   and   with    the 

help  of  powerful  pumping-stations,  the 

refined  petroleum  is  despatched  to  the 

place  of  loading.    In  1905,  the  Standard 

Oil  Company  began  the  construction  of 

another  such  pipe  (pipe-line)  to  connect  FIG.  80. 

the  works  at  Kansas  City  with  the  coast ; 

the   distance   is   about   1700   miles   and  the  construction   cost  £880,000  and  served  to 

transport  daily  from  10,000  to  15,000  barrels  of  petroleum. 

1  Artesian  wells  for  extracting  petroleum  have  an  average  diameter  of  25  to  50  cm.,  and  vary  in  depth  according 
to  the  region  ;  at  Baku  they  were  first  of  all  60  to  150  metres  deep.  But  of  recent  years  wells  have  usually  been 
sunk  to  a  depth  of  250  to  350  metres  (occasionally  1000  metres).  In  the  Washington  district  of  the  United  States 
the  wells  are  from  700  to  850  metres,  and  near  Pittsburg  is  the  deepest  of  all,  1820  metres.  The  wells  are  100  to 
200  metres  apart  according  to  the  locality,  and  they  remain  active  for  five  to  ten  years. 

The  expense  of  boring  varies  with  the  district,  that  is,  with  the  nature  of  the  subsoil,  and,  under  favourable 
conditions  and  for  wells  not  too  deep,  each  boring  costs  about  £400.  Those  made  in  the  Washington  district 
cost  even  £1400  to  £1600.  At,  Velleia  in  the  province  of  Piacenza,  the  wells  are  little  more  than  100  metres  deep, 
whilst  at  Salsomaggiore  they  have  been  bored  to  a  depth  of  400  metres,  and  in  one  case  of  700  metres,  in  order  to 
utilise  for  medical  purposes  the  iodine-salt  water  whiphis  obtained,  together  with  alittle  petroleum.  Jn  America  the 

ii  5 


66 


ORGANIC    CHEMISTRY 


Boiling-point 

Specific  gravity 

40-70°     .  . 

0-635-0-660 

70-80°     .  . 

0-660-0-667 

80-100°   .  . 

0-667-0-707 

100-120°   .. 

0-707-0-722 

120-150°  .. 

0-722-0-737 

150-200° 
200-250° 
250-300° 


above  300° 


0-753-0-864 


FIG.  81. 


DISTILLATION.  Crude  petroleum  cannot  be  used  as  it  is  for  lighting,  as  it  has 
a  bad  smell  and  colour,  contains  many  impurities,  and  is  composed  partly  of  too  volatile 
products,  which  might  easily  cause  explosions  or 
fires  in  the  lamps.  In  order  to  avoid  these  dangers, 
the  petroleum  is  subjected  to  exact  refining,  which 
is  controlled  by  legal  enactments  and  with  special 
apparatus  (see  later). 

The  refining  is  carried  out  in  a  manner  which 
varies  with  the  nature  of  the  petroleum  and  usually 
consists  of  a  fractional  distillation  and  a  chemical 
purification.  The  fractional  distillation  in  the 
laboratory  is  carried  out  in  Engler  flasks  (Fig.  81 ), 
which  are  of  definite  size  and  shape  and  permit 
of  concordant  results  being  obtained  in  all  labo- 
ratories ;  the  following  fractions  are  then  weighed  separately  : 

I.  Light  or  readily  volatile  petroleums  : 

(a)  Petroleum  ether         ..... 

(b)  Gasolene          ...... 

(c)  Benzine  ,          .          .    •      .  „ 

(d)  Ligroin  (burnt  in  special  lamps  for  lighting) 

(e)  Petroline  (used  for  de-fatting  or  cleaning)    . 

II.  Petroleum  for  lighting  : 

I  quality      ....... 

II  quality  ...... 

III  quality  ....... 

III.  Residues  of  the  distillation  : 

(a)  Heavy  oils :  lubricating  oils       .         •. 

(b)  Paraffin  oil  .          .          .          . 

(c)  Coke 

The  industrial  refining  of  petroleum  consists  in  separating  the  crude  petroleum  into 
these  three  groups,  I,  II,  and  III. 

Apparatus  is  used  for  periodic  or  alternate  distillation,  or  for  continuous  distillation. 

Periodic  distillation  is  conveniently  carried  out  in  the  so-called  waggon-still  largely  used 
in  America  and  at  Baku.  It  holds  as  much  as  2500  barrels  at  a  time  (Figs.  82  and  83). 

It  is  made  of  wrought  iron  10-14  mm.  in  thickness,  and  has  a  corrugated  bottom  ; 
it  is  commonly  7  metres  long,  4  metres  wide,  and  3  metres  deep.  The  top  is  fitted  with 
three  flanged  elbows  which  carry  off  the  vapour.  In  thirty  hours  three  distillations  can 
be  carried  through,  the  residues  being  discharged  through  the  three  orifices,  c.  The 
heating  is  effected  by  means  of  these  residues,  which  are  forced  into  perforated  pipes,  r, 
in  the  double-arched  hearth  ;  rational  circulation  of  the  products  of  combustion  results  in 
effective  utilisation  of  the  heat. 

More  profitable  use  is  made  to-day  of  simpler,  cylindrical  boilers,  which,  although  of 
larger  dimensions,  correspond  almost  exactly  with  the  various  types  of  steam-boilers, 
the  heating  being  external,  or  lateral,  or  internal,  or  two  of  these  together.  Such  boilers 

well  is  widened  at  its  lowest  jpoint,'  where  it|  meets  ,the]  petroleum,  by  'exploding  a  dynamite  cartridge  ("tor- 
pedoing ")• 

A  well  sunk  in  1891  at  Balakhany,  270  metres  deep,  gave  an  uninterrupted  jet  producing  3276  tons  of  petroleum 
per  twenty-four  hours,  and  the  mass  of  sand  expelled  covered  the  whole  neighbourhood.  A  little  distance  away 
one  of  the  Nobel  Company's  wells,  in  1892,  gave  13,000  tons  per  day.  In  February  1893  a  well  was  sunk  at 
Romany,  near  Baku,  which  for  several  weeks  yielded  10,000  tons  of  petroleum  per  day  ;  the  oil  issued  from  the 
earth  with  such  violence  that  the  movement  of  the  air  broke  the  windows  of  neighbouring  houses,  and,  as  at  first 
it  was  not  possible  to  guide  the  jet  into  horizontal  channels,  all  the  iron  plates  used  for  this  purpose  being  pierced, 
250,000  tons  of  petroleum  were  lost  in  five  weeks  In  1909  a  new  well  at  Baku  gave,  for  a  long  time,  3500  tons  of 
naphtha  per  day.  A  well  bored  at  Maikop  (70  kiloms.  from  the  Black  Sea),  on  September  12,  1910,  to  a  depth  of 
70  metres,  gave  a  jet  64  metres  above  the  surface  of  the  ground  and  a  production  of  6000  tons  in-  twenty-four  hours  ; 
on  September  18  the  fountain  caught  fiie  and  five  days  passed  bef6re  it  could  be -extinguished. 

Fountains  as  rich  as  this  are  exceptional ;  usually  wells  yield  much  less,  and  at  Baku  a  well  is  generally  abandoned 
when  it  gives  less  than  four  tons  in  twenty-four  hours.  In  Italy,  however,  wells  are  used  which  give  only  a  few 
hundredweights  of  petroleum  per  day ;  some  of  the  Italian  wells  produce  only  60  litres  a  day,  others  as  much  as 
2500  litres  or  more 


0-7446-0-8588 
0-8588-0-9590 


DISTILLATION    OF    PETROLEUM 


67 


of  600-700  or  more  barrels  capacity  are  commonly  used  even  in  America,  where,  however, 
both  the  more  complex  and  more  perfect  Lugo  apparatus  and  the  Rossmassler  apparatus, 
in  which  the  heating  is  effected  by  superheated  steam,  are  used. 

For  the  condensation  of  the  vapours  that  distil  over,  complicated  iron  coils  are  arranged 
in  cisterns  through  which  cold  water  circulates  continuously,  the  bore  of  the  pipe  being 
20-25  cm.  at  first  and  gradually  diminishing  to  5-8  cm. 

The  distillate  with  specific  gravity  not  exceeding  0-750  and  b.pt.  150°  forms  the  crude 
benzine  and  is  collected  and  worked  up  separately.  The  distillate  with  sp.  gr.  0-750-0-860 
forms  the  lighting  oil,  and  the  residue  is  treated  separately. 


FIG.  82. 


FIG.  83. 


Continuous  distillation  is  employed  more  especially  at  Baku,  with  large  plants  con- 
sisting of  boilers  arranged  in  series  so  that  each  boiler  is  maintained  at  a  definite,  constant 
temperature,  the  vapours  passing  from  one  boiler  to  the  other  only  depositing  in  a  con- 
densed form  those  portions  corresponding  with  a  given  boiling-point  and  a  given  specific 
gravity.  By  feeding  the  first  boiler — which  is  at  the  highest  temperature — continuously, 
the  others  are  also  fed  indirectly  and  kept  full,  each  of  them  discharging  a  fraction  of  a 
definite,  constant  specific  gravity.  Naturally  the  higher  temperature  boilers  are  furnished 
with  dephlegmators  (Fig.  84),  which  cause  ready  deposition  of  the  heavy  oil  carried  over 
with  the  very  hot  vapours.  In  these  boilers  the  heating  or  distillation  is  effected  by 


FIG.  84. 


FIG.  85. 


means  of  superheated  steam,  which  is  usually  obtained  by  passing  steam  from  a  boiler 
(D,  Fig.  85)  through  a  series  of  iron  pipes  heated  in  a  furnace  by  direct-fire  heat. 

In  addition  to  other  advantages,  continuous  distillation  gives  an  increase  of  30  per 
cent,  in  the  amount  of  solar  oil.  The  residue  left  after  distilling  the  crude  petroleum  up 
to  280°  bears  the  Tartar  name  of  masut  or  the  Russian  one  of  astatki  (ostatki).  The  amount 
of  petroleum  distilled  in  twenty-four  hours  corresponds  with  four  times  the  capacity  of  all 
the  boilers  in  the  battery. 

The  Nobel  Company  at  Baku  has  boilers  which  distil  1000  tons  of  petroleum  in  twenty- 
four  hours.  During  recent  years  rectifying  columns  similar  to  those  used  for  alcohol 
have  been  employed,  these  admitting  of  a  large  production  without  the  use  of  large 
boilers. 

In  the  "  Black  Town  "  near  Baku,  there  are  200  refineries  which  treat  the  whole  of  the 


68 


petroleum  of  the  district.  The  odour  of  petroleum  is  perceptible  at  a  great  distance,  and 
the  town  is  always  covered  and  surrounded  with  dense,  black  smoke.  The  most  important 
refinery  is  that  of  Nobel  Brothers,  which  refines  half  of  the  annual  output  of  the  Caspian, 
although  this  firm  possesses  only  one -eighth  of  the  total  number  of  wells. 

CHEMICAL  PURIFICATION  OF  PETROLEUM.  The  petroleum  distilling  between 
150°  and  300°  is  not  yet  suitable  for  lighting  purposes,  as  it  has  a  marked,  rather  un- 
pleasant odour  ;  it  has  a  faint  yellow  colour,  and  contains  substances  which  detract  from 
its  value.  It  was  Eichler  at  Baku  who  first  suggested  purification  by  means  of  concen- 
trated sulphuric  acid. 

This  is  carried  out  in  large  iron  tanks  with  conical  bases  (Fig.  86),  the  petroleum  being 
treated  with  several  separate  quantities  (altogether  1-3  per  cent.)  of  concentrated  sulphuric 

acid  of  66°  Be.  (nowadays  the  mono- 
hydrate  obtained  by  the  catalytic  process), 
the  mixture  being  vigorously  agitated  by 
compressed  air  blown  in  at  the  bottom  of 
the  tank,  and  each  quantity  of  the  acid 
separated  after  half  an  hour's  rest. 

The  sulphuric  acid  acts  especially  on 
the  aromatic  hydrocarbons  (forming  sul- 
phonic  acids),  the  defines  and  the  oxy- 
genated acid  compounds,  as  well  as  on 
the  colouring  and  sulphur  substances. 
A  small  part  (1-3  per  cent.)  of  the  petro- 
leum is  resinified  and  the  acid  is  turned 
black,  but  can  still  be  used  for  the  manu- 
facture of  superphosphates. 1  In  order  to 
weaken  the  action  of  the  acid  somewhat, 
it  is  mixed  with  sodium  sulphate  ;  further, 
in  order  that  yellowing  of  the  petroleum 
may  be  avoided,  sulphuric  acid  contain- 
ing less  than  0-01  per  cent,  of  nitrous  acid 
should  be  employed.  After  the  action 
of  the  acid,  the  petroleum  is  washed 
thoroughly  with  water  and  then  with 
1-1-5  per  cent,  of  concentrated  caustic 
soda  solution  (30-33°  Be.),  air  being 
FIG.  86.  passed  in  from  beneath  to  effect  mixing  ; 

in  this  way  the  traces  of   acid  remaining 

and  also  the  phenolic  compounds  are  removed.  After  the  alkali  has  been  separated,  the 
oil  is  again  well  washed  with  water.  The  remaining  petroleum  is  not  clear,  as  it  is 
emulsified  with  a  little  water,  but  it  clarifies  on  standing  and  on  being  filtered  rapidly 
through  sawdust  and  salt,  which  remove  all  traces  of  emulsion.  The  alkaline  petroleum 
residues  are  now  used  in  some  places  to  impregnate  and  preserve  railway  sleepers ;  but 
sometimes  they  are  subjected  to  dry  distillation,  which  regenerates  the  soda  and  gives 
coke  and  unsaturated  hydrocarbons  and  ketones  (acetone,  &c.).  The  heating  of  these 
alkaline  residues  also  yields  naphthenic  acids  (tridecanaphthenic  acid),  from  which  cheap 
antiseptic  soaps  are  prepared. 

Some  crude  petroleums  give  a  rather  yellow  solar  oil,  which  is  decolorised  by  exposure 
for  some  time  to  the  sun  in  shallow  tanks  covered  with  sheets  of  glass.  Sometimes  the 
yellow  tint  is  removed  by  dissolving  in  the  petroleum  traces  of  complementary  blue  or 
violet  dyes  ;  as,  however,  nearly  all  commercial  dyes  are  insoluble  in  petroleum,  it  is 
necessary  to  obtain  from  the  manufacturers  the  bases  of  these  colouring-matters,  these 
being  soluble. 

In  certain  cases,  decolorisation  is  attained  with  infusorial  earths,  clays,  or  natural 
magnesium  hydrosilicates. 

A  most  important  operation  for  petroleum  rick  in  sulphur  (present  especially  as  H2S) 

1  According  to  Ger.  Pat.  221,615  of  1909  this  black  acid,  containing  sometimes  as  much  as  2-5  per  cent,  of 
complex  organic  substances,  may  be  purified  by  causing  it  to  fall  into  pure,  boiling  sulphuric  acid  through  which 
a  current  of  air  is  passed  ;  all  the  acid  distilling  over  is  then  pure  and  colourless.  J.  Fleischer  (1907)  obtains  colour- 
less acid  (45°  to  50°  B$.)  by  causing  the  black  acid  to  diffuse  through  porous  partitions  washed  by  a  little  water. 


DESULPHURISING    OF    PETROLEUM 


69 


and  hence  dark  and  of  unpleasant  odour  (like  those  from  Canada,  which  can  be  used 
only  as  a  combustible  and  not  for  lighting  purposes)  is  that  of  a  desulphurising  according 
to  the  process  proposed  by  Frasch  (1888-1893)  ;  this  consists  in  distilling  the  petroleum 
with  an  excess  of  a  mixture  of  metallic  oxides — powdered  copper  oxide,  75  per  cent.  ; 
lead  oxide,  10  per  cent.  ;  iron  oxide,  15  per  cent.  This  operation  reduces  the  sulphur- 
content  from  0-75  per  cent,  or  more  to  0-02 
per  cent.  It  is  calculated  that,  by  this 
method,  about  50  tons  of  sulphur  are 
extracted  daily  from  Ohio  petroleum, 
most  of  it  being  lost. 

The  operation  is  carried  out  by  simple 
mixing  or  by  means  of  vapour.  In  the  first 
case  6800  kilos  (68  quintals)  of  the  oxide 
mixture  are  added  to  200  tons  of  petroleum 
in  a  large  tank,  the  mixture  being  sub- 
jected to  prolonged  agitation  by  mechanical 
stirrers,  which  keep  the  oxidising  mass  at 
the  bottom  of  the  tank  in  continual  motion. 

The  petroleum  is  then  decanted  off  into 
the  fractional  distilling  apparatus,  a  second 
quantity  of  200  tons  of  petroleum,  together  FIG.  87. 

with    4500    kilos  (45  quintals)  of   oxides 

being  added  to  the  residue  in  the  tank  ;   the  operation  is  repeated  four  or  five  times 
before  renewing  the  oxides  completely. 

The  Frasch  process  of  desulphurising  the  vapour  is  far  more  rational  and  rapid  ;  it 
consists  in  passing  the  petroleum  vapours  from  the  distillation  vessel  (from  100  tons  of 
petroleum)  (A,  Fig.  87)  successively  into  two  communicating  cylinders,  B  and  C,  placed 
one  over  the  other  and  enclosed  by  a  metal  casing,  D,  above  the  boiler.  The  vapours 
pass  first  into  the  casing,  next  into  the  lower  cylinder,  and  then  into  the  upper  one,  coming 
into  intimate  contact  with  the  mixture  of  metallic  oxides,  which  are  kept  moving  and 
subdivided  in  both  cylinders  by  means  of  rotating  reels,  h,  provided  with  peripheral 
brushes,  H.  The  oxidising  mixtures  in  the  two  cylinders  are  renewed  alternately,  while 
the  purified  vapours,  after  traversing  a  gravel  filter,  G,  which  retains  particles  of  the 
oxides  carried  over,  are  condensed  in  ordinary  coils,  F.  By  this  process,  some  refineries 
are  able  to  purify  as  much  as  11,000  tons  of  petroleum  per  day. 


FIG.  88. 


FIG.  89. 


Recently  petroleum  has  been  desulphurised  by  means  of  metallic  sodium,  and  treatment 
with  aluminium  chloride  in  the  hot  and  under  pressure  is  also  recommended.  V.  Walker 
(U.S.  Pat.  955,372,  1910)  passes  the  vapours  into  columns  fitted  with  perforated  plates  and 
containing  anhydrous  cupric  chloride,  the  last  traces  of  hydrogen  sulphide  being  removed 
by  passing  the  vapours  into  a  solution  of  lead  oxide  in  caustic  soda.  Robinson  (1909) 
separates  the  sulphur  by  treating  the  petroleum  with  highly  concentrated  sulphuric  acid. 

In  well-refined  petroleums,  the  proportion  of  sulphur  is  always  less  than  0-06  per 
cent.,  usually  0-02  per  cent. 

PETROLEUM  TANKS.  The  refined  petroleum  is  preserved  in  large  cylindrical 
sheet-metal  tanks  (Fig.  88),  situated  near  the  works  ;  they  are  whitened  outside  to  reflect 


70 


ORGANIC    CHEMISTRY 


the  heat  of  the  sun,  and  are  furnished  with  charging  and  discharging  pipes  communicating 
with  the  pumping-station  by  which  all  the  liquids  in  the  works  are  circulated. 

For  transport  by  land  and  sea,  wooden  casks  holding  159  litres  (about  145  kilos)  were 
at  one  time  exclusively  used,  but  to-day  land  transport  is  effected  by  tank-cars  (Fig.  89), 
which  are  now  numbered  in  hundreds  of  thousands.  For  sea  transport,  tank-steamers 
are  used  (there  are  now  360  of  these  of  the  total  capacity  of  630,000  tons)  (Fig.  90)  ;  when 
they  arrive  at  their  destinations  in  the  ports  of  different  countries,  they  are  discharged 
by  means  of  pumps  into  storage-tanks  or  directly  into  tank-cars.  From  these  stores 
(there  are  tanks  of  2000  tons  capacity  at  Leghorn,  Savona,  Genoa,  and  Venice)  it  is 
dispatched  inland  in  wooden  or  iron  casks  or  in  cans  holding  14  kilos  (17  litres)  and  packed 
in  pairs  in  wooden  cases. 


'    FIG.  90. 
Carbone,  coal ;  j>etrolio,  petroleum ;  macchine  e  caldaie,  engines  ancfboilers. 


USES  AND  STATISTICS.  The  greater  part  of  refined  petroleum  is  still  used  for 
lighting  purposes,  either  in  the  old  lamps  with  flat  wicks  or  in  those  with  cylindrical 
wicks  and  flame -spreaders  or  in  lamps  with  incandescent  Auer  mantles  ;  it  can  be  used 
advantageously  for  household  illumination  in  town  and  country.  Part  of  it  is  employed 
for  power  purposes,  as  in  internal -combustion  engines  it  gives  an  efficiency  of  25-37  per 
cent.,  whilst  coal  yields  only  12  per  cent.  However,  while  in  Russia  large  quantities  of 
petroleum  were  used  in  the  past  in  factories  and  for  locomotives,  nowadays  it  is  being 
replaced  by  coal  ;  in  America,  on  the  other  hand,  the  opposite  is  the  case,  and  the  Mexican 
Railway  alone  consumed  more  than  4000  barrels  of  petroleum  per  day  for  its  locomotives 
in  1908.  Its  use  on  fast  ships  has  the  advantage  of  28  per  cent,  saving  in  space.  In 
America,  about  19,000,000  barrels  of  petroleum  were  used  altogether  for  railway  loco- 
motives in  1907.  Lastly,  it  is  used  as  a  disinfectant  and  for  lubricating  engines,  &c. 

The  production  of  petroleum  has  increased  in  a  surprising  manner,  in  spite  of  the 
growing  development  of  the  gas  and  electrical  industries.  The  following  figures  illustrate 
this  for  the  two  great  petroleum -producing  regions  : 


In  1874 
1884 
1894 
1903 
1905 
1908 
1910 


Caucasus  (Russia) 
Tons 
100,000 

1,500,000 
5,000,000 
9,902,000 
7,969,239 
8,292,000 
9,500,000 


United  States 

Tons 

1,500,000 

3,400,000 

7,000,000 

13,160,006 

17,636,000 

23,940,000 

26,000,000 


In  America  to-day  petroleum  is  monopolised  by  huge  "  trusts,"  especially  the  Vacuum  Oil  Company  and  the 
Standard  Oil  Company  of  New  Jersey,  to  which  are  affiliated  seventy  companies  with  a  total  capital  of  £18,000,000 
and  employing  60,000  workmen  and  monopolising  about  60  per  cent,  of  American  petroleum.  The  Standard 
Oil  Company,  founded  in  1872,  paid  in  dividends  from  1882  to  1892  a  total  of  £94,400,000,  and  from  1894  to  1903 
paid  to  its  shareholders  dividends  of  33  to  48  per  cent.  1  In  1906  President  Roosevelt,  under  pressure  of  public 
opinion,  waged  war  against  this  colossal  [trust  by  rupturing  the  connection  between  the  steel  ring  and  the  interests 
bound  up  with  it  and  making  them  liable  to  a  fine  of  over  £6,000,000.  In  consequence  of  this  commercial  war  of 
1906  the  Standard  Oil  Company  lost  £25,000,000,  of  which  £12,900,000  fell  on  Rockefeller,  the  well-known  millionaire 
president  of  the  company.  The  sentence  was  then  annulled  on  appeal,  but  the  result  was  that  the  company 
fought  its  competitors  by  lowering  prices  (petroleum  that  previously  cost  30  centesimi  (2-9d.)  per  litre  has  been 
lowered  in  price  during  the  last  few  years  to  15  centesimi  (l-45rf.)  ),  and  in  1908  made  a  net  profit  of  £16,000,000, 
and  proposed  raising  its  capital  to  £100,000,000.  This  explains  how  Rockefeller  has  been  able,  without  any  great 
sacrifice,  to  make  benefactions  of  so  many  millions  during  the  past  few  years,  especially  for  the  extension  of  university 
study  in  America.  The  last  sentence  of  the  Supreme  Court  of  Washington  (May  15,  1911)  gave  judgment  against 
the  Standard  Oil  Company,  for  contravention  of  the  law  against  trusts,  and  ordered  dissolution  of  this  powerful 
company  within  six  months. 


PETROLEUM    STATISTICS 


71 


One-third  of  the  American  production  has  been  given  by  California,  more  than  one- 
fourth  by  Texas,  and  one-sixth  by  Ohio,  and  now  one-sixth  is  given  by  Illinois,  one- 
fourth  by  California,  and  one-fourth  by  Oklahoma.  In  1910  the  Calif ornian  production 
reached  almost  10  million  tons. 

The  total  production  of  the.  world  was  about  12,000,000  tons  in  1894,  31,000,000  in 
1905,  and  38,000,000  in  1908.  The  following  Table  gives,  in  the  first  three  columns  the 
production  in  thousands  of  tons  of  each  of  the  petroleum -producing  countries  of  the 
world,  and  in  the  last  three  columns  the  percentages  of  the  total  amounts  yielded  by  each 
country  : 


1903 

1905 

1908 

Per  cent,  of  the  total  production 

1900 

1902 

1908 

United  States   . 
Russia 
Dutch  East  Indies     . 

13,600 
9,902 

870 

20,000 
7,969-2 
1,126-3 

23,940 
8,292 
1,143 

51-50 
42-41 
1-83 

52-51 
37-12 
3-50 

63-0 
21-8 
3-0 

Galicia 

728 

835-8 

1,754 

1-97 

2-90 

4-6 

Roumania1 

381 

641-0 

1,148 

0-85 

1-74 

3-0 

British  India     . 

329 

599-8 

672 

0-87 

1-42 

1-7 

Japan 
Canada     . 

126 

194-4 
91-9 

276 

70-5 

0-86 
0-18 

0-50 
0-24 

0-75 
0-20 

Germany 
Italy         .          . 
Peru 

58-9 
2-5 

81-3 
6-1 
5-4 

141-9 

7-08 
135 

0-35 
0-02 
0-35 

Various  other  countries 

79-0 

In  1890,  Germany  produced  only  15,000  tons  of  crude  petroleum. 

The  country  that  consumes  the  most  petroleum,  after  the  United  States  and  Russia, 
is  Germany,  where,  in  1904,  970,600  tons  were  used  for  lighting,  143,000  tons  for  lubri- 
cating purposes,  and  110,000  tons  for  various  other  uses  ;  in  1909,  it  imported  about 
950,000  tons  of  refined  petroleum  and  31,400  tons  of  crude  petroleum,  of  a  total  value  of 
£3,600,000. 

The  importation  into  Italy  has  been  as  follows  : 

1884  1890  1900  1904  1906  1907  1908  1909  1910 

Tons     .     73,361     72,000     73,000     69,233     61,588     72,714    82,373     88,930     84,748 

and  whilst  in  1907  two-thirds  of  this  came  from  the  United  States,  one-fourth  from 
Russia,  and  little  from  Roumania,  after  the  new  commercial  treaty  with  the  last  two 
nations,  the  proportions  changed  considerably,  Roumania  alone  sending  29,000  tons  in 
1909. 

Almost  the  whole  of  the  Italian  industry  is  in  the  hands  of  one  company,  and  the 
production  is  very  small  and  almost  stationary. 

The  consumption  of  petroleum  by  different  countries  is  quite  different  proportionately 
from  the  production,  as  is  shown  in  the  following  Table,  which  gives  the  mean  consump- 
tion per  inhabitant  in  1904  : 


United  States  .. 

Germany 

England         .          . 

France 

Russia  (140,000,000  inhabitants) 

Japan  .          .          .• 


Total  consumption 

Tons 
2,016,700 

970,600 
520,933 
312,210 

1,050,787 
299,370 


Annual  consumption 

per  inhabitant 

Kilos 

25-21 
16-72 
11-84 

8-22 

7-51 

6-65 


1  In  1910  the  production  was  1,352,300  tons,  339,300  tons  of  distilled  petroleum  and  125,750  tons  of  benzine 
being  exported.  In  1903  the  refineries  of  Roumania  treated  altogether  314,748  tons  and  in  1904  391,387  tons  of 
crude  petroleum,  which  yielded  62,218  tons  of  benzine,  109,510  tons  of  lighting  oil,  30,214  tons  of  mineral  oil,  and 
173,661  tons  of  residues.  In  1909  Koumania  exported  420,000  tons  of  petroleum  benzine,  and  mineral  oils. 


ORGANIC    CHEMISTRY 


Roumania     .          .          . 
Austria -Hungary   .         . 
Italy    .          .          .          . 
India  (300,000,000  inhabitants) 
ghina  (300,000,000  inhabitants) 


Annual  consumption 
Total  consumption          per  inhabitant 

Kilos 
4-50 


Tons 

27,025 

215,546 

73,000 

503,930 

254,464 


4-31 
2-21 

1-70 

0-85 


The  units  of  measure  of  petroleum  in  different  countries  have  already  been  given  on 
p.  58. 

In  view  of  the  enormous  and  increasing  consumption  of  petroleum,  it  may  be  interesting 
to  know  how  much  longer  the  known  stock  of  petroleum  in  the  earth  will  last.  According 
to  the  calculations  made  in  1909  by  the  Geological  Survey  Office,  the  known  deposits 
of  petroleum  would  last  until  1990  if  the  annual  consumption  remained  at  its  present 
amount,  but  if  the  consumption  increases  in  the  same  proportion  as  it  has  been  doing 
during  the  last  few  years,  the  deposits  will  be  exhausted  in  1935. 

The  price  of  rectified  petroleum  at  Batoum  is  about  7s.  2d.  per  quintal,  and  the  trans- 
port to  Genoa  Is.  5d.,  and,  making  allowance  for  all  taxes,  Russian  petroleum  costs  at 
Genoa  16s.  per  quintal,  including  the  cask  ;  the  American  costs  16s.  I0d.,  and  at  the 
present  time  Russian  petroleum  is  beginning  to  oust  the  American  product  from  the 
European  markets.  In  the  free  port  of  Hamburg,  Russian  and  American  petroleums 
cost  16s.  Wd.  per  quintal  in  1879,  13s.  Id.  in  1890,  and  14s.  Q%d.  in  1904. 

TESTS  FOR  LIGHTING  PETROLEUM.  A  good  petroleum  is  limpid  and  colourless, 
does  not  turn  brown  with  sulphuric  acid  (sp.  gr.  1-53),  and  has  a  specific  gravity  of  0-820- 
0-825  (Russian)  or  0-780-0-805  (American)  ;  the  specific  gravity  is  determined  with  an 
aerometer  at  15°  (corrected  by  0-0007°  for  each  degree)  and  referred  to  water  at  4°.  It 
should  not  have  an  acid  reaction  ;  when  10  c.c.  of  the  petroleum  is  dissolved  in  a  mixture 
of  alcohol  and  ether  previously  rendered  neutral  to  phenolphthalein,  an  immediate  violet 
coloration  should  be  produced  on  addition  of  a  single  drop  of  N/10  alcoholic  caustic  soda. 
When  subjected  to  fractional  distillation  in  the  Engler  flask  (p.  66),  it  should  not  yield 
products  distilling  below  110°,  only  5  per  cent,  or  at  most  10  per  cent,  up  to  150°,  and 
less  than  10  per  cent,  or  at  most  15  per  cent,  above  300°  ;  in  the  distillation  products 
the  difference  in  specific  gravity  between  Russian  and  American  petroleums  is  increasingly 
marked.  American  petroleum  is  distinguished  from  the  Russian  (see  p.  62  et  seq.)  also 
with  the  refractometer  and  by  the  different  solubilities  of  the  fractions  of  equal  specific 
gravity  in  a  mixture  of  chloroform  and  aqueous  alcohol  (Riche-Halphen  test)1.  The 
viscosity  determined  with  the  Engler  viscosimeter  (see  later,  Mineral  Oils)  should  not  be 
greater  than  1-15  at  20°.  The  luminosity  is  determined  with  the  Bunsen  photometer 
(p.  56)  and,  in  general,  3-5-5  grms.  are  consumed  per  candle-hour. 

The  determination  of  the  temperature  at  which  a  petroleum  gives  off  inflammable 
vapours  is  of  great  importance,  and  in  order  to  obtain  concordant  results,  the  Abel  apparatus 
modified  by  Penski  (Figs.  91  and  92)  is  employed  in  all  laboratories.  The  petroleum  to 
be  examined  is  placed  in  a  brass  receiver,  G,  up  to  the  level-index,  h  ;  the  cover,  D  8, 
carries  a  thermometer,  t,  which  dips  into  the  petroleum,  and  a  clockwork  mechanism, 
T  b,  which,  when  it  is  released  (by  a  lever,  h),  opens  automatically  a  small  window  in  the 
cover  ;  at  the  same  instant  a  small  oil-flame  passes  through  the  window  and  is  immediately 
withdrawn,  the  window  then  closing.  The  petroleum  receiver  is  surrounded  by  an  air- 
chamber,  A,  which  is  heated  to  55°  in  the  reservoir,  W,  regulated  by  the  thermometer  t2. 
For  every  0-5°  increase  of  temperature  of  the  petroleum,  the  spring  is  released,  this  being 
continued  until  the  flame  ignites  and  explodes  the  mixed  petroleum  vapour  and  air. 
The  slight  explosion  sometimes  extinguishes  the  flame.  The  temperature  shown  at  this 

1  Of  each  fraction  with  specific  gravity  higher  than  0-760,  4  grms.  is  weighed  into  a  beaker,  and  from  a  burette 
a  mixture  in  equal  parts  of  anhydrous  chloroform  and  93  per  cent,  alcohol  is  run  in  until  the  tuibidity  fiist  foimed 
suddenly  disappears : 

Density       .         .         .          .     0-760      0-770       0-780      0-790      0-800      0-810      0-820      0-830      0-850       0-880 
American   petroleum    (cubic 

centimetres  solvent).          .     4-3          4-6          5-2          5-9          6-6          7-7  9-5         11-3 

Russian     petroleum     (cubic 

centimetres  solvent).          .     4-0          3-d          4-1          4-2          4-0          4-2          4-5          5-0          6-4         11-9 

Italian  petroleums  behave  like  the  Russian,  but  this  reaction  does  not  serve  to  distinguish  between  the  other 
European  petroleums  (Utz,  1905). 


FLASH-POINT    OF    PETROLEUM 


73 


moment  by  the  thermometer  ^  is  that  of  inflammability  (flash-point),  which  is,  however, 
influenced  by  the  atmospheric  pressure  and  should  be  corrected  by  +  0-035°  for  every 
mm.  of  pressure  above  760  mm. 

In  Italy,  Germany,  and  Austria  the  sale  of  petroleum  for  lighting  purposes  is  prohibited 
if  it  shows  a  flash-point  below  21°  in  the  Abel  apparatus  ;  otherwise  explosive  vapours 
could  be  formed  in  ordinary  lamps,  even  at  30°  or  32°,  which  would  be  dangerous. 
A  petroleum  inflammable  at  above,  60°  (Abel)  cannot  be  used  for  lamps. 

A  rough-and-ready  test  to  detect  if  a  petroleum  is  dangerous  consists  in  pouring  a 
little  into  a  glass  and  throwing  into  it  a  lighted  match  ;  if  the  latter  is  extinguished,  the 
petroleum  is  safe. 


FIG.  91. 


FIG.  92. 


The  illuminating  power  is  determined  with  the  Lummer  and  Brodhun  photometer 
(see  Fig.  77,  p.  56).  To  determine  the  moisture  or  water,  which  does  not  separate  well  in 
the  distillation  of  certain  Calif ornian  petroleums,  Robert  and  Fraser  (1910)  proposed 
adding  calcium  carbide  and  measuring  the  quantity  of  acetylene  formed,  this  depending 
on  the  amount  of  water  present. 

TREATMENT  OF  CRUDE  BENZINE 

The  portion  of  crude  petroleum  distilling  below  150°  forms  crude  benzine,  which  can 

be  separated  by  fractional  distillation  into  various  qualities  for  different  commercial  uses. 

The  crude  benzine  is  redistilled  in  small  horizontal  or  vertical  boilers,  usually  heated 

by  superheated  steam  either  in  a  jacket  or  in  closed  coils  inside  the  boiler,  the  condensed 

water  being  collected  outside  the  boiler. 

In  some  cases  moderate  fire-heat  is  used  in  addition. 

When  there  are  many  volatile  products,  an  apparatus  similar  to  that  used  in  the 
rectification  of  spirit  is  employed.  Such  a  system  of  rectifying  columns  is  to-day  in  general 
use,  and  the  condensation  of  the  vapours  and  the  cooling  of  the  condensed  benzine  are 
effected  by  the  crude  benzine,  which  is  thus  fractionated  and  fuel  at  the  same  time 
economised. 

A  special  apparatus  for  condensation  and  rectification,  devised  by  Veith,  consists  of 
five  iron  double-walled  cylinders  (with  water-circulation),  connected  in  series  and  .ter- 
minating in  a  sixth  cylinder  containing  a  coil  with  many  turns  for  the  condensation  of 
the  vapour  from  the  preceding  cylinder.  The  coil  is  cooled  by  ice  and  cold  water,  which 
then  passes  successively  into  the  jackets  of  the  other  five  cylinders  and  gradually  becomes 
heated.  These  five  cylinders  are  full  of  pure  iron  turnings  free  from  oil.  The  vapours 
from  the  boiler  in  which  the  benzine  is  distilled  pass  through  cylinders  1-5,  in  each  of  which 


74  ORGANIC    CHEMISTRY 

that  part  condenses  which  is  liquefied  at  the  temperature  of  the  water  circulating  in  the 
jacket. 

The  least  volatile  products  condense  in  the  first  cylinder  and  the  most  volatile  ones  in  the 
final  coil.  At  the  bottom  of  each  cylinder  is  a  pipe  with  a  tap  communicating  with  a  tank. 

The  apparatus  for  distilling  and  rectifying  benzine  are  so  constructed  that  the  vapour 
above  the  boiling  liquid  which  is  mixed  with  air  is  separated  from  the  liquid,  e.g.  by  metal 
gauze,  so  that  in  case  of  fire  or  explosion  the  liquid  does  not  ignite. 

Baku  petroleums  give  only  0-2  per  cent,  of  benzine,  those  of  Grosny  (Russia)  about 
4-5  per  cent.  In  1902,  341,000  tons  of  naphtha  were  distilled  at  Grosny,  14,000  tons  of 
benzine  (about  4  per  cent.)  being  obtained.  Pennsylvanian  petroleums  give  up  to  12  per 
cent,  of  benzine,  and  those  from  Campina  (Roumania)  3-5  per  cent.  ;  a  petroleum  from 
Anapa  (Caucasus)  gave  28  per  cent.  Italian  petroleums  from  Emilia  yield  30-35  per  cent, 
of  benzine. 

After  the  fractional  distillation  of  the  benzine  the  separate  portions  are  often  refined 
by  treating  with  concentrated  sulphuric  acid  mixed  with  0-2  per  cent,  of  potassium 
dichromate  and  0-01  per  cent,  of  lead  oxide.  Fuming  sulphuric  acid  also  gives  good 
results,  but  animal  charcoal  and  magnesium  hydrosilicates  are  not  very  satisfactory. 
The  treatment  is  carried  out  in  closed  vessels  with  mechanical  stirrers,  the  use  of  com- 
pressed air  being  inapplicable  here. 

The  majority  of  the  benzine  is  produced  at  Baku  and  in  Pennsylvania,  but  some  is 
refined  in  Germany  and  large  quantities  are  sent  to  Europe  from  the  East  Indies — from 
Java,  Sumatra,  and  Borneo  ;  Galicia  and  Roumania  also  yield  large  quantities. 

The  consumption  of  benzine  is  to-day  tending  to  increase,  not  only  as  a  solvent  for 
fats  (benzine  boiling  between  60°  and  80°),  but  also  for  automobiles,  aeroplanes,  and 
dirigible  balloons,  its  calorific  value  (about  11,000  cals.)  being  high.  That  used  for  cleaning 
fabrics  should  boil  at  a  higher  temperature,  otherwise  it  evaporates  too  easily  and  leaves 
an  annular  mark  round  the  spot  (other  varieties,  see  p.  66). 

The  consumption  of  benzine  in  the  various  countries  of  Europe  amounted  in  1908  to  : 
115,000  tons  in.  Germany,  130,000  tons  in  Trance,  100,000  tons  in  England,  10,000  tons 
in  the  Netherlands,  110,000  tons  in  Russia,  20,000  tons  in  Roumania,  10,000  tons  in 
Austria  and  Galicia,  and  25,000  tons  in  other  European  countries.  The  United  States 
produced  800,000  tons  of  benzine  in  1908  and  the  Dutch  Indies  260,000  tons. 

TREATMENT  OF  PETROLEUM   RESIDUES 
A.  Lubricating  Oils.     B.  Vaseline.    C.  Paraffin. 

(A)  LUBRICATING  OILS.  The  crude  petroleum  residue  remaining  in  the  boilers 
at  300°  (astatki  or  masut  1)  forms  a  brownish  black  mass  with  a  greenish  reflection,  dense 
and  sometimes  semi -solid  at  ordinary  temperature,  and  often  with  a  burnt,  faintly  creosotic 
smell  ;  it  has  a  specific  gravity  of  0-900-0-950  and  a  coefficient  of  expansion  of  0'00091, 
and  gives  inflammable  vapour  even  at  120-160°  ;  that  of  Baku  contains  no  paraffin  and 
hence  does  not  freeze.  When  these  residues  are  discharged  from  the  boiler,  in  order  to 
cool  them  and  so  prevent  them  taking  fire  they  are  passed  through  the  tubes  which  serve 
to  heat  the  crude  petroleum  before  introducing  it  into  the  boiler.  At  Baku  the  residues, 
which  form  almost  two-thirds  of  the  crude  naphtha,  are  largely  used  as  a  combustible  for 
the  distillation  vessels  and  also  for  locomotives  and  marine  engines,  the  calorific  power 
being  9700-10,800  cals.  and  1  kilo  being  able  to  evaporate  as  much  as  14-15  kilos  of  water.2 

1  Masut  contains,  on  the  average,  87-5  per  cent.  C,  11  per  cent.  H,  and  1-5  per  cent.  O ;    it  has  a  mean 
specific  gravity  of  0-91,  an  ignition  temperature  of  110°  and  a  calorific   value  of   10,700   cals.      When   used 
as  a  combustible  it  is  gasified,  the  vapours,  mixed  with  compressed  air,  burning  completely  ;   it  is  often  burnt 
directly  after  pulverisation  with  compressed  air  or  steam. 

In  view  of  the  great  calorific  value  of  petroleum  residues  and  their  increasing  production,  new  outlets  have  been 
sought  for  them  ;  they  should  have  a  great  future  as  a  substitute  for  coal  in  the  heating  of  boilers,  steam-engines, 
ships,  &c. 

But,  as  has  been  already  stated,  this  use  of  it  is  diminishing  in  Russia,  although  continually  extending  in 
the  United  States.  In  Italy  attempts  have  recently  (1911)  been  made  to  burn  it,  after  pulverisation,  directly 
under  boilers,  and  it  can  be  used  advantageously  if  it  does  not  cost  "at  the  factory  more  than  about  5s.  per  quintal, 
coal  giving  8000  cals.  costing  2s.  lOd.  ;  the  cost  of  transport  is  hence  excessive,  increasing  the  price  from  lOd. 
or  15rf.  at  the  refinery  to  5s.  in  Italy.  The  Customs  duty  (Italy)  is  20  centesimi  (just  under  2<J.)  per  quintal. 

The  heavy  oils  extracted  from  petroleum  residues  are  largely  used  for  special  engines  of  the  Diesel  type. 

2  "Cracking"  Process.     In  some  cases  it  is  convenient  to  convert  the  heavy  mineral  oils  (and  also 
the  masut)  into  petroleum  for  lighting,  use  being  made  of  the  process  of  cracking.     This  is  based  on  the  fact, 


PETROLEUM    RESIDUES 


75 


Utilisation  of  a  great  part  of  these  residues  was  commenced  after  the  first  American 
and  Scotch  samples  (from  shale  oils)  were  exhibited  at  the  International  Exhibition  at 
Paris  in  1867.  In  Russia  enormous  quantities  of  residues,  of  almost  no  commercial  value, 
accumulated  every  year.  Their  utilisation  was  initiated  in  1876  by  the  Bagosin  process 
for  preparing  the  best  lubricating  oils  (those  of  Baku  are  highly  valued)  by  distilling  the 
residues  by  means  of  superheated  steam,  so  as  to  avoid  the  formation  of  empyreumatic 
odours. 

The  distillation  is  now  carried  out  in  long  horizontal  boilers,  since  in  vertical  ones — 
which  were  used  at  one  time — the  vapours,  in  contact  with  the  heated  walls,  give  products 
of  profound  decomposition  and  of  bad  odour.  Direct-fire  heating  can  be  partly  used  in 
conjunction  with  internal  heating  by  superheated  steam  at  220°,  and  the  distillation  is 
facilitated  by  carrying  it  out  in  a  vacuum. 


FIG.  94. 

Fig.  94  shows  the  plant  used  by  Nobel  Brothers  at  Baku.  The  condensation  is  effected 
in  long,  parallel,  slightly  slanting  pipes,  d,  dv  dz  (40-50  cm.  in  diameter),  communicating 
alternately  at  the  ends*  The  first  of  these  is  cooled  by  air  alone,  the  second  by  water 
and  the  third  by  very  cold  water  that  circulates  in  a  coil  ;  H  is  an  exhaust-pump.  At 

established  in  1872  by  Thorpe  and  Young,  that,  when  the  vapours  of  heavy  petroleums  are  superheated,  they 
yield  gaseous  hydrocarbons  (6  to  8  per  cent.)  poorer  in  hydrogen  (ethylene  series)  and  lighter  liquids  which  can  bo 
used  as  second  quality  petroleum.  The  operation  is  carried  out 
in  a  vertical  boiler  (Fig.  93),  placed  in  a  furnace  so  that  its 
walls  are  strongly  heated  by  the  hot  fumes  circulating  round 
them.  The  boiler  is  not  completely  filled  with  masut,  so  that 
the  vapours  evolved,  coming  into  contact  with  the  red-hot  walls 
above  the  liquid,  are  decomposed ;  after  separation  in  a  de- 
phlegmator  of  the  heavy  oil  carried  over,  the  vapours  are  pro- 
gressively liquefied  in  ordinary  condensers  or  refrigerators, 
yielding  solar  oil,  benzine,  &c.,  whilst  the  remaining  gas  is  used 
for  heating  or  for  gas  engines.  A  mineral  oil  from  Ohio  treated 
by  this  process  gave  the  following  products  :  25  per  cent,  of 
benzine  (sp.  gr  0-650-0-745),  33. per  cent,  of  lighting  petroleum 
(sp.  gr.  0-800-0-840),  10  per  cent,  of  light  paraffin  oils  for  burn- 
ing (sp.  gr.  0-854-0-859),  31  per  cent,  of  solid  paraffin  and 
paraffin  oil  (sp.  gr.  0-870-0-925),  and  3  per  cent,  of  coke  and 
loss. 

Manufacture  of  Benzene  from  Naphtha.  Attempts  in 
this  direction  had  already  been  made  as  early  as  1875,  and 
later  llagosin  and  Nikiforow,  Krey,  Laing,  Dewar,  and 
Redwood  attacked  the  problem,  but  without  practical  success. 
Recently  Nikiforow  appears  to  have  succeeded  and  he  has 
devised  a  plant  for  treating  2400  tons  of  naphtha  and  pro- 
ducing 262  tons  of  benzene.  He  subjects  the  naphtha  to  two 
distillations  under  different  pressures,  in  a  retort  first  at  500° 
and  then  at  1000°.  In  this  way  33  per  cent,  of  tar  containing 

50  per  cent,  of  aromatic  compounds  is  obtained,  together  with  an  abundant  supply  of  gas  which  serves  for 
heating,  lighting,  and  power  purposes.  After  redistillation  and  rectification  of  the  first  of  these  products,  a  final 
yield  of  12  per  cent,  of  benzene  and  toluene  is  obtained,  3  per  cent,  of  naphthalene,  1  per  cent,  of  anthracene, 
and  various  secondary  products.  Benzene  thus  prepared  will  apparently  cosfc-20s.  per  quintal  and  the  aniline  oil 
(used  in  dyeing)  obtainable  from  it  would  cost  about  one-half  as  much  as  that  on  the  market  in  Russia.  J.  Hausmann 
(Ger.\Pat.  227,178,  1909)  also  obtains  benzene  and  its  derivatives  by  passing  the  vapours  of"  mineral  oil  into  red- 
hot  tubes,  and  into  contact  with  catalytic  agents  (oxides  of  iron,  lead,  and  cerium,  sulphate  of  iron,  &c.). 


FIG.  93. 


76 


ORGANIC    CHEMISTRY 


the  bottom  of  each  of  these  pipes  is  a  discharge  pipe  for  the  mineral  oil  condensates,  which 
pass  to  water-separators  ;  thus  three  qualities  of  oil  are  obtained  in  three  separate  tanks  : 
20-25  per  cent,  of  solar  oil,  specific  gravity  below  0-890  ;  6-10  per  cent,  of  spindle-oil 
of  sp.  gr.  0-890-0-900 ;  25-30  per  cent,  of  engine  oil,  sp.  gr.  0-900-0-920,  3-4  per  cent,  of 
cylinder  oil,  sp.  gr.  0-925 ;  3  per  cent,  of  tar  ;  and  5  per  cent,  of  loss.  The  quantity  of  steam 
consumed  varies  from  100  to  150  per  cent,  of  the  amount  of  oil  distilled  and  the  quantity 
of  masut  treated  every  24  hours  corresponds  with  about  double  the  volume  of  the  boilers. 

A  somewhat  different  apparatus  which  has  also  given  good  results  for  the  distillation 
of  tar  and  of  its  heavy  oils  is  that  made  by  the  firm  of  Hirzel  in  Leipzig.  The  large  boiler, 
BV,  with  a  convex  base  (Figs.  95  and  96)  is  divided  longitudinally  by  a  metal  partition,  1, 
which  allows  the  two  halves  of  the  boiler  free  to  communicate  at  the  end,  7  ;  the  distillation 
products  enter  at  the  tube  4,  connected  with  the  horizontal  pipe  5,  from  which  the  liquid 
descends  to  the  bottom  of  the  first  half  of  the  boiler  along  the  tubes  6  ;  the  superheated 

steam  enters  by  the  tube  3,  which 
is  forked  half-way  down  the  boiler 
and  connects  with  a  battery  of 
horizontal  perforated  pipes  running 
along  the  bottom  of  the  boiler.  The 
liquid  moves  slowly  in  a  compara- 
tively thin  layer  from  the  first  to 
the  second  half  of  the  boiler,  pass- 


Section  A.B. C.D. E  F. 


EB- 


Section  J- 1C. 


FIG.  95. 


FlG.    96. 


ing  through  the  space  7,  and  issuing  at  the  tube  8  ;  the  vapours  are  collected  in  the 
dome,  W,  containing  perforated  discs  to  condense  the  drops  carried  over  with  the  vapours, 
the  latter  proceeding  through  the  tube  a  to  the  rectification  or  fractional  distillation 
apparatus.  In  1911  the  Hirzel  apparatus  was  also  used  by  a  large  Italian  firm  of  metal- 
lurgical coke  manufacturers  and  tar  distillers. 

All  these  crude  mineral  lubricating  oils,  after  being  freed  from  moisture  by  heating, 
are  refined  by  prolonged  shaking  with  5-10  per  cent,  of  concentrated  sulphuric  acid  and, 
after  decantation  of  the  black  acid,  with  a  concentrated  caustic  soda  solution  (15°  Be.) 
at  60-65°,  this  being  followed  by  washing  with  hot  water.  In  these  refining  operations 
8-15  per  cent,  of  the  mineral  oil  is  lost.  The  residues  in  the  boilers,  if  they  are  not  solid 
coke,  bat  pasty,  are  dissolved  in  benzene  as  a  black  varnish  for  iron,  or  are  used  as  an 
adhesive  in  the  manufacture  of  briquettes  from  coal-dust,  or  as  a  combustible. 

According  to  Ger.  Pats.  161,924  and  161,925,  it  is  proposed  to  treat  crude  mineral 
oils  with  a  saturated  solution  of  sodium  chloride  and  carbonate,  to  blow  air  in  for  some 
time,  and  finally  to  distil  in  presence  of  an  oxide  of  manganese. 

To  render  mineral  oils  inodorous,  or  nearly  so,  they  are  treated  in  the  hot  with  formalde- 
hyde, and,  after  addition  of  alkali  or  acid  to  the  mass,  a  current  of  steam  is  passed  through 
(Ger.  Pat.  147,163).  According  to  Ger.  Pat.  153,585,  the  20  per  cent,  of  crude  mineral 
oil  is  distilled  with  superheated  steam  at  180°  in  presence  of  1  per  cent,  of  aqueous  lead 
acetate  solution.  The  distillate  is  free  from  sulphur  and  forms  a  lighting  or  gas-engine  oil  ; 
the  residue,  after  filtration,  forms  a  denser  and  almost  odourless  lubricating  oil.  In  some 
cases  petroleum  is  deodorised  by  agitating  with  calcium  chloride  and  a  small  quantity 


DECOLORISATION,    ETC.,    OF    OIL.S          77 

of  hydrochloric  acid,  decanting  it,  shaking  with  lime  to  fix  the  chlorine,  and  sometimes 
adding  a  little  amyl  acetate  or  essence  of  fennel  ;  treatment  with  soda  lye  is  also  resorted 
to,  and,  better  still,  both  for  mineral  oils  and  petroleums,  with  sodium  peroxide. 

Latterly,  mineral  oils  soluble  in  water  have  acquired  importance  for  lubricating 
machinery,  for  greasing  textile  fibres  to  be  combed,  and  for  watering  the  streets  to 
prevent  dust.  They  are  prepared  by  the  Boleg  process  (Ger.  Pats.  122,451,  129,480, 
148,168,  155,288) :  the  mineral  oil  is  heated  in  a  closed  vessel,  fitted  with  a  condenser, 
at  a  temperature  of  60-70°  or  above  by  means  of  indirect  steam  ;  at  the  same  time  finely 
divided  compressed  air,  after  addition  of  a  little  caustic  soda  solution,  is  injected  ;  a 
small  quantity  of  resin  soap  or  a  sulphoricinate  is  subsequently  introduced,  the  air- 
current  being  continued  meanwhile,  and  finally  the  whole  mass  is  heated  under  pressure 
in  an  autoclave. 

Emulsions  of  mineral  oils  with  water  are  obtained  by  addition  of  pyridine  or  quinoline 
bases  or  amino-acids. 

To  obtain  from  dark  mineral  oils  less  coloured  oils,  and  in  some  cases  oils  as  colourless 
as  water  (e.g.  vaseline  oils),  the  oil  is  passed  slowly  through  wide,  shallow  (a, bout  30  cm. 
deep)  filters,  filled  with  a  special  American  clay  (fuller's-earth  from  Florida)  consisting 
of  aluminium  and  magnesium  hydrosilicates,  previously  subjected  to  slight  roasting. 
The  slow  filtration  is  repeated  several  times  and  completed  in  filters  arranged  in  series. 
The  mineral  oil  remaining  in  the  filters  is  recovered  by  displacing  it  by  heavy  tar  oil  (very 
cheap)  and  displacing  the  latter  with  water.  Decolor isation  is  also  effected  with  bone- 
black  or,  best  of  all,  by  residues  from  the  manufacture  of  potassium  ferrocyanide,  which 
exhibit  very  great  decolorising  power  (50  per  cent,  more  than  American  clay)  ;  owing, 
however,  to  the  new  methods  of  manufacturing  ferrocyanide,  these  residues  are  becoming 
scarcer  and  more  expensive  (they  contain  30  per  cent,  of  animal  charcoal,  considerable 
quantities  of  silica  and  silicates  and  a  little  ferric  oxide).  The  darker  mineral  oils  are 
partly  decolorised  with  sulphuric  acid,  sometimes  together  with  dichromate. 

Carts  are  often  greased  with  the  so-called  consistent  fats  obtained  by  mixing  15-23  per 
cent,  of  calcium  soaps  and  mineral  oils  with  1-4  per  cent,  of  water  (if  there  is  no  water 
the  mass  remains  liquid,  and  if  there  is  not  a  little  free  fatty  acid  emulsification  ceases 
after  a  time  and  the  calcium  soap  separates). 

In  1909  Germany  imported  216,987  tons  of  mineral  oils.  Italy  in  1903  imported 
24,387  tons  of  mineral  oils  (exclusive  of  petroleum)  for  engines  and  steam  cylinders,  and 
in  1909  the  importation  (including  a  little  heavy  resin  and  tar  oils)  was  43,360  tons  of 
the  value  of  £450,000,  besides  8800  tons  of  residues  from  the  distillation  of  mineral  oils 
(masut),  worth  £14,000  (in  1907,  560  tons)  ;  in  1910,  49,181  tons  were  imported.  In  1910 
England  imported  mineral  lubricating  oils  to  the  value  of  £1,705,366  and  mineral  oils  for 
gas-engines  to  the  value  of  £262,455. 

REQUIREMENTS  IN  AND  ANALYSIS  OF  LUBRICATING  OILS.  Lubricating 
oils  serve  to  diminish  the  friction  between  metal  surfaces  in  motion  ;  by  adhering  strongly, 
although  in  very  thin  layers,  to  these  surfaces  they  prevent  contact  between  them  and 
hence  friction  and  heating  without  sensible  increase  of  the  resistance  owing  to  the  internal 
friction  of  the  oil.  Lubrication  is  due  partly  to  chemical  phenomena  (formation  of  metallic 
soap?)  and  partly  to  physical  phenomena  not  well  understood  ;  in  general,  where  there  is 
much  pressure  the  viscous  oils  are  suitable,  and  in  other  places  liquid  oils,  although  in  prac- 
tice mixtures  of  these  two  kinds  are  advantageously  employed.  Oil  for  lubricating  steam 
cylinders  at  high  temperatures  should  be  resistant  to  great  heat  and  to  the  mechanical 
and  chemical  action  of  steam,  and  should  not  give  inflammable  products  at  a  lower 
temperature  than  320°,  or  300°  where  superheated  steam  is  employed  ;  it  should  possess 
great  adhesive  power  and  viscosity  and  should  not  contain  resinous  or  tarry  residues. 
No  oil  resists  the  action  of  steam  at  above  350°.  The  good  qualities,  which  are  more  or 
less  dark,  are  transparent  in  the  liquid  state.  The  selection  for  steam  cylinders  of  oils 
viscous  at  ordinary  temperatures  is  unimportant,  as  they  become  as  liquid  as  water  when 
hot  ;  this  is  seen  from  a  comparison  of  the  following  two  mineral  oils,  the  numbers  giving 
the  viscosity  in  seconds  required  for  the  passage  of  200  c.c.  of  oil  through  the  Engler 
viscosimeter  (see  later). 

at  70°  at  100°          at  150'       at  170" 

Viscosity  of  sample  I  270  116  74  67 

II  835  226  93  73 


ORGANIC    CHEMISTRY 


The  Russian  engine  oils  are  more  viscous  than  the  American,  but  the  American  cylinder 
oils  are  more  viscous  than  the  Russian.  American  oils  with  sp.  gr.  0-908-0-920  and 
0-844-0-899  have  viscosities  almost  the  same  as  those  of  the  Russian  oils  with  sp.  gr. 
0-893-0-900  and  0-900-0-923  respectively. 

The  specific  gravities  of  certain  American  and  Russian  oils  are  as  follow : 


Axle  oil 
Pale  engine  oil 
Dark  engine  oil 
Cylinder  oil 


American 

0-908-0-911 
0-920 

0-884 
0-886-0-899 


Russian 
0-893-0-895 
0-903-0-905 
0-900-0-920 
0-911-0-923 


At  the  foot  of  the  page  is  given  a  summary  of  the  criteria  laid  down  by  Holde  for 
various  lubricating  oils  of  good  quality  and  the  requirements  to  be  answered  by  thofo 
supplied  to  the  Italian  railways.1 

Sometimes  mineral  oils  are  used  in  special  motors  for  utilising  their  high  calorific 
value  (10,500-11,700  cals.).  Sherman  and  Kropf  (1908)  found  that  the  calorific  value  of 


FIG.  97. 


FIG 


mineral  oils,  and  to  some  extent  of  petroleums,  is  inversely  proportional  to  their  specific 
gravity. 

The  origin  and  properties  of  certain  mineral  oils  is  sometimes  related  to  their  content 
of  paraffin,  the  determination  of  which  is  described  on  p.  86. 

i  (1)  Oil  for  spinning  spindles.  Clear  liquids,  viscosity  (see  later,  Engler  viscosimeter),  5  to  12  at  20°,  inflam- 
mability (in  the  Martens-Pensky  apparatus),  160°  to  200°.  (2)  Oil  for  ice-machines  or  compressors.  Very  fluid  ; 
viscosity,  5  to  7  at  20°  ;  freezing-point  below  —20°  ;  inflammability,  140°  to  180°.  (3)  Oil  for  light  engines  and 
transmission,  motors,  dynamos.  Medium  fluidity,  viscosity,  13  to  25  at  20° ;  inflammability,  160°  to  210°.  (4)  Oils 
for  heavy  engines  and  transmission.  Dense  ;  viscosity,  25  to  45  to  60  at  20°  ;  inflammability,  160°  to  210°.  (5)  Dark 
oils  for  locomotive  and  railway  carriages.  Viscosity,  45  to  60  (summer),  25  to  45  (winter) ;  inflammability  above 
140°  ;  freezing-point,  —  5°  (summer),  —15°  (winter).  (6)  Oil  for  steam  cylinders.  Very  dense  or  buttery  ;  vis- 
cosity, 23  to  45  at  50°  ;  inflammability,  220°  to  315°.  For  these  buttery  oils,  the  dropping --point  is  determined 
by  the  Ubbelohde  apparatus  (p.  6). 

The  authorities  of  the  Italian  railways  demand  Russian  oils,  since  these  freeze  only  below  - 10°,  whilst  the 
American  ones  solidify  at  0°  ;  they  must  not  contain  water,  that  is,  they  must  not  froth  if  heated  to  129°  ;  they 
must  give  no  deposit  even  after  standing  for  forty-eight  hours  ;  the  viscosity  must  be  at  least  eight  times  that 
of  water,  they  should  be  perfectly  neutral  and  should  not  contain  shale  i»il,  resin  oil,  or.  animal  or  vegetable  oil ; 
they  should  not  have  thf  slightest  "  drying  "  properties  in  the  air  (smeared  on  glass),  or  have  a  density  below 
0-91  or  a  flash-point  below  150°-180°  ;  they  must  not  contain  more  than  10  per  cent,  of  light  oils  distilling  below 
310°  ;  when  shaken  with  water,  the  oil  should  separate  immediately  without  the  water  remaining  whitish. 

With  mineral  oils  for  automobiles  it  is  important  to  test  for  resin  oils,  the  procedure  being  as  follows  :  5  grms. 
of  the  oil  are  heated  with  25  grms.  of  60  per  cent,  alcohol  to  40-50°  on  a  water-bath,  the  mixture  being  well  shaken 
until  it  emulsifies,  allowed  to  cool  and  filtered.  The  alcohol  is  driven  off  from  the  filtrate  on  a  water-bath 
and  the  cold  residue  treated,  drop  by  drop,  with  2  to  3  c.c.  of  dimethyl  sulphate  :  if  resin  oil  is  present,  a  red 
coloration  ii  produced. 


VISCOSITY,    FLASH-POINT,    ACIDITY      79 

For  lubricating  oils  it  is  important  to  determine  the  viscosity,  and  this  is  usually 
effected  by  means  of  the  Engler  viscosimeter  (Figs.  97  and  98),  formed  of  a  brass  vessel,  A 
(sometimes  gilt  inside),  provided  with  a  cover,  Alf  through  which  passes  the  thermometer,  t ; 
at  the  bottom  of  the  vessel  is  a  platinum  tube,  a,  20  mm.  long  and  of  such  dimensions 
that  it  allows  of  the  efflux  of  200  c.c.  of  distilled  water  at  20°  in  52-54  sees.  ;  the  aper- 
ture can  be  closed  from  above  by  the  hard  wooden  peg,  6.  The  vessel,  A,  is  contained  in 
larger  one,  B,  and  the  space  between  the  two  is  filled  with  water  maintained  constantly 
at  the  desired  temperature  by  means  of  the  ring-burner,  d,  and  the  thermometer,  Zx.  The 
dimensions  of  the  apparatus  are  exactly  denned  and  are  shown  in  millimetres  in  the  figure. 
The  mineral  oil  is  introduced  into  A  (clean  and  dry)  up  to  the  level  indicated  by  the  three 
points  (about  240  c.c.).  When  the  temperature  of  the  oil  in  A  has  the  desired  constant 
value,  the  flask  G  is  placed  under  the  efflux  tube  and  the  peg  rapidly  removed,  the 
exact  number  of  seconds  taken  to  fill  the  flask  to  the  200  c.c.  mark  being  determined 
by  a  chronometer.  The  time  required,  in  seconds,  divided  by  the  corresponding 
number  of  seconds  for  water  at  the  same  temperature  gives  directly  the  degree  of 
viscosity. 


FIG.  99. 


FIG.  100. 


The  flash-point  is  determined  by  the  Pensky-Martens  apparatus  (Figs.  99  and  100), 
which  is  analogous  to  the  Abel  apparatus  (p.  73)  but  without  the  water-bath,  being 
furnished  instead  with  a  stirrer  with  vanes,  6,  moved  by  twisting  the  metal  cord,  &',  between 
the  fingers  ;  it  works  similarly  to  the  Abel  apparatus,  and  the  small  flame,  E,  applied 
automatically,  is  fed  by  a  small  gas  tube,  H,  and  is  relighted,  every  time  it  is  extinguished, 
by  another  flame  by  its  side.  The  thermometer,  t,  is  graduated  from  80°  to  320°,  and  the 
heating  is  effected  by  the  triple  gas-burner,  g,  so  that  the  temperature  rises  5°  per  minute  ; 
observations  are  made  by  releasing  the  spring,  at  first  for  every  2°  and  later  for  every 
1°  rise  of  temperature. 

The  acidity  is  determined  by  titrating  50  c.c.  of  the  100  c.c.  of  50  per  cent,  alcohol 
(neutralised)  shaken  up  with  10  grms.  of  the  mineral  oil. 

It  is  sometimes  useful  to  know  if  certain  more  or  less  dark  mineral  oils  are  true  refined 
products  obtained  by  the  distillation  of  petroleum  residues  (masut,  &c.),  or  if  they  are 
merely  the  crude  residues  themselves  diluted  with  more  or  less  mineral  oil.  Charitschkoff 
(1907)  found  that  the  rise  of  temperature  on  mixing  with  concentrated  sulphuric  acid 
(Maumene  number)  in  a  Beckmann  apparatus  (see  Molecular  Weights,  vol.  i.)  is  2-2-3-50 
for  all  distilled  products  (solar  oil  and  various  lubricating  oils)  and  4-8-5°  for  all  non- 
distilled  products  (crude  naphtha,  masut,  &c.). 


80  ORGANIC    CHEMISTRY 

(.B)  VASELINE  (or  mineral  fat).  This  was  prepared  for  the  first  time  by 
Cheeseborough  in  1871  and  forms  a  white,  buttery  mass  constituted  almost 
exclusively  of  various  high,  saturated  hydrocarbons. 

It  is  prepared,  especially  in  America,  by  heating  certain  pale,  crude,  Penn- 
sylvanian  petroleums  by  direct  fire  in  open  boilers,  and  passing  into  the  mass 
a  current  of  hot  air  until  the  desired  consistency  or  specific  gravity  (0-86-0-87) 
is  reached.  The  mass  is  then  decolorised  by  passing  it,  while  still  hot,  re- 
peatedly through  animal  charcoal  or  other  decolorising  agents  (see  p.  77). 
It  is  also  prepared  from  the  residues  of  Galician  and  German  petroleum  by 
diluting  them  with  benzine  and  repeatedly  refining  with  concentrated  sulphuric 
acid.  It  melts  at  33^0°. 

Artificial  vaselines  are  also  placed  on  the  market,  these  being  obtained  by  dissolving 
paraffin  or  cerasin  (see  later)  in  paraffin  oil  ;  they  can  be  distinguished  from  the  natural 
vaselines,  the  latter  being  sticky  and  ropy  and  the  former  not.  At  60°  the  viscosity 
(Engler)  of  the  natural  vaselines  is  4-5-7-5,  and  that  of  the  artificial  ones  little  more  than  1  ; 
the  latter  contain  11-35  per  cent,  and  the  natural  vaselines  63-80  per  cent,  of  paraffin, 
insoluble  in  98  per  cent,  alcohol  at  0°.  The  natural  vaseline  after  solution  in  ether  and 
precipitation  with  alcohol  forms  a  sticky  mass  and  the  liquid  remains  turbid  ;  the  artificial 
variety,  on  the  other  hand,  is  precipitated  in  flocks  and  the  liquid  is  left  clear. 

Gelatinised  oil  of  vaseline,  also  prepared  nowadays,  is  transparent  and  does  not  deposit 
paraffin,  even  if  added  in  considerable  quantity  ;  it  is  obtained  by  heating  vaseline  oil 
(sometimes  with  a  little  sulphuric  acid)  at  about  200°  and  adding,  at  a  certain  moment,  a 
small  quantity  of  soap. 

For  the  decolorisation  of  vaseline  and  oil  of  vaseline  see  above. 

Vaseline  is  used  in  pharmacy  for  the  preparation  of  unguent  medicines, 
also  for  the  preparation  of  lubricants,  and,  in  large  quantities,  for  coating 
metallic  articles  to  preserve  them  from  rusting  and  oxidation  ;  it  is  also  used 
in  the  manufacture  of  smokeless  powder. 

(C)  PARAFFIN.  This  was  first  found  in  petroleum  by  Fuchs  in  1809 
and  Reichenbach  obtained  it  from  wood-tar  in  1830,  and  showed  its  great 
importance  as  an  illuminant. 

It  was  obtained  later  by  distilling  lignites  and  bituminous  schists.  To-day  it  is  largely 
prepared  also  from  the  denser  American  mineral  oils  (0-8588  and  upwards),  which  on 
cooling  deposit  scales  of  paraffin.  • 

For  this  purpose  an  apparatus  consisting  of  three  vertical  concentric  cylinders  is 
used  ;  in  the  inner  and  outer  ones  circulates  a  non -solidifying  freezing  solution,  which 
has  a  temperature  of  -20°  and  serves  to  separate  the  paraffin  from  the  mineral  oil  in  the 
middle  cylinder.  According  to  J.  Weiser  (Ger.  Pat.  226,136  and  227,334),  paraffin  is 
obtained  from  petroleum  and  tar  residues  by  dissolving  them  in  hot  benzine  and  glacial 
acetic  acid  ;  on  cooling,  the  solutions  deposit  paraffin,  cerasin,  or  ozokerite.  To  free  the 
flakes  of  paraffin  from  the  adhering  oil  the  cold  mass  is  pressed  in  filter -presses  (up  to 
15  atmos.)  and  the  cakes  thus  formed  are  finally  squeezed  in  hydraulic  presses,  as  is  done 
in  the  case  of  stearine  (see  this)  ;  the  blocks  of  paraffin  are  then  spread  out  in  a  warm 
chamber,  where  the  last  traces  of  coloured  oils  flow  away.  In  the  Weiser  process  the 
hydraulic  presses  are  replaced  advantageously  by  filtering  tubes  wound  round  with  linen  ; 
the  paraffin  from  the  filter-press  is  broken  up  and  forced  into  these  tubes,  being  afterwards 
removed  by  steam  and  sent  to  the  sweating  chamber. 

Hard  paraffin  melts  at  54-60°,  has  sp.  gr.  0-898-0-915,  and  forms  a  white, 
translucent  mass  used  for  the  manufacture  of  paraffin  candles  ;  it  is  soluble 
in  ether  or  benzene,  insoluble  in  alcohol,  acetic  acid,  and  acetone.  Soft  paraffin 
with  m.pt.  42-48°  and  sp.  gr.  0-88-0-89  is  used  as  an  adjunct  in  wax  and 
stearine  candles,  to  impregnate  wooden  matches,  in  dressing  textiles  and  as  a 
preventive  of  frothing  during  the  concentration  of  saccharine  juices  (see  Sugar) ; 
it  serves  also  as  an  insulator  of  electrical  conductors  and  as  a  cold  bath  in  the 
manufacture  of  hardened  gla^s. 


PYROPISSITE  81 

Most  of  the  paraffin  and  paraffin  oil  is  obtained  from  ozokerite  (see  later), 
the  tar  distilled  from  the  lignites  of  Saxony  and  Thuringia  (pyropissite)  and 
from  the  bituminous  shales  of  Scotland  and  Australia,  and  also  from  boghead 
coal. 

I.  PYROPISSITE  is  a  special  and  interesting  lignite  now  almost  exhausted,  is 
obtained  from  deposits  of  oily  wood,  and  is  extracted  from  the  mines  in  Saxony  and 
Thuringia  in  moist  (up  to  55  per  cent,  water)  more  or  less  plastic  masses  which  feel  greasy 
and  when  dry  become  friable  and  readily  burn  ;  it  has  a  dark  yellow  or  brown  colour. 
In  the  dry  state  it  gives  up  to  alcohol  20  per  cent,  of  its  weight  of  a  substance,  m.pt.  75-86°, 
giving  paraffin  oil  on  distillation.  The  composition  of  a  good  air-dried  pyropissite  was 
found  to  be  :  water,  33  per  cent.  ;  ash,  6-51  ;  C,  43-81  ;  H,  6-97  ;  N,  0-003  ;  O,  8-81. 
When  distilled  in  glass  retorts  in  the  laboratory  it  gives  about  66  per  cent,  of  tar,  26  per 
cent,  of  coke,  and  8  per  cent,  of  gas  ;  sometimes  as  much  as  73  per  cent,  of  tar  is  obtained. 
The  industrial  distillation  of  these  lignites  is  carried  out  in  large  vertical  refractory  retorts, 
8  metres  high  and  2  metres  wide,  placed  in  a  suitable  furnace  so  that  the  external  walls 
are  heated  by  rational  circulation  of  the  hot  gases.  Inside  the  retort  are  arranged 
numbers  of  iron  capsules,  inverted  one  on  the  other  with  a  certain  distance  between,  and 
a  diameter  12-20  cm.  less  than  that  of  the  retort.  The  lignite  is  charged  in  lumps  at  the 
top  and  descends  gradually  in  the  free  annular  space  between  the  walls  of  the  retort  and 
the  edges  of  the  capsule.  When  it  reaches  the  bottom  it  consists  of  nothing  but  coke, 
which  is  occasionally  discharged,  fresh  lignite  being  introduced  at  the  top  ;  the  gaseous 
products  are  evolved  by  a  large  tube  at  the  top,  and  the  tarry  products  (tar)  flow  down 
the  walls  of  the  capsules  and  are  collected  by  a  lower  tube.  The  retorts  are  maintained 
at  a  dull  red  heat. 

Lignite  tar  is  brownish  yellow  to  black  in  colour,  has  a  peculiar  odour,  and  liquefies 
between  15°  and  30°,  giving  a  greenish  fluorescence.  Its  specific  gravity  is  0-820-0-935, 
or  usually  0-840  at  35°.  It  has  an  alkaline  reaction  (from  ammonia,  ethylamine,  &c.)  and 
contains  about  20-25  per  cent,  of  paraffin.  The  best  lignites  give  the  less  dense  tars. 
According  to  the  nature  of  the  tar,  the  paraffin  x  is  obtained  from  it  in  the  following  ways 
(see  also  Part  III,  Distillation  of  Tar) : 

(1)  With  very  dense  tars,  in  order  to  separate  the  creosote  and  certain  resinous  sub- 
stances more  efficiently,  vacuum  distillation  in  large  direct-fired  boilers  is  resorted  to. 
This  yields  25-50  per  cent,  of  fatty  oils,  50-65  per  cent,  of  crude  paraffin,  and  7-9  per 
cent,  of  coke,  which  is  burnt,  together  with  the  gases  from  the  distillation,  to  heat  the 
boilers.  The  mass  of  crude  paraffin  is  purified  with  acid  and  alkali,  or  with  acid  and 
subsequent  distillation.  The  more  solid  part  is  then  separated  from  the  oily  part  by  cooling 
the  mass  in  vessels  holding  100-200  kilos,  around  which  circulates  a  very  cold  solution 
(the  non -solidifying  liquids  used  for  ice-machines,  see  vol.  i,  p.  231).  When  the  oily  or 
buttery  part  (which  is  distilled  for  the  extraction  of  solar  oil  and  second-grade  paraffin) 
is  separated  by  filtration  from  the  crystallised  paraffin,  the  cakes  of  the  latter  are  pressed 
in  hydraulic  presses  at  150  atmos.  to  remove  the  20  per  cent,  of  oil  still  con  tamed  in  them. 
The  solid  cakes  which  remain  are  yellowish  in  colour,  and  are  purified  by  melting  them 
several  times  with  10-15  per  cent,  of  benzine  and  pressing  them  at  200  atmos.  in  a  hydraulic 
press.  To  get  rid  of  the  smell  of  benzine  the  paraffin  is  heated  in  iron  cylinders  with 
high-pressure  steam,  the  hot  paraffin  being  then  passed  through  the  decolorising  material 
(animal  charcoal,  ferrocyanide  residues,  or  magnesium  hydrosilicate  clay  (see  p.  77)). 
The  small  quantity  of  this  material  retained  by  the  paraffin  is  finally  removed  by 

1  Sow  that  the  deposits  of  pyropissite  are  almost  exhausted  and  the  paraffin  industry  of  Saxony  and  Thuringia 
has  been  subjected  to  the  competition,  first,  of  ozokerite  (after  1870),  and  then  (after  1880)  to  the  more  serious 
one  of  the  American  paraffin  extracted  from  Ohio  petroleums — which  has  invaded  all  the  markets  of  the  world — 
it  has  been  recently  discovered  that  when  pyropissite  is  distilled  a  great  part  of  the  paraffin  is  destroyed,  much 
better  yields  being  obtained  by  extracting  direct  with  suitable  solvents,  which,  after  evaporation,  leave  a  waxy 
mass ;  when  this  is  purified  with  fuming  sulphuric  acid,  it  yields  an  almost  white  product  of  great  value— the 
montan  wax  (Bergwachs),  similar  to  cerasin  (mineral  wax).  The  remedy  for  the  paraffin  crisis  of  Saxony  and 
Thuringia  has  arrived  too  late,  since  the  valuable  paraffin  has  been  squandered  by  distillation.  Other  layers  of 
lignite  are  being  worked  to-day,  and  these  are  extracted  in  the  hot  with  benzine  ;  the  solution  of  bitumen  extracted 
is  first  purified  by  thorough  cooling,  the  paraffins  being  thus  separated  while  the  resins  (these  are  recovered 
by  evaporation  of  the  solvent ;  they  melt  at  50°  to  60°  and  form  15  to  25  per  cent,  of  the  crude  bitumen)  remain 
in  solution.  The  bitumen  separated  in  the  cold  is  redissolved  in  benzine  and  treated  with  concentrated  sulphuric 
acid,  the  mass  being  kept  mixed  and  slowly  heated  to  boiling.  Animal  charcoal  is  added  and  the  liquid  filtered, 
passed  over  fuller's-earth  (see  p.  77),  and  neutralised  by  passing  in  a  little  gaseous  ammonia.  After  distillation  of 
the  solvent  there  remains  a  yellowish  or  almost  white  paraffin  melting  at  82*  to  85°  (Ger.  Pat.  216,281,  1907) 
II  6 


82 


ORGANIC    CHEMISTRY 


filtration  through  paper,  the  paraffin  being  then  allowed  to  solidify  in  large  shallow 
moulds. 

Miss  Az  has  recently  suggested  the  purification  of  crude  paraffin  by  treating  it  either 
fused  or  as  powder,  between  60°  and  70°,  with  a  solvent  (methyl  or  ethyl  alcohol,  acetone, 
or  acetic  acid  or  anhydride).  The  paraffin  is  insoluble  and  the  impurities  soluble  in  these 
solvents.  Paraffin  thus  purified  appears  to  be  of  better  quality  than  that  purified  in  the 
ordinary  way. 

The  tar  is  sometimes  distilled  with  superheated  steam  ;  in  other  cases  only  the  benzines 
(photogens)  and  the  light  oils  are  distilled,  the  residue  being  cooled  to  a  low  temperature 
and  the  solid  paraffin  which  separates  centrifugated  to  eliminate  the  tar  and  heavy  oils. 
When  the  tars  are  very  dense  (above  0-900)  Krey  finds  it  convenient  to  distil  them  under 
a  pressure  of  about  10  atmos.,  thus  raising  the  temperature  to  400-450°.  This  yields 
60  per  cent,  of  distilled  oil  of  sp.  gr.  0-830,  which  is  largely  used  for  the  preparation  of 
oil-gas  (see  p.  57),  10  per  cent,  of  gas,  and  30  per  cent,  of  residual  oily  tar. 

(2)  With  light  and  very  pure  tars  a  greater  yield  of  paraffin  is  obtained  more  cheaply 
by  treating  the  tar  directly  with  concentrated  sulphuric  acid,  washing  with  water,  and 
subjecting  to  fractional  distillation  over  calcium  hydroxide.  Crystallisation,  pressing,  and 
bleaching  are  carried  out  as  described  above. 

The  following  scheme  shows  the  different  operations  and  the  final  yields  in  a  tar 
distillation  (the  brackets  unite  products  which  are  worked  up  together,  generally  by 
distillation  ;  the  ultimate  products  are  shown  in  italics) : 

Tar 

(sp.  gr.  0-830-0' 


Crude  oil 


Crude  solar  oil     Red  oil    Pasty  mass  I 


Crude  paraffin 


Expressed  oil     10  %  paraffin  I 


(m.pt.  54-60° 

Crude  solar  oil     Red  oil     Pasty  r 

12  %  (sp.  gr.  0-860-0-880) 

2  %  photogens 

(sp.  gr. 
0-800-0-810) 


10  %  solar  oil 

(sp.  gr. 
0-825-0-830) 


10  %  yellow  oil     solar  oil 

(sp.  gr.  residues 

0-850-0-860) 


3  %  fatty  oil 

(sp.  gr. 
0-880-0-890) 


1  %  pasty  distillate 
(m.pt.  30-38°) 


i 
20  %  dark  paraffin  oil 

(sp.  gr. 
0-890-0-920) 


I 

4  %  soft  paraffin 
(m.pt.  42-48°) 


Photogen  is  a  species  of  benzine  similar  to  that  of  petroleum,  but  obtained  by  the 
distillation  of  wood,  lignite,  and  coal  ;  it  is  used  in  the  purification  of  paraffin,  in  the 
carburetting  of  lighting  gas,  and  for  removing  spots  from  fabrics.  Yellow  oil  is  used  for 
the  extraction  of  fats  and  for  cleaning  ;  red  oil  (sp.  gr.  0-860-0-880)  has  various  uses,  and 
serves  well  for  the  manufacture  of  oil-gas  (see  p.  57)  ;  the  fatty  oils  and  dark  paraffin 
oils  (0-880-0-925)  are  used  as  oil  for  gas  and  for  making  cart-grease  1 ;  the  yellow  and  red 
oils  (0-880-0-900)  are  used  as  thinner  lubricants. 

1  Oils  for  Gas.  From  the  time  when  gasworks  began  to  mix  gas  obtained  by  the  carbonisation  of  bitu- 
minous coal  with  carburetted  water-gas  and  with  oil-gas  (in  1905  Germany  produced  30,000,000  cu.  metres,  England 


ASPHALT  E,    PITCH,    BITUMEN  83 

The  washing  of  tar  and  of  its  distillates  with  alkali  removes  the  creosote  which  is 
liberated  by  sulphuric  or  carbonic  acid  (see  Part  III).  Washing  with  acid  separates 
resinous  masses  which  are  set  free  by  diluting  the  acid  mass  with  water,  this  removing  the 
acid.  Distillation  of  these  resinous  masses  with  varying  proportions  of  creosote  oil  and 
at  different  temperatures  yields  goudron  or  asphalte  tar,  or  artificial  bitumen?-  which  is 
used  in  the  manufacture  of  impermeable  pasteboard  for  roofing,  in  rendering  woodwork 
and  masonry  (especially  in  damp  houses)  damp-proof,  and  also  in  the  manufacture  of 
ultramarine. 

II.  Another  important  source  of  paraffin  is  furnished  by  the  Bituminous  Schists, 
which  are  especially  abundant  in  the  Lothians  in  Scotland.  In  1848  Young  and 
Meldrum  began  to  work  and  purify  a  special  oil  issuing  from  the  surface  of  the  soil  in 

500,000,000  cu.  metres,  and  the  United  States  1,550,000,000  cu.  metres  of  carburetted  water-gas),  the  use  of  mineral 
oils  for  carburetting  the  water-gas  and  tor  producing  oil-gas  has  increased  considerably.  These  oils  for  gasifying 
are  obtained  partly  by  the  distillation  of  lignite  and  shale  tars  (see  pp.  116,  119),  but  more  especially  by  the 
•distillation  of  petroleum  residues  (solar  oil,  intermediate  to  true  petroleum  and  lubricating  oils).  The  price  of 
these  oils  increases  with  the  narrowness  of  the  temperature  limits  within  which  they  boil ;  these  limits  are  usually 
100°  apart  and  it  is  of  no  consequence  whether  they  be  200"  and  300°  or  250°  and  350°  ;  they  should  contain  less 
than  25  per  cent,  of  unsaturated  hydrocarbons  (soluble  ill  concentrated  sulphuric  acid  of  sp.  gr.  1-83),  otherwise 
they  give  too  much  tar  and  coke  on  gasification  ;  they  should  contain  not  more  than  30  per  cent,  of  creosote,  but 
a  high  proportion  of  paraffin  is  advantageous.  In  the  United  States  600,000  tons  are  consumed  annually  ;  about 
220,000  tons  (in  1906)  are  imported  into  England,  and  about  4153  tons  of  mineral  oils  (sp.  gr.  0-83-0-83)  into 
Germany  for  the  carburetting  of  water-gas ;  but  Germany  itself  produces  a  further  quantity  of  about  300,000 
tons  of  oil  for  gasifying,  13,000  tons  being  used  for  producing  oil-gas  on  the  railways,  and  9000  tons  for  mineral- 
oil  engines.  For  the  carburetting  of  gas  these  oils  should  cost  less  than  9s.  6rf.  per  quintal. 

»  Asphlate,  Pitch,  and  Bitumen.  When  tar  from  the  distillation  of  wood  (or  lignite)  is  heated  until  all 
the  volatile  products  are  eliminated,  there  remains  a  black  mass  which,  when  cold,  assumes  a  glassy  consistency 
and  forms  pitch,  used  particularly  for  caulking  ships,  for  preparing  shoemakers'  thread,  and  for  making  cements 
impermeable  to  water,  &c. 

When  coal-tar  is  completely  distilled  it  leaves  a  more  or  less  hard  black  residue — coal-pitch — which  is  used 
for  ordinary  asphalting  and  for  making  varnishes,  lacs,  and  coal  briquettes  (see  vol.  i,  p.  369).  Pitch  is  also 
prepared  expressly  by  prolonged  heating  of  tar  in  a  current  of  air  or  with  sulphuric  acid. 

Bitumen  (mineral  pitch)  bears  sometimes  the  unsuitable  name,  natural  asphalte,  and  forms  a  fragile,  blackish 
brown  mass,  which,  on  heating,  softens  between  100°  and  135°  ;  it  has  the  sp.  gr.  1-10-1-20  and  the  hardness  2. 
It  burns  readily  with  a  very  smoky  flame,  is  insoluble  in  water,  alkali  or  acid,  slightly  soluble  in  alcohol  or  ether 
and  readily  soluble  in  benzene,  carbon  disulphide  and  turpentine  (in  which  it  ceases  to  be  soluble  after  exposure 
to  light,  and  is  hence  used  in  photo-lithography).  The  best  bitumen  is  found  at  the  surface  of  the  Dead  Sea  in 
Palestine,  and  in  greater  quantities  at  the  Pitch  Lake  in  the  island  of  Trinidad ;  it  abounds  also  in  Syria,  Utah, 
Venezuela,  and  Cuba,  and  at  Dax  (France).  That  of  Trinidad  is  the  best  and  contains  40  to  50  per  cent,  of  pure 
bitumen  and  30  per  cent  of  mineral  substances,  the  remainder  consisting  of  organic  substances  and  water.  It 
is  roughly  refined  on  the  spot  by  melting  at  160-170°  in  open  vessels  to  separate  part  of  the  mineral  substances, 
the  product  thus  obtained  containing  56  to  58  per  cent,  of  pure  bitumen,  having  the  sp.  gr.  1-40-1-43  and  softening 
at  85J-95°  ;  the  portion  soluble  in  petroleum  ether  bears  the  name  petrolene.  The  amount  of  change,  or  efflor- 
escence, which  bitumen  will  undergo  under  the  action  of  air  and  light  can  be  estimated  by  determining  the 
proportions  of  carbenes  present,  i.e.  the  products  insoluble  in  carbon  tetrachloride  but  soluble  in  carbon  disulphide. 
Pure  bitumen  is  used  for  making  black  sealing-wax,  black  lacs  and  varnishes,  and  also  lamp-black  ;  the  lower 
qualities  serve  for  coating  wooden  structures  (boats,  telegraph  poles),  for  cardboard,  for  roofs,  and  damp 
walls,  &c. 

In  order  to  distinguish  natural  from  artificial  bitumen,  about  1  grm.  of  the  substance  is  heated  to  200°,  cooled, 
powdered,  and  treated  with  5  c.c.  of  80  per  cent,  alcohol ;  if  the  latter  turns  yellow  and  exhibits  fluorescence, 
artificial  bitumen  is  indicated,  whilst  if  the  alcohol  remains  almost  colourless,  the  bitumen  is  natural. 

By  the  term  asphalte  (natural)  is  meant  minerals,  rocks,  and  earth  containing  bitumen  :  gravelly  stones  impreg- 
nated with  bitumen,  as  has  been  mentioned  above,  are  treated  for  the  extraction  of  refined  bitumen  by  heating 
with  water,  whilst  calcareous  bituminous  stones  containing  5  to  14  per  cent,  (sometimes  20  per  cent.)  of  pure 
bitumen,  are  used  for  the  preparation  of  asphalte  mastic  by  powdering  and  fusing  them  homogeneously  with 
a  certain  -quantity  of  bitumen.  This  mastic  is  cooled  in  moulds  and  is  used  directly  for  paving  streets  and 
terraces,  either  alone  or  mixed  with  fine  sand  or  gravel.  Powdered  asphalte  can  also  be  used  for  paving,  by 
spreading  it  out  and  compressing  it  with  heavy  cast-iron  double  rollers  heated  inside. 

In  California,  large  quantities  of  artificial  asphalte  are  prepared  by  prolonged  injection  of  air  into  dark  mineral 
oils  (sp.  gr.  0-9333  to  0-9859)  heated  at  650°.  Fusion  of  colophony  at  250°  and  addition  of  sulphur  yields  an 
asphalte  which  is  similar  to  that  of  Syria  and  is  used  in  photography. 

Natural  asphalte  occurs  abundantly  near  Neuehitel,  in  the  Department  of  Ain  (France),  in  the  neighbourhood 
of  Hanover,  and  at  Lettomonapello  in  Italy  (the  product  of  this  locality  is  worked  at  S.  Valentino,  near  Chicti). 

Statistics  and  Prices.  Pitch :  Italy  produced  4820  tons  of  the  value  £9600  in  1909 ;  England  ex- 
ported 30,000  tons  in  1909  and  36,000  tons  in  1910,  and  imported  8000  tons  in  1909  and  12,200  tons  in  1910 ; 
Germany  imported  39,251  and  exported  22,387  tons  in  1908,  and  imported  28,434  and  exported  34,816  tons  in 
1909. 

Asphalte:  In  1909  Italy  produced  111,067  tons  of  asphaltic  rock,  26,588  tons  of  pulverised  asphaltjc  rock, 
8250  tons  of  artificial  asphalte  (obtained  by  mixing  the  coke  remaining  from  the  distillation  of  tar  with  sand 
&c.)  and  731  tons  of  compressed  asphalte  bricks.  This  production  takes  place  mainly  in  Central  Italy  and  in 
Sicily  (at  Kagusa  di  Siracusa  and  Modica ;  the  asphalte  rocks  of  the  latter  locality,  according  to  A.  Coppadoro 
(1910)  contain  7  to  14  per  cent,  of  bitumen  and  82  to  89  per  cent,  of  calcium  carbonate).  In  1909  Italy  exported 
a  total  of  21,978  tons  (of  the  value  £132,000)  of  these  substances  under  the  name  solid  bitumen  (27,175  tons  in 
1906  ;  26,036  tons  in  1907  ;  24,158  tons  in  1908).  In  1908  Germany  imported  130,062  tons  (98,370  tons  in  1909) 
and  exported  13,280  tons  (14,200  in  1909) ;  it  produced  103,000  tons  in  1905  ;  89,000  tons  in  1908  (value  £40,000), 
and  77,500  tons  in  1909.  Trinidad  exported  asphalte  to  tho  value  of  £115,800  in  1905  and  £133,200  in  1906. 

The  price  of  tar  is  6*.  7d  per  quintal :  Archangel  pitch  I,  22*  5d. ;  Swedish  pitch,  18s.  5rf. ;  coal  pitch,  4*. 
to  4s.  lOd. ;  lignite  pitch,  4«,  Wd.  to  6*.  5rf. ;  steannc  pitch,  14s.  5rf.  to  28s.  lOrf  ;  Syrian  asphalte  I,  68s. ;  asphnllo 
in  fine  powder,  140s. 


84  ORGANIC    CHEMISTRY 

Derbyshire,  and,  having  exhausted  this  deposit  and  not  finding  others,  they  succeeded  in 
preparing  mineral  oils,  which  had  been  already  introduced  for  illuminating  purposes,  by 
distilling  cannel  coal,  which  gave  much  lower  but  remunerative  yields. 

In  about  1860  they  discovered  that  the  interesting  Scotch  deposits  of  boghead  coal 
gave  a  yield  of  oil  much  greater  than  cannel  coal,  and  in  1864  and  1866  were  erected  the 
two  works  at  Bathgater  and  Addiwell,  which  became  world  famous.  The  deposits  of 
boghead  coal  were  exhausted  in  four  or  five  years,  and  were  then  replaced  by  the  more 
abundant  although  less  fertile  deposits  of  bituminous  schists  (shales)  in  which  Scotland  is 
so  rich.  The  invasion  of  American  petroleum  in  about  1880  created  a  serious  crisis  in 
this  industry,  which  was  partially  saved  by  new  and  improved  technical  methods  intro- 
duced by  engineers  and  chemists,  especially  by  Henderson  ;  the  by-products  were  more 
completely  utilised,  the  furnaces  improved,  fractional  distillation  apparatus  brought  into 
use,  the  ammoniacal  liquors  utilised,  the  tar,  coke,  gas,  and  final  residues  employed  as  fuel 
and  the  labour  reduced  to  a  minimum  ;  the  mineral  oils  came  to  occupy  a  secondary 
position,  attention  being  paid  to  the  production  of  paraffin  and  high-class  lubricating 
oils  for  engines. 

In  France  these  bituminous  schists,  which  abound  in  the  basin  of  the  Autun  and  at 
Buxiere-les-Mines,  were  first  worked  in  1837  by  Selligne  in  consequence  of  the  studies 
of  Reichenbach  (1830),  and  the  industry  became  a  flourishing  one  about  1860  ;  in  1864, 
128,550  tons  of  shale  were  distilled,  producing  4750  tons  of  crude  oil,  destined  principally 
to  prepare  oil-gas  in  the  large  towns.  The  invasion  of  American  petroleums  also  over- 
threw this  industry,  which  is  now  only  partially  supported  by  the  Customs  duty. 

A  bituminous  schist  from  Midlothian  (Scotland)  gave  on  analysis :  20  per  cent, 
carbon,  0-7  per  cent,  nitrogen,  1-5  per  cent,  sulphur,  the  rest  being  mineral  matter  ;  it 
gave  up  nothing  soluble  to  ether. 

The  industrial  distillation  is  carried  out  in  batteries  of  vertical  retorts  arranged  in  a 
furnace  and  heated  also  internally  with  superheated  steam.  The  products  of  distillation 
are  condensed  with  apparatus  similar  to  that  used  for  illuminating  gas,  the  residues  from 
the  retorts,  containing  as  much  as  12  per  cent,  of  combustible  substances,  being  burnt 
in  the  furnaces.  The  distillation  lasts  from  4  to  6  hours,  or,  for  large  retorts  holding  2  tons, 
24  hours.  The  yield  consists  of  about  4  per  cent,  of  gas,  8  per  cent,  of  ammoniacal  liquor 
(ammonium  carbonate),  12  per  cent,  of  crude  oil,  76  per  cent,  of  residue.  The  crude  oil 
contains  less  than  0-03  per  cent,  of  sulphur  ;  the  gas  evolved  contains  21-23  per  cent. 
CO2  ;  1-4  per  cent.  CO  ;  13-24  per  cent.  H  ;  1-6  per  cent,  of  heavy  hydrocarbons  ;  8-20 
per  cent.  CH4  ;  1-2-4  per  cent.  O  ;  and  35-43  per  cent.  N. 

The  crude  oil  is  dark  green  and  has  a  sp.  gr.  0-865-0-885,  and  is  semi-solid  at  ordinary 
temperatures  owing  to  the  paraffin  present. 

This  oil  is  treated  by  virtually  the  same  methods  as  are  used  for  lignite  tar,  that  is, 
by  continuous  distillation  in  a  current  of  steam,  so  as  to  obtain  purer  products.  The 
first  distillation  gives ':  green  naphtha  (0-753)  and  green  oil  (0-858),  which  are  purified  by 
acid  and  alkali  and  then  redistilled :  the  first  gives  commercial  mineral  oil  (also  solar 
oil)  and  the  second  light  oils  and  paraffin,  which  is  separated  by  cooling  from  the  blue  oil, 
which  serves  as  a  good  lubricant  when  refined.  The  paraffin  is  purified  by  the  process 
given  above  (paraffin  of  lignite  tar). 

A  ton  of  bituminous  schist  (of  the  value  of  12s.  9%d.)  yields  about  8  kilos  of  naphtha, 
115  kilos  of  crude  oil  (green  oil),  and  13  kilos  of  ammonium  sulphate.  From  100  kilos 
of  green  oil  are  then  obtained  31  kilos  of  burning  oil,  13  kilos  of  lighting  oil,  11  kilos  of 
midlle  oil,  15  kilos  of  paraffin,  and  15-20  per  cent,  of  loss,  the  remainder  being  coke 
or  tar. 1 

1  Ichthyol  is  an  oil  obtained  by  the  dry  distillation  of  a  bituminous  shale  occurring  abundantly  in  the 
Tyrol  (at  Seefeld),  and  at  Besano  (Varese),  and  Melide  (Switzerland).  On  distillation  it  yields,  besides  illuminating 
gas,  5  to  T  per  cent,  of  crude,  utilisable  ichthyol  (for  the  Melide  shales)  containing  5  per  cent.  (Besano)  or  10  per 
cent.  (Seefeld)  of  combined  sulphur  and  6  to  7  per  cent,  of  nitrogen.  On  distillation,  these  shales  lose  30  to  40  per 
cent,  of  their  weight.  The  Besano  oil  is  richer  in  pyridine  bases  than  that  of  Seefeld,  Which  contains  1  per  cent,  of 
them  (Baumann  and  Schotten,  Contardi,  and  Malerba). 

Treatment  of  this  oil  with  concentrated  sulphuric  acid  yields  ichthyolsulphonic  acid  containing  10  to  15  per 
cent.  S  (like  sulphoricinates)  and  forming  salts  (ichthyolsulphonates)  with  soda  or  better  with  ammonia,  which  are 
used  in  the  cure  of  skin  diseases.  Ammonium  ichthyolsulphonate  (C22H3eOeS3(NH.,)2  ?),  which  commonly 
bears  the  name  of  ichthyol,  forms  a  dense,  reddish  brown  liquid,  soluble  in  water,  and  its  solution  gives  a  black 
resinous  deposit  with  HC1  and  yields  NH3  when  treated  with  KOH. 

When  distilled  with  steam  (or  treated  with  hydrogen  peroxide)  ichthyol  loses  its  unpleasant  odour,  the  deodorized 
product  being  termed  dvsifhthyol.  Of  the  many  other  derivatives  (and  substitutes,  e.g.  thyol,  obtained  by 
treating  tar  oils  with  sulphur),  mention  may  be  made  of  ichthyoform  (blackish  brown,  inodorous),  prepared  by 


OZOKERITE  85 

The  oily  schists  of  Australia  (77  miles  from  Sydney)  give,  on  distillation  :  68  per  cent, 
of  oils,  14  per  cent,  of  gas,  11  per  cent,  of  crude  paraffin  wax,  and  7  per  cent,  of  ash. 

In  1873,  524  tons  of  oily  shales  were  treated  in  Scotland  ;  in  1893  about  2,000,000 
tons,  and  in  1909  3,000,000  tons,  giving  280,000  tons  of  crude  oil.  The  Scotch  shale-oil 
refineries  produced  in  1908  90,000  tons  of  burning  oil,  16,000  tons  of  engine  oil,  40,000 
tons  of  gas-oil,  40,000  tons  of  lubricating  oil,  25,000  tons  of  paraffin  wax,  and  60,000  tons 
of  ammonium  sulphate.  In  1908  134,163  tons  of  bituminous  shale  of  the  value  £72,400 
were  produced  in  Italy.  In  France  219,000  cu.  metres  were  distilled  in  1890. 

In  Germany  80,000  tons  of  lignite  tar  (corresponding  with  600,000  tons  of  lignite) 
are  distilled  annually,  and  the  products  obtained  (9000  tons  of  paraffin  wax — two -thirds 
hard  and  one-third  soft — 5000  tons  of  solar  oil,  and  3500  tons  of  heavy  oil)  have  a  value 
of  about  £880,000. 

Tar  can  be  purchased  from  the  lignite  distilleries  at  little  more  than  Wd.  per  quintal, 
and,  treated  as  above,  yields  14s.  5d.  to  16s.,  taking  as  the  average  selling  prices  per  quintal : 
paraffin  wax,  £3  12s.  ;  solar  oil,  10s.  5d.  ;  yellow  oil  of  paraffin,  12s.  Wd.  ;  dark  oil  of 
paraffin,  10s.  5d.,  which  are  about  25  per  cent,  less  than  the  market  prices. 

III.  The  third  source,  one  of  the  most  important,  of  paraffin  wax  is  Ozokerite 
(or  mineral  wax).  It  is  found  in  England,  Russia,  and  America,  but  the 
deposits  of  greatest  industrial  and  historical  importance  are  those  of  Galicia 
(Boryslaw,  Pomiarki,  Starunia,  &c.),  where  it  occurs  in  seams  as  much  as 
a  metre  in  thickness.  It  was  discovered  by  Doms  when  searching  for  petro- 
leum, and  from  1860  to  1870  was  worked  by  the  Landesberg  process  for  the 
extraction  of  paraffin  wax,  which  competed  keenly  with  that  of  Saxony  and 
Thuringia  (from  lignite)  ;  in  1870,  Pilt  and  Ujhelyi  found  that  simple  treat- 
ment of  ozokerite  with  concentrated  sulphuric  acid,  followed  by  decolorisation 
with  animal  black,  yields  cerasin,  a  product  of  greater  value  than,  and  similar 
to,  beeswax.1  In  the  State  of  Utah,  the  industrial  treatment  of  ozokerite 
was  begun  in  1888,  and  in  1890  already  yielded  as  much  as  600  tons  of  crude 
cerasin. 

Ozokerite  forms  an  amorphous  mass  of  a  yellow,  brown,  greenish,  or  black 
colour  and  of  varying  consistency  ;  the  harder  varieties  show  a  fibrous  fracture  ; 
the  specific  gravity  is  0-85-0-95,  and  the  m.pt.  55-110°  (usually  between 
60°  and  79°)  ;  it  contains  85  to  86  per  cent,  of  carbon  and  14  to  15  per  cent, 
of  hydrogen,  and  hence  consists  principally  of  paraffins,  together  with  a 
small  proportion  of  defines  ;  it  is  soluble  in  benzine,  turpentine,  petroleum, 
ether,  and  carbon  disulphide,  but  only  slightly  so  in  alcohol.  It  forms  an 
excellent  electrical  insulator  and  can  be  used  in  place  of  gutta-percha. 

According  to  Hofer,  ozokerite  has  been  formed  by  the  slow  evaporation, 
during  many  centuries,  of  petroleum  rich  in  paraffin. 

On  distillation,  it  yields  :  2  to  8  per  cent,  of  benzine,  15  to  20  per  cent, 
of  naphtha,  36  to  50  per  cent,  of  paraffin  wax,  15  to  20  per  cent,  of  heavy 
oils,  and  10  to  20  per  cent,  of  residual  solids. 

STATISTICS  AND  PRICE  OF  PARAFFIN  WAX.  In  1908  fourteen  factories  in 
Germany  treated  70,000  tons  of  lignite  tar,  worth  about  £160,000,  and  produced  45,000 

treating  ichthyolsulphonic  acid  with  formaldehyde  and  used  as  an  antiseptic  for  the  intestines  and  instead  of 
iodoform  for  curing  wounds  .  it  costs  £4  per  kilo  and  ammonium  ichthyolsulphonate  £1  per  kilo. 

1  The  material  from  the  mines  (shafts  80  metres  or  more  in  depth),  which  contains  admixed  earth  and  stones, 
is  placed  in  open  vessels  holding  300  litres  and  heated  by  direct  fire  heat ;  the  mineral  matter  settles  to  the  bottom 
and  is  separated  by  decantation.  This  matter  still  contains  10  per  cent,  of  wax,  which  is  extracted  with  benzine  ; 
both  this  and  the  decanted  part  form  the  prime  materials  treated  in  the  refineries  found  in  all  countries. 

The  refining  is  carried  out  in  large  iron  boilers  holding  up  to  3000  kilos  of  the  crude  wax,  half  a  metre  being 
left  free  to  take  the  scum  which  forms.  The  fused  mass  is  kept  at  115-120°  for  four  to  five  hours  and  is  stirred 
to  liberate  all  the  water ;  15  to  25  per  cent,  (according  to  the  quality  of  the  wax)  of  fuming  sulphuric  acid  con- 
taining 78  per  cent,  of  SO,  is  then  added,  in  a  thin  stream,  to  the  mass,  which  is  thoroughly  stiired  meanwhile  ; 
the  temperature  rises  slowly  to  165°  and  then  to  175°,  the  oxidisable  impurities  separating  as  a  black  mass  (asphalte) 
and  the  excess  of  sulphuric  acid  evaporating.  The  vessel  is  covered  and  provided  with  a  draught-pipe  to  carry 
off  the  acid  vapours.  The  mass  is  allowed  to  cool  slowly,  being  neutralised  with  residues  from  the  manufacture 
of  ferrocyanide,  decolorised  with  animal  black  and  sent  to  the  filter-presses.  The  mass  obtained  is  still  slightly 
yellow  and  is  whitened  by  further  treatment  with  sulphuric  acid.  When  beeswax  is  to  be  imitated,  quinoline 
yellow  or  other  coal-tar  dye  is  added. 


86 


tons  of  oil,  11,000  tons  of  crude  paraffin  wax  (equal  to  7600  tons  of  the  pure  wax,  worth 
£220,000),  and  8000  tons  of  creosote,  tar  and  pitch,  of  the  total  value  of  £450,000  ;  about 
1 ,000,000  tons  of  lignite  were  distilled  and  350,000  tons  of  coke  left.  For  several  years, 
however,  the  industry  has  been  stationary.  The  market  price  of  paraffin  wax  varies  some- 
what with  its  melting-point1  ;  white,  m.pt.  38-40°,  costs  78s.  per  quintal  ;  that  melting  at 
42-44°,  82s.  6d.  ;  at  48-50°,  85s.  6d.  ;  at  56-58°,  92s.  ;  and  at  60-62°,  £5.  That  used  in 
pharmacy,  m.pt.  74-76°,  costs  as  much  as  £9  12s.  Crude  paraffin  wax  is  sold  for  about 
56s.  During  recent  years,  however,  the  price  has  diminished  considerably  owing  to  the 
great  production  in  Galicia  (54,000  tons  in  1909  and  62,000  in  1910),  whence  a  considerable 
quantity  is  exported  into  Germany  even  at  less  than  32s.  per  quintal. 

In  1909  England  imported  53,000  tons  (£1,126,000)  of  paraffin,  and  exported  17,400 
tons  (£407,024)  ;  in  1910  the  exports  were  valued  at  £288,457. 

In  1903  Italy  imported  9526  tons  of  solid  paraffin  ;  in  1905  about  8880  tons  ;  in  1909 
17,400  tons,  and  in  1910  19,153  tons  of  the  value  of  £400,000,  in  addition  to  108  tons  of 
cerasin  worth  £4340.  The  production  of  paraffin  in  the  United  States  has  become  of 
great  importance,  the  Standard  Oil  Company  having  almost  the  monopoly  (95  per  cent, 
of  the  American  output)  ;  the  exportation  was  75,000  tons  in  1905,  85,000  tons  in  1909, 
95,000  tons  (£1,465,800)  in  1910,  and  97,000  tons  (£1,409,600)  in  1911.  From  the 
bituminous  shales  of  Scotland  23,000  tons  of  paraffin  wax  were  obtained  in  1910. 

Pure  white  cerasin  resembles  wax,  melts  at  62-80°,  and  has  the  sp.  gr.  0-918-0-922. 
It  is  used  in  making  candles,  in  perfumery,  and  as  dressing  for  textiles.  It  is  subject  to 
much  adulteration  owing  to  its  high  price  ;  the  yellow  of  the  first  quality,  m.pt.  62-63°, 
costs  108s.  or  more  per  quintal  ;  the  second  quality  92s.  ;  that  melting  at  68-70°  costs 
£6,  and  the  white,  m.pt.  62-63°,  £6  12s.2 

The  ozokerite  worked  in  Austria -Hungary  in  1877  amounted  to  8961  tons  ;  in  1885, 
13,000  tons  ;  and  in  1894,  6742  .tons.  The  exportation  of  cerasin  was  3594  tons  in  1891 
and  2382  tons  in  1895. 

In  the  United  States  the  production  of  refined  ozokerite,  which  was  160  tons  in  1888 
rose  in  1892  to  75,000  tons,  of  the  value  of  £4;000,000. 

1  The  estimation  of  the  paraffin  wax  in  a  commercial  sample  of  hard  paraffin  is  made  by  Holde's  method  : 
1  grm.  is  dissolved  in  a  test-tube  in  ether — excess  of  which  is  avoided — the  solu- 
tion cooled  to  —  20°  or  —  21°  and  an  equal  quantity  of  absolute  alcohol  added  ;  the 
paraffin  is  thus  separated  in  flakes,  and  if  the  mass  is  too  hard  to  be  filtered,  it  is 
diluted  with  the  mixture  of  alcohol  and  ether  cooled  to  -  20°  (see  Freezing  Mix- 
tures, vol.  i,  p.  229).  The  filtration  is  effected  under  pressure  in  a  funnel  sur- 
rounded with  the  freezing  mixture,  the  paraffin  being  washed  with  the  alcohol- 
ether  mixture  and  the  washings  kept  separate  from  the  first  filtrate  ;  the  latter  is  freed 
from  the  solvent  by  evaporation,  and  any  paraffin  wax  that  may  have  been  dissolved 
then  estimated.  The  paraffin  on  the  filter  is  dissolved  in  hot  benzine,  the  solution 
evaporated  in  a  tared  dish,  and  the  residue  dried  at  105°  and  weighed  ;  the  per- 
centage of  paraffin  wax  found  is  increased  by  1  to.  correct  for  constant  errors  of 
analysis.  The  apparatus  used  is  shown  in  Fig.  101 ;  the  solution  to  be  filtered  is 
kept  cold  in  the  test-tubes  immersed  in  the  freezing  mixture,  3,  surrounded 
by  felt,  2  ;  the  water  from  the  freezing  mixture  runs  off  at  5  and  that  which  drops 
collects  in  4. 

With  soft  paraffin  wax  Eisenlohr's  method  is  used  :  0-5  grm.  of  the  substance 
is  dissolved  in  100  c.c.  of  absolute  alcohol,  25  c.c.  of  water  being  added  and 
the  solution  cooled  to  - 18°  or  -  20°.  The  separated  paraffin  is  filtered  as 
described  above  and  washed  with  80  per  cent,  (by  volume)  alcohol  until  the  filtrate 
no  longer  turns  turbid  on  addition  of  water.  It  is  dried  in  vacua  at  40°  until 
constant. 

To  detect  the  addition  of  even  small  quantities  of  cerasin  (see  above)  Graefe 
dissolves  1  grin,  in  10  c.c.  of  carbon  disulphide  at  20°  and  treats  1  c.c.  of  this 
solution  with  10  c.c.  of  a  mixture  of  equal  volumes  of  alcohol  and  ether.  If 
undissolved  flocks  remain  even  after  heating  and  subsequent  cooling,  the  presence 
of  cerasin  is  certain  ;  this  result  can  be  confirmed  by  means  of  the  Zeiss  oleo- 
refractometer,  paraffin  wax  at  90°  showing  1-5  to  4,  and  cerasin  11-5  to  13  (Ulzer 
and  Sommer,  1906  ;  Berlinerblau,  1903). 

A  mixture  of  cerasin  and  paraffin  wax  can  be  detected  by  the  following  test :  a  glass  rod  3  mm.  in  diameter 
in  diameter  is  immersed  to  a  depth  of  1  cm.  in  the  fused  substance,  extracted,  allowed  to  cool  and  hung  in  a 
test-tube  heated  externally  with  water.  If  the  wax  drops  above  66°,  it  is  pure  cerasin,  whereas  if  it  drops  below 
66°  it  is  regarded  as  mixed  with  paraffin  wax  or  as  the  latter  alone.  -  The  dropping-point  can  also  be  determined 
with  tho  Ubbelohde  apparatus  (p.  6).  Addition  of  colophony  is  recognised  by  the  add  number  or  saponification 
nnmbw,  colophony  being  saponifiable  and  cerasin  not. 


L 1 

FIG.  101. 


OLEFINES 


87 


(b)    UNSATURATED   HYDROCARBONS 
I.  ETHYLENE  SERIES  :    CHH2n  (Alkylenes  or  defines) 

Two  groups  belong  to  this  series,  the  olefine  group,  the  first  member  of 
which  is  ethylene,  C2H4,  the  succeeding  ones  being  open-chain  hydrocarbons 
with  a  double  linking  between  two  carbon  atoms,  since  hydrogen,  halogens, 
ozone,  &c.,  can  be  readily  added  to  them,  transforming  them  into  saturated 
compounds  of  the  paraffin  series. 

The  other  group  yields  additive  products  only  with  difficulty,  and  its 
members  are  formed  of  closed  carbon-chains  (cyclic  compounds}.  The  first 
term  is  trimethylene  or  cyclopropane,  hexamethylene,  and  higher  compounds 
being  known  : 

-tL2  ri2 

c-cx 

H2C<  >CH2 

!_CH,  \c-cy 

II.,     II., 


CH, 


Trimethylene 


Hexamethylene 


The  carbon  atoms  in  these  last  compounds  are  all  in  the  same  conditions 
and  cannot  be  differentiated.  The  cyclic  compounds  will  be  studied  in  a 
separate  section  of  the  aromatic  series  (Part  III). 

The  following  Table  gives  the  more  important  members  of  the  olefine 
series  (the  number  in  parentheses  representing  boiling-points  under  reduced 
pressure)  : 


Melting- 
point 

Boiling- 
point 

Melting- 
point 

Boiling- 
point 

Ethylene,  C2H4       .      . 

-169° 

-103° 

Decylene,  C10H20    . 

— 

172° 

Propylene,  C3H6     . 

— 

-48° 

Endecylene,  C11H22 

— 

195° 

Butylene  (3  isoms.),!0, 
OH                         V 

— 

—  5° 
+  1° 

Dodecylene,  C^H^ 
Tridecylene,  C^H^ 

-31° 

(96°) 
233° 

°4±18                                       [y 

—  ' 

-6° 

Tetradecylene,  C^Hog 

-12° 

(127°) 

Amylene     (5     isoms.), 

Pentadecylene,  Ci5Tl30 

— 

'247° 

C5H10  ;           normal  - 

Hexadecylene     C16H32 

1     4°    ( 

274° 

amylene 

— 

+  35° 

(Cetene) 

}           \ 

(165°) 

Hexylene,  C8H12     . 

— 

68° 

Octadecylene,  C^gHgg  . 

+  18° 

(179°) 

Heptylene,  C7H14 

— 

98° 

Eicosylene,  C20H40       . 

— 

— 

Octylene,  C8H16 

— 

124° 

Cerolene,  C27H54     . 

+58° 

— 

Nonylene,  C9H18 

— 

153° 

Melene,  C30H60       .      . 

+  62° 

— 

The  official  nomenclature  of  the  defines  is  the  same  as  that  of  the  paraffins, 
excepting  that  the  final  ane  is  changed  into  ene  (thus  ethylene,  which  is  isologous 
with  ethane,  is  called  ethene,  and  so  on  ;  see  also  p.  28). 

These  unsaturated  hydrocarbons  differ  little  in  their  physical  properties 
from  the  corresponding  saturated  homologues. 


The  first  terms — up  to  C4H8 — are  gases, 


and  after  C5H10  come 


liquids 


with  increasing  boiling-points,  these  gradually  approaching  one  another  as 
in  the  paraffins  ;  the  higher  members  are  solid  and,  like  the  paraffins,  have 
a  sp.  gr.  0-63-0-79,  are  insoluble  in  water,  but  soluble  in  alcohol  or  ether. 

The  chemical  properties  differ  somewhat  from  those  of  the  saturated 
compounds.  Thus,  they  readily  take  up  HC1,  HBr,  HI,  Cl,  Br,  I,  fuming 
H2S04,  hypochlorous  acid  (giving  chloro-alcohols  or  chlorhydrins,  e.g. 


88  ORGANIC    CHEMISTRY 

CH2 :  CH2  +  HC10  =  CH2C1  •  CH2OH),  hyponitrous  acid,  ozone,  &c.,  forming 
compounds  of  the  saturated  series. 

Cl  is  added  more  easily  than  I,  Br  occupying  an  intermediate  position, 
whilst  HI  is  added  more  easily  than  HBr,  and  this  more  easily  than  HC1. 
With  these  acids,  the  halogen  is  added  to  the  carbon  atom  with  which  the 
least  hydrogen  is  combined. 

Ethylene  unites  with  fuming  sulphuric  acid  at  the  ordinary  temperature 
and  with  the  ordinary  acid  at  165°,  forming  ethylsulphuric  acid,  C2H50  •  S03H  ; 
with  higher  compounds,  the  acid  radicle  passes  to  the  less  hydrogenated 
carbon  atom. 

They  often  polymerise  under  the  action  of  sulphuric  acid  or  zinc  chloride  ; 
for  example,  amylene,  C5H10  forms  C10H20,  and  C15H30  gives  C20H40. 

They  are  readily  oxidisable,  for  example,  with  potassium  permanganate 
or  chromic  acid  (not  with  nitric  acid  in  the  cold),  the  chain  being  then  broken 
at  the  double  linking,  with  formation  of  oxygenated  compounds  (acids)  con- 
taining less  numbers  of  carbon  atoms  in  the  molecule.  Careful  use  of  per- 
manganate results  initially  in  the  addition  of  two  hydroxyl  groups  without 
breaking  the  chain  and  forming  dihydric  alcohols  (glycols),  for  example, 
OH-CH— CH-OH.1 

Almost  all  compounds  with  a  double  linking  between  atoms  of  carbon 
give  Baeyer's  reaction,  that  is  they  rapidly  discharge  the  violet  colour  of  a 
dilute  solution  of  potassium  permanganate  and  sodium  carbonate,  with  forma- 
tion of  a  reddish  brown  flocculent  precipitate  of  hydrated  manganese  peroxide. 

This  reaction  is  not  given  by  reducing  substances  like  aldehydes  or  by 
certain  aromatic  compounds  (phenanthrene,  &c.). 

All  compounds  with  doubly  linked  carbon  atoms  give  the  ozone  reaction 
(Harries,  1905,  and  Molinari,  1907),  that  is,  when  dissolved  in  a  suitable 
solvent  they  fix,  quantitatively  and  in  the  cold,  the  ozone  contained  in  a  current 
of  ozonised  air  passed  through  the  solution  ;  in  this  property  they  differ 
from  compounds  with  either  a  triple  linking  or  a  benzene  double  linking  (E. 
Molinari,  Ann.  Soc.  Chim.,  Milan,  1907,  116). 

METHODS  OF  PREPARATION.  (1)  They  are  formed,  together  with 
petroleum,  in  the  dry  distillation  of  wood,  lignite,  coal,  paraffin  ("  cracking," 
&c.). 

(2)  By  eliminating  water  from  the  alcohols,  CnH2w+iOH,  by  heating  them 
with  dehydrating  agents  (H2S04,  P205,  ZnCl2,  &c.)  ;    a  stable  intermediate 
product  is  sometimes  formed,  e.g.  ethyl-sulphuric  acid,  C2H5-HS04,  which 
at  a  higher  temperature  gives  ethylene  and  sulphuric  acid.     Higher  alcohols 
and  ethers  are  resolved,  merely  on  heating,  into  defines  and  water. 

(3)  From    saturated    halogen     derivatives     CwH2n+1X     (X  =  halogen), 
especially  from  secondary  and  tertiary  bromo-  and  iodo-derivatives,  by  heating 
them  with  alcoholic  potash,  or  by  passing  their  vapours  over  heated  lime 
or  lead  oxide,  &c. 

C5HUI  +  C2H5OK  =  KI  +  C2H5-OH  +  C5H10. 
The  mixed  ether,  C5HU  •  0  •  C2H5,  may  also  be  formed  to  some  extent. 

1  From  what  has  been  said  up  to  the  present,  it  is  obvious  that  a  double  Unking  does  not  signify  a  firmer 
union  between  carbon  atoms ;  it  is  simply  a  convention.  And  the  breaking  of  the  chain,  by  oxidising  agents, 
at  the  double  linking  is  to  be  attributed  to  the  ease  of  formation  of  intermediate  products  (e.g.  dihydric  alcohols) 
rather  than  to  a  less  attraction  existing  between  carbon  and  carbon  at  that  point.  Such  readiness  to  react  may, 
according  to  Baeyer,  be  explained  by  regarding  the  affinities  of  the  carbon  atom  as  orientated  or  grouped  at  four 
poles  arranged  like  the  vertices  of  a  regular  tetrahedron  (see  p.  18  et  seq.).  If  two  carbon  atoms  unite  by  a  double 
linking  the  poles  at  the  surface  of  the  carbon  atoms  become  displaced  and  approach  one  another,  so  that  there 
results  a  certain  tension  which  tends  to  restore  the  poles  to  their  original  positions  (Baeyer's  tension  hypothesis  of 
valency),  and  which  explains  the  readiness  with  which  the  double  linking  reacts  or  opens.  After  the  initial  oxidation 
leading  to  these  intermediate  products,  further  action  of  the  oxidising  agent,  as  a  general  rule,  oxidises  or  breaks 
the  chain  at  a  point  where  oxygen  already  exists,  that  is  where  the  oxidation  is  already  begun  (see  Part  III,  The 
Hypothesis  of  the  Partial  Valencies  of  the  Beniene  Nucleus). 


ETHYLENE  89 

(4)  From  dihalogenated  compounds  by  heating  with  zinc  : 

C2H4Bra  +  Zn  =  ZnBr2  +  C2H4. 

(5)  By  electrolysis  of  dibasic  acids  of  the  succinic  acid  series  : 

C2H4(COOH)2  =  C2H4  +  2C02  +  H2. 

(6)  Unsaturated  compounds  are  obtained  by  heating  the  condensation 
products  of  the  ketenes  (q.v.). 

CONSTITUTION  OF  THE  OLEFINES.  In  this  group  it  is  assumed  that  between 
two  carbon  atoms  there  exists  a  double  linking:  H2C=CH2,  H2C=CH  —  CH3,  &c.,  the 
presence  of  two  free  valencies,  thus,  H2C  —  CH2  or  HC  —  CH2,  being  excluded  for  the 
following  reasons  :  f\ 

In  unsaturated  compounds  the  addition  of  halogen  does  not  take  place  at  a  single  carbon 
atom,  so  that  ethylene  chloride,  C2H4C12,  has  not  the  formula  CH3  •  CHC12,  which  is  that 
of  ethylidene  chloride  obtained  from  acetaldehyde,  CH3  •  CHO,  by  replacement  of  the 
O  by  C12  (by  the  'action  of  PC16).  Since  ethylene  chloride  is  chemically  and  physically 
different  from  ethylidene  chloride,  the  former  must  have  the  constitutional  formula, 
CH2C1—  CH2C1,  and  the  third  formula  for  ethylene,  CH3—  CH<  is  thus  excluded.  The 
second  formula  is  not  probable  because,  if  the  existence  of  free  valencies  is  assumed,  they 
could  also  occur  in  non-adjacent  carbon  atoms,  and  thus  give  rise,  in  the  higher  hydro- 
carbons, to  numerous  isomerides  which  have,  however,  never  been  prepared  (if  propylene 
had  two  free  valencies,  four  isomerides  should  exist,  instead  of  only  one)  ;  further,  the 
addition  of  halogen  always  takes  place  at  two  contiguous  carbon  atoms  (see  Note  on 
preceding  page). 

Finally,  the  admission  of  free  valencies  in  organic  compounds  is  inadmissible  in  view 
of  the  unsuccessful  attempts  to  prepare  methylene  (or  methene),  CH2,  for  instance,  by 
eliminating  HC1  from  methyl  chloride,  2CH3C1  =  2HC1  +  2CH2<^  ;  the  two  methylene 
residues  always  condense,  forming  ethylene,  as  the  two  valencies  cannot  remain  free. 

ETHYLENE,  C2H4  (Ethene),  H2C  =  CH2.  This  is  a  gas,  becoming  liquid 
at  —103°  and  solid  at  —169°,  or  liquid  at  0°  under  44  atmos.  pressure.  It 
is  very  slightly  soluble  in  water  or  alcohol.  It  has  a  somewhat  sweet  smell 
and  burns  with  a  luminous  flame  ;  indeed,  illuminating  gas,  which  contains 
2  to  3  per  cent,  of  ethylene,  owes  part  of  its  luminosity  to  this  gas.  When 
mixed  with  2  vols.  of  chlorine  it  burns  with  a  dark-red  flame,  carbon  being 
deposited  and  HC1  formed.  At  a  red  heat  it  yields  C,  CH4,  C2H6,  C2H2,  &c.  ; 
with  hydrogen  in  presence  of  spongy  platinum  or,  better,  powdered  nickel  at 
300°,  it  is  converted  into  ethane. 

It  is  prepared  in  the  laboratory  by  heating  alcohol  with  excess  of  sulphuric 
acid  ;  as  an  intermediate  product,  ethyl-sulphuric  acid  is  formed,  this 
giving  ethylene  when  heated  :  C2H5-OH  +  H2S04  =  H20  +  C2H5HS04  ; 
C2H5HSO4  =  H2S04  +  C2H4.  Pure  ethylene  is  obtained  (1)  by  passing 
a  mixture  of  carbon  monoxide  and  hydrogen  over  finely  divided  nickel  or 
platinum  at  100°  :  2CO  +  2H2  =  C2H4  +  2H20  ;  (2)  by  dropping  alcohol  on 
to  phosphoric  acid  at  200-220°  ;  .or  (3)  from  ethylene  bromide  and  a  copper 
zinc  couple. 

PROPYLENE,  C3H6  (Propene),  CH2=CH—  CH3.  This  can  be  prepared  by  heating 
glycerol  with  zinc  dust  or  from  isopropyl  iodide  and  potassium  hydroxide.  It  is  a  gas 
which  liquefies  at  —48°  and  is  isomeric  with  trimethylene. 

BUTYLENES,  C4H8  (Butenes).  Three  isomerides,  the  a,  ft,  and  y,  are  known,  and  are 
obtained  by  treating  normal,  secondary,  and  tertiary  butylene  iodides  respectively  with 
potassium  hydroxide  : 


CH2  =CH—  CH2—  CH3  CH3—  CH  =CH—  CH3  3>C  =CH2 

Butene-l  («-butylene)  Butene-2  (0-butylene)  Methylpropene  (isobutylene) 

Tetramethylene  or  cyclobutane  is  isomeric  with  the  butylenes. 


90  ORGANIC    CHEMISTRY 

AMYLENES,  C5H10  (Pentenes).  Of  the  various  isomerides  theoretically  possible 
several  Have  been  prepared.  By  heating  fusel  oil  (of  distilleries)  with  zinc  chloride, 
pentanes  and  various  isomeric  amylenes  are  formed  which  can  be  separated  by  means  of 
the  different  velocities  with  which  HI  is  added  to  them,  or  by  the  property  possessed  by 
some  of  them  of  dissolving  in  the  cold  in  a  mixture  in  equal  parts  of  concentrated  sulphuric 
acid  and  water,  forming  amylsulphuric  acid,  whilst  the  others  either  do  not  react  or  give 
condensation  products  (di-  and  triamylenes). 

CEROTENE,  C27H54,  and  MELENE,  C30H60,  are  similar  to  paraffin,  and  are  obtained 
by  distilling  Chinese  wax  or  beeswax. 

II.  HYDROCARBONS  OF  THE  SERIES,  C,,H2,,  _2 

A.  With  Two  Double  Linkings  (Diolefines  or  Allenes) 

Of  the  few  known  terms  of  this  series,  the  first  and  best  investigated  is  ALLENE, 
H2C  :  C  :  CH2  (propandiene)  :  this  is  a  colourless  gas  which  differs  from  its  isomeride 
allylene  in  not  forming  metallic  derivatives  ;  it  is  obtained  by  eliminating  one  atom  of 
bromine  from  tribromopropane  by  means  of  potassium  hydroxide  and  the  remaining  two 
by  zinc  dust,  its  constitution  being  thus  rendered  evident  : 

CH2Br  •  CHBr  .  CH2Br-+  CH2  :  CBr  .  CH2Br-+  CH2    C  :  CH2. 

ERYTHRENE,  C4H6  (Pyrrolilene  or  Butane-1  :  3-diene),  CH2  :  CH-CH  :  CH2,  is  a 

gas  found  in  illuminating  gas,  and  when  heated  with  formic  acid  gives  erythritol. 

ISOPRENE,  C5H8,  boils  at  37°  and  is  obtained  by  distilling  rubber.  On  the  other 
hand,  with  concentrated  HC1,  it  condenses,  regenerating  rubber  or  forming  terpenes, 

riTj 

CioH^g,   CifrH-zi,   &c.     Since  dimethylallene,  r,TT3">C  :  C  :  CH2,  gives,   with  2HBr,  a  di- 


bromide,  nT,3^>CBr  •  CH2  •  CH2  •  Br,  which  is  identical  with  that  obtained  from  isoprene 
U±13 

CH2. 
+  2HBr,  the  constitution  of  isoprene  must  be  :  ^.C  •  CH  :  CH2, 

CH3/ 

The  normal  isomeride  PIPERYLENE,  CH2  :  CH-CH2.CH  :  CH2  (Pentane-1  :  4-diene) 
boils  at  42°  and  is  obtained  from  piperidine. 

DIALLYL,  C6Hio  (Hexine),  is  prepared  by  the  general  reaction  —  the  action  of  sodium 
on  allyl  iodide  —  which  indicates  its  constitution  : 

2CH2  :  CH-CH2I  +  2Na  =  CH2  :  CH  -  CH2  •  CH2  •  CH  :  CH2  +  2NaI. 

CONYLENE,  C8H14(1  :  4-octadiene),  CH2  :  CH-CH2-CH  :  CH2-CH2.CH3,  boils  at  126° 
and  is  obtained  from  coniine.  • 

B.   Hydrocarbons  with  Triple  Linkings  (Acetylene  Series) 

The  most  important  members  of  this  series  are  : 
Acetylene,  C2H2  (ethine),  HC=sCH,  gas. 
Allylene,  C3H4  (propine),  CH3-C=-CH,  gas. 

Crotonylene,  C4H6  (2-butine  or  dimethylacetylene),  CH3-C  I  C-CH3,  boils 
at  27°. 

Ethylacetylene,  C4H6  (3-butine),  CH3-CH2-C  :  CH,  boils  at  18°. 
Methyleihylacetylene,  C5H8  (3-pentine),  CH3-CH2-C  I  C-CH3,  boils  at  55°. 
n-Propylacetylene,  C5H8  (4-pentine),  CH3-CH2-CH2-C  •  CH,  boils  at  48°. 

Isopropylacetylene,C6H.s  (3-methyl-l-butine),  *:53>CH-C  I  CH,  boils  at  28°. 

U±i3 

Several  of  these  compounds  (the  first  three)  are  formed  during  the  dry 
distillation  of  coal  and  other  complex  substances,  and  are  hence  found  in 
lighting  gas. 

In  the  laboratory  they  are  obtained  by  the  following  methods  : 
{a)  By  electrolysing  acids  of  the  fumaric  acid  series  (see  later)  : 

COOH-CH  •  CH-COOH  =  H2  +  2C02  +  HC  '•  CH. 


ACETLYENES  91 

(6)  By  heating  with  alcoholic  potash  the  halogenated  compounds  (best 
the  bromo-derivatives)  CMH2wX2  and  CnH.,w_2X2,  gradual  elimination  of 
halogen  hydracid  (of  HBr  or,  in  presence  of  KOH,  of  KBr  and  H2O)  occurs : 

C2H4Br2  =  HBr  +  C2H3Br »HBr  +  C2H2. 

In  general,  starting  from  the  saturated  hydrocarbons,  CMH2n  +  2,  the  action 
of  halogen  and  elimination  of  halogen  hydracid  gives  an  unsaturated  hydrocarbon, 
CHH2n  ;  addition  of  halogen  to  this  and  subsequent  removal  of  halogen  hydracid 
gives  a  still  less  saturated  hydrocarbon,  CMH2M  _  2,  and  so  on. 

Elimination  of  2HC1  from  the  compounds  CnH2nCl2,  obtained  from  alde- 
hydes or  from  certain  ketones  (methylketones,  CMH2M+1-CO-CH3)  by  the 
action  of  PC15,  yields  always  a  trebly  linked  compound,  in  which,  however, 
one  of  the  carbon  atoms  is  always  united  to  a  single,  characteristic  hydrogen 
atom  :  — C  =  CH  ;  for  example,  acetaldehyde  gives  ethylidene  chloride, 
CH3  •  CHC12,  which  then  yields  2HC1  +  CH  i  CH  ;  while  acetone,  CH3  •  CO  •  CH3, 
gives  chloroacetone  CH3-CC12-CH3,  and  this  2HC1  +  CH3-C  =  CH,  the 
elimination  of  halogen  hydracid  never  occurring  in  such  a  way  as  to  give 
compounds  with  two  double  linkings,  such  as  CH2  :  C  :  CH2. 

Acetylene  derivatives  are  also  obtained  by  heating  the  acids  of  the  pro- 
piolic  series  (see  later), 

Compounds  with  this  characteristic  hydrogen  atom  — C^CH  have  a 
feebly  acid  character  and  form  solid  metallic  derivatives  (acetylides)  when 
treated  with  an  ammoniacal  solution  of  copper  chloride  or  silver  nitrate  : 
copper  acetylide,  Cu-C  :  C-Cu,  H20,  having  a  reddish  brown  colour  and 
apparently  the  constitution,  Cu2CH-CHO,  since  with  hydrogen  peroxide  it 
gives  acetaldehyde,  CH3  •  CHO  (Makowka,  1908) ;  and  silver  acetylide,  AgC  :  CAg, 
which  is  white  and  insoluble  in  water  or  ammonia  and,  in  the  dry  state,  is 
extremely  explosive,  simple  rubbing  being  sufficient  to  explode  it.  With 
hydrochloric  acid  it  regenerates  acetylene  in  a  pure  state. 

The  proof  that  it  is  the  characteristic  hydrogen  atom  which  is  replaced 
by  metals  lies  in  the  fact  that  acetylene  derivatives  from  other  ketones  (not 
from  methylketones)  do  not  give  metallic  acetylides  : 

CH3  •  CH2  •  CO  •  CH2  •  CH3 >CH3  •  CH2  •  CC12  •  CH2  •  CH3 > 

2HC1  +  CH3-C  i  C-CH2-CH3. 

Four  atoms  of  a  halogen  or  of  hydrogen  can  be  added  to  the  hydrocarbons 
of  the  acetylene  series,  saturated  compounds  being  formed  ;  but  as  a  rule 
only  two  atoms  are  readily  added,  although  under  the  action  of  light  four 
halogen  atoms  can  be  added  almost  always. 

The  compounds  of  the  olefine  series  can,  however,  be  distinguished  from 
those  of  the  acetylene  series  by  means  of  the  ozone  reaction,  since  compounds 
with  a  triple  linking  do  not  fix  ozone  at  all  (Molinari). 

The  hydrocarbons  of  the  acetylene  series  take  up  a  molecule  of  water  in 
presence  of  mercury  salts,  giving  rise  to  complex  mercuric  compounds, 
which,  with  HC1,  give  as  final  product  an  aldehyde  or  ketone  ot  the  satu- 
rated series— CH.J-C  i  CH  (aUylene)  +  H2O  =  CH3-CO-CH3  (acetone)  or 
CH  i  CH  +  H20  =  CH3-CHO  (acetaldehyde).  This  last  reaction  serves  to 
illustrate  the  transformation  of  inorganic  into  organic  substances  (see  later, 
p.  108). 

In  the  acetylene  series,  also,  condensation  or  polymerisation  is  possible, 
three  molecules  of  acetylene,  on  heating,  yielding  benzene  C6H6  ;  three  mols. 
of  dimethylacetylene,  C4H6,  giving,  with  concentrated  sulphuric  acid,  hexa- 
methylbenzene,  C6(CH3)6,  and  allylene  C3H4  similarly,,  yielding  trimethylbenzene 
(mesitylene)  C6H3(CH3)3. 


92  ORGANIC    CHEMISTRY 

In  the  higher  compounds,  the  position  of  the  triple  bond  is  deduced  from 
the  oxidation  products,  since,  as  with  substances  with  a  double  linking,  the 
breaking  of  the  chain  occurs  at  the  multiple  linking. 

When  certain  acetylene  derivatives,  e.g.  XC=ssC-CH3,  are  heated  with 
sodium,  the  triple  bond  changes  its  position,  the  products  being  sodium 
derivatives  of  isomeric  hydrocarbons,  X-CH2-C  :  CH  (these  give  metallic 
acetylides,  but  the  original  compounds  do  not) ;  when  these  are  heated  with 
alcoholic  potash,  the  reverse  change  occurs. 

ACETYLENE,  C2H2  (Ethine),  HC  •  CH.  Without  having  isolated  or 
characterised  this  compound,  Davy  obtained  it  in  1839  in  a  very  impure 
condition,  by  treating  with  water  the  product  obtained  by  heating  together 
potassium  carbonate  and  carbon,  which  should  yield  potassium.  Bert  helot 
first  obtained  it  pure  (and  named  it)  in  1859,  by  passing  ethylene  or  alcohol 
or  ether  vapour  through  a  red-hot  tube  ;  he  prepared  it  also  by  means  of  a 
voltaic  arc  passing  between  two  carbons  in  an  atmosphere  of  hydrogen.  In 
1862,  Wohler  prepared  it  by  treating  calcium  carbide  (obtained  by  heating 
carbon  with  an  alloy  of  zinc  and  calcium)  with  water. 

It  is  formed  in  the  incomplete  combustion  of  various  hydrocarbons  and 
of  illuminating  gas  (e.g.  in  the  flame  of  a  bunsen  burner  alight  at  the  bottom). 

But  the  industrial  preparation  of  acetylene  has  assumed  great  and  unfore- 
seen practical  importance  since  1870,  when  it  became  possible  to  prepare 
calcium  carbide  on  an  enormous  industrial  scale  by  means  of  the  electric  furnace 
(see  Calcium  Carbide  Industry,  vol.  i,  p.  504) : 

cx 

\]  >Ca  +  2EUO  =  Ca(OH)2  +  HC  \  CH. 
•     C/ 

Acetylene  is  a  colourless  gas,  sp.  gr.  0-92  (1  litre  weighs  1-165  grm.)  with 
a  pleasant  odour  when  pure  and  a  disagreeable  one  when  impure  (as  usually 
obtained).  At  +  1°  under  a  pressure  of  48  atmos.  it  forms  a  highly  refractive, 
mobile,  colourless  liquid,  sp.  gr.  0-451,  and,  on  evaporating  rapidly,  partially 
solidifies  in  the  form  of  snow,  m.pt.  —81°. 

One  volume  of  acetylene  gas  dissolves  in  1-1  vol.  of  water,  or  in  |-  vol.  of 
alcohol  or  in  20  vols.  of  saturated  salt  solution  ;  1  litre  of  acetone  dissolves 
24  litres  of  acetylene,  or  300  litres  at  12  atmos.,  or  about  2000  litres  at  —80°, 
its  volume  being  then  increased  fourfold.  Permanganate  oxidises  it  giving 
oxalic  acid,  and  chromic  acid  acetic  acid. 

It  is  an  endothermic  compound,  requiring  for  its  formation  from  its  elements, 
61,000  cals.  ;  it  is  hence  very  unstable  and  is  readily  decomposed  by  the 
detonation  of  a  mercury  fulminate  cap  or  by  an  electric  discharge,  developing 
as  much  heat  as  an  equal  volume  of  hydrogen  on  conversion  into  water.  The 
explosion  takes  place  much  more  readily  and  is  much  more  dangerous  with 
the  compressed  gas  and  still  more  so  with  the  liquid. 

Acetylene  decomposes  at  780°  and,  when  mixed  with  air,  ignites  at  480°. 
One  cubic  metre  (1-165  kilo)  of  acetylene,  in  burning,  develops  14,350  Cals. 
(12,300  Cals.  per  kilo),  whilst  ordinary  coal-gas  gives  about  5000  Cals. 

When  mixed  with  air  or,  better,  with  oxygen  it  forms  a  detonating  mixture 
which  explodes  with  great  energy  in  contact  with  an  ignited  body.  The 
explosion  is  violent  even  with  1  vol.  of  acetylene  and  40  vols.  of  air  ;  it  reaches 
its  maximum  violence  with  1  vol.  of  the  gas  and  12  vols.  of  air  (2-5  vols.  of 
oxygen),  whilst  scarcely  any  explosion  but  mere  burning  takes  place  with 
1  vol.  of  acetylene  and  1-3  vol.  of  air  (as  has  been  already  stated  on  p.  33, 
ordinary  illuminating  gas  only  explodes  when  at  least  1  vol.  is  present  to 
about  20  vols.  of  air). 

Explosive  mixtures  of  acetylene  are  more  dangerous  than  those  of  coal-gas 


ACETYLENE  93 

owing  to  the  greater  speed  of  propagation  of  the  explosion  (e.g.  with  1  vol.  of 
acetylene  and  40  of  air),  the  explosive  force  being  thus  increased  (see  section 
on  Explosives)  ;  further,  acetylene  contains  less  hydrogen  and  hence  forms 
less  water,  the  condensation  of  the  gases  resulting  from  the  explosion  being 
consequently  smaller.  The  wide  limits  of  the  explosive  mixtures  (from  2-4 
to  130  vols.  of  acetylene  per  100  vols.  of  air)  are  explained  by  the  fact  that  this 
gas,  being  an  endothermic  compound,  reacts  or  decomposes  with  great  facility. 

In  contact  with  copper,  bronze,  silver,  &c.,  acetylene  readily  forms  explosive 
acetylides  (see  p.  91).1 

It  was  at  first  thought  that  acetylene,  like  carbon  monoxide,  was  poisonous, 
but  experiments  made  during  the  last  few  years  have  shown  that  animals  do 
not  die  in  an  atmosphere  containing  9  per  cent,  or,  in  some  cases,  even  20  per 
cent,  of  the  gas.  When,  however,  the  acetylene  is  highly  contaminated  with 
sulphides  and  phosphides,  it  may  be  poisonous. 

With  an  ordinary  gas-jet,  acetylene  burns  with  a  reddish,  smoky  flame  ; 
but  by  passing  the  gas  at  a  pressure  of  60  mm.  through  two  jets  nearly  meeting 
at  an  angle,  a  white,  highly  luminous,  fan-shaped  flame  is  obtained  without 
the  dark  middle  portion  of  the  ordinary  bat's-wing  coal-gas  flame. 

One  kilo  of  chemically  pure  calcium  carbide  should  yield  theoretically  349  litres  of 
acetylene,  and  good  commercial  carbide  yields  practically  300  litres.  The  luminosity  of 
acetylene  in  comparison  with  that  of  other  substances  has  already  been  referred  to  on 
p.  57.  A  proportion  of  2  vols.  of  air  to  3  of  acetylene  gives  the  maximum  luminosity, 
and  at  the  present  time  special  incandescent  mantles  are  made  for  use  with  acetylene. 

The  impurities  present  in  ordinary  acetylene  (98-99  per  cent,  purity)  are  :  N,  NH3, 
CO,  H2S  and  PH3,  the  last  three  of  which  are  poisonous.  The  gas  is  purified  by  passing 
it  through  an  acid  solution  of  a  metallic  salt. 

Lunge  and  Cederkreutz  recommend  chloride  of  lime  (hypochlorite)  for  purifying 
acetylene,  care  being  taken  that  the  mass  does  not  heat,  as  this  would  be  dangerous. 
Latterly  it  has  been  suggested  to  fix  the  PH3  by  passing  the  gas  through  concentrated 
sulphuric  acid  (64°  Be.)  saturated  with  As203.  A  good  purifying  material  is  made 
by  preparing  a  paste  of  calcium  hypochlorite,  quicklime,  sodium  silicate  and  powdered 
calcium  carbide,  this  remaining  porous  when  allowed  to  dry  in  the  air. 

The  use  of  liquid  acetylene  would  be  very  convenient,  but  is  highly  dangerous,  since 
a  sharp  blow  or  other  accident  might  easily  produce  a  terrible  explosion. 

It  is  still  too  expensive  to  employ  in  place  of  benzene  for  carburetting  coal-gas. 
Dissolved  in  acetone,  which  dissolves  a  large  quantity  of  it  (vide  supra),  it  is  used  to  great 
advantage  for  the  oxy-acetylene  blowpipe  in  place  of  oxy-hydrogen.  With  the  latter,  for 
every  cubic  metre  of  oxygen  4  cu.  metres  of  hydrogen  are  used  practically  (theoretically 
2  cu.  metres),  whilst  the  same  amount  of  oxygen  burns  with  600  litres  of  acetylene 
(theoretically  400  litres),  which  costs  much  less  than  4  cu.  metres  of  hydrogen.  The  oxy- 
acetylene  flame  exhibits  at  the  centre  a  shining  point,  which  has  a  temperature  of 
2800-3000°,  and  to  fuse  iron  sheets  1  mm.  thick  requires  50-75  litres  of  acetylene,  while 
in  an  hour  sheets  5  mm.  in  thickness  can  be  melted. 

With  a  slight  excess  of  oxygen  large  tubes  are  easily  cut  and  steel  blocks  perforated. 

Acetylene  dissolved  in  acetone,  especially  if  the  solution  is  absorbed  by  porous  material, 
is  not  at  all  dangerous  and  can  be  transported  in  iron  cylinders. 

The  hope  of  manufacturing  synthetic  alcohol  economically  from  acetylene  has  died 
out.  Even  for  motors  it  is  still  too  dear  to  use.  Acetylene  can,  however,  be  used 
conveniently  with  a  rational  plant  and  relatively  small  gasometers  connected  with  iron 
tubes  which  carry  the  gas  direct  to  the  burners  (when  prepared  from  pure  carbide)  ;  but 
it  is  necessary  to  avoid  the  use  of  copper  or  bronze  in  any  part  of  the  gasometers,  pipes 

1  The  ready  formation  of  metallic  acetylides,  especially  that  of  copper,  led  Brdmann  (1907)  to  devise  a  rapid 
and  exact  analytical  method  for  the  direct  quantitative  precipitation  of  copper  from  any  solution  and  in  presence 
of  any  metals  (except  Ag,  Hg,  Au,  Pd,  and  Os,  which  must  be  previously  eliminated) ;  the  feebly  alkaline  solution 
of  the  copper  salt  is  reduced  until  decolorised  with  hydroxylamine  hydrochloride,  C2H2  being  then  passed  through 
and  the  precipitated  copper  acetylide  collected  on  a  filter,  washed  with  water  and  pumped  off ;  together  with 
the  filter-paper  it  is  introduced  into  a  porcelain  crucible,  treated  with  10  to  15  c.c.  of  dilute  nitric  acid  <sp.  gr.  1-15) 
and  eight  to  ten  drops  of  concentrated  nitric  acid  (sp.  gr.  1-52),  dried  on  a  water-bath,  heated  rapidly  to  redness 
and  weighed  as  CuO.  The  acetylene  used  for  this  precipitation  should  be  washed  with  lead  acetate  solution. 


94  ORGANIC    CHEMISTRY 

and  taps,  in  order  to  avoid  explosions,  which  are  almost  always  due  to  the  formation  of 
copper  acetylide.1 

In  testing  the  purity  of  acetylene  the  only  quantitative  determination  usually  made 
is  that  of  the  hydrogen  phosphide,  which  should  not  occur  in  greater  proportion  than 
1  grm.  per  cubic  metre,  since,  besides  being  poisonous  and  having  an  unpleasant  smell,  it 
facilitates  the  formation  of  explosive  metallic  acetylides.  (The  estimation  of  the  impurities 
in  carbide  is  described  in  vol.  i,  p.  505.) 

III.  HYDROCARBONS  OF  THE  SERIES  C,,H2,,_4  and  C,,H,,,.6 

DI ACETYLENE,  C4H2  (Butandiine),  CH  i  C-C  :  CH,  is  a  gas  and  forms  the  usual 
metallic  acetylides. 

DIPROPARGYL,  C6H6  (Hexan-1  :  5-diine),  CH  •  C.CH2-CH2-C  i  CH,  is  isomeric 
with  benzene,  boils  at  85°,  and  can  take  up  8  atoms  of  bromine.  It  is  obtained  from 
diallyl  and  readily  forms  metallic  acetylides. 

HEXAN-3  :  4-DIINE,  CH3'C  i  C-C  •  C-CH3,  is  also  isomeric  with  benzene. 


BB.   HALOGEN   DERIVATIVES   OF   THE   HYDROCARBONS 

The  Table  on  page  95  summarises  the  physical  properties  of  the  more 
important  halogen  derivatives  of  the  hydrocarbons,  the  first  column  giving 
the  hydrocarbon  residue  (alkyl)  united  with  the  halogen. 

I.   HALOGEN  DERIVATIVES  OF  SATURATED  HYDROCARBONS 

PROPERTIES.  Very  few  are  gases,  several  are  liquids  and,  those  which 
contain  many  atoms  in  the  molecule  are  solids.  The  iodo-compouiids 
boil  at  higher  temperatures  than  the  corresponding  bromo-  and  chloro- 
compounds.  They  are  very  slightly,  if  at  all,  soluble  in  water,  but  are  readily 
soluble  in  alcohol,  ether,  and  glacial  acetic  acid. 

Most  of  them  burn  easily,  and  ethyl  and  methyl  chlorides  colour  the  edges 
of  the  flame  green.  Some  of  them,  containing  few  carbon  atoms,  produce 
ancesthesia,  e.g.  CHC13,  CH2C12,  C2H3C13,  C2H5Br,  C2H5C1. 

Generally  they  do  not  react  with  silver  nitrate,  since  these  compounds, 
in  solution,  are  not  dissociated  and  do  not  give  free  halogen  ions  (see  vol.  i. 
p.  91  et  seq.).  In  alcoholic  solution,  ethyl  iodide  gives  a  little  precipitate  in 
the  cold,  and  ethyl  bromide  in  the  hot,  whilst  the  chloride  gives  no  precipitate 
at  all,  with  silver  nitrate. 

The  bromo-  and  iodo-compounds  exhibit  great  reactivity  and  effect  the 
most  varied  and  interesting  reactions  and  syntheses  ;  methyl  iodide  reacts 
the  most  readily  of  all,  since  the  reactivity  diminishes  with  increase  of  mole- 
cular weight. 

The  halogens  of  these  compounds  can  easily  be  replaced  by  H  (by  sodium- 
amalgam,  or  zinc  dust  and  hydrochloric  or  acetic  acid). 

These  derivatives  can,  to  some  extent,  be  transformed  one  into  the  other, 
e.g.  the  chlorides  into  iodides  by  treatment  with  KI  or  CaI2,  and  the  iodides 
into  the  fluorides  (more  volatile  than  the  chlorides)  by  means  of  silver  fluoride. 

1  The  numerous  types  of  apparatus  for  generating  acetylene  may  be  divided  into  three  groups  : 

(1)  Those  where  the  carbide  and  water  are  in  separate  vessels  communicating  by  a  tube  furnished  with  a  tap 
which  automatically  opens  more  or  less  and  so  diminishes  or  increases  the  supply  of  the  gas.      To  prevent  the 
carbide,  or  rather  the  lime  formed,  from  holding  water  and  generating  gaseven  after  the  tap  is  closed,  the  carbide 
is  impregnated  with  an  indifferent  substance,  e.g.  paraffin,  stearin,  oil,  sugar  (to  dissolve  the  lime  as  calcium 
saccharat  e).  &c.     One  inconvenience  of  this  procedure  is  that  at  some  places  the  carbide,  in  presence  of  little  water, 
becomes  excessively  heated  and  may  produce  an  explosion,  which  is  dangerous  if  the  gas  is  under  pressure. 

(2)  Those  where  the  carbide  is  suspended  at  a  certain  part  of  the  vessel  containing  the  water ;   acetylene  is 
then  generated  when  the  level  of  the  water  rises  to  the  carbide  and  ceases  automatically  when  it  falls. 

(3)  Those  where  the  carbide  and  water  are  separated,  a  small  quantity  of  carbide  being  dropped  into  excess  of 
water.     This  would  be  the  most  rational  method,  but  is  perhaps  not  the  most  convenient  owing  to  the  difficulty  of 
powdering  the  carbide  (often  very  hard)  without  allowing  it  to  absorb  moisture. 


HALOGEN    DERIVATIVES 


95 


Alkyl 

Names  of  the  Alkyls 
and  Isomeridcs 

Chlorides 

Bromides 

Iodides 

B.-pt. 

Sp.gr. 

B.-pt. 

Sp.gr. 

B.-pt. 

Sp.gr. 

(a)  SATURATED 

DERIVATIVES 

(1)  MonositbgtUtUed 

CH, 

Methyl 

-  23-7° 

0-952  (0°) 

+  4-5° 

1-732  (0°) 

+  45° 

2-293  (18°) 

CjH5 

Ethyl 

+  12-2° 

0-918  (0°) 

38-4° 

1-468  (13°) 

+  72-3' 

1-944  (14') 

C,H7 

n-Propyl 

+  46-5° 

0-912  (0°) 

71° 

1-383  (0°) 

102-5° 

1-786  (0°) 

Isopropyl 

36-5° 

0-882  (0°) 

60° 

1-340°  (0°) 

89° 

1-744  (0°) 

C«H, 

n-Butyl  (primary) 

78° 

0-907  (0°) 

101° 

1-305  (0°) 

130° 

1-643  (0°) 

Isobutyl 

68-5° 

0-895  (0°) 

92° 

1-204  (16°) 

119° 

1-640  (0°) 

sec.-Butyl 

— 

— 

— 

— 

119-120° 

1-626  (0°) 

tert.-Butyl 

56° 

0-866  (0°) 

Tfl 

1-215  (20°) 

100° 

1-571  (0°) 

C5Hn 

n-Ainyl  (primary) 

107" 

0-901  (0°) 

129° 

1-246  (0°) 

156° 

1-543  (0°) 

Isoamyl,  (CH,),    CH- 

.101° 

0-893  (0°). 

121° 

1-236  (0°) 

148° 

1-468  (0°) 

CH,-CH,-X 

tertiary-Butylmethyl 

— 

0-879  (0°) 

— 

1-225  (0°) 

— 

1-050?  (0°) 

(CH,),C-CH,-X 

active-  Amyl 

97-99° 

0-886  (15°) 

118-120° 

1-221  (20°) 

148° 

1-524  (20°) 

(CH,)(C,H,)CH-  CH,-  X 

C.H,, 

n-Hexyl  (primary) 

134° 

0-892  (16°) 

156° 

1-193  (0°) 

182° 

1-461  (0°) 

n-Hexyl  (secondary) 

— 

— 

144° 

— 

168° 

1-453  (0°) 

C7HU 

n-Heptyl  (primary) 

159° 

0-881  (16°) 

179° 

1-113  (16°) 

201° 

1-386  (16°) 

C»HI7 

n-Octyl  (primary) 

180° 

0-880  (16°) 

199° 

1-116  (16°) 

221° 

1-345  (16°) 

(2)  Disubsttiuied 

>CH, 

Jlethylene,  CH,X, 

42° 

— 

97° 

— 

180° 

— 

-CH2-CH2— 

Ethylene 

84° 

— 

131° 

— 

— 

— 

CH,  CH2< 

Ethylidene  (or  ethydene) 

57° 

— 

108° 

» 

— 

— 

(3)  Trisubstituted 

CHX,  (chloroform, 

61" 

— 

161" 

— 

solid 

•     — 

bromoform,  iodoform) 

mpt.H9° 

CH.-CC1,  methyl  chloro- 

74° 

— 

188° 

— 

— 

— 

form  (a-trichloroethane 

CH.C1-CHC1,  (/3-tri- 

114° 

— 

220° 

— 

— 

— 

chloroethane) 

CH.X-CHX-CH,X   (tri- 

168° 

— 

— 

— 

— 

— 

chlorohydrin,           tri- 

bromohydrin) 

(4)  Polysvbftituted 

CX4   (carbon   tetra- 

77° 

— 

— 

— 

solid 

— 

chloride,  iodide) 

CaCl,  perchloroethane 

solid 

— 

— 

— 

— 

— 

m.pt.  187 

(&)  UNSATURATED 

DERIVATIVES 

(1)  Ethylenic  series 

CH,  :CH-X 

Vinyl  chloride,  &c. 

-  18° 

— 

23° 

— 

56° 

— 

C,H,-X 

AUyl 

46° 

— 

70° 

— 

101° 

— 

CVH,:XS 

Dichloroethylene 

55° 

— 

— 

— 

— 

— 

G,H  :  X, 

Trichloroethylene 

88° 

— 

— 

— 

— 

— 

C,  :  X4 

Tetrachloroethylene 

121° 

— 

— 

— 

— 

(2)  Acetylene  tenet 

HC:  CX 

Monochloro-  and  mono- 

gas 

— 

gas 

_ 

— 

— 

bromo-acetylene 

METHODS  OF  PREPARATION,  (a)  By  the  action  of  halogens  on 
saturated  h3rdrocarbons  :  chlorine  and  bromine  react  directly  at  the  ordinary 
temperature  on  the  gaseous  hydrocarbons,  and  on  heating  with  the  liquid  ones. 

The  first  halogen  atom  is  fixed  more  readily  than  the  succeeding  ones, 
and  the  addition  of  iodine  facilitates  the  reaction  with  bromine  and  chlorine, 
since  the  iodine  forms,  for  example,  IC13,  which  readily  gives  nascent  chlorine, 
IC13  =  IC1  +  C12  (i.e.  it  acts  like  SbCl5,  which  yields  SbCl3  +  Cl?).  By 
saturating  with  chlorine  and  heating  under  pressure  energetic  chlorinations 
may  be  effected. 

Methane,  ethane,  propane,  &c.,  exchange   their  hydrogen  atoms  one  by 


96  ORGANIC    CHEMISTRY 

one  for  chlorine  atoms,  the  completely  substituted  compounds  (C2C16,  C3C18,  &c., 
and  especially  the  higher  ones),  on  further  energetic  chlorination,  being  resolved 
into  other  completely  chlorinated  compounds  containing  less  numbers  of 
carbon  atoms  :  C2C16  +  C12  =  2CC14  ;  C3C18  +  C12  =  C2C16  +  CC14,  a  little 
hexachlorobenzene,  &c.,  being  always  formed  as  well. 

Iodine  scarcely  ever  acts   directly  on  the  hydrocarbons,   since  the   HI, 
formed  acts  in  the  opposite  sense  on  the  iodo-products.     The  reaction  proceeds 
only  in  presence  of  iodic  acid  or  mercuric  oxide,  which  fixes  the  hydrioclic 
acid  as  it  is  formed. 

The  iodo -compounds  are  easily  obtained  from  zinc-alkyls  and  iodine. 

When  the  halogens  act  directly,  the  more  energetic  (F  or  Cl)  replaces  the 
weaker  (Br  or  I).  The  iodo-compounds  may,  however,  be  easily  obtained  by 
preparing  first  the  magnesium  compounds  of  the  alkyl  chlorides  or  bromides 
and  treating  these  with  iodine  : 

Alkyl-Mg-Cl  +  I2    =    Alkyl-I  +  MglCl. 

(b)  Unsaturated  hydrocarbons,  with  the  halogen  hydracids,  give   saturated 
monosubstituted  derivatives  :    C2H4  +  HBr  =  C2H5Br,  ethyl    bromide,  &c.  ; 
if  the  halogens  act  directly,  disubstituted  saturated   products  are  obtained  : 
C2H4  +  C12  =  C2H4C12,  ethylene  dichloride. 

Propylene,  CH  •  3CH :  CH2,  reacts  with  HI  giving  isopropyl  iodide, 
CH3-CHI-CH3,  which  is  decomposed  by  alcoholic  potash,  yielding  propylene  ; 
but  normal  propyl  iodide,  CH3-CH2-CH2I,  which  also  yields  propylene  when 
HI  is  removed  from  it,  can  thus  be  converted  into  isopropyl  iodide. 

Similar  behaviour  is  exhibited  by  the  butyl  iodides. 

The  halogen  always  goes  to  the  carbon  atom  united  with  the  lesser  number  of 
hydrogen  atoms  :  CH3-CH  :  CH2  +  HI  =  CH3-CHI-CH3. 

(c)  The     alcohols     CwH2w+1OH      with     the     halogen      hydracids     give  : 
CwH2n+1OH  +  HBr  =  H20  +  CjjHg^+jBr,  but  the   reverse  action   also   pro- 
ceeds and  to  limit  this,  excess  of  the  halogen  hydracid  is  used  and  the  water 
formed  is  fixed,  e.g.  by  addition  of  zinc  chloride. 

Further,  the  chlorine  of  the  phosphorus  chlorides  also  replaces  hydroxyl  : 
PC13  +  3C2H5OH  =  P(OH)3  +  3C2HsCl,  or,  better,  PC15  +  C2H5OH  = 
POC13  +  HC1  +  C2H5C1.  This  reaction  is  of  importance  for  the  preparation 
of  the  bromo- and  iodo-compounds  :  3CH3-OH  +  P  +  31  =  3CH3I  +  H3P03; 
the  bromine  or  iodine  first  acts  on  the  phosphorus  to  form  PBr3  or  PI3,  this 
then  reacting  with  the  alcohol. 

The  polyhydric  alcohols  act  in  the  same  way  ;  for  example,  glycerol, 
C3H5(OH)3  reacts  with  PC15  giving  trichlorohydrin,  CH2C1  •  CHC1  •  CH2C1. 

The  resulting  halogenated  products  are  easily  separated  by  distillation, 
as  the  phosphoric  acid  does  not  distil.  In  these,  as  in  most  other  chemical 
reactions,  secondary  products  are  always  formed  ;  these  are  often  very  com- 
plex and  form  viscous  resins  of  unknown  composition. 

(d)  The  aldehydes  and  Tcetones  yield  disubstituted  products  :   for  example, 
ethylidene  chloride,  CH3-CHC12,  is  obtained   from  acetaldehyde,  CH3-CHO, 
and  dichloropropane,   CH3  •  CC12  •  CH3,   from    acetone,   CH3-CO-CH3,   by  the 
action  of  PC15. 

METHYL  CHLORIDE  (Chloromethane),  CH3C1.  This  is  prepared  by 
passing  hydrogen  chloride  into  boiling  methyl  alcohol  containing  half  its 
weight  of  zinc  chloride  in  solution,  or  by  heating  1  part  of  methyl  alcohol 
with  3  parts  of  concentrated  sulphuric  acid  and  2  parts  of  concentrated  hydro- 
chloric acid.  Industrially  it  can  be  obtained  by  heating  methyl  alcohol  and 
crude,  concentrated  hydrochloric  acid  together  in  an  autoclave. 

It  is  also  obtained  to-day  in  appreciable  quantity,  by  the  old  Vincent 
process,  from  the  final  residues  of  the  beet-sugar  industry,  which  are  evaporated 


ALKYL  HALOGEN  COMPOUNDS      97 

and  then  dry-distilled.  In  this  way  an  abundant  quantity  of  trimethylamine 
is  formed  ;  this  is  neutralised  with  HC1,  and  the  hydrochloride  distilled  at 
300°.  A  regular  evolution  of  methyl  chloride  and  trimethylamine  is  thus 
obtained  :  3N(CH3)3HC1  =  2CH3C1  +  2N(CH3)3  +  CH3-NH2-HC1. 

Triinethylamine  hydro-  Trimethyl-  Methylamine  hydro- 

chloride  amine  chloride    (residue) 

The  chloromethane,  distilled  as  a  gas,  is  purified  with  HC1,  dried  with 
CaCl2,  and  liquefied  in  steel  cylinders  under  pressure,  just  as  is  done  with 
carbon  dioxide  (vol.  i,  p.  382). 

It  is  a  colourless  gas  of  ethereal  odour,  and  at  —  23-7°  becomes  liquid, 
then  having  a  sp.  gr.  0-952  (at  0°).  Water  dissolves  one-fourth  of  its  volume, 
and  alcohol  rather  more.  It  burns  with  a  green-edged  flame. 

In  the  liquefied  condition  it  is  used  as  a  local  anaesthetic  ;  it  is  used  also 
to  extract  perfumes  from  flowers,  and  in  considerable  quantities  for  the 
manufacture  of  dyestuffs  (methyl  green),  especially  for  methylation ;  but 
the  greatest  amount  is  employed  in  cooling  machines.  In  France  there  are 
about  100  ice-machines  which  use  methyl  chloride  instead  of  liquefied  NH3, 
C02,  or  S02.  In  brass  cylinders  containing  from  1  to  30  kilos  it  is  sold  at 
11s.  to  14s.  Qd.  per  kilo,  in  addition  to  the  cost  of  the  cylinder,  which  is 
20s.  for  the  1-kilo,  25s.  Qd.  for  the  3-kilo,  and  £3  16s.  for  the  30-kilo  size. 

METHYL  IODIDE,  CH3I,  is  prepared  from  methyl  alcohol,  phosphorus,  and  iodine 
as  described  later  for  ethyl  iodide.  It  is  a  liquid  of  sp.  gr.  2-293,  boiling  at  45°  ;  with 
excess  of  water  at  100°  it  is  decomposed  into  hydrogen  iodide  and  methyl  alcohol. 

ETHYL  CHLORIDE  (Chloroethane),  C2H5C1,  was  termed  by  Basil  Valentine  "  Spiritus 
salis  et  vini,"  or  spirit  of  sweet  wine.  It  is  obtained  from  ethane  and  chlorine,  or  by  passing 
hydrogen  chloride  into  a  solution  of  zinc  chloride  and  ethyl  alcohol.  It  is  also  formed  as 
a  secondary  product  in  the  manufacture  of  chloral.  It  boils  at  +  12-2°  and  burns  with  a 
flame  having  green  edges.  It  is  a  local  anaesthetic  and  is  soluble  in  alcohol,  but  only  slightly 
so  in  water.  It  costs  from  Is.  Id.  to  4s.  per  kilo  in  metal  cylinders  containing  1  to  30  kilos. 

ETHYL  IODIDE,  C2H5I,  is  prepared  by  digesting  10  grms.  of  red  phosphorus  with  80 
grms.  of  absolute  alcohol  for  12  hour's  and  gradually  adding  100  grms.  of  iodine  ;  the  mix- 
ture is  then  heated  for  2  hours  under  a  reflux  condenser  and  the  ethyl  iodide  distilled  on 
the  water-bath,  washed  with  dilute  alkali  and  with  water,  and  dried  by  means  of  calcium 
chloride.  According  to  Ger.  Pat.  175,209,  ethyl  iodide  is  obtained  quantitatively  if 
diethyl  sulphate  is  slowly  added  to  the  calculated  amount  of  hot  potassium  iodide  solution. 
It  boils  at  72-3°  and  has  the  sp.  gr.  1-944  (at  14°)  ;  it  is  highly  refractive  and  dissolves  in 
alcohol  or  ether.  It  decomposes  when  heated  with  water  at  100°.  Chlorine  converts  it 
into  ethyl  chloride  and  bromine  into  ethyl  bromide.  In  the  light  it  slowly  decomposes 
with  separation  of  iodine,  which  colours  the  liquid  brown,  but  it  remains  colourless  in 
presence  of  a  drop  of  mercury.  It  is  used  as  an  inhalation  for  the  treatment  of  asthma. 
It  costs  about  28s.  to  32s.  per  kilo. 

ETHYL  FLUORIDE,  C2H5F,  is  liquid  at  -48°,  burns  with  a  blue  flame,  and  does  not 
attack  glass. 

From  PROPANE  two  series  of  isomeric  compounds  are  derived:  CH3 •  CH2 •  CH2X, 
prepared  from  normal  propyl  alcohol,  and  CH2-CHX-CH3,  derived  from  isopropyl  alcohol, 
and  hence  from  acetone. 

ISOPROPYL  IODIDE  (Iodo-2-propane),  CH3-CHI.CH3,  is  obtained  from  glycerol, 
phosphorus  and  iodine,  small  amounts  of  allyl  iodide  and  propylene  being  also  formed. 

The  butyl  compounds  occur  in  four  isomeric  modifications  : 

NORMAL  BUTYL  IODIDE  (Iodo-i-butane),  CH3 - CH2 - CH2 - CH2I. 

SECONDARY  BUTYL  IODIDE  (Iodo-2-butane),  CH3 .  CH2  -  CHI  -  CH3. 

ISOBUTYL  IODIDE  (Methyl-2-iodo-3-propane),  ^3>CH-CHI. 

/-ITT 

TERTIARY  BUTYL   IODIDE  (Methyl-2-iodo-2-propane),  CH3>CI-CH3. 

The  constitutions  of  the  four  isomerides  are  deduced  from  those  of  the  corresponding 
butyl  alcohols  from  which  they  are  obtained  by  the  action  of  hydriodic  acid. 
Of  the  AMYL  derivatives  eight  isomerides  are  known. 

ii  7 


98  ORGANIC    CHEMISTRY 

METHYLENE  CHLORIDE  (Dichloromethane),  CH2C12,  bromide  and  iodide  (see 
Table,  p.  95). 

ETHYLENE  COMPOUNDS,  CH2X-CH2X,  are  formed  from  ethylene  by  the  addition 
of  halogens  or  from  glycol,  C2H4(OH)2  and  halogen  hydracids. 

ETHYLIDENE  (or  Ethydene)COMPOUNDS,  CH3  •  CHX2,  are  obtained  by  substituting 
the  oxygen  of  the  aldehydes  by  halogens. 

ETHYLENE  CHLORIDE  (Dichloro-i  :  2-ethane),  CH2C1-CH2C1  (Dutch  liquid),  boils 
at  84°.  The  IODIDE,  BROMIDE,  and  CHLORIDE  with  alcoholic  potaeh  give  acetylene 
and  glycol. 

ETHYLIDENE  CHLORIDE  (Ethydene  chloride  or  Dichloro-i  :  i -ethane), 
CH3.CHC12,  is  obtained  from  aldehyde  and  phosgene:  CH3-CHO  +  COCJ2  =  C02  + 
CH3-CHC12,  chloral  (which  see)  being  also  formed  ;  it  boils  at  57°. 

CHLOROFORM  (Trichloromethane),  CHC13.  Chloroform  was  discovered 
by  Liebig  and  Souberain  and  its  constitution  shown  by  Liebig  in  1835. 

It  is  prepared  from  (1)  ethyl  alcohol  or  (2)  acetone,  by  heating  with  chloride 
of  lime  and  water :  (1)  4C2H6OH  +  16CaOCl2  =  3H2Ca04Ca  (calcium 
formate)  +  13CaCl2  +  8H20  +  2CHC13  ;  in  this  reaction  there  is  always  an 
appreciable  evolution  of  C02,  which  appears  to  originate  in  the  oxidation 
of  the  alcohol,  and  liberates  HC10  and  so  forms  aldehyde  and  hence  chloral, 
this,  in  presence  of  lime,  yielding  chloroform  :  3C2H5OH  +  8Ca(OCl)2  = 
2CHC13  +  3CaC03  +  C02  +  8H20  +  5CaCl2. 

(2)  2CH3-CO-CH3  +  3Ca(OCl)2  =  2CH3-CO-CC13  (trichloro-acetone) 
+  3Ca(OH)3;  2CH3-CO-CC13  +  Ca(OH)2  =  Ca(C2H3O2)2  (calcium  acetate) 
+  2CHC13. 

In  a  very  pure  form  for  pharmaceutical  use  it  is  obtained  by  treating 
chloral  with  aqueous  caustic  soda  solution,  sodium  formate  being  also  formed  : 

/H 
CC13  •  C(      +  NaOH  =  CHC13  +  H  •  C02Na. 

%0 

Chloroform  can  also  be  obtained  industrially  by  reducing  carbon  tetra- 
chloride  with  hydrogen  in  the  hot  :  CC14  +  H2  =  HC1  +  CHC13  ;  the  hydrogen 
necessary  to  treat  75  kilos  of  CC14  is  given  by  60  kilos  of  HC1  at  22°  Baume 
and  50  kilos  of  zinc. 

To  obtain  very  pure  chloroform  from  the  impure  product,  Anschtitz  treats 
the  latter  with  salicylic  anhydride,  C6H4C02,  which  forms  a  crystalline  mass 
only  with  chloroform,  (C6H4C02)4,  2CHC13  ;  this,  after  separation  from  the 
mother-liquor,  is  heated  on  the  water-bath,  when  pure  chloroform  distils  off. 

It  is  a  colourless  liquid  with  a  sweet  ethereal  smell  and  taste  ;  it  dissolves 
only  to  a  slight  extent  in  water  (0-7  per  cent.),  but  is  soluble  in  alcohol  or 
ether.  It  boils  at  61-2°,  and  its  vapour  pressure  at  20°  is  160  mm.  of  mercury ; 
its  specific  gravity  is  1-5263  at  0°  and  1-500  at  15°,  referred  to  water  at  4°. 

It  is  non-inflammable,  and  it  dissolves  resins,  rubber,  fats,  and  iodine, 
with  the  last  of  which  it  gives  violet  solutions. 

Exposed  to  light  and  air,  it  decomposes  partially  into  Cl,  HC1,  and  COC12, 
but  it  can  be  kept  in  yellow  bottles,  while  that  for  pharmaceutical  use  keeps 
better  if  1  per  cent,  of  absolute  alcohol  is  added. 

It  is  the  most  efficacious  anesthetic  (Simpson,  1848),  but  in  some  cases 
may  cause  death  if  not  used  with  great  care,  since  it  acts  on  the  heart  ;  to 
diminish  this  effect,  it  is  mixed  with  atropine  or  morphine.1 

1  From  coal-tar  products  various  anaesthetics  or  hypnotics  are  produced  synthetically,  and  these  have  been 
of  great  service  to  medicine,  especially  to  surgery,  rendering  possible  the  execution  of  the  most  complicated  opera- 
tions without  any  pain  to  the  patient.  At  first  substances  were  used  which  produced  general  ancesthesia  of  the 
organism,  but  they  were  accompanied  by  many  inconveniences,  sometimes  by  fatal  results. 

Indeed,  the  anaesthetic  is  transported  by  the  blood  into  contact  with  the  higher  nervous  centres  by  which 
pain  is  felt,  producing  poisoning  and  paralysis  of  them  often  lasting  for  some  time  ;  at  the  same  time  an  influence 
is  felt  by  the  centres  controlling  the  action  of  the  heart  and  of  respiration,  this  being  the  cause  of  the  danger  and 
disturbance  produced  by  general  anaesthesia.  The  nerve-currents  start  from  the  periphery,  from  the  points  where 
the  surgical  operation  is  to  begin,  and  are  transmitted  to  the  brain,  which  transforms  them  into  painful  sensations, 


MANUFACTURE  OF  CHLOROFORM     93 

In  America,  chloroform  is  used  to  render  pigs  insensible  so  as  to  kill  them 
painlessly  and  to  skin  them  more  easily.  Also,  in  fattening  them,  they  are 
subjected  to  periodic  inhalations  of  chloroform,  which  renders  them  more 
restful. 

Chromic  acid  transforms  chloroform  into  phosgene  (COC12),  whilst  potassium 
amalgam  gives  acetylene.  With  potassium  hydroxide,  it  gives  potassium 
formate  and  chloride  : 


CHC1 


H-C02K 


2H20. 


FIG.  102. 


3       4KOH  =  3KC1 
With  ammonia  at  a  red  heat,  it  gives  hydrocyanic  and  hydrochloric  acids  : 
CHC13  +  NH3  =  HCN  +  3HC1. 

Pictet  Chloroform  is  pure  chloroform  obtained  from  the  commercial 
product  by  freezing  it  at  -80°  to  -120°  ;  the  impurities  remain  in  the 
liquid,  the  crystals  giving  pure  chloro- 
form. 

INDUSTRIAL   PREPARATION.      A 

considerable  amount  of  chloroform  is  pre- 

pared even  to-day  from  chloride  of  lime 

and   alcohol,  but   the    latter   should   not 

contain  fusel  oil.     The  reaction  takes  place 

in  a  double  -bottomed  iron  boiler,  A  (Fig. 

102),  which  contains  a  mechanical  stirrer, 

M,  and  into  which  the  chloride   of  lime, 

water,  and  alcohol  are  introduced  through 

a  large  aperture,  F,  at  the  top.     The  heat- 

ing is  effected  by  a  steam-coil,  Pp,   and 

cold  water  can  be  circulated  through  the 

jacketed    bottom,     when     necessary,     by 

means  of    another  pipe  not  shown  in  the 

figure.      To  produce  100  kilos    of    chloro- 

form 100  kilos  of  alcohol  and  1300  kilos 

of  chloride  of  lime  (with  36  per  cent.  Cl) 

are  actually  used  ;  but  in  practice  a  large  excess  of  alcohol  —  about  ten  times  that  really 

required  by  the  reaction  —  is  employed,  but  the  excess  is  used  up,  since  it  is  added  all  at 

once  and  the  process  then  continued  by  gradually  replacing  the  quantity  that  reacts. 

An  apparatus  for  producing  125  kilos  of  chloroform  daily  —  with  four  charges  of  the 
apparatus  in  24  hours  —  is  charged  first  of  all  with  300  kilos  of  alcohol  (96  per  cent.)  and 
1300  litres  of  water,  400  kilos  of  chloride  of  lime  being  then  added,  in  small  quantities  and 
with  constant  stirring  ;  the  aperture  F  is  then  covered  and  the  temperature  raised  to 
40°  by  steam  -heating.  The  steam  is  then  shut  off  and  the  stirring  continued  until  the 
temperature  rises  spontaneously  to  60°  (if  this  is  exceeded,  cold  water  is  passed  through 
the  jacket).  The  mixing  is  then  stopped  and  the  chloroform,  mixed  with  a  little  alcohol, 
begins  to  distil.  The  vapours  are  cooled  and  condensed  in  a  coil,  Z,  placed  in  the  lank,  K, 
through  which  cold  water  circulates  from  V  to  ms.  The  mixed  chloroform  and  alcohol 
is  collected  in  a  reservoir,  L,  with  a  graduated  standpipe.  When  about  30  kilos  of 
chloroform  have  distilled  over,  the  stirrer  is  started  again,  and  a  little  of  the  distillate 

and  it  is  by  influencing  the  cerebral  centres  by  anaesthetics  that  pain  is  avoided  ;  but  anaesthesia  ceases  to  be 
dangerous  if  the  peripheral  nervous  centres  at  the  beginning  of  the  nerve-currents  are  paralysed  without  the  latter 
reaching  the  brain.  Thus  local  anaesthesia  is  much  more  rational  and  less  dangerous,  since  the  insensibility  extends 
only  to  one  organ  or  one  region  of  the  subject  of  the  .operation. 

So  that,  to  chloroform,  ether,  &c.,  was  added,  in  1885,  cocaine,  which  paralyses  only  the  sensitive  peripheral 
nerves  without  influencing  the  motor  nerves.  By  studying  anaesthetic  and  hypnotic  substances  chemists  were 
able  to  determine  what  specific  atomic  groups  produced  anaesthetic  properties  in  a  molecule.  Thus,  with  many 
of  these  substances,  it  was  found  to  be  the  hydroxyl  group  which  induced  sleep,  especially  when  it  is  united  to 
carbon  joined  at  the  same  time  to  several  alkyl  groups  ;  replacement  of  the  hydroxyl  by  other  groups  resulted  in 
the  disappearance  of  the  anaesthetic  properties.  Also  various  amino-acid  gioups,  under  certain  definite  condi- 
tions, give  rise  to  anaesthetics.  To  enumerate  all  the  members  of  the  vast  group  of  anaesthetics  which  chemistry 
has  placed  at  the  disposal  of  surgery  would  be  out  of  place  here,  but  the  following  few  examples  may  be  mentioned  : 
a-eucaine,  ^-eucaint,  orthoform,  alipine,  holocaine,  and,  on  the  other  band,  ttUphonal,  trional,  dormiol,  hedonal, 
Veronal,  &c.  Other  properties  of  anaesthetics  are  described  in  Part  III,  in  the  section  on  alkaloids. 


100 

collected  from  time  to  time  from  the  tap,  y,  at  the  bottom  of  the  condensing  coil ;  when 
the  addition  of  water  to  this  no  longer  causes  separation  of  chloroform  at  the  bottom  of 
the  liquid,  the  remainder  of  the  distillate  obtained — finally  the  contents  of  the  boiler 
are  again  heated  with  steam — is  collected  at  y,  communication  with  the  reservoir,  L, 
being  shut  off  and  the  tap,  O,  closed.  More  or  less  dilute  alcohol  now  distils  over 
and  the  distillation  is  stopped  when  the  distillate  contains  less  than  2  to  2ij  per  cent,  of 
alcohol. 

The  total  amount  of  alcohol  (usually  260-265  kilos)  in  the  alcoholic  distillate  (500-600 
litres)  is  determined,  and  sufficient  pure  alcohol  added  to  bring  the  total  quantity  up  to 
300  kilos  ;  this  dilute  solution  serves  for  the  next  operation,  allowance  being  made  for 
the  water  it  contains.  In  this  way  the  loss  of  alcohol  is  small. 

The  crude  chloroform  is  washed  and  agitated  with  water  (30  litres  per  100  kilos)  to 
remove  the  alcohol  present,  or,  better,  with  lime-water  or  a  weak  soda  solution,  which 
removes  also  the  small  quantity  of  HC1  that  always  forms.  Finally,  the  liquid  is  agitated 
with  concentrated  sulphuric  acid,  thoroughly  rewa?hed  with  water,  dried  over  CaCl2  and 
redistilled,  the  chloroform,  passing  over  at  62-63°,  being  collected.  Instead  of  alcohol, 
acetone  is  used  by  some  manufacturers  when  it  can  be  bought  cheaply,  and  in  that 
case  100  kilos  of  acetone  yields  up  to  170  kilos  of  chloroform.  According  to  Ger.  Pat. 
129,237,  a  good  yield  and  continuous  formation  of  chloroform  are  obtained  by  heating,  in 
a  vessel  divided  into  a  number  of  cells  communicating  at  the  bottom,  alcohol  (35°  Be.) 
which  has  been  previously  chlorinated  by  means  of  chloride  of  lime  and  alkali  in  the  hot. 

During  recent  years  the  industrial  preparation  of  chloroform  has  again  been  attempted 
by  electrolysing  an  aqueous  solution  of  KC1  (20  per  cent.)  into  which  alcohol  or  acetone 
is  slowly  introduced.  In  this  process  1  h.p.-hour  is  consumed  to  produce  40  grms.  of 
chloroform. 

Erlworthy  and  Lange  (Fr,  Pat.  354,291,  1905)  propose  to  produce  chloroform  from 
methane  and  chlorine  diluted  with  indifferent  gases  (N,  C02)  by  subjecting  the  mixture 
to  the  action  of  light  in  suitable  retorts  :  CH4  +  6C1  =  3HC1  +  CHC13. 

TESTS  FOR  CHLOROFORM.  Minute  quantities  of  chloroform  can  be  detected 
by  gently  heating  a  little  of  the  liquid  with  a  few  drops  of  aniline  and  of  alcoholic  potash 
solution,  the  characteristic  repulsive  odour  of  phenylcarbylamine  (phenyl  isocyanide) 
being  formed.  Pure  chloroform  for  medicinal  use  should  not  be  acid  or  give  a  precipitate 
with  silver  nitrate  solution  or  redden  potassium  iodide  solution  ;  on  evaporation  it  should 
not  leave  a  residue  of  water  or  odorous  substances,  and  it  should  not  darken  with 
concentrated  sulphuric  acid.  To  test  for  the  presence  in  it  of  carbon  tetrachloride,  20  c.c. 
are  treated  with  a  solution  of  3  drops  of  aniline  in  5  c.c.  of  benzene  ;  a  turbidity  or  separa- 
tion of  crystals  of  phenylurea  indicates  with  certainty  the  presence  of  the  tetrachloride. 
To  ascertain  if  it  contains  alcohol  it  is  treated  with  a  very  dilute  potassium  permanganate 
solution,  which  is  decolorised  in  presence  of  this  impurity. 

Its  estimation  is  effected  by  treating  a  given  weight  with  Fehling's  solution  (see  under 
Sugar  Analysis)  and  heating  the  mixture  in  a  closed  bottle  on  a  water-bath  for  some  hours 
(until  the  odour  of  chloroform  disappears)  ;  the  cuprous  oxide,  formed  according  to  the 
equation  CHC13  +  2CuO  +  5KOH  =  K2CO3  +  3H2O  +  3KC1  +  Cu2O,  being  weighed.  One 
molecule  of  chloroform  corresponds  with  2  atoms  of  copper. 

It  can  also  be  determined  by  heating  with  alcoholic  potash  in  a  reflux  apparatus  on 
the  water-bath  ;  it  is  then  diluted  with  water,  the  alcohol  distilled  off,  and  the  potassium 
chloride  formed  (together  with  potassium  formate,  see  preceding  page)  titrated  with  a 
standard  silver  nitrate  solution.  This  method  serves  for  the  estimation  of  all  alkyl-halogen 
compounds. 

The  price  of  industrial  chloroform  is  about  £8  per  100  kilos  ;  redistilled  costs  2s.  Wd. 
per  kilo  ;  the  pharmacopceial  preparation  2s.  2d.  ;  puriss.  from  chloral,  6s.  5d.  to  9s.  Id.  ; 
Pictet's,  12s.  per  kilo,  and  that  of  Anschiitz  Wd.  per  50  grms.  Part  of  the  chloroform 
consumed  in  Italy  is  imported  from  abroad  ;  in  1906  this  amounted  to  12,200  kilos  ;  in 
1907,  10,100  ;  in  1908,  7000  ;  and  in  1909,  9000  kilos -of  the  value  £680. 

IODOFORM  (Tri-iodomethane),  CHI3,  was  discovered  by  Serullas  in  1822, 
and  its  constitution  was  established  by  Dumas  who,  unlike  his  predecessors, 
did  not  overlook  the  very  small  proportion  of  hydrogen  (0-25  per  cent.) 
present. 


IODOFORM 


It  is  formed  by  heating  ethyl  alcohol  or  acetone  with  iodine  and  sufficient 
alkali  hydroxide  or  carbonate  to  decolorise  the  iodine  (Lieberis  reaction) : 

C2H5OH  +  81  +  6KOH  =  CHI3  +  H-COOK  +  5KI  +  5H20. 

This  reaction  (separation  of  yellow  crystals  and  formation  of  a  character- 
istic odour)  is  so  sensitive  that  it  serves  for  the  detection  of  minute  traces 
(1  :  2000)  of  ethyl  alcohol  or  acetone  in  other  liquids  (waiting  12  hours 
for  the  separation  of  crystals  if  the  amount  of  alcohol  is  small)  ;  the  same 
reaction  is,  however,  given  by  isopropyl  alcohol,  acetaldehyde  (and  by  almost 
all  compounds  containing  the  group  CH3-CO-),  but  not  by  methyl  alcohol, 
ether,  or  acetic  acid. 

For  the  practical  preparation  of  iodoform  32  parts  of  K2CO3  are  dissolved  in  80  parts 
of  water  and  16  parts  of  alcohol,  the  mixture  being  heated  to  70°  and  32  parts  of  iodine 
gradually  added.  The  separated  iodoform  is  filtered  off  and  the  iodine  of  the  potassium 
iodide  in  the  nitrate  utilised  as  follows  :  20  parts  of  HC1  are  added  and  2-3  parts  of 
potassium  dichromate,  the  liquid  being  then  neutralised  with  K2CO3,  mixed  with  a  further 
32  parts  of  K2CO3, 16  parts  of  alcohol  and  6  parts  of  iodine.  On  heating,  a  second  quantity 
of  iodoform  separates,  and  after  this  or  another  similar  operation  the  mother -liquor  is 
treated  to  recover  the  iodine  from  the  potassium  iodide. 

It  has  been  proposed  to  prepare  iodoform  by  treating  the  metallic  acetylides  (see 
p.  91 )  with  iodine  and  caustic  soda. 

It  seems  that  practical  use  is  now  made  of  the  old  electrolytic  process,  using  a  bath 
of  6  parts  KI,  2  parts  soda,  8  vols.  alcohol,  and  40  of  water  at  60-65°.  The  iodine  to  be 
used  in  the  reaction  is  set  free  at  the  anode  and  to  avoid  the  formation  of  a  little  iodate 
with  the  KOH  formed  at  the  cathode  the  latter  is  enclosed  in  parchment  paper. 

When  pure,  iodoform  crystallises  in  hexagonal,  yellow  plates  (sp.  gr.  2), 
insoluble  in  water  but  soluble  in  alcohol  or  ether.  It  has  a  penetrating  and 
persistent  odour, '  recalling  partly  that  of  saffron  and  partly  that  of  phenol. 
It  melts  at  119°,  readily  sublimes,  and  is  volatile  in  steam.  On  heating  with 
either  alcohol  or  reducing  agents,  it  gives  methyleiie  iodide. 

It  is  used  in  surgery  as  an  important  antiseptic,  which,  however,  acts 
indirectly  on  bacteria  by  means  of  the  decomposition  products  formed  from 
it  under  the  action  of  the  pus  of  wounds  or  of  the  heat  of  the  body. 

Owing  to  its  disagreeable  odour,  it  has  been  to  some  extent  replaced  latterly 
by  Xeroform,  which  is  a  tribromophenoxide  of  bismuth,  C6H2Br30  •  OH,  Bi202, 
obtained  by  the  action  of  bismuth  chloride  on  sodium  tribromophenoxide  and 
forming  a  tasteless,  odourless,  yellow  powder  insoluble  in  water  or  alcohol  ; 
it  is  used  also  as  a  disinfectant  for  the  intestines,  and  costs  44s.  to  48s.  per 
kilo,  whilst  iodoform  costs  only  24s.  to  28s.  a  kilo. 

TESTS  FOR  IODOFORM.  It  should  leave  no  residue  on  sublimation  and  should 
dissolve  completely  in  alcohol  or  ether.  It  is  estimated  by  heating  about  1  grm.  with 
about  2  grms.  of  silver  nitrate  and  25  c.c.  of  concentrated  nitric  acid  (free  from  chlorine) 
in  a  reflux  apparatus  so  that  the  liquid  does  not  boil  ;  when  the  nitrous  vapours  have 
disappeared  the  liquid  is  diluted  with  water  to  150  c.c.  and  heated,  the  silver  iodide  being 
collected  on  a  tared  filter,  dried  and  weighed  :  1-789  grm.  Agl  corresponds  with  1  grm. 
iodoform. 

CARBON  TETRACHLORIDE  (Tetrachloromethane),  CC14  (see  vol.  i,  p.  378). 

POLYCHLORO-DERIVATIVES  OF  ETHYLENE  AND  ETHANE.1  Asymm. 
HEPTACHLOROPROPANE  was  prepared  in  1910  by  Boeseken  and  Prins  from  tetra- 
chloroethylene  and  chloroform  in  presence  of  aluminium  chloride  as  catalyst. 

1  Since  1908  (Ger.  Pats.  196,324,  204,516,  204,883,  &c.),  the  Chemische  Fabrik  Griesheim-Elektron  of  Frankfort, 
and  the  Usines  electriques  de  la  Lonia  of  Geneva  have  placed  on  the  market,  as  non-inflammable  solvents  for 
industrial  purposes,  six  chlorinated  compounds  obtained  as  colourless  liquids  by  the  action  of  chlorine  on  acetylene. 
They  are  all  good  solvents  for  fats,  resins,  rubber,  &c.,  and  can  replace  advantageously  benzene,  carbon  disulphide, 
and  alcohol,  since  they  are  not  inflammable  and  their  vapours  do  not  form  explosive  mixtures  with  air ;  ovci 


;  102 


r.$>Jf.GANIC    CHEMISTRY 

1  *f»    »  '  C    r" 


II.  HALOGENATED  DERIVATIVES  OF  UNSATURATED 
HYDROCARBONS 

These  are  obtained  from  saturated  halogen  derivatives  by  partial  elimination  of  the 
halogen  hydracid  :  C2H4Br2  =  HBr  +  C2H3Br.  They  are  formed  by  incomplete  satura- 
tion, with  halogens  or  halogen  hydracids,  of  the  less  saturated  hydrocarbons : 
C2H2  +  HBr  =  C2H3Br  (see  Table  in  footnote). 

The  allyl  compounds,  C3H5X,  are  formed  from  allyl  alcohol  by  the  action  of  halogen 
hydracid  or  of  phosphorus  and  halogen. 

ALLYL  CHLORIDE  (Chloro-3-propene-i),  CH2  :  CH.CH2C1,  the  bromide  and  iodide 
having  analogous  constitutions. 

They  are  related  to  the  natural  allyl  compounds  (garlic  oil  and  mustard  oil).  Two 
stereoisomerides  are  known  : 

H— C— Cl  H— C— Cl 

a-chloropropylene,  and  iso-a-chloropropylene, 

H — C — CHa  CH3 — C — H 


CC.  ALCOHOLS 

These  form  an  important  group  of  organic  compounds  containing  one  or 
more  characteristic  hydroxyls,  the  hydrogen  of  which  has  pronounced  reactive 
properties,  so  that  numerous  series  of  other  compounds  are  derived  from  the 
alcohols.  They  have  a  neutral  reaction,  although  their  chemical  behaviour 
is  analogous  to  that  of  the  inorganic  bases  which  always  contain  the  anion 
OH'.  The  majority  of  these  alcohols  are  colourless  liquids,  but  those  of 
high  molecular  weights  are  oily,  solid,  and  sometimes  of  a  yellowish  colour. 
The  first  members  of  the  series  are  soluble  in  water,  but  with  increase  of 
molecular  weight  the  solubility  decreases  and  the  smell,  generally  slight,  also 
tends  to  disappear.  They  are  often  found  in  nature  either  free  or  combined 
with  organic  acids,  in  the  fats,  waxes,  fruits,  essential  oils,  &c. 

According  to  the  number  of  hydroxyl  groups  they  contain,  they  are  divided 
into  mono-,  di-,  .  .  .  polyhydric  alcohols,  and  may  belong  either  to  the  satu- 
rated or  to  the  unsaturated  series — already  studied  in  connection  with  the 
hydrocarbons — of  which  they  retain  the  fundamental  characters  ;  added  to 
the  latter  are  those  characteristic  of  the  alcoholic  group,  which  we  shall  study 
generally  with  the  monohydric  alcohols. 

carbon  tetrachloride  they  have  the  advantage  of  not  attacking  the  metal  parts  of  the  extraction  apparatus,  and  the 
loss  on  extraction  varies  from  0-3  to  0-8  per  cent. ;  they  are,  however,  dearer  than  the  ordinary  solvents  and  seem 
to  be  injurious  to  health.  The  properties  of  these  compounds  are  given  in  the  following  Table  : 


DlCHLORO- 

TRICHLORO- 

TETRA- 

TETRA- 

PENTA- 

HEXA- 

ETHYLENE 

ETHYLENE 

CHLORO- 

CHLORO- 

CHLORO- 

CHIORO- 

ETHYLENE 

ETHANE 

ETHANE 

ETHANE 

C,H2C1, 

CjHCl, 

C2C14 

CjH^Cli 

CjHCl6 

C2C1. 

Common  name 

Didine 

Trieline 

EtUine 

Tetraline 

Pentaline 

— 

Specific  gravity     . 

1-278 

1-471 

1-628 

1-600 

1-685 

2 

Boiling-point 

52° 

85° 

119° 

144* 

159° 

(185') 

Vapour  pressure  at  20° 

205  mm. 

56 

17 

11 

7 

3 

Specific  heat  at  18° 

0-270 

0-233 

0-208 

0-227 

0-207 

.  

Heat  of  evaporation 

41  cals. 

57-8 

50 

52-8 

45 

— 

Freesing-point 

— 

-70° 

— 

—  30° 

— 

— 

Uses  and  properties 

Readily  dis- 

Dissolves 

Serves  well 

Dissolves 

Readily  dis- 

Has   an 

solves     rub- 

fats,   paraf- 

for   remov- 

resins    and 

solves  cellu- 

odour    like 

ber 

fin,  and  va- 

ing spots 

varnishes, 

lose  acetate 

camphor, 

seline  hotter 

like  turpen- 

for  artificial 

and     serves 

than      ben- 

tine  and  al- 

silk    and 

as  an  insec- 

«'ne 

cohol  and  dissolves  cellu- 

cinemato- 

ticide 

lose  acetate  for  films  and 

graph  films 

artificial  silk 

MONOHYDRIC    ALCOHOLS  103 

I.  SATURATED  MONOHYDRIC  ALCOHOLS 

The  specific  gravity  of  these  is  always  lower  than  that  of  water  and  up  to 
the  C16  member  they  distil  unchanged  at  the  ordinary  pressure  ;  beyond  that 
reduced  pressure  must  be  employed. 

That  alcohols  always  contain  a  hydroxyl  group  OH  can  be  shown  by  the  following 
chemical  reactions : 

The  alcohols  can  be  obtained  by  the  action  of  silver  hydroxide,  AG-OH  (which  cer- 
tainly contains  the  group  OH),  or  even  of  the  alkalis  or  hot  water,  on  halogenated  hydro- 
carbons :  CwH2n+1I  +  AgOH  =  Agl  +  CreH2w+1OH. 

With  the  halogen  hydracids  the  hydroxyl  separates  from  the  alcohols  in  the  form  of 
water  :  CreH2n+1OH  +  HBr  =  H20  +  CnH2w+1Br  ;  and  the  same  happens  with  oxy- 
acids,  the  so-called  esters  being  formed  :  CnH2w+1OH  +  HN03  =  H20  +  CnH2n+1NO3. 
Just  as  sodium  and  potassium  react  with  water,  liberating  hydrogen,  so  do  they  act 
on  the  alcohols,  from  which  only  the  typical  hydrogen  (hydroxylic),  not  united  directly 
to  carbon,  is  eliminated :  CnH2n+1OH  +  Na  =  CnH2n+1ONa  (sodium  alkoxide)  +  H. 
Magnesium  alkoxides  are  also  easily  obtained.  With  phosphorus  trichloride,  however, 
the  hydroxyl  group  is  eliminated  : 

3CnH2n+1OH  +  PC13  =  3CnH2n+1Cl  =  P(OH)8. 

On  p.  16  the  difference  in  constitution  between  ethyl  alcohol  and  methyl  ether  has 
been  demonstrated. 

If  the  hydroxyl  group  occurs  in  place  of  a  hydrogen  atom  in  the  methyl  group 
( — CH3)  at  the  extremity  of  the  hydrocarbon  chain,  the  primary  alcohols  are  obtained, 

/  ^    z  \ 

all  containing  the  characteristic  group  — CH2-OH  (i.e.  — Cf          1,  e.g.  propyl  alcohol, 

CH3  •  CH2  •  CH2  •  OH,  and  by  oxidation  of  these  alcohols  are  formed  first  aldehydes  with 
the  characteristic  group  (  X — G'f      ),  and  then  acids  with  the  characteristic  carboxyl 


group  — COOH  (i.e.  — Cf         ).     Substitution  of  a  hydroxyl  for  a  hydrogen  atom  in  an 


intermediate  methylene  group  ( =  CH2)ln  the  saturated  hydrocarbon  chain  yields  secondary 
alcohols,  which  have  the  characteristic  group  ^>CH-OH  (i.e.  ^>C<^QTT)  and  on  oxidation 

give  ketones  containing  the  special  group  ^>CO.  Finally  the  substitution  of  the  hydrogen 
of  a  branched  hydrocarbon  may  take  place  in  the  methinic  group  (=CH),  giving  tertiary 
alcohols  with  the  characteristic  grouping  =C-OH,  the  other  three  valencies  of  the  carbon 
being  united  to  three  carbon  atoms.  When  the  secondary  alcohols  are  oxidised  they 
cannot  give  either  acids  or  ketones  with  an  equal  number  of  carbon  atoms,  but,  if  the 
oxidation  is  energetic,  the  chain  breaks,  and  then  acids  and  ketones  may  be  formed,  but 
with  less  numbers  of  carbon  atoms. 

According  to  B.  Neave  (1909),  primary,  secondary,  and  tertiary  alcohols 
can  be  distinguished  by  the  Sabatier  and  Senderens  reaction  (see  p.  34),  by 
passing  the  vapours  of  the  alcohol  over  finely  divided  copper  heated  at  300°  ; 
the  primary  alcohols  form  hydrogen  and  aldehydes  (recognisable  by  Schiff  s 
reaction  ;  see  section  on  Aldehydes),  the  secondary  ones  give  hydrogen  and 
ketones  (detectable  by  semicarbazide  hydrochloride  solution)  and  the  tertiary 
alcohols  give  water  and  unsaturated  hydrocarbons  (which  decolorise  bromine 
water). 

The  primary  alcohols  and  the  corresponding  ethers  have  the  highest  boiling- 
points,  the  tertiary  ones  and,  in  general,  those  with  branched  chains  showing 
the  lowest  boiling-points. 

In  the  group  of  alcohols  the  isomerism  and  the  number  of  isomerides  are 


104  O  R  GA  N.I  C    CHEMISTRY 

similar  to  those  of  the  halogenated  derivatives  of  the  hydrocarbons,  since  the 
halogen  atom  is  here  replaced  by  a  hydroxyl  group.  * 

The  names  of  the  primary  alcohols  are  made  from  those  of  the  corresponding  hydro- 
carbons (see  p.  31)  with  the  termination  ol,  and  those  of  the  secondary  and  tertiary 
alcohols  are  derived  from  the  names  of  the  hydrocarbons  with  the  longest  non-branched 
chains  ;  or  the  secondary  and  tertiary  alcohols  may  be  regarded  as  derivatives  of  methyl 
alcohol  or  carbinol,  CH3  •  OH,  formed  by  substitution  of  the  hydrogen  atoms  of  the  methyl 
group.  We  have,  hence,  two  different,  but  still  equally  clear,  systems  of  nomenclature. 
For  example  : 

(1)  Normal  butyl  alcohol:  CH3 •  CH2 •  CH2 •  CH2 •  OH  =  butan-1-ol  or  n-propylcarbinol. 

2          1 

(2)  Secondary  butyl   alcohol:    CH3.CH2-CH(OH).CH3  =  butan-2-ol  or  methylethyl- 
carbinol.  2  l 

123 

(3)  Isobutyl  alcohol:   CH3 •  CH •  CH2 •  OH  =  2-methylpropan-3-ol  or  isopropylcarbinol. 


CH, 


1  23 

(4)  Tertiary  butyl  alcohol :  CH3 — C — CH3  =  2-methylpropan-2-ol  or  trimethylcarbinol. 


CH3     OH 

PROCESSES  OF  FORMATION  OF  MONOHYDRIC    ALCOHOLS.      As 

well  as  from  the  halogen  derivatives,  the  alcohols  can  usually  be  obtained  by 
decomposing  esters  with  acids,  alkalis,  or  superheated  water.  This  reaction 
is  termed  saponification  or  hydrolysis  : 

C2H50-N02  +  KOH  -  KN03  +  C2H5-OH. 

Tn  a  general  way,  the  primary  alcohols  are  formed  by  reducing  the  acids 
(CnH2n02)  or  aldehydes  (CnHowO)  with  nascent  hydrogen  : 

7° 
CH3  •  CC      (acetaldehyde)  +  2H  =  CH3  •  CH2  •  OH. 

H 

Since  the  acids,  in  their  turn,  can  be  prepared  from  the  alcohols  with  one 
carbon  atom  less,  we  have  at  our  disposal  a  general  reaction  for  preparing 
synthetically  any  higher  alcohol. 

The  secondary  alcohols  are  formed  by  reducing  the  ketones,'CwH2W0,  e.g.  : 

CH3  •  CO  •  CH3  +  H2      =      CH3  •  CH(OH)  •  CH3 

Acetone  Isopropyl  alcohol 

(see  later,  Aldehydes  and  Ketones). 

The  tertiary  alcohols  are  formed  by  the  prolonged  action  of  zinc  methyl 
on  acid  chlorides,  the  intermediate  compounds  thus  formed  being  decomposed 
with  water. 

For  the  secondary  and  tertiary  alcohols  Grignard's  reaction  may  also  be 
employed  (see  later,  Alkylmetallic  Compounds). 

Of  more  industrial  importance,  however,  is  the  preparation  of  some  of  the 
more  common  of  these  alcohols  by  the  distillation  of  wood  or  the  fermentation 
of  certain  carbohydrates  (see  later). 

In  addition  to  the  properties  of  the  alcohols  given  above,  namely,  their 
behaviour  towards  acjds,  halogens  (which  oxidise  them),  chlorides,  and  oxidising 
agents  in  general  (which  give  aldehydes  and  acids),  it  may  be  mentioned  that 
the  higher  alcohols  (primary)  are  transformed  into  the  corresponding  acids 
by  simple  heating  with  soda  lime.  Traces  of  primary  alcohols  are  detectable 
by  oxidising  with  permanganate  and  sulphuric  acid  and  then  testing  for 
aldehyde  with  a  sulphurous  acid  solution  of  fuchsine. 


CONST  ANTS  OF  ALCOHOLS        105 

ft 

PHYSICAL  CONSTANTS  OF  THE  MONOHYDRIC  ALCOHOLS 


Name  and  Formula 

Specific 
gravity 

Melting- 
point 

Boiling- 
point 

1.     Methyl  alcohol,  CH3-OH 

0-812  (0°) 

-94°,  -98° 

66° 

2.     Ethyl  alcohol,  C2H6-OH 

0-806 

-112°  -117° 

78° 

3a.  Normal  propyl  alcohol  (prim.) 

CH3-CH2-CH2-OH 

0-817 

-127° 

97° 

36.  Iso  propyl  alcohol  (sec.) 

CH3-CH(OH)-CH3 

0-789  (20°) 

— 

81° 

4a.  Normal  butyl  alcohol  (prim.),  C4H9-OH    . 

0-810 

-80°(-122°) 

117° 

46.  Normal  butyl  alcohol  (sec.),  C4H9-OH 

0-808 

— 

100° 

4c.   Isobutyl  alcohol,  C4H9-  OH      .         .         ;:  . 

0-806  (20°) 

— 

107° 

4:d.  Tertiary  butyl  alcohol  (trimethylcarbinol), 

C4H9-OH 

0-786  (20°) 

+  25° 

83° 

5a.  Normal  amyl  alcohol  (prim.) 

CH3-[CH2]3-CH2-OH 

0-817  (20°) 

— 

138° 

56.  Amyl  alcohol  of  fermentation  or  isobutyl- 

carbinol,  (CH3)2CH-CH2-CH2-OH  . 

0-810  (20°) 

— 

130° 

5c.    Active  amyl  alcohol  or  sec.  butylcarbinol, 

CH3-CH(C2H5)-CH2-OH 

0-816  (20°) 

— 

128° 

5d.  Trimethyl-  or  tertiary  butyl-carbinol, 

(CH3)3C-CH2-OH 

0-812  (20°) 

49° 

113° 

5e.  Diethylcarbinol,  C2H5-CH(OH)-C2H5 

0-831  (0°) 

— 

117° 

5/.    Methylpropylcarbinol, 

CH3.[CH2]2-CH(OH)-CH3 

0-824  (0°) 

— 

119° 

5g.  Methylisopropylcarbinol, 

(CH3)2CH-CH(OH)-CH3 

0-819  (0°) 

— 

112-5° 

&h.  Dimethylethylcarbinol, 

(CH3)2C(OH).C2H5 

0-814  (15°) 

-12° 

102° 

6.  Normal  hexyl  alcohol  (prim.),  C6H13-OH    . 

0-833  (0°) 

— 

157° 

7.  Normal  heptyl  alcohol  (prim.),  C7H15-OH 

0-836 

— 

175° 

8.  Normal  octyl  alcohol  (prim.),  C8H17-OH 

0-839 

— 

191° 

9.  Normal  nonyl  alcohol,  C9H19-OH 

0-842 

—  5° 

213° 

10.  Decyl  alcohol,  C^^-OH          .          .          . 

0-839 

+  7° 

231° 

11.  Undecyl  „        CuH28-OH          .       ,  .          . 

— 

+  19° 

131°(15rrm.) 

12.  Dodecyl  „        C^H^-OH          .          . 

0-831 

24° 

143°       „ 

13.  Tridecyl  „        C^H^-OH          .          .          . 

— 

30-5° 

156°       „ 

14.  Tetradecyl  alcohol,  Ci4H29-  OH 

0-824 

38° 

167°       „ 

15.  Pentadecyl  alcohol,  C^H^-OH 

— 

45-46° 

— 

16.  Hexadecyl  (cetyl)  alcohol,  C16H33-OH 

0-818 

50° 

190°       „ 

17.  Octodecyl  alcohol,  C^H^-OH  . 

0-813 

59° 

211°       „ 

18.  Ceryl               „        C26H53-OH  .          .          . 

— 

79° 

— 

19.  Myricyl           „        C30H61-OH  . 

— 

85° 

— 

corre- 


By  the  behaviour  of  the  nitro-compounds  (prepared  from  the 
spending  iodides  and  silver  nitrite)  and  also  by  the  initial  velocity  and  degree 
of  esterification,  primary  alcohols  can  be  differentiated  from  the  secondary 
and  tertiary  ones. 

Various  primary  normal  alcohols  enter  inorganic  compounds  as  alcohol  of 
crystallisation,  e.g.  BaO,  2CH3-OH;    CaCl2,  4CH3-OH;    KOH,  2C2H5-OH 


MgCl2 


6C2H5 


OH  ;    CaCL,  4C,H5-OH,  &c.  ;   it  is  hence  evident  why  calcium 


chloride  cannot  be  used  for  drying  alcohol,  although  it  serves  well  in  the  case 
of  ether. 


106 


ORGANIC    CHEMISTRY 


METHYL  ALCOHOL,  CH3-OH  (Methanol  or  Carbinol) 

This  is  called  wood-spirit,  since  it  was  obtained  by  Boyle  in  1661  from 
wood-tar,  and  is  to-day  prepared  in  large  quantities  by  distilling  wood.  Its 
chemical  composition  was  not  determined  until  1834  (by  Dumas  and  Peligot). 

In  nature  it  occurs  in  the  form  of  its  salicylic  ester,  in  Gaultheria  pro- 
cumbens  (in  Canada)  and  as  butyric  ester  in  the  bitter  seeds  of  Heracleum 
giganteum. 

PROPERTIES.  When  pure  it  is  a  colourless  liquid,  b.pt.  66°,  with  a 
faint  alcoholic  smell ;  it  burns  with  a  non-luminous  flame,  solidifies  at  very 
low  temperatures  and  melts  at  —94°.  When  1  kilo  is  burned,  5310  cals. 
are  developed.  It  dissolves  in  all  proportions  in  water,  alcohol,  ether,  or 
chloroform.  Its  specific  gravity  at  15°  is  0-7984,  and  in  aqueous  solutions 
the  amount  of  the  alcohol  present  can  be  determined  from  the  specific  gravities.1 

Like  spirits  of  wine  (ethyl  alcohol)  it  is  intoxicating,  dissolves  fats,  oils,  &c., 
and  when  it  is  anhydrous  it  dissolves  also  calcined  copper  sulphate  forming 
a  bluish  green  solution.  Jfrn 

It  is  more  poisonous  to  the  human  organism  than  ethyl  alcohol,  since  it 
produces  fatty  degeneration  of  the  liver  and  undergoes  changes  quite  different 
from  those  of  ethyl  alcohol,  passing  only  in  minimal  quantities  into  the  urine 
and  being  mostly  oxidised  in  the  organism. 

When  heated  with  soda  lime  or  with  oxidising  agents  it  readily  yields 
formaldehyde  and  formic  acid,  and  sometimes  carbon  dioxide  ;r[when  distilled 
with  zinc  dust  it  gives  CO  and  H.  With  potassium  it  forms  a  crystalline 
alcoholate,  CH3-OK,  CH3-OH. 

INDUSTRIAL  PREPARATION.  In  the  laboratory  methyl  alcohol  can  be  prepared 
by  saponifying  methyl  chloride  or  iodide.  Industrially,  if  wood  is  heated  in  retorts  out 
of  contact  with  air,  after  all  the  water  has  distilled  over,  gradual  decomposition  commences 
at  150°,  and  between  150°  and  280°  acetic  acid  (about  5  per  cent,  of  the  weight  of  wood), 
acetone  (0-1  to  0-2  per  cent. ),  methyl  alcohol  (0-5  to  0-8  per  cent. ),  certain  ammonia  bases,  &c., 
distil  over  in  the  form  of  a  reddish  brown  aqueous  liquid  of  empyreumatic  odour,  termed 
wood-spirit,  and  containing  about  10  per  cent,  of  acetic  acid,  1  to  2  per  cent,  of  methyl 
alcohol  and  0-1  to  0-5  percent,  of  acetone.  Between  300°  and  400°  the  distillate  is  mainly 
black,  oily,  dense  wood-tar  (about  10  per  cent,  of  the  wood),  and  at  the  fame  time  gases 
(about  6-5  per  cent.)  are  developed  which  are  utilised  for  heating  the  retorts.  At  the 
end  of  the  distillation,  charcoal  (about  18  per  cent.)  remains  in  the  retort?.  If  the  distilla- 
tion is  rapid,  a  greater  yield  of  charcoal  is  obtained,  whilst  with  slow  heating  more 
volatile  and  liquid  products  are  obtained  and  only  9  to  10  per  cent,  of  charcoal. 

As  the  principal  product  of  the  distillation  of  wood  is  acetic  acid,  the  description  of 
the  apparatus  employed  in  this  industry  will  be  left  until  later. 


Per 

Per 

Per 

Per 

Per 

Specific 

cent,  by 

Specific 

cent,  by 

Specific 

cent,  by 

Specific 

cent,  by 

Specific 

cent,  by- 

gravity 

weight 

gravity 

weight 

gravity 

weight 

gravity 

weight 

gravity 

weight 

at  15-56" 

of 

at  15-56° 

of 

at  15-56° 

of 

at  15-56° 

of 

at  15-56° 

of 

alcohol 

alcohol 

alcohol 

alcohol 

alcohol 

0-99729 

1 

0-96524 

22 

0-93335 

42 

0-89358 

62 

0-84521 

82 

0-99554 

2  . 

0-96238 

24 

0-92975 

44 

0-88905 

64 

0-84001 

84 

0-99214 

4 

0-95949 

26 

0-92610 

46 

0-88443 

66 

0-83473 

86 

0-98893 

6 

0-95655 

28 

0-92237 

48 

0-87970 

68 

0-82938 

88 

0-98569 

8 

0-95355 

30 

0-91855 

50 

0-87487 

70 

0-82396 

90 

0-98262 

10 

0-95053 

32 

0-91465 

52 

0-87021 

72 

0-81849 

92 

0-97962 

12 

0-94732 

34 

0-91066 

54 

0-86535 

74 

0-81293 

94 

0-97668 

14 

0-94399 

36 

0-90657 

56 

0-86042 

76 

0-80731 

96 

0-97379 

16 

0-94055 

38 

0-90239 

58 

0-85542 

78 

0-80164 

98 

0-97039 

18 

0-93697 

40 

0-89798 

60 

0-85035 

80 

0-79589 

100 

0-96808 

20 

METHYL    ALCOHOL  107 

To  separate  the  methyl  alcohol  from  the  liquid  products  of  the  distillation  these  are 
subjected  to  fractional  distillation  in  copper  boilers  with  a  Pistorius  rectifier  (see  Ethyl 
Alcohol),  and  when  the  specific  gravity  of  the  distillate  has  increased  from  0-9  to  1  all 
the  methyl  alcohol  (crude  wood-spirit)  has  passed  over  and  forms  a  greenish  yellow  liquid 
with  a  disagreeable  odour.  To  eliminate  the  majority  of  the  impurities  the  liquid  is 
mixed  with  about  2  per  cent,  of  lime,  left  overnight,  and  then  distilled  with  the  Pistorius 
rectifying  apparatus,  the  acetic  acid  remaining  fixed  by  the  lime. 

The  crude  methyl  alcohol  thus  obtained  has  a  specific  gravity  of  about  0-816  (93  per 
cent.)  and  is  colourless,  but  it  turns  brown  on  standing  in  the  air  and  becomes  turbid  on 
mixing  with  water.  To  purify  it,  it  is  diluted  with  water  to  the  sp.  gr.  0-935  (about 
40  per  cent. ),  left  for  several  days,  and  after  the  superficial  tarry  layer  which  collects  has 
been  removed  it  is  treated  with  2  per  cent,  of  lime  and  distilled  almost  completely.  The 
distilled  product  is  mixed  with  0-1  to  0-2  per  cent,  of  sulphuric  acid  and  rectified,  the 
concentrated  alcohol  distilling  at  64°  to  66°,  being  collected  separately ;  this  is  used  for  many 
industrial  purposes,  although  it  contains  a  small  proportion  of  acetone.  The  latter  can 
be  removed  almost  completely  by  transforming  the  alcohol  into  an  ester  (e.g.  the  oxalate, 
by  treatment  with  concentrated  sulphuric  acid  and  potassium  dioxalate),  which  is  easily 
separated  from  the  impurities  ;  by  hydrolysing  the  ester  with  KOH,  distilling  and  rectify- 
ing, pure  methyl  alcohol  is  obtained.  The  acetone  can  also  be  got  rid  of  by  combining 
the  alcohol  with  CaCl2,  giving  the  compound  CaCl2,  4CH3-OH,  which  is  stable  at  100°, 
so  that  the  acetone  can  be  distilled  off  at  56°  together  with  the  other  impurities  ;  the 
residue  is  then  decomposed  with  water  and  the  pure  methyl  alcohol  distilled. 

To  ascertain  if  the  alcohol  still  contains  acetone,  10  c.c.  of  it  are  treated  with  caustic 
soda  and  an  aqueous  solution  of  iodine  in  potassium  iodide  ;  no  turbidity  due  to  iodoform 
should  be  formed  for  some  time.1 

According  to  Farkas's  patent  (Ger.  Pat.  166,360,  1904)  alcohol  of  92  to  95  per  cent, 
purity  is  obtained  direct  if  the  vapours  from  the  distillation  of  wood,  while  still  hot,  are 
passed  through  hot  NaOH  solution  (15°  to  20°  B6.)  and  then  into  hot  fatty  acids,rthe 
alcoholic  condensate  being  rectified  by  passing  the  vapours  into  milk  of  lime. 

USES  AND  STATISTICS.  Methyl  alcohol  is  used  for  the  manufacture 
of  formaldehyde  and  various  aniline  dyes,  for  the  preparation  of  different 
varnishes  and  for  the  denaturation  of  spirit  (ethyl  alcohol). 

1  Tests  for  Methyl  Alcohol.  When  pure  it  should  leave  no  residue  on  evaporation,  should  not  have  an 
acid  reaction  towards  litmus,  and  should  not  contain  ethyl  alcohol,  which  can  be  detected  as  follows :  a  little 
of  the  liquid  is  heated  with  sulphuric  acid,  diluted  with  water  and  distilled,  the  distillate  being  treated  with 
permanganate,  then  with  sulphuric  acid,  and  finally  with  sodium  hydrogen  sulphite ;  if  ethyl  alcohol  is  not 
present  this  liquid  will  not  give  a  violet  coloration  with  fuchsine  solution.  Acetone  and  ethyl  alcohol  can  also  be 
detected  by  the  iodoform  reaction  (Lieben's  reaction  :  see  below  and  also  p.  101).  Proportions  of  2  to  3  per  cent,  of 
methyl  alcohol  can  be  detected  by  Scudder  and  Rigg»'s  reaction  (1906),  which  consists  in  treating  10  c.c.  of  the 
liquid  at  25"  with  5  c.c.  of  concentrated  sulphuric  acid  and  5  c.c.  of  saturated  permanganate  solution,  decolorising 
(after  two  minutes)  with  sulphurous  acid  solution  and  boiling  until  all  smell  of  sulphur  dioxide  or  acetaldehyde 
disappears.  This  liquid  is  then  tested  for  formaldehyde  by  adding  a  few  centigrams  of  resorcinol  to  2  c.c. 
and  pouring  1  c.c.  of  pure  concentrated  sulphuric  acid  to  the  bottom  of  the  liquid ;  a  blue  ring,  due  to  the 
formaldehyde  formed  from  the  methyl  alcohol,  forms  at  the  surface  of  separation  of  the  two  liquids.  Deniges 
(1910)  detects  as  little  as  1  per  cent,  of  ethyl  alcohol  by  heating  the  methyl  alcohol  with  bromine  water  and 
testing  for  the  acetaldehyde  formed  with  fuchsine  solution  decolorised  with  SO,  (see  Aldehydes). 

Estimation  of  the  methyl  alcohol  in  the  commercial  product  is  effected  by  the  Krell-KrSmer  method  :  30  grms. 
of  phosphorus  tri-iodide  is  placed  in  a  flask  furnished  with  a  long  reflux  condenser,  down  which  is  poured,  drop  by 
drop,  10  c.c.  of  the'methyl  alcohol ;  after  a  short  time  the  methyl  iodide  formed  is  distilled  from  a  water-bath  into 
a  graduated  cylinder  containing  a  little  water  ;  when  the  distillation  is  completed,  the  condenser  is  rinsed  out  with 
water  and  the  volume  of  the  methyl  iodide  under  the  water  measured  at  15"  ;  5  c.c.  of  pure  methyl  alcohol  give 
7-19  c.c.  of  methyl  iodide. 

The  acetone  is  estimated  by  Kramer's  method  :  in  a  50  c.c.  graduated  cylinder  with  a  ground  stopper  are  placed 
10  c.c.  of  a  2N-caustic-soda  solution,  then  1  c.c.  of  the  alcohol,  and,  after  shaking,  5  c.c.  of  a  2N-iodine  solution. 
After  a  short  time  10  c.c.  of  ether  free  from  alcohol  are  added,  the  liquid  shaken  and  then  allowed  to  stand  ;  the 
volume  occupied  by  the  ether  is  read  off,  an  aliquot  part  of  it  evaporated  to  dryness  on  a  tared  watch-glass  and 
the  iodoform  crystals  dried  in  a  desiccator  and  weighed  :  394  parts  CHI,  correspond  with  58  of  acetone. 

A  good  commercial  methyl  alcohol  should  contain  not  more  than  0-7  per  cent,  of  acetone  and  at  least  95  per 
cent,  of  the  alcohol ;  it  should  distil  within  1°  ;  5  c.c.  of  0-1  per  cent,  permanganate  solution  should  not  be  decolo- 
rised immediately  when  treated  with  5  c.e.  of  the  alcohol,  and  25  c.e.  of  the  alcohol,  mixed  with  1  c.c.  of  an  acetic 
acid  solution  of  bromine  (1  part  Br  in  80  parts  of  50  per  cent,  acetic  acid)  should  give  a  yellow  solution. 

Detection  of  Methyl  Alcohol  in  Ethyl  Alcohol.  To  0-1  c.c.  of  the  alcohol,  in  a  test-tube,  are  added  5  c.c. 
of  1  per  cent,  potassium  permanganate  solution  and  0-2  c.c.  (not  more)  of  pure,  concentrated  sulphuric  add.  The 
liquid  is  shaken  and  left  at  rest  for  2  or  3  minutes,  1  c.c.  of  8  per  cent,  oxalic  acid  solution  being  then  added.  The 
mixture  i?  again  shaken  and  when  it  has  assumed  a  brownish  yellow  coloration,  1  c.c.  of  concentrated  sulphuric 
acid  is  added,  decolorlsation  then  occurring  in  a  few  seconds.  Five  c.c.  of  rosaniline  bisulphite  are  then  mixed 
with  the  liquid,  which  is  afterwards  allowed  to  stand.  With  ethyl  alcohol  alone,  an  intense  greenish  to  violet 
coloration  is  obtained,  but  this  disappears  after  a  few  minutes.  But  if  the  alcohol  contains  even  as  little  as  1  per 
cent,  of  methyl  alcohol,  the  more  or  less  blue  coloration  persists  for  several  hours. 


108  ORGANIC    CHEMISTRY 

In  1902,  Germany  produced  5000  tons  of  the  pure  spirit,  of  which  1151 
tons  was  exported,  and  imported  4273  tons  of  the  crude  product.  In  1910 
England  imported  448,500  galls,  of  methyl  alcohol  and  exported  47,290  galls. 
The  United  States  exported  1,691,000  galls,  in  1910  and  2,040,000  (£179,600) 
in  1911. 

Pyroligneous  alcohol  of  90  per  cent,  strength  (French)  is  sold  at  £4  12s. 
per  100  kilos ;  that  of  92  to  93  per  cent,  strength  (English)  at  £4  17s.  6d. ;  and 
that  of  95  to  96  per  cent,  strength  for  lacs  at  £5  Is.  Qd.  ;  the  purest  methyl 
alcohol,  free  from  acetone,  costs  £7  per  100  kilos. 

ETHYL  ALCOHOL,   C2H5-OH  (Ethanol,  Spirit  of  Wine) 

This  is  found  rarely  in  nature  (as  butyric  ester  in  Pastinaca  sativa)  and  sometimes  as 
an  abnormal  product  in  certain  vegetables  and  animals,  whilst  it  is  easily  formed  by  the 
alteration  (fermentation)  of  various  organic  vegetable  substances  (saccharine  juices, 
fruits,  &c.)-  It  has  hence  been  known  from  the  most  remote  times.  Aqua  vitae  or  spirit 
of  wine,  obtained  by  distilling  alcoholic  beverages,  was  used  as  early  as  the  eighth  century 
and  gave  rise  to  an  industry  which  acquired  great  renown  in  the  province  of  Modena 
in  the  fourteenth  century.  Various  European  races  learnt  the  use  of  aqua  vitse  from  the 
custom  introduced  everywhere  by  the  soldiers,  who  consumed  large  quantities  of  it  during 
the  wars  of  the  Middle  Ages.  But  very  soon  the  northern  peoples,  who  did  not  produce 
aqua  vitae  from  wine,  began  to  prepare  alcohol  by  suitable  transformations  of  the  starch 
in  the  cereals  abounding  in  their  countries.  By  the  beginning  of  the  nineteenth  century 
alcoholic  liquors  (exciting  and  enfeebling  the  nervous  system  and  the  brain)  were  spread 
over  the  whole  of  the  civilised  world  and  produced  the  terrible  social  scourge  of  alcoholism, 
much  more  disastrous  in  its  material  and  moral  consequences  than  all  the  other  maladies 
that  afflict  humanity  (see  later,  Alcoholism).  Later,  however,  alcohol  gradually  acquired 
agricultural  and  industrial  importance  owing  to  its  increasing  practical  applications  in 
the  arts  and  industries.  Since  1830  Germany  has  extended  the  manufacture  of  potato 
spirit,  and  in  many  districts  great  agricultural  advantages  have  followed  the  culture  of 
this  vegetable,  since  the  waste  products  from  the  distilleries  serve  as  nourishment  for 
large  numbers  of  cattle — a  source  of  great  direct  and  indirect  profit  owing  to  the  abundance 
of  stable  manure,  which  increases  the  fertility  of  the  land  and  hence  also  the  crops. 

SYNTHESIS  OF  ALCOHOL.  In  the  laboratory  alcohol  can  be  obtained 
synthetically  by  hydrolysing  ethylsulphuric  acid,  prepared  from  ethylene  and 
concentrated  sulphuric  acid  (Faraday  and  Hennel,  1828).  Alcohol  is  formed 
by  hydrolysing  ethyl  chloride,  and,  since  ethyl  chloride  is  prepared  from  ethane, 
which,  in  its  turn,  can  be  obtained  from  acetylene  and  hydrogen  at  500°  (or 
in  presence  of  platinum  black),  the  synthesis  of  alcohol  from  acetylene  can 
be  effected  (Berthelot,  1855).  Further,  acetylene  can  be  obtained  from 
so-called  inorganic  substances,  from  C  and  H  (Berthelot)  ;  by  decomposing 
calcium  carbonate  with  an  acid,  carbon  dioxide  is  obtained,  and  magnesium, 
burnt  in  this  gas,  gives  carbon,  which,  with  lime,  gives  calcium  carbide,  and 
this,  with  water,  acetylene  ;  there  is  hence  a  transformation  of  mineral  sub- 
stances into  organic  substances. 

In  1907,  Jonas,  Desmonts,  and  Deglotigny  (Fr.  Pat.  360,180)  proposed 
preparing  alcohol  by  first  forming  acetylene  in  mercurous  nitrate  and  then 
heating  the  mass  to  boiling  ;  the  precipitate  decomposes,  regenerating  the 
mercury  salt  and  evolving  vapours  of  acetaldehyde,  which  are  condensed  and 
converted  into  alcohol  by  means  of  sodium  amalgam  (nascent  hydrogen). 

PROPERTIES.  When  pure,  it  is  a  colourless  liquid  with  a  characteristic 
odour,  sp.  gr.  0-7937  at  15°,  0-80625  at  0°  ;  it  boils  at  78-3°  (or  at  13°  under 
21  mm.  pressure),  and  its  vapour  is  stable  at  300°  ;  at  a  very  low  temperature 
it  gives  a  glassy  mass,  which  at  —135°  is  converted  into  another  solid  mass 
m.pt.  —117°  (enantiotropy,  vol.  i,  p.  191). 

When  concentrated  (absolute)  it  is  extremely  hygroscopic,  and  it  mixes 


PROPERTIES    OF    ALCOHOL  109 

with  water  or  ether  in  all  proportions.  To  obtain  absolute  alcohol,  i.e. 
absolutely  free  from  water,  fractional  distillation  is  not  sufficient,  since  at 
78-15°  an  aqueous  alcohol  containing  95-57  per  cent,  of  alcohol  by  weight 
distils  ;  the  higher  alcohols  also  give  mixtures  with  water  which  boil  at 
lower  temperatures  than  the  corresponding  alcohols.  If  benzene  is  mixed  with 
alcohol,  the  latter  can  be  obtained  pure  although  a  mixture  of  water  and 
benzene  first  distils  over,  then  alcohol  (at  64-8°),  then  alcohol  and  benzene 
(68-2°)  and  finally  pure  alcohol. 

Usually  absolute  alcohol  is  obtained  by  distilling  the  ordinary  90  to  96  per 
cent,  alcohol  over  calcined  potassium  carbonate  or  over  anhydrous  (i.e.  calcined) 
copper  sulphate,  redistilling  over  lime  and  finally  over  baryta  or  a  little  sodium 
or  calcium  ;  or  it  may  be  left  over  powdered  aluminium  until  hydrogen  ceases 
to  be  evolved.  The  aldehydes  of  the  alcohol  can  be  separated  by  boiling 
with  5  per  cent,  of  caustic  soda. 

If  alcohol  contains  a  little  water,  it  becomes  turbid  on  mixing  with  benzene, 
carbon  disulphide,  or  paraffin  oil,  and  turns  white,  calcined  copper  sulphate 
blue,  and  barium  hydroxide  is  precipitated  on  addition  of  baryta,  the  latter 
dissolving  only  in  the  absolute  alcohol. 

A  mixture  of  53-9  vols.  of  alcohol  with  39-8  of  water  gives  100  vols.,  the 
contraction  of  3-7  per  cent,  being  due  to  the  formation  of  a  labile  compound, 
(C2H5-OH)18,H20  (or  2H20,  &c.).  It  is  a  good  solvent  for  resins,  oils,  colour- 
ing-matters, varnishes,  ethereal  essences  and  many  other  substances,  and  dis- 
solves sulphur  and  phosphorus  to  a  slight  extent ;  it  coagulates  proteins  and 
diffuses  through  porous  membranes  more  rapidly  than  water.  It  dissolves 
and  gelatinises  soaps.1 

It  unites  with  various  salts  and  alkalis  as  alcohol  of  crystallisation  (KOH, 
LiCl,  CaCl2,  MgCl2)  (see  p.  107). 

It  oxidises  easily,  giving  aldehyde  and  acetic  acid,  e.g.  with  potassium 
dichromate,  Mn02  or  even  H2S04,  or  oxygen  in  presence  of  platinum,  or  with 
micro-organisms  if  the  solution  is  dilute.  With  concentrated  nitric  acid,  it  gives 
various  oxidation  products  and  with  the  dilute  acid,  glycollic  acid.  Alcoholic 
solutions  of  caustic  alkalis  turn  brown,  since  they  are  partially  resinified  by 
the  aldehyde  which  forms  first  and  which  acts  as  a  reducing  agent.  Chlorine 
gives  acetaldehyde  and  various  intermediate  chlorinated  products.  In  a 
red-hot  tube  it  decomposes,  giving  hydrogen  and  many  hydrocarbons  and 
acids.  With  sodium  it  gives  sodium  ethoxide  in  the  form  of  a  white  powder. 

Absolute  alcohol,  which  plays  an  important  part  in  organic  syntheses,  is 
poisonous  and  rapidly  produces  death  when  injected  into  the  blood. 

The  complete  combustion  of  1  kilo  of  pure  alcohol  (C2H5-OH  +  60  = 
2C02  +  3H20)  generates  7193  cals.  and  96  per  cent,  alcohol,  about  6750  cals. 

Alcohol  can  be  detected  even  in  traces  (1  :  2000)  by  means  of  Lieben's 
iodoform  reaction  (see  pp.  101  and  107).  This  reaction  is  also  given  by  acetone, 
isopropyl  alcohol,  and  the  aldehydes  ;  according  to  Buchner  (1905)  it  is 
preferable  to  heat  the  alcoholic  liquid  with  a  little  paranitrobenzoyl  chloride, 
which  forms  crystals  of  ethyl  paranitrobenzoate,  N02-C6H4-C02C2H5, 
m.pt.  57°.  In  Rimini's  reaction,  the  liquid  is  heated  with  sulphuric  acid,  and 
a  dilute  solution  of  potassium  dichromate  :  the  green  colour  of  the  solution  and 
the  odour  of  acetaldehyde  are  sufficiently  characteristic,  but  the  reaction  can 
be  confirmed  by  distilling  a  few  drops  of  the  liquid  and  treating  the  distillate 

1  Solid  Alcohol  is  nothing  but  a  soapy  mass  formed  from  about  20  per  cent,  of  water,  20  per  cent,  of  soap 
(sodium  stearate)  and  60  per  cent,  or  more  of  alcohol ;  it  burns  like  liquid  alcohol  but  leaves  a  residue. 

A  richer  product  can  be  prepared  by  heating  and  stirring  100  parts  of  96  per  cent,  alcohol  at  60°,  dissolving 
1  part  of  stearine  and  adding  0-5  part  of  a  30  per  cent,  aqueous  sodium  hydroxide  solution— just  sufficient 
to  make  it  redden  phenolphthalein.  Some  use  a  sodium  soap  charged  with  silicate  (500  per  cent.).  A  solid  alcohol 
that  burns  without  leaving  a  residue  can  be  obtained  by  dissolving  20  to  40  parts  of  collodion  in  100  parts  of  alcohol ; 
others  add,  instead,  25  parts  of  a  25  per  cent,  solution  of  cellulose  acetate  in  acetic  acid,  and  shake,  the  crust  of 
solid  alcohol  which  separates  being  squeezed  out. 


110  ORGANIC    CHEMISTRY 

with  a  little  sodium  nitroprussiJe  and  a  drop  of  piperidine,  a  beautiful  blue 
coloration  being  obtained  if  acetaldehyde  is  present. 

The  manufacture  of  alcohol  became  One  of  the  great  chemical  industries 
when  a  scientific  explanation  was  obtained  of  the  phenomena  governing  the 
transformation  of  starch  and  sugar.  Fermentation,  although  known  from  the 
most  ancient  times,  remained  unexplained  up  to  the  nineteenth  century,  and 
it  is  solely,  or  largely,  owing  to  the  studies  of  Caignard  de  Latour  and 
Schwann,  Turpin,  Schroeder,  Liebig,  Pasteur,  Nageli,  Cohn,  de  Bary,  and, 
more  recently,  Duclaux,  Buchner,  &c.,  that  the  phenomena  of  fermentation 
are  now  completely  explained  and  rationally  regulated. 

In  1836  Caignard  de  Latour  and  Schwann  found  that  the  fermentation  of  wine  and 
beer  is  strictly  dependent  on  the  germination  of  microscopic  fungi  which  multiply  in  the 
must  or  wort.  Turpin  supposed  that  these  fungi  are  nourished  by  the  sugar,  producing, 
as  the  excreta  of  their  vital  action,  alcohol  and  carbon  dioxide.  In  1838  Liebig  held 
that  this  transformation  of  sugar  is  caused  by  a  special  inter  molecular  movement  due  to 
substances  contained  in  the  ferment  itself  "(microscopic  fungus). 

Pasteur,  in  1872,  showed  that  certain  ferments  that  live  at  the  expense  of  the  oxygen 
of  the  air  and  can  decompose  sugar  into  water  and  carbon  dioxide,  when  they  are 
immersed  in  saccharine  liquids,  being  no  longer  able  to  assimilate  oxygen  from  the  air, 
extract  it  from  the  sugar,  resolving  the  molecule  of  the  latter  into  alcohol  and  carbon 
dioxide.  Although  Nageli,  in  1879,  had  attempted  to  reconcile  the  hypotheses  of  Liebig 
and  Pasteur,  yet  up  to  a  few  years  ago  all  fermentative  phenomena  were  interpreted  on 
the  basis  of  the  ideas  enunciated  by  Pasteur.  Progress  in  the  fermentation  industry 
proceeded,  part  passu,  with  that  of  bacteriology.1 

1  Bacteriology  is  the  science  which  studies  morphologically  and  biologically  the  smallest,  unicellular, 
vegetable  organisms  which  are  propagated  with  immense  rapidity  by  segmentation.  The  cell  is  formed,  as  in  the 
other  organisms,  of  an  extremely  thin  membrane  which  permits  all  the  osmotic  phenomena  (see  vol.  i,  p.  77), 
and  encloses  the  protoplasm  in  which  no  central  nucleus  is  visible,  but  in  which  there  occur  scattered  granules 
(of  starch  and  other  substances),  fat  globules,  vacuoles  containing  cell-sap,  and  sometimes  crystals  (e.g.  of  sulphur), 
while  in  certain  bacteria  the  protoplasm  holds  various  colouring-matters  in  solution.  The  temperature  most 
favourable  to  their  vitality  varies,  according  to  the  species,  from  5°  to  40°  ;  they  live,  however,  in  a  latent  con- 
dition, at  very  low  temperatures,  although  they  do  not  reproduce,  and  they  usually  die  at  about  70° 
(excepting  the  spores,  tee  below).  As,  in  general,  they  do  not  contain  chlorophyll,  they  are  nourished  by  complex 
organic  substances  already  elaborated  by  other  organisms  and  hence  soluble  or  capable  of  being  rendered  soluble 
(sugars,  organic  ammonium  salts,  ammonium  compounds,  &c.) ;  and  in  this  they  are  clearly  differentiated  from 
vegetable  organisms  and  approximate  more  to  the  animals.  Nutrient  matter  for  bacteria  always  contains 
phosphorus,  sulphur,  potassium,  and  calcium,  and,  in  certain  cases,  magnesium  and  manganese.  They  live  well 
and  reproduce  rapidly  in  meat-broth  or  nutrient  gelatine.  They  tolerate  more  easily  alkaline  than  acid  media 
and  direct  sunlight  kills  many  species  of  bacteria,  even  pathogenic  ones.  As  a  result  of  their  vital  actions,  sub- 
stances are  sometimes  formed  which  kill  the  bacteria  themselves.  Different  antiseptics  have  various  actions 
on  different  bacteria,  or  else  only  a  specific  action  on  certain  of  them.  The  reproduction  of  bacteria  takes  place 
ordinarily  by  segmentation,  that  is,  when  the  cell  has  reached  a  certain  length  a  thin  wall  forms  in  the  middle  and 
divides  the  cell  into  two  new  ones  ;  these  divide,  in  their  turn,  so  that  the  reproduction  of  these  organisms,  which 
increase  in  geometrical  proportion  (1,  2,  4,  8,  16,  32,  &c.),  proceeds  with  prodigious  rapidity  and  yields  millions 
of  individuals  in  a  few  hours.  The  universal  distribution  of  bacteria  is  thus  easily  understood.  When  the  vital 
conditions  are  rendered  abnormal  or  difficult  for  bacteria,  in  many  of  them  there  occurs  a  contraction  of  their  proto- 
plasm into  a  more  compact  mass  (at  the  centre  or  laterally,  according  to  the  species),  which  forms  a  separate 
individual,  the  spore,  much  more  resistant  to  cold  (—180°)  and  heat  (130-140°),  and  even  to  antiseptics  than  the 
corresponding  bacterial  cell ;  the  spores  can  retain  life  even  for  some  years.  Under  favourable  conditions,  the 
spore  breaks  its  envelope  and  gives  a  cell  which  reproduces  by  segmentation  like  the  original  one.  Only  certain 
rare  species  of  bacteria  are  provided  with  chlorophyll  or  other  colouring-matters  capable  of  assimilating  carbon 
dioxide  under  the  action  of  sunlight. 

These  micro-organisms,  termed  bacteria  or  schizomycetes  or  microbes,  are  those  which  produce  putrefaction 
and  infectious  diseases  (cholera,  carbuncles,  typhus,  tuberculosis,  small-pox,  diphtheria,  &c.) ;  they  are  classified, 
according  to  their  form,  into:  (1)  Desmobacteria  (bacillus  or  vibrio  forms  like  small  rods);  (2)  Sphere 
bacteria  (cocci  and  micrococci  of  spherical  shape  and  termed  diplococci  if  united  in  twos,  staphylococci  if  joined 
in  bunches,  and  streptococci  if  in  strings) ;  (3)  Spirobacteria  (spirilla  of  twisted  shape).  To  give  a  concrete  idea 
of  their  forms  de  Bary  described  them  as  analogous  to  a  pencil,  a  billiard  ball,  and  a  corkscrew. 

On  the  basis  of  their  different  activities  and  physiological  properties  Cohn  divided  all  the  species  of  bac- 
teria into  three  characteristic  groups  :  (1)  zymogenic,  or  those  which  produce  all  the  non-alcoholic  feimentations  ; 
(2)  ehromogenic,  which  produce  various  colouring-matters  (red,  violet,  yellow,  &c.) ;  (3)  pathogenic,  which  cause 
diseases  of  man  and  animals.  To  recognise  the  latter — given  the  difficulty  of  distinguishing  them  morphologicaly 
under  the  microscope,  since  different  species  often  have  the  same  form  and  the  same  species  sometimes  several 
forms — they  are  inoculated  into  the  blood  of  living  rabbits,  rats,  guinea-pigs,  &c.,  the  pathogenic  character 
being  deduced  from  the  effects  produced  in  the  animals  in  two  or  three  days,  or  sometimes  even  after  a  few 
hours. 

The  lesser  diameter  (width)  of  these  unicellular  bacteria  measures  a  few  tenths  of  a  micron  (1  micron  or  /*  = 
0-0001  mm.),  and,  in  rare  cases,  as  much  as  1-7  M  ;  the  greater  diameter  (length)  is  usually  several  microns. 

If  we  wish  to  indicate  bacteria  in  a  wider  sense  of  the  term,  and  not  to  limit  them  to  the  pathogenic  or  sapro- 
phylic  (non-pathogenic)  but  still  to  those  that  produce  all  putrefactions  and  widen  the  limits  of  their  dimensions, 


FERMENTATION  111 

During  recent  times,  however,  new  facts  have  been  discovered  which  have  profoundly 
shaken  the  fundamental  basis  of  this  theory,  according  to  which  no  fermentation  is 
possible,  except  in  the  presence  of  certain  species  of  living  micro -organisms.  In  reality 
certain  special  fermentations  are  already  known  which  are  produced  by  enzymes,  i.e. 
substances  of  complex  chemical  compositions  which  do  not  manifest  anything  in  the 
nature  of  living  micro-organisms  ;  for  example,  diastase  transforms  starch  into  maltose  • 
2(C6H1005).V  +  H20  =  aAaH^Ou.1 

In  1900  Buchner  succeeded  in  showing,  by  careful  experiment,  that  some  of  these 
fermentations,  which  in  the  past  could  only  be  induced  by  the  living  micro-organisms, 
could  also  be  effected  by  using  the  extract  of  the  bacteria  obtained  by  squeezing  out, 
under  great  pressure,  through  special  unglazed  porcelain  niters,  the  extract  of  the  ferment- 
cells  previously  ground  with  quartz-sand.  In  this  way  Saccharomyces  cerevisice  yields 
maltase  (which  is  an  enzyme  occurring  also  in  germinating  barley  or  maize  and  contained 
in  Saccharomyces  octosporus),  which  hydrolyses  maltose,  transforming  it  into  glucose  ; 
f  i'om  beer-yeast  is  obtained  invertase  (or  invertin)  capable  of  resolving  saccharose  or  cane- 
sugar  (not  directly  fermentable)  into  fructose  and  glucose  (fermentable)  ;  fresh  yeast 
calls  yield  zymase,  the  enzyme  capable  of  effecting  the  alcoholic  fermentation  of  various 
six-carbon-atom  sugars  (glucose,  fructose,  &c.). 

The  action  of  the  enzyme  cannot  be  attributed  to  the  still  living  protoplasm  derived 
from  the  cells  of  the  ferment,  since  the  protoplasm  can  easily  be  killed  in  a  mixture  of 
alcohol  and  ether,  and  after  this  treatment  the  enzyme  retains  its  activity.  The  action 
of  ferments  is  hence  due  to  the  enzymes  that  they  are  able  to  produce,  rather  than  to 
the  biological  phenomena  of  the  life  of  the  organisms. 

To-day  numerous  enzymes  are  known  which,  are  of  great  importance  in 
many  vital  functions  of  vegetable  and  animal  organisms.  It  is  not  certain 
if  the  enzymes,  with^their  large  and  complex  molecules,  are  true  proteins, 
since  up  to  the  present  they  have  not  been  obtained  chemically  pure  ;  all  of 
them  contain  nitrogen  but,  as  they  are  purified  more  and  more,  the  nitrogen 
content  continually  diminishes  and  to-day  it  is  held  by  some  that  the  com- 
position of  each  enzyme  approaches  that  of  the  substance  it  transforms  ;  so 
that  diastase  would  be  a  substance  similar  to  starch  and  poor  in  nitrogen, 
whilst  the  enzymes  that  transform  the  proteins  would  be  of  true  protein  nature. 
Proteolytic  (decomposition  of  proteins)  and  fermentative  actions  only  occur 

we  can  logically  divide  these  micro-organisms  into  two  other  similar  groups  of  similar  beings,  namely,  the 
Hyphomycetes  (moulds)  and  the  Blastomycetes  (ferments). 

The  Hyphomycetes  form  groups  of  branched  filaments  (mycelia),  which  often  subdivide  into  portions  similar  to 
bacteria,  but  the  width  of  these  always  exceeds  2/x,  and  often  5/x  ;  they  multiply  by  means  of  spores  and  four 
principal  species  are  distinguished  according  to  the  mode  of  formation  of  these  spores  (conidia)  :  (1)  the  Aspergittus 
species  which  form,  at  the  extremities  of  the  fruit-bearing  filaments  (spore-bearing  hyphce),  a  swelling  in  the  form  of 
a  club  covered  with  series  of  spores  attached  by  means  of  intennediaFe  steriymata  ;  (2)  the  Mucor  species  (or 
Mucedinece),  in  which  the  spore-bearing  hyphse  which  start  from  the  mass  of  mycelia  carry  sporangia  (species  of 
capsule)  in  which  the  spores  develop  ;  (3)  the  Oidium  species  in  which  the  spores  are  formed  directly  in  the  spore- 
bearing  hyphae  without  any  special  organ  of  fructification ;  (4)  the  Penicillium  species,  which  is  very  common 
and  has  branched  spore-bearing  hyphse  in  the  form  of  a  brush  containing  series  of  spores  AsperyiUus  and  Oidium 
are,  however,  not  separate  species  but  special  sporifying  forms  of  Eurotium  and  Erysiphw  belonging  to  the  order 
of  Ascomycetes. 

The  most  important  of  these  micro-organisms  for  industrial  purposes  are  the  Blastomycetes,  i.e.  the  ferments 
or  unicellular  fungi  which  usually  multiply  by  gemmation  (budding),  that  is,  by  excrescences  forming  on  the  cells 
and  becoming  detached  when  they  have  reached  a  certain  size,  forming  new  cells  which  live  independently  of  the 
mother-cells ;  under  abnormal  conditions,  however,  the  ferments  multiply  also  by  means  of  spores,  four  nuclei 
being  usually  formed  inside  the  cell,  these  then  becoming  covered  with  membranes  and  dividing  the  mother-cell 
into  four  parts  forming  four  new  cells. 

The  cells  of  the  ferments  have  often  a  magnitude  greater  than  5/x,  and  the  most  important  for  alcoholic 
fermentation  form  the  family  of  the  Saccharomycetes  (see  later). 

The  extraordinary  beneficial  influence  of  the  bacteria  and  ferments  in  nature  (apart  from  the  pathogenic  action 
of  certain  of  them  on  some  of  the  higher  organisms)  is  manifested  in  the  wonderful  destructive  activity  they  exert 
on  the  refuse  and  remains  of  all  the  higher  organisms,  converting  the  complex  substances  composing  them  into 
continually  more  simple  substances  until  they  give  CO.,,  HaO,  NH,,  and  HNO,.  These  are  the  simplest  materials 
which  can  be  used  by  vegetable  organisms  to  recommence  the  life-cycle,  since  in  nature  nothing  is  destroyed  or 
created,  but  everything  is  transformed  and  thus  life  itself  rendered  eternal. 

1  Starch,  which  is  formed  in  the  green  leaves,  of  plants  under  the  action  of  sunlight  and  of  chlorophyll, 
although  an  insoluble  substance  and  very  resistant  to  various  reagents,  emigrates  during  the  night  and  accumulates 
in  the  seeds,  roots  (tubers),  medulla,  &c.  We  can,  however,  stop  the  starch  in  its  path,  and  can  explain  how  it 
can  be  transported  by  the  juices  into  other  parts  of  the  plant.  In  fact,  various  enzymes  occur  distributed  through 
plants,  and  among  these  is  diastase  or  amylase,  which  renders  the  starch  soluble  by  transforming  it  into  soluble 
(and  hence  transportable  by  the  juices)  sugar  (maltose),  to  be  regenerated  by  an  inverse  process — unknown  to  us— 
in  the  form  of  insoluble  starch  in  other  parts  of  the  plant. 


112  ORGANIC    CHEMISTRY 

between  certain  limits  of  temperature  (0-65°)  and  are  retarded  or  prevented 
by  certain  poisons  (e.g.  by  traces  of  prussic  acid  or  by  metallic  salts  that  act 
on  proteins,  like  HgCl2,  &c.,  although  they  are  more,  and  sometimes  completely, 
resistant  to  the  action  of  antiseptics  that  kill  ferments,  such  as  salicylic  acid, 
boric  acid,  ether,  &c.).  The  various  enzymes  produce  one  or  other  of  the 
following  general  reactions  :  hydrolysis  (amylases,  sucrases),  coagulation 
(enzyme  of  rennet),  decomposition  (zymase  of  alcoholic  fermentation),  oxidation 
(laccase  oxidises  the  juice  of  the  lac-tree),  &c.  Enzymes  exhibit  different 
behaviour  towards  the  stereoisomerides  of  certain  hydrolysable  and  ferment- 
able substances  (see  section  on  Sugars).1 

1  The  following  are  some  of  the  more  important  enzymes  : 
Diastase  (or  amylase)  occurs  abundantly  in  malt  (germinating  cereals)  but  is  found  also  in  plants,  the  pancreas, 

the  saliva,  the  liver,  the  bile,  the  blood,  the  kidneys,  and  the  mucous  membrane  of  the  stomach  and  of  the 

intestines ;   it  transforms  starch  into  maltose  and  dextrin. 
Maltase  transforms  maltose  into  glucose,  and  is  found  in  malt,  in  Saccharomyces  cerevisice,  and  in  plants  and 

animals. 
Zymase   causes  alcoholic    fermentation  of    glucose  and  is  contained  in   yeast  and  the  alcoholic   ferments 

(Saccharomyces). 

Lactase  decomposes  milk-sugar. 

Melibiase  resolves  rafflnose  (or  cane-sugar)  into  molecules  of  more  simple  sugars. 
Invertase  (sucrase,  saccharase,  or  inverting  decomposes  saccharose  into  glucose  and  levulose,  and  is  obtained  from 

beer-yeast. 

Cytase  or  Cellase  attacks  cellulose. 
Maltodextrinase  ferments  maltodextrin. 
Dextrinase  ferments  dextrins. 

Peptase  governs  the  important  digestive  functions  of  the  stomach,  and  peptonises  proteins. 
Tryptase  is  found  in  the  pancreas  and  contributes  to  the  peptonisation  and  decomposition  of  the  proteins, 
Lipase  is  also  found  in  the  pancreas  and  renders  the  fats  soluble  (hydrolyses  them). 
Emulsin,  contained  in  bitter  almonds,  and  capable  of  decomposing  amygdalin. 
Ptyaiiii  is  contained  in  the  saliva  and  initiates  the  digestion  of  starchy  foods. 
Reductase  is  capable  of  effecting  reduction  phenomena,  especially  in  presence  of  aldehydes,  and  is  hence  also 

known  as   aldehydo-catalase ;    it  decolorises  Schardinger' s  reagent   (mixture  of  methylene   blue    and 

formalin).     Reductase  is  widespread  in  the  animal  kingdom  and  occurs  in  unboiled  milk  (boiled  milk  is 

detected  by  the  lack  of  this  enzyme  ;  it  does  not  decompose  water  or  decolorise  guaiacol). 
The  Oxydases  form  a  group  of  enzymes  (laccase,  tyrosinase,  aenoxydase,  catalase,  &c.)  capable  of  effecting 
oxidations  by  fixing  the  free  oxygen  of  the  air  and  transferring  it,  in  the  nascent  state,  to  the  substances  to  be 
oxidised.  They  occur  widespread  in  the  vegetable  kingdom  and  are  also  found  in  the  animal  kingdom,  and  their 
oxidising  action  is  comparable  to  that  of  platinum  black  (catalyst).  In  fact  the  catalase  found  in  the  blood  is 
capable  of  decomposing  H2O2,  giving  nascent  oxygen  and  water  (Loew,  1901).  It  is  now  found  that  the  oxydases 
are  formed  of  mixtures  of  oxygenase  and  peroxydase.  Euler  and  Boliu  (1909)  obtained  a  laccase  of  the  Medicago 
type  in  a  chemically  pure  state,  and  found  it  to  be  composed  of  calcium  salts  and  a  small  amount  of  iron  salts 
of  mono-,  di-,  and  tri-basic  hydroxy-acids,  especially  citric,  malic,  mesoxalic,  and  glycollic  acids. 

Peroxydases  and  Oxygenases.  Schonbein  (1856)  had  observed  that  certain  vegetable  and  animal 
organisms  contain  substances  analogous  to  ferments  and  capable  of  decomposing  hydrogen  peroxide  catalytically 
with  liberation  of  oxygen,  and  also  of  accelerating  catalytically  this  decomposition  (i.e.,  the  oxidising  action) 
in  the  same  way  that  ferrous  sulphate  does.  Loew  (1901)  showed  that  the  first  action  is  due  to  a  special  enzyme, 
catalase  (oxygenase).  Linossier,  in  1898,  succeeded  in  separating  from  pus  an  enzyme  free  from  oxydase  (oxygenase), 
yet  capable  of  accelerating  but  notof  initiating  the  decomposition  of  hydrogen  peroxide  ;  this  he  called  peroxydase. 
The  oxydases  and  peroxydases  often  occur  together  and  they  may  be  separated  by  heating  the  mixture  to  70°, 
the  oxydase  being  thus  killed,  or,  as  was  proposed  by  Aso  of  Tokio  (1902),  by  dissolving  the  peroxydase  in  alcohol 
which  does  not  dissolve  the  oxydase,  or  by  poisoning  the  latter  with  sodium  fluoride  or  fluosilicate.  There  are 
also  several  plants  that  contain  only  peroxydases,  among  them  pumpkins  and  horse-radish  roots  (Bach  and  Chodat, 
1903,  1906). 

The  peroxydases  are  nitrogenous  but  non-protein  substances,  and,  when  heated  with  NaOH  give  NH8  ;  they 
always  contain  about  6  per  cent,  of  ash,  0-8  to  1-4  per  cent,  being  aluminium  and  0-2  to  0-6  per  cent,  manganese. 
The  peroxydases  dialyse,  whilst  the  oxygenases  do  not.  The  specific  action  of  the  peroxydases  consists  in  activating 
in  a  remarkable  manner  the  oxidising  action  of  H2O,  on  organic  substances,  e.g.  gallic  acid,  pyrogallol,  &c. ;  they 
activate  also  the  action  of  the  peroxides  that  form  in  organic  substances  by  the  action  of  the  oxygen  of  the  air 
(e.g.  ethereal  oils,  turpentine,  &c.). 

In  1897  Bertrand  introduced  the  following  hypothesis  to  explain  the  action  of  the  oxydases  :  the  latter  are 
regarded  as  hydrolysable  manganous  protein  compounds,  in  which  the  manganese,  in  the  mauganous  condition, 
is  the  transmitter  of  oxygen  from  the  air  to  the  oxidisable  substance  ;  the  manganese  dioxide  formed  would  then 
be  again  reduced  by  the  protein  acid  radical,  the  original  manganous  protein  compound  being  regenerated.  Bach 
and  Chodat  have,  however,  found  manganese  in  the  peroxydases,  although  these  are  not  direct  oxidising  agents. 

The  peroxydases  have  no  oxidising  action,  unless  a  peroxide  is  present.  They  do  not  turn  fresh  guaiacol 
tincture  blue,  but  after  some  hours  this  change  does  occur,  the  tincture  having  formed  peroxide,  which  can  be  detected 
by  starch  and  potassium  iodide  solution.  Whilst  the  peroxydases  accelerate  the  decomposition  of  very  dilute 
H2O2,  this  kills  them  if  concentrated.  In  1908  J.  Wolff  obtained  the  reactions  of  the  peroxydases  by  traces  of 
ferrous  sulphate  or  copper  sulphate.  The  oxidising  action  of  the  oxygenases  (which  have,  however,  not  yet  been 
obtained  free  from  peroxydases,  although  the  latter  are  known  free  from  oxygenases)  is  only  weak  and  is  strongly 
activated  by  addition  of  peroxydase.  On  the  other  hand,  it  seems  established  that  there  are  two  species  of  peroxy- 
dases existing,  the  one  activating  strongly  the  oxygenases  and  feebly  the  decomposition  of  H2O2,  and  the  other 
behaving  in  the  opposite  way.  The  character  of  the  oxydases  themselves  is  indicated  by  the  specific  action  of  one  or 
the  other  species  of  peroxydase.  Indeed,  Bertrand  had  in  1896  extracted  from  certain  plants,  e.g.  young  potato 
tubers)  an  oxydase  which  differed  from  all  others  in  not  oxidising  phenols  or  the  aromatic  amines,  whilst  it  oxidised 
and  blackened  tyrosine,  which  is  not  altered  by  the  ordinary  oxydases  or  even  by  the  presence  of  H,Oa  alone. 
Bach  (1906)  succeeded  in  separating  the  specific  peroxydase  from  tyrosinase  and  in  showing  that  this  peroxydase 


ENZYME    ACTIONS  113 

But  still  more  interesting  is  the  fact  that  during  an  ordinary  fermentation  the  amount 
of  sugar  fermented  does  not  depend  closely  on  the  quantity  of  living  ferment  or  enzyme  ; 
thus  large  quantities  of  sugar  can  be  decomposed  by  small  quantities  of  ferment  or  enzyme. 

The  action  of  the  enzymes  and  of  the  ferments  may  be  logically  compared  with  that 
of  the  inorganic  catalysts  (vol.  i,  p.  67),  which  only  produce  an  enormous  increase  in  the 
velocity  of  reaction,  in  our  case,  of  the  decomposition  of  sugar.  And  that  these  organic 
catalysts  have  an  action  really  similar  to  that  of  the  inorganic  catalysts  can  be  shown  by 
certain  other  interesting  facts. 

Some  years  ago  Duclaux  succeeded  in  producing  alcoholic  fermentation  by  dilute 
alkali  ;  Traube  in  1899  transformed  sugar  into  alcohol  by  means  of  finely  divided  platinum 
alone  at  160°  ;  while  Schade  in  1906  converted  an  alkaline  solution  of  glucose,  in  absence 
of  enzyme,  quantitatively  into  acetaldehyde  and  formic  acid  (C6H12O6  =2C2H4O  +2CH2O2), 
and  these  products,  under  the  catalytic  influence  of  rhodium,  are  transformed  quantitatively 
into  C02  and  alcohol  (perhaps  the  formic  acid  first  gives  C02  and  H2,  the  latter,  in  the 
nascent  state,  reducing  the  aldehyde  to  alcohol).1 

Further,  as  in  chemical  equilibria  (vol.  i,  p.  62),  the  action  of  catalysts  in 
reversible  reactions  is  regulated  by  conditions  of  temperature  and  of  con- 
centration different  from  those  met  with  in  the  case  of  enzymes  :  indeed, 
when  diastase  has  converted  a  certain  quantity  (dependent  on  the  temperature) 
of  starch  into  maltose,  the  hydrolytic  change  is  arrested  (i.e.  equilibrium  is 
reached  in  the  reversible  reaction  :  starch  t;  maltose)  ;  but  if  part  of  the 
maltose  is  fermented  into  alcohol  and  C02,  the  equilibrium  is  disturbed  and 
the  diastase  hydrolyses  a  further  quantity  of  starch.  Also  at  temperatures 
above  55°,  diastase  forms  dextrin  in  preference  to  maltose.  An  analogous 
phenomenon  is  observed  in  the  hydrolysis  of  amygdalin  by  emulsin.  It  has 
already  been  mentioned  that  maltase  transforms  maltose  first  into  glucose, 
but  when  a  certain  proportion  between  these  two  products  is  reached,  the 
hydrolysis  ceases  owing  to  equilibrium  being  attained  :  C12H220U  +  H20  ^ 
2C6H1206,  and  the  transformation  proceeds  only  when  the  glucose  is  removed 
by  alcoholic  fermentation  ;  Emmerling  has  realised  the  inverse  reaction 
by  displacing  the  equilibrium  by  addition  of  glucose  (in  which  case  isomaltose 
is  produced). 

is  only  capable  of  causing  the  oxidation  of  tyrosine  when  mixed  with  the  corresponding  oxygenase  or  in  presence 
of  H2Oa  alone.  Hence  the  action  of  tyrosinase  is  due  to  the  specific  action  of  its  peroxydase.  Bach  holds  further 
that  in  the  phenomena  of  respiration  of  organisms,  oxidation  due  to  oxydases  plays  no  part,  since  this  leads  to 
true  condensations,  to  syntheses  of  more  complex  products  ;  for  respiratory  phenomena  there  should  exist  euzymes 
of  a  type  not  yet  known  and  capable  of  decomposing  and  oxidising  there  serve  materials  of  the  organism  (fats, 
carbohydrates,  &c.,  which  are  not  oxidised  by  oxydases). 

At  the  present  day  the  catalytic  action  of  the  enzymes  is  explained  as  due  to  small  quantities  of  metal  which 
they  contain  ;  thus  the  important  action  of  the  haemoglobin  of  the  blood  (which  fixes  the  oxygen  in  the  lungs 
in  a  labile  condition  and  transports  it  to  all  parts  of  the  organism)  appears  to  be  due  to  the  small  quantities  of 
iron  present,  this  inducing  the  decomposition  of  the  food  materials  ;  thus  the  synthetic  action  of  the  peroxydases 
is  perhaps  due  to  the  manganese  they  contain  (see  above),  just  as  the  important  synthetic  functions  of  chlorophyll, 
according  to  Willstatter's  recent  work,  appears  to  be  owing  to  the  magnesium  present  in  it.  Recently  (1910) 
Bach  has,  however,  succeeded  in  preparing  very  active  oxydases  and  peroxydases  free  from  iron  and  manganese, 
so  that  the  true  explanation  of  the  activity  of  these  enzymes  remains  to  be  discovered. 

1  Buchner  and  Meisenheimer  (1909)  explain  the  action  of  ferments,  from  the  chemical  point  of  view,  by  the 
addition  of  a  molecule  of  water  to  the  sugar  and  abstraction  of  an  atom  of  oxygen  by  the  ferment,  so  that  there 
results,  as  an  unstable  intermediate  product,  a  dihydric  alcohol,  which,  in  its  turn,  is  immediately  decomposed 
into  H2  and  2  mols.  of  dihydroxyacetone  ;  the  last  product  is  able  to  decompose  into  CO2  and  alcohol,  while  the 
hydrogen  continues  to  transform  fresh  quantities  of  sugar  into  the  dihydric  alcohol,  and  so  on.  Boysen-Jensen 
(1909)  finds  that  the  reactions  for  dihydroxyacetone  are  given  by  fermentations  ;  the  decomposition  would  hence 
take  place  thus  : 

CH2OH  CH2OH  CH2OH 

CH, 
CHOH  CHOH  CO  -»  CO.  +       • 

C'llj,-  UJ1 

CHOH  CHOH  CH,OH 

+  H,0  =  O  +      .  -»     H2  +         pH'OH 

CHOH  CHOH 

CH, 

CHOH  CHOH  CO      ~*  C02  +   •        - 

CH2-UH 

CHO  CH,OH  CH.OH 

Glucose  Dihydric  alcohol  2  mols.  of  2  mols. 

Dihydroxyacetone  of  Alcohol 

ii  8 


114  ORGANIC    CHEMISTRY 

Also  in  the  action  of  maltase  on  amygdalin,  Emmerling  succeeded  in 
producing  the  reverse  reaction,  and  at  the  St.  Louis  Exhibition  in  1904  he 
showed  a  fine  specimen  of  amygdalin  prepared  synthetically  by  an  enzymic 
process.1 

So  that  with  one  and  the  same  enzyme,  analytic  and  synthetic  processes 
can  be  effected.  Cremer  obtained  glycogen  (C6H1005)y  from  levulose  by 
means  of  an  extract  of  yeast,  and  Hanriot,  Kastle,  and  Loewenhart  prepared 
monobutyrin  and  butyl  acetate  synthetically  by  means  of  lipase.  The 
enzymes  also  effect  the  so-called  asymmetric  syntheses,  i.e.  they  give  optically 
active  compounds  containing  asymmetric  carbon  (1908). 

Also  interesting  is  the  fact  that  a  single  ferment  may  contain  various 
enzymes ;  thus,  from  Saccharomyces  cerevisice,  maltase  and  invertase  can  be 
extracted  easily  and  also  zymase,  though  with  more  difficulty. 

These  recent  discoveries  on  the  reversibility  of  the  reactions  effected  by 
enzymes  are  of  great  importance,  as  it  was  at  first  thought  that  enzymes  or 
ferments  in  general  were  capable  of  causing  only  decompositions  and  not 
synthetical  reactions,  whereas  their  analogy  with  inorganic  ferments  is  now 
complete.  But  the  discoveries  are  all  the  more  remarkable,  since  the  same 
phenomenon  of  vitality — in  the  single  cell  as  in  more  complex  organisms — 
can  be  reduced  to  an  enzymic  phenomenon  ;  that  is  to  say,  the  exchange  of 
material  in  the  organism  (decomposition,  recomposition,  growth)  takes  place 
by  means  of  these  organic  catalysts,  which  cause  the  decomposition  of  food, 
preparing  various  complex  materials  which  form  the  organism  itself,  and  at 
the  same  time  generating  the  energy  manifested  in  the  vitality,  enzymic 
phenomena  being  always  exothermic.  This  hypothesis  can,  with  advantage, 
be  substituted  for  the  too  abstract  biogen  z  hypothesis,  to  explain  vital 
phenomena. 

1  C.Hs-CHfCI^-C.HnOo  +  C.H1S08         ;±        C20H27NOn  +  H2O 

Glucoside  of  phenylgly-  Maltase           Amygdalin 

collie  nitrile 
or,  more  completely : 

2C«H12O,          +           HCN  +           C6H,,-CHO     ^±     2H2O  +  C20H2,XOU 

Glucose                Hydrocyanic  Benzal- 

acid  dehyde 

«  Hypotheses  of  Biogen,  Toxins,  and  Genesis  of  Life.  The  physical  and  physiological  basis  of  life  resides 
especially  in  the  protoplasm,  the  semi-fluid,  almost  always  colourless,  refractive  substance — insoluble  in  water— 
which  everywhere  constitutes  the  essential  part  of  the  cell.  Protoplasm  is  formed  principally  from  protein  sub- 
stances, whilst  it  is  thought  that  the  fats  and  carbohydrates  are  not  active  components.  To  the  protoplasm  is 
attributed  the  fundamental  property  of  vitality,  i.e.  the  exchange  of  material,  but  it  is  not  known  how  its  com- 
ponents— the  proteins — can  have  such  properties  or  in  what  physico-chemical  aggregation  of  the  proteins  (the  plasti- 
dules  and  bionomads  are  regarded  as  morphological  components  or  units  of  protoplasm)  they  have  their  orign. 

In  animals  one  of  the  principal  functions  of  the  blood  is  that  of  supplying  the  respiratory  needs  of  the  tissues 
in  virtue  of  the  haemoglobin  contained  in  the  blood  of  vertebrates  [besides  fibrinogen,  serum-albumin,  and  para- 
globulin;  whilst  with  the  invertebrates  there  are  echinochrom,  chlorocruorin,  hcemoerythrin,  hcemocyanin  (con- 
taining copper),  and  pinnoglobin  (containing  manganese),  which  have  the  same  functions  as  hsemoglobin] ;  it  is 
formed  of  a  protein  substance  united  with  a  ferruginous  compound,  which  takes  up  oxygen  at  the  respiratory 
surfaces  of  the  organism  (skin,  bronchi,  and  lungs),  and  brings  it  into  close  contact  with  the  tissues. 

The  vital  processes  of  the  organism  being  due  to  the  exchange  of  material  in  the  cells  full  of  protoplasm,  the 
biogenic  hypothesis  assumes  that  this  is  brought  about  by  a  very  complex,  labile  compound,  which,  by  being  con- 
tinually decomposed  and  reconstituted,  maintains  the  interchange  uninterruptedly.  By  many  this  compound 
is  called  living  albumin,  but  Max  Verworn  (1895  and  1902)  regards  this  as  an  unsuitable  name  and  does  not  think 
it  has  been  shown  to  be  a  true  albuminoid,  although  it  is  a  nitrogenous  substance  ;  there  arc  possibly  several  sub- 
stances in  a  state  of  labile  combination  and  these  he  calls  molecules  of  biogen. 

It  has  been  observed  that  in  organisms,  as  in  parts  of  them,  vitality  ceases  when  oxygen  is  eliminated,  many 
of  them  subsequently  (the  frog  even  after  twenty-five  hours)  recovering  it  in  presence  of  oxygen.  From  this  arise 
two  hypotheses  :  (1)  the  molecule  of  biogen  becomes  labile,  and  hence  gives  rise  to  decompositions  and  recompo- 
sitions,  that  is,  to  the  vital  process — since  it  unites  transitorily  with  oxygen  ;  (2)  oxygen  serves  only  to  oxidise 
or  eliminate  the  decomposition  products  of  the  biogen  (admittedly  labile),  and  when  there  is  no  oxygen,  these 
products  are  not  eliminated,  so  that  the  decomposition  and  recomposition  of  the  biogen  arc  arrested.  By 
experiments  on  the  frog  Max  Verworn  has  shown  that  the  foimer  hypothesis  is  the  more  probable. 

Since,  in  the  vital  process,  under  the  action  of  oxygen,  it  is  especially  the  carbon  dioxide  that  is  eliminated, 
often  along  with  lactic  acid,  water,  &c.,  whilst  the  elimination  of  nitrogenous  substances  does  not  increase,  it  may 
be  assumed  that  biogen  is  constituted  of  a  benzene  nuckus  with  lateral  chains  of  carbohydrate  and  aldehydic 
character  and  with  an  oxygen-carrying  nitrogenous  group  which  fixes  the  oxygen  of  the  air  (just  as  NO  gives 
NOj  in  the  lead-chambers  of  sulphuric  acid  works)  and  gives  it  up  to  the  lateral  chain,  which  is  oxidised  (Ehrlich's 
side-chain  hypothesis,  1882-1902)  to  CO2,  lactic  acid,  H.O,  <fcc.,  these  being  eliminated  ;  the  nitrogenous  group, 
thus  reduced,  remains  united  with  the  benzene  group,  wh'ch,  with  new  food,'  oims  the  biogen  molecule,  this 


TOXINS    AND    ANTITOXINS  115 

In  order  to  ascertain  if  a  given  action  is  due  to  enzymes  or  to  organised 
ferments,  the  liquid  is  passed  under  pressure  through  a  Chamberland  porous 
porcelain  filter,  which  retains  the  ferment  cells,  but  not  the  enzymes  ;  the 

being  again  decomposed  by  oxygen  and  so  on.  The  digested  food^inaterials  carry,  with  the  blood,  new  materials 
to  the  regeneration  of  biogen  (without  food,  death  ensues),  the  oxygen  then  effecting  the  changes  described  above. 
The  seat  of  the  biogen  lies  in  the  liquid  protoplasm  of  the  cell  (not  in  its  nucleus),  into  which  oxygen  enters  in  the 
state  of  labile  combinations  not  yet  defined  but  capable  of  giving  it  up  when  needed  :  these  compounds  are  more 
stable  in  the  cold  than  in  the  hot  and  are  those  that  carry  on  the  vitality  during  prolonged  fasts.  These  reserve 
materials  are  probably  formed  by  the  decomposition  of  the  food  by  means  of  intracellular  enzymes,  which  form  the 
connecting-link  between  the  living  substance  (biogen)  and  the  non-living  (foods),  transforming  the  latter  into 
the  former. 

The  biogen  hypothesis  is  opposed  by  that  of  the  enzymes  as  factors  of  the  vital  process  and,  given  the  varied 
nature  of  the  phenomena  and  of  the  chemical  transformations  occurring  in  the  living  organism,  and  the  variety 
of  the  numerous  chemical  groups  forming  a  protein  molecule,  it  is  perhaps  imprudent  to  refer  all  these  phenomena 
to  a  single  compound,  biogen,  when  we  already  know  different  enzymes  which  certainly  effect  well-investigated, 
definite  reactions.  From  the  action  of  different  enzymes  on  the  protein  complex  forming  the  protoplasm  of  the 
cell,  there  results  the  many-sided  phenomenon  of  vitality.  And  in  certain  cases  it  is  possible  to  go  still  further, 
as  it  must  be  admitted  that  many  synthetic  and  analytic  phenomena  of  organic  substances  (e.g.  the  fermenta- 
tion of  sugar)  take  place  even  without  protoplasm,  by  the  direct  action  of  the  enzyme  alone  (see  p.  111). 

Further,  by  simple  catalytic  actions,  it  is  now  possible  to  effect  artificial  fertilisation  (artificial  parthenogenesis) ; 
for  example,  by  treating  unfertilised  eggs  of  the  sea-urchin  with  solutions  of  various  chlorides,  best  of  all, 
magnesium  chloride,  Loeb  (1899  and  1900)  obtained  living  larvae ;  Giard  (1904)  studied  the  artificial  partheno- 
genesis of  the  star-fish  (Asteria  rabens) ;  Tichomiroff  (1886  and  1902)  and,  better,  Quajat  at  Padua  (1905)  obtained 
partial  artificial  parthenogenesis  of  the  virgin  eggs  of  the  silk-worm. 

Most  interesting  of  all  are  the  investigations  on  sero-therapy  which  have  led  to  the  most  unexpected  results 
when,  instead  of  the  observations  being  limited  to  the  bacteria,  the  poisonous  or  beneficial  substances  which 
they  elaborate  or  secrete  have  been  considered.  These  toxins  or  antitoxins  secreted  by  bacteria  or  formed  in 
animal  organisms  also  appear  to  be  enzym'es,  exhibiting,  however,  their  activity  in  phenomena  of  a  different  and 
more  complex  nature 

In  the  last  few  years  (1902-1907)  Arrhenius,  in  conjunction  first  with  the  head  of  the  German  school,  Ehrlich, 
and  later  with  that  of  the  Danish  school,  Madsen,  has  devoted  himself  to  the  interpretation  of  sero-therapy,  making 
effectual  use  of  all  the  modern  laws  of  physical  chemistry.  He  has  succeeded  in  following  and  controlling  the 
formation  and  action  of  toxins  and  antitoxins  in  the  animal  organism  by  empirical  mathematical  formulae, 
calculated  beforehand  from  the  results  of  previous  experiments ;  and  it  is  not  improbable  that  the  time  will 
soon  arrive  when  from  these  empirical  formulae,  suitably  co-ordinated,  rational  formulae  will  be  derived  leading 
to  new  and  important  natural  laws,  from  which  general  pathology  will  obtain  great  principles  rendering  it  possible 
for  man  and  other  animals  to  be  immunised  against  the  attacks  of  pathogenic  bacteria.  Then,  and  only  then, 
will  man  have  triumphed  over  the  microbe. 

By  injecting  more  or  less  poisonous  substances  (toxins)  into  the  animal  organisms,  the  so-called  anti-bodies 
(antitoxins)  are  formed  in  the  blood,  but  their  formation  is  probably  incomplete  in  consequence  of  the  laws 
of  chemical  equilibria  discovered  by  Guldberg  and  Waage  (vol.  i,  p.  62). 

The  corresponding  antitoxins  are  known  for  only  a  few  poisons.  Those  of  solanine  and  saponin  (1901) 
and  of  morphine  (aniimorphine)  (1903)  have  been  sought  for  in  vain  by  inoculating  guinea-pigs  and  rabbits,  so 
that  these  three  poisons  are  not  to  be  regarded  as  toxins.  From  castor-oil  seeds  ricin  has  been  extracted — 
a  toxin  for  which  the  corresponding  antiricin  is  known  ;  also,  seeds  of  Abrus  prcecatorius  and  Robinia  •pseudacacia 
yield  the  poisons  abrin  and  robin,  for  which  the  corresponding  antitoxins  have  been  obtained.  Animals  also 
produce  anti-bodies  of  non-poisonous  substances ;  thus,  if  any  cells  whatsoever  are  injected  into  the  blood,  anti- 
bodies are  more  or  less  rapidly  produced  which  have  a  special  destructive  action  on  these  cells.  Also  by  injecting 
rennet  (which  coagulates  milk)  an  antirennet  is  obtained  which  is  able  to  prevent  the  coagulating  action  of  the 
rennet. 

From  pathogenic  bacteria  are  obtained  anti-bodies  (by  inoculation)  to  certain  proteolytic  eusymes  :  in  1893 
Hildebrandt  found  an  anti-body  to  emulsin  and  Gessard  (1901)  prepared  an  anti-body  to  tyrosinu.se  (see  above) ', 
from  the  serum  of  a  goose  inoculated  with  pepsin,  H.  Sachs  (1902)  obtained  an  antipepsin  ;  A.  Schutze  (1904) 
obtained  antilactase  by  making  subcutaneous  and  intermuscular  inoculations  with  the  lactase  of  kephir  (which 
see),  and  similarly  were  prepared  anti-bodies  to  cynarase,  zymase,  urea.se,  and  the  fibrin  and  pancreatic  ferments. 

It  is  difficult  to  establish  a  limit  or  any  essential  difference  between  enzymes  or  ferments  and  toxins,  and 
the  preparation  of  anti-bodies  to  all  these  active  substances  is,  perhaps,  only  a  matter  of  time.  The  anti-bodies 
are  divided  into  two  classes,  according  as  they  are  obtained  by  inoculation  of  homogeneous  solutions  (toxins) 
or  of  emulsions  of  bacteria  or  cells  (red  blood  corpuscles),  <fec.  The  anti-body  formed  by  the  inoculation  of  a 
homogeneous  solution  combines  with  the  toxin  of  the  latter,  forming  an  innocuous  substance,  which  is  called 
an  antitoxin  if  soluble  or  a  precipitin  if  insoluble.  The  injection  of  bacteria  sometimes  leads  to  the  formation 
of  anti-bodies  capable  of  dissolving  the  bacteria  themselves  (from  which  they  are  derived)  and  then  these  anti- 
bodies are  termed  lysins  (bacteriolysins).  There  may  also  be  formed  anti-bodies  which  agglutinate  the  inoculated 
cells,  i.e.  agglutinins,  but  this  depends  on  the  presence  of  salts.  The  cholesterin  and  lecithin  of  the  organism 
often  form  part  of  the  toxin  or  antitoxin.  Cholesterin,  for  example,  acts  as  an  antitoxin  to  tetanolysin  and 
other  lysins.  According  to  Metchnikoff  it  is  the  leucocytes  (white  corpuscles)  which  produce  the  antitoxins, 
but  this  has  not  been  rigorously  proved,  although  Wright  has  shown  that  certain  anti-bodies  (opsonins)  exhibit 
their  activity  against  bacteria  only  in  presence  of  leucocytes. 

That  the  action  between  toxins  and  antitoxins  resembles  chemical  neutralisation  was  assumed  at  the  time 
of  the  discovery  of  the  first  diphtheritic  antitoxin  by  Bearing  and  Kitasato  in  1890,  and  was  supported  by  the 
German  school  with  Ehrlich  at  its  head.  From  1893,  however,  the  French  school  (Roux,  Vaillaid,  Metchnikoff, 
and  also  Buchner)_  held  that  the  antitoxins  exert  a  physiological  action,  exciting,  as  it  were,  the  organic  tissues 
to  resist  the  attacks  of  these  poisons  (toxins).  When,  however,  Ehrlich  showed  that  the  agglutinating  action 
of  ricin  on  the  red  blood  corpuscles  (suspended  in  physiological  serum,  that  is,  in  0-9  per  cent.  NaCl  solution) 
could  be  annulled  by  simply  adding  antiricin,  and  because  he  showed  that  the  neutralisation  of  the  action  of 
a  given  quantity  of  toxin  required  the  presence  of  a  proportionate  amount  of  antitoxin,  most  scientific  men 
abandoned  the  physiological  hypothesis.  Ehrlich's  more  recent  studies  on  the  action  of  two  arsenical  compounds 
on  the  toxins  have  led  to  the  cure  of  sleeping-sickness  and  probably  to  that  of  syphilis  (by  means  of  the  product 
606).  In  suitable  conditions  of  temperature,  &c.,  the  original  toxins  can  be  regenerated  from  the  antitoxins 
by  a  reversible  process  (Reversible  Reactions,  vol.  i,  p.  63) ;  this  was  shown  by  Morgenroth  (1905)  by  dissociating 


116 

filtered  liquid  is  then  examined  to  ascertain  if  it  still  produces  the  enzymic 
action.  Or  the  liquid  may  be  mixed  with  chloroform,  which  arrests  all  cellular 
life,  but  does  not  act  on  the  enzymes. 

A  liquid  containing  an  enzyme  is  coloured  blue  by  the  addition  of  an 
alcoholic  solution  of  guaiacum  resin,  previously  mixed  with  a  drop  of  hydrogen 
peroxide. 

The  enzymes  are,  as  a  rule,  destroyed  by  boiling. 

INDUSTRIAL  PREPARATION  OF  ALCOHOL.  As  already  mentioned, 
the  prime  materials  are  saccharine  or  starchy  substances  ;  the  latter,  by  the 
action  of  enzymes  (diastase  and  maltase)  are  transformed  into  maltose  and 
glucose,  and  then  by  the  action  of  the  zymase  contained  in  yeast-cells  (species 
Saccharomyces,  see  pp.  Ill  and  121)  the  glucose  is  transformed,  to  the  extent 
of  95  per  cent.,  into  alcohol  and  C02,  with  evolution  of  heat. 

The  treatment  of  the  starchy  materials  is  carried  out  as  follows  :  the 
starch  is  obtained  from  various  prime  economic  materials,  namely,  maize 
(especially  in  Italy,  Hungary,  and  America),  potatoes  (Germany,  France, 
England,  and  Russia  ;  attempts  to  introduce  the  potato  industry  into  Italy 
have  as  yet  come  to  nothing)  ;  cereals  (Russia  and  England)  ;  rice  (England, 
Japan,  China,  Italy). 

There  are  two  practical  processes  :  (1)  the  action  of  dilute  mineral  acids 
in  the  hot,  and  (2)  the  action  of  certain  hydrolytic  enzymes  (like  diastase 
contained  in  malt). 

(1)  Transformation  of  starch  by  dilute  acids.     In  this  transformation,  starch  yields 
glucose  almost  quantitatively :    (C6H10O6)n  (starch)  +  nH2O  =  »C6H12O6,  and  we  shall 
deal  more  in  detail  with  this  process  later  on,  in  the  section  on    Glucose,     At  present 
only  the  second  process  will  be  considered. 

(2)  Transformation  of  starch  by  means    of    enzymes.     Of  the   enzymes,    that   which 
is  of   the  most  service  industrially,  is  diastase.     It  is  formed  more  especially  during 
the  early  stages  of  the  germination  of  cereals  (maize,  barley,  &c.),  and  this  germinated 
gram  forms  malt  which  is  most  favoured  by  a  temperature  of  45-55°  in  its  transformation 
of  starch  into  dextrins  (amylodextrin,  erythrodextrin,  achroodextrin,  (C12H2o01o).v)  and 
into  maltose  and  isomaltose,  C^H^On. 

As  has  been  already  mentioned  (p.  113),  this  reaction  is  regulated  by  the 
laws  of  chemical  equilibria,  and  depends  especially  on  the  temperature  : 

the  antitoxin  with  a  little  HC1  and  destroying  the  anti-body  at  100°.  So  that  validity  can  no  longer  be  ascribed 
to  the  hypothesis  of  Behring  (1890),  Nernst  (1904),  and  Biltz,  Much,  and  Siebert  (1905).  according  to  which  the 
toxins  are  absorbed  by  the  colloidal  antitoxins  and  then  destroyed. 

The  toxins  and  antitoxins,  although  colloidal  substances,  diffuse  easily  and  give  osmotic  pressures  according 
to  van  't  Hoff's  law. 

Toxins  diffuse  through  water  and  gelatine  much  more  rapidly  than  antitoxins,  so  that  a  mixture  of  the  two 
bodies  can  be  separated  into  its  components.  The  difference  in  the  rapidity  of  diffusion  depends  on  the  molecular 
magnitudes  (according  to  E.  W.  Reid,  haemoglobin  has  a  molecular  weight  of  48,000).  The  molecular  weights 
of  the  antitoxins  would  be  10  to  100  times  as  great  as  those  of  the  toxina. 

The  velocity  of  reaction  of  the  different  toxins  does  not  depend,  as  Morgenroth  supposed,  on  catalytic  actions, 
but,  as  Arrhenius  and  Madsen  showed,  on  the  temperature,  and  is  regulated  by  a  law  deduced  from  thermo- 
dynamical  considerations  based  on  van  't  Hotf's  laws  of  solutions. 

A  number  of  other  factors  of  the  vitality  of  the  organism — digestion  of  food,  assimilation  of  carbon  dioxide 
by  plants,  development  of  the  egg,  production  of  alcohol  during  the  fermentation  of  sugar,  &c. — are  due  to 
enzymes  or  toxins  and  antitoxins,  whose  actions  are  regulated  by  the  laws  of  chemical  equilibria  and  of  the 
velocity  of  reaction,  and  are  perhaps  not  disconnected  from  catalytic  phenomena  or  from  reactions  similar  to 
or  identical  with  those  assumed  by  the  biogen  and  side-chain  hypotheses. 

Further,  the  recent  studies  of  O.  Lehmann  and  of  S.  Leduc  (1896)  on  Liquid  Crystals,  according  to 
which,  under  certain  conditions,  solutions  of  substances  can  assume  the  form  of  crystals  or  of  cells  that  grow, 
multiply,  and  die,  like  actual  organisms  (see  vol.  i,  p.  112),  furnish  a  probable  explanation  of  the  transition  from 
organic  substances  to  organised  bodies.  Thus,  after  what  has  been  stated  above,  the  entire  cycle  of  the  genesis 
of  life  can  be  comprehended,  from  the  transformation  of  inorganic  substances  into  organic  (see  p.  108)  and  of 
these  into  organised  (or  living),  by  hypotheses  based  on  scientific"  facts.  It  still  remains,  however,  to  explain 
the  origin  of  the  inorganic  world,  terrestrial  and  extra-terrestrial,  the  answer  of  science  being  that,  in  accordance 
with  Lavoisier's  law,  nothing  is  created  and  nothing  destroyed,  so  that  the  inorganic  world  has  always  existed 
and  is  eternal,  and  eternal  also  is  its  continuous  evolution.  This  is  the  actual  limit  of  human  knowledge,  which, 
in  its  imperfection,  cannot  explain  the  infinite  and  the  eternal.  And  no  metaphysical  philosophy  has  succeeded 
in  obtaining  a  final  clue  to  this  secret  of  eternity,  since  it  is  not  a  plausible  or  even  rational  explanation  to  refer 
the  eternity  of  the  inorganic  world  to  a  hypothetical,  abstract,  supernatural  being  who  created  everything  from 
nothing,  in  contradiction  to  the  fundamental  laws  of  positive  science,  the  fast  of  all  of  these  being  those  of  the 
conservation  of  mass  and  of  energy. 


MANUFACTURE    OF    ALCOHOL 


117 


between   45°   and   50°    maltose    is   preferably   formed,    and   at   about    60°, 
dextrin. 

We  have  already  noticed  how  maltose  is  transformed  into  glucose  by  means 
of  maltase,  and  how  the  chemical  equilibrium  is  displaced,  by  gradually  trans- 
forming the  glucose  into  alcohol  by  fermentation. 

Of  the  various  malts  used  industrially,  that  of  barley  is  the  most  active,  then  follow 
wheat  and  rye,  and,  finally,  maize ;  the  last  named  is  one-third  less  active  than  that  of 
barley,  but  owing  to  its  low  price  has  practical  advantages,  and  in  Italy  is  the  one  most 
commonly  used. 

In  describing  the  industry  of  brewing,  we  shall  deal  in  detail  with  the  practical  manu- 
facture of  malt,  and  we  would  refer  the  reader  to  that  section  for  a  description  of  the 
preparation  of  maize  malt,  which  does  not  differ  from  that  of  barley  malt. 

As  regards  the  use  of  chlorine  dioxide  to  increase  the  germinative  power  of  maize, 
as  proposed  by  Effront,  see  vol.  i,  p.  171. 

The  starchy  matters  forming  the  starting  materials  of  the  alcohol  industry  (cereals, 
potatoes,  &c.)  cannot  be  subjected  to  the  action  of  diastase  unless  their  starch  is  first 
transformed  into  a  semi-solution  (starch-paste)  by  treating  with  water  or  steam  at  a  high 
temperature  ;  the  starch-granules  swell  and  then  burst  and  readily  assimilate  water 
(potato  starch  at  65°,  maize  starch  at  75°,  barley  starch  at  80°).  The  materials  are  hence 
first  steeped  and  ground,  and  then  extracted  with  hot  water,  to  be  subjected  subsequently 
to  saccharification  with  malt  and  finally  to  alcoholic  fermentation. 

The  following  Table  gives  the  amounts  of  starchy  and  extractive  matters  per  100  kilos 
of  various  materials,  together  with  the  theoretical  yields  of  alcohol : 


Wheat      . 

Maize 

Barley 

Rye      ••'.      :    . 

Rice 

Durra 

Green  potatoes 

Dry  potatoes     . 


Starchy  and  extrac- 
tive matters 

65-68  kilos 

62-67  „ 

63-65  „ 

66-69  „ 

78-82  „ 

61-64  „ 

18-20  „ 
68-70 


Alcohol 

32-44  kilos 

31-33  „ 

30-32  „ 

34-35  „ 

39-43  „ 

30-32  „ 

10-12  „ 
34-35 


In  washed  potatoes  the  starch  is  calculated  from  their  specific  gravity  (vol.  i,  pp.  72 
and  107).1 

In  cereals  and  potatoes  the  content  of  starch  can  be  determined  as  follows  :  200  grms. 
of  potatoes  (75  grms.  of  ground  cereal)  are  heated  in  a  flask  with  600  c.c.  of  water  and 
10  c.c.  of  hydrochloric  acid  (sp.  gr.  1-2  =i  4-7  grms.  HC1)  for  ten  hours  at  90°,  the  volume 
made  up  to  1  litre  and  3-5  grms.  of  HC1  neutralised  with  caustic  soda  (leaving  1  grm. 
free)  ;  the  whole  is  poured  into  a  larger  flask,  a  few  grammes  of  beer-yeast  being  added 
and  the  flask  kept  at  25°  for  2  or  3  days  until  the  fermentation  is  over,  when  half  of  the 


Specific 

Per 

Specific 

Per 

Specific 

Per 

Specific 

Per 

gravity  of 

cent,  of 

gravity  of 

cent,  of 

gravity  of 

cent,  of 

gravity  of 

cent,  of 

potatoes 

starch 

potatoes 

starch 

potatoes 

starch 

potatoes 

starch 

1-070 

11-5 

1-088 

15-6 

1-106 

19-4 

1-125 

23-5 

1-072 

11-9 

1-090 

16-0 

1-108 

19-9 

1-127 

24-0 

1-074 

12-5 

1-092 

16-4        i|         1-110 

20-3 

1-129 

24-5 

1-077 

13-1 

1-094 

16-9 

1-113 

20-9 

1-134 

25-E 

1-079 

13-7 

1-097 

17-5 

1-115 

21-4 

1-139 

26-f 

1-081 

14-1 

1-099 

17-9 

1-118 

22-0 

1-144 

27-6 

1-083 

14-5 

1-101 

18-4 

1-120 

22-5 

1-149 

28-7 

1-085 

14-9 

1-103 

18-8                  1-122 

22-9 

1-150 

28-9 

(To  15  per  cent,  of  starch  corresponds  20-8  per  cent,  of  dry  matter  in  the  potato ;  to  20  per  cent,  of  starch 
25-8  per  cent,  of  dry  matter  ;  and  to  25  per  cent,  of  starch  30-8  per  cent,  of  dry  matter). 


118 


ORGANIC    CHEMISTRY 


liquid  is  distilled  and  the  alcohol  estimated  in  the  distillate  by  means  of  the  specific  gravity. 
100  kilos  of  starch  yield  practically  63-5  litres  of  alcohol.1 

The  fresh  potatoes  are  washed  free  from  stones  and  earth  in  an  Eckert  mechanical 
washer  (Pig.  103),  passing  first  into  a  rotating  sieve,  E,  which  removes  the  stones  and, 
by  means  of  the  blades,  F,  carries  the  potatoes  into  the  tank,  A,  through  which  water 
flows  and  in  which  they  are  stirred  by  the  vanes,  C,  fixed  to  a  rotating  axis  ;  the  latter 
is  inclined  in  such  a  way  that  the  potatoes  are  gradually  forced  to  the  far  end  of  the  tank 
where  a  rotating  disc,  furnished  with  perforated  blades,  collects  them  and  removes  them 
from  the  tank.  An  elevator  raises  them  to  the  opening  of  a  Pauksch's  improved  form 
of  the  conical  Henze  autoclave  (Fig.  104),  which  is  made  of  sheet-iron,  has  a  volume  of 
2500-3000  litres,  and  takes  about  1500-3000  kilos  of  potatoes  ;  in  this  they  are  treated 
for  an  hour  or  more  with  steam  at  2-5  to  3-5  atmos.  pressure.  Such  an  apparatus  can 
also  be  used  for  treating  maize  and  other  cereals,  and  gives  a  much  denser  wort  than  was 
previously  obtained  when  steam  at  100°  was  used  ;  in  addition,  it  effects  a  better  dis- 
solution of  the  starch,  and  is  of  advantage  to  manufacturers  in  countries  where  the  alcohol 
tax  is  based  on  the  volume  of  wort  fermented  (or  of  the  fermenting  vats).  The  steam  is 
passed  in  at  the  top  by  the  tube  b,  and  is  distributed  uniformly  over  the  interior  by  means 

of  a  perforated  pipe  (shown  dotted 
at  c),  the  tap,  g,  at  the  bottom 
being  left  open  to  discharge  the 
condensed  water.  When  the  whole 
mass  is  hot,  steam  begins  to  issue 
from  this  tap  and  drives  out  all 
the  air.  The  tap  is  then  shut,  and 
the  pressure,  shown  by  the  mano- 
meter, e,  soon  rises  to  3  atmos. 
After  about  45  minutes  at  this 
~^;  pressure  (temperature  135°),  the 
conversion  is  complete.  With 
damaged  or  frozen  potatoes,  the 
steam  is  allowed  to  issue  for  an 
hour  from  the  tap,  g,  before  raising 
the  pressure,  and  steam  is  then  passed  in  by  the  pipe  V  as  well.  A  pressure  higher 
than  3  atmos.  turns  the  mass  brown,  owing  to  the  caramelisation  of  the  maltose.  To 
discharge  the  apparatus,  the  pressure  is  maintained  at  its  maximum  and  connection 
made  with  the  discharge  pipe,  i,  by  opening  the  valve,  h.  At  the  bottom  of  the  cone, 
just  above  k  is  a  horizontal  disc  of  cutting  grids,  through  which  the  whole  of  the  mass 
is  forced  by  the  steam -pressure  and  thus  converted  into  a  paste  ;  the  pipe  i  carries 

1  Witte  (1904)  gives  the  following  improved  modification  of  the  Baumert  and  Bode  method  for  estimating 
the  starch  in  cereals  :  1-2  grms.  of  the  meal,  sieved  and  mixed  to  a  paste  with  water,  are  heated  with  60-70  c.c. 
of  water  under  4  atmos.  pressure  (145°)  in  a  Lintner  bottle  or  other  vessel  for  two  hours — in  an  oil-bath.  After 
being  allowed  to  cool  partially,  the  whole  is  introduced  into  a  flask  and  boiled  for  10  minutes  with  a  few  grains 
of  zinc.  When  cool,  the  liquid  is  made  up  to  a  volume  of  500  c.c.  and  filtered  through  a  thin  layer  of  asbestos. 
To  50  c.c.  of  the  filtrate  are  added  5  c.c.  of  10  per  cent,  caustic  soda  solution,  about  1  grm.  of  shredded  asbestos 
and  100  c.c.  of  96  per  cent,  alcohol ;  the  whole  is  well  shaken  and  then  allowed  to  settle,  when  the  liquid  is 
decanted  through  an  asbestos  filter-tube  (Allihn) ;  the  deposit  is  also  washed  on  to  the  filter  with  40  c.c.  of  60  per 
cent,  alcohol,  and  is  washed  successively  with  40  c.c.  of  60  per  cent,  alcohol,  a  mixture  of  25  c.c.  96  per  cent,  alcohol, 
10  c.c.  of  water,  and  5  c.c.  of  10  per  cent.  HC1,  a  further  40  c.c.  of  60  per  cent,  alcohol,  25  c.c.  96  per  cent,  alcohol,  and 
finally  with  a  little  ether.  After  being  well  pumped  off,  the  tube  with  the  starch  is  dried  at  120°  in  a  current  of 
dry  air  for  twenty  minutes,  cooled,  and  weighed.  By  heating  the  tube  to  redness  in  a  current  of  air  the  starch  is 
burnt  away,  and  its  weight,  when  cool,  subtracted  from  the  original  weight,  leaves  that  of  the  starch  corresponding 
with  50  c.c.  of  the  solution  ;  multiplication  by  10  gives  the  amount  of  starch  in  the  meal  originally  weighed  out. 

When  starch  is  to  be  determined  in  materials  free  from  cellulose,  dextrin,  and  other  substances  which  give 
reducing  substances  (pentoses,  &c.)  with  acids,  the  following  method  (Marcker  and  Morgen)  should  be  used  : 
3  grms.  of  the  substance,  mixed  with  200  c.c.  of  hot  water,  are  treated  with  15  c.c.  of  hydrochloric  acid  (sp.  gr. 
1-125)  for  2J  hours  in  a  flask  immersed  in  a  boiling  water-bath  and  fitted  with  a  simple  reflux  tube  1  metre  in 
length.  The  cooled  liquid  is  almost  neutralised  with  caustic  soda  (it  must  be  left  faintly  acid)  and  made  up  to 
500  c.c.,  the  amount  of  glucose  in  25  c.c.  being  then  determined  by  means  of  Fehling's  solution  (see  p.  186).  The 
quantity  of  starch  is  obtained  by  multiplying  the  amount  of  glucose ^by  0-9. 

For  spirit  manufacture,  where  all  materials  giving  fermentable  substances  are  of  importance,  the  new  method 
given  by  Reinke  is  employed  :  3  grms.  of  the  amylaceous  material  is  heated  in  a  Lintner  bottle  with  30  c.c.  of 
water  and  25  c.c.  of  1  per  cent,  lactic,  acid  solution  for  two  hours  at  135°.  The  liquid  is  then  cooled  to  70-80°, 
shaken  with  50  c.c.  of  hot  water,  cooled  to  the  ordinary  temperature,  made  up  to  250  c.c.,  shaken  several  times 
during  the  course  of  half  an  hour,  and  filtered.  200  c.c.  of  the  filtrate  are  heated  with  15  c.c.  of  hydrochloric 
acid^(sp.  gr.  1-125)  for  two  hours  in  a  reflux  apparatus  immersed  in  a  boiling  water-bath.  The  cooled  liquid  is 
near/i/,'neutralised  and  made  up  to  a  volume  of  500  c.c.,  25  c.c.  being  then  titrated  with  Fehling's  solution.^as 
above. 


FIG.  103. 


CONVERTERS 


119 


it  to  the  coolers  and  then   to   the   wort  vessels,  where  suitable  stirrers  complete  the 
gelatinisation  of  the  mass. 

In  order  to  avoid  danger  of  explosion,  the  Henze  autoclaves  should  be  tested  once  a 
year  to  ascertain  if  they  are  capable  of  withstand- 
ing the  pressure  employed,  since  they  may  become 
weakened  at  rusted  parts. 

Maize,  rice,  and  cereals  are  also  treated  in  the 
Henze  apparatus,  but  with  the  addition  of  110-140 
kilos  of  water  per  100  kilos  of  cereals,  since  these 
contain  less  water  (15  per  cent.)  than  potatoes  (75 
per  cent. ),  and  without  the  water  the  desired  fluidity 
of  the  starch  would  not  be  obtained.  The  volume 
of  the  autoclave  is  350  litres  per  100  kilos  of  maize. 
If  a  pressure  of  5  atmos.  cannot  be  easily  attained 
in  the  autoclave,  instead  of  using  the  whole  grain, 
it  is  better  to  crush  or  grind  it  coarsely  and  then 
introduce  it  into  the  necessary  quantity  of  boiling 
water  in  the  autoclave.  During  the  boiling,  the 
maize  should  be  kept  in  continual  motion  by  steam- 
jets  at  the  bottom  and  along  the  autoclave,  or  by 
an  air-jet  at  the  bottom  with  an  outlet  at  the  top, 
so  that  a  spiral  motion  is  imparted  to  the  mass 
(Fig.  105).  Only  rarely  are  mechanical  stirrers 
employed  inside  the  autoclave.  After  an  hour's 
heating  the  pressure  reaches  2^  atmos.  and  is 
raised  to  3  atmos.  in  another  hour.  The  mass  is 
then  discharged  in  the  usual  way. 

Maize  that  is  too  dry  is  steeped  in  water  for  a  day  before  boiling. 

Maize  always  contains  a  little  ready  formed  sugar  (1-7  to  10  per  cent.),  and  this  must 
be  allowed  for  in  calculating  the  yield  and  also  in  order  to  avoid  a  too  protracted  heating, 


FIG.  104. 


FIG.  105. 


FIG.  106. 


which  caramelises  the  wort  and  injures  it  by  decomposing  the  large  proportions  of  fat 
present. 

Saccharification  is  effected  by  means  of  malt  (2-5  to  3  percent,  on  the  weight  of  maize) 
added  to  the  starchy  mass  at  a  concentration  of  about  14°  Be.  and  cooled  to  about 
50°  ;  if  it  is  too  cold,  it  coagulates  and  the  diastase  acts  irregularly  ;  at  35-40°  the  lactic 
fermentation  readily  takes  place  ;  above  65°  to  70°  the  diastase  is  altered  and  rendered  less 
active,  dextrin  being  then  formed  in  preference  to  maltose.  The  paste  from  the  Henze 
autoclave  is  cooled  in  various  ways,  e.g.  with  Ellenberg's  apparatus  (Figs.  106  and  107), 
in  which  it  is  dropped  from  the  top  of  a  pipe  into  a  vessel  similar  to  the  Hollanders 
used  in  paper  factories  (see  Paper),  where  it  is  mixed,  cooled,  and  broken  up  by  a  rotating 
drum,  T,  fitted  with  knives  which  graze  other  knives  fixed  to  an  inclined  plate,  d,  at  the 


120 


ORGANIC    CHEMISTRY 


bottom  of  the  vessel  ;  the  drum  makes  200  revolutions  per  minute  ;  above  the  pipe  by 
which  the  paste  enters  is  a  Korting  injector,  e,  which  produces  a  strong  current  of  air 
and  thus  facilitates  the  cooling  of  the  paste  during  its  fall. 

At  the  present  time  preference  is  given  to  apparatus  with  centrifugal  stirrers,  the 
cooling  and  ako  the  saccharification  being  carried  out  in  these.  Fig.  108  shows  the 

Hentschel  apparatus.  The  hot  starch -paste 
from  the  Henze  converter  passes  through  the 
pipe  6  into  the  vessel  A,  where  it  is  cooled 
by  water  flowing  from  m  to  n  through  an 
internal  coil ;  the  mass  is  mixed  by  means  of 
a  kind  of  screw,  B,  rotated  by  bevel -wheels 
outside  the  vessel  and  the  air-draught  is  pro- 
duced by  the  Korting  injector,  r.  Fig.  109 
shows  a  section  of  the  Pauksch  masher,  in 
which  the  cooling  is  effected  by  means  of  water 
circulating  through  the  jacket,  C,  surrounding 
the  vessel,  the  liquid  being  mixed  by  four 
blades,  p,  which  are  rapidly  rotated  (300  revolutions  per  minute)  by  the  pulley,  S,  and, 
as  they  graze  the  bottom  of  the  vessel,  have  also  a  grinding  action.  A  battery  of  Henze 
autoclaves  is  sometimes  used  in  conjunction  with  one  masher. 

Since,  during  this  saccharification,  which  may  last  three  or  four  hours  (and  is  complete 
when  a  test  of  the  liquid,  how  very  fluid,  no  longer  gives  the  blue  starch  reaction  with 
iodine  solution),  the  mass  may  become  infected  with  extraneous  bacteria,  which  may 
have  a  harmful  influence  during  the  alcoholic  fermentation  of  the  wort,  it  is  usually  heated 


FIG.  107. 


FIG.  108. 


FIG.  109. 


for  a  few  minutes  at  70-75°  to  kill  these  germs.  This  procedure  has,  however,  the 
disadvantage  of  destroying  the  diastase,  which  can  always  play  a  part  during  the 
fermentation,  and  of  increasing  thje  quantity  of  dextrin. 

In  the  Effront  process  (see  later),  the  fermentation  is  carried  out  in  presence  of  hydro- 
fluoric acid,  which  kills  all  the  bacteria  but  not  the  enzymes  (previously  acclimatised  to 
the  hydrofluoric  acid),  so  that  the  saccharification  can  be  effected  at  the  most  favourable 
temperature  (55°)  without  subsequently  heating  to  75°. 

As  soon  as  the  saccharification  is  terminated,  the  wort  should  be  cooled  to  about  20°, 
and  the  fermentation  started.  This  cooling  may  be  accomplished  in  the  masher,  with 
suitable  internal  coolers  (Fig.  108),  but  it  is  better  done  in  appropriate  apparatus. 

One  form  of  horizontal  Hentschel  refrigerator  is  shown  in  Fig.  111.  The  horizontal 
rotating  axis  (40-50  turns  per  minute)  is  formed  of  a  tube,  to  which  is  fastened  a 


FERMENTATION 


121 


deep  screw  and  in  which  cold  water  circulates  from  h  to  k.  The  screw  moves  in  a  horizontal 
cylinder  through  which  the  hot  wort  is  forced  by  the  screw  in  a  direction  (b  to  /)  opposite 
to  that  taken  by  the  water  ;  the 
temperature  of  the  wort  at  the 
outlet,  /,  is  controlled  by  regu- 
lating the  flow  of  wort  and 
water,  and,  if  necessary,  by  spray- 
ing the  exterior  of  the  cylin- 
der with  water  by  means  of  the 
tube  I.  With  700  c.c.  of  water, 
.a  litre  of  wort  is  cooled  from  60° 
to  16°. 

To  separate  the  solid  residue, 
husks,  &c.  (grains),  from  the  wort, 
the  latter  is  filtered  cold  through 
dehuskers,  which  have  different 
forms,  some  fixed  and  some  re- 
volving. The  most  recent  Pauksch 
type  consists  of  a  kind  of  centri- 
fuge (hydro-extractor)  with  a  fine 
copper  gauze  basket,  almost  like 
the  centrifuges  used  in  sugar  fac- 
tories (see  Sugar). 

Brewers  and  distillers  often 
use  also  ^  the  Hentschel  dehusker 
(Fig.  112  and  113),  consisting 
simply  of  a  rotating  drum,  with 
a  spiral  of  metal  gauze,  which 

carries  the  drained  grains  to  the  middle  and  discharges  it  in  cakes  through  doors  which 
close  automatically  ;  the  liquid  flows  to  the  bottom  and  passes  to  the  fermenting  vessels. 


FIG.  110. 


FIG.  111. 


FIG.  112. 


ALCOHOLIC  FERMENTATION.  Industrially  the  transformation  of  saccharine 
worts  into  alcoholic  liquors  is  always  effected  by  means 
of  organised  ferments  (or  yeasts).  Worts  left  exposed 
to  the  air  at  15-30°  ferment  spontaneously,  but,  owing 
to  the  different  species  of  bacteria  present,  not  only 
alcoholic  fermentation,  but  also  harmful  secondary  fer- 
mentations, such  as  the  acetic,  lactic,  butyric,  &c.  (the 
corresponding  bacteria  are  shown  in  Fig.  114),  develop. 

Owing  to  the  studies  of  Rees  and  more  especially  of 
Hansen,  it  is  nowadays  admitted  by  everybody  that  the 
principal  agent  of  alcoholic  fermentation  is  Saccharomyces 
cerevisice  (Fig.  115,  a,  b,  and  c),  a  fungus  that  multiplier; 
by  budding  and  has  varying  dimensions  (2-5-10  p)  and 
appearance  according  as  it  develops  at  the  surface  (Fig- 
116)  or  in  the  body  of  the  wort  (Fig.  117).  In  Fig.  118  is  represented  a  cell  of  the 
ferment  magnified  4000  times  and  showing  the  granulations,  vacuoles,  protoplasm, 


FIG.  113. 


122  ORGANIC    CHEMISTRY 

cell-wall,  &c.  In  spirit  distilleries,  a  mixture  of  two  varieties  of  yeast  (top-  and  bottom- 
yeasts)  is  used,  these  being  of  the  same  race  but  not  interconvertible  ;  often  top-yeast  is 
preferred,  as  it  is  more  active,  whilst  in  lager-beer  breweries,  where  the  fermentation 
is  slow,  bottom-yeast  is  mostly  used. 

The  final  result  of  the  decomposition  of  maltose  by  yeast  can  be  expressed  thus : 
Ct2H22Ou  +  H20  =  4C2H5-OH  +  4CO2  ; 


(a)  Acetic  bacteria 


FIG.  114. 
(b)  Lactic  bacteria 


(c)  Butyric  bacteria 


actually,  however,  the  maltose  and  dextrin  formed  from  the  starch  are  transformed  into 
glucose  by  the  action  ,of  the  maltase  contained  in  the  ferment  along  with  the  zymase, 
the  latter  then  converting  95  per  cent,  of  the  glucose  into  alcohol  and  carbon  dioxide 


FIG.  115. 

with  the  development  of  heat  (if  the  glucose  were  transformed  completely  into  H20  +  C02, 
the  evolution  of  heat  would  be  seven  times  as  great) : 

C6H1206  (glucose)  =  2C2H5-OH  +  2CO2  +  33,000  cals. 


FIG.  116. 


FIG.  117. 


A  small  part  of  the  sugar  serves  for  the  growth  and  multiplication  of  the 
yeast  (Pasteur),  about  3  per  cent,  of  it  is  converted  into  glycerol,1  about 
0-5  per  cent,  into  succinic  acid,  and  the  remainder  into  higher  alcohols  forming 
fusel  oil,  this  consisting  mostly  of  amyl  alcohol  (C5Hn-OH,-  isobutylcarbinol) , 
with  small  proportions  of  isopropyl  alcohol,  butyl  alcohols,  and  esters.  Ehrlich 

1  The  formation  of  glycerol  during  fermentation  has  not  yet  been  explained  ;  it  is  thought  that  it  forms  a 
direct  secondary  product  from  the  decomposition  of  the  sugar  into  alcohol  and  CO2,  or  that  it  results  from  the 
action  of  lipase  on  the  fats  and  oils  of  the  ferment  cells  ;  Buchner  (1906)  holds  that  it  is  formed  from  the  sugar 
but  by  a  special  process  ;  Reisch  (1907),  however,  finds  no  relation  between  the  amounts  of  alcohol  and  glycerol 
formed  and  hence  regards  it  not  as  a  product  of  fermentation,  but  rather  as  a  metabolic  product  of  the  yeast. 


YEAST 


123 


(1909)  has  shown,  however,  that  fusel  oil  and  succinic  acid  are  formed  by  the 
decomposition  of  the  amino-acids  which  constitute  the  cells  of  the  ferment. 
The  theoretical  yields  of  pure  alcohol  from  various  sugars  are  as  follow  : 

100  grms.  of  saccharose  C12H220U  —  51-11  grms.  or  64-6  c.c.  of  alcohol 
,,         „      maltose       C12H22On —  51-11         ,,        64-6       „         ,, 
„     starch         (C6H1005),—  56-80        „        71-8 
.,     glucose        C6H1206    —48-67         „        61-6 

Various  sugars,  however,  do  not  ferment  directly  (saccharose,  lactose,  &c.), 
but  must  first  be  inverted,  that  is,  transformed  into  hexoses  (fermentable 
sugars  with  six  carbon  atoms),  but  ordinary  alcoholic  ferments  (saccharo- 
mycetes)  contain  the  inverting  enzymes  (besides  zymase)  and  hence  can  effect 
inversion  and  then  fermentation.1 

The  fermentation  industries  in  general,  and  the  alcohol  industry  in  particular,  have 
made  marked  progress  since  the  introduction  of  pure  ferments.  The  cultivation  of  pure 


FIG.  119. 


FIG.  118. 


FIG.  120. 


FIG.  121. 


ferments  has  at  the  present  time  become  a  special  industry  of  great  importance  ;  all 
precautions  are  taken  to  select  and  cultivate  well-defined  races  of  ferments,  and  this  is 
especially  owing  to  Hansen  of  Copenhagen,  who,  by  thirty  years  of  study  and  experiment, 
showed  the  great  practical  value  of  the  selection  of  yeasts.  The  first  pure  culture  is 
made  in  a  moist  chamber  of  glass,  c  (Fig.  119),  fixed  on  a  microscope  slide,  a  ;  the  whole 
is  sterilised,  either  by  a  flame  or  by  heating  for  two  hours  in  an  oven  at  150°.  Sterilised 
water  is  placed  on  the  bottom  of  the  chamber  to  keep  the  atmosphere  moist,  and  the 
chamber  placed  in  an  incubator  at  30°  to  35°.  The  bacterial  culture  is  developed  in  a  drop 
of  gelatine,  b,  adhering  to  the  lower  side  of  the  cover -glass  covering  the  chamber. 

The  culture  of  pure  ferments  can  also  be  carried  out  in  Chamberland  flasks  of  30  c.c. 
capacity  (Fig.  120),  half  filled  with  nutrient  gelatine  and  fermentable  substances,  and 
covered  with  a  glass  cap  full  of  sterilised  cotton-wool. 

The  more  or  less  pure  ferment  which  it  is  desired  to  cultivate  is  introduced  by  means 
of  a  sterile  platinum  wire  into  a  flask  containing  sterile  water,  which  is  well  mixed  and 
should  become  just  turbid.  A  drop  of  this  water  is  then  examined  under  the  microscope 
in  order  to  ascertain  the  number  of  cells  of  the  ferment  it  contains.  By  means  of  a 
platinum  wire  sterilised  in  a  flame,  a  drop  of  the  water  is  introduced  into  a  Chamberland 

1  According  to  Boysen-Jensen  (1909)  the  zymaae  of  alcoholic  ferments  is  constituted  of  two  enzymes  :  deztrase 
and  dihydroxyacetonase,  glucose  first  forming  2  mols.  of  dihydroxyacetone  OH  •  CH2-  CO  •  CH,-  OH  (triose),  which  to  a 
small  extent  can  be  fixed  in  the  form  of  oxime  or  hydrazone  (which  see)  by  means  of  hydroxylamine  hydrochloride 
or  methylphenylhydrazine  acetate ;  the  dihydroxyacetonase  then  decomposing  the  dihydroxyacetone  into  2CO2 
and  2C2H6OH.  The  dextrase  alone  would  give  directly  alcohol  and  CO2  if  glycerol  were  added  to  the  solution 
of  glucose.  With  zymase  (which  contains  dihydroxyacetonase),  pure  dihydroxyacetone  gives  alcohol  and  CO2, 
whilst  with  oxydase  it  gives  only  CO,. 


124 


ORGANIC    CHEMISTRY 


flask  containing  liquefied  gelatine  at  35°.  After  the  latter  has  been  well  shaken,  a  drop 
of  the  gelatine  is  examined  microscopically  on  a  glass  micrometer  (marked  with  crossed 
lines)  to  see  that  there  are  not  too  many  rr  too  few  cells  present,  since  the  colonies  that 
ultimately  develop  from  the  single  cells  should  develop  sufficiently  far  apart  from  one 
another  not  to  mingle.  Of  this  inoculated  gelatine,  one  or  more  drops  are  placed  on  the 
cover-glass  of  the  moist  chamber,  this  being  kept  under  a  bell-jar  until  the  gelatine  has 
solidified  and  then  placed,  upside  down,  in  the  chamber.  In  a  thermostat  at  25°,  the 
ferments  are  usually  sufficiently  developed  after  two  or  three  days  and  the  various  colonies 
are  then  examined  under  the  microscope  to  ascertain  if  one  or  more  of  them  are  pure, 
that  is,  constituted  of  similar  cells  of  one  and  the  same  ferment.  Each  of  the  pure  colonies 
is  touched  separately  with  a  small  piece  of  sterilised  platinum  wire,  which  is  immediately 
dropped  into  a  Pasteur  flask  (125  c.c.)  charged  to  the  extent  of  two-thirds  with  gelatine 
and  nutritive  substances  (Fig.  121),  the  rubber  tube  being  momentarily  removed.  The 
flask  is  at  once  closed  again,  and  is  then  kept  in  a  thermostat  at  25°  to  28°.  After  2  days 

the  liquid  will  be  in  a  state  of  active 
fermentation,  a  large  quantity  of  the 
ferment  having  been  formed.  Each 
of  these  flasks  represents  a  pure 
culture  (provided  that  the  proper 
precautions  have  been  taken  in  the 
inoculation).  All  the  cultures  are, 
however,  examined,  one  or  two  drops 
from  each  flask  being  observed  under 
the  microscope. 

These  pure  yeasts  or  other  pure 
ferments  are  largely  used  by  brewers 
or  distillers,  who  have  ferments 
suited  to  then-  needs  selected  and 
preserved  by  scientific  institutions, 
from  which  cultures  in  Pasteur 
flasks  are  despatched  to  them  when 
FIG.  122.  the  organisms  in  their  own  ferment- 

ing vessels  begin    to   degenerate  or 

become  contaminated.  In  Fig.  122  is  shown  diagrammatically  an  apparatus  for 
the  industrial  preparation  of  selected  ferments  ;  the  metal  reservoir,  C,  provided 
with  a  safety-valve,  q,  and  a  manometer,  r,  is  filled,  by  means  of  the  pump,  u, 
with  air  filtered  through  a  cotton-wool  filter,  t,  and  compressed  under  a  pressure 
of  3  to  4  atmos.  The  vessel,  A,  is  first  sterilised  with  steam  under  pressure,  which 
enters  at  the  tap,  /,  whilst  the  air  is  driven  out  through  the  tube,  b,  dipping  into  a 
vessel  of  mercury  forming  a  seal.  When  the  cock,  /,  is  shut,  g  is  opened  so  as  to 
allow  air  to  filter  through  d  into  A.  Hot  wort  is  introduced  into  the  reservoir,  A, 
heated  to  boiling  and  then  cooled  by  means  of  a  water-spray  issuing  from  an  annular 
tube,  e,  and  bathing  the  outside  of  A.  The  fermenting  vessel,  B,  which  is  sterilised  in  the 
same  way  as  A,  is  also  furnished  with  a  cotton -wool  filter,  h,  and  a  hydraulically  sealed 
tube,  ip,  through  which  the  C02  is  to  escape  ;  the  glass  tube,  O,  which  is  a  continua- 
tion of  the  filter,  indicates  the  level  of  the  liquid  inside  the  vessel.  It  is  further  provided 
with  a  vertical  stirrer  which  is  set  in  motion  by  the  handle,  k,  and  serves  to  mix  the  wort 
and  yeast  which  are  introduced  through  the  small  tap,  I.  A  slight  air-pressure  is  main- 
tained in  both  A  and  B  in  order  to  prevent  external  contaminated  air  from  entering 
either  when  the  discharge-cock,  m,  for  the  fermented  wort  is  opened  or  through  any  leaks 
there  may  be  in  the  apparatus.  In  this  way  B  can  be  used  for  a  year  or  more  without 
contamination  taking  place,  a  little  residual  yeast  being  left  after  each  operation  to  ferment 
the  succeeding  charge  of  wort.  The  sterile  wort,  cooled  to  15°,  is  passed  from  A  into 
B  by  means  of  the  tube,  a  n,  and  before  it  reaches  the  level  of  the  tap,  I,  the  pure  yeast 
contained  in  a  Pasteur  flask  is  introduced  through  this  tap  ;  B  is  filled  to  the  extent  of 
about  three-fourths  (about  200  litres)  with  the  wort  from  A,  the  whole  being  then  well 
mixed.  When  the  fermentation  is  ended  (in  three  or  four  days  with  worts  for  alcohol 
production,  or  in  8  to  10  days  for  beer  worts),  the  yeast  is  allowed  to  deposit  ;  the 
fermented  wort  is  discharged  from  m  by  increasing  the  pressure  of  the  air  and,  when  it 


CULTIVATION    OF    PURE    YEAST  125 

begins  to  issue  turbid  (owing  to  suspended  j  east),  m  is  closed  and  about  30  litres  of  wort 
introduced  from  A  and  well  mixed  in,  30  litres  of  the  turbid  yeasty  liquid  being  then 
run  off  from  B,  this  amount   being  sufficient  to   induce  fermentation  in  40  hectols.  of 
wort  in  the  ordinary  fermenting  vessels  ;  a  further  quantity  of  30  litres  of  wort  is  then 
run  in  from  A  and,  after  mixing,  another  30  litres  of    yeasty  wort  drawn  off.      That 
remaining  in  B  serves  for  the  next  operation.     This  is  the  procedure  adopted  in  large 
breweries  and  distilleries  ;    whilst  in    yeast-factories  the  wort  is  prepared  from  barley 
and  rye  under  the  action  of  malt  for  an  hour  at  60°  and  for  about  24  hours  at  40°  to 
44°  in  order  to  produce  about  1  per  cent,  of  lactic  acid,  which  peptonises  the  proteins 
and  so  affords  better  nutriment  for  the  yeast,  the  action  being  completed  by  the  addition 
of  10  grms.  of  sodium  or  ammonium  phosphate  per  hectolitre  of  wort.     The  wort  is  then 
fermented  as  above  at  18°  to  20°, 
and  the  yeast,  which  is  formed  in 
large  quantity,  is  washed  with  water 
by  decantation,  freed  from  excess  of 
water  in  centrifuges  or  filter-presses 
and  made  into  a  paste  with  5  to  10 
per  cent,  of  potato -starch,  forming 
cakes   which   are   sold   under  the 
name    of    pressed   yeast   at    about 
£3  12s.  per  quintal  (220  lb.).      100 
kilos  of  rye  yield  16  kilos  of  yeast. 
In    Germany   more    than    210,000 
quintals  of  pressed  yeast  are  pro- 
duced   annually,    and    10,000    to 
13,000  quintals  exported;    in  five 
factories  alone  more  than  110,000 
quintals   were  made  in   1909.     In 
Italy,  1361  quintals  were  imported 
in  1905 ;  2000  in  1906 ;  3500  in  1907 ; 
4500  in  1908;  in  1909,  5300_  quin- 
tals, of  the  total  value  of  £21,700 
(including  2000  quintals  of  diamalt 
or  liquid  malt  worth  £10,700) ;  and 
in  1910,  4750  quintals,   including 
1137  of    diamalt.     Certain  of  the 
French  factories  export  as  much  as 
30  or  40  quintals  of  pressed  yeast  per 
day.  In  Austria,  the  law  of  May  18, 
1910,  regulates  the  trade  in  yeast  so  as  to  prevent  adulteration  and  mixture.1     In  France 
and  latterly  in  Italy,  industrial  spirit  distillers  are  making  use  of  the  Jacquemin  apparatus 
(Fig.  123)  for  the  preparation  of  pure  yeast  cultures.     The  peptonised  wort  is  prepared 
as  described  above,  and  the  sterilised  air,  compressed  by  the  pump  A,  passes  through  a 
filter  of  cotton-wool  moistened  with  mercuric  chloride,  F,  into  a  battery  of  vessels,  G,  tho 
first  and  third  of  which  are  empty,  whilst  S  contains  sulphuric  acid  and  n  soda  solution  ; 

1  Yeast  Manufacture.  Not  only  in  Austria,  but  also  in  Germany,  the  yeast  industry  has  lately  assumed 
great  importance,  especially  in  spirit  factories.  It  has  given  rise  to  special  legislation  and  has  led  to  the 
formation  of  powerful  syndicates  to  regulate  prices  and  production.  The  largest  consumers  are  the  bakers. 

At  one  time,  with  a  yield  of  30  to  32  per  cent,  of  alcohol  on  the  weight  of  cereal  used,  the  amount 
of  yeast  obtained  was  12  to  14  per  cent.  During  recent  years  a  marked  increase  has  been  effected  in  the  quantity 
of  yeast  (up  to  20  per  cent.),  the  yield  of  alcohol  being  diminished  by  vigorous  aeration  of  the  wort  during  fer- 
mentation (30  to  40  cu.  metres  of  air  per  hour  for  every  100  kilos  of  cereals  converted  into  wort).  By  the  new 
Braasch  process  the  yield  of  yeast  can  be  raised  to  40  per  cent,  and  that  of  alcohol  lowered  to  15  per  cent,  (under 
some  conditions  of  the  market  the  production  of  yeast  is  more  remunerative  than  that  of  alcohol).  The  value 
of  yeast  in  Germany  is  calculated  at  about  £3  16*.  to  £4  per  quintal,  and  some  factories  produce  as  much  as 
5000  to  10,000  quintals  per  annum  ;  the  alcohol  is  valued  at  £1  8«.  per  hectolitre. 

In  the  old  Vienna  process,  worts  of  10°  to  20°  Balling  (or  even  heavier)  were  fermented  by  means  of  yeasts  pre- 
pared with  worts  rich  in  lactic  acid  (100  c.c.  of  this  wort  should  require  12  to  14  c.c.  of  normal  sodium  hydroxide 
solution  for  neutralisation).  When  the  fermentation  was  complete,  the  yeast  was  collected  by  means  of  ladles 
and  despatched  along  channels  into  vats,  where  its  activity  was  arrested  with  cold  water.  After  this,  it  was 
shaken  on  silk  sieves,  which  retained  all  the  husks  or  grains  ;  the  yeast  passing  through  the  sieves  was  washed 
two  or  three  times  with  water  and,  after  settling,  pressed  into  cakes.  In  1887-1890  all  yeast  factories  worked 
on  this  plan,  but  nowadays  only  few  of  them  do  so. 

The  new  aeration  process  starts  from  clear  wort  and  green  malt  (non-kilned).     The  cereals  for  preparing  the 


FIG.  123. 

Vapeur,  steam;  eau,  water;  laveurs  d'air,  air-washers; 
filtre  a  air,  air-fllter 


126  ORGANIC    CHEMISTRY 

the  empty  vessels  serve  as  safeguards,  in  case  the  liquids  are  sucked  backwards.  The 
air  sterilised  in  this  way  passes  along  suitable  pipes  to  all  the  ^fermenting  vessels, 
B,  B',  G,  C',  D.  B  is  two-thirds  filled  with  the  peptonised  wort  (20  to  30  litres),  which  is 
boiled  for  a  few  minutes  by  steam  entering  through  b  and  then  cooled  by  passing  a  vigorous 
current  of  air  through  the  wort  and  by  an  annular  spray  of  water  applied  to  the  outside 
of  the  vessel  B  by  the  tube  e.  When  the  temperature  has  fallen  to  20°,  the  contents 
of  a  Pasteur  flask  of  pure  yeast  are  introduced  through  the  tube  a,  and  the  fermentation 
allowed  to  proceed  for  24  hours  ;  in  the  meantime,  wort  sterilised  and  cooled  to  20°  is 
prepared  in  B'  ;  a  little  of  the  yeast  is  then  passed  from  B  through  the  tube  t  to  B', 
the  remainder  being  discharged,  by  the  three-way  cock,  t,  into  the  larger  vessel,  C,  which 
contains  sterilised  wort  (250  to  300  litres).  When  the  fermentation  has  reached  an 
advanced  stage  (a  definite  attenuation  ;  see  later),  the  wort  is  discharged  through  the  tube  r 
into  D,  which  also  contains  sterilised  wort,  and  that  remaining  on  the  bottom  of  C  is 
forced  by  compressed  air  into  the  vessel  C',  previously  charged  with  sterile  wort. 

It  will  be  seen  that,  by  this  procedure,  the  working  is  continuous,  and  the  yeast  is 
renewed  only  once  .or  twice  per  month.  The  yeast  may  then  be  separated  from  D  and 
pressed,  or  the  actively  fermenting  wort  (5  to  6  hectols.)  may  be  used  to  induce  fermenta- 
tion in  the  factory  vats  containing  ordinary  wort. 

The  selected  yeasts  are  controlled  practically,  by  measuring  then-  fermentative  activity 
and  by  determining  the  concentration  with  the  microscope  and  cell -counters,  note  being 
taken  of  extraneous  organisms. 

Pressed  yeast  in  cakes  keeps  for  several  days  if  well  wrapped  in  paper  and  placed  in 
tightly  closed  boxes  in  a  cool  room  ;  otherwise  it  soon  becomes  covered  with  mould  and 
unusable.  When  the  stock  of  yeast  is  larger  than  is  required,  it  can  be  dried  at  a  cost 
of  a  shilling  per  quintal  and  sold  as  a  good  cattle  food.  To  prevent  secondary  fermenta- 
tions from  taking  place,  instead  of  the  lactic  acid  fermentation,  during  the  preparation 
of  selected  yeasts,  Bucheler  (Ger.  Pat.  123,437)  suggests  the  addition  of  180  c.c.  of 
concentrated  sulphuric  acid  to  every  hectolitre  of  wort ;  the  process  yields  excellent 
results  in  practice,  notwithstanding  the  disputing  of  the  patent  from  1900  to  1909,  owing 
to  the  fact  that  a  similar  patent  (No.  3885)  was  granted  in  Austria  to  Bauer  in  1900. 

FACTORS  WHICH  FACILITATE  OR  RETARD  FERMENTATION.  Alcoholic 
fermentation  may  be  hindered  by  various  factors.  Very  concentrated  sugar  solutions 
do  not  ferment,  whilst  with  a  concentration  of  70  per  cent.,  only  6  per  cent,  of  the  sugar 
is  converted  into  alcohol  ;  with  a  strength  of  60  per  cent.,  25  per  cent,  is  transformed, 
and  when  the  concentration  is  30  per  cent,  it  is  possible,  although  not  without  difficulty, 
to  convert  92  per  cent,  of  the  sugar  into  alcohol. 

Temperature  has  also  a  very  marked  influence  on  alcoholic  fermentation,  and  at  0° 
or  at  60°  it  ceases  completely  ;  later  we  shall  see  at  what  temperature  the  process  takes 
place  most  regularly  from  the  point  of  view  of  the  industrial  yield. 

Alcohol,  although  a  product  of  fermentation,  when  it  reaches  a  certain  concentration, 
may  prevent  further  fermentation.  And  this  an ti -fermentative  action  of  the  alcohols  is, 
to  some  extent,  proportional  to  their  molecular  weights.  Thus  the  fermentation  of 
glucose  can  be  arrested  by  20  per  cent,  of  methyl  alcohol,  16  per  cent,  of  ethyl  alcohol, 
10  per  cent,  of  propyl  alcohol,  2-5  per  cent,  of  butyl  alcohol,  1  per  cent,  of  amyl  alcohol, 
and  0-1  per  cent,  of  capryl  alcohol. 

mash  and  then  the  wort  are  no  longer  ground,  but  are  softened  with  water  and  then  crushed.  The  mashing  of 
the  green  malt  is  carried  out  in  a  medium  slightly  acidified  with  sulphuric  acid,  the  lactic  ferment  (Bacillus 
Delbriickii)  being  allowed  to  act,  after  the  diastase,  for  several  hours  at  40°  to  50°.  When  the  desired  acidity  is 
reached,  further  acidification  is  prevented  by  heating  the  whole  mass  to  68°  to  70°  (the  total  amount  of  sulphuric 
and  lactic  acids,  without  CO2,  corresponds  with  5  c.c.  of  normal  NaOH  per  100  c.c.  of  wort).  The  concentration 
of  the  wort  used  was  at  one  time  12°  to  14°  Balling,  but  at  the  present  time  10°  Balling  is  preferred.  The  tempera- 
ture of  fermentation  is  about  25°.  If  the  acidity  of  the  wort  is  less  than  2  c.c.  of  normal  soda  per  100  c.c.,  the 
yeast  obtained  is  flocculent  and  separates  badly.  The  separation  of  the  yeast  is  now  effected  thoroughly  and 
rapidly  in  centrifuges.  The  fermentation  is  started  by  adding  to  the  wort  4  to  5  per  cent,  of  yeast  (calculated  on  the 
weight  of  cereals  used)  and  is  finished  in  10  to  12  hours  ;  the  yield  of  40  per  cent,  (on  the  weight  of  cereals)  of 
yeast  is  in  addition  to  the  amount  added  (5  per  cent.).  The  yeast  culture's  should  be  renewed  occasionally. 

The  fermented  wort  is  feebly  alcoholic  (less  than  1  per  cent,  of  alcohol),  so  that  the  distillation  and  rectifica- 
tion necessary  to  obtain  90  to  95  per  cent,  alcohol  are  very  expensive  ;  further,  the  alcohol  is  not  of  good  quality 
and  is  hence  only  suitable  for  denaturing.  The  diminished  yield  of  alcohol  is  due  partly  to  loss  of  the  alcohol 
carried  away  by  the  large  volumes  of  air  passed  through  the  wort  and  partly  to  destruction  of  maltose  by  ferments 
or  enzymes  developing  in  presence  of  excess  of  air.  The  less  the  amount  of  air  used,  the  greater  is  the  amount 
of  spirit  obtained. 

In  the  control  of  the  purity  of  the  yeast,  account  must  be  taken  of  the  extraneous  ferments,  of  the  quantity 
of  starchy  substances  (when  starch  is  not  added  this  does  not  reach  4  per  cent.)  and  of  the  fermentative  activity. 


ANTISEPTICS    AND    FERMENTATION      127 

ANTISEPTICS,  in  general,  prevent  fermentation  when  they  are  present  in  relatively 
great  concentrations  ;  they  may,  if  their  dilution  is  great,  exert  a  favourable  influence 
on  fermentation.1 

However,  since  the  favourable  action  exhibited  by  these  solutions  depends  on  the 
quantity  of  yeast  present  and  that  of  the  antiseptic  dissolved,  it  is  possible,  when  the 
quantity  of  yeast  is  large,  that  solutions  more  concentrated  than  those  indicated  in 
column  (B)  may  produce  favourable  effects  on  the  fermentation.  It  is  unnecessary  to 
state  that  these  concentrations  vary  somewhat  with  the  nature  of  the  organisms.  It 
has  been  shown  recently  (1910),  for  example,  that  Staphylococcus  pyogenes  aureus  resists 
a  2-7  per  cent,  solution  of  mercuric  chloride  for  six  hours. 

The  organic  acids  also  exert  an  unfavourable  influence  on  alcoholic  fermentation,2 
whilst,  within  certain  limits,  lactic  and  formic  acids  and  formaldehyde  have  a  beneficial 
action,  since  they  prevent  the  development  of  harmful  bacteria  and  are  readily  tolerated 
by  alcoholic  ferments  specially  acclimatised  to  their  action.  By  adding  small  quantities 
of  formaldehyde  and  of  sterilised  milk  (which  then  gives  lactic  acid),  the  yield  of 
alcohol  has  recently  been  increased  by  as  much  as  2  per  cent.  E.  Soncini  (1910)  has 
shown  that  the  course  of  fermentation  in  general  is  closely  connected  with  the  chemical 
medium  in  which  it  takes  place  ;  thus,  in  a  saccharine  wort  (from  bananas),  the  lactic 
fermentation  first  develops  spontaneously  and  proceeds  until  the  lactic  acidity  reaches  a 
certain  limiting  amount  ;  this  may  be  followed  by  alcoholic  fermentation,  which,  in  its 
turn,  may  be  succeeded  by  the  acetic  fermentation  ;  the  lactic  fermentation  may  ulti- 
mately begin  again.  It  is  only  by  considering  all  these  conditions  that  a  regular  alcoholic 
fermentation  and  a  good  yield  of  pure  alcohol  can  be  assured,  since  in  general  the  secondary 
and  harmful  products  of  the  fermentation  (higher  alcohols,  such  as  amyl,  &c.)  result 
from  the  actions  of  extraneous  micro-organisms.  The  carbon  dioxide  formed  during 
fermentation  may  give  rise  to  pressures  as  high  as  12  atmos.  if  hermetically  sealed  vessels 
are  used,  and  the  action  of  the  yeast  is  then  retarded  or  even  arrested. 

PRACTICE  OF  FERMENTATION.  To  start  the  fermentation  of  the  worts  pre- 
pared as  described  above,  various  methods  are  used :  in  some  cases  a  portion  of  old, 
fermented  wort  from  a  preceding  operation  is  employed  ;  but  this  is  not  a  rational  method, 
because  the  yeast  in  the  old  wort  is  in  a  condition  unfavourable  to  development  and  is 
also  contaminated  with  other  micro-organisms  which  would  develop  readily  in  the  new 
wort.  To  be  preferred  is  the  custom  followed  by  certain  distilleries  of  starting  the  fer- 
mentation with  brewery  yeast,  which  is  cheap  and  comparatively  pure.  The  best  and 
most  rational  method  is,  however,  the  use  of  selected  yeast  in  culture  wort  or  in  a  pressed 
condition  (see  above),  as  supplied  by  various  firms  and  institutions  which  guarantee  its 
purity.  By  this  means  alone  it  has  been  possible  during  the  past  few  years  to  increase 
the  mean  yield  of  alcohol  in  distilleries  by  0-5  per  cent,  or  even  1  per  cent.,  and  at  the 
same  time  to  improve  the  quality  of  the  product. 

It  is  advisable  to  ferment  worts  as  soon  as  they  are  prepared  and  cooled  to  15°  to  20°, 
delay  resulting  in  contamination  with  heterogeneous  germs  always  present  in  the  air. 

To  avoid  secondary  fermentations  as  far  as  is  possible,  addition  is  often  made  to  the 

Thus,  lor  example : 


Bromine 
Thymol 
Salicylic  acid 
Phenol 

Sulphuric  acid 
Boric  acid 


2  The  action  of  some  of  the  commoner  acids  is  as  follows  : 


(A)  The  most  dilute  solution        (B)  The  most  concentrated 

capable  of  preventing                    solution  capable  of 

fermentation  is  :                  favouring  fermentation  is  ;. 

oride  . 

1  in  20,000 

1  in  300,000 

ermanganate 

10,000 

100,000 

4,000 

50,000 

3,000 

20,000 

d 

1,000 

6,000 

200 

1,000 

:id 

100 

10,000 

25 

8,000 

Dose  that  retards 

Dose  that  arrests 

alcoholic  fermentation 

alcoholic  fermentation 

Acetic  acid 

0-50  % 

1-0    % 

Formic  „ 

0-20  % 

0-30  % 

Propionic  acid 
Valeric        ,, 

0-15  % 
0-10  % 

0-30  % 
0-15  % 

Butyric       ,, 

0-05  % 

0-10% 

Caproic 

— 

,                 0-05  % 

128  ORGANIC    CHEMISTRY 

wort  of  antiseptics,  to  which  the  selected  yeasts  have  been  habituated.  Thus,  small 
proportions,  of  calcium  bisulphite  or,  better,  of  ammonium  or  aluminium  fluoride  are 
added,  the 'hydro fluoric  acid — liberated  under  the  action  of  the  acids  formed  in  the 
secondary  fermentations — killing  the  harmful  organisms.  With  the  Effront  process, 
hydrofluoric  acid  (see  vol.  i,  p.  156)  is  added  directly  in  the  proportion  of  5  or  even  10  grms. 
per  hectolitre  of  wort  (some  yeasts  resist  as  much  as  100  grms.  of  HF  per  hectolitre). 
Sometimes  a  selected  lactic  ferment  (Bacillus  acidificans  longissimus)  is  added,  this  ako 
favouring  the  production  of  pure  alcohol. 

The  use  of  these  yeasts  acclimatised  to  the  action  of  hydrofluoric  acid  renders  possible 
the  employment  of  the  temperature  55°  to  57°  (see  above)  for  the  previous  saccharification 
of  the  starch  by  diastase,  this  low  temperature  resulting  in  the  formation  of  an  increased 
amount  of  maltose  ;  also  if  there  are  other  noxious  living  micro-organisms  in  the  wort, 
these  are  killed  by  the  hydrofluoric  acid  during  the  fermentation. 

Effront,  however,  succeeded  in  preparing  yeasts  capable  of  fermenting  also  the  dextrin 
with  ease  ;  when  these  are  used,  the  saccharification  with  diastase  can  be  effected  with 
less  malt  and  at  64°  to  65°,  so  that  harmful  micro-organisms  are  killed.  All  the  apparatus, 
instruments,  and  vats  which  come  into  contact  with  the  wort  should  be  previously  washed 
with  dilute  hydrofluoric  acid  solution  (100  grms.  per  25  litres  of  water). 

For  every  hectolitre  of  wort  are  added  about  30  grms.  of  pressed  yeast  in  small  quantities 
mixed  up  with  increasing  quantities  of  wort  and  well  stirred  in  ;  the  fermentation  then 
starts  immediately. 

The  fermentation  of  the  wort  proceeds  in  three  successive  phases  : 

(1)  Preliminary  fermentation,  in  which    the   yeast   develops   and  grows, 
the  most  favourable  temperature  being  17°  to  21°. 

(2)  Principal  fermentation,  in  which  the  maltose  and  glucose  are  fermented, 
best  at  26°  to  30°. 

(3)  Secondary  fermentation,   in   which  the   dextrins    are    fermented,   the 
diastase  continuing  to  saccharify  the  remaining  dextrins  as  the  wort  becomes 
warm,  the  best  temperature  being  25°  to  27°. 

The  vats,  holding  10  to  90  hectols.  and  often  furnished  with  stirrers,  are  filled  with 
wort  to  the  extent  of  nine-tenths.  The  temperature  is  regulated  by  suitable  cold-water 

coils  (attemperators,  Fig.  124),  which 
are  of  various  forms  (see  Beer).  In 
general,  these  attemperators  have  a 
surface  of  0-3  to  0-4  sq.  metres  per 
10  hectols.  of  wort.  Fermentation  is 
begun  in  the  vats  at  12°  to  15°,  and 
after  2  or  3  hours  the  tempera tuie 
FIG  124  rises  and  the  fermentation  becomes 

vigorous.    The  liquid  is  then  agitated 

to  liberate  the  CO2,  thus  diminishing  the  pressure  in  the  mass  and  facilitating  the 
fermentation,  the  temperature  not  being  allowed  to  exceed  28°  to  29°.  After  two  days, 
the  principal  fermentation  ceases  and  the  temperature  is  maintained  at  25°  to  26°  for  a 
day,  the  fermentation  being  thus  completed. 

Worts  that  are  too  dilute  or  are  made  from  poor  malt  or  impure  grain  give  a  boiling 
fermentation  that  hurls  the  liquid  from  the  vat  and  renders  the  subsequent  distillation 
difficult.  This  inconvenience  is  avoided  by  using  more  concentrated  worts  and  good 
yeast,  or,  in  case  of  necessity,  adding  100  to  200  c.c.  of  oil  to  each  vat. 

Ammonium  fluoride  (2  to  2-5  grms.  per  hectolitre)  or  hydrofluoric  acid  (rather  less)  is 
often  added  to  the  wort  before  fermentation. 

LOSSES  AND  YIELDS.  A  residue  of  unfermented  starch  (0-7  to  2  per  cent.)  and 
dextrin  (5  to  8  per  cent.)  always  remains  after  fermentation.  In  every  fermentation  2  to 
3  per  cent,  of  glycerol  are  formed  ;  also  part  of  the  sugar  serves  as  food  for  the  yeast  and 
part  of  the  alcohol  evaporates,  this  making  a  total  of  6  to  8  per  cent. 

Starting  with  100  parts  of  starch,  12  to  20  parts  are  usually  lost  in  various  ways,  and 
with  improper  working  the  loss  may  reach  28  per  cent. 

If  the  starch  could  be  transformed  theoretically  into  alcohol  and  carbon  dioxide  alone, 
100  kilos  of  starch  should  yield  71-6  litres  of  pure  alcohol  ;  allowing  for  these  losses  and 


DEGREE    OF    ATTENUATION  129 

working  under  the  best  conditions,  63-5  litres  of  alcohol  are  obtained  ;  60  litres  is  a  good 
yield  and  58  litres  a  medium  one,  whilst  55  litres  would  indicate  bad  conditions  of  working. 
The  mean  starch -contents  of  many  of  the  prime  materials  used  in  the  distillery  are  given 
on  p.  117  ;  that  of  green  malt  (from  good  barley)  is  38  to  42  per  cent,  and  that  of  kilned 
malt,  65  to  70  per  cent.  Whilst  in  1883  Italian  distilleries  gave  an  average  yield  of  31-5  litres 
of  alcohol  per  quintal  of  maize,  in  the  season  of  1904-1905  the  yield  (official  statistics) 
amounted  to  35  litres. 

For  calculating  the  yield,  the  exact  analyses  of  the  prime  materials,  starch  and  sugar, 
must  be  known.  The  sugar-content  of  a  wort  is  determined  from  the  density  by  means 
of  the  Balling  saccharometer  modified  by  Brix,  degrees  Brix  (or  Balling)  read  at  20° 
(formerly  17-5°)  indicating  directly  the  percentage  of  sugar  in  the  solution.  In  worts, 
however,  part  of  this  density  is  due  to  unfermentable  substances. 

As  fermentation  proceeds,  the  proportion  of  alcohol  increases  and  the  density 
diminishes  ;  this  diminution  is  called  the  degree  of  fermentation  or  attenuation.  The 
density  is  measured  before,  during,  and  after  the  fermentation  on  the  filtered  wort,  and 
if  it  filters  badly  it  is  diluted  with  a  definite  volume  of  water.1  When  the  fermentation 
is  finished  and  the  degree  of  attenuation  controlled,  the  resultant  fermented  wash  (with 
about  9  to  11  per  cent,  of  alcohol)  is  subjected  to  distillation  and  rectification  in  order  to 
extract  the  alcohol  and  separate  it  from  the  water,  yeast,  and  other  solid  and  liquid 
substances.  Before  the  distillation  apparatus  is  described,  certain  special  eaccharification 
and  fermentation  processes,  which  have  been  recently  applied  practically,  will  be  considered. 

The  AMYLO  PROCESS  (Collette  or  Boidin  Process).  This  process  is  based  on  investi- 
gations of  Calmette,  Collette,  Boidin,  and  others,  who  found  that  certain  Mucors  (mould?, 
see  p.  Ill),  isolated  from  impure  Chinese  and  Japanese  ferments,  are  capable  of  performing 
the  functions  of  both  diastase  and  zymase,  that  is,  of  transforming  starch  into  alcohol  by 

1  The  density,  p,  before  fermentation  is  due  to  x  parts  of  sugars  +  z  parts  of  non-fermentable  substances ; 
if  the  density  after  fermentation  indicates  the  magnitude,  z,  then  p — z  =  x.  But  this  does  not  give  the  absolute 
attenuation,  since  z  is  altered  by  the  presence  of  alcohol  and  carbon  dioxide.  If  the  carbon  dioxide  is  eliminated 
by  shaking  and  gentle  heating,  a  density,  m,  is  obtained  and  the  magnitude  of  (p — m)  gives  the  so-called  apparer.t 
attenuation  (apparent  because  alcohol  is  still  present) ;  the  amount  of  alcohol  formed  can  be  allowed  for  by  meai.s 
of  a  factor,  a,  the  real  attenuation  being  given  by  A  =  a  (p — m).  The  value  of  a  is  determined  by  distilling  a  small 

^ 
quantity  of  fermenting  wort,  and  calculating  the  value  of  the  expression  a  =  -. : ;    a  is,  however,  not  a 

constant,  but  varies  with  the  nature  of  the  sugars,  with  the  original  concentration,  p,  and  with  the  stage  of 
the  fermentation  (incipient,  vigorous,  or  secondary).  If  a  is  known,  the  quantity  of  alcohol  obtainable  from  a 
fermented  wort  of  a  given  density  can  be  calculated. 

The  ratio  between  the  apparent  attenuation,  (p — m),  and  the  original  saccharometer  reading,  p,  gives  the 
so-called  degree  of  apparent  fermentation  (B).  If  p  =  25°  and  the  density  (m)  of  the  fermented  wort  is  3,  we  have 

25  —  3 
B  =  =  0-880,  which  is  the  degree  of  apparent  fermentation  and  indicates  that,  of  every  unit  of  saccharine 

4t> 

substances,  0-880  parts  have  disappeared,  i.e.  have  been  fermented.  From  the  degree  of  apparent  fermentation 
(B),  the  degree  of  apparent  attenuation  can,  of  course,  be  obtained  :  thus,  —  —  =  B  gives  p — m  =  Bp ;  and 

from  the  factor  a  mentioned  above,  the  amount  of  alcohol  resulting  from  such  degree  of  apparent  fermentation 
is  known. 

The  real  attenuation  (A')  is  determined  by  distilling  a  certain  quantity  of  the  fermented  wort  until  its  volume 
is  reduced  to  one-third,  the  residue  being  made  up  to  the  original  volume  with  water  and  the  density,  n,  measured  ; 
the  real  attenuation  then  =  p — n.  But,  since  the  residue  always  contains  unfermented  matter,  in  order  to 
calculate  the  alcohol,  a  factor,  b,  is  determined  in  the  same  way  as  the  factor,  a,  i.e.  by  distillation  of  a  part  of 
the  fermented  wort ;  the  quantity  of  alcohol  can  then  always  be  determined  from  the  density  of  the  fermented 

wort,  for,  since  A'  =  (p — n)  b,  b  = .    Similarly,  the  degree  of  real  fermentation  will  be  B'  =  — -—which 

p — n  p 

expresses  the  fraction  of  the  extract  (dissolved  substance  without  alcohol)  really  fermented,  the  manufacturer 
being  thereby  able  to  judge  if  the  fermentation  proceeds  normally  and  to  establish  comparisons  with  previous 
fermentations,  &c. 

The  apparent  attenuation  (alcohol  being  present)  is  always  greater  than  the  real  (derived  after  elimination 
of  the  alcohol)  and  the  attenuation  difference,  D,  is  obtained  by  subtracting  one  from  the  other,  (p — m) — (p — n)  =  D- 
This  magnitude,!),  is  therefore  equal  to  n — mand  increases  as  the  fermentation  proceeds  towards  completion;  also 
here  the  quantity  of  alcohol  already  formed  is  found  by  determining  experimentally  a  factor,  c,  in  the  usual  way, 

A                                                                                                                                  p — m 
so  that  ^_—  =  c,  or  A  =  (n — m).c.     The  ratio  of  the  apparent  to  the  real  attenuation,    n   =  q,  gives   a  quo- 

tient  of  attenuation  which  varies  with  the  concentration  of  the  liquid  but  becomes  constant  towards  the  end  of 
the  fermentation  and  shows  how  much  the  apparent  fermentation  is  greater  than  the  real ;  by  its  means,  almost 

all  the  saccharometric  calculations  can  be  made  :  ~  =  the  alcohol  factor  for  the  real  attenuation,  and  if  this  is 

q 
divided  by  q  diminished  by  unity  [i.e.  by  (q — 1)],  the  factor,  c,  for  the  difference  of  attenuation  is  obtained 

D 

The  factor,  r,  is  used  for  the  analysis  of  liquids  for  which  the  value  of  p  is  unknown     also  —  =  B'  (degreeof  real 

fermentation). 

The  following  illustrates  a  practical  calculation  :   the  original  saccharometric  degree  of  a  wort  was  p  =  16-2, 
and  that  after  fermentation  m  =  1,  and  that  after  boiling  n  =  3-9 ;  applying  any  one  of  the  three  factors  (a, 
II  9 


130 


ORGANIC    CHEMISTRY 


way  of  maltose  and  dextrin.  Of  these  moulds,  Amylomyces  Rouxii,  discovered  by  Calmette 
in  1892,  and  the  Mucors  B  and  C  discovered  by  Collette,  Boidin,  and  Mousain,  are  of  most 
importance  industrially.1  Of  the  first  two,  the  forms  observed  under  the  microscope 
in  different  stages  of  development  are  shown  in  Fig.  125  (A,  B,  C,  D,  and  E). 

b,  and  c)  given  in  the  appended  Table,  the  apparent  attenuation  becomes  A  =  (p — m)  a  (where  p  =  16-2, 
a  =  0-4267)  =  6-4858  per  cent,  of  alcohol.  Calculating  according  to  the  real  attenuation,  A  =  (p — n)  b  (where 
p  —  16-2,  n  =  3-9,  and  6  =  0-5274)  =  6-4870  per  cent,  of  alcohol.  Lastly,  calculating  from  the  attenuation 
difference,  D,  A  —  (n — m)  c  (where  c  =  2-2350)  =  6-4815  per  cent.  Hence  the  fermented  wash  consists  of 
6-48  per  cent,  of  alcohol,  3-9  per  cent,  of  unfermented  extract  (n),  and  89-62  per  cent,  of  water. 

TABLE  FOB,  CALCULATING  THE  ATTENUATION  IN  FERMENTED  WORTS 


Alcohol  factors  for 

Saccharo- 
meter  degrees 
of  the  wort 

the  attenuation 

Factors  for  the 
attenuation 
difference 

Attenuation 
quotient 

c 
Values  of  r 

Apparent 

Real 

b 

P 

a 

b 

c 

9 

6      . 

0-4073 

0-4993 

2-2096 

1-226 

4-4247 

7      . 

0-4091 

0-5020 

2-2116 

1-227 

4-4052 

8      . 

0-4110 

0-5047 

2-2137 

1-228 

4-3859 

9      . 

0-4129 

0-5074 

2-2160 

1-229 

4-3668 

10      . 

0-4148 

0-5102 

2-2184 

1-230 

4-3478 

11       . 

0-4167 

0-5130 

2-2209 

1-231 

4-3289 

12      . 

0-4187 

0-5158 

2-2234 

1-232 

4-3103 

13       . 

0-4206 

0-5187 

2-2262 

1-233 

4-2918 

14       . 

0-4226 

0-5215 

2-2290 

1-234 

4-2734 

15      . 

0-4246 

0-5245 

2-2319 

1-235 

4-2553 

16      . 

0-4267 

0-5274 

2-2350 

1-236 

4-2372 

17       . 

0-4288 

0-5304 

2-2381 

1-237 

4-2194 

18       . 

0-4309 

0-5334 

2-2414 

1-238 

4-2016 

19      . 

0-4330 

0-5365 

1M!U,S 

1-239 

4-1840 

20      . 

0-4351 

0-5396 

2-2483 

1-240 

4-1660 

21      . 

0-4373 

0-5427 

2-2519 

1-241 

4-1493 

22      . 

0-4395 

0-5458 

2-2557 

1-242 

4-1322 

23      -. 

0-4417 

0-5490 

2-2595 

1-243 

4-1152 

24      . 

0-4439 

0-5523 

2-2636 

1-244 

4-0983 

25      . 

0-4462 

0-5555 

2-2677 

1-245 

4-0816 

26      . 

0-4485 

0-5589 

2-2719 

1-246 

4-0650 

27      . 

0-4508 

0-5622 

2-2763 

1-247 

4-0485 

28      . 

0-4532 

0-5636 

2-2808 

1-248 

4-0322 

29      . 

0-4556 

0-5690 

2-2854 

1-249 

4-0160 

30      . 

0-4580 

0-5725 

2-2902 

1-250 

4-0000 

B.  Wagner,  F.  Schultze,  and  J.  Rub  (1908)  suggest  the  Zeiss  immersion  refractometer  as  a  means  of  deter- 
mining the  attenuation  :  exact  results  are  obtained  rapidly  and  with  a  small  quantity  of  liquid  (20  to  30  c.c.).  A 
little  of  the  wort  is  well  shaken  to  get  rid  of  carbon  dioxide,  and  filtered  through  a  covered  filter,  5  c.c.  of  the 
filtrate  being  used  to  determine  the  refractometer  reading,  A,  at  a  temperature  of  17-5° ;  a  further  20  c.c.  are 
evaporated  to  one-half  the  volume  in  a  porcelain  dish  to  expel  the  alcohol,  the  volume  being  then  made  up  exactly 
to  20  c.c.  with  water  and  the  refractometer  reading,  B,  taken.  From  the  difference,  A—B=C,  15  (the  refracto- 
meter  reading  for  water)  is  subtracted,  giving  E  ;  the  corresponding  alcohol  degree  (by  volume),  V,  is  then  found 
in  the  following  Table  and  can  be  subsequently  corrected  for  the  density  of  the  wort : 


E: 

V  : 


16-2     17-5     18-8     20-1     21-4     22-8     24-2     25-6     27-1     28-6     30-1     31-7     33-3     34-9     36-4     38-0 
1          2          3          4          5          6          7          8          9         10        11         12        13        14        15        16 


1  Among  the  Ilyphomyceles  (moulds,  p.  Ill) — in  the  Mucor  and  Mucedirue — Pasteur  found  certain  varieties 
(Mucor  racenwsm)  capable  of  transforming  sugar  into  alcohol  and  carbon  dioxide  when  they  live  immersed  in 
the  liquid  out  of  contact  of  air  (like  the  yeasts) ;  in  presence  of  air,  they  convert  the  sugar  directly  into  water 
and  carbon  dioxide.  These  are  called  facultative  anaerobic  organisms.  In  1887  Gayon  studied  other  varieties 
which  behave  similarly  (Mucor  alternant,  spinosus,  and  cirrinettoides),  and  Prinsen  Geerligs  investigated  Chlamy- 
domucor  oryzce,  which  is  used  in  Java  to  ferment  molasses.  In  1892  Calrnette  imported  from  China,  studied, 
and  named  Amylomyces  Rouxii,  the  Mucor  isolated  from  the  rice-ferment  used  by  the  Chinese  (which  is  more 
active  than  the  Japanese  l-oji)  for  the  preparation  of  spirit ;  later  he  found  this  Mucor  in  rice-husks.  At  Tokyo 
in  1894,  Takamine  studied,  and  applied  practically  to  the  saccharification  of  rice,  Aspergillus  oryzce  (separated 
from  Japanese  koji,  which  is  a  mixture  of  yeasts  and  moulds  used  in  Japan  for  producing  alcoholic  fermentation), 
but  it  did  not  meet  with  success,  owing  to  its  action  being  too  energetic.  Boidin,  Collette,  and  Mousain  investi- 
gated Mucor  /3,  which  is  another  Mucor  separated  from  Japanese  koji  and  is  different  from,  and  more  important 
industrially  than,  that  of  Takamine ;  Mucor  y,  which  was  separated  at  the  same  time  from  Tonkin  rice,  is  of 
still  greater  practical  value  than  Mucor  /s. 

These  moulds  have  the  special  property  of  saccharifying  starch  and  of  fermenting  the  sugar  thus  formed.  Their 
saccharifying  and  fermentative  activity  is,  however,  influenced  by  the  acids  that  they  produce.  Thus,  Amylomyces 
Rouxii,  which  was  the  first  to  be  used  in  practice  in  1898,  was  abandoned  later,  as  it  transforms  rather  too 
much  sugar  into  carbon  dioxide  and  water  and,  owing  to  the  production  of  1-45  grms.  of  acid  per  litre  of  wort  (at 


AMYLO    PROCESS 


131 


Collette  and  Boidin  patented  in  1897  (Eng.  Pat.  19,858)  a  process  for  the  industrial 
utilisation  of  Amylomyces  Rouxii  for  manufacturing  alcohol  directly  from  the  starch  of 
cereals,  &c.,  and  later  they  utilised  Mucor  ft.  At  the  present  time  this  process  is  employed 
on  an  enormous  scale  in  varioiis  distilleries  in  France,  Belgium,  and  Italy  (at  Savona). 

As  it  is  necessary  to  work  with  perfectly  aseptic  worts,  the  starch-paste  prepared  in 
the  ordinary  way  with  the  Henze  apparatus  is  passed  into  closed  metal  cylinders  holding 
200  to  1000  hectols.  and  furnished  with  vertical  stirrers.  When  the  temperature  reaches 
65°,  1  per  cent,  of  malt  (on  the  amount  of  maize  used)  is  added  to  render  the  mass  rather 
more  liquid  ;  after  an  hour  the  mash  is  slightly  acidified  by  the  addition  of  0-1  grm.  of 
sulphuric  acid  per  litre,  and  is  then  rendered  completely  sterile  by  passing  steam  in  at 
the  bottom  and  boiling  the  wort  until  the  steam  issues  freely  from  the  upper  aperture. 
The  apparatus  is  then  closed  hermetically,  a  vacuum  being  produced  by  the  condensation 


FIG.  125. 

A.  Colonies  of  Amylomyces  Rouxii  in  wort-gelatine.  B.  Mycelial  conidia  of  Amylomyces  Rouxii 
in  aerobic  cultures.  C.  Segmentation  into  gemmae  of  the  mycelium  of  Amylomyces  in  anaerobic 
culture.  D.  Hyphse  of  Mucor  /3  (1  :  100)  with  sporangia  in  aerobic  culture.  E.  Mycelium  of 
Mucor  £  with  spores  in  different  stages  of  development  in  anaerobic  culture  :  1,  spores  just  sepa- 
rated ;  2,  turgid  spores  ready  to  germinate  ;  3,  germinating  spores  ;  4,  mycelium  (1 :  600). 

of  the  steam.  The  vacuum  is  relieved  by  allowing  sterilised  air — filtered  through  cotton- 
wool (see  p.  124) — to  enter  ;  the  maintenance  of  a  slight  pressure  inside  the  vessel  prevents 
the  entry  of  germs.  By  stirring  the  starch  and  running  cold  water  down  the  outer  walls 
of  the  cylinder  1000  hectols.  of  boiling  wort  may  be  cooled  in  five  hours  to  38°  ;  this 
is  the  most  suitable  temperature  for  the  Mucor  fermentation,  but  a  great  part  of  the 

16°  Balling),  complete  attenuation  is  obtained  only  in  very  dilute  worts  (7°  to  8°  Balling,  these  giving  4  to  4-5  per 
cent,  alcohol) ;  Mucor  ft,  on  the  other  hand,  forms  only  0-75  grm.  of  acid,  and  can  ferment  worts  at  10°  to  17°  Balling 
(which  give  8  to  9  per  cent,  of  alcohol)  without  oxidising  completely  more  than  a  very  small  proportion  of  sugar. 
Calmette  studied  more  particularly  the  saccharifying  properties  of  Amylomyces  Rouxii,  but  in  1897  Boidin 
and  Bolants,  and  simultaneously  Sanguinetti  (Institut  Pasteur,  1897)  found  that  this  mould  is  also  capable  of 
transforming  sugar  and  dextrin  into  alcohol ;  it  was  found  later  that  Mucor  racemosus,  which  had  been  already 
studied  by  Pasteur,  behaved  similarly.  In  1895  Professor  Saito,  of  Tokyo,  isolated  Rhizopits  oligotyorus,  which 
acts  like  Amylomyces  Rouxii. 


132 


ORGANIC    CHEMISTRY 


sulphuric  acid  added  must  first  be  neutralised.     A  vat  of  1000  litres  capacity  contains 
150  to  200  quintals  (15  to  20  tons)  of  maize  and  six  times  as  much  water. 

The  Amylomyces  is  cultivated  in  the  laboratory  on  100  grms.  of  rice  and  200  c.c.  of 
sterile  wort,  so  that  preferably  spores  are  developed.  Every  culture-flask  contains  a 
total  of  about  0-1  grm.  of  spores,  and  this  quantity  is  sufficient  to  inoculate  1000  hectols. 
of  wort.  The  Mucor  is  introduced,  under  aseptic  conditions,  into  the  vats  from  above 
and  the  stirrer  set  in  motion  ;  a  little  air  is  introduced,  this  issuing  by  an  upper 
tube  with  a  hydraulic  seal.  In  the  course  of  24  hours  the  wort  is  attacked  by  an 
abundant  growth  of  the  Mucor.  The  mass  is  then  cooled  to  33°  and,  in  order  to  com- 
plete the  alcoholic  fermentation  more  rapidly,  a  small  quantity  of  ordinary  yeast  (500  c.c. 
of  a  wort  culture,  corresponding  with  3  to  4  grms.  of  pressed  yeast)  is  added. 

After  3  to  4  days,  the  alcoholic  fermentation  is  complete  (the  carbon 
dioxide  passes  out  at  the  top  through  the  water-seal).  Fig.  126  shows  dia- 
grammatically  a  plant  with  five  large  fermentation  vessels. 


FIG.  126. 

The  advantages  of  the  amyio-process  are  :  (1)  a  considerable  saving  in 
malt,  only  about  1  per  cent,  being  used  instead  of  12  to  15  per  cent,  by  the 
old  process  ;  further,  air-dried  malt  is  difficult  to  keep  in  hot  countries  ; 
(2)  the  reduction  of  the  amount  of  yeast  required  to  a  minimum.  The  yield 
of  alcohol  is  also  sensibly  increased,  one  quintal  of  maize  containing  57  to  58  per 
cent,  of  starch  yielding  37-5  litres  of  alcohol,  i.e.  65  (often  66)  litres  of  pure 
alcohol  per  100  kilos  of  starch ;  the  old  method  of  working  gives  only  60  to  61 
litres. 

The  increase  in  the  alcohol-yield  is  naturally  due  to  the  fermentation 
taking  place  in  a  wort  uncontaminated  with  extraneous  micro-organisms  ;  on 
rectification,  4  to  5  per  cent,  more  good  spirit  (bon  gout)  are  obtained  than 
by  the  old  process. 

Finally,  the  spent  wash  (residue  after  distillation)  filters  better,  since  it 
contains  less  dextrin  and  does  not  block  the  filter-presses. 

DISTILLATION  OF  THE  FERMENTED  LIQUID.  As  has  already  been  stated, 
the  fermentation  is  rendered  the  more  complete  by  using  worts  which  are  not  too  con- 
centrated and  yield  9  to  10  per  cent,  of  ethyl  alcohol.  These  fermented  liquids  contain  also 


RECTIFICATION 


133 


FIG.  127. 


small  quantities  of  various  other  substances,  such  as  aldehydes,  organic  acids  (acetic, 
propionic,  butyric,  lactic,  succinic,  &c.),  certain  higher  alcohols  (amyl,  propyl,  butyl  ; 
glycerol),  &c.,  besides  the  solid  residues  of  cereals  and  yeast  and  small  amounts  of 
unfermented  dextrin  and  starch. 

It  was  formerly  not  easy  to  separate  the  ethyl  alcohol  from  these  products,  in  spite 
of  the  great  differences  in  boiling-point  in  some  cases  (amyl  alcohol,  132°  ;  ethyl  alcohol, 
78-4°),  and,  as  already  explained  on  p.  109,  this  separation  cannot  be  effected  with  the 
most  exact  fractional  distillation,  so  that  recourse  must  be  had  to  rectification  (see  p.  3).1 
Every  distillation  apparatus  is  now  composed  of  four  parts  : 
(1)  the  boiler  in  which  the  alcoholic  liquid  is  heated;  (2)  the 
rectifier  ;  (3)  the  dephlegmator  ;  and  (4)  the  condenser.  The 
liquid  collecting  in  the  dephlegmator  returns  to  the  column 
(hotter),  where  alcohol  vapours  are  formed  richer  than  those  from 
which  it  was  formed  in  the  first  distillation  ;  so  that  the  alcohol 
vapours  of  the  dephlegmator,  uniting  with  the  other  vapours 
before  the  condenser  is  reached,  contribute  to  form  a  more  con- 
centrated alcohol. 

Apparatus  with  continuously  working  columns  and  with  re- 
covery of  the  heat  have  been  studied  and  applied  since  1867 
(Savalle).  • 

The  action  of  a  rectifying  column  may  be  understood  from  Fig. 
127,  showing  part  of  the  column,  which  is  divided  into  a  number 
of  chambers  communicating  by  means  of  tubes  and  placed  above 
the  boiler.  The  mixture  of  alcohol  and  water  vapours  from  the 

Jj         IBilg^aa        boiling  fermented  wash  below  ascends  the  column  from  chamber 
to  chamber  through  the  central  tubes,  which   are   covered  with 

ffl  ^  caps  dipping  below  the  surface  of  the  liquid  in  the  chambers  ;    by 

this  arrangement  the  mixed  vapours  are  obliged  to  pass  through 
the  hot,  condensed  liquid,  which  slowly  descends  the  column 
through  the  drop-tubes,  when  it  reaches  a  certain  level  in  each 
chamber.  The  vapours  give  up  to  the  liquid  mainly  water-vapour,  and  the  liquid  gives 
up  to  the  vapours  preferably  the  alcohol  it  contains,  so  that  the  alcohol -vapour  reaches 
the  top  of  the  column  mixed  with  only  a  little  water-vapour  and  passes  to  the  condenser, 
whilst  water  almost  free  from  alcohol  flows  downwards,  forming  vinasse  or  spent  wash. 

With  this  column,  8  to  10  metres  high  and  containing  20  to  25  plates  and  chambers, 
one  distillation  and  partial  rectification  yields 
directly  a  crude  50  to  65  per  cent,  alcohol,  and 
when  this  is  subjected  to  a  second  similar 
distillation  and  rectification  a  concentration  of 
90  per  cent,  or  even  96  per  cent,  is  attained  ; 
each  apparatus  gives  a  high  output.  This  is 
the  procedure  often  adopted  in  France. 

Taller  columns  (14  to  18  metres)  are,  how- 
ever, used,   especially   in    Germany,  and   these 

with  efficient  dephlegmators  give  90  per  cent,  or  even  96  per  cent,  alcohol  in  one  continuous, 
although  slower,  operation.  The  cylindrical  columns  are  advantageously  replaced  by 
square  ones,  which  are  less  easily  stopped  up  and  more  easily  cleaned  and  repaired  ;  in 
place  of  the  costly  copper  columns,  cheaper  cast-iron  ones  are  now  largely  used.  A  square 
plate  of  such  a  Savalle  column  is  shown  diagrammatically  in  Fig.  128,  the  apertures  and 

1  The  first  forms  of  distillation  apparatus  were  used  in  the  times  of  the  ancient  Arabs,  and  were  termed  alembics. 
The  alchemists  made  improvements  in  the  shape,  especially  of  the  part  used  for  condensing.  Simple  distillation 
apparatus,  like  that  used  for  obtaining  distilled  water  (vol.  i,  p.  225),  yield  a  highly  aqueous  spirit,  termed  phlegm. 
Argand,  and  later  Adam  (about  1800),  utilised  the  heat  of  the  aqueous  alcoholic  vapours  distilling  over  to  heat 
the  liquid  to  be  distilled.  Solimani  and  Berard  (1805)  improved  the  apparatus  so  as  to  allow  a  distillate 
moderately  rich  in  alcohol  to  be  obtained  in  a  single  operation.  Before  the  condenser  was  placed  a  vessel  called 
a  dephlegmator,  which  condensed  part  of  the  water-vapour  and  part  of  the  alcohol  (phlegm),  more  concentrated 
alcohol  vapours  passing  to  the  condenser.  The  first  really  rational  and  complete  apparatus  for  the  fractional 
distillation  of  alcohol  was  constructed  by  Cellier-Blumenthal  (1815),  who  used  dephlegmators  and  the  first  rudi- 
mentary rectifiers  ;  but  as  early  as  1813,  A.  Baglioni  had  placed  semi-rectifying  dephlegmators  directly  above 
the  boiler.  , 

The  first  column  rectifying  dephlegmator  was  devised  by  Derosne  and  Cail  in  1817,  and  shortly  afterwards 
widespread  use  was  made  of  the  very  convenient  Pistorius  apparatus,  with  its  flat,  lenticular  dephlegmators, 
which  allows  of  60  to  75  per  cent,  alcohol  being  obtained  directly,  and  is  still  used  in  some  of  the  smaller  distilleries. 


FIG.  128. 


134 


ORGANIC    CHEMISTRY 


tubes  being  sufficiently  wide  to  avoid  obstructions  when  dense  fermented  worts,  rich  in 
solid  matters,  are  distilled.  The  heating  of  the  column  and  of  the  liquid  is  no  longer 
effected  by  direct  steam,  as  this  causes  useless  dilution  ;  indirect  steam  is  employed  with 


FIG.  129. 


a  tubular  heater,  to  be  described  later.  In  order  to  obtain  regularity  of  working  and 
constancy  in  the  alcoholic  strength  an  automatic  steam  regulator  is  used  (see  below), 
and  the  supply  of  fermented  wash  to  the  apparatus  is  so  controlled  that  the  yield  and 
strength  of  the  alcohol  remain  uniform.  The  heat  of  condensation  of  the  alcohol  vapours 
is  recovered  to  heat  the  wash,  and  the  latter,  before  being  introduced  into  the  top  of  the 


CONTINUOUS    DISTILLATION 


135 


column,  is  passed  through  tubular  heaters  so  as  to  utilise  also  the  heat  of  the  spent  wash 

before  this  is  discarded. 

Fig.  129  shows  the  whole  of  a  Savalle  continuous  distilling  apparatus.     The  wash  to 

be  distilled  passes  from  large  constant -level  tanks,  situate 
on  the  upper  floors,  through  the  tube  m,  furnished  with 
a  regulating  cock,  2,  into  the  bottom  of  the  heater,  C, 
from  which  it  issues  at  the  top,  after  serving  to  condense 
the  alcohol  vapours  coming  from  the  column  by  the  tube 
k  ;  these  vapours,  however,  first  yield  a  little  condensed 
spirit  in  B,  this  being  carried  to  the  column  by  the  tube  r. 
The  heated  wash  passes  along  the  pipe  q  to  the  top  of 
the  column  and  slowly  descends,  meeting  meanwhile  the 
ascending  vapour  current,  to  which  it  gradually  gives 
up  its  alcohol,  as  stated  above  (see  Fig.  127).  The 
alcohol  condensed  in  the  wash -heater  is  cooled  in  the 
condenser,  D,  below,  through  which  cold  water  circulates. 
If  the  wash  is  heated  in  the  wash -heater  sufficiently  to 
form  vapour  this  passes  into  the  small  dephlegmator,  H, 
whence  the  condensed  alcohol  and  water  are  led  by  the 
tube  S  r  to  the  column,  whilst  the  alcohol  vapour  which 
is  not  condensed  proceeds  through  t  to  the  condenser 
along  with  the  other  alcohol.  When  all  the  plates  of 
the  column  are  covered  with  wash,  steam  is  passed 
in  from  below  by  heating  the  exhausted  vinasse  by 
pipes  from  the  heater,  G,  in  which  superheated  steam 
from  suitable  boilers  circulates  ;  this  steam  is  regulated 
by  the  tap  j,  which  in  its  turn  is  controlled  by  the 
automatic  regulator  F.  When  the  distilled  alcohol  issues 
from  the  test-glass,  E,  the  access  of  wash  through  2  is 
regulated  so  that  the  alcoholic  strength  remains  con- 
stant. In  the  column  the  wash  traverses  a  path  more 


FIG.  130. 


than  125  metres  in  length,  the  total  absorptive 
surface  being  more  than  200  metres,  so  that  every 
litre  of  wash,  before  exhaustion,  meets  a  surface  of 
vapour  200  metres  long.  In  this  way  30,000  kilos 
or  more  of  wash  can  be  distilled  per  day  without 
interruption  of  the  working  for  months. 

Fig.  130  shows  Savalle 's  tubular  heater  more  in 
detail.  Steam  under  pressure  from  ordinary  boilers 
traverses  the  regulator,  E,  and  passes  through 
the  tube  i  to  a  large  metallic  cylinder,  G,  which 
contains  a  series  of  vertical  tubes  connecting 
the  upper  chamber,  0',  with  the  lower  one,  Q"  ; 
the  latter  is  filled  with  almost  exhausted  vinasse 
supplied  from  the  lower  part  of  the  Savalle  column 
by  the  pipe  x.  The  spent  wash,  which  is  already 
very  hot,  is  thus  easily  brought  into  a  condition  of 
vigorous  ebullition  and  loses  the  last  traces  of 
alcohol,  which  rise  with  a  large  quantity  of  steam 
through  the  pipe  y  into  the  Savalle  column.  The 
exhausted  spent  wash  is  discharged  continuously 
from  the  tube  7,  whilst  the  condensed  steam 
issues  from  the  tap  8. 

Fig.  131  shows  the  automatic  regulator  of  the  pressure  and  steam  in  the  distillation 
and  rectifying  column.  In  order  that  it  may  pass  through  all  the  layers  of  liquid  on  the 
plates  of  the  column  the  steam  must  be  at  a  certain  pressure  in  the  column  itself  ;  this 
pressure  increases  or  diminishes  according  as  the  quantity  and  temperature  of  the  steam 
rise  or  fall,  and  the  greater  the  supply  of  steam  the  more  dilute  will  be  the  alcohol.  If 
the  column  is  connected  with  the  pressure  regulator  by  means  of  the  tube  F(f  in  Fig.  129), 


FIG.  131. 


136  ORGANIC    CHEMISTRY 

then,  when  the  pressure  increases,  the  water  in  the  lower  chamber,  A,  of  the  regulator  is 
forced  along  the  tube  B  to  the  upper  chamber  and  raises  a  float,  C,  which  operates  the 
lever  D,  and  so  partially  closes  the  tap  (or  valve)  E  controlling  the  supply  of  steam  to  the 
heater,  G  ;  owing  to  the  diminished  supply  of  steam  the  pressure  falls.  In  the  opposite 
case,  when  the  pressure  in  the  column  is  smaller  than  that  necessary  for  regular  distilla- 
tion, so  that  the  concentration  of  the  alcohol  (measured  in  E,  Figs.  129  and  132)  becomes 
too  high  and  the  yield  too  small,  the  water  of  the  upper  chamber  of  the  regulator  descends 
to  the  lower  one,  the  float,  C,  hence  falling  and  the  steam-cock,  E,  opening  a  little.  With 
these  regulators,  which  are  sensitive  to  variations  of  one -thousandth  part  of  an  atmo- 
sphere, the  distillation  is  automatically  regulated  and  requires  very  little  personal 
control. 

'"•  The  constancy  of  the  strength  of  the  alcoholic  distillate  is  controlled  by  the  test- 
glass,  E  (see  Fig.  132),  which  is  situated  in  the  alcohol  discharge  tube  and  contains  an 
alcoholometer  fitted  with  a  thermometer,  so  that  the  concentration  and  temperature  are 
indicated  continuously. 

Of  the  variously  highly  perfected  forms  of  apparatus  (Ilges,  Coffey,  Pampe,  the  last 

of.  which  gives  very  pure  spirit  by  distillation  under 
reduced  pressure)  used  in  England,  Germany,  Russia, 
&c.,  which  allow  of  the  continuous  and  direct  pro- 
duction of  90  to  96  per  cent,  alcohol  without  special 
rectification  and  refining  (when  the  first  and  last 
products  of  distillation — foreshots  and  tailings — are 
kept  separate  ;  see  later),  we  shall  refer  only  to 
the  apparatus  of  Siemens  Brothers,  which  is  largely 
used  in  Germany  (Fig.  133).  The  column  is  com- 
posed of  three  principal  parts  :  the  heater  (or  pre- 
heater),  A,  the  distillation  column,  B,  and  the  recti- 
fier, C  ;  the  whole  is  formed  of  superposed  cast-iron 
discs  or  rings  fitted  with  pasteboard  packing  and 
held  tightly  together  by  bolts  extending  from  the 
top  to  the  bottom.  Inside  are  plates  arranged 
FIG.  132.  spirally  round  a  central  tube,  D,  which  passes  about 

half-way  up  the  column  to  / ;  the  liquids  thus  tra- 
verse a  long  path,  so  that  a  large  production  is  possible  with  a  relatively  small  tower-space. 
The  apparatus  is  also  economical  since  it  is  not  necessary  to  construct  it  of  copper.  The 
heater,  A  (see  also  Fig.  134,  A),  contains,  in  the  chambers  a  and  o,  hot  spent  wash  which 
comes  from  the  top  of  the  column.  Between  these  hot  chambers  are  arranged  alternately 
others  in  which  circulates  the  cold  wash  or  wine  to  be  distilled  ;  this  is  supplied  through 
the  pipe  d  by  means  of  high -pressure  pumps,  and  begins  to  be  heated  as  it  descends  the  spiral 
chambers  between  the  hot  ones  containing  the  spent  wash.  When  it  reaches  the  bottom 
the  hot  wash  passes  into  the  central  pipe  D,  and  rises  to  the  higher  level,/,  in  the  distillation 
column,  B  (which  embraces  the  space  between  d  and  E).  The  pipe  D  empties  on  to  the 
perforated  spiral  plates  (see  Fig.  134,  B)  and,  as  it  descends,  the  wash  meets  a  current  of 
steam  rising  from  the  tube  o  through  B.  In  this  way  the  alcohol  liberated  from  the  wash 
rises  with  the  steam  through  the  perforations  of  the  spiral  plates  and  thus  continually 
meets  fresh  quantities  of  wash  and  becomes  continually  richer  in  alcohol,  as  is  shown 
in  Fig.  134,  B.  The  wash,  thus  deprived  of  alcohol,  reaches  the  bottom  as  very  hot 
spent  wash,  which,  before  leaving  the  column,  traverses  the  chambers  of  the  heater 
(shown  in  Fig.  134,  A)  and  is  then  discharged  continuously  from  the  pipe  J  K,  at  a  lower 
level  than  /.  The  mixed  alcohol  and  water  vapours  enter  the  rectifying  compartment,  E,1 
which  is  formed  of  plain  discs  and  is  filled  with  wash,  the  level  of  which  can  be  seen  through 
suitable  glass  windows.  The  alcohol  vapours  rise  into  the  rectifier,  C  (more  properly 
termed  a  fractionator  or  dephlegmator,  see  p.  133),  formed  of  non -perforated  and  hence 
non-communicating  spiral  chambers  (Fig.  134,  C),  in  some  of  which  circulate  the  ascending 
vaporous  mixture,  whilst  the  alternate  ones  are  traversed  by  a  descending  current  of 
water  ;  the  latter  is  not  very  cold,  as  it  comes  from  the  top  of  the  condenser,  S  (by  means 
of  the  pipe  t),  so  that  it  condenses  mainly  steam  and  only  a  little  alcohol  vapour, 

1  Pampe  (Ger.  Pat.  199,142,  1908)  suggests  placing,  before  the  rectifying  compartment,  a  steam-turbine  with 
rapidly  rotating  vanes,  which  separate  all  the  suspended  drops  or  impurities  from  the  vapours. 


RECTIFYING    COLUMNS 


137 


which  falls  into  the  distilling  column  again.     The  alcohol  vapours  gradually  become 
more  and  more  highly  concentrated  and  pass  through  the  tube  F  to  the  refrigerator,  S, 
where  they  condense  and  are  cooled  by  water  flowing  in  at  s  and  out  at  t.     By  means  of 
a  sample  taken  from  the  column  B  by  the  tube  p 
and  examined  in  the  tester,  T,  it  can  be  ascertained 
if  the  spent  wash  is  completely  free  from  alcohol. 

In  some  cases  it  is  observed  that  the  spirit  from 
such  a  cast-iron  apparatus  absorbs  traces  of  hydro- 
carbons and  of  hydrogen  sulphide  which  are  formed 


FIG.  133. 


ConC.atco* 

.  f  £»—  nol  vapoun 

JLyueous  alcoltol  vapour: 

FIG.  134. 


from  the  iron  and  give  an  unpleasant  taste  and  smell  to  the  alcohol ;  this  may,  perhaps, 
depend  on  the  quality  of  the  metal  and  on  the  newness  of  the  apparatus. 

We  shall  mention  finally  the  attempts  which  have  been  made,  first  by  Perrier  in  1875, 
to  transform  the  vertical  column  into  a  horizontal  distilling  and  rectifying  column  with 
a  central  rotating  axis  carrying  helically  arranged  blades,  which  transport  even  a  very 
dense  wash  from  one  end  to  the  other,  whilst  the  opposing  current  of  steam  removes  the 
whole  of  the  alcohol.  The  process  was  perfected  by  Sorel  and  Savalle  (1891),  who  arranged 
the  numerous  vertical  chambers  of  the  horizontal  column  in  a  more  rational  manner. 
These  forms  are  not  yet  free  from  disadvantages,  but  they  have  the  advantage  of  being 


138 


ORGANIC    CHEMISTRY 


considerably  more  economical  to  construct  and  of  bringing  all  the  taps  conveniently  to 
hand  on  the  «ame  level. 

Lastly,  Guillaume  eliminated  various  defects  of  these  columns  and  at  the  same  time 
retained  all  their  advantages  by  employing  very  simple  and  convenient  inclined  columns 
(made  by  Egrot,  of  Paris),  which  allow  of  very  dense  washes  being  employed  without 
danger  of  obstruction.  Fig.  135  shows  the  complete  Guillaume-Egrot  apparatus,  and 
the  description  of  the  various  parts  given  underneath  will  indicate  the  way  in  which  it 
works.  The  cross-section  shown  in  Fig.  136  gives  an  idea  of  the  internal  arrangement  of 
the  inclined  column,  and  Fig.  137  represents  the  ground  plan  of  the  column,  the  arrows 
indicating  the  horizontal,  zigzag  course  followed  by  the  liquid  from  the  highest  part  of 
the  column,  whilst  the  vapours  ascend  the  column  in  a  zigzag  vertical  path  and  bubble 
through  the  liquid  in  all  the  chambers  formed  by  the  numerous  vertical  partitions.  With 
relatively  small  plant,  which  can  be  mounted  on  portable  cars  (see  later),  30,000  litres  or 


FIG.  135. 

A,  distilling  column  ;  a,  entrance  of  the  wash  into  the  heater  or  refrigerator  ;  B,  condenser  and 
heater;  b,  hot  wash  pipe;  C,  adjustable  steam  regulator;  c,  exit  for  spent  wash;.D,  hot  wash 
extractor  used  as  heater  ;  d,  steam-tap  ;  E,  test-glass  giving  the  strength  of  the  alcohol ;  e,  valve 
regulating  flow  and  hence  strength  of  the  alcohol ;  h,  entrance  of  water  into  refrigerators  in  case 
of  need. 

more  of  wash,  containing  10  per  cent,  of  alcohol,  can  be  distilled  per  24  hours,  90  per  cent, 
alcohol  being  produced. 

In  the  modern  distillery  the  consumption  of  steam  should  not  exceed  25  kilos  (about 
3  kilos  of  coal)  per  100  kilos  of  wash,  and  the  consumption  of  water  in  the  condenser 
should  not  exceed  80  litres. 

RECTIFICATION  OF  ALCOHOL.  The  alcohol  obtained  with  the  ordinary  Savalle 
apparatus  is  not  sufficiently  concentrated  or  pure  to  be  placed  on  the  market,  and  even 
that  obtained  with  other  forms  from  washes  which  have  nqt  been  fermented  with  selected 
yeasts  should  be  freed  by  rectification  and  refining  from  various  impurities  which  impair 
the  colour,  smell,  and  taste.  These  impurities  may  be  more  volatile  than  alcohol  (i-_uch 
as  aldehydes  and  certain  esters)  or  less  volatile  (as  acetic  and  butyric  acids  ;  propyl, 
isopropyl,  and  amyl  alcohols  ;  various  esters,  &c.),  and  they  are  separated  from  the  true 
alcohol  if,  in  the  redistillation  and  rectification,  the  portions  which  distil  most  readily 
(foreshots)  and  also  the  least  volatile  portions  (tailings  or  fusel  oil,  which  has  a  very 


PROCESS    OF    RECTIFICATION 


139 


disagreeable  odour  if  obtained  from  potatoes,  molasses,  or  maize,  but  a  pleasing  odour  if 
derived  from  grapes,  fruit,  &c. )  are  kept  apart. 

Beatification  apparatus  usually  consists  of  a  large  copper  or  iron  boiler,  A  (Fig.  138), 
which  is  heated  with  an  indirect  steam-coil  and  on  which  is  mounted  the  copper  rectifying 
column,  B.  Above  this  and  to  one  side  is  a  large  dephlegmator,  G,  which  serves  as  a  heater, 

and  is  of  importance  not 
so  much  for  condensing  the 
less  volatile  products  (water, 
amyl  alcohol,  &c.)  as  for 
furnishing  a  continuous  and 
abundant  supply  of  a  suitable 
alcoholic  liquid  to  wash  the 
vapours  arriving  at  the  top 
of  the  column  ;  it  is,  however, 
quite  useless  to  employ  several 
dephlegmators,  as  was  erro- 
neously done  in  the  past.  The 
foreshots,  which  have  a  con- 
centration up  to  94  per  cent, 
and  boil  at  85°,  are  collected 
separately.  Then  from  85°  to 
102°  alcohol  passes  over.  The 
tailings,  boiling  above  102°, 
are  collected  in  the  bottom  of 
the  column  by  shutting  off  the 

PIG.  136.  steam  and  thus  emptying  the 

plates.  The  quantities  of  these 

products  vary  according  to  the  quality  of  the  alcohol  required  ;  thus  20  per  cent,  of 
foreshots  and  tailings  may  be  obtained  and  80  per  cent,  of  alcohol  (bon  gout  extra),  or 
5  per  cent,  of  foreshots  and  tailings  and  95  per  cent,  of  alcohol  (bon  gout). 

This  apparatus  does  not  work  continuously,  the  boiler  requiring  to  be  discharged 
and  recharged.  Attempts 

y*T>tv  j^ 

£9 


to  render  the  process  con- 
tinuous were  met  with  suc- 
cess in  1881  (E.  Barbet)  in 
spite  of  the  difficulty  of 
separating  the  pure  alcohol 
from  an  impure  product 
that  boils  below  it  and 
another  that  boils  above  it. 
This  is  effected  by  carrying 
out  the  operation  in  two 
phases,  which  are,  however, 
continuous  ;  in  the  first 
phase  the  foreshots  are 
driven  off  and  the  alcohol 
distilled  from  the  remaining 
liquid,  the  tailings  being  left 
behind.  The  boiler  is  then 

replaced  by  a  rectifying  column,  which  receives  the  impure  product  and  distils  the 
foreshots,  passing  the  residue  continuously  at  a  certain  height  to  a  second  lower  column 
at  the  side  ;  this  distils  and  rectifies  the  pure  alcohol  and  retains  in  the  lowest  chamber 
of  the  column  the  tailings,  which  are  continuously  discharged. 

In  the  Savalle  rectifiers  45  kilos  of  coal  are  consumed  per  hectolitre  of  pure  rectified 
alcohol.  Continuous  rectification  results  in  a  saving  of  almost  50  per  cent,  of  fuel  compared 
with  the  discontinuous  process.  During  rectification  the  loss  of  alcohol  is  1  to  2  per  cent., 
and  the  cost  of  rectification  varies  from  3  to  3-5  lire  (2*.  6d.  to  3*.)  per  hectolitre.  The  firm 
of  Savalle  holds  that  it  is  more  economical  to  use  cold  air  than  water  in  the  refrigerators  of 
the  condensers, 


FIG.  137. 


140 


ORGANIC    CHEMISTRY 


Attention  may  lastly  be  drawn  to  the  ingenious  although  complicated  Perrier 
distilling  and  rectifying  apparatus,  in  which  the  vapours  of  alcohol,  water,  higher 
alcohols,  and  aldehydes  are  pacsed  successively  into  columns  filled  with  glass  beads  and 
surrounded  by  a  jacket  containing  a  liquid  boiling  at  a  constant  temperature,  the  latter 
bsing  hence  assumed  by  the  whole  of  the  tower.  In  one  of  these,  having  a  tempera- 
ture of  85  to  90°,  only  water  and 
the  tailings  are  condensed  ;  the 
vapours  then  pass  into  a  second 
tower,  kept  at  75°,  where  all  the 
ethyl  alcohol  (which  can  be  recti- 
fied in  another  tower)  separates  ; 
the  vapours  from  this  form  the 
foreshots  and  are  condensed  in  a 
succeeding  tower. 

OTHER  PRIME  MATERIALS 
FOR  THE  MANUFACTURE  OF 
ALCOHOL.  (1)  Beetroot  and  Mo- 
lasses. It  is  especially  in  France 
that  considerable  quantities  of 
beet  are  used  for  the  manufacture 
of  alcohol  instead  of  sugar  ;  this 
is  never  done  in  Germany  or  Italy. 
The  beets  are  washed,  minced,  and 
the  pulp  exhausted  by  pressure, 
maceration,  or  diffusion  with  water. 
This  treatment  is  described  in  the 
section  on  sugar. 

The  spirit  obtained  from  the 
beet  is  less  pure  than  that  from 
potatoes,  containing  more  propyl 
and  butyl  alcohols  but  less  amyl 
alcohol. 

Of  more  importance  in  Italy 
and  various  other  countries  is  the 
utilisation  of  beet-molasses.1 

The  complete  fermentation  of 
molasses  has  presented  many  diffi- 
culties, which  have  now  been  over- 
come. Formerly,  after  the  molasses 
was  diluted  to  8°  to  10°  Be.  (this 
was  carried  out  in  vats  provided 
with  stirrers,  see  Fig.  139),  it  was 
slightly  acidified  with  sulphuric  acid 
(2-5  grms.  of  free  H2SO4  per  litre), 
as  the  reaction  is  usually  alkaline. 
The  liquid  was  then  boiled  for  some 


1  These    are    the    dense,    viscous,   and 
FlG.    138.  blackish  mother-liquors  which  remain  from 

the  final  crystallisation  of  the  sugar  (which 

e)  and  from  which  no   further  sugar   will  crystallise  although  45  to  50  per  cent,  are  present  (see  explana- 
tion in  the  section  on  Sugar) ;  it  has  a  density  of  40°  to  45°  Be.  (74°  to  84°  Balling).      The  composition  of  beet- 
is  as  follows  :  water,  16  to  20  per  cent. ;   sugar,  44  to  52  per  cent. ;   non-nitrogenous  extractive  matters, 
10  to  15  per  cent,  (largely  pentoses) ;  nitrogenous  compounds,  6-5  to  9-5  per  cent,  (of  which  only  one-third  consists 
[  proteins,  the  rest  being  amino-acids) ;    ash  (deducting  CO2),  8-5  to  11  per  cent.     In  Italy  the  working-up  of 
nolasses  has  assumed  considerable  importance  during  the  last  few  y^ars,  owing  to  a  change  in  the  method  of 
taxing  sugar ;    previous  to  1903,  sugar  recovered  from  molasses  by  somewhat  expensive  processes  (see  Sugar) 
was  exempt  from  taxation,  whilst  nowadays  all  sugar  produced  is  taxed  uniformly,  so  that  the  manufacturers 
nnd  it  advantageous  to  sell  the  molasses  to  the  distillery  at  4s.  9d.  to  6s.  5d.  per  quintal. 

In  Germany,  Belgium,  and  part  of  France,  it  is  found  to  be  more  convenient  and  rational  to  utilise  a  large 
proportion  of  the  molasses  as  cattle-food  after  absorbing  it  by  highly  porous  vegetable  substances.  In  Italy, 
tumelina,  patented  by  E.  Molinari,  and  sanguemelassa  (blood-molasses),  patented  by  L.  Fino,  are  manufactured  ; 
the  residues  of  dried  tomatoes  (Squassi,  Bono)  and  various  other  dried  industrial  products  are  now  used  as  absor- 
bents. In  Germany  more  than  1,500,000  quintals  of  molassic  fodder  are  consumed  ;  Italy  produced  400,000 
quintals  in  1908  and  more  than  480,000  in  1909 


ALCOHOL   FROM    MOLASSES,  FRUIT,    ETC.  141 

hours  in  a  current  of  air  in  order  to  eliminate  the  volatile  acids  (nitric,  &c.)  liberated, 
and,  after  cooling  it  to  15°,  alcoholic  fermentation  was  initiated  by  the  addition  of 
vigorously  fermenting  liquid  ;  the  excess  of  acid  which  forms  is  gradually  neutralised 
with  chalk.  The  spirit  thus  obtained  is  difficult  to  purify  as  it  contains  an  aldehyde 
and  various  acids  which  boil  at  a  very  low  temperature. 

To-day,  however,  the  process  is  much  more  simple,  as  Jacquemin  and  Effront  have 
devised  various  methods  of  preparing  races  of  yeast  capable  of  living  actively  in  worts 
rich  in  salts  (nitrates,  carbonates,  &c.),  such  as  those  prepared  from  beet-molasses.  In 
the  past  the  difficulty  of  fermentation  was  attributed  to  the  presence  of  nitrates,  but  it 
appears  from  Fernbach  and  Langenberg's  experiments  (1910)  that  nitrates,  even  in 
proportions  as  great  as  0-3  per  cent.,  facilitate  fermentation. 

(a)  In  the  Jacquemin  process  the  fermentation  is  initiated  in  small  quantities  of 
wort  in  suitable  vessels  (see  Fig.  123,  p.  125),  and  the  wort  of  the  last  rather  larger  vessel 
(into  which  is  also  placed  a  little  hydrofluoric  acid,  to  which  the  yeast  has  been  previously 
"  acclimatised  ")    serves    to    pitch  a  200-hectol.  vat    containing  diluted,  non-sterilised 
molasses,  to  which  has  been  added  8  to  10  kilos 

of  calcium  hypochlorite,  this  preventing  the  de- 
velopment of  heterogeneous  organisms  during  the 
first  few  hours  without  damaging  the  yeast — 
already  adapted  to  chlorine.  By  means  of  this 
vat  two  other  500-hectol.  vats  of  similar 
diluted  molasses  can  be  brought  into  a  state  of 
vigorous  fermentation  ;  the  fermentation  takes 
place  so  rapidly  (and  this  is  the  most  specific 
action  of  these  yeasts)  that  in  three  days  the 
Avhole  of  the  molasses  is  fermented,  there  being 
thus  no  time  for  the  development  of  extraneous 
germs  causing  harmful  secondary  fermentations. 

(b)  The  Effront  process  is  still  more  simple, 
and  is  based  on  the  use  of  selected  yeasts  specially 
adapted   to    molasses  worts    and   endowed   with 
exceptionally  rapid  fermenting  properties  ;    these 

yeasts  are  placed  under  such  conditions  that  they  easily  overcome  deleterious 
bacteria  (namely,  the  addition  of  resin) 1  and  complete  the  fermentation  before  these 
become  harmful.  To  the  molasses  simply  diluted  with  water  and  not  sterilised  are 
added  these  special  yeasts  together  with  1  kilo  of  colophony  per  10  hectols.  of  wort  ; 
in  three  days  the  fermentation  is  complete.  In  1903  almost  1,000,000  kilos  of  colophony 
were  used  in  France  for  this  purpose. 

(2)  Alcohol  from  Fruit.  This  is  not  of  great  industrial  importance, 
although  in  certain  districts  and  in  certain  years  it  assumes  considerable 
magnitude.  In  Italy,  dried  figs  of  little  commercial  value,  carobs,  &c.,  are 
used  ;  and,  in  other  countries,  plums,  apples,  pears,  &c.  These  fruits  often 
give  an  irregular,  and  seldom  a  complete,  fermentation,  owing  to  conditions 
similar  to  those  encountered  with  beet-molasses.  Hence,  as  in  the  latter  case, 
use  is  made  of  very  active  yeasts  adapted,  where  possible,  to  these  special 
worts. 

The  alcohol  obtained  from  these  worts  has  a  characteristic  odour  indicating 
its  origin. 

•  *  Effront  observed  that  the  law  of  the  strongest,  which  is  often  verified  in  bacteriology — the  most  numerous 
and  powerful  bacteria  rendering  life  impossible  to  weaker  ones— scarcely  ever  holds  in  the  case  of  .alcoholic  fer- 
mentation, where,  even  though  the  harmful  bacteria  are  less  numerous  than  the  yeasts,  the  latter  are  seldom 
victorious,  the  bacteria  often  entirely  arresting  alcoholic  fermentation  even  when  the  conditions  are  favourable 
for  the  latter. 

According  to  Effront,  this  is  owing  to  the  different  specific  gravities  possessed  by  yeasts  and  bacteria,  which 
hence  live  in  different,  relatively  distant  strata,  so  that  there  is  no  opportunity  for  the  application  of  the  law 
of  the  strongest — -which  consists  in  the  production  by  certain  micro-organisms  of  poisonous  substances  preventing 
other  forms  from  developing.  Effront  hence  proposes  to  add  suitably  emulsified  resin  (colophony)  to  the  worts 
at  the  beginning  of  Uie  fermentation  ;  this  has  the  property  of  coagulating  only  the  bacteria,  which  become 
denser  and  are  brought  into  more  intimate  contact  with  the  yeast,  the  latter  then  being  in  the  most  favourable 
condition  for  the  annihilation  of  the  bacteria.  The  resin  itself  is  not  the  cause  of  the  death  of  the  bacteria,  as 
Effront  states  that  these  can  be  readily  cultivated  in  the  pure  state  in  presence o"f  resin  (private  communication). 


FIG.   139. 


142  ORGANIC    CHEMISTRY 

(3)  Alcohol   from  Woody  Substances.     This  is  a  subject  which  has  aroused  con- 
siderable interest  during  about  the  last  twenty  years.     Many  attempts  have  been  made 
to  transform  a  part  of  the  wood  (sawdust,  peat,  &c.)  into  fermentable  sugar  by  the  action 
of  acids  on  the  matter  (lignin)  encrusting  the  'wood  and  not  on  the  cellulose.     In  Chicago 
the  process  was   applied  on   a   vast  industrial   scale   according  to  A.  Classen's  patents 
(Ger.  Pats.  130,980,  1899,  and  161,644,  1904).     100  kilos  of  wood  (with  25  per  cent,  of 
moisture)  are  treated  in  an  autoclave  for  an  hour  with  about  100  kilos  of  aqueous  sulphur 
dioxide  and  sulphuric  acid  in  presence  of  steam  at  6  to  7  atmos.  pressure  (150°  to  165°). 
The  excess  of  sulphur  dioxide  is  eliminated  by  means  of  a  current  of  air,  the  residue  being 
boiled  with  water   or    extracted  in  diffusers,  and  the  liquid  neutralised  with  calcium 
carbonate  and  fermented  ;  x   about  8  litres  of  pure  alcohol  are  thus  obtainable,  and  the 
residues  are  partially  utilisable  for  making  paper.     It  is  not  improbable  that  in  the  near 
future  wood  and  the  more  economical  wood  refuse  will  replace  cereals  and  potatoes  in  spirit 
factories.2     In  France,  England,  and  the  United  States  there  were  in  1910  four  factories 
making  alcohol  from  wood  and  obtaining  yields  of  7  per  cent. 

(4)  Alcohol  from  Wine,    Lees,  Vinasse,  and  Withered  Grapes.     In  seasons  when 

1  Wood  thus  yields  a  product  contaiuing  35-36  per  cent,  of  solid  residue,  34-63  per  cent,  of  water,  10-97  per 
cent,  of  fermentable  reducing  sugar,  3-21  per  cent,  of  non-fermentable  reducing  sugars  (pentoses :  xylose,  &c.): 
0-35  per  cent,  of  sulphuric  acid,  and  0-77  per  cent,  of  other  acids. 

»  As  early  as  1820,  Braconnot  observed  that  sugar  is  formed  when  wood  or  even  cotton  cloth  is  treated  with 
sulphuric  acid.  Later  on  Melsens  obtained  a  good  yield  by  treating  cellulose  with  dilute  sulphuric  acid  in  an 
autoclave  under  pressure.  In  1860  Pettenkofer  investigated  this  process  and  showed  that  it  could,  at  that  time, 
compete  with  the  use  of  potatoes.  Still  later,  Basset  prophesied  a  yield  of  32  per  cent,  of  alcohol  from  the  similar 
treatment  of  wood  (I).  Simonson,  in  1889,  treated  wood  under  pressure  with  dilute  sulphuric  acid,  transforming 
25  per  cent,  of  it  into  sugar  (78  per  cent,  of  which  was  fermentable)  and  obtaining  a  practical  yield  of  6  to  7  litres 
of  pure  alcohol  (Third  International  Congress  of  Applied  Chemistry,  Berlin,  1903). 

Ileiferscheidt  (1905)  overcame  the  resistance  of  the  wood  to  penetration  by  liquid  acid  (met  with  also  by 
Classen)  by  causing  sawdust  to  absorb  two-thirds  of  its  weight  of  sulphuric  acid  (sp.  gr.  1-65)  and  subjecting 
the  mass  to  the  maximum  pressure  of  a  hydraulic  press  ;  simple  digestion  of  the  mass  with  water  and  nitration 
gave  a  fermentable  liquid  and  a  yield  of  6-5  per  cent,  of  alcohol  on  the  weight  of  wood  (pine,  containing  53  per 
cent,  of  cellulose)  taken.  A  similar  yield  is  obtained  by  treating  the  wood  with  five  times  its  weight  of  1  per 
cent,  sulphuric  acid  solution  at  a  pressure  of  8  atmos.  for  fifteen  minutes.  He  confirmed  the  observation  that  the 
pentosans  of  the  wood  do  not  ferment,  and  with  pure  cotton  he  obtained  as  much  as  13  per  cent,  of  alcohol. 

According  to  Xh.  Korner,  the  addition  of  oxidising  agents  or  of  ozone,  as  was  suggested  by  Both  and  Gentzen 
(1905),  is  of  no  advantage.  He  obtained  the  best  yields  by  heating  sawdust,  straw,  &c.,  with  0-5  per  cent,  sul- 
phuric acid  for  2  hours  in  an  autoclave  at  6  to  8  atmos. ;  only  a  small  part  of  the  molecular  complex  of  the  cellulose 
is  converted  into  fermentable  sugar,  and  he  obtained  a  yield  of  alcohol  equal  to  15  to  18  per  cent,  of  the  weight  of 
the  true  cellulose  in  the  wood.  Without  the  addition  of  sulphuric  acid,  the  yield  was  about  one-fourth  less. 

P.  Ewen  and  H.  Tomlinson,  of  Chicago  (U.S.  Pat,  938,308,  1909)  treated  400  kilos  of  sawdust,  straw 
or  stems  of  various  cereals  (with  30  per  cent,  of  moisture)  in  autoclaves  with  5  kilos  of  sulphuric  acid  of  60°  Be1, 
diluted  with  20  litres  of  water ;  after  complete  digestion  and  agitation  the  temperature  of  the  mass  is  brought 
in  fifteen  minutes  to  135°  to  160°  by  means  of  steam  under  pressure  ;  after  half  an  hour  the  temperature  is  lowered 
rapidly  to  100°  by  allowing  the  steam  to  escape,  and  the  sulphuric  acid  then  separated  in  the  usual  way.  By 
this  means  20  to  30  per  cent,  of  the  weight  of  the  cellulose  is  transformed  into  fermentable  sugar.  A  similar  process 
is  that  of  Eckstrom  (Norw.  Pat.  17,634,  1907). 

Classen's  process,  which  has  been  tried  on  a  large  scale  in  North  America,  has  exhibited  various  disadvantages  : 
the  time  required  for  treating  2  tons  of  wood  was  as  much  as  six  hours,  the  consumption  of  sulphuric  acid  was 
large,  part  of  the  sugar  was  destroyed,  and  frequent  repairs  were  necessary.  The  process  was  improved  by 
Ewen  and  Tomlinson,  and  was  worked  in  a  factory  near  Chicago.  Less  acid  was  used  and  the  treatment  main 
tained  only  for  forty  minutes,  the  autoclave  being  rotatable  and  made  of  steel  protected  outside  with  fireclay 
This  was  filled  with  sawdust,  sulphur  dioxide  (1  part  per  100  of  dry  wood)  being  then  passed  in,  and  subsequently 
steam  at  7  atmos.  After  forty  minutes,  the  vapours  of  water,  acetic  acid,  terpenes,  and  sulphur  dioxide  are 
passed  into  washing  or  absorption  vessels,  while  the  residual  darkened  sawdust  is  extracted  with  hot  water : 
the  aqueous  extract  is  neutralised  with  chalk,  filtered,  fermented,  and  distilled.  Rectification  yields  94  per 
cent,  alcohol  free  from  methyl  and  higher  alcohols,  and  containing  only  traces  of  furfural  and  other  aldehydes, 
The  cost  of  this  alcohol  seems  to  be  less  than  three-halfpence  per  litre  of  90  per  cent,  concentration. 

J.  Ville  and  W.  Mestrezat  (1910)  state  that,  whilst  cellulose  resists  dilute  solutions  (up  to  30  per  cent.)  of 
hydrofluoric  acid,  with  50  per  cent,  solutions,  100  grms.  of  cellulose  yield  50  grms.  of  glucose  1 

According  to  the  Swedish  patents  of  J.  H.  Vallin  and  of  Eckstrom,  alcohol  is  obtained  by  treating  the  waste 
sulphite  liquors  of  paper-mills  in  the  hot  with  sulphuric  acid  and  fermenting  the  liquid  containing  the  glucose 
formed.  The  hot  acid  liquid  has  to  be  neutralised  almost  completely  with  chalk  and  decanted,  the  residue 
being  then  pressed  in  a  filter-press  ;  the  liquid  is  then  cooled  on  piles  to  30°,  pitched  with  yeast,  aerated  during 
fermentation  (5  to  6  hours)  and  the  dilute  alcoholic  liquid  (0-7  to  0-8  per  cent,  alcohol)  distilled.  From  10 
cu.  metres  of  the  sulphite  liquors  are  obtained  60  litres  of  100  per  cent,  alcohol  (which  is,  however,  of  bad  flavour 
and  is  used  for  denaturation).  For  a  factory  producing  60  tons  of  cellulose  per  day,  i.e.  600  tons  of  waste  sulphite 
liquors,  the  cost  of  tanks,  pumps,  piles,  distilling  apparatus,  filter-presses,  &c.,  may  be  taken  as  about  £6000, 
and  the  alcohol  produced  (36  hectols.  per  day)  would  cost  (including  all  expenses,  but  excluding  taxation)  10s. 
to  11«.  per  hectolitre  at  100  per  cent,  strength.  The  problem  of  the  disposal  of  the  waste  liquors  (which  con- 
taminate the  rivers)  of  paper-mills  is  not,  however,  solved  in  this  way,  since  the  liquid  still  contains  much  decom- 
posable organic  matter  after  the  distillation  of  the  alcohol.  Before  starting  such  an  industry,  it  is  also  necessary 
to  consider  the  condition  of  the  market,  so  that  there  may  not  be  an  over-production  of  alcohol  and  hence 
depression  of  prices. 

In  1910  there  were  two  factories  in  Sweden  for  the  manufacture  of  alcohol  from  these  waste  sulphite  liquors : 
that  at  Billingfors  prepared  methyl  alcohol  (15  kilos  per  ton  of  wood  pulp)  by  H.  Bergstrom  and  H.  Fahl's  process  ; 
the  other  at  Skutskiir  manufactured  ethyl  alcohol.  For  every  ton  of  cellulose  there  are  obtained  8  to  9  tons  of 


ALCOHOL    FROM    WINE    RESIDUES 


143 


wine  is  abundant  and  prices  low  and  in  general  when  there  are  spoilt  wines  (at  6s.  to 
8s.  per  hectolitre),  it  is  convenient  to  extract  the  alcohol  from  them,  this  being  of  use 
in  the  preparation  of  liqueurs  and  spirits. 

The  distillation  presents  no  difficulty  and  is  carried  out  either  in  the  large  distilleries 
or  with  a  Guillaume-Egrot  apparatus  (see  p.  138),  which  is  mounted  on  a  car  so  as  to  be 
readily  transportable,  and  can  be  used  in  places  where  there  is  little  available  water,  since 
the  coolers  and  condensers  act  as  heaters  and  are  fed  with  the  wine  to  be  distilled.  It 
gives  directly  90  to  94  per  cent,  alcohol. 

In  the  same  way  as  wine,  fresh  lees  or  bottoms  from  wine  vats  (containing  4  to  6  per 
cent,  of  alcohol)  and  dried  grapes  l  are  treated. 

The  distillation  of  vinasse,  containing  2-25  to  3-5  per  cent,  of  alcohol,  is  of  considerable 
importance  in  Italy  ;  if  this  were  all  distilled  it  would  yield  about  250,000  hectols.  of 
pure  alcohol  annually  (for  a  production  of  40  million  hectols.  of  wine).  Of  the  various 
forms  of  apparatus  for  the  distillation  of  vinasse  only  those  of  Villard-Rottner  and  of 
Egrot  will  be  described,  as  they  are  the  commonest  and  differ  little  from  other  good  types. 

The  generator,  K  (Fig.  140),  of  the  Villard-Rottner  apparatus  sends  steam  from  the 
dome,  M,  into  the  three  boilers,  A,  in  succession,  the  steam  entering  at  the  bottom  and 


FIG.  140. 


FIG.  141. 


issuing  at  the  top  of  each.  These  three  boilers  contain  the  vinasse  mixed  with  an  equal 
volume  of  water.  The  vapours,  which  are  rich  in  alcohol,  pass  through  the  pipe,  E,  to 
the  dephlegmator,  G,  and  are  then  condensed  in  the  coil,  7,  at  a  concentration  little 
exceeding  50  per  cent.  When  the  first  boiler  is  exhausted  it  is  emptied  and  again  charged, 
the  steam  passing  meanwhile  through  the  second  and  third  ;  the  first  boiler  now  becomes 
the  third,  the  second  being  then  emptied,  so  that  two  boilers  are  always  in  use.  The 
hot  water  from  the  boilers  is  treated  separately  for  the  extraction  of  tartar  (see  this). 

In  the  Egrot  apparatus  (Fig.  141)  the  boilers,  A,  are  arranged  on  pivots,  so  that  they 

sulphite  liquors  containing,  either  dissolved  or  suspended,  as  much  as  12  per  cent,  of  organic  substances  and 
yielding  alcohol  at  loss  than  \\d.  per  litre. 

Considerable  interest  was  aroused  in  1901  by  the  English  patent  of  Dornig  and  Pratorius,  according  to 
which  human  faces  yielded  about  9  per  cent,  of  alcohol,  but  it  proved  to  be  a  fraud. 

There  has  been  much  discussion  recently  (1906-1907)  concerning  a  process  for  extracting  spirit  from  peat 
in  a  manner  similar  to  that  described  for  wood.  These  attempts  date  from  1870,  and  various  patents  were  filed 
in  1882-1891.  The  most  important  tests  were  made  in  Norway  in  1906  by  the  Reynaud  process  (1903),  in  which 
300  kilos  of  peat  were  treated  in  the  hot  with  700  kilos  of  water  containing  7  kilos  of  sulphuric  acid  (66°  Be.) 
under  3  atmos.  pressure ;  600  litres  of  liquid  were  thus  obtained  and  this  was  fermented  with  specially  selected 
yeasts  (Saccharomyces  ellipsoideus),  the  yield  being  25  litres  of  burning  spirit  at  an  inclusive  cost  of  about  4-5<7. 
per  litre,  which  is  about  double  the  cost  of  that  obtained  from  ordinary  starchy  materials.  In  1905,  the  Danif  b 
Government  offered  a  prize  for  the  improvement  of  this  process,  but  the  yield  was  not  increased  although  it  varies 
somewhat  (6  to  8  per  cent.)  with  the  quality  of  the  peat ;  in  all  cases  the  alcohol  obtained  in  this  way  is  too  costly. 

1  In  some  countries — at  certain  times  in  Italy — dried  grapes  are  used  for  the  production  of  alcohol,  especially 
Greek  grapes,  which  are  received  from  viticulturists  by  the  Greek  Government  in  payment  of  taxes,  and  are 
dried  and  placed  on  the  European  markets.  These  grapes  are  first  macerated  in  tepid  water,  then  crushed  and 
fermented  in  the  usual  way  ;  the  wine  obtained  may  be  used  for  mixing  with  other  wines  or  for  distillation.  In 
1905-1907,  in  order  to  help  the  crisis  in  the  South,  the  Italian  Government  granted  a  considerable  rebatement 
of  taxation  on  the  alcohol  obtained  from  grapes  The  Italian  distillers  then  began  to  import  large  quantities 
-of  Greek  grapes  (containing  50  to  55  per  cent,  of  sugar),  which  could  be  delivered  in  the  factory  at  about  13*.  per 
'  quintal,  so  that  the  southern  viticulturists  reaped  no  advantage  from  the  rebate,  which  was  hence  abolished. 


144  ORGANIC    CHEMISTRY 

can  be  inverted  and  rapidly  emptied.  Steam  from  the  boiler,  D,  extracts  the  alcohol 
from  the  three  boilers,  which  are  arranged  in  series,  as  before,  so  that  two  are  always  in 
use  while  the  third  is  being  emptied  and  recharged.  The  alcohol  vapours  pass  into  the 
dephlegmator,  B,  and  thence  into  the  spherical  rectifier,  C  ;  R  acts  as  a  condenser  and  is 
cooled  by  water  from  the  tank,  K.  The  condensed  alcohol  passes  along  the  tube,  m,  to  the 
test-glass,  M,  and  from  there  to  the  casks,  t,  at  a  concentration  of  55  to  60  per  cent. 

With  the  first  apparatus,  to  treat  100  quintals  of  vinasse,  yielding  about  8  hectols. 
of  brandy  at  51  per  cent.,  roughly  13  quintals  of  coal  are  consumed,  whilst  the  Egrot 
apparatus  uses  much  less  than  this  for  an  equal  yield.  The  brandy  thus  obtained  has 
almost  always  a  rather  unpleasant  flavour  and  is  often  used  for  rectification  in  the  ordinary 
way  (if  too  dilute  it  becomes  opalescent)  and  is  then  left  to  age  in  oak  casks  so  as  to  acquire 
a  pleasing  aroma.  This  result  is  obtained  more  rapidly  by  pasteurisation,  that  is,  by  passing 
the  brandy  through  a  coil  surrounded  by  water  at  60°  to  65°,  or  by  passing  a  current  of 
ozonised  air  through  it  (artificial  maturation).  The  name  cognac  is  given  to  the  finest  old 
French  brandies. 

Alcohol  from  cereals  can  be  distinguished  from  that  obtained  from  wine,  &c.,  as  the 
latter  always  contains  aldehydes  (see  later,  Rimini's  Reaction  and  Schiff's  Reagent). 

REFINING  AND  PURIFICATION  OF  SPIRIT.  After  the  introduction  of  rational 
methods  of  fermentation  with  selected  yeasts  and  of  more  perfect  rectifying  appliances, 
the  quantity  of  actual  alcohol  was  considerably  increased  and  it  was  generally  sufficiently 
pure  for  ordinary  commercial  purposes.  But  when  it  became  recognised  that  the  harmful 
effects  of  alcoholism  are  aggravated  by  the  presence  in  commercial  alcohols  for  liquors, 
&c.,  of  even  minimal  quantities  of  aldehydes  and  amyl  alcohol,  recourse  was  sometimes 
had  to  a  special  purification  or  refining  of  rectified  spirits  in  order  to  give  them  a  slight 
ethereal  odour,  which  is  greatly  valued.  Of  the  many  and  varied  substances  suggested 
for  the  purification,  mention  need  only  be  made  of  charcoal  in  lumps  calcined  and  cooled 
out  of  contact  with  air  and  placed  in  batteries  of  tall  cylinders  through  which  the  alcohol 
is  passed  ;  when  the  charcoal  becomes  inactive  it  is  revivified  by  means  of  superheated 
steam  at  600°.  The  charcoal  has  an  oxidising,  esterifying,  and  decolorising  action,  but 
it  does  not  fix  the  amyl  alcohol.  Treatment  with  fatty  oils  (which  retain  the  aldehydes) 
and  subsequent  distillation  are  also  used,  as  also  are  carbonates  of  the  alkalis  and  alkaline 
earths.  Treatment  with  oxidising  agents — ozonised  air,  potassium  permanganate  or 
dichromate,  nitric  acid,  chloride  of  lime,  &c. — has  the  disadvantage  of  forming  acetic 
acid  and  ethyl  acetate.  Consequently  Naudin  prefers  reducing  the  aldehydes  with  nascent 
hydrogen  formed  in  the  liquid  itself  by  means  of  a  copper-zinc  couple. 

R.  Pictet  has  devised  a  totally  different  process  :  owing  to  the  variations  (at  different 
temperatures)  of  the  maximum  vapour  pressure  of  volatile  liquids,  he  ascertained  that 
the  vapours  obtained  from  a  mixture  of  water  or  other  substances  with  alcohol  are  the 
richer  in  alcohol  the  lower  the  temperature  to  which  the  mixture  is  heated.  He  boils  the 
mixture  at  50°  to  60°  in  a  vacuum  and  then  rectifies  the  vapours  in  a  column  at  a  tempera- 
ture of  —30°  or  —40°,  obtained  by  means  of  a  sulphur  dioxide  refrigerating  machine. 
The  apparatus  is  somewhat  complex,  but  it  yields  a  well-refined  pure  spirit. 

TESTS  FOR  THE  PURITY  OF  ALCOHOL.  The  tests  mentioned  on  p.  109  will 
detect  traces  of  water  in  so-called  absolute  alcohol. 

If  alcohol  is  highly  purified  (puriss.),  10  c.c.  of  it,  mixed  with  1  c.c.  of  water  and  1  c.c. 
of  0-1  per  cent,  potassium  permanganate  solution,  should  maintain  its  red  colour  for  20 
minutes,  or  for  at  least  five  minutes  if  the  alcohol  is  termed  pure  ;  it  should  not  become 
turbid  on  dilution  with  water,  should  give  neither  an  acid  nor  an  alkaline  reaction  (with 
phenolphthalein),  and  should  remain  unchanged  with  ammoniacal  silver  nitrate  solution. 
To  test  for  aldehydes  the  alcohol  is  diluted  with  water  and  a  few  drops  distilled  and  tested 
by  Rimini's  reaction  (see  p.  109)  ;  or,  for  aldehydes  in  general,  by  Schiff's  reagent(fuchsine 
solution  decolorised  with  sulphur  dioxide  :  0-5  grm.  of  fuchsine  is  dissolved  in  500  c.c. 
of  water  and  decolorised  with  10  c.c.  of  sodium  hydrogen  sulphite  solution  of  sp.  gr.  1-26 
and  10  c.c.  of  concentrated  HC1)  ;  a  few  c.c.  of  this  reagent  are  coloured  red  when  shaken 
with  a  few  drops  of  alcohol  containing  traces  of  aldehydes. 

Of  more  importance  is  the  quantitative  estimation  of  the  fusel  oil 1  (always  formed  in 

1  Fusel  oil  has  a  varying  composition :  14-24  per  cent,  of  water,  15-45  per  cent,  of  ethyl  alcohol,  6-14  per 
cent,  of  normal  propyl  alcohol,  10-25  per  cent,  of  isobutyl  alcohol,  and  10-40  per  cent,  of  amyl  alcohol  of  fer- 
mentation. Traces  of  fusel  oil  may  be  detected  by  Kamarowsky's  reaction,  i.e.  with  salicylic  aldehyde  and 


ESTIMATION    OF    FUSEL    OIL 


145 


alcoholic  fermentation),  which  is  made  with  Herzfeld  and  Windisch's  modification  of 
Rose's  apparatus  (Fig.  142)  ;  the  method  is  based  on  the  property  possessed  by  chloro- 
form of  dissolving  the  higher  alcohols  and  a  very  little  ethyl  alcohol,  at  the  same  time 
increasing  in  volume.  The  alcohol  is  first  diluted  to  a  concentration  of  30  per  cent,  by 
volume  or,  better,  to  the  sp.  gr.  0-9656  at  15-5°  (see  Table,  p.  148  ;  if  the  alcohol  has  a 
concentration,  v,  less  than  30  per  cent.,  then  10  (30  —  v)  1  c.c.  of  absolute  alcohol  should  be 
added).  The  Rose  tube  (washed  with  alkali,  acid,  water,  alcohol,  and  ether  and  well 
dried)  has  a  cylindrical  expansion  at  the  bottom  containing  20  c.c.  up  to  the  first  mark  ; 
then  comes  a  tube  18  cm.  long,  holding  2-5  c.c.  and  graduated  in  O'Ol  c.c. ;  at  the  top  is 
a  pear-shaped  bulb  of  about  200  c.c.  capacity,  closed  with  a  ground  stopper.  The  tube 
is  placed  in  water  at  15°  and  into  it  are  introduced  by  a  long  funnel  reaching  to  the  lower 
bulb  20  c.c.  of  pure  chloroform  at  15°,  and  then  100  c.c.  of  the  alcohol 
diluted  to  30  per  cent,  at  15°  and  1  c.c.  of  sulphuric  acid  of  sp.  gr.  1-2857 
(38  per  cent.  H2SO4).  The  tube  is  then  closed,  inverted  so  that  all  the 
liquid  passes  into  the  pear-shaped  bulb,  shaken  vigorously  for  a  minute 
(150  shakes)  and  placed  erect  in  the  water-bath  at  15°,  where  it  is  left  for 
15  minutes  after  a  rotatory  movement  has  been  imparted  to  the  liquid  so  as 
to  collect  the  drops  of  chloroform  adhering  to  the  walls.  The  increased 
volume  of  the  chloroform  is  then  compared  with  that  obtained  in  a  similar 
test  with  pure  alcohol  of  the  same  concentration.  If  no  blank  experiment 
is  made,  1-64  c.c.  is  subtracted  from  the  increase  in  volume  as  being  due  to 
the  ethyl  alcohol  dissolved.  Each  0-01  c.c.  increase  hi  volume  of  the  chloro- 
form corresponds  with  0-006634  per  cent,  by  volume  of  fusel  oil.  For 
an  alcohol  rich  in  fusel  oil  which  gave  a  final  volume  of  chloroform  of 
22-14  c.c.  the  true  increase  in  volume  will  be  22-14 — 1-64-20=0-5  c.c. 
The  percentage,  /,  of  fusel  oil  by  volume  on  the  original  alcohol  (not  on 
that  diluted  to  30  per  cent.)  is  calculated  by  the  following  formula  : 

_  (c-6)(100  +  a) 
*  =  150 ' 

where  c  is  the  uncorrected  increase  in  volume  of  the  chloroform,  6  is  the 
correction,  1-64,  due  to  the  ethyl  alcohol,  and  a  indicates  the  number  of 
c.c.  of  water  or  absolute  alcohol  added  to  100  c.c.  of  the  original  spirit  to 
bring  it  to  30  per  cent.  Example  :  If  80  per  cent,  alcohol  is  used,  171-05 
c.c.  of  water  must  be  added  to  100  c.c.  to  break  it  down  to  30  per  cent.  ; 
100  c.c.  of  this  then  increases  the  volume  of  the  chloroform  from  20  to 
21-94  c.c.,  so  that: 


/  = 


(1-94 -1-64)  (100  +  171-05) 
150 


FIG.  142. 


=  0-54  per  cent,  by  volume  of  fusel  oil. 


The  furfural  is  determined  in  10  c.c.  of  distilled  alcohol,  to  which  are  added  10  drops 
of  colourless  aniline  and  2  c.c.  of  acetic  acid ;  if  a  red  coloration  appears  after  20  to  30 
minutes  furfural  is  present.1 

sulphuric  acid;  H.  Kreis's  modification  (1907)  of  this  colorimetric  reaction  yields  moderately  accurate 
results. 

Fusel  oil  is  now  largely  used  for  the  preparation  of  amyl  alcohol,  which  is  used  in  the  manufacture  of  fruit 
essences,  for  obtaining  nitrous  and  other  ethers,  and  for  gelatinising  explosives  (nitrocellulose)  ;  during  the  last 
five  years  the  price  of  fusel  oil  has  risen  from  65  to  170,  and  even  195  lire  per  quintal.  Pasteur  thought  that 
the  amyl  alcohol  (iso-  and  d-amyl)  arose  from  the  action  of  specific  bacteria  on  the  sugar.  But  in  recent  years 
F.  Ehrlich  has  thrown  doubt  on  the  formation  of  an  alcohol  with  a  branched  chain  from  a  sugar  with  a  direct 
chain,  and  has  now  shown  that  it  is  the  proteins  of  the  malt  and  their  decomposition  products  which  furnish 
nitrogen  to  the  yeast  for  the  synthesis  of  its  protein  constituents  and  at  the  same  time  form  amyl  alcohol.  In 
fact,  in  the  fermentation  of  a  pure  sugar,  Ehrlich  obtained  a  quantity  of  fusel  oil  proportional  to  the  quantity 
of  leucine  added ;  he  was  also  able  to  obtain  an  amount  of  fusel  oil  equal  to  7  per  cent,  of  the  alcohol  formed 
(the  usual  amount  being  0-4  to  0-6  per  cent.)  and,  further,  he  succeeded  in  reducing  the  formation  of  fusel  oil 
considerably  by  the  addition  of  ammonium  salts.  The  United  States  imported  2350  tons  (£122,000)  of  fusel 
oil  in  1910  and  2900  tons  (£255,000)  in  1911. 

1  The  estimation  of  small  quantities  of  benzene  in  denaturated  alcohol  can  be  carried  out  by  means  of  Rose's 
apparatus  (for  more  than  1  per  cent,  of  benzene).  The  best  method  is  to  dilute  100  c.c.  of  the  alcohol  to  a  con- 
centration of  24-7  per  cent,  by  weight  and  to  distil  the  whole  ;  the  first  10  c.c.  of  the  well-cooled  distillate  are 
diluted  to  20  to  25  c.c*  with  water  in  a  graduated  cylinder  ;  the  volume  of  the  benzene  which  separates  is  increased 
by  0-3  per  cent.,  which  is  a  constant  error  of  the  method.  This  method  of  Holde  and  Winterfeld  (1908)  is  based 
on  the  fact  that  when  the  alcohol  is  diluted  with  water,  the  pressure  of  the  benzene  is  considerably  augmented, 
whilst  that  of  the  alcohol  is  diminished. 

To  ascertain  if  methyl  alt-olio  as  present  in  alcohol,  1  c.c.  of  it  is  treated  with  1  c.c.  of  chromic  acid  solution 
II  10 


146 


ORGANIC    CHEMISTRY 


FIG.  143. 


ALCOHOL  METERS  OR  MEASURERS.  These  are  important  instruments,  as  in 
nearly  all  countries  the  manufacture  of  alcohol  is  subject  to  taxation  which  is  calculated 
on  the  quantity  of  alcohol  passing  through  a  sealed  meter  indicating  automatically  the 
corresponding  amount  of  pure  alcohol  (100  per  cent.).  The  Siemens  measurer  is  the  one 
most  used  (Figs.  143  and  144)  and  somewhat  resembles  the  gas-meter  (see  p.  50)  even  in 
its  registration.  The  alcohol,  which  enters  laterally  by  the  tube  I,  is  discharged  into  the 
inner  central  part  of  the  drum,  B,  i.e.  into  D,  this  being  divided  longitudinally  into  three 
small  chambers  furnished  with  apertures,  r1,  r2,  r3  ;  when  the  small  chamber  is  about  half 
full  the  alcohol  falls  into  the  large  lower  chamber  (e.g.  I),  which  has  a  capacity  of  4  Hires. 
When  this  chamber  is  filled  with  alcohol  the  level  of  the  latter  reaches  the  chamber  D, 
the  alcohol  then  falling  through  r2  into  //  and  displacing  the  equilibrium,  so  that  the 

drum,  B,  is  forced  round  in  the  sense 
of  the  arrow.  At  the  same  time  the 
first  4  litres  of  alcohol  are  discharged 
into  the  vessel  C,  which  communicates 
with  the  storage  reservoir  by  means 
of  the  tube  G.  The  compartment  II 
then  occupies  the  position  of  7,  and 
so  on.  The  axis  of  the  drum  is  con- 
nected with  a  suitable  automatic  regis- 
tering device.  At  the  same  time,  in 
the  cylinder  A  in  front  of  the  drum, 
the  alcohol  which  passes  through  raises 
the  float,  P,  more  or  less  according  to 
its  strength,  and  a  screw,  Q,  operates  the  lever,  T,  and  so  moves  the  index,  8,  the  point  of 
which  registers  the  alcoholic  strength  on  a  paper  ribbon  moving  along  a  carefully  calcu- 
lated curve,  X.  In  order  that  alcohols  of  different  concentrations  may  be  well  mixed 
and  so  influence  the  float  correctly,  they  are  delivered  at  E,  where  there  are  two  tubes  ; 
one  of  these,  a,  collecting  the  lighter 
alcohol,  rises  and  then  descends  (c),  dis- 
charging into  the  bottom  of  A  by  the  per- 
forated tube,  e ;  the  denser  alcohol  passes 
preferably  along  6  and  is  discharged 
through  the  perforated  tube,  d,  at  the  top 
of  A,  so  that  mixing  is  rapid  and  com- 
plete. The  registration  is  also  independent 
of  the  temperature  of  the  alcohol,  as  its 
expansion  (or  contraction)  is  allowed  for 
by  that  of  the  float. 

ALCOHOLOMETRY  AND  TESTS 
FOR  ALCOHOL.  As  a  rule  alcohol  is 
sold  practically  by  volume  and  not  by 
weight ;  1  litre  of  absolute  alcohol  weighs 
0-7937  kilo  or  1  kilo  measures  1-2694  litre. 
Industrially  alcohol  is  stated  to  be  of  so 
many  litre-degrees  ;  thus  100  litres  of  2  per  cent,  alcohol  would  contain  200  litre-degrees 
(100  x  2),  and  100  litres  of  50  per  cent,  alcohol  would  indicate  5000  litre -degrees,  which 
would  also  be  given  by  1000  litres  of  5  per  cent,  alcohol  ;  so  also  75-48  litres  of  100  per 
cent,  alcohol  would  be  expressed  as  7548  litre-degrees.  Alcohol  is  taxed  on  the  basis  of 
the  number  of  litres  of  absolute  alcohol. 

The  alcohol-content  of  an  aqueous  alcoholic  solution  is  deduced  from  the  specific 
gravity  determined  by  the  Westphal  balance,  or  directly  by  the  Gay-Lussac  alcoholometer 
(at  15°)  in  France,  or  by  the  Tralles  official  alcoholometer  (at  15-56°)  in  Italy  and  Germany, 
these  giving  the  percentage  of  alcohol  by  volume  contained  in  100  vols.  of  the  aqueous 

and  5  c.c.  of  water,  the  whole  being  then  carefully  distilled  until  only  0-5  c.c.  remains.  The  distillate  is  condensed 
in  a  long  air-cooled  tube  and  collected  in  a  test-tube,  the  condenser-tube  being  washed  out  with  2  c.c.  of  distilled 
water.  One  drop  of  ferric  chloride  and  two  of  albumin  solution  are  added  to  the  test-tube,  which  is  shaken ; 
5  c.c.  of  concentrated  sulphuric  acid  are  then  cautiously  added.  The  immediate  appearance  of  a  violet  ring  at 
the  zone  separating  the  two  layers  indicates  that  the  original  alcohol  contained  more  than  5  per  cent,  of  methyl 
alcohol ;  if  the  coloration  appears  after  a  minute,  the  proportion  is  1  to  5  per  cent,  and  if  after  two  minutes  less  than 
]per  cent.(A.  Vorisek,  1909). 


FIG.  144. 


ALCOHOLOMETRY 


147 


FIG.  145. 


alcohol.     The  reading  on  the  alcoholometer  is  made  at  the  point  of  the  stem  coincident 

with  the  lower  meniscus,  which  is  well  seen  by  looking  rather  below  the  surface  of  the 

liquid  (Fig.  145) ;  to  avoid  error,  the  alcoholometer  must  be  so  im- 
mersed that  the  whole  of  the  graduated  stem  is  not  wetted  (see 
vol.  i,  p.  75).  To  determine  the  percentage  by  weight  contained 
in  100  vols.  the  percentage  by  volume  is  multiplied  by  0-7937 
(specific  gravity  of  absolute  alcohol)  and  divided  by  the  specific 

gravity  of  the  alcohol  examined  (see  Table  on  p.  148). 

To  correct    the   alcohol  reading  determined  at  a  temperature 

different  from  15°  (or  15-56°  for  the  Gay-Lussac  alcoholometer), 

the   following   moderately  exact  formula   of    Pranco3ur  is  used  : 

x  =  c  ±  0-392,  where  x  is  the  number  of  Gay-Lussac  degrees  at 
15°,  c  the  number  of  degrees  found  at  the  non-normal  tempera- 
ture, and  t  the  number  of  degrees  the  latter  is  above  or  below  15°  ; 

the  +  sign  of  the  formula  is  used 
if  the  temperature  is  below  15°  and 
the  —  sign  if  it  is  above  15°.  Thus 
an  alcohol  showing  72°  on  the 
Gay-Lussac  alcoholometer  at  a 
temperature  of  28°  would  have : 
x  =  72  -  0-39  x  13  =  66-93°  Gay-Lussac  at  15°. 

With  dilute  alcoholic  liquids  of  complex  composi- 
tion (wine,  beer,  spirits,  &c.)  the  alcoholic  degrees  cannot 
be  deduced  from  their  specific  gravities.  But,  if  a  given 
volume,  e.g.  100  c.c.,  is  taken  and  distilled  (Fig.  147) 
until  all  the  alcohol  has  passed  over  (about  70  c.c.),  the 
distillate  can  be  made  up  to  the  original  volume  with 
distilled  water  and  its  specific  gravity  and  alcoholic 
strength  determined  in  the  usual  manner.  In  order  to 
prevent  frothing  during  the  distillation  of  beer  and  wine 
a  piece  of  tannin  or  a  few  drops  of  oil  are  added.  In 
some  cases  the  alcohol  of  wines  and  other  liquors  is 
determined  by  the  Geissler  vapoiimeter,  which  indicates 
the  pressure  of  the  vapours  from  the  liquid  heated  at  100°, 
By  means  of  a  Table  the  alcoholic  strength  may  be  read 
off,  knowing  the  vapour  pressure  ;  the  latter  is  measured 
on  a  special  barometric  U-tube,  B  (Fig.  146),  to  one  end 
of  which  is  fixed  the  bottle,  O,  containing  mercury  and 
the  alcoholic  liquid  and  placed  in  the  jacketed  vessel,  D, 
filled  with  steam  from  the  boiler,  A.  This  apparatus 
gives  results  which 
are  influenced  by 
several  factors  (dis- 
solved carbon  dioxide, 

salts,  &c.),  so  that  little  use  is  made  of  it.     In  more 

general   use  is  the  ebullioscope    devised  in   1823  by 

Groningen    and   subsequently  improved  by  Tabarie 

(1833),     Brossard-Vidal     (1842),     Malligand     (1874), 

Salleron    (1880),    and    Amagat    (1885).      Malligand's 

form  (Fig.  148)  is  the  most  commonly  used  and  is 

based  on  the   different    boiling-points   possessed   by 

alcoholic   liquids   of   different    concentrations.      The 

reservoir,  F,  is  provided  with  a  cover,  through  which 

pass  a  thermometer,  T,  bent  at  a  right-angle  and  a 

tube  surrounded  by  the  condenser,  R.     This  cover  is 

unscrewed  and  water  poured  into  the  reservoir  as  far  as  the  lowest  mark  inside,  the  cover 

being  then  screwed  on  (the  bulb  of  the  thermometer  does  not  touch  the  water).     The 

burner,  L,  is  then  lighted  under  the  small  chamber,  S,  which  is  traversed  by  a  brass  tube 

communicating  with  the  reservoir  ;  the  part  a'  being  rather  higher  than  a,  circulation  of 


146. 


FIG.  147. 


148  ORGANIC    CHEMISTRY 

WINDISCH'S  TABLE  FOR  CALCULATING  THE  STRENGTH  OF  AQUEOUS 

ALCOHOL  SOLUTIONS 


Sp.  gr. 
at 
15°  C. 

Grms.  of 
alcohol  in 
100  grms. 

C.c.  of 
alcohol  in 
100  c.c. 

Grms.  of 
alcohol  in 
100  c.c. 

Sp.  gr. 
at 
15°  C. 

Grms.  of 
alcohol  in 
100  grms. 

C.c.  of 
alcohol  in 
100  c.c. 

Grms.  of 
alcohol  in 
100  c.c. 

0-9999 

0-05 

0-07 

0-05 

0-9550 

31-66 

38-06 

30-21 

0-9992 

0-42 

0-53 

0-42 

0-9535 

32-55 

39-07 

31-01 

0-9985 

0-80 

1-00 

0-80 

0-9520 

33-42 

40-06 

31-79 

0-9978 

1-17 

1-48 

1-17 

0-9505 

34-28 

41-02 

32-55 

0-9970 

1-61 

2-02 

1-60 

0-9490 

35-11 

41-95 

33-30 

0-9963 

2-00 

2-51 

1-99 

0-9470 

36-21 

43-17 

34-26 

0-9956 

2-39 

3-00 

2-38 

0-9455 

37-01 

44-06 

34-96 

0-9949 

2-79 

3-49 

2-77 

0-9440 

37-80 

44-93 

35-66 

0-9942 

3-19 

4-00 

3-17 

0-9420 

38-84 

46-07 

36-56 

0-9935 

3-60 

4-51 

3-58 

0-9405 

39-61 

46-90 

37-22 

0-9928 

4-02 

5-03 

3-99 

0-9385 

40-62 

47-99 

38-09 

0-9922 

4-39 

5-48 

4-35 

0-9365 

41-61 

49-06 

38-93 

0-9915 

4-81 

6-01 

4-77 

0-9345 

42-59 

50-11 

39-76 

0-9909 

5-19 

6-47 

5-14 

0-9330 

43-31 

50-88 

40-38 

0-9902 

5-63 

7-02 

5-57 

0-9305 

44-51 

52-14 

41-38 

0-9896 

6-02 

7-50 

5-95 

0-9290 

45-22 

52-89 

41-97 

0-9889 

6-48 

8-07 

6-40 

0-9265 

46-39 

54-12 

42-95 

0-9884 

6-81 

8-48 

6-73 

0-9245 

47-32 

55-08 

43-71 

0-9877 

7-29 

9-06 

7-19 

0-9225 

48-24 

56-03 

44-47 

0-9872 

7-63 

9-48 

7-53 

0-9205 

49-16 

56-97 

45-21 

0-9866 

8-05 

10-00 

7-94 

0-9180 

50-29 

58-13 

46-13 

0-9860 

8-48 

10-52 

8-35 

0-9160 

51-20 

59-05 

46-86 

0-9854 

8-91 

11-05 

8-77 

0-9140 

52-09 

59-95 

47-57 

0-9849 

9-28 

11-50 

9-13 

0-9115 

53-21 

61-06 

48-46 

0-9843 

9-72 

12-05 

9-56 

0-9095 

54-10 

61-95 

49-16 

0-9838 

10-10 

12-50 

9-92 

0-9070 

55-20 

63-04 

50-03 

0-9832 

10-55 

13-06 

10-36 

0-9050 

56-09 

63-91 

50-71 

0-9827 

10-94 

13-53 

10-74 

0-9025 

57-18 

64-98 

51-56 

0-9822 

11-33 

14-01 

11-12 

0-9000 

58-27 

66-03 

52-40 

0-9817 

11-72 

14-48 

11-49 

0-8975 

59-36 

67-08 

53-23 

0-9811 

12-20 

15-07 

11-96 

0-8955 

60-23 

67-91 

53-89 

0-9807 

12-52 

15-46 

12-27 

0-8930 

61-31 

68-94 

54-71 

0-9801 

13-00 

16-04 

12-73 

0-8905 

62-39 

69-95 

55-51 

0-9796 

13-41 

16-54 

13-13 

0-8880 

63-47 

70-96 

56-31 

0-9791 

13-82 

17-04 

13-52 

0-8855 

64-54 

71-96 

57-10 

0-9786 

14-23 

17-54 

13-92 

0-8830 

65-61 

72-94 

57-88 

0-9781 

14-65 

18-04 

14-31 

0-8805 

66-67 

73-92 

58-66 

0-9776 

15-06 

18-54 

14-71 

0-8775 

67-95 

75-07 

59-57 

0-9771 

15-48 

19-04 

15-11 

0-8750 

69-01 

76-02 

60-33 

0-9766 

15-90 

19-55 

15-51 

0-8725 

70-06 

76-97 

61-08 

0-9761 

16-32 

20-05 

15-91 

0-8695 

71-33 

78-08 

61-97 

0-9756 

16-73 

20-55 

16-31 

0-8670 

72-37 

79-00 

62-69 

0-9751 

17-15 

21-06 

16-71 

0-8640 

73-63 

80-09 

63-56 

0-9747 

17-49 

21-46 

17-03 

0-8615 

74-67 

80-99 

64-27 

0-9741 

17-98 

22-06 

17-50 

0-8585 

75-91 

82-05 

65-11 

0-9736 

18-40 

22-55 

17-90 

0-8555 

77-15 

83-10 

65-94 

0-9731 

18-81 

23-05 

18-29 

0-8530 

78-17 

83-96 

66-63 

0-9726 

19-22 

23-54 

18-68 

0-8500 

79-40 

84-97 

67-43 

0-9721 

19-63 

24-02 

19-07 

0-8470 

80-62 

85-97 

68-23 

0-9716 

20-04 

24-51 

19-45 

0-8440 

81-83 

86-95 

69-00 

0-9710 

20-52 

25-08 

19-91 

0-8405 

83-23 

88-08 

69-90 

0-9705 

20-92 

25-56 

20-28 

0-8375 

84-42 

89-02 

70-65. 

0-9695 

21-71 

26-50 

21-03 

0-8340 

85-80 

90-09 

71-50 

0-9685 

22-49 

27-42 

21-76 

0-8310 

86-97 

90-99 

72-21 

0-9675 

23-25 

28-32 

22-47 

0-8275 

88-31 

92-01 

73-02 

0-9665 

24-00 

29-20 

23-17 

0-8240 

89-64 

93-00 

73-80 

0-9655 

24-73 

30-06 

23-86 

0-8200 

91-13 

94-09 

74-66 

0-9645 

25-45 

30-91 

24-53 

0-8165 

92-41 

95-00 

75-39 

0-9630 

26-51 

32-14 

25-50 

0-8125 

93-85 

96-00 

76-19 

0-9620 

27-19 

32-93 

26-13 

0-8080 

95-43 

97-08 

77-04 

0-9605 

28-19 

34-10 

27-06 

0-8040 

96-79 

97-99 

77-76 

0-9590 

29-17 

35-22 

27-95 

0-7990 

98-46 

99-05 

78-61 

0-9580 

29-81 

35-95 

28-53 

0-7925 

100-00 

100-00 

79-36 

0-9565 

30-74 

37-02 

29-38 

There  are  also  Tables  by  Hehner,  Haas,  Tralles-Brix,  Gay-Liissac,  &c.,  which  differ  little 
(at  most  0-1  to  0-2  per  cent.)  from  that  of  Windisch. 

For  any  specific  gravity  not  given  in  the  Table  the  corresponding  alcoholic  degree  can 
be  obtained  easily  and  with  sufficient  accuracy  by  proportional  interuolat 


ALCOHOL    STATISTICS,    ETC 


149 


liquid  takes  place  through  the  tubes  and  reservoir.  When  the  mercury  thread  of  the 
thermometer  remains  stationary  owing  to  the  water  boiling  and  the  steam  hence  having 
a  constant  temperature,  the  scale  is  adjusted  by  the  screw,  E,  so  that  the  zero-point  corre- 
sponds with  the  end  of  the  mercury  column.  The  reservoir  is  then  emptied,  rinsed  out 
with  the  wine,  &c.  (containing  less  than  15  per  cent,  of  alcohol),  and  then  filled  with  the 
wine  to  the  upper  mark,  so  that  the  thermometer  bulb  dips  into  the  liquid  when  the  cover 
is  screwed  on.  The  condenser  is  filled  with  cold  water,  the  burner  lighted,  and  the 
heating  continued  until  the  thermometer  again  shows  a  constant  reading  ;  the  corre- 
sponding scale-reading  then  gives  directly  the  percentage  of  alcohol  by  volume.  In  tho 
case  of  sweet  wines  or  beers  it  is  advantageous  to  dilute  with  an  equal  volume  of  water, 
the  result  given  by  the  instrument  then  being  doubled. 

An  ingenious  and  simple  ca pillar imeter,  recently  devised  by  Bosla  and  constructed  by 
the  Italian  (Enological  Agency,  Milan,  gives  the  alcoholic 
strength  of  wines  or  spirits  with  sufficient  accuracy  in 
three  or  four  minutes. 

The  Table  given  in  the  footnote  1  indicates  the  volume 
of  water  to  be  added  to  100  c.c.  of  alcohol  of  known 
strength  in  order  to  bring  it  to  a  definite  lower  concen- 
tration. This  Table  is  calculated  from  the  formula  : 

/S'x.  v         \ 
x  =  100  (—. ~r-    -  8} 

where  v  is  the  strength  of  the  more  concentrated 
alcohol,  S  its  specific  gravity,  S'  and  V  the  specific 
gravity  and  alcoholic  strength  required,  and  x  the 
quantity  of  water  to  be  added  to  100  c.c. 

STATISTICS,  FISCAL  REGULATIONS,  DE- 
NATURED ALCOHOL.  The  annual  production  of 
alcohol  is  now  about  21,000,000  hectols.,2  and  of 
this  23  per  cent,  is  made  in  Germany  (the  taxation 
amounting  to  £7,600,000  in  1907  and  £8,000,000  in 
1909  ;  in  1911  the  consumption  of  alcohol  in  Germany 
fell  to  3,650,000  hectols.),  20  per  cent,  in  European 
Russia,  16  per  cent,  in  Austria-Hungary,  14  per  cent, 
in  France,  15  per  cent,  in  the  United  States,  10  per  cent,  in  England,  and  1-4  per  cent,  in 
Italy.  In  1908  Turkey  imported  about  175,000  hectols.  of  alcohol  (one-half  from  Russia), 


FIG.  148. 


Concen- 

GIVEN ALCOHOL  AT 

tration 

desired 

95% 

90  % 

85% 

80  % 

75% 

70% 

65% 

60  % 

55  % 

50% 

by  vol. 

by  vol. 

by  vol. 

by  vol. 

by  vol. 

by  vol. 

by  vol. 

by  vol. 

by  vol. 

by  vol. 

90% 

6-4 

85 

13-3 

6-56 

80 

20-9 

13-79 

6-83 

75 

29-5 

21-89 

14-48 

7-20 

70 

39-1 

31-10 

23-14 

15-35 

7-64 

65 

50-2 

41-53 

33-03 

24-66 

16-37 

8-15 

60 

63-0 

53-65 

44-48 

35-44 

26-47 

17-58 

8-76 

55 

78-0 

67-87 

57-90 

48-07 

38-32 

28-63 

19-02 

9-47 

50 

95-9 

84-71 

73-90 

73-04 

52-43 

41-73 

31-25 

20-47 

10-35 

45 

117-5 

105-34 

93-30 

81-38 

69-54 

57-78 

48-09 

34-46 

22-90 

11-41 

40 

144-4 

130-80 

117-34 

104-01 

90-76 

77-58 

64-48 

51-43 

38-46 

25-55 

35 

178-7 

163-28 

148-01 

132-88 

107-82 

102-84 

87-93 

70-08 

58-31 

43-58 

BO 

224-4 

206-22 

188-57 

171-05 

153-53 

136-34 

118-94 

101-71 

84-54 

67-45 

25 

287-0 

266-12 

245-15 

224-30 

203-61 

182-83 

162-21 

141-65 

121-16 

100-73 

20 

381-8 

355-80 

329-84 

304-01 

278-26 

252-58 

226-98 

201-43 

175-96 

150-55 

15 

539-5 

505-27 

471-00 

436-85 

402-81 

368-83 

334-91 

301-07 

267-29 

233-64 

10 

859-0 

•^ 

804-50 

753-65 

702-89 

652-21 

601-60 

551-06 

500-50 

460-19 

399-85 

_^ 

c.c.  of  water  to  be  added  to  100  c.c.  of  the  more  concentrated  alcohol. 

For  example,  if  an  alcohol  of  90  per  cent,  by  volume  is  to  be  diluted  to  50  per  cent,  by  volume,  to  100  c.c. 
of  the  former  must  be  added  84-71  c.c.  of  water. 
1  See  Table  on  next  page. 


150 


ORGANIC    CHEMISTRY 


For  every  100  litres  of  alcohol  consumed  as  beverages  the  following  amounts  are  used 
for  industrial  purposes  :  54  litres  in  Germany,  19  in  Austria,  18  in  France,  and  14  in 
England. 

These  figures  indicate  the  countries  where  alcoholism  is  causing  the  greatest  amount 
of  harm.1 

PRODUCTION  OF  ALCOHOL  IN  THOUSANDS  OF  HECTOLITRES 


1902-3 

1904-5 

1905-6 

1907-8 

1908-9 

Observations 

Germany 

3383 

3791 

4020 

4500 

Austria-Hungary 

2318 

2480 

2700 

2650 

Russia     . 

3855 

4196 

4500 

2700 

United  States  . 

2900 

2900 

2900 

France    . 

1800 

2500 

2700 

2538 

England 

1297 

1300 

1284 

1400 

Holland  . 

354 

367 

351 

Belgium 

328 

329 

389 

Sweden   . 

186 

195 

220 

(Imports        in 

1909  :  12,000 

hectolitres) 

Italy 

173 

300 

293 

463 

Denmark 

169 

155 

154 

In  Germany  the  exportation  varies  considerably  :  313,400  hectolitres  in  1902,  14,000  in  1904,  194,000  in  1906, 
and  9700  in  1908. 

1  Alcoholism.  The  abuse  of  alcoholic  beverages  is  leading  to  the  ruin  and  decadence  of  certain  nations,  since  it 
is  largely  the  cause  of  depopulation  and  produces  actual  decay  of  the  human  organism.  Alcoholism  produces  a 
diminution  in  stature,  as  is  shown  by  the  increased  numbers  of  those  unfit  for  military  service  ;  it  quickly  leads 
to  crime  and  folly,  and  renders  the  organism  easily  attackable  by  all  kinds  of  disease,  its  effects  being  felt  to  the 
third  generation. 

Alcohol  acts  as  a  poison  which  first  excites  and  exalts,  then  intoxicates  and  depresses  the  psychic  faculty 
more  or  less  permanently.  The  abuse  of  wine  and  spirits  is  the  real  cause  of  much  intestinal  catarrh  and  of 
certain  visceral  lesions,  and  sometimes  leads  to  chronic  nephritis,  heart-injury,  enlargement  and  inflammation 
of  the  liver,  hepatic  cirrhosis,  cerebral  apoplexy,  progressive  paralysis,  and  often  to  madness. 

Among  the  industrial  classes  it  is  thought  that  alcohol  warms,  prevents  cold,  and  gives  greater  strength  during 
work,  but  this  is  a  great  error  based  on  appearances.  Almost  as  soon  as  it  is  swallowed,  the  alcohol  of  wine  and 
spirits  is  absorbed  by  the  blood  by  means  of  the  capillaries  and  brought  into  contact  with  all  parts  of  the  organism, 
the  nervous  centres  are  then  more  or  less  paralysed,  and  the  numerous  capillaries  under  the  skin  dilate,  since 
an  increased  amount  of  blood  rushes  to  the  skin  itself.  The  drinker  has,  indeed,  a  red  face  ;  but  the  sensation 
of  great  heat  is  only  superficial ;  if  the  surroundings  are  cold,  the  heat  of  the  body  is  more  easily  dispersed.  This 
explains  why  drunken  men,  sleeping  on  the  roads  in  the  winter,  readily  die  of  cold.  Nansen,  the  famous  Polar 
explorer,  withstood  temperatures  52°  below  zero  without  using  alcoholic  liquors. 

The  International  Congress  on  Industrial  Diseases,  held  at  Milan  in  1906,  declared  that  the  use  of  alcohol 
"  is  unnecessary  for  the  nourishment  of  the  workman,  and  becomes  harmful  where  the  work  is  heavy  or  long. 
As  regards  useful  effects  in  the  food  rations  of  the  worker,  alcohol  may  be  advantageously  replaced  by  sugar, 
coffee,  and  tea."  Alcohol  may  diminish  the  using-up  of  fat  in  the  organism  and  hence  the  consumption  of  proteins, 
but  as  a  food  it  is  very  costly  and  of  little  effect. 

During  the  last  few  years  alcohol-free  wines  have  been  prepared  by  crushing  grapes  from  the  best  vineyards 
and  subjecting  the  must  to  filtration  and  pasteurisation  (heating  to  60°)  so  as  to  render  it  clear  and  prevent 
fermentation  ;  the  wine  is  then  stored  in  hermetically  sealed,  sterilised  bottles.  These  wines  retain  the  taste 
and  fragrance  of  the  grape  and  have  considerable  nutritive  value  since  the  sugar  of  the  grape  remains  unchanged 
(15  to  20  per  cent.). 

Alcohol  also  has  a  harmful  effect  on  the  reproduction  of  man,  this  explaining  the  slowness  or  absence  of  the 
increase  in  population  of  nations  consuming  much  alcohol ;  as  in  France,  where  £6,000,000  was  spent  in  1898 
on  so-called  aperitives  (absinthe,  bitters,  Ac.)  alone.  In  England  £60,000,000  is  spent  annually  on  spirits,  and 
in  Switzerland  even  £6,000,000.  Drink  causes  the  direct  or  indirect  death  of  about  45,000  people  annually  in 
France,  40,000  in  Germany,  50,000  in  England,  20,000  in  Belgium,  and  100,000  in  Russia.  In  Italy,  L.  Ferriani 
stated  that  627  cases  of  death  in  1904  were  evidently  due  to  acute  alcoholism.  Dr.  Marambat  affirms  that  in 
France  72  per  cent,  of  the  criminals  and  70  per  cent,  of  the  individuals  (121,688)  appearing  annually  before  the 
courts  make  excessive  use  of  alcoholic  liquors.  In  Germany,  A.  Baer  found  that  41-7  per  cent.  (13,706)  of  the 
prisoners  (32,837)  were  addicted  to  drink  ;  in  Switzerland,  it  is  41  per  cent. ;  and  in  England,  33  per  cent,  of 
those  sentenced  at  the  Assizes.  In  Holland,  four-fifths  of  the  crime  is  attributed  to  alcohol,  and  in  Sweden  three- 
fourths.  Similar  figures  to  the  above  have  been  giyen  for  Italy.  In  various  countries  it  has  been  found  that 
25  per  cent,  of  the  lunatics  are  excessive  alcohol  drinkers.  In  the  Salpi'triere  Hospital  of  Paris,  60  out  of  83 
babies  afflicted  with  epilepsy  had  alcoholic  parents.  In  Germany,  30,000  persons  are  attacked  every  year  by 
alcoholic  delirium  and  other  cerebral  disturbances  due  to  abuse  of  alcohol. 

Alcoholism  in  Germany  was  a  national  calamity  as  early  as  the  fifteenth  and  sixteenth  centuries,  when  to 
the  enormous  consumption  of  beer  was  added  that  of  brandy  and,  after  1550,  of  cereal  and  potato  spirit.  After 
the  eighteenth  century,  when  the  production  of  cereal  and  potato  spirit.,  became  a  great  industry,  their  consump- 
tion as  beverages  increased  enormously.  In  1905  the  annual  expenditure  for  alcoholic  drinks  amounted  to  47*. 
per  head,  or  £8  for  every  person  over  fifteen  years  old,  making  a  total  of  £120,000,000  for  the  whole  of  Germany, 
or  about  £80,000,000  for  the  working  classes  corresponding  with  12  per  cent,  of  their  wages.  Every  year  there 
are  200,000  cases  of  inebriety,  and  75  per  cent,  of  the  crimes  against  the  person  are  the  result  of  drunkenness. 
The  question  of  alcoholism  is  closely  connected  with  the  social  problem,  as  it  is  especially  among  the  working 
classes  and  the  ignorant  and  ill-nourished  that  the  victims  are  found. 

Abstainers  are  less  liable  to  illness  and  usually  live  longer,  as  is  shown  by  the  following  statistics.  The  Tables 
of  the  Sceptre  Life  Association  for  eleven  years  (1884-1894)  show  that  the  mortality  in  the  temperance  section 


ALCOHOL    STATISTICS 


151 


In  1874  the  average  consumption  of  alcohol  per  inhabitant  in  Italy  amounted  to 
6-5  litres,  and  hi  1898  to  10-23  litres,  to  which  must  be  added  about  100  litres  of  wine.1 

In  Italy  the  production  was  80,000  hectolitres  in  1878  ;  165,000  in  1888  ;  187,000 
in  1898-9  ;  306,700  in  1904-5,  90,000  being  from  cereals,  72,600  from  molasses, 
59,000  from  wine,  83,000  from  vinasse,  and  1725  from  fruit.  In  1907-8  Italy  produced 
463,000  hectolitres  and  exported  64,000  in  1908  (half  in  bottles)  ;  134,000  in  1909,  40,000 
being  in  bottles  and  7000  sweetened  or  rendered  aromatic  for  beverages,  and  95,000 
in  1910. 

In  1903  there  were  3275  distilleries  in  Italy  employing  8670  workmen.  In  1904-5 
spirit  factories  consumed  234,000  quintals  of  maize,  6000  of  durra,  and  17,000  of  barley, 
rye,  millet,  and  rice  ;  also  280,000  quintals  of  molasses  and  sugar  and  53,000  of  other 
materials.  To  these  must  be  added  575,000  hectolitres  of  wine,  2,600,000  quintals  of 
vinasse,  and  13,700  of  fruit. 

In  Germany  80  per  cent,  of  the  alcohol  comes  from  potatoes  (the  cultivation  of  which 
occupies  3,300,000  hectares  out  of  a  total  area  of  26,000,000  hectares  capable  of  cultiva- 
tion) ;  in  Austria  60  per  cent.,  in  Russia  50  per  cent.,  and  in  France  20  per  cent. ;  the  rest 
is  obtained  from  cereals  and  saccharine  products. 

The  origin  of  the  alcohol  produced  in  France  is  as  follows,  the  numbers  representing 
hectolitres  : 


From  starchy 
matters 

From 
molasses 

From 
beetroot 

From 
wine 

From 
cider 

Total 

1877   .       . 

163,204 

642,709 

272,883 

157,570 

9,468 

1,308,881 

1885   . 

567,768 

728,523 

465,451 

23,240 

-  20,908 

1,864,514 

1897   .     .  . 

484,637 

734,819 

798,484 

83,719 

26,579 

2,208,140 

1901    . 

269,074 

1,006,933 

578,628 

330,966 

115,220 

2,437,964 

1904   . 

380,710 

626,722 

992,149 

88,509 

— 

2,181,362 

f     about 

1908   . 

362,500 

448,000 

1,260,000 

468,000 

~ 

\  2,600,000 

In  Italy  the  tax  for  manufacturing  alcohol  was  21s.  per  hectolitre  at  100  per  cent,  in 
1871,  £4  in  1883,  £6  in  1885,  and  £7  4s.  in  1887  ;  to  this  the  sale-tax  of  £2  8s.  was  added 

(abstainers)  was  57  per  cent,  and  that  in  the  general  section  (non-abstainers)  81  per  cent.  In  times  of  epidemics 
nine  out  of  ten  non-abstainers  die  and  only  two  out  of  ten  abstainers. 

The  introduction  of  the  alcoholic  tendency  into  Africa,  as  a  result  of  colonisation,  wrought  such  havoc  qmong 
the  natives  that  the  International  Congresses  against  Alcoholism  held  in  Brussels  in  1899  and  1906  adopted  various 
prohibitive  and  fiscal  measures  to  save  the  black  race  of  Africa  from  the  terrible  plague.  Many  remedies  for 
alcoholism  have  been  proposed,  but  singly  they  are  almost  all  inefficacious,  though  more  useful  if  combined. 

Increase  of  the  price  of  drinks  and  diminution  of  the  number  of  shops  have  proved  almost  useless  in  France, 
Belgium,  and  England.  In  England,  however,  the  latest  increase  in  taxation  has  diminished  by  one-third  the 
consumption  of  spirit ;  the  amount  of  beer  has  fallen  from  31-4  to  25-8  litres  per  head  per  annum,  whilst  the 
consumption  of  tea  and  wine  has  increased.  In  the  United  States  the  enormous  taxes  on  alcohol  have  not 
diminished  the  consumption  of  liquors.  Sweden  has  obtained  good  results  by  making  a  State  monopoly  of  alco- 
holic drinks,  by  granting  licence  to  sell  only  to  trustworthy  persons,  by  giving  them  special  facilities  for,  and 
large  profits  on  the  sale  of  other  beverages  and  of  food,  by  abolishing  profit  on  alcoholic  drinks  and  by  making 
the  licencees  responsible  for  cases  of  drunkenness  on  their  premises.  This  example  has  been  partially  followed 
in  America  and  England,  and  many  temperance  associations  have  helped  by  opening  establishments  where  good 
food  and  drink  are  obtainable  at  low  prices,  alcohol  being  banned.  Another  effective  factor  against  alcoholism 
is  education  and  the  explanation  of  the  harm  done  by  it :  in  schools,  churches,  barracks,  the  streets,  workshops, 
books,  reviews,  newspapers, 'advertisements — indeed  everywhere  should  an  intelligent  campaign  be  waged  against 
alcoholic  liquor  which,  as  Gladstone  said  in  the  House  of  Commons,  commits  more  slaughter  in  our  days  than  the 
three  historic  plagues  :  famine,  pestilence,  and  war,  since  it  decimates  more  than  famine  and  pestilence  and  kills  more 
than  war,  and  is  in  all  cases  a  disgrace  often  lowering  man  below  the  level  of  the  brute. 

1  The  average  annual  consumption  per  head  in  litres  of  absolute  alcohol  in  the  form  of  different  beverages 
is  as  follows  : 


Germany 
Austria-Hungary 
France    . 
England  . 

Belgium  . 

Denmark 
Sweden  .         . 
Russia     . 
United  States  . 
Italy 


Beer 
4-8 
1-7 
1-3 
8-3 
8-7 
2-6 
2-3 
0-2 
3-4 
0-1 


Wine 
0-66 
2-1 

17-5 
0-2 
0-6 

0-06 

0-28 
12-0 


Spirits 
4-1 
5-1 
3-5 
2-3 
3-7 
7-0 
3-9 
2-5 
2-7 
2-0 


Total 

9-5 

8-9 

22-3 

10-8 

13-0 

9-6 

6-26 

2-7 

6-38 

14-1 


In  Sweden  27  litres  of  alcohol  in  the  form  of  spirits  were  consumed  per  inhabitant  in  1830. 


152 


ORGANIC    CHEMISTRY 


in  1888  (so  that  the  consumer  paid  about  23  pence  per  litre  in  taxation  alone  !)  ;  the 
sale-tax  was  abolished  in  1904.  A  rebate  of  90  per  cent,  of  the  tax  is  made  on  exported 
alcohol  (added  to  marsala,  vermouth,  &c.).  In  1903  alcohol  obtained  by  distilling  wine 
and  vinasse  and  destined  for  industrial  use  was  exempted  of  all  taxation,  and  to  alleviate 
the  crisis  in  the  wine  industry  it  was  proposed,  but  in  vain,  to  grant  a  substantial  bounty 
to  the  distillers  of  wine  and  vinasse.  In  1911  the  tax  was  raised  to  £10  16s.  per  anhydrous 
hectolitre  at  15-56°.  In  1910  the  Italian  exchequer  received  nearly  a  million  sterling 
in  alcohol  taxes. 

In  Germany  the  manufacturing  tax  of  ordinary  non-denatured  alcohol  varied  prior 
to  1909  from  64s.  to  72s.  per  hectolitre,  this  being  entirely  repaid  on  exported  alcohol, 
which  in  certain  cases  also  enjoyed  a  bounty  of  9s.  Before  1909  the  tax  was  based  on 
the  volume  of  the  wort,  so  that  all  distillers  tried  to  work  with  concentrated  worts  (up 
to  25°  Brix).  Nowadays  the  payment  is  made  on  the  volume  of  anhydrous  alcohol 
produced,  and  the  tax  varies  according  to  the  production,  which  is  established  every 
ten  years  for  each  factory  (contingent  production).  On  this  contingent  quantity  the  tax 
is  105  marks  (shillings)  per  anhydrous  hectolitre,  excess  production  paying  125  marks. 
There  are  then  supplementary  taxes  of  4  to  14  marks  to  protect  the  small  factories,  so  that 
a  hectolitre  of  alcohol,  costing  of  itself  28s.  to  32s.,  with  taxes,  costs  £7  4s.  to  £8  8s.  The 
German  Government  received  about  £8,000,000  in  alcohol  taxes  in  1908-9  and  expect 
in  the  future  to  raise  this  to  £14,000,000  ;  but  increase  in  the  taxation  has  been  followed 
by  a  diminution  of  25  per  cent,  in  the  consumption.  Potato  spirit  is  made  in  6400  large 
factories,  that  from  cereals  in  730  large  and  6600  small  factories,  that  from  molasses  in 
27  special  distilleries,  and  that  from  wine,  fruit,  and  yeast  by  about  60,000  small  dis- 
tilleries. In  Germany,  besides  the  concession  of  untaxed  denatured  alcohol  to  all  indus- 
tries, non-denatured  alcohol  is  also  allowed  free  of  taxes  to  scientific  laboratories  and  for 
medicinal  uses  and  military  explosives.  The  alcohol  of  spirituous  beverages  imported 
into  Germany  pays  a  Customs  tax  of  about  £14  16s.  per  quintal.  In  England  the  spirit 
duty  amounted  to  about  £30,000,000  in  1907. 

In  Prance  alcohol  for  drinking  pays  a  tax  of  £10  per  hectolitre,  whilst  industrial  spirit 
is  untaxed  (as  in  Germany),  and  is  sold  at  about  4-5  pence  per  litre. 

Denatured  Alcohol.  In  several  countries  denatured  alcohol  is  allowed  free  of  tax  to 
manufacturers,  and  in  Italy  in  1903  this  spirit  was  taxed  12s.  per  hectolitre  (100  per  cent.) 
instead  of  £8  (which  is  subject  to  25  to  40  per  cent,  bonus  if  made  from  vinasse  or  wine). 
Denaturation  is,  however,  allowed  only  for  the  manufacture  of  ether,  collodion,  mercury 
fulminate,  varnishes,  photographic  papers,  artificial  silk,  and  alcohol  for  heating  or 
illuminating  purposes.  In  1905  Italy  also  abolished  the  tax  of  12s.  for  denatured  alcohol 
of  whatever  origin  (cereals,  vinasse,  &c.),  but  there  remains  the  cost  of  the  denaturant, 
which  sometimes  amounts  to  2s.  Qd.  or  more  per  hectolitre — for  about  3  per  cent,  of  de- 
naturant composed  of  methylene,  acetone,  pyridine,  and  benzene. 

In  order  that  alcohol  intended  for  various  industries  may  not  be  used  for  beverages 
(wines,  liqueurs,  &c.),  the  Government  denatures  it  by  the  addition  of  various  substances  1 
— stinking,  coloured,  or  of  unpleasant  taste — which  cannot  be  separated  from  the  alcohol 


DENATURANTS 

Crude 
wood  spirit 

Crude 
pyridine 

Acetone 

Benzene 

Crude 
benzine 

per  cent. 

per  cent. 

per  cent: 

per  cent. 

per  cent. 

France      .         . 

7-5 

— 

2-5 

— 

o-r. 

Germany           .                  . 

1-5 

0-5 

0-5 

__ 



,,         (motors) 

0-75 

0-25 

0-25 

2-0 

.  

Austria     . 

3-75 

0-5 

1-25 

— 

.  

,,       (motors) 

0-5 

traces 

traces 

2'5 

— 

Russia 

10-0 

0-5 

VO 

.  — 



Switzerland 

5-0 

0-32 

2-2 

— 

— 

In  the  United  States  methyl  alcohol  and  pyridiue  are  used,  and,  for  special  purposes,  ether,  cadmium  iodide, 
ammonium  iodide,  &c. 

In  France  denaturation  costs  about  10  fr.  (8s.)  per  hectolitre,  and  the  Government  makes  a  rebate  of  9  fr. 
In  Germany  it  costs  only  2  marks  (shillings)  since  much  less,  although  sufficient,  denaturant  is  added.  In  Italy 
denaturation  is  possibly  excessive  and  too  expensive. 


DENATURED    ALCOHOL  153 

by  any  of  the  ordinary  means  (distillation,  &c.),  but  which  do  not  damage  the  alcohol 
for  its  industrial  use.  The  denaturant  should  vary  according  to  the  use  to  which  the 
spirit  is  to  be  put.  There  are  hence  in  all  countries  a  general  denaturant  for  alcohol  as 
fuel,  for  motors,  &c.,  and  special  denaturants.  As  colouring- matter,  traces  of  crystal 
violet  (hexamethyl-p-rosaniline  hydrochloride)  are  used  in  Germany.  Alcohol  intended 
for  the  manufacture  of  ether,  collodion,  and  artificial  silk  is  denatured  by  the  addition 
of  ether  and  sometimes  of  a  little  acetone  ;  in  Italy,  for  varnishes,  2  per  cent,  of  methylene, 
2  per  cent,  of  light  acetone  oils,  and  20  per  cent,  of  a  50  per  cent,  solution  of  sealing-wax 
are  used.  It  has  also  been  proposed  to  use  part  of  the  stinking  products  obtained  on 
distilling  certain  bituminous  shales. 

In  1906-7,  41,000  hectolitres  of  alcohol  were  denatured  in  Italy  with  the  general 
denaturant  for  fuel,  motors,  lighting,  &c.  (16,790  in  1903-4,  about  18,500  in  1904-5, 
over  30,000  in  1905-6,  and  almost  83,000  in  1910),  1031  hectolitres  for  making  ether 
(about  1100  in  1904-5  and  8120  in  1910),  38  hectolitres  for  collodion  (63  in  1910),  130 
hectolitres  for  the  manufacture  of  mercury  fulminate  (140  in  1910),  1625  hectolitres  for 
artificial  silk  in  1910,  50  hectolitres  for  photographic  paper  (1910),  995  hectolitres  for 
lacquer  according  to  the  Dermoid  patent,  and  1364  hectolitres  for  other  lacquers  (1910). 
In  France  23,000  hectolitres  out  of  a  total  of  1,488,000  were  denatured  in  1879  ;  in  1901 
153,000  hectolitres  with  the  general  denaturant  were  used  for  motors  and  lighting,  and 
98,130  hectolitres  with  special  denaturants  for  chemical  industries  ;  in  1904,  290,000 
hectolitres  with  the  general  denaturant  and  133,500  hectolitres  with  special  denaturants, 
the  total  production  being  2,180,000  hectolitres  ;  in  1907,  600,000  hectolitres  were  de- 
natured altogether  ;  and  in  1908,  about  626,670  hectolitres — 442,758  for  heating  and 
lighting,  12,054  for  varnishes,  21,300  for  celluloid,  1147  for  dyes,  359  for  collodion,  194 
for  chloroform,  950  for  tannin,  490  for  chloral,  138,346  for  ether,  fulminate  of  mercury, 
and  explosives,  6972  for  pharmaceutical  products,  587  for  scientific  purposes,  and  1514 
for  other  uses. 

In  the  United  States,  126,000  hectolitres  were  denatured  in  1908  and  173,000  hecto- 
litres in  1909  (after  the  law  of  1907).  In  1910-1911  the  United  States  consumed  250,000 
hectolitres  of  denatured  alcohol.  In  Norway,  in  1910,  400  hectolitres  were  denatured, 
and  the  consumption  of  spirits,  which  was  40,000  hetcolitres  in  1874,  diminished  to 
15,000  hectolitres  in  1910. 

In  Germany,  1,400,000  hectolitres  of  denatured  alcohol  were  sold  in  1904-5  (1,582,000 
hectolitres  in  1908),  of  which  36,000  were  for  motors  (in  1903  only  24,000  hectolitres  were 
used  for  this  purpose,  12,500  horse-power  being  developed).1  In  1909-1910,  1,883,000 
hectolitres  of  alcohol  were  denatured  in  Germany. 

Denatured  90  per  cent,  alcohol  now  costs  465.  per  quintal  in  Italy,  whilst  in  Germany 
it  costs  only  about  half  this,  namely,  25  marks  (shillings)  per  hectolitre  (after  1909,  with 
the  new  tax,  48s.),  in  Austria  26s.,  in  Switzerland  24s.  (retail),  and  in  Belgium  25s. 

UTILISATION  OF  DISTILLERY  RESIDUES.  All  the  components  of  the  prime 
materials  used  in  the  production  of  alcohol  are  found  (excepting  the  carbohydrates : 
starch  and  sugar)  in  the  residues  (grams,  spent  wash)  left  after  the  distillation  of  the 
alcohol. 

These  residues  formerly  formed  inconvenient  refuse,  since  they  readily  undergo  putre- 
faction and,  if  discharged  into  rivers  or  canals,  contaminate  the  water.  In  exceptional 
cases,  when  the  distilleries  are  in  large  agricultural  centres,  the  residues  are  used  in 
the  wet  state  for  cattle-food,  but  more  commonly  they  are  evaporated  and  dried,  these 
dried  grains  being  highly  valued  as  a  concentrated  fodder,  rich  in  proteins 2  and  having 
a  restricted  (1  :  3  to  1  :  5)  nutritive  ratio  (ratio  between  nitrogenous  and  non -nitrogenous 
substances).3  In  the  fresh  residues  two-thirds  of  the  part  which  is  not  water  is  dissolved 

1  An  automobile  weighing  1200  kilos,  on  a  journey  of  174  kiloms.  (109  miles)  at  30  kiloms.  (19  miles)  per 
hour,  consumed  11-3  litres  of  alcohol ;  under  similar  conditions,  10  litres  of  petrol  are  required.  For  an  8  h.p. 
car,  350  grms.  of  alcohol  or  500  of  petrol  are  used  per  horse-power  hour.  For  automobiles  and  explosion 
motors  in  general,  the  Paris  Omnibus  Company  uses  alcohol  mixed  with  50  per  cent,  of  benzene,  this  giving  a 
better  thermal  efficiency  (34  per  cent.).  A  domestic  25-candle  lamp  with  an  Auer  mantle  uses  about  2  grms.  of 
alcohol  per  candle-hour.  The  use  of  alcoholene,  a  mixture  of  alcohol  and  ether,  has  now  been  proposed,  and 
from  a  technical  standpoint  presents  advantages  over  alcohol  and  other  mixtures. 

*  The  average  percentage  compositions  of  the  principal  residues  will  be  found  in  the  Table  on  page  154. 

3  For  fodder,  the  nutritive  values  of  the  proteins,  fats,  and  non-nitrogenous  digestible  substances  are  in  the 
proportions  3  :  2  : 1,  so  that  the  commercial  value  of  a  fodder,  expressed  in  nutritive  units,  is  given  by  :  nitrogenous 
substances  x  3  -f  fatty  substances  X  2  +  non-nitrogenous  substances,  given  by  the  percentage  composition 
of  the  digestible  components. 


154 


ORGANIC    CHEMISTRY 


and  the  remaining  third  suspended  in  the  water.  Potatoes  give  about  10  per  cent,  of 
dried  residue,  malt  about  40  per  cent.,  and  maize  45  to  50  per  cent. 

It  will  hence  be  understood  how  distilleries  have  greatly  increased  the  raising  of  cattle 
and  consequently  production  of  stable  manure,  thus  contributing  to  the  fertilisation  of 
formerly  unfertile  lands. 

The  economics  of  the  drying  of  these  residues  has  always  constituted  a  difficult  problem 
owing  to  the  presence  of  more  than  90  per  cent,  of  water  in  which  part  of  the  nutritive 
products  is  dissolved  and  to  the  fact  that  the  dried  residues  sell  at  8s.  to  11s.  per  quintal. 
In  many  cases  the  liquid  portion  is  abandoned  and  the  solid  part  separated  by  filter- 
presses  or  centrifuges  ;  but  if  the  liquid  part  cannot  be  got  rid  of,  even  after  addition 
of  lime,  ferrous  sulphate,  &c.,  it  is  best  to  evaporate  it  by  means  of  the  hot  fumes  from 
the  flues,  the  operation  being  hastened  with  disc-stirrers  of  large  surface  and  with  fans.  The 
evaporation  is  sometimes  carried  out  in  a  vacuum  apparatus  (see  Sugar)  furnished  with 
stirrers,  by  which  means  a  marked  economy  in  fuel  is  effected  (see  also  vol.  i,  pp.  442- 
444). 


FIG.  149. 

Of  the  various  drying  systems  (Hatschek,  Meeus,  Porion  and  Mehay,  Venuleth  and 
Ellenberg,  Theisen,  Biittner  and  Meyer,  &c.),  we  shall  only  deal  with  that  of  Donard  and 
Boulet,  which  has  been  applied  with  advantage  in  France  and  recently  also  in  Italy. 

The  solid  residue  from  the  filters  or  centrifuges  (perhaps  mixed  with  the  evaporated 
residue  of  the  liquid  portion),  still  containing  more  than  50  per  cent,  of  water,  is  carried 
by  mechanical  transporters  into  the  vacuum  drying  apparatus  (Fig.  149),  consisting 
of  a  horizontal  cast-iron  cylinder  rotatable  about  a  hollow  axis  through  which  the  steam 
enters  or  issues  ;  its  length  and  diameter  are  2-5  metres.  Inside  are  a  number  of  tubes 
(heating  area  about  60  sq.  metres)  into  which  steam  is  passed  from  D,  the  condensed 
water  being  discharged  without  coming  into  contact  with  the  mass  to  be  dried.  At  the 

TABLE  OF  AVERAGE  PERCENTAGE  COMPOSITIONS  OF  THE  PRINCIPAL  RESIDUES 


Beetroot 

Potato 

Rye 

Maize 

Durra 

Barley 

liquid 

dried 

liquid 

dried 

liquid 

dried 

liquid 

dried 

liquid 

dried 

liquid 

dried 

Water     . 

91-0 

10-12 

94-0 

8-10 

91-0 

10-12 

90-6 

10-12 

90-3 

10-12 

75-0 

14-0 

Proteins 

0-9 

6-7 

1-3 

18-24 

1-9 

22-28 

2-0 

24-26 

2-0 

24-26 

4-0 

20-0 

Non-nitrogenous 

-\ 

matter 

I    7-2 

60-65 

2-6 

45-55 

5-2 

48-52 

4-9 

35-40 

5-1 

30-34 

10-0 

46-0 

Fatty  matter 

( 

1-3-1-6 

0-2 

3-4 

0-3 

5-6 

1-0 

12-16 

0-7 

12-14 

1-7 

7-0 

Cellulose 

•> 

13-15 

0-9 

9-11 

1-0 

5-7 

1-0 

10-12 

1-1 

14-16 

5-0 

16-0 

Ash 

10-12 

0-5 

1-2 

0-6 

4-6 

0-5 

5-6 

0-8 

7-8 

1-3 

5-0 

ALCOHOLIC    BEVERAGES:    WINE  155 

other  end,  by  means  of  the  perforated  axis,  G',  the  interior  of  the  cylinder  communicates 
with  a  double-action  exhaust  pump  to  carry  away  the  vapour  from  the  grains  which  are 
hsated  in  a  vacuum  of  700  mm.,  while  the  cylinder  slowly  rotates  (three  turns  per  minute). 
The  charge  consists  of  25  to  30  quintals  of  solid  grains,  which  are  dried  (to  15  per  cent, 
moisture,  it  then  keeping  well)  in  less  than  four  hours,  the  coal  consumption  being  about 
150  kilos.  By  thus  drying  at  a  relatively  low  temperature  (in  a  vacuum)  and  out  of 
contact  with  air,  the  oil  of  the  grains  does  not  become  rancid. 

Since  maize-grains  contain  as  much  as  15  to  18  per  cent,  of  fat,  it  is  sometimes' 
convenient  to  extract  them  in  one  of  the  forms  of  apparatus  described  in  the  section 
on  Fats. 

Special  interest  attaches  to  the  residues  from  Molasses  and  Beet,  since  these  contain 
special  nitrogenous  compounds  (amino-acids)  and  a  large  proportion  of  potassium  salts 
utilisable  for  fertilisers  or  for  chemical  products.  The  evaporation  of  the  liquid  part  of 
these  residues  may  be  carried  to  a  certain  stage  in  the  ordinary  vacuum  plant,  the  mass 
being  subsequently  completely  evaporated  and  the  residue  calcined  in  suitable  furnaces 
(Porion  model  in  France  and  Belgium)  which  are  similar  to  the  reverberatory  furnaces 
or  muffles  used  in  the  preparation  of  sodium  sulphate  (see  vol.  i,  p.  161).  Care  must 
be  taken  not  to  fuse  the  mass,  which,  when  discharged,  should  still  be  carbonaceous  and, 
indeed,  sufficiently  so  to  cause  it  to  burn  when  placed  in  heaps  outside  the  furnaces  ;  the 
greyish  mass  thus  obtained — known  in  France  as  salin — contains  :  water,  0-3  to  6  per 
cent.  ;  KC1,  6  to  10  per  cent.  ;  K2SO4, 10  to  14  per  cent.  ;  potassium  phosphate,  0-5  to  1 
percent.  ;  K2C03,  53  to  58  per  cent.  ;  Na2CO3,6to  9  per  cent.  ;  soluble  substances,  9  to 
14  per  cent.  By  this  treatment,  however,  all  the  nitrogen  compounds  are  lost  ;  but  in 
some  cases  these  are  used  for  the  extraction  of  methyl  chloride  (see  p.  96).  The  process 
for  extracting  pure  potassium  carbonate,  ammonia,  and  sodium  cyanide  is  referred  to 
in  vol.  i,  p.  435. 

During  recent  years  the  utilisation  of  these  nitrogenous  substances  has  assumed  great 
importance  :  according  to  the  Effront  patents  (1907),  the  amino-acids  are  utilised  by 
enzymic  processes1  for  the  preparation  of  organic  acids  and  ammonium  sulphate  (with 
each  hectolitre  of  alcohol  produced  correspond  25  kilos  of  ammonium  sulphate  and 
35  grms.  of  organic  acids,  principally  acetic,  propionic,  and  butyric).  Since  1902,  the 
Dessau  Sugar  Refinery,  and  since  1904  the  Ammonia  Company  of  Hildesheim,  have 
utilised  the  nitrogen  compounds  as  potassium  cyanide  and  ammonium  sulphate.  In 
1907  the  Ammonia  Company  utilised  60  per  cent,  of  the  nitrogen  of  the  residues, 
producing  potassium  cyanide  to  the  value  of  £80,000  and  ammonium  sulphate  to  the 
value  of  £20,000. 

ALCOHOLIC  BEVERAGES 

WINE.  Only  the  liquid  obtained  by  the  spontaneous  alcoholic  fermentation  of  the 
must  of  fresh  grapes,  without  any  addition,  should  be  called  wine.  The  fermentation 
i^  spontaneous  owing  to  the  presence  on  the  grapes  of  Saccharomyces  cerevisice. 

Grape  must  has  the  sp.  gr.  1-08  to  1-10  and  contains  70  to  86  per  cent,  of  water,  16  to  36  per 
cent,  of  sugar  (glucose  and  levulose,  which  reduce  Fehling's  solution) ;  1  to  3  per  cent,  of 
cream  of  tartar,  tartaric,  malic,  and  tannic  acids  ;  0-4  to  1  per  cent,  of  colouring,  aromatic, 
extractive,  gummy,  and  protein  substances,  and  mineral  salts.  If  the  musts  have  to 
be  transported  over  long  distances,  either  they  are  concentrated  in  a  vacuum  or  by  freezing, 
or  the  fermentation  is  interrupted  for  a  time  by  filtering  them.  One  quintal  of  grapes 
gives  60  to  70  litres  of  must  and  30  to  35  kilos  of  residue  (marc). 

By  fermentation  in  open  vats  the  sugar  is  transformed,  more  or  less  completely,  in 
7  or  8  days  into  alcohol,  large  quantities  of  carbon  dioxide  being  developed  and 
a  little  glycerol,  succinic  acid,  &c.,  always  being  formed.  With  more  than  25  per  cent, 
of  sugar,  sweet  wines  are  obtained,  and  with  less,  dry  wines.  Fermentation  cannot  yield 
more  than  15  to  16  per  cent,  of  alcohol,  as  with  more  than  this  proportion  the  yeast  dies. 
After  the  principal  fermentation,  when  the  wine,  without  the  marc,  is  placed  in  casks 
of  chestnut  or  oak,  a  slow  fermentation  goes  on,  this  ceasing  in  the  winter  ;  with  increase 
in  the  alcohol -content  and  lowering  of  the  temperature,  the  yeast  and  part  of  the  tartar 

1  Ehrlich  was  the  first  to  show  that  the  fermentation  of  amino-acids  is  produced  by  amidages.  Effront  (1908) 
found  that  amidases  occur  especially  in  top  beer-yeasts  and  in  aerobic  yeasts  which,  in  seventy-two  hours  at  40" 
are  able  to  transform,  e.g.  all  the  nitrogen  of  an  alkaline  asparagine  (fee  this)  solution,  and  almost  all  the  nitrogen 
of  the  yeast  itself  into  ammoniacal  nitrogen,  organic  acids  being  formed  at  the  same  time. 


156  ORGANIC    CHEMISTRY 

(slightly  soluble  in  alcoholic  liquids)  are  deposited.  In  the  spring,  the  clear  wine  is 
decanted  into  clean  (sulphured?)  casks,  which  are  kept  full.  It  can  now  be  placed  on 
the  market,  or  it  can  be  further  matured  by  clarifying  it  in  the  cask  (by  shaking  with 
albumin  and  a  little  tannin  and  allowing  to  stand)  and  by  decanting  and  filtering  it  several 
times  during  the  course  of  a  year  or  more  before  placing  in  well -cleaned  bottles  ;  the 
latter  are  corked  by  machinery  with  paraffined  corks.  As  time  goes  on,  the  wine  acquires 
a  pleasing  aroma,  this  process  being  hastened  sometimes  by  pasteurisation,  which  consists 
in  passing  the  wine  rapidly  through  coils  heated  to  about  60°  ;  this  process  ako  arrests 
certain  incipient  diseases,  which  would  otherwise  end  by  spoiling  the  wine  (acidity,  &c.). 
Sparkling  wines  are  obtained  by  saturating  the  cold  wine  with  carbon  dioxide  during 
bottling  or  by  bottling  sweet  wines,  the  fermentation  of  which  continues  slowly  in  the 
corked  bottle  ;  in  the  latter  case,  however,  a  deposit  forms  at  the  bottom  of  the  bottle. 

In  order  to  obtain  wines  of  constant  type  on  a  large  scale,  co-operative  wineries  have 
been  recently  instituted  in  France,  these  collecting  the  grapes  or  must  from  a  whole 
district,  mixing  it  and  preventing  it  from  fermenting  by  saturating  it  in  the  cold  with 
sulphur  dioxide  (70  grms.  liquid  SO2  per  hectolitre)  ;  in  this  way,  not  only  the  yeasts, 
but  also  the  moulds,  bacteria,  and  unpleasant  odours  are  destroyed  and  the  must  can 
then  be  kept  for  months  in  closed  vessels.  When  part  of  the  must  is  to  be  converted 
into  wine,  it  is  heated  at  50°  to  60°  in  a  vacuum  by  allowing  it  to  pass  down  a  kind  of  recti- 
fying column  (Barbet,  Ger.  Pat.  195,235,  1906),  the  sulphur  dioxide  thus  removed  being 
recovered  ;  selected  yeast  or  other  wine  rich  in  yeast  is  then  added,  the  resulting  wines 
being  of  uniform  and  improved  character,  although  somewhat  rich  in  sulphates.  These 
desulphurated  musts  might  well  be  used  as  non-alcoholic  wines.  There  are  also  special 
yeasts  capable  of  destroying  SO2  in  the  musts  and  of  starting  fermentation.  In  Italy 
much  has  been  said  in  favour  of  co-operation  in  1909  and  1910,  but  no  trial  has  been 
made  on  a  large  scale. 

The  proportions  of  the  most  important  components  of  wine  vary  between  wide  limits, 
owing  to  variation  of  the  vines,  soil,  climate,  system  of  wine-making,  and  season  (certain 
wines  contain  manganese,  sometimes  as  much  as  27  mgrms.  per  litre). 

It  is  hence  difficult  to  ascertain  if  there  has  been  an  artificial  addition  of  constituents 
similar  to  those  naturally  present  in  the  wine,  so  that  considerable  dilution  with  water  and 
addition  of  alcohol,  glycerol,  tartar,  sugar,  &c.,  are  not  easy  to  detect  if  they  do  not 
exceed  such  limits.  Natural  wines  may  contain  8  to  16  per  cent,  of  alcohol,  1-6  to  4  per  cent, 
(for  dry  wines,  and  as  much  as  20  per  cent,  or  more  for  sweet  wines)  of  dry  extract 
(obtained  by  evaporating  a  definite  volume  to  dryness  on  a  water-bath  and  drying  in 
an  oven  at  100°),  0-5  to  1-5  per  cent,  of  various  acids  and  tartar  (expressed  as  tartaric  acid) 
and  0-15  to  0-45  per  cent,  of  mineral  substances  (ash,  obtained  by  calcining  the  dry  extract)  ; 
the  glycerol  varies  from  one-seventh  to  one -fourteenth  part  of  the  alcohol.  Naturally 
these  variations  are  much  smaller  for  wines  of  a  certain  quality  and  year  and  obtained 
from  one  and  the  same  district,  for  which  the  results  of  numerous  analyses  have  been 
collected. 

In  Italy  the  following  minimum  legal  limits  have  been  recently  (Ministerial  Circular, 
1907)  established  as  those  which  must  be  reached  for  a  wine  to  be  called  natural  (except 
in  cases  where  genuine,  wines  of  the  same  origin  and  year  are  shown  to  give  lower  limits)  : 
alcohol,  8  per  cent,  by  volume  in  white  wines,  9  per  cent,  in  red  ;  dry  extract  without  sugar, 
1-6  (white),  2-1  (red)  ;  total  acidity  expressed  as  tartaric  acid,  0-5  (white),  0-6  (red)  ; 
ash,  0-15  (white),  0-2  (red)  ;  alkalinity  of  the  ash  in  c.c.  of  normal  alkali  per  litre,  11 
(white),  16  (red)  ;  the  glycerol  should  be  from  one-seventh  to  one-fourteenth  by  weight 
of  the  alcohol,  and  the  relation  between  ash  and  extract  (for  dry  wines  or  for  sweet  wines 
after  deducting  the  sugar)  should  be  about  1  :  10  ;  plastering,1  expressed  as  sulphuric 
acid,  should  not  exceed  0-02  per  cent. 

In  France,  and  now  also  in  Italy,  watering  of  a  wine  is  detected  by  adding  the  per- 
centage of  alcohol  by  volume  to  the  total  acidity  per  litre  expressed  as  sulphuric  acid  ; 
this  should  give  13-5  for  red  and  12-5  for  white  wines  (in  Milan,  12-5  is  allowed  for  red 
and  11-5  for  white  wine).  Wines  weak  in  alcohol  or  tartar  do  not  keep  well  in  the  warm 

1  In  order  to  prevent  certain  diseases  to  which  southern  wines  low  in  acidity  are  liable,  recourse  is  had  to 
plastering,  i.e.  the  addition  of  sulphites  or  bisulphites,  which  increase  the  quantities  of  sulphuric  acid  and  sulphates. 
Thus  some  wines  remain  clear  in  the  bottle,  but  become  turbid  and  dark  on  exposure  to  the  air ;  this  disease, 
termed  casse,  is  prevented  by  addition  of  potassium  bisulphite,  which  also  arrests  secondary  fermentation. 
To  make  certain  weak  wines  keep  better  in  summer  in  tapped  casks,  calcium  sulphite  is  added,  this  giving  a  slow 
evolution  of  sulphur  dioxide. 


TESTING    OF    WINE  157 

weather.  A  weak  wine  can  be  improved  by  either  mixing  with  stronger  wines  or  con- 
centrating by  freezing,  water  then  separating  in  the  form  of  ice  (this  method,  in  use  even 
in  the  Middle  Ages,  has  recently  been  patented  in  Italy  !) 

New  wine  has  sometimes  the  smell  and  taste  of  rotten  eggs,  i.e.  of  hydrogen  sulphide  ; 
this  can  be  remedied  by  decanting  it  into  casks  in  which  sulphur  has  been  burnt : 
2H2S  +  S02  =  2H20  +  3S.1 

From  the  vinasse  remaining  after  the  wine  is  drawn  off  a  little  rather  rougher  wine 
can  still  be  obtained  by  subjecting  it  to  considerable  pressure,  and  from  the  pressed  vinasse 
alcohol  (see  above)  and  tartar  (see  later)  can  be  extracted. 

The  testing  or  analysis  of  wine  is  usually  limited  to  determining  the  alcohol  (by  the 
method  described  on  p.  146),  dry  extract, '  ash  (see  above),  glycerol,  plastering,  and 
total  acidity,  and  to  testing  for  the  addition  of  colouring  -matter  and  other  adultera- 
tions.2 

Statistics.  The  countries  which  produce  the  most  wine  are  France,  Italy,  and  Spain. 
For  Italy  the  statistics  are  very  contradictory,  and  even  the  official  ones  are  erroneous  ; 
for  instance,  the  production  for  1909,  which  was  given  officially  as  40,000,000  hectols. 
was  officially  corrected  in  1910  to  60,000,000  hectols. 

1  To  desulphur  musts  and  wines,  use  is  sometimes  made  of  a  small  quantity  of  urotropine  (hexamethylene- 
tetramine) ;  such  addition  can  be  detected,  according  to  Fonzes-Diacon  and  Bouis  (1910)  by  distilling  25  c.c. 
of  the  wine  with  3  drops  of  sulphuric  acid,  acidifying  the  first  5  c.c.  of  distillate  with  1  c.c.  of  sulphuric  acid,  and 
observing  if  it  colours  a  solution  of  fuchsine  decolorised  with  sulphur  dioxide.  The  residue  from  the  distillation 
is  rendered  alkaline  with  magnesium  hydroxide  and  distilled,  the  vapours  distilling  over  being  condensed  in  a 
known  volume  of  N/10  sulphuric  acid,  which  is  titrated  back  to  ascertain  how  much  ammonia  distils  over  from 
the  urotropine. 

1  The  Total  Acidity  is  estimated  by  titrating  10  c.c.  of  the  wine,  diluted  with  water,  with  N/10  sodium  hydroxide 
solution,  using  blue  litmus  paper  as  indicator ;  multiplication  of  the  number  of  c.c.  of  NaOH  by  0-75  gives  the 
total  acidity  in  100  c.c.,  expressed  as  tartaric  add.  A  volatile  acidity  (acid  that  distils  in  a  current  of  steam) 
exceeding  0-1  per  cent.,  expressed  as  acetic  acid,  indicates  a  sour  wine. 

The  Cilycerol  is  determined  by  evaporating  100  c.c.  of  wine  to  about  10  c.c.  on  the  water-bath,  then  adding 
sand  and  milk  of  lime  until  it  is  strongly  alkaline  and  evaporating  to  dryness  ;  the  residue  is  taken  up  in  50  c.c. 
of  95  per  cent,  alcohol,  the  solution  boiled  and  filtered,  and  the  residue  washed  with  150  c.c.  of  hot  alcohol ;  the 
filtrate  is  then  evaporated  on  the  water-bath  to  a  syrup,  which  is  well  mixed  with  10  c.c.  of  absolute  alcohol  and 
15  c.c.  of  ether,  allowed  to  deposit,  filtered  into  a  tared  dish,  the  residue  on  the  filter  being  washed  with  a  mixture 
of  equal  volumes  of  alcohol  and  ether.  Evaporation  of  the  solvent  leaves  the  glycerol,  which  is  dried  in  a  steam- 
oven  and  weighed. 

Plastering  is  allowed  bylaw  up  to  a  maximum  quantity  of  total  sulphuric  acid  (of  sulphates)  corresponding 
with  2  grms.  of  normal  potassium  sulphate  per  litre.  Hence,  on  adding  to  50  c.c.  of  the  wine,  50  c.c.  of  a  solution 
of  BaCl2  (2-8  grms.  of  the  crystallised  salt  and  50  c.c.  of  HC1  to  a  litre),  boiling,  allowing  to  stand,  and  filtering, 
the  filtrate  should  give  no  further  precipitate  with  barium  chloride  solution,  that  already  added  being  exactly 
sufficient  to  precipitate  the  maximum  allowable  amount  of  potassium  sulphate.  Excessive  sulphuration  of  wines 
is  sometimes  masked  by  the  addition  of  urotropine  (see  above),  which  decomposes  into  ammonia  and  formal- 
dehyde, the  latter  fixing  the  sulphurous  anhydride ;  this  can,  however,  be  detected  by  Schiff's  reaction  (see 
Aldehydes). 

Artificial  Coloration.  100  c.c.  of  the  wine  are  evaporated  to  about  one-third  the  volume,  3  to  4  c.c.  of  10  per 
cent.  HC1  and  0-5  grm.  of  well  defatted  white  wool  being  then  added  and  the  liquid  boiled  for  five  minutes  ;  the 
solution  is  then  poured  off,  and  the  wool,  after  being  thoroughly  rinsed  in  running  water,  is  repeatedly  boiled 
with  fresh  quantities  of  water  acidified  with  HC1  until  the  latter  no  longer  becomes  coloured  ;  the  wool  is  again 
well  washed  with  water  and  boiled  for  ten  minutes  with  50  c.c.  of  water  and  15  to  20  drops  of  concentrated 
ammonia  solution,  the  wool  being  then  removed  and  the  boiling  continued  to  expel  the  ammonia  ;  the  liquid  is 
then  slightly  acidified  with  HC1  and  boiled  for  five  minutes  with  fresh  wool.  If  the  latter,  after  washing, 
remains  distinctly  red,  the  presence  of  artificial  coal-tar  colours  in  the  wine  may  be  certified  ;  but  if  the  colour 
of  the  wool  is  faint  or  indefinite,  the  colour  is  removed  with  water  and  ammonia,  and  the  solution  acidified  and 
boiled  with  fresh  wool ;  even  a  faint  red  coloration  of  this  confirms  the  presence  of  coal-tar  dye. 

L.  Bernardini  (1910)  finds  that  if  the  lower  end  of  a  strip  of  filter-paper  is  dipped  into  wine  coloured  with 
vegetable  or  animal  substances,  these  rise  to  a  greater  height  than  the  cenocyanin,  which  is  more  tenaciously 
fixed  ;  hence,  after  the  paper  has  been  dried,  different  parts  can  be  tested  for  artificial  colouring-matters  by  the 
characteristic  general  reactions  (see  Table  of  Colouring-Matters  in  Part  III). 

It  has  been  observed  recently  that  the  natural  colours  are  slowly  decolorised  (in  48  hours)  by  hydrogen 
peroxide,  whilst  the  artificial  ones  are  not, 

Salicylic  Acid  and  Saccharin  are  detected  as  in  beer  (see  later). 

Added  water  is  difficult  to  recognise  if  it  does  not  bring  the  constituents  of  the  wine  below  the  legal  limits 
(see  above),  and  sometimes  as  much  as  40  per  cent,  of  water  can  be  added  to  strong  wines  without  reaching  these 
limits.  However,  since  natural  wines  never  contain  nitrates,  which  are  present  in  almost  all  waters,  the  following 
test  may  be  made  :  100  c.c.  of  the  wine  are  treated  with  6  c.c.  of  lead  acetate  solution  and  filtered.  To  the  filtrate 
are  added  4  c.c.  of  concentrated  magnesium  sulphate  solution  and  a  little  pure  animal  charcoal,  the  liquid  being 
shaken,  allowed  to  stand  a  short  time,  and  then  filtered.  To  a  few  drops  of  the  decolorised  liquid  are  added  a 
few  crystals  of  diphenylamine  and  1  to  2  c.c.  of  concentrated  sulphuric  acid.  If  a  blue  coloration  is  formed,  the 
presence  of  nitrates  is  demonstrated — the  reagents  being  assumed  to  be  pure.  If  the  wine  is  watered  with  distilled 
or  condensed  water,  or  pure  rain  water,  the  reaction  for  nitrates  is  not  given. 

The  addition  of  Glucose  to  wine  or  liqueurs  is  detected  by  adding  to  the  wine  a  little  pure  yeast  (pressed  yeast) 
so  as  to  ferment  completely  any  grape-sugar  still  present  as  well  as  the  added  glucose.  Commercial  glucose, 
prepared  from  starch,  always  contains  a  small  quantity  of  unfermentable,  dextro-rotatory  substances,  so  that 
if  the  wine,  after  fermentation  is  complete  (when  no  more  CO,  is  evolved)  and  after  decolorisation  with  animal 
charcoal  or  with  a  little  lead  acetate,  still  exhibits  a  dertro-rotation  greater  than  0-5"  in  a  20  cm.  tube,  the  presence 
of, glucose  is  proved. 


158  ORGANIC    CHEMISTRY 

The  following  figures  represent  hectolitres  (1  hectolitre  =  22  gallons) 


France. 

Italy 

Production 

Production 

Exportation 

1875 

83,000,000 

28,000,000 

363,000 

1879 

25,000,000 

34,000,000 

1,075,000 

(phylloxera) 

* 

1884 

34,781,000 

21,000,000 

2,380,000 

1887 

24,333,000 

34,000,000 

3,603,000  (2,800,000  to  France) 

1889 

23,000,000 

22,000,000 

1,440,000    (commercial    treaty    with    France 

broken  in  1887) 

1893  . 

59,000,000 

32,000,000 

2,362,000     (750,000     to"     Austria-Hungary  ; 

300,000      to      Switzerland,1      and 

426,000  to  America) 

1897 

32,000,000 

28,000,000 

2,400,000 

1901 

58,000,000 

44,000,000 

1,334,000 

1902 

— 

35,000,000 

2,164,000  (976,300  to  Austria-Hungary). 

1903 

39,000,000 

— 

— 

1904 

— 

42,000,000 

1,200,000     (Austro  -Hungarian     market    lost 

by  new  commercial  treaty) 

1905 

57,000,000 

28,000,000 

980,000  (worth  £1,400,000) 

1906 

62,000,000 

30,000,000 

710,000 

1907 

66,070,000 

54,000,000 

920,000 

1908 

66,500,000 

52,000,000 

1,200,000 

1909 

66,000,000 

60,000,000 

1,450,000  (France  has  a  vine  area  of  1,625,630 

and  Italy  of  3,500,000  hectares) 

1910 

— 

42,000,000 

2,000,000 

In  the  Italian  exportation  is  included  that  of  marsala,  vermouth,  and  bottled  wine, 
this  amounting  in  1885  to  1,200,000  bottles  and  flasks  (including  vermouth  and  marsala), 
in  1894  to  3,000,000,  in  1897  to  4,720,000,  in  1904  to  8,120,000,  and  in  1905  to  9,000,000 
(worth  £440,000),  whilst  in  1891  France  exported  33,000,000  bottles  (worth  £3,800,000) 
and  to-day  has  an  enormous  export. 

The  world's  'production  of  wine  in  1902  was  126,000,000  hectolitres:  16,000,000  in 
Spain,  5,200,000  in  Austria,  2,000,000  in  Hungary,  5,000,000  in  Portugal,  3,500,000 
in  Algeria,  2,000,000  in  Germany  (formerly  3,700,000  ;  in  1906  1,636,000  and  in  1907 
2,492,000  from  118,600  hectares  of  vineyards,  in  1910  846,139  hectolitres),  2,300,000  in 
Russia,  almost  2,000,000  in  Turkey  and  Cyprus,  nearly  1,000,000  in  Greece  and  its  islands, 
2,300,000  in  Bulgaria,  2,700,000  in  Roumania,  500,000  in  Servia,  1,100,000  in  the 

1  The  following  is  a  statistical  resume  of  the  wine  imported  into  Switzerland  from  1906  to  1910  (in 
hectolitres) : 


From 

1906 

1907 

1908 

1909 

1910 

Italy               .                    •  i, 

137,843 

300,208 

531,776 

651,726 

828,559 

France 

273,731 

581,163 

363,769 

386,486 

216,909 

Spain 

123,587 

219,666 

415,052 

352,347 

422,775 

Austria 

53,411 

78,104 

69,634 

91,034 

110,608 

Greece 

9,370 

10,120 

12,209 

42,234 

64,874 

Algeria-Tunis 

19,520 

52,501 

17,342 

11,118 

10,714 

Germany 

10,009 

8,870 

7,619 

7,650 

5,504 

Turkey     .                             . 

5,743 

5,183 

3,637 

2,865 

2,451 

Other  countries 

50 

50 

62 

457 

Total  hectolitres 

633,566 

1,255,865 

1,421,290 

1,546,027 

1,675,427 

Total  value       .         . 

— 

— 

•"^ 

£1,430,800 

£2,255,840 

VARIOUS    WINES,    ETC.  159 

United  States,  1,500,000  in  Argentine,  2,500,000  in  Chili,  350,000  in  Brazil,  327,000 
in  Australia,  &c.  The  total  production  in  1909  was  estimated  at  160,000,000  hectolitres. 
The  average  annual  consumption  per  head  is  144  litres  in  France,  121  in  Italy,  and  116 
in  Spain.  In  Milan  in  1909  duty  was  paid  on  1,000,000  hectolitres,  the  Corporation 
receiving  £420,000,  and  the  consumption  per  head  being  200  litres. 

In  1905  Italy  exported  to  Germany  124,000  quintals  of  dessert  grapes,  whilst  France 
exported  only  78,000  quintals.  In  1892  Italy  exported  about  260,000  hectolitres  of 
wine  to  Germany,  but  less  amounts  in  subsequent  years.1 

MARSALA.  This  is  a  liqueur  wine  made  for  the  first  time  at  Trapani  in  1773  by 
J.  Woadhouse  of  Liverpool  to  compete  with  the  world-famous  Madeira.  In  1812  another 
large  establishment  was  started  by  the  Englishman,  Benjamin  Ingham,  and  in  1840 
Vincenzo  Florio's  factory  which  has  since  become  the  most  celebrated.  The  prime 
material  for  the  manufacture  of  Marsala  is  white  Trapani  wine  with  13  per  cent,  of  alcohol, 
to  which  is  added  (in  quantity  varying  for  different  types  of  Marsala)  the  must  (cotto)  of  very 
mature  white  grapes,  concentrated  in  open  boilers  until  two-thirds  have  evaporated  ; 
then  is  added,  in  varying  amount,  the  sifone,  obtained  by  filling  a  cask  to  the  extent  of 
three-fourths  with  clear,  must  from  a  very  ripe  white  grape,  and  one-fourth  with  pure 
alcohol  (free  from  tax  if  for  export),  mixing  and  allowing  to  age  so  as  to  develop  the 
Marsala  aroma. 

Mixtures  of  these  three  components  in  different  proportions  give  the  various  brands 
of  Marsala  :  the  Italian  brand  is  the  least  alcoholic  (16  to  17  per  cent.)  ;  the  original  English 
brand,  the  strongest  (up  to  24  per  cent,  of  alcohol) ;  while  the  Margherita  and  Garibaldi 
brands  are  of  intermediate  strengths  and  are  sweeter, 

In  1904  Italy  exported  in  cask  30,540  hectolitres  of  Marsala,  worth  £92,000  ;  in 
1905,29,765  hectolitres,  worth  £83,280,  and  51,000  bottles,  value  £2040  ;  in  1906,26,800 
hectolitres  ;  in  1907,27,677  hectolitres  ;  in  1908,24,900  hectolitres  ;  and  in  1909,24,800 
hectolitres,  of  the  value  of  £97,600,  together  with  136,000  bottles.  In  1910  the  exportation 
was  32,500  hectolitres. 

VERMOUTH.  This  was  prepared  formerly  in  Tuscany,  but  nowadays  almost 
exclusively  in  Piedmont,  where  the  industry  was  started  in  1835  by  Giuseppe  Cora  and 
A.  Marendazzo. 

The  prime  material  for  manufacturing  vermouth  is  the  muscat  wine  of  Asti  and  of 
the  Monferrato  heights,  which  contains  6  to  11  per  cent,  of  alcohol  and  2  to  4  per  cent,  of 
sugar  ;  with  this  is  mixed  2  to  5  per  cent,  of  a  vinous  infusion  of  aromatic  drugs  in  which 
wormwood  predominates  and  which  contains  also  sweet  flag,  juniper,  gentian,  &c.  ; 
finally  alcohol  is  added  to  bring  the  strength  up  to  15  to  18  per  cent,  and  sugar  to  the  density 
of  6°  to  9°  Be.  (if  for  exportation,  90  per  cent,  of  the  alcohol  and  sugar  taxes  are  refunded). 
Sparkling  vermouth  is  made  by  saturating  it  with  CO2  in  the  cold  under  pressure. 

It  cannot  be  said  that  in  the  manufacture  of  Marsala  and  vermouth  all  the  rational 
methods  prescribed  by  modern  oenotechnics  are  followed. 

The  production  of  vermouth  in  Piedmont  is  now  about  250,000  hectolitres,  the  exports 
(especially  to  America)  being  12,400  hectolitres  in  cask  and  31,214  hectolitres  in  bottle 
in  1902  ;  10,000  hectolitres  (£24,000)  in  cask  and  53,500  hectolitres  (£224,000)  in  bottle 
in  1905  ;  8960  hectolitres  in  cask  and  64,980  hectolitres  in  bottle  in  1906  ;  8600  hecto- 
litres in  cask  and  77,800  hectolitres  in  bottle  in  1907  ;  7874  hectolitres  in  cask  and  83,300 
hectolitres  in  bottle  in  1908  ;  10,176  hectolitres  in  cask  (£27,680)  and  100,000  hectolitres 
in  bottle  (£464,920)  in  1909  ;  20,400  hectolitres  in  cask  (£53,040)  and  173,670  hectolitres 
in  bottle  (£760,000)  in  1910. 

CIDER.  This  is  an  alcoholic  drink  obtained  by  the  partial  fermentation  of  the  juice 
of  apples  and  pears.  It  is  largely  used  in  the  north  of  France,  in  Germany,  and  in  Swit- 
zerland. It  is  consumed  almost  immediately  it  is  made.  In  France  the  production 
varies  from  8,000,0000  to  30,000,000  hectolitres,  part  of  which  is  distilled  to  produce 
alcohol  (30,000  to  70,000  hectolitres  of  alcohol). 

LIQUEURS.  These  contain  40  to  70  per  cent,  of  alcohol.  The  finest  are  those  obtained 
by  collecting  the  first,  more  highly  alcoholic  distillate  from  other  fermented  liquors. 
Such  are  brandy  (prepared  by  distilling  vinasse  or  wine  and  containing  45  to  55  per  cent,  of 
alcohol),  cognac,  kirschwasser  (obtained  especially  from  the  cherries  of  the  Black  Forest )f 

1  The  import  dutie  elevied  by  different  countries  on  Italian  wines  are  as  follows  :  Germany,  29*.  per  quintal ; 
Belgium  18«.  &d.  Holland,  34*. ;  England,  23s.  for  wines  with  less  than  14-84  per  cent,  of  alcohol,  and  54.*.  M. 
for  strosger  one  li  -.  i  45s.  ;  United  States,  54s.  6d.  ;  and  British  India,  33*.  6d. 


160  ORGANIC    CHEMISTRY 

rum  (prepared  principally  in  Jamaica  by  distilling  fermented  cane-sugar  molasses), 
maraschino  (prepared  from  small  Zara  cherries),  gin  (from  juniper  berries),  atole  or  chica 
of  South  America,  arrack  of  the  Arabs  and  Indians  (prepared  from  rice,  cane-sugar,  and 
coco-nuts),  schnapps  of  the  Germans  (potato  spirit),  &p. 

The  other  class  of  liqueurs  comprises  those  obtained  from  aromatic  substances,  sugar, 
and  more  or  less  concentrated  pure  alcohol.  In  this  way  are  obtained  rosoli,  anisette, 
absinthe  (alcoholic  decoction  and  distillation  with  wormwood) — much  used  in  France 
and  the  principal  cause  of  the  terrible  effects  of  alcoholism  (p.  150) — creme  de  menthe, 
creme  de  cafe,  &c.  ;  ratafia  from  fruit  must,  spirit,  and  sugar  ;  Chartreuse  (the  most  cele- 
brated was  that  prepared  by  the  Carthusian  monks,  before  their  expulsion  from  France 
in  1904,  from  balm-mint,  cinnamon,  saffron,  hyssop,  angelica,  sugar,  alcohol,  and  other 
ingredients),  coca  (from  Bologna),  curacao  (first  prepared  from  two  kinds  of  orange  in  the 
island  of  Curasao  in  the  Antilles),  kummel  (in  Russia  the  best  kinds  are  obtained  by 
distilling  brandy  or  alcoholic  liquids  with  Dutch  cumin  seeds  and  dissolving  pure  sugar 
in  the  highly  alcoholic  distillate).  It  is  unnecessary  to  mention  that  all  liqueurs,  even 
the  most  celebrated,  are  more  or  less  poorly  imitated  in  all  countries  with  mixtures  in 
no  way  resembling  the  original  types,  but  the  latter  always  command  very  high  prices. 

Cognac  is  a  brandy  prepared  especially  in  Charente  by  very  carefully  distilling  weak 
wines  of  special  vintages  and  refining  and  maturing  the  product  in  casks  of  Angouleme 
or  Limousin  oak,  which  gradually  imparts  to  the  spirit  a  pale  yellow  colour  and  a 
characteristic  aroma.  The  finer  and  older  brands  sell  at  as  much  as  £40  per  hectolitre. 

FERMENTED  MILK.  This  bears  the  following  names  according  to  the  locality 
and  method  of  its  preparation  and  the  nature  of  the  milk  from  which  it  is  made  :  kephir, 
koumis,  galazin,  leben  (Egypt),  and  mazun.  The  first  three  of  these  are  the  best  known. 

KEPHIR,  or  Kefir,  is  of  very  ancient  origin  among  the  Caucasian  highlanders,  who 
nowadays  make  enormous  use  of  it  and  jealously  keep  the  secret  of  its  preparation.  There 
is  a  legend  to  the  effect  that  Allah  was  the  first  to  make  it,  and  that  he  recommended  it 
as  a  remedy  for  various  diseases.  Kephir  is  simply  cows'  milk  (fresh  or  skim)  fermented 
by  the  addition  of  a  special  ferment  in  the  form  of  granules,  which  the  Russians  call 
"fungi  "  and  the  Tartars  "  grain  or  millet  of  the  Prophet,"  as  they  regard  it  as  discovered 
by  Mahomet.  It  was  only  in  1882  that  Dr.  Dmitrieff  called  the  attention  of  the  rest 
of  Russia  and  of  Europe  to  kephir  and  its  great  recuperative  properties  in  cases  of  lung 
diseases. 

Kern  and,  later,  Freudenreich  showed  that  the  alcoholic  fermentation  of  milk  with 
millet  of  the  Prophet  is  due  to  the  simultaneous  action  (symbiosis)  of  the  new  Saccharomyces 
kephiri  (similar  to  ordinary  Saccharomyces  ellipsoideus),  a  streptococcus,  and  a  bacillus. 
The  alcoholic  fermentation  of  milk-sugar  with  evolution  of  C02  takes  place  rapidly  and 
is  always  accompanied  and  followed  by  acid  fermentation  (lactic  acid),  which  partially 
dissolves  the  casein  (propep tones)  and  forms  a  very  fine  coagulation,  almost  a  frothy 
emulsion.  In  practice  the  kephir  granules  are  softened  with  tepid  water  (30°  to  35°)  for  a 
couple  of  hours,  the  milk  being  then  added  and  the  mixture  shaken  every  hour  for  eight 
hours  ;  it  is  then  sealed  up  in  clean  bottles  fitted  with  mechanical  stoppers  and  is  shaken 
now  and  then,  the  temperature  being  maintained  at  15°  to  20° ;  in  24  hours'  time 
the  kephir  is  ready  ;  it  forms  a  slightly  alcoholic  and  acidulated  dense,  frothing  liquid. 
If  the  kephir  is  left  in  closed  bottles  for  two  days,  the  pressure  increases  and  the  mass 
becomes  more  acid  and  more  liquid  ;  by  the  third  day  it  becomes  extremely  acid  and 
contains  up  to  about  2  per  cent,  of  alcohol,  and  after  this  it  is  inadvisable  to  drink  it. 

In  Italy  kephir  or  kephir-extract  is  placed  on  the  market  by  the  Borgosatollo  Dairy 
(Brescia)  and  kephir  dried  in  vacua  is  also  prepared  (Rosemberger,  Ger.  Pat.  198,869, 
1907). 

KOUMIS  is  similar  to  kephir,  and  of  equally  ancient  origin,  but  is  prepared  from 
mares'  milk.  In  Russia  there  are  various  sanatoria  which  make  efficacious  use  of  large 
quantities  of  koumis.  The  composition  of  the  latter  has  been  found  to  be  :  Water, 
94  per  cent.  ;  CO2,  0-9;  ethyl  alcohol,  1-7;  lactic  acid,  0-7;  lactose,  1-3  (before  fer- 
mentation 5-5)  ;  fats,  1-3  ;  proteins,  2-3  (largely  peptonised)  ;  salts,  0-3. 

GALAZIN  is  obtained  by  placing  skim  (cows')  milk,  with  2  per  cent,  of  sugar  and 
0-3  per  cent,  of  beer-yeast  in  strong,  tightly  stoppered  bottles,  and  allowing  fermentation 
to  proceed  for  twenty -four  hours  at  16°  ;  from  the  second  to  the  sixth  day  the  proportion 
of  alcohol  rises  from  0-3  to  1-5  per  cent.  Galazin  is  less  nutritious  than  kephir  or  koumis. 


BREWING 


161 


BEER 

This  is  another  alcoholic  liquor  saturated  with  C02  and  is  obtained  by 
fermenting  aqueous  decoctions  of  barley-malt  and  hops. 

The  ancient  Egyptians  were  acquainted  with  the  manufacture  of  beer  and  held  it  in 
great  regard.  Later  it  became  known  to  the  Ethiopians  and  the  Hebrews,  but  the  Greeks 
never  acquired  a  taste  for  beer.  The  industry  was  taken  by  the  Armenians  from  Egypt 
into  the  interior  of  Asia,  and  still  later  beer  was  manufactured  in  Spain  and  France,  but 
it  was  never  consumed  by  the  Romans.  In  Germany  beer  has  been  made  from  time 
immemorial. 

A  marked  improvement  in  the  manufacture  of  beer  dates  from  the  time  of  Charles 
the  Great,  when  hops  were  first  used. 


FIG.  150. 


FIG.  151. 


Lager  beer  (see  later)  was  prepared  as  early  as  the  thirteenth  century,  and  its  use  has 
since  been  greatly  extended  in  various  countries. 

In  England  the  manufacture  has  flourished  since  the  fifteenth  century,  the  famous 
porter  being  first  made  at  the  beginning  of  the  eighteenth  century. 

The  improvements  made  in  brewing  operations  by  the  introduction  of  scientific  methods 
have  led  to  a  very  considerable  development  of  the  industry  in  Germany  and  elsewhere. 

The  prime  materials  for  the  manufacture  of  beer  are  barley,  rice,  maize,  &c., 
hops,  water,  and  yeast. 

LA.  BARLEY  1  should  satisfy  the  following  requirements  : 

1  Barley  (botanical  species  Hordeum)  used  for  making  beer  is  of  two  types  :  two-rowed  (Fig.  150),  in  which 
the  corns  are  arranged  in  the  ear  in  two  rows,  one  on  each  side,  and  six-rowed  (Fig.151),  in  which  there  are  three 
rows  of  corns  on  each  side  of  the  ear.  Different  kinds  of  barley  can,  to  some  extent,  be  recognised  by  the  form 
of  the  small  basal  bristle  found  at  the  base  of  the  corn  inside  the  longitudinal  furrow.  The  value  of  barley  for 
brewing  purposes  is  largely  influenced  by  the  nature  of  the  soil,  climate,  methods  of  cultivation,  and  manuring. 
Barley  is  cultivated  in  all  countries  and  in  all  climates—in  Holland  and  also  in  Sicily.  It  is  difficult  to  keep 
II  II 


162 


ORGANIC    CHEMISTRY 


(a)  When  moistened  and  kept  at  25°  to  30°,  80  per  cent,  of  the  corns  should  germinate 
in  48  hours  and  90  to  95  psr  cent,  in  72  hours. 

•     (b)  Those  are  preferred  which  are  heaviest  (60  to  70  kilos  per  hectolitre)  and  contain 
about  62  per  cent,  of  starch,  about  10  per  cent,  of  protein,  and  12  to  14  per  cent,  of  moisture. 

(c)  The  skin  should  be  thin  and  the  colour  pale  yellow,  the  ends  of  the  corns  not  being 
brown. 

Barley  starch  swells  at  50°,  and  with  water  forms  a  paste  at  80°.     With  diastase  it 
begins,  unlike  potato  starch,  to  saccharify  as  soon  as  it  is  completely  transformed  into 
paste. 
!  B.  Wheat  is  sometimes  used,  together  with  barley,  for  pale  beers. 

C.  Maize  is  used  in  America  after  being  skinned  and  degermed,  the  germ  being  rich 
in  oil. 

D.  Rice  is  used  in  America  and  Scandinavia  with  the  barley. 

2.  HOPS.  The  female 
flowers,  dry  and  mature,  of 
Humulus  lupulus  (Fig.  152) 
are  used,  these  containing  10 
to  17  per  cent,  of  a  powder 
(which  can  be  separated  by 
shaking  and  sieving)  possess- 
ing the  aromatic  and  bitter 
principles  which  bestow  on 
the  beer  its  aroma  and  keep- 
ing qualities.1 

varieties  pure,  since  they  become 
modified  during  growth  owing  to 
crossing.  Only  by  the  rational 
system  of  selection  initiated  by  Dr. 
Nilsson  at  the  Svalof  Institute  is  it 
possible  to  fix  different  varieties 
with  constant,  well-marked  charac- 
ters suited  to  the  various  districts  in 
which  at  one  time  they  originated. 

From  a  commercial  point  of 
view,  the  weisjht  of  a  barley  is  of 
importance  and  good  qualities  give 
a  weight  of  40  grms.  per  1000  corns, 
or  62  to  67  kilos  per  hectolitre  for  thin 
barleys  and  as  much  as  70  kilos  per 
hectolitre  for  the  larger  ones.  The 
grains  should  have  a  floury  and  not 
a  vitreous  appearance  when  cut 
through,  and  there  should  be  few 
broken  corns  as  these  do  not  ger- 
minate and  become  mouldy  on  the 
malting  floor.  Germination  tests, 
made  on  500  or  1000  corns,  should 
show  at  least  95  per  cent,  of  ger- 
m  nated  corns  in  5  to  6  days.  With  barley  harvested  under  wet  conditions,  the  ends  of  the  corns  are  darkened. 

The  world's  production  of  barley  in  1906  amounted  to  315,000,000  quintals  ;  in  France,  in  1909,  10,800,000 
quintals  (or  17  million  hectols.)  were  grown  on  an  area  of  737,300  hectares ;  Italy  imported  104,000  quintals 
in  1907,  124,000  in  1908,  176,000  (value  £126,120)  in  1909,  and  178,000  (value  £128,120),  mostly  from  Austria- 
Hungary,  in  1910. 

1  The  best  hops  are  cultivated  in  Bohemia  (at  Saaz),  Bavaria,  Posen,  Wiirtemberg,  Baden,  and  Alsace- 
Lorraine,  where  they  are  picked  towards  the  end  of  August.  If  they  are  too  ripe  the  bracts  of  the  hop-cones 
open  and  lupulin  is  lost. 

The  hop  should  have  a  yellowish  green,  and  not  a  brown,  colour,  and  the  bracts  should  not  be  opened ;  a 
too  green  colour  indicates  that  the  hops  have  been  picked  in  an  unripe  condition.  The  seeds  have  no  value  for 
brewing  purposes,  but  the  largest  hops  are  of  least  value.  They  should  not  have  an  unpleasant  odour.  Since 
the  fresh  hops  contain  75  to  85  per  cent,  of  moisture,  so  that  they  will  not  keep,  it  is  necessary  to  dry  them  in  the 
air  or  in  ovens  at  25°  to  30°  with  a  strong  current  of  dry  air,  until  they  contain  only  12  to  15  per  cent,  of  moisture; 
they  will  then  keep  well,  even  for  a  year  or  more.  Their  keeping  qualities  may  be  improved  by  sulphuring  them 
(with  S02)  either  when  dry  or  during  the  drying.  Sulphuring  is,  however,  often  applied  to  inferior  hops  to  mask 
their  defects. 

The  better  qualities  are  seldom  sulphured  and,  when  they  are  well  dried,  are  kept  tightly  compressed  in 
large  sacks  or  in  evacuated  metal  cylinders.  They  may  also  be  kept  in  a  very  cool  place  (cold  store). 

The  bitter  flavour  and  keeping  properties  imparted  by  hops  depend  on  their  content  of  a-  and  p-bitter  acids, 
which  varies  from  6  to  18  per  cent,  and  is  determined  by  Lintner's  method  as  follows  :  10  grms.  of  an  average 
sample  of  the  hops  are  heated  in  a  flask  graduated  at  505  c.c.,  with  350  c.c.  of  light  petroleum  (b.pt.  30°  to  50°) 
for  six  hours  on  a  water-bath  at  40°  to  45°,  an  efficient  reflux  condenser  being  fitted  to  the  flask.  When  the  latter 
Is  cold,  it  is  filled  to  the  mark  with  light  petroleum  and  shaken,  the  contents  then  being  filtered.  100  c.c.  of  the 
filtrate,  mixed  with  80  c,c.  of  alcohol,  we  titrated  with  a  drcinormal  potassium  hydroxide  solution  in 


Fia.  152. 


STEEPING 


163 


3.  WATER.  Formerly  water  for  brewing  purposes  was  invested  with  a  mysterious 
importance,  but  nowadays  the  water  is  tested  in  a  much  more  rational  and  rigorous 
manner.  Preference  used  to  be  given  to  moderately  soft  water,  but  now  waters  of  medium 
hardness  are  regarded  as  best,  as  it  is  found  that  a  certain  quantity  of  calcium  sulphate 
aids  fermentation  ;  but  if  the  water  is  too  hard,  less  extract  is  obtained  from  the  malt 
and  hops.  Iron  is  also  harmful,  and  especially  so  are  waters  contaminated  with  bacteria.1 

The  principal  operations  in  the  manufacture  of  beer  are  as  follow  : 

(1)  CLEANING  OF  THE  BARLEY,  to  remove  dust,  soil,  stones,  damaged  and  light 
corns,  &c.  by  means  of  sieves,  fans,  &c. 

(2)  STEEPING  OF  THE  BARLEY  for  2  or 
3  days  in  water  at  11°  to  12°  in  order  that  it  may 
absorb  the  water  necessary  for  germination. 

For  this  purpose  use  is  generally  made  of  the 
Neubecker  tank  (Fig.  153)  made  of  iron  plates, 
opan  at  the  top  and  cone-shaped  at  the  bottom. 
In  the  middle  is  a  wide  perforated  pipe,  E,  which 
is  surrounded  by  the  barley  (500  to  3000  kilos). 
The  water  is  supplied  by  the  pipe  W,  and  is 
discharged  through  the  perforations  of  E,  thus 
covering  the  barley  ;  it  is  then  discharged  from 
the  top  of  the  tank  through  the  pipe  U,  the 
lighter  floating  corns  being  carried  away.  After  7 
or  8  hours  the  water  is  run  off  through  the  tap 
C,  and  the  moist  barley  left  exposed  to  the  air  for 
5  or  6  hours.  Fresh  water  is  then  introduced  and 
left  for  10  to  12  hours,  after  which  it  is  run  off 
and  the  grain  exposed  for  5  or  6  hours,  and  so 
on.  This  procedure  is  continued  for  30  to  50  hours  in  summer  or  70  to  100  hours 
in  winter,  the  corns  having  in  that  time  absorbed  about  40  per  cent,  of  water. 
Steeping  of  the  barley  in  lime-water  has  been  suggested  as  a  means  of  preventing 
abnormal  fermentations  (Windisch,  1901).  In  some  cases  steeping  is  preceded  by 
washing  the  barley  in  running  water  in  rotating  cylinders  ;  or  else  compressed  air  is 
forced  into  the  steeping  vessels  at  frequent  intervals,  so  as  to  stir  the  barley.  The 

of  10-15  drops  of  phenolphthalein  solution.  If  much  fat  is  present  an  aliquot  part  of  the  light  petroleum  solution 
is  evaporated  and  the  residue  extracted  with  methyl  alcohol,  which  does  not  dissolve  the  fat  and,  on  evaporation, 
gives  the  bitter  acids  ;  these  can  then  be  weighed. 

The  quality  and  commercial  value  of  hops  are  influenced  largely  by  the  nature  of  the  soil  and  the  quality 
of  the  manure  used,  as  well  as  by  the  variety  of  the  hop  itself. 

Chemical  composition  does  not  always  give  satisfactory  indications  for  judging  of  the  value  of  hops,  and  this 
is  almost  always  done  by  men  experienced  in  valuing  hops.  Hops  give  up  to  alcohol  22  to  30  per  cent,  of  extract, 
about  two-thirds  of  which  is  composed  of  a  resin  giving  the  bitter  flavour  and  acting  as  an  antiseptic  towards 
certain  bacteria  injuriously  affecting  the  keeping  of  the  beer,  although  it  has  no  influence  on  the  yeast.  The 
flavour  of  the  beer  is  also  considerably  affected  by  the  tannin  contained  in  the  hop  to  the  extent  of  2  to  4  per  cent. 

The  determination  of  the  ethereal  extract  is  also  employed  in  judging  of  the  quality  of  hops ;  with  good 
qualities,  after  evaporation  of  the  ether,  27  to  28  per  cent,  of  residue  is  left  (see  above,  Lintner  Test). 

The  total  area  of  the  earth's  surface  under  hops  in  1909  was  97,421  hectares  (of  which  29,000  hectares  in 
Germany)  and  the  production  varied  from  10  to  15  quintals  per  hectare.  Germany  imported  28,000  quintals  of 
hops  in  1908  and  36,360  in  1909,  but  exported  124,000  quintals  in  1908  and  88,000  in  1909.  The  hops  imported 
by  the  United  States  were  valued  at  £247,200  in  1910  and  at  £427,400  in  1911,  and  those  exported  at  £461,400 
in  1910  and  at  £851,600  in  1911. 

1  The  compositions  of  various  waters  are  as  follows  : 


FIG.  153. 


Good 

Medium 

Cad 

Dry  residue        ...... 

250-450 

450-550 

550-700      A 

Ferric  oxide  and  alumina  (Fe2Oa,Al2O3) 

0-1-5 

1-5-2-5 

3              1    .- 

Lime  (CaO)         

120-150 

150-200 

200-300       1    .2 

Magnesia  (MgO)           ..... 

20-50 

50-80 

80-120       1  3 

Sulphuric  acid  (SO,)   

20-60 

60-80 

100-200       j  ° 

Ammonia  ....... 

— 

— 

trace-1-5        /   <£> 

1         Q< 

Nitrates     ....... 



0-0-5 

0-5-1-5            j 

Organic  matter  (as  oxygen  absorbed)    . 

0-4-1-5 

1-5-2-0 

2-3              | 

Hardness  (French  degrees)  .... 

15-25 

25-35 

35-50        /    PH 

Number  of  bacteria  per  1  c.c. 

50-500 

500-4000 

4000-10,000 

These  numbers  are  only  indicative  apd  mupt  not  be  tefcen  too  strictly, 


164 


ORGANIC    CHEMISTRY 


steep-water  becomes  yellowish  brown  and  acid,  and  after  some  time  undergoes  lactic 
and  butyric  fermentations.  At  the  end  of  the  operation,  the  barley  is  discharged  through 
the  lower  aperture,  A,  by  undoing  the  screw,  B,  and  raising  the  tube,  E,  by  means  of 
the  lever,  D. 

(3)  GERMINATION  OF  THE   BARLEY.     The  steeped  barley  is  carried  to  the 
spacious  malting  floor,  which  is  fitted  with  numerous  windows  to  allow  of  the  renewal 

of  the  air  when  desired,  and  is  arranged  so  that 
the  temperature  can  be  maintained  constant  at 
15°  to  20°.  On  the  impermeable  floor  (of  cement 
or  asphalte),  the  barley  is  spread  out  in  a  layer 
50  to  60  cm.  deep,  and  on  the  second  day  the 
mass  is  moved  with  wooden  shovels  so  as  to 
reduce  the  depth  to  30  to  35  cm.,  this  being 
further  reduced  to  15  cm.  on  the  third  day. 
Every  8  Or  10  hours  the  grain  is  turned, 
the  floor  being  kept  well  ventilated.  The 
temperature  gradually  rises,  but  should  -  not  be  allowed  to  exceed  20°  ;  if  necessary 
it  can  be  modified  by  turning  more  often  and  thinning  out  the  barley.  After  the  second 
day  the  radicles  begin  to  sprout  and  later  the  plumule.  In  eight  to  ten  days  the  rootlets 
become  twice  or  three  times  as  long  as  the  corn  and  the  transformation  of  nitrogenous 
material  into  diastase  is  at  its  maximum  (Fig.  154  shows  the  various  stages  in  the  ger- 
mination of  barley).  The  germination  should  then  be  interrupted  so  as  not  to  lose  any 
part  of  the  diastase  formed,  the  green  malt  then  containing  about  40  per  cent,  of  moisture. 
A  floor  of  20  sq.  metres  is  sufficient  for  only  1000  litres  of  steeped  grain.  If  the  piece 
dries  too  much,  it  is  moistened  by  sprinkling  with  water.  In  order  to  prevent  mould- 
growth  when  the  floor  is  free,  it,  and  also  the  walls,  are  washed  with  1  per  cent,  calcium 
bisulphite  solution,  the  floors  being  then  well  dried  by  ventilation. 


FIG.  154. 


••- • v;  ;••:•.,..,••-.•••   '•' -.   ••?>>'•-...     -K^':  .••o>«v,'  'v.;^-  x  ;.-  -••..-•.>  ^u.^.:..^^^""-  ';v.\ «,;-  ,;<V;?^-'"\ 


FIG.  155. 


FIG.  156. 


The  germination  is  now  sometimes  carried  out  on  the  pneumatic  system,  use  being 
made  of  the  Galland  apparatus  (Figs.  155  and  156),  which  consists  of  a  double  sheet-iron 
drum,  T,  rotated  by  means  of  the  wheels  6  (one  rotatiqn  in  forty  minutes).  The  inner 
drum  is  perforated  and  is  filled  to  the  extent  of  four-fifths  with  barley  from  the  steeping 
tank,  W  ;  along  the  axis  of  the  cylinder  passes  a  pipe  which  is  also  perforated.  Air 
sucked  in  by  a  fan,  Z,  is  moistened  in  A  by  means  of  pulverised  water,  and  from  L  passes 
into  the  jacket  of  the  drum,  then  through  the  perforations  and  the  grain  to  the  central 
pipe,  m .  Thence  it  proceeds  to  8,  and  so  through  the  fan  Z  to  the  shaft  ;  a  thermometer 
here^shows  the  temperature  of  the  air,  and  if  this  becomes  too  high  the  speed  of  the  fan 


PNEUMATIC    MALTING 


165 


is  increased.  If  100  kilos  of  barley  are  taken  and  the  air  enters  at  12°  and  issues  at  20°, 
4500  cu.  metres  of  air  are  required  per  hour  ;  if  the  air  is  to  leave  at  16°,  10,000  cu.  metres 
per  hour  are  necessary.  The  germination  lasts  8  to  9  days. 

To  stop  the  germination,  a  current  of  dry  air,  heated  to  22°  to  25°  or  mixed  with  gas 
rich  in  C02  (to  diminish 
the  supply  of  oxygen), 
is  supplied  ;  in  a  short 
time  the  moisture  content 
of  the  grain  is  reduced 
from  40  per  cent,  to  20  to 
25  per  cent. 

For  a  malting  to'give 
continuously  2000  to 
5000  kilos  per  day,  three 
to  four  steeping- tanks  are 
used,  these  feeding  six 
to  eight  Galland  drums 
arranged  in  batteries  (Fig. 
157)  ;  6  to  10  horse -power 
are  required  for  turning 
the  drums,  driving  the 
fans,  &c.  FIG-  157' 

The  water  necessary  for  steeping  amounts  to  about  10  to  12  times  the  weight  of  the 
barley,  rather  less  being  required  to  moisten  the  air  for  pneumatic  malting.  The  steep-water 
can  hence  be  used  again  for  the  latter  purpose  if  at  any  time  the  water-supply  is  scarce. 


FIG.  158. 

Another  system  of  malting,  used  especially  in  France,  is  that  of  Saladin  (shown  in 
perspective  in  Fig.  158,  while  Fig.  159  shows  a  longitudinal  section  of  one  of  the  vessels 
and  Fig.  160  a  transverse  section  of  the  vessels).  There  is  one  vessel,  made  of  concrete 


1 

M 

p 

if 

<arri>A 

G=r^ 

""tSS?         L      "^l 

i 

"Q  "D~  D  ~D"D  B  "Q  n  T  D  D"C"  B  "n  o  ~G~D  a  a  Ta  o"o~  B"o 

t 

I 

C         L 

D 

« 

i 

FIG.  159. 


FIG.  160j 


and  fitted  with  a  perforated  false  bottom  of  sheet-iron,  for  each  day  that  the  germination 
lasts.  These  vessels,  B,  communicate  under  the  false  bottom  with  a  channel  containing 
a  fan  which  draws  moistened'air  through  the  mass  of  barlej'  in  the  vessel  (50  cm.  deep). 


166 


ORGANIC    CHEMISTRY 


Above  each  vessel  is  a  mechanical  turner,  A,  with  a  number  of  screws  which  rotate  in  the 
barley  as  the  turner  passes  along  the  vessel.  The  turner  can  be  transported  from  one 
vessel  to  another  and  is  put  into  operation  twice  a  day  at  first  (the  temperature  of  the 
barley  being  12°  to  14°),  then  four  times  a  day  (at  15°  to  18°),  and  finally  twice  a  day  (at 
18°  to  50").  In  some  maltings  a  saving  is  effected  by  operating  the  fan  only  at  intervals — 
when  the  temperature  rises.  Dry  air,  drawn  along  the  channels,  S,  is  finally  passed 
through  the  malt. 

The  advantages  of  the  various  mechanical  processes  over  the  old  system  of  malting 
are  that  they  can  be  worked  continuously  and  at  any  season  of  the  year,  while  they  occupy 
less  space,  allow  of  efficient  regulation, of  temperature,  economise  labour  and  general 
exp3nses  and  diminish  the  percentage  of  waste. 

(4)  KILNING  OF  MALT.  The  germinated  barley  is  too  moist  to  keep  sound,  and 
as  breweries  require  large  stocks  of  malt  this  must  be  dry  and  capable  of  being  kept.  If 

the  moisture  is  reduced  to  6  per  cent,  by  air  alone  the 
germination  process  is  stopped,  and  on  subsequently 
raising  the  temperature  to  60°  a  slight  diastatic  saccharin- 
cation  occurs,  this  being  greater  in  amount  if  the  moisture 
is  kept  at  12  to  15  per  cent.  ;  beyond  70°  the  diastase  is 
destroyed  and  certain  substances  formed  which  give  good 
flavour,  aroma  and  fullness  of  taste  to  the  beer  and  at  the 
same  time  furnish  food  for  the  yeast.  When  the  tempera- 
ture exceeds  100°  part  of  the  maltose  is  caramelised — for 
the  making  of  dark  beers — and  a  considerable  amount  of 
nitrogenous  substances,  which  would  cause  the  beer  to  keep 
badly,  thrown  out  of  solution. 

In  order  not  to  destroy  too  much  of  the  diastase  and  to 
make  malt  suitable  for  pale  beers  the  drying  must  first  be 
conducted  with  warm  air.  When  the  proportion  of  mois- 
ture has  reached  5  to  6  per  cent,  the  diastase  can  withstand  a 
temperature  of  60°  to  70°  without  losing  much  of  its  activity  ; 
whilst  if  the  malt  is  heated  when  it  contains  too  much 
moisture  (15  to  20  per  cent.)  the  diastase  is  rapidly  destroyed. 
The  drying  is  carried  out  in  a  current  of  warm  air  (or  of  air 
mixed  with  the  hot  gases  from  a  coke  or  anthracite  fire), 
which  passes  through  the  green  malt  placed  in  layers  1 5  to  20 
cm.  deep  on  wire  or  tile  floors,  often  arranged  one  above 
the  other.  Above  the  upper  floor  is  a  chimney,  which 
increases  and  facilitates  the  draught  started  by  suitable 

fans.  The  air  is  heated  by  passing  directly  over  a  fire  or  through  batteries  of  tubes 
heated  in  the  usual  way.  During  the  drying  the  malt  is  turned  by  a  suitable  mechanical 
device,  at  first  every  2  hours  and  later  on  continuously.  The  temperature  of  the  air 
gradually  rises,  during  the  course  of  84  to  90  hours,  by  30°  to  35°  (during  the  first  few 
hours  germination  still  proceeds  feebly,  causing  increase  in  the  diastase),  and  ends  at  100° 
to  110°  (for  dark  beers).  Drying  is  usually  effected  in  less  than  48  hours,  and  it  is  only 
beyond  80°  that  the  diastase  partially  loses  its  saccharifying  properties  (at  90°  it  loses 
50  per  cent,  and  at  100°  85  per  cent.)  ;  this  loss  is,  however,  an  advantage,  since  a  too 
highly  diastatic  malt  leads  to  excessive  saccharification  and  hence  to  increased  attenua- 
tion in  the  subsequent  fermentation,  so  that  the  beer  tastes  less  full.  The  peptases 
also  are  destroyed  beyond  90°,  so  that  the  nitrogenous  substances  are  dissolved  to  a  less 
extent  and  the  beer  hence  keeps  better. 

Fig.  161  shows  diagrammatically  a  section  of  a  two -floor  malt -kiln  in  which  the  air  is 
heated  in  the  tubing,  t,  surrounding  the  ducts  carrying  the  hot  fumes  from  the  coal  burning 
on  the  grate,  F.  The  hot  air  then  traverses  the  malt  on  the  floors,  B  and  C,  and  issues 
from  the  chimney,  D,  the  turning  apparatus,  a,  being  kept  in  motion  meanwhile.  To  obtain 
100  kilos  of  dry  malt  in  24  hours  (maximum  temperature  90°  to  100°)  20  kilos  of  coal  are 
required.  For  making  dark  beers  of  the  Munich  type  part  of  the  kilned  malt  is  further 
roasted  at  about  200°  in  suitable  rotating  iron  cylinders  heated  by  direct  fire  ;  this  treat- 
ment leads  to  the  formation  of  caramel,  which  colours  the  beer,  the  malt  being  then  called 
coloured  malt.  The  temperatures  on  the  malting  floors  and  kiln  are  registered  by  auto- 


FIG.  161. 


MALT    ANALYSIS  167 

matic  devices  which  construct  diagrams  showing  the  temperature  at  any  particular 
moment. 

Nowadays  malt  for  pale  beers  is  sometimes  heated  only  to  25°  to  30°. 

The  kilned  malt  leaves  the  kiln  with  2  to  5  per  cent,  of  moisture  and  is  then  cooled  and 
stored  in  silos  or  large  bins.  A  malt  kept  for  only  1  or  2  months  is  to  be  preferred  to  an 
older  one.1 

1  The  commercial  value  of  a  malt  is  determined  largely  by  its  yield  of  extract,  which  is  measured  as  follows  : 
45  grins,  of  ground  malt  are  placed  in  a  tared  flask  with  200  c.c.  of  water,  the  temperature  being  kept  at  exactly 
45°  for  half  an  hour  and  then  raised  1°  per  minute  up  to  70°,  this  temperature  being  maintained  until  the  liquid 
no  longer  gives  a  blue  colour  with  iodine  ;  the  time  required  at  70°  to  reach  this  point  is  noted  (saccharification 
test).  The  mass  is  then  cooled  and  water  added  to  bring  its  total  weight  up  to  450  grins. ;  after  mixing  and 
filtering  through  a  dry  filter,  the  density  of  the  liquid  is  determined  at  15°  and  by  Windisch's  or  Schulze's  tables 
the  corresponding  quantity  of  extract  deduced.  The  latter  can  also  be  obtained  from  Balling's  tables  (see  below). 
note  being  taken  that  they  yield  low  values,  the  deficit  being  0-08  grm.  per  cent,  for  specific  gravities  up  to  1-01  ; 
0-345  for  specific  gravities  up  to  1-05  ;  0-48  for  specific  gravities  up  to  1-06  ;  and  0-4  for  specific  gravities  up  to 
.  1-08.  If  the  maltose  is  to  be  determined  directly,  10  grms.  of  the  filtered  saccharine  liquid  (corresponding  witli 
1  grm.  malt)  are  diluted  to  100  c.c.,  various  quantities  of  this  liquid  being  then  titrated  with  Fehling's  solution, 
1  c.c.  of  which  corresponds  with  0-0075  grm.  of  maltose. 

C.  Lintner  (1886-1908)  has  modified  the  Kjeldahl  method  for  determining  the  diastatic  power  of  malt  as  follows  : 
25  grms.  of  the  ground  malt  are  extracted  for  6  hours  with  500  c.c.  of  water  at  the  ordinary  temperature,  the 
mixture  then  being  filtered  ;  2  c.c.  (for  pale  malts)  or  8  c.c.  (for  dark  malts)  of  the  filtrate  are  added  to  100  c.c. 
of  2  per  cent,  soluble  starch  solution  and  the  mixture  left  for  exactly  half  an  hour,  at  the  end  of  which  time  10  c.c. 
of  caustic  soda  solution  are  added.  Into  a  number  of  test-tubes,  each  containing  5  c.c.  of  Fehling's  solution, 
are  introduced  varying  quantities  of  the  saccharified  starch  solution  (e.g.  from  1  to  6  c.c.) ;  the  tubes  are  next 
immersed  for  ten  minutes  in  a  boiling  water-bath  and  then  taken  out,  and  the  precipitated  cuprous  oxide  allowed 
to  settle  ;  it  can  then  be  seen  in  which  of  the  tubes  the  Fehling's  solution  is  just  completely  reduced  and  in  which 
it  is  just  not  reduced.  A  more  exact  result  can  be  obtained  by  using  quantities  of  the  saccharified  starch  solution 
intermediate  to  those  corresponding  with  these  two  tubes.  When  0-1  c.c.  of  the  cold  water  malt  extract,  acting 
for  one  hour  on  10  c.c.  of  2  per  cent,  soluble  starch  solution,  forms  just  sufficient  maltose  to  reduce  5  c.c.  of 
Fehling's  solution,  the  malt  is  said  to  have  the  diastatic  power  100  ;  if  0-2  c.c.  of  the  malt  extract  is  required, 
the  diastatic  power  is  taken  as  50,  and  so  on. 

BALLING'S   TABLE 


Degrees 

Degrees 

Degrees 

Degrees 

Balling  or 

Balling  or 

Balling  or 

Balling  or 

Sp.  gr. 

grms.  of 

Sp.  gr. 

grms.  of 

Sp.  gr. 

grms.  of 

Sp.  gr. 

grms.  of 

at  17-5° 

saccharose 

at  17-5° 

saccharose 

at  17-5° 

saccharose 

at  17-5° 

saccharose 

per  100 

per  100 

per  100 

per  100 

grms.  liquid 

grms.  liquid 

grms.  liquid 

grms.  liquid 

1-0010 

0-250 

1-0210 

5-250 

1-0410 

10-142 

1-0610 

14-904 

1-0020 

0-500 

1-0220 

5-500 

1-0420 

10-381 

1-0620 

15-139 

1-0030 

0;750 

1-0230 

5-575 

1-0430 

10-G19 

1-0630 

15-371 

1-0040 

1-000 

1-0240 

6-000 

1-0440 

10-857 

1-0640 

15-604 

1-0050 

1-250 

1-0250 

6-244 

1-0450 

11-095 

1-0650 

15-837 

1-0060 

1-500 

1-0260 

6-488 

1-0460 

11-388 

1-0660 

16-070 

1-0070 

1-750 

1-0270 

6-731 

1-0470 

11-571 

1-0670 

16-302 

1-0080 

2-000 

1-0280 

6-975 

1-0480 

11-809 

1-0680 

16-534 

1-0090 

2-250 

1-0290 

7-219 

1-0490 

12-047 

1-0690 

16-767 

1-0100 

2-500 

1-0300 

7-463 

1-0500 

12-285 

1-0700 

17-000 

1-0110 

2-750 

1-0310 

7-706 

1-0510 

12-523 

1-0710 

17-227 

1-0120 

3-000 

1-0320 

7-950 

1-0520 

12-761 

1-0720 

17-454 

1-0130 

3-250 

1-0330 

8-195 

1-0530 

13-000 

1-0730 

17-681 

1-0140 

3-500 

1-0340 

8-438 

1-0540 

13-238 

1-0740 

17-909 

1-0150 

3-750 

1-0350 

8-681 

1-0550 

13-476 

1-0750 

18-136 

1-0160 

4-000 

1-0360 

8-925 

1-0560 

13-714 

1-0760 

18-363 

1-0170 

4-250 

1-0370 

9-170 

1-0570 

13-952 

1-0770 

18-590 

1-0180 

4-500 

1-0380 

9-413 

1-0580 

14-190 

1-0780 

18-818 

1-0190 

4-750 

1-0390 

9-657 

1-0590 

14-428 

1-0790 

19-045 

1-0200 

5-000 

1-0400 

9-901 

1-0600 

14-666 

1-0800 

19-272 

Correction  of  Degrees  Balling  for  Various  Temperatures 


Determina- 
tion made 
at  tempera- 
ture of 

Correction 
of  degrees 
Balling 

Determina- 
tion made 
at  tempera- 
ture of 

Correction 
of  degrees 
Balling 

Determina- 
tion made 
at  tempera- 
ture of 

Correction 
of  degrees 
Balling 

Determina- 
tion made 
at  tempera- 
ture of 

Correction 
of  degrees 
Balling 

Deg. 

Deg. 

Deg. 

Deg. 

4 

-0-43 

11 

-0-22 

17-5 

— 

24 

+  0-27 

5 

-  0-40 

12 

-  0-19 

18 

+  0-02 

25 

+  0-32 

6 

-  0-37 

13 

-  0-16 

19 

+  0-05 

26 

+  0-37 

7 

-  0-34 

14 

—  0-13 

20 

+  0-09 

27 

+  0-42 

8 

-  0-31 

15 

-0-10 

21 

+  0-13 

28 

+  0-48 

9 

-0-28 

•16 

-0-06 

22 

+  0-17 

29 

+  0-54 

10 

-0-25 

17 

—  0-02 

23 

+  0-22 

30 

+  0-60 

168 


ORGANIC    CHEMISTRY 


Malt  kilned  with  fumes  direct  from  a  coal  fire  communicates  to  the  beer  a  certain 
flavour  from  the  smoke.  Also,  when  coal  is  employed  which  contains  arsenic,  the  latter 
becomes  deposited  on  the  malt  and  hence  finds  its  way  into  the  beer.  Arsenic  may  also 
be  present  in  the  glucose  often  used  in  brewing  ;  in  this  case  it  is  introduced  by  the 
employment  of  arsenical  sulphuric  acid  in  the  manufacture  of  the  glucose  from  starch. 

(5)  CLEANING  AND  GRINDING. 
Before  the  malt  is  mashed  it  is  freed 
from  dust  and  rootlets  by  means  of 
rotating  drums  of  metal  gauze  (a  kind 
of  sieve)  furnished  with  fans.  It  is 
then  ground  but  not  too  finely,  the 
husks  being  kept  whole  as  far  as  pos- 
sible, since  they  serve  in  the  subsequent 
operations  as  filtering  material  ;  if  the 
malt  is  ground  too  fine  it  cannot  be 
exhausted,  as  the  liquid  will  not  drain 
off.  A  suitable  form  of  mill  is  the 
Excelsior  Mill,  made  by  Messrs. 
Krupp  (Figs.  162  and  163).  The  shaft, 
g,  fitted  with  fast  and  loose  pulleys, 
s  and  t,  can  be  shifted  from  right  to 
left  or  vice  versa  through  the  stuffing- 
boxes,  m,  by  means  of  the  lever,  d.  One 
toothed  disc,  a,  is  fixed,  whilst  the 
FIG.  162.  other,  6,  rotates  with  the  axis,  g,  and 

is    so    adjusted    that    the    teeth   pass 

through  the  tooth  spaces  of  the  other  disc.  The  barley  from  the  hopper,  /,  falls  between 
the  two  discs,  where  it  is  ground,  the  ground  malt  (grist)  being  discharged  at  n.  For  the 
sake  of  economy  the  discs  are  toothed  on  both  faces,  so  that  when  one  face  is  worn  the 
other  can  be  used. 

The  total  loss  in  weight  suffered  by  the  barley  during  steeping,  germination,  kilning, 
cleaning,  and  grinding  amounts  to  about  20  per  cent. 

(6)  MASHING.  This  consists  in  subjecting  the  ground  malt  to  the  action  of  warm 
water  so  that  the  diastase  may  act  on 
the  starch  and  convert  it  into  soluble 
products.  The  temperature  at  which  the 
maximum  extract  is  obtained  is  about  65°, 
whilst  at  55°  the  starch  is  only  very 
slightly  attacked  by  diastase,  and  above 
70°  diastase  loses  its  saccharifying  pro- 
perties very  largely  and  the  wort  filters 
through  the  grains  (husks  ;  see  later)  with 
difficulty — this  effect  is  aggravated  by 
coagulation  of  part  of  the  proteins.  The 
quantity  and  quality  of  the  water  have 
an  influence  on  the  mashing,  the  presence 
of  calcium  sulphate  facilitating  the  forma- 
tion of  maltose  and  maltodextrins  and 
increasing  the  amount  of  nitrogenous  substances  dissolved. 
3  hectols.  of  beer  are  made. 

There  are  two  systems  of  mashing  :  the  infusion  method  (at  65°  to  72°),  used  only  in 
top-fermentation  breweries,  and  the  decoction  system,  used  for  bottom-fermentation  and 
sometimes  for  top-fermentation  beers,  and  with  highly  diastatic  malt  or  when  unmalted 
barley  is  used  with  the  malt. 

(I)  The  infusion  process,  used  largely  in  England  and  Scotland,  less  in  France  and 
still  less  in  Germany,  is  usually  carried  out  in  one  of  two  ways  :  (i)  rising  infusion,  where 
the  malt  is  first  mixed  to  a  paste  with  10  per  cent,  of  cold  water  and  then  with  hot  water 
in  the  ratio  of  two  parts  of  water  to  one  part  of  malt,  so  that  a  temperature  of  40°  is 
attained.  To  raise  the  temperature  of  1  kilo  of  malt  (which  has  a  specific  heat  of  about 


FIG.  163. 
From  1  quintal  of  malt  2  to 


MASHING 


169 


0-5)  from  20°  to  40°  requires  10  Calories,  which  can  be  supplied  by  2  litres  of  water  at 
45°,  the  latter  falling  to  40°  on  losing  10  Calories  ;  owing,  however,  to  unavoidable  loss 
of  heat,  water  at  48°  to  50°  should  be  used. 

This  mixing  is  done  in  a  circular  mash-tun  of  metal  or  wood,  furnished  with  a 
perforated  false  bottom  several  centimetres  above  the  true  bottom,  in  which  are  fitted 
the  pipes  supplying  the  hot  water  (Fig.  164).  The  mashing  and  subsequent  mixing  are 
effected  by  efficient  mechanical  stirrers  or  rakes. 

As  soon  as  the  mash  has  reached  the  temperature  of  40°  water  at  80°  is  gradually 
introduced,  the  temperature  being  raised  to  63°  to  65°  in  half  an  hour.  It  is  next  mixed 
for  60  to  70  minutes,  the  liquid  being  then  discharged  by^opening  the  taps  under  the  false 
bottom  so  that  the  liquid  passes  through  the  grains  and  is  conducted  to  the  copper.  The 
residue  in  the  tun  is  mixed  for  15  minutes  with  water  at  75°,  the  liquid  being  run  off  and 
the  grains  finally  washed  with  water  at  80°,  all  these  extracts  passing  to  the  copper.  In 
this  way  almost  complete  saccharification  is  attained  and  the  subsequent  fermentation 
produces  considerable  attenuation.  If 
a  less  attenuation  is  desired,  either 
a  higher  temperature  (72°  to  73°)  is  used 
in  place  of  65°,  or  high-dried  malt  is 
used. 

(ii)  Descending  infusion,  which  is 
rarely  used,  consists  in  bringing  the 
mass  directly  to  a  temperature  of  65°  to 
70°  with  very  hot  water  and  then  allowing 
it  to  fall  slowly  to  35°  to  40°. 

Neither  of  these  methods  admits  of 
the  use  of  rice  or  maize,  the  starch  of 
which  is  attacked  by  diastase  only  after 
it  has  been  heated  with  water  to  80°  to 
85°.  Hence  with  such  material  the 
decoction  process  is  used. 

(II)  Decoction  Process.  This  is 
largely  used  in  North  Germany,  Austria, 
and  Belgium,  and  allows  of  the  use  of  FIG.  164. 

unmalted  barley,  rice,  maize,  wheat,  &c. 

The  malt  grist  is  first  mixed  to  a  paste  with  cold  water  so  as  to  dissolve  the  diastase, 
this  being  carried  out  in  a  metal  vessel  without  a  false  bottom  ;  by  the  addition  of  small 
quantities  of  boiling  water  the  temperature  of  the  mass  is  raised  gradually  to  35°,  From 
one-third  to  one-half  of  the  turbid  wort  (Dickmaische)  is  transferred  to  a  double-bottomed 
copper  heated  with  steam.  In  many  cases  coppers  with  direct-fire  heat  are  used,  these 
being  furnished  with  chains  which  scrape  on  the  bottom  and  so  prevent  caramelisation  of 
the  mass  which  settles  (Fig.  165  shows  a  complete  decoction  or  infusion  plant).  The 
wort  transferred  to  the  copper  is  boiled  for  20  to  40  minutes  and  is  then  returned  to  the 
original  tun,  where  it  raises  the  temperature  to  about  55°.  Another  one-third  or  one-half 
is  similarly  removed,  boiled,  and  returned,  the  temperature  being  thus  raised  to  65°  ;  the 
saccharification  has  then  reached  a  maximum  and  the  mash  become  thinner.  The 
complete  disappearance  of  starch  is  controlled  by  the  reaction  with  iodine.  About 
one-half  of  the  wort  is  again  removed,  boiled,  and  returned,  the  temperature  being  thus 
raised  to  75°.  During  all  these  operations  continual  stirring  is  maintained.  The  greater 
the  number  of  decoctions  made  the  greater  will  be  the  density  of  the  wort  and  the  darker 
the  beer.  The  turbid  wort  is  either  allowed  to  deposit  in  tuns  with  false  bottoms  as 
shown  in  Fig.  164,  or  passed  through  filter-presses  (see  Sugar  Industry)  to  clarify  it,  the 
grains  remaining  in  the  form  of  cakes  being  well  washed.1 

When  considerable  quantities  of    other    cereals    are    to    be  used  with  the  malt  use 

1  The  grains  are  composed  of  the  whole  of  the  husks  of  the '  malt — coagulated  proteins,  pentosans,  fat, 
maltose  and  dextrin.  They  serve  as  excellent  cattle-food,  but  if  not  consumed  in  the  course  of  24  hours,  they 
undergo  change  ;  they  may,  however,  be  placed  in  silos  and  dried  in  a  suitable  apparatus  (see  Tig.  149,  p.  154). 
Wet  grains  contain  70  to  80  per  cent,  of  water,  4  to  6  per  cent,  of  protein,  1  to  3  per  cent,  of  fat,  8  to  14  per  cent, 
of  extractive  substances,  1  to  3  per  cent,  of  ash,  and  3  to  9  per  cent,  of  cellulose.  Dried  grains  contain  6  to 
18  per  cent,  of  water,  17  to  26  per  cent,  of  protein,  4  to  9  per  cent,  of  fat,  35  to  55  per  cent,  of  extractive 
substances,  3  to  12  per  cent,  of  ash,  and  9  to  20  per  cent,  of  cellulose  ;  they  have  a  brown  colour,  a  pleasing 
odour  of  new  bread  and  a  sweet  taste  ;  they  make  a  good  food  to  follow  wheat  or  oat  bran. 


170 


ORGANIC    CHEMISTRY 


is  made  of  a  Henze  pressure  apparatus,  as  described  under  Distilling  (Fig.  104, 
p.  119). 

The  wort  thus  obtained  is  boiled  with  a  certain  quantity  of  hops  until  a  certain  amount 
of  concentration  has  been  effected.  This  boiling  finally  destroys  the  diastase,  intensifies 
the  colour  of  the  wort  and  aerates  it,  and  oxidises  various  substances  producing  acid 
bodies  ;  it  completely  sterilises  the  liquid,  which  is  also  clarified  owing  to  the  precipitation 
of  nitrogenous  substances,  partly  by  the  tannin  of  the  hops. 

The  decoction  of  the  hops  is  carried  out  in  a  separate  vessel,  the  boiling  liquid  being 
continually  circulated  until  the  hops  are  exhausted.  The  decoction  is  then  added  to  the 
boiling  wort,  principally  towards  the  end  of  the  operation  ;  if  added  earlier  the  hop 
extract  loses  some  of  its  aroma.  The  direct  addition  of  the  hops  to  the  copper  is  still 
used,  although  the  method  is  not  a  very  rational  one  ;  it  is  better  to  pass  the  boiling 
wort  from  time  to  time  into  a  separate  vessel  containing  the  hops  and  then  back  to  the 
copper,  this  procedure  being  repeated  until  the  hops  are  exhausted. 


FIG.  165. 

In  general,  400  to  500  grms.  of  hops  are  used  per  hectolitre  of  beer,  or  2-5  to  5  kilos  for 
every  quintal  of  malt  mashed.  More  hops  are  usually  employed  for  beers  to  be  kept  for 
some  time  (lager  beer,  stock  ale)  than  for  draught  beer.  The  lupulin  powder  contained  in 
the  hop  gives  up  resins  and  essential  oils,  while  the  leaves  give  tannin  and  the  stalks 
somewhat  bitter  substances  ;  the  whole  gives  the  bitter  taste  and  aroma  of  the  beer,  and 
causes  the  latter  to  keep  better.  A  temperature  of  75°  (Pasteur)  is  sufficient  to  sterilise 
a  hopped  beer,  since  the  resins  have  a  marked  antiseptic  action. 

The  boiling  of  the  wort  is  carried  out  in  copper  vessels  (see  Fig.  165,  a)  heated  by  direct 
fire  or  by  indirect  steam  (passed  through  coils  or  through  the  double  bottom  of  the  copper), 
the  boiling  being  continued  for  4  to  6  hours  with  dilute  worts  (infusion)  and  only  1^  to  2  hours 
with  the  more  concentrated  decoction  worts  ;  as  a  rule  boiling  is  continued  until  the 
density  reaches  a  certain  value  for  the  particular  kind  of  beer  to  be  made  (see  later).  The 
temperature  during  boiling  should  be  gradually  raised  and  registered.  In  many  modern 
breweries  there  are  automatic  registering  thermometers  which  show  the  whole  course  of 
these  operations.  When  the  boiling  is  finished  the  wort  is  allowed  to  stand  for  a  time, 
and  the  Inland  Revenue  officials  then  generally  make  their  first  measurements  (they 
calculate  that  1  kilo  of  dry  malt  should  give  25  litres  of  wort  with  a  density  of  1°  Balling, 
5  litres  at  5°,  &c.,  an  allowance  being  made  of  10  per  cent.).  The  copper  is  then  dis- 
charged, the  hops  being  strained  off,  and  the  wort  pumped  to  the  cooler,  which  is  usually 
at  the  top  of  the  building.  These  coolers  are  large  shallow  vessels  of  iron  (or  copper  or 
wood)  in  whicfy  the  coagulated  proteins  are  deposited  ;  the  temperature  here  is  not  allowed 


COOLING    OF    WORT 


171 


to  fall  below  60°  to  65°,  otherwise  contamination  with  harmful  organisms  (butyric,  lactic, 
&c.)  might  occur.  In  Italy  the  tax  on  the  manufacture  of  beer  is  calculated  from  the 
volume,  temperature,  and  specific  gravity  of  the  wort  in  the  cooler  (see  later).  The  wort 
is  next  cooled  rapidly  by  suitable  refrigerators  to  2°  to  3°  (for  bottom  fermentation)  or 
12°  to  15°  (for  top  fermentation).  One  form  of  refrigerator  which  is  much  used  consists  of 
a  number  of  superposed,  communicating  horizontal  tubes  (Fig.  166).  In  the  tubes  of 
the  upper  half  water  circulates,  and  in  those  of  the  second  half  brine  at  a  temperature 
of  -6°  or  -8°  from  a  refrigerating  machine  (see  vol.  i,  p.  231).  The  wort  flows  down  in 
a  thin  skin  over  the  outside  of  the  tubes,  meanwhile  dissolving  an  appreciable  quantity 
of  air.  The  cooled  and  aerated  wort  flows  down  to  the  fermenting  vessels  placed  in  cool 
rooms  ;  for  bottom  fermentation  these  are  cooled  to  about  0°  by  pipes  conveying  cold 
brine.  The  wort  from  the  coolers  is  turbid  and  should  be  filtered  through  conical  cloth 
bags  or  filter -presses.  In  some  modern  breweries  the  coolers  are  omitted  in  order  to 
avoid  any  possible  contamination  (which  is,  however,  difficult  with  hopped  wort  at  60°) 
and  the  wort  is  passed  direct  from  the  copper  to  the  closed  refrigerator  and  the  filter- 
press,  aeration  being  afterwards  effected  with  air  filtered  through  cotton -wool. 

The  refrigerators  consume  considerable 
quantities  of  water,  and  where  this  is 
scarce  the  warm  water  from  the  refrigera- 
tors is  cooled  by  means  of  pulverisers 
or  by  causing  it  to  flow  down  over 
twigs,  the  evaporation  thus  caused  often 
lowering  the  temperature  below  that  of 
the  air  (see  section  on  Sugar).  The  boil- 
ing of  the  wort  has  hence  effected  a  con- 
centration, the  preparation  of  a  sterile 
(aseptic)  liquid,  and  the  extraction  of  the 
useful  principle  of  the  hop,  the  tannin  of 
which  has  partially  precipitated  the  pro- 
teins. If  pale  beer  is  to  be  brewed  the 
wort  can,  if  necessary,  be  clarified  during 
the  boiling  by  the  addition  of  a  little 
tannin.  During  the  cooling  on  the  cooleis 
the  wort  takes  up  the  oxygen  necessary 
for  the  oxidation  of  the  resins,  for  clarify-  pIG  ^gg 

ing  it  and,  more  especially,  for  aiding  the 
development  and  multiplication  of  the  yeast  during  the  initial  stages  of  the  fermentation 

Contact  of  the  wort  with  tin,  e.g.  tinned  vessels,  is  avoided,  as  turbidity  of  the  beer 
may  be  caused  thereby,  especially  if  the  wort  is  acid  or  rich  in  carbon  dioxide. 

FERMENTATION.  From  the  density  (degrees  Balling)  or  the  dry 
extract  of  the  wort,  the  extract  yielded  by  the  materials  may  be  deduced,  and, 
under  favourable  conditions,  the  dry  extract  amounts  to  about  70  per  cent, 
of  the  weight  of  the  malt,  whilst  with  bad  working  it  may  be  as  low  as  45  per 
cent.  When  ready  for  fermentation  the  wort  contains  mainly  maltose,  malto- 
dextrins,  dextrins,  a  little  saccharose,  glucose,  and  levulose,  besides  nitro- 
genous substances  partially  peptonised  and  transformed  into  amino-acids  ; 
also  lactic  acid  and  potassium  phosphates.  Fermentation  with  yeast  converts 
the  carbohydrates  more  or  less  completely  into  alcohol  and  carbon  dioxide.1 

1  In  addition  to  what  has  been  said  on  pp.  Ill  and  123  on  ferments  and  yeasts  in  general,  the  following  i& 
of  interest,  especially  to  the  brewing  industry : 

All  yeasts  which  attack  only  saccharose,  maltose,  glucose,  and  levulose,  giving  alcohol  and  carbon  dioxide, 
are  feebly  attenuating  yeasts  of  the  so-called  Saaz  type  (e.g.  the  beer-yeasts  of  Li6ge, which  yield  fairly  full-tasting 
sweet  beers  containing  little  alcohol).  Other  yeasts  are  also  capable  of  fermenting  the  combined  maltose  of 
maltodextrins  by  means  of  a  special  enzyme  studied  by  Delbriick,  maltodextrinase  ;  these  yeasts  give  the  maximum 
attenuation  and  form  the  so-called  Frohberg  type,  producing  alcoholic,  highly  attenuated  beers  even  from  weak 
worts.  Between  these  types — Saaz  and  Frohberg — there  exist  intermediate  ones  giving  in  4  days  at  25°  to  27°, 
well-defined  attenuations  in  a  normal  wort. 

Certain  other  yeasts  are  capable  of  fermenting  dextrin  combined  as  maltodextrins,  since  they  contain  an 
enzyme  which  Delbriick  has  termed  dextrinase.  Such  is  the  Schizosaceharomycet  Pombi:,  separated  from  the 
millet  beer  of  the  Egyptians.  These  yeasts  constitute  the  so-called  Logos  type.  Wild  yeasts  are  all  strongly 
attenuating  and  may  produce  turbidity  in  finished,  slightly  fermented  beers,  which  they  referment.  The  yeasts 


172  ORGANIC    CHEMISTRY 

The  concentration  of  the  wort  most  favourable  to  the  multiplication  of 
yeast  is  15°  Balling  (corresponding  with  a  specific  gravity  of  1-06).1  A  too 
dilute  wort  or  one  prepared  with  an  excessive  proportion  of  non-germinated 
grain  has  not  sufficient  assimilable  nitrogenous  food  (amino-acids),  and  this 
is  remedied^  by  the  addition  of  zymogen,  which  is  a  commercial  product. 
During  the  period  when  the  yeast  develops  (first  stage  of  the  fermentation) 
little  alcohol  and  much  carbon  dioxide  are  produced. 

Two  distinct  methods  of  fermentation  are  in  use  :  top  fermentation,  used 
generally  in  England,  Belgium,  and  Holland,  and  largely  in  France,  and  also, 
at  one  time,  exclusively  in  Italy  ;  and  bottom  fermentation,  usually  employed 
in  Germany,  Austria,  and  Denmark,  and  in  general  use  in  countries  where 
beers  of  the  Munich  and  Pilsen  types  are  made.  In  hot  countries  it  is  easier 
to  regulate  bottom  fermentation  (by  refrigeration)  than  top  fermentation, 
since  in  summer  the  temperature  of  the  air  is  often  high  enough  to  have  an 
injurious  effect  on  top  fermentation.  So  that,  as  a  refrigerating  plant  is 
necessary,  the  bottom  fermentation  system  is  preferable. 

The  difference  between  bottom  and  top  yeasts  is  that  the  latter  are  covered 
with  viscous,  mucilaginous  substances  and  readily  stick  together  and  carry 
bubbles  of  carbon  dioxide  developed  in  the  wort  to  the  surface  and  so  produce 
a  rapid  feimentation  ;  the  former,  however,  fall  to  the  bottom  of  the  fer- 
menting vessel  and,  even  under  the  microscope,  are  not  found  in  large  masses. 
Top  yeasts  develop  well  only  at  temperatures  above  12° — best  at  about 
24° — and  effect  complete  fermentation  in  4  to  6  days,  whilst  the  bottom 
yeasts  develop  below  10°  and,  after  the  vigorous  primary  fermentation  of 
8  to  12  days  at  6°  to  8°,  continue  the  maturation  of  the  beer  for  two  or 
three  months  by  a  secondary  fermentation  at  a  low  temperature  (0°  to  2°)  ; 
this  procedure  gives  beers  of  less  attenuation  which  can  be  produced  or  con- 
sumed even  in  summer  (lager  beer).  Top -fermentation  beers  are  almost 
always  more  highly  attenuated,  are  consumed  at  once  (draught  beer),  and  are 
made  more  especially  in  the  cold  weather ;  they  can,  however,  be  kept,  and 
in  some  cases  stock  beers  are  made  on  this  system. 

The  advantages  and  disadvantages  of  the  two  processes  are  as  follow  : 

Top  fermentation  does  not  require  costly  refrigerating  plant,  and  hence  lends  itself 
to  the  construction  of  small  breweries  ;  further,  the  beer  can  be  sold  immediately,  and 
the  capital,  although  small,  thus  frequently  renewed  each  year.  The  control  and  successful 
working  of  top  fermentation  are,  however,  more  difficult  owing  to  ready  contamination 
with  numerous  harmful  bacteria  which  find  at  15°  to  20°  the  most  favourable  conditions  for 
their  development,  especially  in  the  summer  ;  in  bottom-fermentation  beers  only  yeasts 
can  develop  at  0°  to  2°. 

With  top  fermentation,  in  which  at  first  yeasts  of  the  Saaz  type  and  those  intermediate 
to  the  Saaz  and  Frohberg  types  predominate,  there  develop  later  bacteria  and  also 
Frohberg  yeasts  (especially  during  the  secondary  fermentation),  and  both  of  these  render 
difficult  the  preparation  of  a  clear  beer  which  does  not  become  turbid  after  fermentation  ; 
on  the  other  hand,  a  bright  beer  is  easily  and  naturally  obtained  by  bottom  fermentation. 
In  summer,  then,  unless  an  abundant  supply  of  cold  water  and  also  cool  cellars  are  avail- 
intermediate  to  the  Saaz  and  Frohberg  types  and  also  Frohberg  yeasts  themselves  are  especially  active  in  the 
secondary  fermentation ;  they  increase  the  apparent  fullness  of  the  beer,  even  when  this  is  light,  arid  maintain 
a  continuous  and  desirable  evolution  of  carbon  dioxide  by  slowly  fermenting  the  maltodextrius  and  even  dextrins. 
In  order  to  grow  and  multiply,  yeasts  generally  require,  in  addition  to  carbohydrates  and  free  oxygen,  nitro- 
genous substances,  but  they  cannot  make  use  of  nitrates,  or  ammonium  salts,  or  even  the  true  proteins ;  they 
can,  however,  utilise  the  decomposition  products  of  the  latter,  namely,  the  amino-acids  (such  as  asparagine)  pro- 
duced by  the  proteolytic  enzymes  secreted  by  healthy  yeasts.  They-.require  also  mineral  substances,  e.g.  calcium 
and  potassium  phosphates. 

The  oxygen  of  the  air  is,  as  has  been  said,  indispensable  to  the  development  and  multiplication  of  yeast,  and 
well-aerated  worts  facilitate  the  multiplication  during  the  first  few  days,  when  only  CO.  and  H,O  are  produced 
when,  however,  the  supply  of  free  oxygen  diminishes  or  ceases,  the  yeast  produces  more  especially  alcohol  and 
carbon  dioxide.     There  are  also  saccharomyces  which  are  solely  aerobic  and  form  membranes  on  the  surface  of 
the  wort,  producing  only  carbon  dioxide  and  water  and  destroying  the  alcohol  produced  by  other  yeasts. 

1  The  strengths  of  the  worts  for  different  types  of  beer  are  :  9°  to  10°  Balling  for  light  beers  ;  12°  to  13°  for 
draught  beers  (Schenkbier) ;  15°  to  20°  for  double  beers  (Bock  or  Salvator  beer) ;  and  up  to  25°  for  table  beers. 


FERMENTATION 


173 


able,  and  rigorous  precautions  and  disinfection  are  resorted  to,  it  is  very  difficult  to 
prepare  top-fermentation  beer,  whilst  the  low  temperature  required  for  bottom  fer- 
mentation can  be  attained  at  any  season  of  the  year  by  refrigerating  plant.  Bottom 
fermentation  gives  beers  of  a  more  constant  type,  since  the  mother -yeast  from  succes- 
sive fermentations  does  not  become  contaminated  so  easily  as,  and  hence  requires  renewal 
less  frequently  than,  with  top  fermentation.1 

When  a  large  amount  of  yeast  is  added  to  a  wort  the  fermentation  is  initiated  and 
completed  more  rapidly  ;  with  small  quantities  the  same  result  is  obtained,  but  after  a 
longer  time,  so  that  there  is  more  danger  of  contamination.  Usually  250  to  300  grms. 
of  pressed  yeast  are  used  per  hectolitre  of  wort — rather  more  for  strong  worts. 

Especially  with  top,  but  also  with  bottom  fermentation,  it  is  most  important  that  all 
instruments,  vessels,  and  rooms  should  be  kept  clean  and  disinfected.  For  this  purpose 
boiling  water  is  used  and  also  dilute  solutions  of  hydrofluoric  acid,  ammonium  fluoride, 
ammonium  fluosilicate,  calcium  bisul- 
phite, and  calcium  hypochlorite.  In 
all  cases,  however,  great  care  must  be 
taken  to  remove  the  disinfectant  com- 
pletely with  abundant  supplies  of  hot 
water,  in  order  that  the  yeast  may  not 
be  injured.  Chloride  of  lime  is  elimi- 
nated by  rinsing  first  with  bisulphite 
solution  and  then  with  hot  water. 
Even  traces  of  bisulphite  (sometimes 
added  during  mashing  to  prevent  the 
action  of  lactic  ferments)  must  be 
completely  eliminated,  otherwise, 
during  the  alcoholic  fermentation, 
which  is  a  process  of  reduction,  they 
may  yield  hydrogen  sulphide  and  so 
give  a  bad  taste  and  odour  to  the 
beer.  (Bacteria  capable  of  producing 
hydrogen  sulphide  sometimes  develop 
in  beer.) 

Whatever  system  of  fermentation  is 
used,  it  is  always  divided  into  two 
phases  :  the  primary  or  vigorous,  and 
the  secondary.  The  primary  fermenta-  FIG.  167. 

tion    begins    12    or    24    hours     after 

pitching,  when  the  yeast  has  grown  to  some  extent  at  the  expense  of  the  dissolved 
oxygen,  and  continues  for  3  or  4  days  in  the  case  of  top  fermentation  or  for  10  to  12 
days  with  bottom  fermentation  ;  considerable  quantities  of  carbon  dioxide  are  developed, 
these  forming  a  dense,  white,  frothy  head  on  which  can  be  seen  brownish  spots  of  hop 
resin  or  agglutinated  bacteria.  In  top  fermentation,  this  first  head  is  removed,  the  next 
darker  one  being  collected  for  pitching  purposes. 

In  the  bottom  fermentation  system  and  in  large  modern  breweries  in  general,  in  order 
that  the  yeast  may  be  kept  as  pure  as  possible,  the  pitching  is  carried  out  in  the  manner 
described  on  p.  127  for  distilleries. 

1  With  top  fermentation,  the  type  and  taste  of  the  beer  are  determined  by  the  united  activity  of  a  number 
of  different  yeasts  and  bacteria  which  are  present  in  given  equilibrated  proportions,  these  becoming  modified 
as  contamination  increases.  When  the  yeast  is  renewed,  the  pure  yeast  naturally  gives  a  different  taste  to  the 
beer,  and  this  inconvenience  cannot  be  avoided  by  preparing  a  mixture  of  yeasts  and  bacteria  similar  to  that 
normally  present  in  the  partially  contaminated  top  fermentation.  New  pure  yeasts  are  less  resistant  to  con- 
taminating surroundings  than  old  ones  are. 

Attempts  are  made  to-day  to  keep  the  fermentation  pure  as  long  as  possible  by  the  use  of  good,  hops,  the 
resins  of  which  exert  an  agglutinating  and  paralysing  action  on  the  bacteria,  so  that  these  can  be  removed  from 
the  tun  with  the  first  scum  forming  on  the  surface  of  the  fermenting  wort ;  the  purer  yeast  of  succeeding  heads 
is  then  collected  for  pitching  subsequent  worts.  When  the  collection  of  the  yeast  is  delayed,  that  of  the  Frohberg 
type  increases.  With  the  object  of  maintaining  the  cultures  naturally  pure  and  constant,  Effront  has  proposed 
the  addition  of  abietinic  acid — a  component  of  lupulin  and  of  colophony — to  agglutinate  and  render  innocuous 
the  bacteria  in  fermenting  worts  (see  also  p.  141).  Thus,  after  elimination  of  the  bacteria  with  the  first  scums, 
purer  yeast  can  be  collected  and  washed  with  pure  water  or,  better,  with  water  containing  a  little  hydrofluoric 
acid  or  ammonium  fluoride  (5  to  10  grms.  per  hectolitre),  which  attacks  the  bacteria,  but  not  the  yeast.  It  cannot, 
however,  be^denied  that,  in  general,  washing  produces  considerable  weakening  of  yeast,  which  can  be  reinvigorated 
by  preliminaryjgrowth  in  sterilised,  unhopped  wort. 


174  ORGANIC    CHEMISTRY 

During  the  primary  fermentation,  a  considerable  quantity  of  heat  is  evolved,  and  to 
prevent  the  temperature  exceeding  22°  to  25°  in  top  or  7°  to  8°  in  bottom  fermentation, 
attemperating  coils,,  through  which  cold  water  (top)  or  brine  (bottom)  passes,  are  used  to 
cool  the  fermenting  wort  (F,  Fig.  167).  Each  fermenting  vat  is  provided  with  a  slate, 
&c.,  on  which  are  noted,  each  day,  the  temperature  and  the  specific  gravity  of  the  wort  ; 
the  attenuation  should  reach  58  to  62  per  cent,  in  the  primary  fermentation  and  70  to 
75  per  cent,  in  the  secondary  fermentation,  in  order  that  the  beers  may  keep  in  the  warmer 
rooms  of  the  consumers.1  When  the  vigorous  fermentation  is  ended,  the  head  falls  and 
almost  disappears,  carrying  to  the  bottom  of  the  wort  the  suspended  yeast  ;  in  this  way 
the  secondary  fermentation  is  started,  this  being  allowed  to  proceed  for  15  to  20  days 
in  the  trade  casks  placed  in  cellars  at  10°  to  12°  (for  top  fermentation)  ;  the  beer  is  then 
cleared,  filtered,  and  sold.  In  bottom  fermentation,  on  the  other  hand,  the  secondary 
fermentation  is  completed  in  large  tuns  pitched  inside  (-see  later)  ;  these  are  not  quite  filled 
and  are  kept  for  1  to  3  months  in  cellars  maintained  continually  at  0°  to  2°,  where  the 
beer  acquires  the  desired  attentuation  and  its  characteristic  flavour.  The  yeast  which  is 
deposited  in  the  fermenting  vessels  can  be  collected,  pressed  (p.  125)  and  sold  to  bakers  or 
small  brewers. 

In  some  breweries  the  carbon  dioxide  is  now  drawn  off  from  the  fermenting  vats,  which 
are  fitted  with  covers,  by  pumps  and,  after  being  passed  through  potassium  permanganate 
solution  to  purify  it,  the  gas  is  then  liquefied  (see  vol.  i,  p.  382)  ;  it  can  be  either  utilised 
in  the  brewery  itself  or  sold. 

The  fermenting  vessels  and  the  storage  casks  are  constructed  of  oak  or  pitch-pine. 
The  use  of  glass  vats  has  been  proposed,  as  these  retain  the  pure  flavour  of  the  beer  ;  such 
a  vat  to  hold  42  hectols.  costs  about  £40.  The  cellars  have  walls  and  floor  of  concrete 
(1  metre  higher  than  the  first  aqueous  border  of  the  subsoil)  so  that  they  can  be  washed 
when  necessary  ;  the  roof  is  of  brickwork.  These  cellars  are  furnished  with  draughts 
to  remove  the  carbon  dioxide,  with  double  doors  (always  on  the  north  side)  to  prevent  the 

1  Determinatiort  of  the  Attenuation  and  of  the  Apparent  and  Real  Extracts  of  Beer.  The  apparent 
extract  is  deduced  from  the  density  of  the  well-shaken  (to  remove  CO2)  beer  and  the  corresponding  number 
of  degrees  Balling  (see  p.  167).  The  real  extract  is  deduced  from  the  specific  gravity  (and  Balling's  tables)  of  the 
beer  freed  from  alcohol  by  evaporating  it  to  one-third  of  its  volume  and  making  the  residue  up  to  the  original 
volume.  The  original  extract  of  the  wort  may  he  calculated  with  moderate  accuracy  by  adding  to  the  real  extract 
the  amount  of  alcohol  (determined  as  in  wine,  p.  147)  multiplied  by  1-92. 

The  degree  of  real  attenuation  (A)  is  referred  to  1  hectolitre  of  wort  and  indicates  how  many  parts  per  100  of 
the  extract  of  the  wort  are  transformed  into  alcohol  and  carbon  dioxide  :  it  is  obtained  by  means  of  the  following 
formula  : 

A  =  ^^  X  100 

where  D  represents  the  percentage  of  extract  in  the  wort  and  d  the  percentage  of  real  e.rtract  of  the  beer. 

In  practice,  the  percentage  of  extract  is  sometimes  replaced  by  the  degrees  Balling,  but  the  results  thus  obtained 
are  not  very  exact.  If  we  make  D  =  15°  Balling  and  d  =  5°,  the  real  attenuation  becomes  : 

15-5 
A  =  ——•  x  100  •=  66-66  per  cent. 

15 

But  it  cannot  be  denied  that  Balling  degrees  refer  to  kilos  of  sugar  or  of  extract  in  100  kilos  of  solution,  so 
that  a  wort  showing  15°  Balling  (sp.  gr.  1-0615)  contains  15  kilos  of  extract  per  100  kilos  of  wort,  or  15-922  kilos 
(i.e.  15  X  1-0615)  in  a  hectolitre  of  wort  ;  the  beer,  free  from  alcohol,  showing  5°  Balling,  has  a  sp.  gr.  1-020,  and 
1  hectolitre  contains  5-100  kilos  of  extract,  so  that  10-822  kilos  of  extract  have  been  fermented  and  the  true 

10-822 
attenuation  is  TcTooo  x  ^  ~  ®^'*  ™" 


Practical  brewers  find  it  more  convenient,  in  considering  the  degree  of  attenuation  of  a  wort,  to  calculate  the 

D-d 
degree  of  apparent  attenuation  (A')  from  the  apparent  extract  of  the  beer  d  bymeans  of  the  formula,  A  =  —  —  —  x  100; 

for  example,  a  wort  of  16°  Balling  has  the  sp.  gr.  1-0658  and  1  hectolitre  contains  17-05  kilos  of  extract,  while 
the  beer,  with  7°  Balling  of  apparent  extract,  has  the  sp.  gr.  1-0281,  corresponding  with  7-20  kilos  of  extract  per 

17.05  _  7-20 
hectolitre.     The  apparent  attenuation  is  hence  -  -r-rr  -  X  100  =  57-9  per  cent,  per  hectolitre. 

L  i  *Ui> 

The  attenuation  can  be  deduced  in  a  rather  less  exact  manner  if  instead  of  degrees  Balling  are  used  degrees  of 
the  legal  densimeter  (i.e.  the  figures  in  the  second  decimal  place  of  the  specific  gravity,  a  value  of  1-063  for  the 
latter  thus  corresponding  with  6-3°  on  the  legal  densimeter).  In  the  above  example,  16°  Balling  corresponds  with 
sp.  gr.  1-0658,  hence  with  6-58°  on  the  densimeter  ;  similarly,  7°  Balliog  corresponds  with  2-81  densimeter  degrees. 
Hence  the  apparent  attenuation  is  given  by  : 

A'  =  —  -  —  -  X  100  =  57-3  per  cent. 
6-58 

which  differs  little  from  the  value  calculated  above  from  the  degrees  Balling,  and  is  sufficiently  exact  for  practical 
purposes.  Hence,  both  for  real  and  apparent  attenuation,  Balling's  tables  can  be  dispensed  with,  it  being  sufficient 
to  determine  the  specific  gravity.  It  should  be  noted  that  the  lesjal  density  expresses  the  weight  of  wort 
contained  in  the  volume  occupied  hy  1  kilo  of  water  measured  »t  17-5°, 


NATHAN-BOLZE    PROCESS 


175 


entry  of  warm  air  from  outside  and  with  electric  lighting  so  that  windows,  which  dissipate 
the  cold  may  be  avoided.  The  vats  and  casks  are  raised  50  to  60  cm.  from  the  ground  and 
are  inclined  slightly  forward  so  that  they  can  be  emptied  completely  and  easily  cleaned 
from  outside.  Along  the  ceiling  run  pipes  for  the  circulation  of  cold  brine  (bottom 
fermentation),  which  maintain  a  temperature  below  60°  in  the  fermentation  cellars 
and  one  of  0°  to  2°  in  the  lager  cellars. 

Ten  or  fifteen  days  before  the  beer  is  run  off  from  the  lager  vessels — which  have  been 
several  times  filled  up  to  avoid  contact  of  the  beer  with  the  air  and  consequent  danger 
from  acetic  ferments  —  the 
bung-hole  is  tightly  closed  so 
as  to  supersaturate  the  beer 
under  slight  pressure  with 
carbon  dioxide,  which  is  still 
developed  more  or  less  feebly 
according  to  the  state  of  ma- 
turity of  the  beer.  If  a  beer 
contains,  say,  O'l  to  0-2  per 
cent,  of  C02  before  the  bung- 
hole  is  closed,  it  will  sub- 
sequently contain  six  or  seven 
times  that  proportion. 

Nathan-Bolze  Rapid 
Process  (Ger.  Pat.  135,539, 
1900).  This  process  was  tested 
on  an  industrial  scale  in  1904 
in  the  Fermentation  Institute 
at  Berlin,  and  gave  satisfac- 
tory results.  But  the  applica- 
tion of  the  process  has  not 
progressed  as  rapidly  as  was 
hoped  for  a  process  which 
allows  of  mature  beer  being 
prepared  in  8  or  10  days,  and 
works  under  conditions  of 
sterilisation  formerly  attain- 
able only  in  the  laboratory  or 
in  the  manufacture  of  spirit 
by  the  amylo -process  (p.  129). 
The  hot,  sterile  wort  from  the 
copper  passes  into  a  large 
hermetically  sealed,  sterile 
vessel  of  enamelled  iron  (a 
special  resistant  enamel  being 
employed)  surrounded  by  an  FIG>  igg. 

iron     jacket     through    which 

water  can  be  passed.  These  vessels  have  a  capacity  of  125  hectols.  or  more  and  are 
called  Hansena  vessels.  They  are  provided  with  powerful  stirrers  (Fig.  168),  which  keep 
the  wort  in  continual  motion  during  the  fermentation  and  thus  accelerate  the  transforma- 
tion of  the  maltose  into  alcohol  and  carbon  dioxide. 

After  the  temperature  of  the  wort  has  been  lowered  to  50°  by  passing  water  through 
the  jacket  and  the  diminution  of  pressure  (owing  to  the  condensation  of  steam)  compen 
sated  by  the  admission  of  sterilised  air,  the  latter  (which  has  served  also  to  aerate  th 
wort)  is  replaced  by  carbon  dioxide,  the  cooling  being  continued  to  10°.     The  pure  yeast 
is  then  introduced  through  suitable  pipes,  the  mass  being  slightly  stirred  at  intervals 
of  an  hour.     The  gas  developed  is  removed  in  order  to  hasten  the  fermentation,  and  is 
washed  with  permanganate,  part  of  it  then  being  compressed  (see  p.  174).     The  carbon 
dioxide  which  is  not  compressed  is  utilised  to  remove  the  new  beer  flavour  from  beer 
already  fermented  in  the  Hansena  vessels  ;  the  gas  is  passed  in  at  the  bottom  (after  removal 
of  the  yeast  sediment)  at  the  ordinary  temperature,  the  mass  being  continually  stirred 


176  ORGANIC    CHEMISTRY 

meanwhile,  it  being  the  carbon  dioxide  which  effects  the  elimination  from  the  boor  of  the 
volatile  products  to  which  the  disagreeable  taste  and  odour  of  new  beer  are  due.  The 
gas  issues  from  the  top  of  the  vessel,  passes  to  the  purifiers  and  is  again  conducted  through 
the  beer,  this  process  being  continued  for  10  hours  on  end.  The  primary  fermentation 
is  finished  in  less  than  3  days,  and,  after  the  passage  of  gas  through  the  beer  is  completed, 
the  temperature  is  lowered  to  0°  and  the  beer  saturated  for  24  hours  with  slightly  com- 
pressed carbon  dioxide.  The  beer  is  finally  filtered  and  delivered  to  the  trade  casks, 
where  it  keeps  well  even  in  the  hot  weather. 

Such  a  process,  simple,  rapid,  and  economical  (the  cost  of  the  beer  being  diminished 
by  about  2s  6d.  per  hectolitre),  although  it  does  not  give  a  very  delicate  flavoured  beer, 
should  be  suitable  to  hot  countries  and  to  small  breweries.  Several  European  breweries 
already  work  on  these  lines  and  recently  (1907)  one  has  been  constructed  at  Milan  to  employ 
a  modification  of  the  Nathan  patent,  consisting  of  a  system  intermediate  to  the  old  process 
with  open  fermenting  vessels  and  that  devised  by  Nathan  ;  in  this  case  enamel]  ed  iron 
vessels  are  used  both  for  the  primary  fermentation  and  for  the  maturation  (3  to  4  weeks). 
These  vessels  cost  about  £1  for  each  hectolitre  of  capacity. 

If  to  the  Nathan  process  is  added  the  Meura  system  of  mashing  (1891) — which  has 
rendered  the  preparation  of  the  wort  as  simple  as  possible  by  mashing  the  finely  ground 
malt  in  a  horizontal  cylinder  fitted  with  stirrers  so  that  the  mash  can  be  rapidly  cooled  or 
heated  and  wort  ready  for  passing  to  the  filter-press  and  thence  to  the  copper  can  be 

obtained  in  an  hour — it  will  be  understood 
how  the  manufacture  of  ordinary  beer  has 
been  shorn  of  those  practical  and  theoretical 
difficulties  long  regarded  as  insurmount- 
able. 

RACKING  OF  BEER.  Beer  is  delivered 
to  the  consumer  in  bottles  and  in  casks,  and 
should  be  perfectly  bright,  cold,  and  super- 
saturated with  carbon  dioxide.  To  render  it 
bright,  the  old  method  of  clarification  with 
gelatine  or  of  filtration  through  bags  has  now 
FIG.  169.  been  largely  replaced  by  the  use  of  the  filter- 

press,  which    acts    more    rapidly    and    yields 

brilliant  beer.  The  filtration  is  carried  out  in  suitable  frames  through  filter-cloths  or, 
better,  through  finely  divided  cellulose  (such  as  is  used  in  paper-making)  under  a  pressure 
of  about  half  an  atmosphere.  These  filter-presses  are  the  same  in  principle  as,  and  little 
different  in  form  from,  those  which  are  used  for  the  filtration  of  saccharine  liquids  and 
are  described  in  the  section  on  Sugar.  (In  England,  beer  in  cask  is  clarified  by  mixing 
with  the  beer  a  small  quantity  of  finings,  which  consist  of  isinglass  "  cut  "  or  dissolved 
in  an  acid,  such  as  tartaric,  sulphurous,  &c.  ;  these  finings  are  gradually  deposited  on  the 
bottom  of  the  cask  and  carry  down  with  them  any  suspended  protein  substances,  hop- 
resins,  &c.).  Bottling  is  to-day  carried  out  with  all  the  care  employed  in  the  preparation 
of  sparkling  wines.  A  few  lines  may  be  devoted  to  the  preparation  of  beer-casks,  since 
the  methods  employed  are  peculiar  to  the  brewing  industry. 

In  order  that  beer  for  retail  consumption  may  retain  its  flavour,  it  must  be  kept  cool 
and  saturated  with  carbon  dioxide  up  to  the  moment  when  it  is  drawn  off  into  the  customers' 
glasses,  and  for  this  purpose  the  use  of  liquid  carbon  dioxide  with  the  arrangement  shown 
in  vol.  i,  p.  389,  is  well  adapted. 

RESINING  OR  PITCHING  OF  CASKS.  The  keeping  of  beer  sound  depends 
largely  on  the  cleanliness  of  its  surroundings  and  of  the  vessels  in  which  it  is  stored.  Hence 
the  casks,  returned  empty  from  the  customers,  are  first  well  scrubbed  and  washed  both 
inside  and  outside  with  water  under  pressure  by  means  of  automatic  plant  (Fig.  169), 
and  are  then  disinfected  by  means  of  formalin  vapour  or  other  antiseptics,  or,  better  still, 
by  pitching  the  internal  surface  with  natural  or  artificial  resins,  which  should  be  transparent 
and  have  a  melting-point  of  about  50°  ;  in  this  process,  which  was  first  used  in  Bavaria, 
and  is  nowadays  largely  employed  all  over  the  Continent,  aromatic  resins  are  no  longer 
used,  mixtures  of  colophony  with  other  residues  from  the  distillation  of  turpentine  being 
prepared  by  fusion  and  then  rendered  more  elastic  by  the  addition  of  resin  oil  (10  per 
cent.).  To  free  the  casks  from  the  old  resin  and  coat  them  again  every  time  they  are 


PASTEURISATION 


177 


returned  to  the  brewery,  they  are  heated  inside  by  means  of  air  supplied  from  a  Roots 
blower,  B  (Fig.  170),  and  heated  bypassing  through  red-hot  coke,  the  hot  air  being  forced 
into  the  casks  through  the  tubes,  D,  for  5  minutes.  The  old  pitch  is  discharged  and  the 
new  pitch  (about  200  to  250  grms.  per  hectolitre),  fused  and  heated  to  250°,  introduced 
into  the  sterile  cask.  The  bung-hole  is  then  closed,  the  cask  rotated  automatically  for  a 


FIG.  170. 

few  minutes,  the  excess  of  pitch  poured  out,  and  the  rolling  of  the  cask  continued  until 
it  is  cold.  The  lager -vessels  used  for  the  maturation  of  the  beer  are  treated  in  a  similar 
way. 

PASTEURISATION.  Beer,  more  than  wine,  is  subject  to  numerous  changes  and 
diseases  (turbidity  due  to  inferior  materials,  incomplete  saccharification  or  excess  of 
proteins  ;  acidity  caused  by  acetic  or  lactic  acid  ;  stinking  fermentation  produced  by 


FIG.  171. 

various  bacteria,  &c.),  and  it  is  difficult  to  remedy  these  inconveniences  except  by  improve- 
ment in  the  methods  of  working.  In  order  that  beer  may  remain  unchanged  when  kept 
for  a  long  time  in  bottle  or  when  sent  to  hot  places,  it  is  advisable  to  pasteurise  it.  The 
bottles  are  tightly  stoppered  and  placed  in  vessels  containing  cold  water,  which  is  then 
gradually  heated  to  a  maximum  of  60°  to  65°,  this  temperature  being  maintained  for  10 
minutes  ;  the  vessels  should  be  covered  so  as  to  avoid  danger  from  breakages.  The 
water-bath  is  subsequently  allowed  to  cool  slowly  to  the  ordinary  temperature.  Top- 
fermentation  beers  are  rarely  pasteurised,  as  they  sometimes  acquire  an  unpleasant  flavour 

II  12 


178 


ORGANIC    CHEMISTRY 


under  this  treatment ;  bottom-fermentation  beers,  however,  undergo  no  change  and  keep 
good  even  for  ten  years. 

In  large  breweries,  very  efficient  pasteurising  apparatus  is  employed,  the  bottles  being 
moved  automatically  in  suitable  vessels  in  which  the  water  moves  in  the  opposite 
direction. 

Of  the  many  improved  forms  in  use  at  the  present  time,  the  Gasquet  circular  type  is 
shown  in  Pig.  171.  Here  the  chambers  are  filled  successively  with  baskets  of  bottles, 
which  are  raised  by  suitable  cranes.  The  water,  at  a  gradually  increasing  temperature, 
is  drawn  from  each  chamber  by  means  of  a  tube  communicating  with  a  pump,  heated  by 
a  central  thermo-syphon,  and  then  passed  on  to  the  succeeding  chamber.  A  bell  rings 
every  five  minutes  as  a  signal  for  the  bottles  of  a  cool  chamber  to  be  removed  and  replaced 
by  fresh  ones. 

The  bottles  are  made  of  a  special  glass,  which  diminishes  the  proportion  of  breakages 
to  less  than  1  per  cent. 

ALCOHOL-FREE  BEER.  A  proposal  has  recently  been  made  to  manufacture 
beer  containing  no  alcohol  by  treating  wort  directly  at  0°  with  yeast  which  has  previously 
been,  subjected  to  special  treatment  effecting  the  destruction  of  almost  all  of  the  zymase 
but  not  that  of  the  peptase  and  other  proteolytic  enzymes  ;  the  carbohydrates  hence  give 
no  alcohol,  the  proteins  alone  being  decomposed.  These  yeasts  remove  the  flavour  of 
fresh  wort,  the  beer  being  used  before  alcoholic  fermentation  begins  (Ger  Pat.  180,128). 

COMPOSITION  AND  ANALYSIS  OF  BEER.  The  most  varied  types  of 
beer  are  found  in  different  countries,  and  of  each  type  there  are  usually  the 
two  qualities — pale  and  dark.1  The  density  varies  from  1-010  to  1-030,  and 
the  amount  of  alcohol  usually  from  3-5  to  4-5  per  cent,  by  volume,  although 
export  beers  often  contain  5  to  5-5  per  cent,  of  alcohol,  and  certain  special 
beers  still  more.  The  amount  of  extract  also  varies  considerably,  being  as 

1  The  compositions  of  some  of  the  best-known  beers  are  as  follow  : 


Alcohol 

Extract 

Ash 

Real 

attenuation 

per  cent, 
by  vol. 

per  cent, 
by  vol. 

per  cent, 
by  vol. 

per  cent, 
by  vol. 

Pale  Berlin  beer             .... 

3-91 

4-85 

0-14 

60-50 

Berlin  lager  beer  .....                   . 

4-00 

6-15 

0-20 

54-70 

Export  Bavarian  beer  .          .          .          .                   . 

4-78 

1067 

0-29 

45-44 

Munich  Spaten  beer  (at  Munich)    . 

3-23 

6-61 

0-28 

48-40 

,,           ,,      (at  Milan)      .         . 

5-23 

— 

— 

— 

Salvator  beer'  .          .                   . 

4-64 

9-08 

0-28 

49-00 

Spaten  table  beer      .         .         . 

7-0 

10-35 

— 

57-40 

Bock        ..... 

4-20 

7-10 



54-20 

white  beer        .... 

3-51 

4-73 



59-58 

Vienna  lager  beer          .... 

3-62 

6-01 

— 

54-50 

Pilsen  beer  ...... 

3-47 

4-97 

— 

59-00 

North  of  France  beer    .... 

3-20 

4-04 

— 

61-20 

Amsterdam  beer  ..... 

4-30 

7-0 

— 

36-40 

Brussels  Iambic    ..... 

5-94 

3-30 



78-00 

Belgian  faro          ..... 

4-33 

5-1 

— 

62-80 

Bass's  pale  ale      ..... 

6-15 

6-87 

— 

64-00 

Scotch  pale  ale     ..... 

8-50 

10-90 

— 

59-9 

Dublin  stout         ..... 

7-23 

6-15 

— 

70-64 

London  porter      .:.... 

5-40 

6-00 

'     — 

63-3 

American  beer      ..... 

5-89 

6-45 

— 

63-15 

Milan  beer  :  Pilsen  type          ... 

3-92 

5-43 

0-21 

57-91 

,,        „      Munich  type       ... 

3-50 

5-58 

0-20 

54-63 

Porretti  beer  (Varese)   .... 

3-98 

5-66 

0-22 

57-45 

Italia  beer  (made  at  Milan  by  the  modified  Nathan- 

Bolze  process)  ....... 

4-78 

6-00 

0-22 

59-43 

The  real  attenuation  (or  degree  of  fermentation,  see  p.  174)  is  calculated  by  multiplying  the  percentage  of  nlcohol 
by  1-92  (=  d'),  and  adding  to  this  product  the  extract  of  the  beer,  d ;  this  gives  the  extract,  D,  contained  in  the 

D  —  d 
wort  prior  to  fermentation  and  then  the  attenuation  or  percentage  of  extract  fermented  =  — — —  X  100. 

Some  English  breweries  make  stout  from  a  mixture  of  65  per  cent,  of  pale  malt,  10  per  cent,  of  black  malt  (for 
colour),  10  por  cent,  of  caramelised  malt  and  sometimes  10  per  cent,  of  cane-sugar  and  5  per  cent,  of  maize.  This 
very  dark  beer  is  attenuated  to  a  relatively  small  extent,  and  retains  a  full,  sweet  taste,  this  being  partly  due  to 
the  almost  entire  absence  of  gypsum  in  and  the  small  total  hardness  of  London  water  ;  these  beers  also  contain  few 
hops.  Export  stout  is  made  from  worts  having  gravities  as  high  ag  25°  Balling,  whilst  porter  is  lighter  jn  character, 
J'he  pale  beers  of  Berlin  are  made  with  a  gggd  proportion  (75  per  00nt-)  Q*  malted  wheat, 


BEER    STATISTICS  179 

much  as  12  per  cent,  for  certain  types  of  beer  ;  for  ordinary  beers  it  lies 
between  5  and  6  per  cent.  (1  per  cent,  being  maltose).  The  proportion  of  ash 
is  generally  less  than  0-3  per  cent.  The  amount  of  carbon  dioxide  dissolved 
varies  from  0-15  to  0-40  per  cent. 

The  analysis  qf  beer  is  carried  out  in  a  similar  manner  to  that  of  wine  (p.  157),  but 
the  carbon  dioxide  is  eliminated  by  heating  the  beer  to  40°  and  shaking  for  several  minutes 
before  the  specific  gravity  and  acidity  are  determined  ;  the  latter  does  not  exceed  0-3  per 
cent,  and  is  expressed  as  lactio  acid  (1  c.c.  N/10-alkali  =  0-009  grm.  lactic  acid)  or  as 
cubic  centimetres  of  normal  alkali  used  per  100  c.c.  of  beer.  To  avoid  frothing  during  the 
distillation  of  the  alcohol,1  a  little  tannin  is  added.  The  nitrogenous  substances  are  deter- 
mined on  the  extract  of  40  c.c.  of  the  beer  by  Kjeldahl's  method  (p.  10),  the  proportion  of 
nitrogen  being  multiplied  by  6-25  to  give  the  corresponding  amount  of  proteins.  The 
reducing  sugar  is  determined  by  means  of  Fehling's  solution  and  is  calculated  as  maltose 
(see  Note,  p.  167).2 

STATISTICS.  In  Italy  the  brewing  industry  has  never  been  in  a  flourishing  condition, 
owing  to  the  abundance  and  cheapness  of  wine — possibly  more  commonly  drunk  than  water. 
The  beer  manufactured  from  remote  epochs  in  Italy  was  made  by  the  top -fermentation 
process  and  was  of  poor  quality  ;  it  did  not  keep  well  in  summer,  was  stored  carelessly 
by  the  retailers  and  was  consumed  for  only  about  a  couple  of  months  in  the  year — 
close  to  where  it  was  produced.  Technical  improvements  have  been  introduced  tardily, 
but  nowadays  the  industry  is  largely  concentrated  into  a  few  large  breweries  using  the 
most  modern  methods  and  controlled  by  technical  experts  from  other  countries. 

About  one -half  of  the  beer  imported  into  Italy  is  supplied  by  Austria -Hungary,  about 
one -third  by  Germany,  and  one -tenth  by  Switzerland  : 

PRODUCTION,  IMPORTATION,  AND  CONSUMPTION  OF  BEER  IN  ITALY 

Consumption 

Production  Imports  Total  Per  head 

hectols.  hectols.  in  cask  hectols.  litres 

1880  .  ".  116,000  .  .  46,900  . .  163,000  .  .  0-57 

1890  .  .  160,900  .  .  99,500  .  .  260,000  .  .  0-86 

1894-95  .  .  95,500  ..  60,000  ..  156,000  ..  0-50 

1900  .  .  154,000  .  .  54,750  .  .  209,000  . .  0-66 

1903  .'  .  185,000  .  .  70,000  .  .  255,000  . .  0-79 

1904  .  .  220,000  .  .  80,000  .  .  300,000  .  .  0-92 
1905-06  .  .  304,000  .  .  90,000  .  .  394,000  .  .  1-20 
1906-07  .  .  360,000  ..  94,494  ..  455,000  ..  1-50 
1907-08  .  •  .  400,000  ..  95,213  ..  495,000  ..  1-60 
1908-09  .  .  473,000  ..  88,100  ..  561,000  ..  1-80 
1909-10  .  .  563,000  .  .  89,737  .  .  651,000  .  .  2-00 

1  The  proportion  of  alcohol  can  be  calculated  indirectly  by  means  of  the  formula,  A  =  (s/S)  -4-  8,  where 
A  indicates  the  percentage  of  alcohol,  s  the  specific  gravity  of  the  beer,  S  the  specific  gravity  of  the  beer  freed 
from  alcohol  and  made  up  to  the  original  volume  ;  the  alcohol  Table  (p.  148)  gives  the  percentage  by  weight 
corresponding  to  the  value  of  s/S  and  division  of  this  percentage  by  S  gives  the  true  percentage  of  alcohol. 

8  The  determination  of  sulphurous  add  (only  traces  are  allowed  in  beer)  derived  from  sulphites  or  sulphurous  acid 
added  to  preserve  the  beer,  is  effected  by  distilling  200  c.c.  of  the  beer,  previously  acidified  with  5  c.c.  of  syrupy 
phosphoric  acid,  in  a  current  of  carbon  dioxide  and  passing  the  distillate  through  50  c.c.  of  iodine  solution  (5  grms. 
I  +  7-5  grms.  KI  made  up  to  1  litre  with  water) ;  the  iodine  solution  is  then  acidified  with  hydrochloric  acid, 
boiled  to  expel  excess  of  iodine  and  precipitated  with  barium  chloride,  the  filtered,  washed,  and  ignited  barium 
sulphate  being  weighed  ;  multiplication  of  this  weight  by  1-372  gives  the  amount  of  SO2  per  litre  of  beer.  For 
the  detection  of  boric  and,  100  c.c.  of  beer  are  evaporated  to  dryness  and  the  residue  calcined  ;  a  little  sulphuric 
acid  and  alcohol  are  then  added  to  the  resulting  ash  and  the  mixture  ignited  and  stirred  ;  the  appearance  of  a 
green  colour  at  the  edges  of  the  flame  indicates  the  presence  of  boric  acid.  The  quantitative  determination  of 
boric  acid  is  difficult  and  is  only  rarely  carried  out,  Rosenbladt  and  Gooch's  method  being  then  used. 

For  the  detection  of  fluorides,  sometimes  (although  prohibited)  added  as  preservative,  100  c.c.  of  the  beer, 
rendered  alkaline  with  ammonium  carbonate,  are  boiled,  mixed  with  3  to  4  c.c.  of  calcium  chloride  solution,  boiled 
again  for  5  minutes  and  filtered,  the  residue  being  washed  and  calcined  in  a  platinum  crucible.  One  cubic  centi- 
metre of  concentrated  sulphuric  acid  is  then  added  and  the  crucible,  covered  with  a  watch-glass  partly  coated 
with  paraffin  wax,  gently  heated.1  In  presence  of  fluorides,  the  glass  is  attacked  in  the  unprotected  parts. 

The  degree  of  attenuation  or  of  fermentation  is  calculated  as  indicated  in  the  Note  on  the  preceding  page. 

Adulteration  with  salicylic  acid  is  detected  by  acidifying  100  c.c.  of  the  beer  with  5  c.c.  of  hydrochloric  acid  and 
shaking  with  50  c.c.  of  ether  and  50  c.c.  of  light  petroleum.  The  ethereal  solution  is  separated  and  evaporated  to 
dryness,  the  residue  being  taken  up  in  water  and  filtered.  If  the  liquid  gives  a  violet  coloration  with  a  little 
dilute  ferric  chloride  solution  and  a  red  one  with  MiKon'9  mgent  (aqueous  mercuric  nitrate  containing  a  little 
nitrous  acid),  the  presence  of  salicylic  acid  is  certain, 

Saccharin  \»  determiped  by  evaporating  an.  ethereal  fjrfrapt  obtained  as  abpve,  dissolving  fte  resjdup  is  a  Jltyfe 


180  ORGANIC    CHEMISTRY 

The  consumption  of  beer  in  Italy  takes  place  mostly  in  the  towns  of  the  north  and 
centre,  and  the  average  consumption  per  head  in  Milan,  Turin,  or  Rome  is  at  least  ten 
times  that  for  the  whole  country. 

The  production  of  beer  in  Japan  was  362,000  hectols.  in  1907  ;  294,100  in  1908  ;  271,500 
in  1909,  and  280,000  in  1910. 

The  production  of  beer  in  other  countries  in  1900  was  as  follows  :  Germany,  67,000,000 
hectols.  or  118  litres  (in  1907,  70,  and  in  1910,  64  litres)  per  head.  England,  59,000,000 
hectols.  (57,000,000  or  150  litres  per  head  in  1909).  Austria -Hungary,  20,000,000  hectols. 
(72  litres  per  head)  or  19,000,000  in  1909.  Belgium,  14,000,000  hectols.  (213  litres  per  head). 
France  9,000,000  hectols.  (25  litres  per  head ;  but  here,  too,  the  consumption  is  localised,  the 
annual  consumption  per  head  in  Lille  being  360  litres) ;  in  1909  France  produced  11,000,000 
hectols.  The  United  States,  48,000,000  hectols.  (63  litres  per  head)  in  1900  and  70,000,000 
in  1909.  Spain,  about  1,000,000  hectols.,  and  Russia,  6,200,000  hectols.  in  1909. 

In  1900,  Germany,  with  10,000  breweries,  produced  twice  as  much  beer  as  in  1880, 
and  in  1885  exported  1,500,000  hectols.  One  large  brewery  in  Germany  makes  more 
beer  than  the  whole  of  Italy  consumes.  (Italy  has  93  breweries  at  the  present  time.) 

In  1881,  England  produced  45,000,000  hectols.  ;  Austria -Hungary,  12,000,000  ;  Belgium 
9,000,000  ;  France,  8,000,000  ;  Switzerland,  1,000,000  (now  1,500,000),  and  the  United 
States,  19,000,000. 

The  world's  production  of  beer  in  1910-11  was  271,000,000  hectols. 

In  Italy  the  brewing  tax  was  5fd.  up  to  1891,  when  it  was  raised  to  ll^d.  (causing  a 
temporary  diminution  in  the  consumption  at  that  time)  per  saccharometer  degree  per 
hectolitre,  measured  with  the  decimal  saccharometer  at  17'5°  on  the  wort  from  the  cooler, 
an  allowance  of  12  per  cent,  being  made  for  loss  during  the  subsequent  operations  ;  the 
tax  varied  from  a  minimum  of  115d.  to  a  maximum  of  184d.  per  hectolitre,  according  to 
the  strength  of  the  beer.  Imported  beer  pays  29d.  more,  or  the  importers  can  demand  the 
tax  to  be  levied  on  the  extract  degrees,  these  being  increased  by  twice  the  number  of 
alcohol  degrees.  The  exchequer  collected  £180,000  in  1905-6  and  £211,800  in  1906-1907 
as  tax  of  manufacture. 

In  Germany  beer  costs  about  12s.  per  hectolitre,  or  rather  more  with  the  extra  taxation 
of  1910.  In  Italy  the  cost  is  about  32s.  (that  imported  from  well-known  breweries  about 
40s.  per  hectolitre). 

ALCOHOLS   HIGHER  THAN  ETHYL 

PROPYL  ALCOHOLS,  C3H8O.     The  two  isomerides  theoretically  possible  are  known  : 

(1)  Normal,  CH3  •  CH2  •  CH2  •  OH  (propanol-1  or  ethylcarbinol).     This  can  be  obtained 
from  fusel  oil  (p.  122)  by  fractional  distillation  or  from  its  bromo -derivative.     It  has  an 
agreeable  odour,  b.pt.  97°,  sp.  gr.  0-804,  and  is  readily  soluble  in  water.     On  oxidation  it 
gives  propionic  acid,  which  proves  its  constitution. 

(2)  Sec.  or  Iso-Propyl  Alcohol,  CH3-CH( OH)- CH3  (propanol-2  or  dimethylcarbinol),  is 
a  colourless  liquid,  b.pt.  81°,  sp.  gr.  0-789.     It  is  obtained  from  isopropyl  iodide  and  hence 
indirectly  from  glycerol,  or  by  reducing  acetone  with  sodium  amalgam,  the  constitution 
attributed  to  it  being  thereby  confirmed. 

BUTYL  ALCOHOLS,  C4H10O.  The  four  isomerides,  predicted  by  theory,  are 
known  : 

(1)  Normal  Butyl  Alcohol,  CH3-CH2- CH2-CH2- OH  (l>utanol-\  or  propylcarbinol),  is  a 
liquid,  b.pt.  117°,  sp.  gr.  0-810,  and  has  an  irritating  odour  ;  12  vols.  of  water  at  22°  dissolve 
only  1  vol.  of  it,  this  being  separated  from  the  solution  by  the  addition  of  a  soluble  salt. 

sodium  carbonate  solution,  evaporating  in  a  silver  dish  and  fusing  the  residue  with  solid  caustic  soda ;  the  white 
mass  is  dissolved  in  water,  the  solution  acidified  with  hydrochloric  acid,  and  the  sulphuric  acid  (derived  from 
the  sulphonic  group  of  the  saccharin)  precipitated  quantitatively  as  barium  sulphate.  The  weight  of  the  latter, 
multiplied  by  0-785,  gives  the  weight  of  saccharin. 

Caramel,  rjdded  to  colour  the  beer  is  recognised  by  shaking  20  c.c.  with  about  30  to  40  grms.  (i.e.  until  saturated) 
of  solid  sodium  sulphate  and  60  c.c.  of  05  per  cent,  alcohol.  If  the  lower  liquid  is  markedly  coloured  and  forms  a 
greenish  brown  deposit,  the  presence  of  caramel  is  indicated ;  beer  .containing  no  caramel  becomes  decolorised 
and  gives  only  a  greenish  or  dark  greenish  brown  deposit  if  it  contains  coloured  malt. 

Picric  acid  is  detected  by  evaporating  a  litre  of  the  beer  to  a  syrupy  consistency,  extracting  with  boiling  absolute 
alcohol,  filtering  and  evaporating  the  alcoholic  liquid,  dissolving  the  residue  in  water,  adding  a  few  drops  of  hydro- 
chloric acid  and  heating  for  an  hour  with  a  few  strands  of  wool ;  if  the  latter  are  coloured  yellow,  picric  acid  is 
present. 

Extraneous  bitter  substances  are  tested  for  by  evaporating  2  litres  of  beer  to  half  its  volume  and  precipitating 
the  residue  in  the  hot  with  lead  acetate  ;  the  hot  liquid  is  filtered  rapidly  and  the  lead  then  precipitated  with 
ammonium  sulphate  and  filtered  off.  The  filtrate  should  have  no  bitter  taste. 


BUTYL,   AMYL,   AND   HIGHER   ALCOHOLS     181 

It  is  found  in  fusel  oil  and  can  be  obtained  by  fermenting  glycerol  or  mannitol  (yield 
8  to  10  per  cent.)  with  Bacillus  butylicus  (contained  in  the  excreta  of  cows).  It  can  also 
be  prepared  synthetically  by  the  various  general  processes  (p.  104).  Its  constitution  is 
indicated  by  its  syntheses  and  by  the  possibility  of  transforming  it  into  normal  butyric 
acid  by  oxidation. 

(2)  Secondary  Butyl  Alcohol,  CH3  •  CH2  •  CH(OH)  •  CH3  (butanol-2  or  ethylmethylcarbinol) 
is  a  liquid  with  an  intense,  peculiar  odour,  b.pt.  100°,  sp.  gr.  0-808.     It  can  be  obtained  by 
treating  the  tetrahydric  alcohol,  erythritol,  C4H6(OH)4,  with  hydriodic  acid  or  by  the 
interaction  of  normal  butylene  and  hydriodic  acid  and  hydrolysis  of  the  resulting  iodide. 

/ITT 

(3)  Isobutyl  Alcohol,  ^^^CH  •  CH2  •  OH  (methylpropanol),  is  termed  also  butyl  alcohol 


of  fermentation,  since  it  abounds  in  the  fusel  oil  of  potatoes,  from  which  it  can  be  extracted 
by  forming  the  corresponding  iodo  -compound.  It  is  a  colourless  liquid,  b.pt.  107°,  sp.  gr. 
0-806,  and  has  a  characteristic  alcoholic  smell.  Its  constitution  is  determined  by  the 
fact  that,  on  oxidation,  it  yields  isobutyric  acid,  the  constitution  of  which  is  known. 

C*TT 

(4)  Tertiary  Butyl  Alcohol,  r,T4-3>C(OH)-CH3  (trimethylcarbinol  or  methyl-2-propanol), 
Or±3 

occurs  in  small  proportion  in  fusel  oil,  and  can  be  prepared  by  the  action  of  hot  75  per  cent. 
sulphuric  acid  on  isobutylene,  which  thus  takes  up  1  mol.  of  water.  When  pure,  it  forms 
rhombic  prisms  or  plates,  m.pt.  25-5°,  sp.  gr.  0-786  (solid),  b.pt.  83°.  On  oxidation  it  gives 
acetic  acid,  acetone,  and  carbon  dioxide. 

AMYL   ALCOHOLS,  C6HU.OH.     The  eight  isomerides    theoretically  possible    are 
known,  the  most  important  being  : 

(1)  Normal  Amyl  Alcohol,    CH3  -  CH2  •  CH2  -  CH2  •  CH2  -  OH    (pentanol-l),    b.pt.    138°, 
sp.  gr.  0-817,  is  of  little  importance,  and  is  obtained  by  reducing  normal  valeraldehyde  or 
by  the  other  general  methods. 

(2)  Amyl  Alcohol  of  Fermentation,        3>CH-CH2-  CH2-  OH   (methyl-3-butanol-I    or 

L>±13 

isobutylcarbinol),  is  a  liquid,  b.pt.  130°,  sp.  gr.  0-810,  and  is  solid  at  —134°.  It  imparts 
its  characteristic  smell  and  burning  taste  to  fusel  oil,  in  which  it  abounds.  It  is  to  this 
alcohol  that  the  poisoning  effect  of  spirits  is  principally  due.  It  occurs  naturally  in  Roman 
chamomile  oil. 

(3)  Active  Amyl  Alcohol,  /Lr^CH  •  CH2  •  OH   (methyl-2-butanol-l   or  2-methylbutan- 

L>rL3 

l-ol),  boils  at  128°,  has  the  sp.  gr.  0-816,  and  is  found  with  the  amyl  alcohol  of  fermentation. 
It  contains  an  asymmetric  carbon  atom  (see  p.  19)  and  is  laevo  -rotatory,  whilst  the  halogen 
compounds  and  the  valeric  acid  derived  from  it  are  dextro-rotatory  ;  also  the  dextro- 
isomeride  of  this  acid  yields  a  laevo  -rotatory  iodide. 

PTT 

(4)  Tertiary  Amyl  Alcohol,  ^TT3>C(  OH)-  CH2-CH3    (methyl-2  -butanol-2    or   amylene 

CM3 

hydrate  or  dimethylethylcarbinol)  is  an  oily  liquid  with  a  faint  odour  of  mint.  It  boils  at 
102°  and  is  prepared  from  amylene  by  the  indirect  addition  of  water  under  the  influence  of 
sulphuric  acid.  It  exerts  a  soporific  action. 

HIGHER  ALCOHOLS.  Of  these  may  be  mentioned  :  Primary  normal  hexyl  alcohol 
or  hexanol,  CH3-  [CH2]4-CH2-OH  (14  of  the  18  hexyl  alcohols  predicted  by  theory  are 
known),  can  be  obtained  from  caproic  acid,  C6H1202,  and  is  found  as  butyric  and  acetic 
esters  in  the  ethereal  oil  of  the  seeds  of  Heracleum  giganteum  and  in  the  fruit  of  Heracleum 
spondylium  :  it  boils  at  158°  (under  740  mm.  pressure),  and  has  a  specific  gravity  of  0-820. 
Caproyl  or  isohexyl  alcohol,  (CH3)2  :  CH  •  CH2  •  CH2  •  CH2  •  OH,  b.pt.  150°,  is  f  ound  in  vinasse 
and  in  fusel  oil.  Heptyl  (or  oznanthyl)  alcohol,  C7H16O  ;  of  the  ^38  possible  isomerides, 
13  are  known.  Normal  octyl  alcohol,  C8H18O,  is  contained  in  Heracleum  spondylium  and 
H-eracleum  giganteum  ;  secondary  octyl  alcohol  (or  capryl  alcohol  or  methylhexylcarbinol)  is 
formed  on  distilling  castor  oil.  Other  higher  alcohols  are  obtained  by  reducing  the  corre- 
sponding aldehydes  with  zinc  dust  and  acetic  acid  ;  they  are  almost  solid,  like  paraffin  wax. 
Cetyl  or  normal  hexadecyl  alcohol,  C^H^O,  combined  with  palmitic  acid,  forms  the  principal 
component  of  sperm  oil.  Ceryl  alcohol  (cerotin),  C26H53  •  OH,  occurs  as  cerotic  ester  in  Chinese 
wax  and  in  wool-fat  ;  it  melts  at  76°  to  79°.  Melissyl  or  myricyl  alcohol,  C30H61  •  OH, 
is  found  as  the  palmitic  ester  in  beeswax  and  carnauba  wax  and  is  obtained  free  by  saponi- 
fication  with  alcoholic  potash. 


182 


II.   UNSATURATED   MONOHYDRIC  ALCOHOLS 


These  are  similar  to  the  saturated  alcohols,  but,  as  they  contain  one  or  .two  double 
linkings,  they  behave  like  the  olefines  and  diolefines  in  taking  up  two  or  four  atoms  of 
hydrogen,  halogens,  &c.,  to  give  saturated  compounds.  If  they  contain  a  triple  linking, 
— C  ^  CH,  they  form  explosive  metallic  compounds,  as  does  acetylene  (p.  91 ). 

VINYL  ALCOHOL,  CH2  :  CH-OH  (Ethenol),  appears  to  be  present  in  commercial 
ether,  but  it  has  never  been  isolated,  attempts  to  synthesise  it  leading,  as  is  the  case  with 
other  similar  compounds,  to  an  isomeride — acetaldehyde,  CH3-CHO  ;  the  formation  of 
the  latter  is  explained  by  the  addition  of  a  molecule  of  water  to  the  alcohol,  and  immediate 
loss  of  a  molecule  of  water  from  the  compound  thus  formed. 

ALLYL  ALCOHOL,  CH2  :  CH-CH2-OH  (Propenol),  is  a  liquid  of  pungent  odour, 
b.pt.  97°,  and  readily  soluble  in  water.  It  is  formed  in  small  quantity  in  the  distillation  of 
wood,  but  is  more  easily  obtained  by  heating  glycerol  at  26°  with  oxalic  acid  and  a  little 
ammonium  chloride.  Cl,  Br,  CN,  and  HC10  can  be  added  on  to  it  directly,  but  not  H. 
When  cautiously  oxidised,  it  takes  up  O  and  H2O,  giving  glycerol  or  even  acrolein  (ally! 
aldehyde)  and  acrylic  acid,  which  shows  it  to  be  a  primary  alcohol. 

CITRONELLOL,  C10H2oO,  is  found  in  attar  of  roses. 

PROPARGYL  ALCOHOL,  CH  •  C-CH2-OH  (Propinol),  is  a  liquid  with  a  pleasant 
odour,  lighter  than  water,  b.pt.  114°. 

GERANIOL,  C10Hl8Oor(CH3)2  :  C  :  CH-CH2-CH2-C(CH3)  :  CH-CH2-OH,  is  a  pleasant- 
smelling  oil,  b.pt.  121°  under  17  mm.  pressure.  It  is  obtained  from  geranium  oil,  and 
on  oxidation  gives  citral  (the  corresponding  aldehyde)  which  occurs  in  mandarin  oil  and 
in  essences  of  orange  and  lemon  and  to  a  very  considerable  extent  (60  per  cent.)  in 
verbena  oil. 

III.  POLYHYDRIC  ALCOHOLS 
(a)  DIHYDRIC  ALCOHOLS  OR  GLYCOLS,  CWH2,XOH)2 

Substitution  of  two  hydrogen  atoms  joined  to  different  carbon  atoms 
by  two  hydroxyl  groups  gives  dihydric  alcohols,  containing  two  alcoholic 
groups.  It  is  not,  however,  possible  to  have  two  hydroxyl  groups  united  to 
the  same  carbon  atom — although  similar  compounds  are  known  for  the  ether 
derivatives  known  as  Acetals  (see  later) — since  even  if  they  could  be  formed 
they  would  immediately  lose  a  molecule  of  water,  forming  aldehydes  or 
ketones. 

The  dihydric  alcohols,  owing  to  their  sweet  taste,  were  called  Glycols  by 
Wurtz,  who  prepared  them  by  transforming  a  dihalogenated  hydrocarbon  into 
the  corresponding  diacetyl-ester  by  means  of  silver  acetate  and  then  saponi- 
fying the  diacetyl  compound  either  by  baryta  or  sodium  hydroxide  or  by 
boiling  with  water  and  lead  oxide  or  sodium  carbonate  solution  : 

CH2Br  CH2.0-COCH3 

1  +2CH3-COOAg   =  2AgBr+    I 

CH2Br  CH2-0-COCH3 

Ethylene  bromide  Diacetylglycol 

CH2.0-COCH3  CH2-OH 

+  2KOH  =  2CH3-COOK  +    I  (glycol) 

CH2-0-COCH3  CH2-OH 

A  special  group  of  glycols,  the  pinacones,  containing  two  adjacent  tertiary 
alcohol  groups  (=C-OH),  are  formed  by  reducing  the  ketones  with  sodium 
and  water,  or,  better,  together  with  isopropyl  alcohol,  by  electrolysing  a  dilute 
solution  of  sulphuric  acid  and  acetone,  the  latter  being  reduced  at  the 
negative  pole  : 

CH3-C(OH)-CH3 
3CH3  •  CO  •  CH3  +  H4  =  CH3  •  CH(OH)  •  CH3  +  | 

CH3-C(OH)-CH3 


POLYHYDRIC    ALCOHOLS  183 

this  pinacone  (2  :  3-dimethyl-2  :  3-butandiol),  melts  at  38°,  boils  at  172°  and 
crystallises  with  6H2O.  When  distilled  with  dilute  sulphuric  acid,  it  is 
transformed  into  pinacotine,  (CH3)3C-CO-  CH3,  with  separation  of  H20 
and  transposition  of  an  alkyl  group. 

The  glycols  have  an  almost  oily  appearance  ;  their  solubility  and  sweetness 
increase  with  the  molecular  weight ;  the  specific  gravity  and  boiling-point  are 
much  higher  than  those  of  the  monohydric  alcohols  with  equal  numbers  of  carbon 
atoms.  The  hydroxyl  groups  of  the  glycols  behave  like  those  of  monohydric 
alcohols,  so  that  the  glycols  can  give  rise  to  ethers  and  esters,  alkoxides  (sodium, 
&c.),  halogen  compounds  (e.g.  the  chlorohydrins),  aldehydes  and  acids,  besides 
which  they  may  give  up  1  mol.  of  H20  forming  anhydrides. 

ETHYLENE  GLYCOL  (Ethan-1  :  2-diol),  C2H4(OH2),  is  a  dense  liquid,  b.pt.  198°, 
and,  on  oxidation,  yields  glycollic  acid,  CO2H  •  CH2  •  OH  and  oxalic  acid,  C02H  •  C02H. 

PROPYLENE  GLYCOLS.  Two  isomerides  are  known :  a-Propylene  Glycol, 
OH.CH2-CH(OH)-CH3  (propan-1  -.  2-diol),  boils  at  188°  and  is  formed  in  the  distillation 
of  glycerolwith  sodium  hydroxide.  It  contains  an  asymmetric  carbon  atom  and,  by  the 
action  of  certain  ferments,  the  Isevo -rotatory  isomeride  can  be  isolated.  /3 -Propylene 
Glycol  boils  at  216°  and  is  formed  by  the  bacterial  decomposition  of  glycerol,  as  well  as  by 
the  usual  synthetical  methods. 

In  the  higher  glycols,  when  the  two  hydroxyl  groups  have  four  carbon  atoms  between 
them  (y-glycols),  water  is  readily  separated  and  furan  derivatives,  analogous  with  pyrrole 
and  thiophene  compounds,  formed. 

(6)  TRIHYDRIC  ALCOHOLS,  C,,H2w.1(OH)3 

These  are  colourless,  dense  liquids  with  a  sweetish  taste  and  readily  soluble 
in  water  ;  they  contain  at  least  three  carbon  atoms  and  three  hydroxyl  groups, 
and  are  hence  capable  of  forming  three  series  of  esters  by  combination  with  a 
monobasic  acid. 

GLYCEROL,  C3H5(OH)3,  or  OH-CH2-CH(OH)-CH2-OH  (Propantriol), 
was  discovered  by  Scheele  in  1779.  Chevreul  and  Braconnot  (1817)  found  it 
as  a  component  of  all  oils  and  fats.  Its  formula  and  constitution  were  estab- 
lished later  (Pelouze,  Wurtz,  and  Berthelot).  It  occurs  abundantly  in  nature, 
not  in  the  free  state,  but  combined  with  higher  fatty  acids  in  the  form  of  esters 
(glycerides),  which  form  the  fats  and  oils  ;  these  contain  9  to  11  per  cent,  of 
combined  glycerol. 

It  exists  free  in  rancid  fats  and  is  formed  in  small  proportions  in  the  fer- 
mentation of  sugar  (all  wines  contain  0-98  to  1-67  per  cent.).  Industrially 
glycerol  is  obtained  principally  from  factories  where  fats  are  decomposed 
(stearine-  and  soap-works).  Synthetically  it  can  be  obtained  by  transform- 
ing propylene  (from  isopropyl  iodide),  by  means  of  chlorine  in  the  hot,  into 
dichloropropane,  C3H6C12,  which,  with  iodine  chloride,  gives  the  trichloro- 
derivative  C3H5C13  ;  the  latter,  when  heated  with  water  at  170°,  gives  glycerol : 

CH2C1-CHC1-CH2C1  +  3H2O  =  3HC1  +  OH-CH2-CH(OH)-CH2-OH. 

This  formation  of  glycerol  and  also  that  by  the  oxidation  of  allyl  alcohol, 
CH2  :  CH-CH2-OH,  demonstrate  the  constitution  of  glycerol.  On  the  other 
hand,  it  is  possible  to  prepare  glycerol  synthetically  from  the  elements  by  way 
of  acetylene,  acetaldehyde  (p.  91),  acetic  acid,  acetone  (by  distillation  of 
calcium  acetate),  isopropyl  alcohol  (by  reduction),  propylene,  and  thence,  as 
above  to  glycerol  (Friedel  and  Silva). 

PROPERTIES.  Glycerol  (also  termed  glycerine)  is  an  oily,  colourless,  dense 
(sp.  gr.  1-265  at  15°)  liquid,  with  a  sweet  taste  ;  it  is  very  hygroscopic  and 
dissolves  in  all  proportions  in  water  and  alcohol,  heat  being  developed  on  mixing 
58  parts  of  glycerol  with  42  parts  of  water. 

It  is  insoluble  in  ether  and  chloroform  ;  it  dissolves  to  the  extent  of  5  per 


184 


ORGANIC    CHEMISTRY 


cent,  in  dry  acetone  and  to  a  greater  degree  in  aqueous  acetone.  It  boils  at 
290°  with  partial  decomposition,  but  it  can  be  distilled  unchanged  in  a  vacuum 
(at  10  mm.  pressure  it  boils  at  162°).  It  crystallines  at  —40°  or  at  a  higher 
temperature  if  it  contains  water  ;  the  separated  crystals  melt  only  at  22°. 

When  heated  for  a  long  time  at  130°  to  160°  in  presence  of  sulphuric  acid, 
glycerol  loses  one  or  more  molecules  of  water,  giving  anhydrides  or  ethers 
of  glycerol  or  polyglycerines  (A.  Nobel,  1890)  ;  W.  Will  (1904)  arrived  at  the 
same  result  by  heating  glycerol  for  7  to  9  hours  at  290°  to  295°  and  distilling 
off  the  water  formed.  This  treatment  yields  about  60  per  cent,  of  diglycerol, 
C3H5(OH)2-0-C3H6(OH)2,  and  a  little  tri-  and  polyglycerols  ;  all  these  pro- 
ducts can  be  esterified  like  glycerol  and  yield,  e.g.  tetranitrodiglycerine,  which 
does  not  congeal  even  at  —20°  and  has  an  explosive  power  like  trinitroglycerine 
(see  also  C.  Claessen,  Ger.  Pats.  181,754  and  198,768,  1907).  According  to 
U.S.  Pats.  978,443  (1910)  and  13,234  (1911),  glycerol  readily  polymerises 
when  heated  at  275°  in  presence  of  0-5  to  1-0  per  cent,  of  sodium  acetate, 
70  per  cent,  being  polymerised  in  an  hour. 
-  When  it  is  heated  rapidly  and  strongly  it  decomposes,  yielding  partly 

acrolein  with  the  characteristic  pungent  odour.     Also  when  heated  with  P205 

or  KHS04,  it  loses  2H20,  giving  acrolein,  CH2  :  CH-  CHO. 

One  hundred  parts  of  glycerol  dissolve  the  following  quantities  of  mineral 

salts  :  98  of  sodium  carbonate,  60  of  borax,  50  of  zinc  chloride,  40  of  potassium 

iodide,  10  of  boric  acid,  50  of  tannin  ;   bromine,  ammonia,  ferric  chloride,  &c., 

are  also  dissolved. 

Glycerol  has  the  refractive  index  1-476  at  13°  and  in  aqueous  solution  the 

index  varies  proportionally  with  the  dilution.     By  means  of  Lenz's  table,  the 

concentration  of  glycerol  solutions  can  be  determined  from  either  the  specific 

gravity  or  the  index  of  refraction  : 


Per- 
centage of 
glycerol 

Degrees 
Bailing, 
Beck, 
Gerlach 

Sp.  gr.  at 
12°  to  14° 

Index  of 
refraction 
at  12-5°  to 
12-8° 

Per- 
centage of 
glycerol 

Degrees 
Baum€, 
Beck, 
Gerlach 

Sp.  gr.  at 
12°  to  14° 

Index  of 
refraction 
at  12-5°  to 
12-8° 

98 

30-1 

1-2637 

1-4729 

48 

16-2 

1-1265 

1-3979 

96 

29-6 

1-2584 

1-4700 

46 

15-5 

1-1210 

1-3950 

94 

29-1 

1-2531 

1-4671 

44 

15-0 

1-1155 

1-3921 

92 

28-7 

1-2478 

1-4642 

42 

14-3 

1-1100 

1-3890 

90 

28-2 

1-2425 

1-4613 

40 

13-6 

1-1045 

1-3860 

88 

27-7 

1-2372 

1-4584 

38 

13-0 

1-0989 

1-3829 

86 

27-1 

1-2318 

1-4555 

36 

12-3 

1-0934 

1-3798 

84 

26-6 

1-2265 

1-4525 

34 

11-5 

1-0880 

1-3772 

82 

26-1 

1-2212 

1-4496 

32 

11-0 

1-0825 

1-3745 

80 

25-6 

1-2159 

1-4467 

30 

10-3 

1-0771 

1-3719 

78     . 

25-1 

1-2106 

1-4438 

28 

9-6 

1-0716 

1-3692 

76 

24-5 

1-2042 

1-4409 

26 

9-0 

1-0663 

1-3666 

74 

24-0 

1-1999 

1-4380 

24 

8-3 

1-0608 

1-3639 

72 

23-5 

1-1945 

1-4352 

22 

7-6 

1-0553 

1-3612 

70 

23-0 

1-1889 

1-4321 

20 

6-9 

1-0498 

1-3585 

68 

22-3 

1-1826 

1-4286 

18 

6-1 

1-0446 

1-3559 

66 

21-6 

1-1764 

1-4249 

16 

5-6 

1-0398 

1-3533 

64 

21-0 

1-1702 

1-4213 

14 

4-9 

1-0349 

1-3507 

62 

20-3 

1-1640 

1-4176 

12 

3-8 

1-0297 

1-3480 

60 

19-8 

1-1582 

1-4140 

10 

3-4 

1-0245 

1-3454 

58 

19-2 

1-1530 

1-4114 

8 

2-8 

1-0196 

1-3430 

56 

18-6 

1-1480 

1-4091 

6 

2-1 

1-0147 

1-3405 

54 

18-0 

1-1430 

1-4065 

4 

1-3 

1-0098 

1-3380 

52 

17-4 

1-1375 

1-4036 

2 

0-7 

1-0049 

1-3355 

50 

16-9 

1-1320 

1-4007 

GLYCEROL  185 

Glycerol  has  the  interesting  property  of  preventing  the  precipitation  of 
various  metallic  hydroxides  (i.e.  it  keeps  them  dissolved)  ;  for  instance,  in 
presence  of  glycerol,  potassium  hydroxide  does  not  precipitate  salts  of  chromium, 
copper,  &c.  With  alkalis  it  forms  slightly  stable  soluble  alkoxides.  It  does 
not  reduce  silver  or  cupric  salts,  and  hence  cannot  contain  aldehyde  groups  ; 
it  is  not  coloured  by  concentrated  sulphuric  acid  or  by  sodium  hydroxide  on 
boiling.  The  halogens  act  on  glycerol,  not  as  substituting,  but  as  oxidising 
agents.  It  inverts  cane-sugar  and  renders  starch  soluble  ;  100  parts  of  glycerol 
and  six  of  starch  at  190°  give  starch  soluble  in  water,  and  the  starch  can  be 
separated  from  the  glycerol,  when  cold,  by  precipitation  with  alcohol. 

Like  the  other  polyhydric  alcohols  (glycols,  erythritol,  and  its  isomerides, 
also  glucose  and  its  isomerides — galactose,  &c. — but  not  cane-sugar,  quercitol 
or  dextrin)  glycerol,  when  added  in  sufficient  quantity,  transforms  the  alkaline 
reaction  of  borax  solutions  in  an  acid  reaction,  thus  allowing  of  the  determina- 
tion of  boric  acid  and  borax  by  titration. 

Under  the  action  of  certain  schizomycetes,  glycerol  yields  normal  butyl 
alcohol,  butyric  acid  and,  partly,  ethyl  alcohol. 

Being  a  trihydric  alcohol,  glycerol  is  able  to  form  esters  of  three  types 
(mono-,  di-  and  tri-),  according  as  one,  two,  or  three  hydroxyl  groups  are 
replaced  by  inorganic  or  organic  acid  residues.  In  this  way  the  glycerides  can 
be  regenerated  ;  for  example,  when  excess  of  stearic  acid  is  heated  with  glycerol 
at  200°  under  reduced  pressure  until  no  more  water  separates,  tristearin  is 
formed. 

When  cautiously  oxidised,  glycerol  forms  first  glyceric  acid,  OH-CH2- 
CH(OH)-COOH,  which  undergoes  further  oxidation  to  tartronic  acid, 
COOH-CH(OH)'COOH,  so  that  it  is  proved  that  glycerol  contains  two 
primary  alcohol  groups,  (-CH2-OH);  also,  as  tartronic  acid  still  exhibits 
alcoholic  characters,  it  must  contain  a  secondary  alcohol  group.  The  con- 
stitution of  glycerol  is  hence  completely  proved. 

USES  OF  GLYCEROL.  The  majority  of  the  glycerol  manufactured  is 
used  for  the  preparation  of  nitroglycerine  and  hence  of  dynamite  (see  later). 
It  is  also  used  to  give  body  to  light  wines  (termed  Scheelisation,  after  Scheele,  the 
discoverer  of  glycerol).  It  is  employed  in  the  manufacture  of  liqueurs,  syrups, 
preserves,  and  sweetmeats,  since  it  is  sweet  and  dense,  and,  to  some  extent, 
anti-fermentative.  It  is  added  to  chocolate,  tobacco,  cosmetics,  textiles  to  be 
dressed,  and  leather  goods,  since  it  does  not  dry  and  keeps  them  soft  or  pliable. 
It  is  also  used  in  extracting  from  flowers  and  herbs  delicate  perfumes  which 
would  undergo  change  if  extracted  by  distillation. 

It  is  employed  as  a  non-congealing  and  lubricating  liquid  (a  solution  of 
$p.  gr.  1-13)  in  gasmeters  ;  for  greasing  iron  objects  to  prevent  them  from 
rusting ;  for  making  copying-ink,  soap,  and  shoe-polish ;  for  preserving 
anatomical  preparations,  &c. 

INDUSTRIAL  PREPARATION.  Glycerol  is  almost  exclusively  obtained  as  a 
secondary  product  in  the  treatment  of  fats.  Until  the  year  1885  only  the  aqueous  residues 
of  stearine  works  were  worked  up  (the  fats  are  decomposed  with  lime,  sulphuric  acid,  steam, 
or  ferments),  but  nowadays  almost  all  the  alkaline  lye  of  soap  factories  (where  the  fats 
are  treated  directly  with  caustic  soda  and  then  with  salt) 1  are  utilised. 

Of  the  9  to  11  per  cent,  of  glycerol  contained  in  fats,  8  to  10  per  cent,  can  be  recovered 
(only  4  per  cent,  when  the  decomposition  is  effected  by  sulphuric  acid,  the  maximum  yield 
being  obtained  when  water  or  ferments  are  used). 

The  treatment  of  the  dilute  solutions  of  crude  glycerol  varies  with  their  origin  :  soap- 
lyes  (which  are  sometimes  concentrated  in  the  soap-works  and  sold  to  the  glycerol  refiners) 

1  These  lyes  have  an  alkaline  reaction  and,  on  analysis,  one  of  them  gave  the  following  results  :  water,  61  per 
cent.;  glycerol,  16-5  per  cent,  salts;  22  per  cent,  (eight-tenths  of  which  were  NaCI,  one-tenth  Na2SO4,  and 
one-thirtieth  Na2CO,).  The  specific  gravity  varies  from  3°  to  7°  B6.,  and  the  proportion  of  glycerol  usually 
from  6  to  12  per  cent. 


186 


ORGANIC    CHEMISTRY 


are  treated  with  0*1  to  0*2  per  cent,  of  lime  or  ferrous  sulphate  and  mixed  by  means  of  an 
air-jet  ;  the  liquid  is  decanted,  slightly  acidified  with  hydrochloric  acid  and  skimmed  ; 
a  small  quantity  of  aluminium  sulphate  is  then  added,  the  liquid  being  decanted,  rendered 
slightly  alkaline,  passed  through  a  filter-press  and  concentrated  in  open  boilers  furnished 
with  stirrers  until  sodium  chloride  begins  to  separate  ;  subsequent  concentration  to  the 
sp.  gr.  28°  Be.  is  carried  out  in  a  vacuum,  the  salt  deposited  being  gradually  removed.  This 
crude  glycerol  contains  85  to  90  per  cent,  of  glycerol  and  1  per  cent,  of  salts,  and  has  a  dark 
yellow  or  brownish  colour.  Sometimes  the  alkali  is  removed  from  the  soap  lyes  by  adding  a 

little  resin  and  boiling,  so  that  the 
resin  soap  formed  is  carried  to  the 
surface  and  can  be  decanted  (to  be 
utilised  by  adding  to  ordinary  soap). 
The  free  lime  may  also  be  pre- 
cipitated with  an  oxalate  or  with 
carbon  dioxide.  The  concentration 
is  not  carried  out  in  open  vessels, 
as,  when  the  aqueous  solutions  are 
vigorously  boiled,  the  steam  given 
off  carries  away  appreciable  quan- 
tities of  glycerol.  The  concentration 
is  hence  carried  to  a  certain  point 
FIG.  172.  in  an  apparatus  (Fig.  172  shows  the 

Droux  apparatus  and  Fig.  173  that 

of  Morane),  fitted  with  rotating  coils  or  hollow  discs,  in  which  steam  under  pressure  circu- 
lates. The  apparatus  is  covered  in  and  the  steam  from  the  solution  .issues  rapidly  through 
a  tube  communicating  with  an  aspirator.  When  the  density  reaches  18°  to  20°  Be.  the 
solution  is  decanted  or  filtered  and  then  further  concentrated  in  a  vacuum  to  27°  to  28°  Be. 

In  some  cases  the  glycerol  thus  obtained,  while  still  boiling,  is  decolorised  by  adding 
animal  charcoal  and  filtering  through  a  filter-press.  This  glycerol  always  contains  a  small 
quantity  of  dissolved  salts.  To  purify  it,  its  temperature  is  raised  to  110°  to  120°  by  means 
of  superheated  steam,  the  acids  or  more  volatile  products  being  thus  eliminated.  It  is 
then  distilled  with  superheated  steam  at  170°  to  180°,  at  which  temperature  all  the 
pure  glycerol  passes  over.  This  is  rectified 
in  one  apparatus  to  22°  Be.  and  in  a 
second,  under  diminished  pressure  and  wit  h 
superheated  steam,  to  28°  Be.,  at  wh:'ch  . 
concentration  almost  all  the  salt  separate' . 
The  vacuum  distillation  is  sometiirto 
effected  by  a  triple-effect  apparatus  (Pick 
type,  see  vol.  i,  p.  453  ;  also  section  c  n 
Sugar),  with  which  it  is  easy  to  remove 
the  salt  as  it  separates  without  interrupt- 
ing the  distillation. 

These  forms  of  apparatus  for  purifica- 
tion and  distillation  are  named  after  their 
inventors  (Hagemann,  Scott,  Jobbins,  van  Ruymbeke,  Lehmann,  Heckmann,  &c.). 

The  Heckmann  process  consists  in  distilling  the  aqueous  glycerine,  already  concentrated 
to  beyond  20°  Be.,  in  a  boiler,  A  (Fig.  174),  into  which  steam  superheated  to  200°  to 
220°  and  under  half  an  atmosphere  pressure  is  passed  by  means  of  a  perforated  coil.  In 
order  to  prevent  the  scum  being  carried  over  with  the  steam  and  glycerol,  a  perforated 
disc,  a,  fitted  with  a  vent-pipe  is  fixed  two-thirds  of  the  way  up  the  boiler.  The  vapours 
issue  by  the  pipe  B,  and  are  condensed  in  the  reservoir,  C,  which  is  heated  to  80°  to  90° 
with  indirect  steam  circulating  in  the  jacketed  bottom,  D.  Above  the  reservoir  is  a 
rectifying  column,  with  a  dephlegmator,  K,  similar  to,  but. much  lower  than,  that  used  for 
the  rectification  of  alcohol  (see  p.  136). 

During  the  distillation,  a  slight  vacuum  is  maintained  in  the  whole  apparatus  by  means 
of  a  suction  pump,  V,  so  that  principally  water-vapour  and  only  a  little  glycerol  are  evolved 
from  the  reservoir,  C.  The  glycerol  vapour  separates  in  the  column  and  returns  to  the 
reservoir,  whilst  the  condenser,  M ,  condenses  only  the  water-vapour,  which  is  controlled 


FIG.  173. 


PURIFICATION    OF    GLYCEROL 


187 


by  its  density,  colour,  and  taste  in  the  test-glass,  N,  and  is  then  collected  in  the  tank,  0. 
In  C  the  glycerol  finally  reaches  a  concentration  of  95  to  99  per  cent. 

The  rectifying  column  is  sometimes  replaced  by  a  series  of  communicating,  vertical 
copper  tubes  (Fig.  175)  which  fractionally  condense  the  glycerol-  and  water-vapours  from 
the  boiler,  B  (heated  partly  by  d:rect  fire),  into  which  passes  steam  from  v,  superheated 


in  the  furnace,  T.  By  means  of  the  pump,  Z,  a  vacuum  is  maintained  in  the  whole  apparatus, 
so  that,  as  the  distillation  proceeds,  fresh  glycerine  from  the  reservoir,  A,  can  be  drawn 
into  the  boiler.  In  the  first  cylinder  or  condensing  tube,  which  soon  reaches  a  temperature 
of  100°,  almost  pure  glycerol  separates,  whilst  in  the  succeeding  tubes,  cooled  only  by  the 
surrounding  air,  more  and  more  dilute  glycerine  and  finally  water  separate.  Below  each 
tube  is  a  horizontal  cylinder,  these  serving  to  collect  the  glycerols  of  different  concen- 
trations, some  of  which  are  subjected  to  redistillation.  In  this  way  is  obtained  the  best 
dynamite,  glycerine,  which  must  have  a  specific  gravity  of  1-263  (98  to  99  per  cent.),  and 
should  not  contain  lime,  sulphuric  acid,  chlorine,  or  arsenic. 

The  final  decoloration  may  also  be  effected  by  sodium  hydrosulphite.     Very  pure 


FIG.  175. 

glycerol  has  been  obtained  by  maintaining  it  at  0°  for  some  time  and  then  inducing  crystal- 
lisation by  a  few  pure  crystals  obtained  separately  by  cooling  to  —  40°  (Kraut's  process). 
The  degree  of  purity  is  increased  by  a  second  crystallisation. 

Purification  by  an  osmotic  process  has  also  been  attempted  but  with  unsatisfactory 
results. 

During  the  last  few  years  the  glycerine  liquids  from  the  biological  or  catalytic  decom- 
position of  fats  (see  section  on  Fats)  have  also  been  worked  up  :  they  are  first  neutralised 
or,  better,  rendered  slightly  alkaline  with  milk  of  lime  and,  after  being  left  for  some  time, 
the  liquid  is  decanted  or  filtered  off,  concentrated  to  15°  Be.  in  vacuo,  again  allowed  to 
stand  to  deposit  a  further  quantity  of  lime,  decolorised  by  passing  through  a  carbon  filter 
and  again  concentrated  to  28°  Be. 

Various  attempts  have  also  been  made  to  recover  the  glycerine  from  the  waste  liquors 
from  the  manufacture  of  alcohol,  but  as  yet  without  much  success  (Ger.  Pats.  114,492, 


188  ORGANIC    CHEMISTRY 

125,788,  129,578,  141,703,  and  147,558).     Separation  of  glycerine   by  dialysis  does  not 
give  good  results. 

STATISTICS  AND  PRICES.  In  1890,  the  world's  production  of  crude  glycerine 
amounted  to  26,000  tons  from  candle  factories  and  14,000  tons  from  soap  factories,  the 
amounts  due  to  the  principal  nations  being  :  France,  6000  tons  (candles),  3500  tons  (soap) ; 
Germany,  3000  and  2000  ;  England,  1200  and  5500  ;  Italy,  180,  &c. 

In  1900  the  production  rose  to  80,000  tons  (equally  divided  between  soap  and  candle 
factories)  and  Germany,  with  a  production  of  about  10,000  tons,  exported  2730  tons  (value 
about  £140,000)  in  1900  and  1580  tons  in  1909,  against  importations  of  5373  tons  in  1908 
and  3530  tons  in  1909.  In  1890  France  exported  3856  tons  (value  £156,000),  in  1900  about 
7450  tons  (value  £308,000),  and  in  1909  as  much  as  7000  tons  out  of  a  total  production  of 
12,000  tons  ;  9000  tons  were  made  at  Marseilles,  where  the  most  important  refinery  produces 
more  than  2000  tons  per  annum.  The  French  exportation  is  now  directed  especially  to 
the  United  States  (more  than  4000  tons  in  1910).  According  to  the  official  statistics  (!) 
Italy  produced  190  tons  of  distilled  glycerine  (worth  £8660)  in  1905  and  215  tons  (value 
£12,040)  in  1908  ;  the  imports  were  198  tons  in  1907  and  1908,  160  tons  in  1909  and  270 
tons  in  1910;  and  the  exports  833  tons  in  1908,  1145  tons  (worth  £59,540)  in  1909,  and 
1763  tons  (value  £126,920)  in  1910. 

In  1910  Spain  produced  2500  tons  of  glycerine  and  exported  893  tons.  In  1905  the 
United  States  produced  23,000  tons  (£1,040,000),  of  which  13,500  tons  were  obtained  from 
soap-works  ;  the  imports  amounted  to  16,000  tons  in  1909  and  to  more  than  20,000  tons  in 
1910.  England  exported  10,500  tons  (one-half  in  the  crude  state)  in  1909  and  about  12,500 
tons  (£1,040,000)  in  1910  ;  in  1911  the  output  was  16,000  tons,  one-half  of  which  was  refined. 
Two  main  qualities  of  glycerine  are  distinguished  :  *•  (a)  Crude  glycerine  from  the 
candle  or  soap  works  ;  (b)  Refined  glycerine,  which  is  subdivided  into  :  pale,  white,  for 
dynamite,  and  chemically  pure. 

In  1905-1909  the  price  of  No.  II  dark  brown  crude  glycerine  at  24°  Be.  was  30s.  6d.  per 
quintal,  and  at  28°  Be.  36s.  per  quintal  ;  for  the  light  brown  quality,  46s.  6d.  per  quintal 
at  28°  Be.,  and  for  the  pale  at  28°  Be.  £4.  Yellow  refined  at  28°  Be.  cost  93s.  ; 
white  refined  No.  I,  96s.  at  28°  Be.  and  108s.  at  30°  Be.  ;  free  from  lime  for  soap, 
£5  at  28°  and  108s.  at  30°  Be.  Finally  the  purest  double  distilled  glycerine  for  nitro- 
glycerine at  31°  Be.  cost  £6  per  quintal.  At  the  beginning  of  1910  these  prices  were 
increased  by  25  per  cent,  and  towards  the  end  of  1910  by  50  per  cent,  or  even  70  per  cent. 
At  the  beginning  of  1911  they  were  still  higher  mainly  owing  to  the  large  amount  required 
in  North  America  for  making  dynamite  for  the  Panama  Canal  and  other  public  works. 

C.  TETRA-  AND  POLY-HYDRIC  ALCOHOLS 

These  are  usually  sweet,  crystalline  substances  which  decompose  near  their 
boiling-points.  They  are  distinguished  one  from  another  by  the  crystalline 
forms  of  their  phenylhydrazine  derivatives. 

1  Tests  for  Glycerine :  the  crude,  pale  at  28°  Be.,  contains  0-5  per  cent,  of  ash  and  is  not  rendered 
turbid  by  HC1,  and  only  faintly  so  by  lead  acetate ;  that  separated  from  sulphuric  acid  saponifications,  besides 
having  a  bad  smell  and  taste,  gives  3  to  5  per  cent,  of  ash  and  84  to  86  per  cent,  of  glycerine,  a  turbidity  (fatty 
acWs)  or  precipitate  being  produced  by  HC1  or  lead  acetate.  The  glycerine  to  be  used  for  nitroglycerine  and 
dynamite  is  subjected  to  the  following  tests  :  the  water  is  calculated  from  the  loss  in  weight  of  20  grms.  heated 
for  10  hours  at  100°  and  for  a  few  hours  at  a  slightly  higher  temperature.  Five  grammes,  after  being  heated  in  a 
platinum  dish  at  180°  until  no  further  evolution  of  vapour  takes  place,  are  weighed,  and  should  then  undergo  no 
further  diminution  in  weight  when  again  heated  for  a  short  time  ;  it  is  then  ashed  in  the  usual  way  and  the  ash 
tested  for  metals  and  salts.  Glycerine  for  nitroglycerine  should  have  been  distilled  at  least  once,  should  not 
contain  sugar  or  fatty  acids,  should  have  a  neutral  reaction  and  should  contain  no  lead,  calcium,  or  other  metals  or 
foreign  metalloids ;  only  traces  of  Cl,  As,  and  Fe  are  allowed  :  the  specific  gravity  should  exceed  1-262.  The  purest 
glycerine  (puriss.)  does  not  contain  more  than  0-03  per  cent,  of  ash  and  as  much  organic  impurity,  and  for  dynamite 
these  two  should  not  exceed  0-25  per  cent.  Oxalic  acid  is  detected  by  neutralising  with  ammonia,  acidifying 
with  acetic  acid  and  precipitating  with  CaCl,.  The  glycerine  content  is  determined  from  the  density  (the  air- 
bubbles  being  removed  by  heating),  use  being  made  of  the  Table  on  p.  184  ;  in  Germany  a  special  Berthelot  scale  is 
used  indicating  one  degree  higher  than  the  Baume'  scale,  26°  Berthelot  corresponding  with  a  specific  gravity  of  1-210, 
28°  with  1-230,  29°  with  1-240,  and  30°  with  1-250.  The  index  of  refraction  is  determined  at  the  temperature 
indicated  in  the  Table.  In  many  cases  the  glycerine  is  estimated  directly  by  means  of  the  acetyl  number  (see 
(succeeding  Note),  but  the  method  in  which  the  glycerine  is  oxidised  by  hot  permanganate  and  potassium  hydroxide 
to  oxalic  acid  and  the  latter  precipitated  as  calcium  oxalate  should  be  rejected.  The  fairly  rapid  Hehner- 
Richardson-Jaffe  method  is  used  more  successfully  :  the  glycerine  is  destroyed  with  dichromate  and  sulphuric 
acid,  and  the  amount  of  dichromate  used  up  (or,  according  to  Gautter  and  Schulze,  how  much  CO8  is  evolved) 
measured  by  titration  with  sodium  thiosulphate,  or,  better,  ferrous  ammonium  sulphate.  This  method  assumes 
that  the  glycerine  contains  no  chloride,  nitrate,  or  extraneous  organic  matter ;  these  impurities  can,  in  any  case, 
be  eliminated  by  means  of  silver  oxide  (chlorides),  and  lead  acetate  and  calcium  carbonate  (organic  matter), 
decoloration  being  then  effected  by  heating  with  animal  charcoal. 


POLYHYDRIC    ALCOHOLS  189 

They  do  not  reduce  Fehling's  solution  and  hence  differ  from  the  carbo- 
hydrates, but  are  derived  from  these  by  reduction. 

The  valency  of  an  alcohol  is  given  by  the  number  of  alcoholic  hydroxyls  it 
contains,  and  hence  by  the  number  of  monobasic  acid  residues  it  can  fix  to  form 
a  neutral  ester.  Acetic  anhydride  serves  well  for  this  purpose,  the  hydrogen 
atoms  of  the  hydroxyl  groups  being  replaced  each  by  an  acetyl  group,  CH3  •  CO : 1 

C6H8(OH)6  +  6(CH3-CO)2O  =  6CH3-COOH  +  C6H8(0-CO-CH3)6. 

Mannitol  Hexacetylmannitol 

Esters  can  also  be  prepared  with  bromobenzoic  acid,  the  bromine  in  the 
resultant  product  being  determined  and  the  number  of  hydroxyl  groups 
deduced  therefrom.  Well-defined  compounds  are  also  formed  with  benzal- 
dehyde  and  are  employed  in  separating  the  constituents  of  different  mixtures. 

ERYTHRITOL(Butantetrol),OH-CH2-CH(OH)-CH(OH)-CH2-OH,  is  found  in  nature 

in  the  free  state  in  Protococcus  vulgaris,  and  as  orsellinic  ester  (erythrin)  in  lichens  and  algae. 
It  forms  crystals,  m.pt.  112°,  b.pt.  330°,  and  is  slightly  soluble  in  alcohol  and  insoluble  in 
ether.  It  is  obtained  by  decomposing  rf-glucose  or  synthetically  from  crotonylene,  and  its 
constitution  is  deduced  from  the  fact  that  it  yields  secondary  normal  butyl  iodide  on 
reduction  with  hydriodic  acid.  A  similar  reaction  takes  place  with  the  higher  polyvalent 
alcohols  with  normal  chains.  The  four  possible  stereoisomerides  are  known,  the  most 
common  being  the  one  now  described  which  is  optically  inactive. 

PENTA-ERYTHRITOL  has  the  formula  C(CH2-OH)4,  and  melts  at  253°. 

ARABITOL,  C5H7(OH)5  (Pentahydroxypentane),  crystallises  in  acicular  prisms, 
m.pt.  102°,  has  a  sweet  taste  and  is  formed  by  reducing  the  corresponding  sugar,  arabi- 
nose,  with  nascent  hydrogen  ;  reduction  of  xylose  similarly  yields  xylitol. 

MANNITOL,  C6H8(OH)6  (Hexanhexol),  occurs  abundantly  in  the  vegetable  kingdom 
(the  larch,  sugar-cane,  Agaricus  integer  containing  20  per  cent,  of  mannitol,  &c.),  but  espe- 
cially in  the  manna  ash  (Fraxinus  ornus),  the  dried  juice  of  which  forms  ordinary  wanna;2 

1  In  this  way  is  determined  the  so-called  acetyl  number  which  is  so  widely  used  in  the  analysis  of  fats  and  oils. 
With  these,  the  test  is  made  on  the  insoluble  fatty  acids  obtained  by  saponifying  40  to  50  grms.  of  the  fat  with 
40  c.c.  of  KOH  solution  (sp.  gr.  1-4)  and  40  c.c.  of  alcohol,  this  mixture  being  heated  for  half  an  hour  on  the 
water-bath,  after  which  it  is  diluted  with  a  litre  of  water  and  boiled  for  three-quarters  of  an  hour  in  an  open 
beaker  to  eliminate  the  alcohol.  The  liquid  is  acidified  with  sulphuric  acid  and  boiled  until  the  fatty  acids  separate 
in  a  transparent  condition,  when  they  are  removed  with  a  tapped  funnel,  washed  twice  with  hot  water  and  dried  in 
an  oven  at  100°  to  105".  To  determine  the  acetyl  number,  a  few  grammes  of  the  substance  containing  the  hydroxyl 
groups  (or  about  20  grms.  of  hydroxylic  fatty  acids)  are  treated  with  two  or  three  times  their  volume  of  acetic 
anhydride  and  a  few  drops  of  concentrated  sulphuric  acid  (formerly  in  place  of  the  sulphuric  acid  fused  sodium 
t  acetate,  in  quantity  equal  to  the  acetic  anhydride,  was  used,  the  mixture  being  heated  for  two  hours  on  the  water- 
bath  in  a  reflux  apparatus).  The  mass  heats  spontaneously,  and  in  a  few  minutes  acetylation  takes  place ;  it 
is  then  allowed  to  cool,  calcium  carbonate  being  added  to  precipitate  the  sulphuric  acid  and  the  liquid  filtered. 
The  filtrate  is  distilled  or  evaporated  to  separate  the  acetate  in  a  liquid  or  crystalline  condition. 

In  the  case  of  the  fatty  acids,  the  filtrate  is,  however,  diluted  with  600  to  700  c.c.  of  water  and  boiled  for 
30  to  40  minutes  in  an  open  beaker  to  remove  the  acetic  acid,  a  slow  current  of  CO2  being  passed  into  the  bottom 
of  the  liquid  to  prevent  bumping.  The  supernatant  liquid  is  then  siphoned  from  the  acetyl  compound,  which  is 
boiled  with  another  500  c.c.  of  water  and  so  on,  this  operation  being  repeated  until  the  washing  water  no  longer 
has  an  acid  reaction.  The  acetylated  derivative  is  then  collected  on  a  filter,  washed  and  dried  in  an  oven. 

Of  this  compound,  0-5  to  1  grm.  is  dissolved  in  pure,  neutral  alcohol,  and  the  solution  heated  for  45  minutes  on 
the  water-bath  in  a  150  c.c.  flask  with  a  definite  volume  (30  to  50  c;c.)  of  seminormal  alcoholic  potash.  When 
cold,  the  liquid  is  titrated  with  seminormal  hydrochloric  acid  in  presence  of  phenolphthalein  to  determine  the 
excess  of  alkali  which  has  not  taken  part  in  the  splitting  of  the  acetic  ester. 

One  hydroxyl  group  for  every  grm.-mol.  of  substance  corresponds  with  56  grms.  of  KOH  fixed.  With  the 
fatty  acids,  which  contain  also  the  carboxyl  group,  the  procedure  is  as  follows  :  3  to  4  grms.  of  the  acetyl  derivative 
are  dissolved  in  pure,  neutral  alcohol  and  the  acidity  of  the  carboxyl  group  (acetyl  acid  value)  determined  by 
titration  with  N/2-alkali ;  the  neutralised  liquid  is  boiled  with  a  known  volume  in  excess  of  N/2-alcoholic  potash 
for  a  short  time  on  the  water-bath,  retitration  with  N/2-hydrochloric  acid  given  the  excess  of  alkali  not  combined 
with  acetyl  groups.  The  alkali  combined  (after  the  first  neutralisation),  expressed  in  mgrms.  of  KOH  per  1  grm. 
of  acetyl  compound  gives  the  acetyl  number.  With  the  fatty  acids  the  sum  of  the  acetylated  acid  number  and 
the  acetyl  number  is  termed  the  acetyl  saponiftcation  value.  From  the  acetyl  number  (N),  the  molecular  magnitude 

56,100 
(M ),  of  the  alcoholic  substance  can  be  deduced  by  the  formula  :  M  —  — —  -  -  42. 

1  Manna  is  extracted  more  particularly  from  Fraxinus  ornus  and  Fraxinus  rotundifolia,  which  are  widespread 
in  Sicily  and  Calabria  and  from  which  it  readily  flows  through  long  vertical  incisions  made  in  summer  and  autumn. 
It  seems  to  occur  in  the  rising  sap  before  this  reaches  the  leaves  and  is  thought  by  some  to  be  produced  by  enzyme 
actions.  Crude,  commercial  manna  contains  12  to  13  per  cent,  of  water,  10  to  15  per  cent,  of  sugar,  32  to  42 
per  cent,  of  mannitol,  40  to  41  per  cent,  of  mucilaginous  substances,  organic  acids  and  nitrogenous  matter,  1  to  2 
per  cent,  of  insoluble  substances  and  1  to  2  per  cent,  of  ash.  Australian  manna  (from  Myoporum  platycorpum) 
contains  as  much  as  90  per  cent,  of  mannitol. 

The  manna  tree  grows  in  fertile,  rocky  soiljind  is  incised  iu  its  tenth  year  and  in  the  following  10  or  15  years.    It 


190  ORGANIC    CHEMISTRY 

from  this  alcohol  extracts  pure  mannitol,  which  can  be  decolorised  by  repeated  treatment 
with  charcoal.  In  manna  it  was  discovered  by  Proust  in  1806.  It  is  obtained  synthe- 
tically by  reducing  fructose  or  glucose  :  C6H12O6  +  H2  =  C6H14O6. 

The  optically  inactive,  laevo-  and  dextro-rotatory  forms  are  known,  the  last  being  the 
most  common  ;  the  optical  activity  is  slight  but  is  rendered  more  apparent  by  the  addition 
of  borax.  When  heated  it  loses  water  giving  anhydrides  (mannitan,  C6H1205,  and  mannide, 
C6H10O4)  ;  in  a  vacuum  it  distils  unchanged. 

One  hundred  parts  of  water  dissolve  16  parts  by  weight  of  mannitol  at  16°. 

From  alcohol  it  crystallises  in  triclinic  acicular  prisms  and  from  water  in  large  rhombic 
prisms  having  a  sweet  taste  and  melting  at  160°. 

Stereoisomeric  with  mannitol  is  DULCITOL,  C6H8(OH)6,  which  occurs  in  a  number 
of  plants  and  in  Madagascar  manna.  It  forms  sweet,  monoclinic  prisms,  m.pt.  188°,  and  is 
almost  insoluble  in  water,  even  in  the  hot.  Synthetically  it  can  be  prepared  by  reducing 
lactose  and  galactose.  It  is  optically  inactive  even  in  presence  of  borax. 

Another  stereoisomeride  of  mannitol  is  sorbitol,  which  melts  at  104°  to  109°,  or  at  75° 
when  crystallised  with  1H2O.  It  can  be  obtained  synthetically  by  reducing  d-glucose 
or  ^-fructose.  In  presence  of  borax  it  shows  a  slight  dextro-rotation. 

Other  stereoisomerides  are  TALITOL  and  IDITOL  ;  these  isomerides  are  usually 
separated  by  means  of  the  acetals  they  form  with  benzaldehyde. 

DD.  DERIVATIVES   OF  THE    ALCOHOLS 

A.  DERIVATIVES    OF    MONOHYDRIC    ALCOHOLS 
i.  ETHERS 

These  are  generally  formed  by  eliminating  1  mol.  of  water  (for  example, 
by  concentrated  sulphuric  acid  or  by  hot  hydrochloric  acid)  from  2  mols.  of 
alcohol,  which  condense  to  form  1  mol.  of  ether  in  the  same  way  as  2  mols.  of 
an  acid  give  an  anhydride  : 

C2H5  •  OH    _  TT  o    ,      C2H5\O 
CH3-OH  CH3/L 

Ethers  are  not  formed  by  secondary  or  tertiary  alcohols.  The  first  term  of  the 
series,  methyl  ether,  is  gaseous,  and  the  succeeding  terms  become  liquid  and 
then  solid  as  the  molecular  weight  increases,  the  ethereal  odour  of  the  first 
members  being  gradually  lost. 

is  then  cut  back  and  the  new  branches  incised  in  the  seventh  year  and  the  succeeding  10  or  15  years.  It  is 
then  again  cut  back,  this  procedure  being  continued  for  80  or  100  years.  JOne  hectare  with  4500  trees  gives  as 
much  as  100  kilos  of  manna  per  annum.  It  is  harvested  in  August  and  September. 

Manna  is  used  as  a  mild  purgative  for  children.  It  has  a  sweetish  taste,  is  soluble  in' water  or  alcohol,  and, 
besides  mannitol,  contains  various  sugars  such  as  stachyose  and  mannatrwse. 

To  extract  the  mannitol,  the  crude  manna  is  dissolved  in  half  its  weight  of  water  containing  white  of  egg. 
The  solution  is  boiled  for  a  few  minutes  and  strained,  and  the  filtered  mass,  solidified  by  cooling,  pressed  in  bags, 
or,  better,  centrifuged  and  washed  at  the  same  time  with  a  large  quantity  of  cold  water.  It  is  redissolved  in 
water  and  the  solution  boiled  with  animal  charcoal,  filtered  under  pressure,  crystallised  and  centrifuged.  The 
mother-liquors  are  used  to  dissolve  fresh  quantities  of  the  crude  manna.  The  fineness  of  the  crystals  depends  on 
the  concentration  and  on  the  temperature  of  the  air  ;  in  some  cases  the  crystallisation  is  disturbed  by  continually 
stirring  the  mass. 

Sometimes  the  manna  solutions  are  first  subjected  to  lactic  fermentation,  by  which  means  considerable  quantitie 
of  calcium  lactate  are  obtained  ;  the  mannitol  is  then  extracted  from  the  residual  liquors. 

Mannitol  is  not  fermented  by  beer-yeast,  but  with  chalk  and  sour  cheese  it  gives  a  considerable  amount  of 
alcohol,  volatile  acids,  carbon  dioxide,  and  hydrogen.  When  cautiously  oxidised  with  nitric  acid,  it  forms 
d-mannose  and  d-fructose,  whilst  with  the  Sorbose  bacterium  it  gives  only  the  latter  sugar. 

Mannitol  has  a  slight  laevo-rotation  (—  0-15°)  which  is  increased  by  alkali  and  changed  in  sign  by  borax.  It 
dissolves  in  6-5  parts  of  water  at  18°,  in  80  parts  of  60  per  cent,  alcohol  at  15°,  or  in  1400  parts  of  absolute  alcohol ; 
it  is  insoluble  in  ether. 

Manna  in  casks  costs  3s.  to  5s.  per  kilo  ;  assorted,  1«.  7d. ;  in  lumps,  9i</v  The  average. price  of  manna  (from 
Cefalu)  on  the  Genoa  Exchange  has  gradually  risen  from  about  2s.  Id.  in  1901  to  about  4s.  7d.  in  1910,  when  pure 
crystallised  mannitol  cost  7«.  to  10s.  per  kilo.  The  best  qualities  of  manna  are  those  from  Cefalu,  Gerace,  and 
Smauro  ;  of  inferior  quality  is  the  Capaci  variety,  which  is  produced  also  at  Cinisi,  Belmonte,  Castellamare  del 
Golfo,  &c.  The  Sicilian  production,  which  represents  almost  the  entire  production  of  the  world,  was  about  3600 
quintals  in  1900,  7000  in  1902,  5100  in  1905,  6900  in  1906,  4550  in  1908,  and  less  than  3000  (owing  to  the  bad 
season)  in  1910.  The  exports  were  2320  quintals  in  1907,  1776  in  1908,  2582  (value?  £36,000)  in  1909.  About 
8000  quintals  per  annum  are  treated  for  the  extraction  of  mannitol — about  1000  quintals,  of  wljieh  onjy  one-third 
pr  one-fourth  IB  consumed  in  Italy, 


ETHERS  191 

The  empirical  formulae  of  the  ethers  show  them  to  be  isomeric  with  the 
alcohols,  but  their  constitution  results  from  Williamson's  synthesis,  according 
to  which  they  are  obtained  by  the  action  of  a  sodium  alkoxide  on  the  halogen 
derivative  of  an  alcohol  : 

CwH2w+1ONa  +  IC,,H2,,+1  =  Nal  +  C^^.O-aH^ 

If  in  the  sodium  alkoxide  the  sodium  were  not  united  to  the  oxygen  but 
directly  with  carbon,  this  reaction  would  give  an  alcohol  and  not  an  ether  ; 
indeed,  if  sodium  ethoxide  were  NaCH2  •  CH2-  OH,  it  would,  with  methyl  iodide, 
give  propyl  alcohol  :  CH3I  +  NaCH2  •  CH2  •  OH  =  Nal  +  CH3  •  CH2  •  CH2  •  OH. 
But,  in  reality,  methyl  ethyl  ether  and  not  propyl  alcohol  is  obtained,  this 
proving  the  constitution  of  the  metallic  alkoxides  and  of  the  ethers,  in  which 
all  the  hydrogen  atoms  are  equivalent. 

The  interaction  of  silver  oxide  with  alkyl  halides  (see  p.  17)  also  leads  to 
the  formation  of  ethers  :  2C2H5I  +  Ag20  =  2AgI  +  C2H5-0-C2H5. 

If  the  alkyl  radicles  of  an  ether  are  similar,  it  is  a  simple  ether,  e.g.  ethyl  ether, 
C2H5-0-C2H5,  whereas  if  the  radicles  are  different,  the  result  is  a  mixed  ether, 
e.g.  methyl  ethyl  ether,  C2H5-  0-  CH3. 

Sabatier,  Senderens,  and  Mailhe  (1909-1910)  obtained  ethers  of  different  types,  some 
mixed  and  of  the  aromatic  series,  by  passing  the  superheated  vapours  of  alcohols  (250°  to 
350°)  over  metallic  oxides  (titanium,  thorium,  tungsten,  or,  best  of  all,  aluminium).  The 
yield  is  quantitative,  no  ethylene  hydrocarbons  being  formed  as  is  the  case  when  sulphuric 
acid  is  used.  The  process  is  continuous  and  pseudo-catalytic,  unstable  aluminium  alkoxide 
being  formed  as  an  intermediate  product  :  (C2H50)6A12  =  A1203  +  3(C2H5)20.  In  some 
cases  this  general  method  can  be  advantageously  employed  industrially. 

When  the  ethers  are  prepared  from  the  alkoxides  in  alcoholic  solution  there  should  not 
be  an  excess  of  water  (more  than  50  per  cent.)  present,  otherwise  the  alkoxide  decomposes 
into  alcohol  and  alkali  hydroxide  and  no  ether  is  formed. 

Also  when  sulphuric  acid  (or  HC1)  is  used  in  the  preparation,  an  equilibrium  sets  in 
between  the  reacting  products  —  intermediate  and  final  —  this  equilibrium  being  regulated 
by  the  mass  law,  so  that  a  certain  yield  cannot  be  exceeded  except  by  eliminating  some 
of  the  new  products  formed  (e.g.  by  gradually  distilling  the  ether  ;  see  later)  : 


(a)  C2H5.OH  +  H2S04  =  C2H5.S04H  +  H2O. 

Ethylsulphuric  acid. 

(b)  C2H5.S04H  +  C2H5-OH  =  H2S04+  C2H5.O.C2H6. 

The  sulphuric  acid  is  regenerated  and  can  transform  fresh  alcohol  into  ether  ;  theoreti- 
cally, then,  the  initial  quantity  of  sulphuric  acid  should  be  sufficient  to  transform  an 
infinite  quantity  of  alcohol  into  ether,  but  in  practice  it  is  necessary  to  add  a  small  quantity 
of  the  acid  each  time,  as  some  of  it  is  used  up  in  the  formation  of  sulphur  dioxide,  ethylene, 
and  sulphonated  products.  The  process  is  thus  not  practically  continuous  in  the  strict 
sense  of  the  term,  since  in  the  phase  (a)  water  is  formed,  and  this  cannot  all  be  eliminated 
by  distillation,  but  after  a  time  accumulates  in  such  quantity  as  to  establish  an  equilibrium 
between  the  formation  of  ether  and  the  decomposition  of  ethylsulphuric  acid,  alcohol  and 
sulphuric  acid  thus  being  regenerated. 

The  ethers  are  very  stable  and  scarcely  react  in  the  cold  with  alkalis, 
dilute  acids,  sodium  or  phosphorus  pentachloride.  When  superheated  with 
water  and  a  little  mineral  acid,  ether  is  converted  back  into  alcohol  : 

C2H5-0-C2H5  +  H2S04  =  CaH5-OH  +  C,H6-S04H 

and  the  same  change  occurs  on  saturating  ether  at  0°  with  gaseous  hydrogen 
iodide  : 

(C2H5)20  +  HI  -  C2H5-OH  +  C2H5I, 

the  hydrogen  iodide  subsequently  converting  £he  alcohol  also  into  gthyl  iodide  ; 


192  ORGANIC    CHEMISTRY 

when  mixed  ethers  are  taken,  the  iodine  unites  preferably  with  the  radicle 
containing  the  lesser  amount  of  carbon.  PC15  also  decomposes  the  ethers  on 
heating  : 

(C2H5)20  +  PC15  =  POC13  +  2C2H5C1. 

The  halogens  give  substitution  products  just  as  they  do  with  the  hydro- 
carbons, but  nitric  acid  gives  oxidation  products. 

In  the  ethers  are  reproduced  all  the  cases  of  isomerism  presented  by  the 
alkyl  groups  from  which  they  are  derived,  there  being  consequently  numerous 
cases  of  metamerism  (see  p.  17),  e.g.  methyl  amyl  ether,  CH3-OC5HU,  is 
metameric  with  ethyl  butyl  ether,  C2H5-0-C4H9,  and  also  with  dipropyl 
ether,  C3H7-  0-  C3H7,  all  these  having  the  empirical  formula  C6H140. 

METHYL  ETHER,  CH3-O-CH3  (Methoxymethane),  is  a  gas,  but  liquefies  at  —23°, 
and  then  has  a  sp.  gr.  1  -617  ;  it  resembles  ethyl  ether.  One  volume  of  water  dissolves  37  vols. 
of  the  gas,  and  1  vol.  of  sulphuric  acid  600  vols.  of  it. 

ETHYL  ETHER,  C4H10O  (Ethokyethane),  C2H5-0-C2H5.  This  was  pre- 
pared for  the  first  time  in  the  sixteenth  century  by  Valerius  Cordus  from  spirit 
of  wine.  It  was  formerly  thought  to  contain  sulphur,  and  was  therefore  given 
the  name  sulphuric  ether,  still  in  use.  Its  true  composition  was  established  by 
Saussure  and  by  Gay-Lussac  (1807  and  1815)  and  the  constitution  was  enun- 
ciated by  Laurent  and  Gerhardt  and  confirmed  experimentally  by  Williamson. 
It  was  thought  for  a  long  time  that  the  sulphuric  acid  employed  in  the  manu- 
facture of  ether  possessed  the  sole  function  of  fixing  and  subtracting  water 
from  the  alcohol.  Since,  however,  it  was  found  that  water  formed  in  the 
reaction  always  distilled  with  the  ether,  this  hypothesis  became  invalid,  and 
Berzelius  and  Mitscherlich  attributed  the  reaction  of  etherification  to  the 
catalytic  action  of  the  sulphuric  acid. 

Later  on  Liebig  maintained  that  the  ether  is  formed  by  the  direct  decom- 
position of  the  intermediate  product  (ethylsulphuric  acid)  with  separation, 
in  the  hot,  of  S03.  Graham,  however,  succeeded  in  showing  that  ethyl- 
sulphuric  acid,  when  heated  alone  at  140°,  does  not  give  ether,  but  that  the 
latter  is  formed  in  presence  of  alcohol.  •  In  1851  Williamson  gave  the  true 
explanation  of  the  process  by  dividing  the  reaction  into  two  phases  (a  and  b,  see 
preceding  page) ;  the  secondary  products,  explaining  the  loss  of  sulphuric  acid 
(see  above],  were  discovered  later. 

Etherification  takes  place  also  if  the  sulphuric  acid  is  replaced  by  phos- 
phoric, arsenic,  boric,  or  hydrochloric  acid. 

Sulphur  dioxide,  which  is  formed  and  lost  in  this  process,  is  not  produced 
if  the  sulphuric  acid  is  replaced  by  an  aromatic  sulphonic  acid,  for  instance, 
C6H5-S03H,  or  the  corresponding  chloride,  C6H6-S02C1  (Kraft  and  Ross, 
Ger.  Pat.  691,115),  the  temperature  of  the  reaction  being  then  slightly  above 
100°: 

(a)  C2H5-OH  +  C6H5-S03H  =  H20  +  C6H5-S02-OC2H5. 

(b)  C2H5-OH  +  C6H5.S02-OC2H5  =  (C2H5)20  +  C6H5-S03H. 

J.  W.  Harris's  process  (U.S.  Pat.  711,656)  may  also  have  an  industrial 
future  ;  in  this,  acetylene  and  hydrogen  give  ethylene  which,  with  H2S04, 
forms  ethylsulphuric  acid,  the  latter  then  forming  ether  under  the  action  of 
water. 

Good  results  are  also  given  by  the  use  of  methionic  acid,  CH2(S03H)2, 
proposed  by  Schroeter  and  Sondag  in  1908  ;  with  this  acid  all  the  higher  ethers 
can  be  prepared  and  10  per  cent,  of  the  acid  (on  the  weight  of  alcohol)  is  sufficient 
to  give  a  continuous  distillation  of  ether. 

Senderens  transforms  alcohol  vapour  quantitatively  into  ether  by  passing 
it  over  calcined,  precipitated  alumina  heated  exactly  to  260°  (see  p.  191). 


PROPERTIES    OF    ETHER 


193 


PROPERTIES.  Ether  is  a  colourless,  very  mobile  liquid  boiling  at  34-9°, 
solidifying  at  -129°,  and  melting  at  -113°  ;  it  has  the  sp.  gr.  0-7196  at  15°. 
At  120°  its  vapour  pressure  is  10  atmos.  On  evaporation,  it  produces  intense 
cold.  It  inflames  very  readily,  but  is  not  inflammable  when  mixed  with 
35  to  50  per  cent,  of  carbon  tetrachloride.  With  air  it  forms  explosive  mixtures 
(p.  33).  It  is  obtained  anhydrous  by  distilling  over  a  little  sodium. 

J.  Meunier  (1907)  has  found  that  mixtures  of  ether  vapour  and  air  become 
inflammable  and  explosive  when  they  contain  from  75  to  200  mgrms.  of  ether 
per  litre  of  air. 

As  ether  vapour  is  much  heavier  than  air  (mol.  wt.  74),  it  tends  to  collect 
in  a  dense,  invisible  layer  on  the  floor  or  bench  and  may  cause  fire  or  explosion. 
It  is  soluble  in  concentrated  hydrochloric  acid. 

Water  dissolves  6-5  per  cent,  of  ether  at  19°,  and  ether  dissolves  about 
1-25  per  cent,  of  water  at  20°.  Aqueous 
ether  can  be  recognised  by  the  turbidity  pro- 
duced on  shaking  it  with  a  small  quantity  of 
carbon  disulphide.  It  is  moderately  soluble 
in  concentrated  sulphuric  acid  (1  vol.  H2S04 
dissolves  1-67  vol.  of  ether).  It  is  an  excellent 
solvent  for  many  organic  substances.  It 
combines  with  certain  inorganic  substances 
(chloride  of  tin,  aluminium,  phosphorus, 
antimony,  &c.)  as  ether  of  crystallisation. 

The  action  of  light  on  ether  produces  small 
quantities  of  hydrogen  peroxide,  acetaldehyde, 
acetic  acid,  and  vinyl  alcohol.  In  contact  with 
platinum  black,  ether  ignites.  When  poured 
into  a  cylinder  of  chlorine  it  explodes  and 
forms  hydrogen  chloride,  whilst  in  the  dark 
the  slow  reaction  yields  perchloroether.  Ether 
is  an  anaesthetic  and  was  used  as  such  before 
chloroform  ;  it  is  again  coming  into  use  at 
the  present  time,  as  it  is  not  very  dangerous, 
although  it  produces  certain  disturbing  effects, 
for  example,  in  the  lungs.  For  this  purpose 
it  must  be  used  in  a  highly  purified  con- 
dition. 

When  mixed  with  liquid  carbon  dioxide, 
it  lowers  the  temperature  to  79-5°  below  zero 
giving  acetaldehyde. 

INDUSTRIAL  PREPARATION  OF  ETHER.  Use  is  generally  made  of  the  con- 
tinuous process,  the  apparatus  employed  being  that  of  Boullay  or  of  Barbet  ;  9  parts  of 
concentrated  sulphuric  acid  of  66°  Be.  (free  from  nitric  and  nitrosylsulphuric  acids, 
which  would  attack  the  copper  of  the  apparatus)  and  5  parts  of  90  per  cent,  alcohol  free 
from  fusel  oil  are  taken.  Heckmann's  apparatus  for  working  on  a  small  scale  is  shown  in 
Fig.  176  :  A  is  the  alcohol  reservoir  which  feeds  the  alcohol  regularly  through  the  tap,  a, 
and  the  glass  vessel,  b,  to  the  still,  B,  containing  the  sulphuric  acid  ;  indirect  steam  under 
pressure  is  supplied  to  the  coil,  e.  The  ether  continually  distilling  over  is  condensed  in 
the  coil,  C,  immersed  in  cold  water. 

The  Barbet  apparatus  (Fig.  177)  is  used  for  the  production  of  large  quantities  of  ether, 
and  consists  of  a  vertical  cylindrical  boiler,  A,  inside  which  is  the  steam  coil,  C.  The  alcohol 
is  introduced  by  the  central  tube,  H,  whilst  another  tube  is  used  at  the  beginning  for  the 
acid  and  still  another,  of  greater  width,  allows  the  ether  vapour  to  escape  to  the  saturator 
and  the  condenser.  The  boiler  and  the  coils  are  of  copper  or  of  iron  lined  with  lead. 

First  of  all,   3500  kilos  of  sulphuric  acid  (66°  Be.)  and  1500  kilos  of  95  per  cent, 
alcohol  are  introduced  and  are  heated  to  130°  by  means  of  the  steam-coil  ;   as  the  ether 
II  13 


FIG.  176. 


It  decomposes  at  above  500C 


194 


ORGANIC    CHEMISTRY 


distils  alcohol  is  automatically  added  in  a  continuous  stream.  To  remove  the  acid  products 
carried  over  by  the  ether,  use  is  made  of  a  saturator  (Fig.  178),  which  contains  a  number  of 
plates  like  a  rectifying  column  and  down  which  flows  a  solution  of  soda. 

The  crude  ether,  distilled  and  condensed  in  the  refrigerating  coil,  contains  a  little  alcohol, 
water,  and  other  impurities  ;  to  dry  and  purify  it,  it  is  redistilled  over  calcium  chloride 
and  then  rectified  in  a  column  apparatus.  Distillation  over  sodium  wire  yields  a  very  pure 
product. 

The  premises  where  the  distilling  apparatus  is  situated  are  usually  separated  by  thick 
walls  from  the  condenser,  in  order  to  avoid  the  danger  of  fire  and  explosion.  Some  premises 
are  fitted  with  channels  and  draught-apertures  for  rapidly  dispersing  any  vapour  which 
may  find  its  way  into  the  air.  The  distilled  vapour  is  condensed  in  closed  apparatus, 
the  only  outlet  to  which  is  a  tube  opening  on  the  roof. 

If  the  temperature  of  etherification  exceeds  140°,  the  yield  diminishes,  as  a  considerable 

quantity  of  ethylene  is  then 
formed  :  C2H5  •  OH  =  H20  +  C2H4. 
On  the  other  hand,  if  the  tem- 
perature falls  below  130°,  a  large 
amount  of  alcohol  distils  without 
reacting. 

The  alcohol  for  making  ether 
is  denatured  so  as  to  be  exempt 
from  taxation,  and  in  Germany 
animal  oil  (Dippel's)  is  added, 
this  being  then  fixed  and  decom- 
posed by  the  sulphuric  acid.  In 
Italy  the  alcohol  is  denatured  with 
sulphuric  acid. 

D.  Annaratone  (Ger.  Pat. 
231,395,  1909)  obtains  increased 
yields  of  ether  by  passing  alcohol 
vapour,  superheated  to  130°,  into 


FIG.  177. 


•pIG 


a  column  filled  with  pebbles,  among  which  the  sulphuric  acid  is  circulated  or  sprayed  ; 
for  100  kilos  of  ether  only  180  kilos  of  steam  are  required  for  heating  instead  of  700 
kilos  used  in  the  old  process. 

USES  AND  PRODUCTION.  The  amount  of  ether  manufactured  in 
Germany  in  1902  was  about  2000  tons,  without  counting  that  now  made  in 
large  quantities  for  the  production  of  artificial  silk  by  the  Chardonnet-Lehner 
process. 

In  Italy  large  amounts  of  ether  were  manufactured  before  the  artificial 
silk  factories  were  closed  ;  it  is  protected  by  a  Customs  duty  of  £3  12s.  The 
importation  into  Italy  has  fallen  to  25  quintals.  In  1907,  Gulinelli's  distillery 
(Ferrara)  alone  produced  3588  quintals  of  ether.  Owing  to  the  crisis  in  the 
Italian  artificial  silk  industry,  the  production  had  fallen  considerably  in  1910. 

Ether  exempt  from  duty  is  sold  in  Germany  at  £4  per  quintal  if  its  sp.  gr. 
is  0-722,  whilst  the  price  of  the  pharmacopcsial  product,  sp.  gr.  0-720,  is  £4  10s. 
Taxed  ether,  distilled  over  sodium  and  chemically  pure,  costs  4s.  per  kilo.  In 
1909,  ether  for  artificial  silk  manufacture  cost  £2  11s.  per  quintal  in  Belgium  and 
£2  14s.  in  Austria. 

Ether  is  used  in  small  quantity  as  an  anaesthetic,  and  in  large  quantities 
in  the  manufacture  of  collodion  and  artificial  silk,  and  also  as  a  solvent  for 
numerous  organic  compounds  in  dye  and  perfume  factories.  In  Ireland  it 
is  drunk  as  a  liqueur — a  refined  form  of  alcoholism.  • 

Various  chlorinated  derivatives  of  ether  are  known. 

Also  Ethyl  Peroxide, C2H5-O-O-C2H5,  is  prepared  by  introducing  ethyl  groups  into 
hydrogen  peroxide  by  means  of  ethyl  sulphate  ;  it  is  a  liquid,  b.pt.  65°,  soluble  in  water 
and  very  readily  inflammable,  but  is  moderately  stable  towards  chemical  reagents. 

Jn  1901  Baeyer  prepared  also  the  Hydrate  of  Ethyl  Peroxide,  C2H5O  •  OH,  as  a  colourless 


MERCAPTANS  AND  SULPHIDES     195 

liquid,  which  possesses  strong  oxidising  properties,  dissolves  in  water,  boils  at  95°,  and 
forms  barium  and  other  salts. 

TESTS  FOR  ETHER.  Ether  containing  water  or  alcohol  has  a  specific  gravity  of 
0-720-0-722-0-725  or  even  0-733.  When  20  c.c.  of  ether  are  shaken  with  5  c.c.  of  water, 
the  latter  should  not  exhibit  an  acid  reaction.  The  presence  of  ozone  or  hydrogen  peroxide 
in  ether  is  revealed  by  potassium  iodide  solution,  which  turns  brown  within  an  hour  in  the 
dark.  If  water  is  present,  the  ether  imparts  a  green  or  blue  colour  to  ignited  white  copper 
sulphate. 

In  a  mixture  of  alcohol  and  ether,  Fleischer  and  Frank  (1907)  determine  the  proportions 
of  the  two  components  by  pouring  10  c.c.  into  a  graduated  cylinder  containing  5  c.c.  of 
benzene  and  5  c.c.  of  water.  After  shaking,  the  increase  in  volume  of  the  water  gives 
the  alcohol  and  the  increase  in  volume  of  the  benzene  shows  the  quantity  of  ether. 


II.  THIO-ALOCOHLS  AND  THIO-ETHERS 

These  have  the  same  constitution  as  the  alcohols  and  ethers,  excepting  that 
the  oxygen  is  replaced  by  sulphur.  They  are  very  volatile  and  inflammable 
liquids,  almost  insoluble  in  water  and  having  repulsive  garlic-like  odours  ; 
in  the  higher  members,  however,  the  odour  diminishes  and  the  solubility  in 
water  vanishes,  although  they  continue  to  be  soluble  in  alcohol  or  ether. 

(a)  THIO-ALCOHOLS  (or  Mercaptans  or  Thiols  or  Alkyl  Sulphydrates), 
CWH2W+1SH,  have  lower  boiling-points  than  the  corresponding  alcohols.  They 
are  feebly  acid  in  character  and  form  salts  called  Mercaptides,  e.g.  with  mercuric 
oxide.  They  are  soluble  in  concentrated  alkali  solutions.  They  may  be 
regarded  as  hydrogen  sulphide  in  which  one  atom  of  hydrogen  is  replaced  by  an 
alkyl  radicle,  e.g.  ethanthiol  or  ordinary  Mercaptan,  C2H5SH.  As  acids  they 
are  monobasic,  and  salts  are  formed  with  metallic  sodium  or  potassium  ;  the 
lead  salts  are  yellow  and  are  obtained  by  the  action  of  lead  acetate  in  alcoholic 
solution.  Nitric  acid  transforms  the  mercaptans  into  alkylsulphonic  acids  : 
C2H5SH  +  30  =  C2H5-S03H. 

With  iodine,  the  salts  of  sodium,  &c.,  give  disulphides  : 

2C2H5SNa  +  I2  =  2NaI  +  (C2HS)2S2, 

which,  with  hydrogen,  give  mercaptans,  and  with  nitric  acid  disulphoxides, 
(C2H5)2S202 ;  concentrated  sulphuric  acid  gives  disulphides  and  is  itself  reduced 
to  sulphur  dioxide. 

(6)  THIO-ETHERS  (or  Alkyl  Sulphides),  (CwH2n+1)2S,  are  neutral, 
readily  volatile  liquids,  and  afford  a  good  illustration  of  the  variability  of  the 
valency  of  sulphur  (di-  to  hexa-valent). 

They  may  be  regarded  as  derived  from  hydrogen  sulphide  by  replacement 
of  the  two  hydrogen  atoms  by  alkyl  groups.  With  salts  they  form  double 
compounds,  e.g.  ethyl  sulphide  with  mercuric  chloride  gives  (C2H5)2S,  HgCl2. 
They  combine  with  halogens,  giving,  for  instance,  (C2H5)2SBr2,  whilst  when 
treated  with  dilute  nitric  acid  they  fix  an  atom  of  oxygen,  yielding,  e.g. 
(C2H5)2SO,  ethyl  sulphoxide  ;  with  more  energetic  oxidising  agents,  a  further 
oxygen  atom  is  taken  up  with  formation  of  sulphones,  e.g.  Diethylsulphone, 
(C2H5)2S02.  With  hydrogen,  the  sulphoxides  give  sulphides,  but  the  sul- 
phides are  not  reduced.  They  combine  with  alkyl  haloids,  forming  sulphonium 
compounds,  e.g.  ethyl  iodide  and  ethyl  sulphide  give  Triethylsulphonium 
Iodide,  (C2H5)3SI,  which  reacts  like  metallic  iodides  with  silver  hydroxide, 
yielding  Triethylsulphonium  Hydroxide,  (C2H5)3S-OH. 

METHODS  OF  FORMATION.  They  are  obtained :  (1)  by  heating  alkyl  haloids 
or  salts  of  alkylsulphuric  acid  with  an  alcoholic  or  aqueous  solution  of  potassium  sul- 
phide or  hydrosulphidc  :  C2H5Br +  KSH  =  KBr +  C2H5SH  :  2C2H5Br +  K2S  =  2KBr  + 
(C2H5)2S;  2C2H5-S04K  +  K«S  =  2.K,SO4  +  (C2H5)2S. 


(2)  By  the  action  of  phosphorus  pentasulphide,  P2S5,  on  ethers.  Mixed  sulphides  can 
also  be  obtained  by  these  and  various  other  methods. 

METHYL  HYDROSULPHIDE  (Methanthiol) ,  CH3-SH,  is  found  among  the 
gases  from  the  anaerobic  decomposition  of  proteins  (for  instance,  in  the  intestines 
of  animals).  It  is  a  nauseous  liquid,  lighter  than  water  and  boiling  at  6°. 

METHYL  SULPHIDE,  (CH3)2S,  is  a  liquid,  b.pt.  37°,  having  a  disagreeable 
ethereal  odour. 

ETHYL  HYDROSULPHIDE  (Ethanthiol,  Ethylmercaptan,  or  Mercaptan), 
C2H5-SH,  is  a  liquid,  b.pt.  36°,  having  a  repulsive  odour  and  is  used  for  the  preparation 
of  sulphonal.  With  sodium  ethoxide  in  alcoholic  solution  it  gives  Sodium  Mercaptide, 
C2H5SNa,  in  white  crystals  ;  Mercuric  Mercaptide,  (C2H5S)2Hg,  has  also  been  obtained. 

ETHYL  SULPHIDE,  (C2H5)2S,  is  a  liquid,  b.pt.  92°,  insoluble  in  water,  and  forms 
a  crystalline  bromide  (C2H5)2SBr2. 

ETHYL  DISULPHIDE  (Ethanodithioethane),  (C2H5)2S2,  boils  at  151°,  and  is 
obtained  by  the  action  of  iodine  on  mercaptan. 

ETHYL  SULPHOXIDE  (Ethanosulphoxyethane),  (C2H5)2SO,  is  a  dense  liquid, 
soluble  in  water,  and  readily  reducible. 

ETHYLSULPHONE  (Ethanosulphonethane,  Diethylsulphone),  (C2H5)2SO2,  boils 
unchanged  and  does  not  undergo  reduction. 

TRIMETHYLSULPHONIUM  IODIDE,  (CH8)3SI,  obtained  from  sulphur  and 
methyl  iodide,  forms  white  crystals  soluble  in  water  and  with  silver  hydroxide  gives  the 
Hydroxide  (CH3)3SOH,  which  is  an  energetic  base  and  displaces  ammonia  from  its  salts. 

III.  ETHERS  OF  ALCOHOLS  WITH  INORGANIC  ACIDS 

Ethers  formed  from  an  alcohol  residue  and  an  acid  residue  are  termed 
Compound  Ethers  or  Esters.  We  shall  here  describe  those  derived  from  mineral 
acids  and  shall  consider  organic  acid  esters  more  in  detail  when  the  acids 
themselves  have  been  studied.  The  esters  may  be  regarded  as  derived  either 
from  acids  by  the  replacement  of  the  acid  hydrogen  by  an  alkyl  residue,  as 
with  the  salts,  or  from  alcohols  by  replacing  the  hydroxylic  hydrogen  by  an 

acid  radicle :  TT\T/-A  -ir-\*r\ 

HN03  .    .    .  KN03  •  ..    .  C2H5-N03 

or     C2H6-OH  .    .    .  C2H5-0(N02)   .    .    .  C2H5-0(S03H). 

Monobasic  acids  form  only  one  class  of  esters,  viz.  normal  esters. 

Dibasic  acids  form  two  series  of  esters,  normal  and  acid  :  e.g.  C2H5HS04, 
acid  esters,  and  (C2H5)2S04,  normal  ester. 

Tribasic  acids  give  three  kinds  of  esters  with  constitutions  analogous  to 
those  of  the  salts. 

The  Normal  Esters  are  neutral  liquids  of  agreeable  odour,  moderately 
volatile  and  insoluble  in  water. 

The  Acid  Esters  have  acid  reactions,  are  less  stable,  odourless,  soluble  in 
water,  and  volatile  without  decomposition. 

In  general,  these  esters  are  decomposed  by  alkali  or  water  at  a  high  tempera- 
ture (150°  to  180°),  the  components  being  regenerated  ;  this  change  is  known 
as  Saponification  :  C2H5N03  +  KOH  =  C2H5-OH  +  KN03. 

FORMATION.  (1)  They  are  usually  formed  by  the  interaction  of  the 
components  (absolute  alcohol  +  acid),  the  water  which  gradually  forms  being 
fixed  and  the  resulting  ester  distilled.  With  some  acids,  the  corresponding 
salts  in  presence  of  concentrated  sulphuric  acid-  at  100°  to  130°  are  taken, 
so  that  the  acid  is  obtained  in  the  nascent  state  and  the  ester  driven  off  as  it  is 
formed.  They  are  more  readily  obtainable  by  saturating  the  mixture  of 
alcohol  and  salt  with  gaseous  hydrogen  chloride. 

(2)  From  the  silver  salt  of  the  acid  and  alkyl  iodide  : 

Ag2S04  +  2C2H5I  =  2AgI  +  S04(C2H5)2. 


INORGANIC    ESTERS  197 

(3)  From  the  alcohol  or  alkoxide  with  the  chloride  of  the  acid  : 

SOC12  +  2C2H5OH  =  2HC1  +  SO(OCaH5)2 ;  and 
POC13  +  3C2H5ONa  =  3NaCl  +  PO(OC2H5)3  (ethyl  phosphate) . 

(4)  By  passing  the  vapours  of  the  acid  and  alcohol  together  over  a  catalyst 
as  much  as  50  per  cent,  of  the  ester  is  obtained. 

1.  ESTERS  OF  SULPHURIC  ACID  AND  ALKYLSULPHURIC  ACIDS.     These 
are  generally  prepared  from  fuming  sulphuric  acid  and  alcohol,  or  from  silver  sulphate 
and  alkyl  iodide  or  from  alcohol  and  sulphuryl  chloride, 

S02C12  +  2C2H5OH  =  2HC1  +  S02(C2H5O)2  ; 

acid  esters  (alkylsulphuric  acids)  also  exist.     Tertiary  alcohols  do  not  form  these  esters. 

Ethyl  Sulphate,  (C2H5)2S04,  is  an  oily  liquid  with  an  odour  of  mint  and  a  pro- 
nounced acid  character  ;  it  boils  at  208°  and  is  easily  saponified,  even  by  boiling  with 
water  alone.  It  is  formed  by  heating  ethylsulphuric  acid  : 

2C2H5S04H  =  S04H2  +  S04(C2H5)2. 

Ethylsulphuric  Acid,  C2H5SO4H  =  (C2H5O-SO3H),  is  formed  as  an  initial  product 
in  the  manufacture  of  ether  (p.  192).  It  is  soluble  in  water  and  is  distinguished  from 
sulphuric  acid  by  the  solubility  of  its  calcium,  strontium,  barium,  and  lead  salts.  It 
gives  well  crystallised  salts,  the  potassium  salt  being  largely  used  for  preparing  ethyl 
derivatives,  e.g.  when  it  is  dry-distilled  with  potassium  bromide  : 

KBr  +  C2H6SO4K  =  S04K2  +  C2H5Br. 

2.  DERIVATIVES  OF  SULPHUROUS  ACID:    (a)  Sulphurous  Esters;    (b)  Sul- 
phorric  Acids. 

(a)  Ethyl  Sulphite,  SO3(C2H5)2,  and  ethylsulphurous  acid,  C2H5SO3H.     The  latter 
is  known  also  in  the  form  of  salts  and  both  are  readily  saponified,  since  the  sulphur  is  not 
directly  uru'ted  with  carbon  :    CH3  •  CH2  •  0  •  SO2H.    . 

(b)  Ethylsulphonic  Acid,  C2H5-SO3H,  is  obtained  by  the  reaction 

C2H5I  +  SO3Na2  =  Nal  +  C2H5S03Na  ; 
or  by  oxidising  the  thioalcohols  :   C2H5SH  +  03  =  C2H5  •  S03H  ;  or  thus  : 

2C2H5I  +  Ag2S03  =  2AgI  +  (C2H5)2S03  (ethyl  ethylsulphonate). 

Sulphonic  acid  compounds  are  not  saponifiable  ;  diethylsulphonic  acid  is  saponifiable  to 
the  extent  of  one-half,  since  in  the  sulphonic  acids  the  sulphur  is  united  with  carbon  : 
CH3  •  CH2  •  S02  •  OH  ;  the  presence  of  hydroxyl  is  shown  by  the  fact  that  with  PC15  it 
forms  C2H5  •  S02C1,  which  with  hydrogen  gives  ethylsulphinic  acid,  C2H6SHO2,  the  salts 
of  the  latter  reacting  with  alkyl  haloids  to  form  sulphones. 

3.  ESTERS  OF  NITRIC  ACID.     These  are  explosive  if  heated  rapidly  and  undergo 
saponification  when  boiled  with  an  alkali.     Tin  and  hydrochloric  acid  reduce  them,  giving 
Hydroxylamine,  NH2OH,  the  nitrogen  being  separated  from  the  radicle  as  in  saponification; 

Ethyl  Nitrate  :  C2H5O-NO2,  is  a  liquid  boiling  at  86°. 

4.  ESTERS    OF    NITROUS    ACID.     These  are  easily  obtained  by  passing  nitrogen 
trioxide  (N2O3)  into  the  alcohols,  or  by  treating  the  latter  with  alkali  nitrites  and  sulphuric 
acid.     They  are  reduced  by  nascent  hydrogen,  giving  alcohol  and  ammonia. 

Ethyl  Nitrite,  C2H5O-NO,  was  at  one  time  called-m'Jn'c  ether.  Dissolved  in  alcohol,  it 
bears  the  name  spiritus  cetheris  nitrosi,  and  is  used  to  modify  the  taste  of  various  substances. 
It  is  also  used  for  preparing  diazo -compounds. 

5.  NITRO-DERIVATIVES     OF     THE     HYDROCARBONS.     These  are  isomeric 
with  nitrous  esters  but  they  boil  at  higher  temperatures  than  the  latter  and  are  distinguished 
from  them  by  being  non-saponifiable  and  by  giving  organic  amino-compounds  on  reduction, 
as  long  as  the  nitrogen  is  not  severed  from  the  organic  radical : 

CH3.NO2(nitromethane).+  3H2  =  2H2O  +  CH3-NH2. 
They  are  formed  by  treating  alkyl  iodides  with  silver  nitrite  : 

CH3I  +  AgNO2  =  Agl  +  CH3-N02  ; 
with  the  higher  members  of  the  series,  the  nitrous  esters  are  formed  at  the  same  time 


198  ORGANIC    CHEMISTRY 

and  may  be  separated  by  distillation.  Of  the  various  methods  of  formation,  mention  may 
be  made  of  that  based  on  the  action  of  dilute  nitric  acid,  in  the  hot  and  under  pressure,  on 
the  paraffins  : 

C6H14  +  HN03  =  C6H13.N02  +  H2O. 

Hexane  Nitrohexane 

Concentrated  nitric  acid  does  not  give  nitro -compounds  with  the  paraffins,  but  with 
aromatic  hydrocarbons  it  reacts  readily. 

The  difference  in  constitution  between  nitro-derivatives,  e.g.  H3C-N02,  and  nitrous 
esters,  e.g.  H3C-0-N  :  O,  explains  their  different  relations  as  regards  saponification. 

This  also  confirms  the  hypothetical  constitution  of  nitrous  acid,  O :  N  •  OH.  The 
hydrogen  of  the  carbon  atom  united  to  nitrogen  can  be  partially  substituted  by  metals  or 
bromine,  since  it  has  acquired  acid  characters — for  instance,  NaCH2  •  N02 — but  the  acidify- 
ing influence  of  the  nitro -group  is  not  extended  to  the  hydrogens  of  the  other  carbon  atoms. 

These  nitroparaffins  react  with  nitrous  acid  differently  according  as  they  are  primary, 
secondary,  or  tertiary : 

A  Jff.OH 

(a)  Nitroethane,  CH3  -  Of  +  NO2H  =  H2O  +  CH3  -  Of  i.e.  ethyl- 

XN02  \NO2 

nitric  acid,  salts  of  which  are  red. 

CH3  ,IL  CH3X         N  =  O 

(6)  Secondary    Nitropropane,  \OQ          +  N02H  =  H2O  +  )C<f 

CH3/      \N02  CH3/      \N02 

propylpseudonitrole,  which  forms  blue  salts. 

(c)  Tertiary  derivatives  give  no  reaction. 

These  reactions  serve  well  to  distinguish  primary,  secondary,  and  tertiary  alcohols. 

Nitroethane  may  be  used  in  the  manufacture  of  explosives  to  lower  the  freezing-point  of 
nitroglycerine. 

CHLOROPICRIN,  CC13-N02,  boils  at  112°,  and  is  formed  by  the  simultaneous  action 
of  nitric  acid  and  chlorine  on  various  organic  compounds. 

NITROFORM,  CH(NO2)3,  and  TETRANITROMETHANE,C(N02)4,  are  crystallisable 
substances  which  boil  unchanged.  R.  Schenck  (Ger.  Pat.  211,198,  1908)  has  prepared 
tetranitromethane  in  various  ways. 

6.   Various  esters  of  hyponitrous,  phosphoric,  boric,  silicic,  &c.,  acids  are  known. 

DERIVATIVES  OF  HYDROCYANIC  ACID 
A.  NITRILES.        B.   ISONITRILES 

These  compounds  are  formed  by  the  substitution  of  the  hydrogen  of  hydrocyanic  acid 
by  an  alkyl  radical,  but  they  are  not  true  esters,  as  they  do  not  give  the  acid  and  alcohol 
again  on  hydrolysis. 

A.  NITRILES  (or  Alkyl  Cyanides),  are  either  liquid  or  solid,  and  have  a 
pleasant,  faintly  garlic-like,  ethereal  odour.  They  are  lighter  than  water,  in 
which  the  first  terms  are  soluble  without  undergoing  change.  They  boil  at 
about  the  same  temperatures  as  the  corresponding  alcohols. 

PREPARATION.  1.  They  are  obtained  by  distilling  a  potassium  alkyl- 
sulphate  with  potassium  cyanide  or  with  anhydrous  potassium  ferrocyanide, 
or  by  heating  the  cyanide  at  180°  with  methyl  iodide  : 

CH3I  +  KCN  =  KI  +  CHg-CN  (methyl  cyanide  or  acetonitrile). 

2.  Distillation  of  ammonium  salts  of  monobasic  acids  yields  amido- 
compounds  which,  with  a  dehydrating  agent  (P205,  P2S5  or  PC15),  give  nitriles  : 

(a)  CH3-COOH  +  NH3  =  H20  +  CH3-CO-NH2 ; 

Acetic  acid  Acetamide 

(6)  CH5CO-NH2  -  H20  =  CH3-CN. 

Acetonitrile  or 
Methyl  cyanide 


NITRILES    AND    ISONIT  RILES  199 

3.  The  higher  nitriles  are  formed  from  the  acid-amides  containing  one 
more  carbon  atom  or  from  the  primary  amine  containing  the  same  number  of 
carbon  atoms,  by  treatment  with  sodium  hydroxide  and  bromine  ;  or  from  the 
aldehydes  which,  with  hydrocyanic  acid,  give  the  nitriles  of  higher  acids,  the 
so-called  cyanohydrins  or  hydroxynitriles,  liquid  compounds  easily  saponified 
with  regeneration  of  the  aldehyde  : 


+Q 

CH3  •  Of      +  HCN  =  CH3  •  CH<( 

XH  XCN 

Acetaldehyde  Ethylidenecyanohydrin 

PROPERTIES.  When  boiled  with  alkali  or  acid,  or  treated  with 
superheated  steam,  nitriles  give  ammonia  and  an  acid,  from  which  products 
they  can  also  be  formed  : 

(a)  CH3CN  +  H20  =  CH3-CO-NH2  (acetamide)  ; 
(6)  CH3-CO-NH2  +  H20  =  CH3-CO-OH  +  NH3. 

This  reaction  is  of  importance  for  the  synthesis  of  organic  acids  since, 
starting  from  a  given  alcohol  and  transforming  it  into  iodide  and  then  nitrile, 
an  acid  of  the  saturated  series  containing  an  extra  carbon  atom  is  obtained. 

If  the  cyanide  is  treated  with  hydrogen  sulphide  instead  of  water, 
thioacetamide,  CH3-CS-NH2,  is  obtained.  With  hydrochloric  acid,  the 
nitriles  form  chloramides  or  chlorimides,  whilst  with  ammoniacal  bases  they 
give  amidines  (see  later).  Nascent  hydrogen  converts,  them  into  amines  : 
CH3-CN  +  2H2  =  CH3-CH2-NH2  (ethylamine).  By  potassium  or  gaseous 
hydrogen  chloride  the  nitriles  are  polymerised. 

ACETONITRILE  (or  Methyl  Cyanide),  CH3-CN,  is  found  among  the 
products  of  distillation  of  beetroot  molasses  and  of  tar.  It  is  soluble  in 
water  and  boils  at  82°. 

B.  ISONITRILES  (Isocyanides  or  Carbylamines)  are  colourless  liquids 
which  have  a  faint  alkaline  reaction  and  boil  at  rather  lower  temperatures  than 
the  corresponding  nitriles.  They  are  insoluble  in  water  but  dissolve  in  alcohol 
or  ether.  They  have  repellent  odours  and  are  poisonous.  They  are  obtained 
by  the  interaction  of  alkyl  iodides  with  silver  cyanide  (whilst  with  potassium 
cyanide  the  nitriles  are  obtained)  : 

C2H5I  +  AgCN  =  Agl  +  C2H5-NC  ; 

they  are  also  formed  by  treating  the  primary  amines  with  chloroform  and 
alcoholic  potash  (see  p.  100  ;  also  later  under  Amines). 

Although  they  are  stable  towards  alkalis,  the  isonitriles  are  readily 
decomposed  by  water  giving  formic  acid  and  the  corresponding  amino-base 
containing  one  carbon  atom  less  than  the  isonitrile  : 

CH3-NC  +  2H20  =  H-COOH  +  CH3-NH2. 

From  the  nitriles  they  are  distinguished  also  by  the  different  additive 
compounds  which  they  form  with  halogens,  hydrogen  chloride,  hydrogen 
sulphide,  &c.  At  high  temperature  certain  isonitriles  change  into  nitriles. 

CONSTITUTION  OF  THE  NITRILES  AND  ISONITRILES.  The  nitriles  have  the 
carbon  atom  of  the  cyanogen  group  attached  to  the  alkyl  radicle  and  when  they  are  hydro  - 
lysed  only  the  nitrogen  is  removed  as  ammonia.  Acetonitrile  would  hence  have  the 
constitution,  CH3  —  C^N. 

The  isonitriles,  on  the  other  hand,  readily  form  amino -bases  with  loss  of  an  atom  of 
carbon — that  of  the  cyanogen  group — the  nitrogen  remaining  with  the  radicle.  Methyl - 
isocyanide  or  methylcarbylamine  would  hence  have  the  formula  CH3  —  N==C. 


200  ORGANIC    CHEMISTRY 

• 
IV.  NITROGENATED  BASIC  ALKYL  COMPOUNDS  (AMINES) 

If  one  or  more  of  the  hydrogen  atoms  of  the  ammonia  molecule  is  replaced 
by  one  or  more  alkyl  radicles,  substances  called  Amines  are  formed  ;  these 
have  a  basic  character,  which  is  in  some  cases  more  marked  than  that  of 
ammonia  itself  (in  the  dissociation  of  compounds  of  the  ammonia  type,  free 
anions,  OH',  are  formed).  To  ammonia  they  present  other  chemical  analogies. 
They  have  disagreeable  ammoniacal  odours  ;  with  mineral  acids  they  form 
white,  crystalline,  deliquescent  salts  which  are  extremely  soluble  in  water 
and  have  a  basic  nature,  the  nitrogen  then  becoming  pentavalent  ;  for  the 
first  members  of  the  series  the  electrical  conductivity  is  very  high,  higher 
indeed  than  that  of  ammonia,  since  N/100  solutions  are  almost  completely 
dissociated. 

Like  ammonia,  they  give,  with  platinum  chloride,  crystalline  platinichlorides, 
e.g.  methylamine  platinichloride,  (NH2-CH3,  HCl)2PtCl4  ;  they  also  form 
double  salts  with  gold  chloride,  NH2-C2H5,  HC1,  AuCl3.  They  precipitate 
heavy  metals  from  solutions  of  their  salts,  and,  in  excess,  sometimes  redissolve 
them.  The  first  terms  are  gases,  after  which  come  unpleasant  smelling 
liquids  soluble  in  water.  The  higher  members  are  odourless  and  insoluble  in, 
and  lighter  than,  water  ;  they  are  soluble  in  alcohol  and  in  ether. 

The  ammonia  derivatives  are  deliquescent  solids,  and  in  their  behaviour 
greatly  resemble  potassium  hydroxide,  &c.  According  as  they  contain  one 
or  more  alkyl  radicals,  these  bases  are  called  primary  or  aminic,  secondary  or 
iminic,  tertiary  or  nitrilic,  quaternary  or  ammoniacal. 

PROCESSES  OF  FORMATION,  (a)  By  heating  an  alkyl  halogen  com- 
pound with  ammonia  : 

(1)  NH3  +  CnH2+1I  =  HI  +  CwHan+1NH2  ;  the  halogen  hydracid  formed 
unites  with  the  ammonia  and  with  the  amine,  converting  these  partly  into  the 
corresponding    salts  ;     distillation    with    potassium    hydroxide    then    gives  : 
KI  +  H20  +    the  free  base,  CMH2n+1-NH2.     The  latter,  which  is  partly  free 
before  treatment  with  potash,  can  in  its  turn  react  with  a  second  molecule  of 
the  alkyl  halogen  compound,  giving  a  secondary  amine  ; 

(2)  CMH2W+1-NH2  +  CwH2n+1I  =  (CWH2W+1)2NH,  HI;  the  free  base,  which 
can  be  liberated  by  distilling  with  KOH,   reacts   with   a  third  molecule  of 
the  alkyl  halogen  compound,  yielding  a  tertiary  amine ; 

(3)  (CMH2n+1)2NH  +  CWH2W+1I  =  (CnH2w+1)3N,  HI.     Finally,  the  tertiary 
base,  which  remains  free  or  can  be  liberated,  reacts  with  a  fourth  molecule 
of  the  halogen  derivative,  giving  the  salt  of  the  quaternary  base  ; 

(4)  (CnH2n+1)3N  +  CnH2n+1I  =  (CWH2M+1)4NI,  which  is  no  longer  a  crystalline 
ammonia  base  and  is  not  decomposed  by  potassium  hydroxide,  being  more 
energetic  than  the  latter  ;  the  hydrogen  iodide  formed  unites  with  the  amines 
if  such  are  still  present.     When  heated,  the  iodide  of  the  quaternary  base  is 
converted  back  into  the  tertiary  base  and  alkyl  iodide,  whilst   with   silver 
hydroxide  it   gives  the  corresponding  solid  alkylammonium  hydroxide.     In 
this  general  reaction,  the  four  bases  are  always  formed  together,  although  more 
of  one  or  another  is  obtained  according  to  the  nature  of  the  alkyl  group,  the 
temperature,  the  duration  of  the  reaction,  and  the  quantity  of  ammonia  present. 

The  separation  of  the  bases  in  this  mixture  is  not  easy,  and  when  these  are 
present  as  salts,  distillation  with  potassium  hydroxide  yields  the  primary, 
secondary,  and  tertiary  amines,  whilst  the  quaternary  ammonium  compound 
remains  unchanged.  The  three  bases  or  the  corresponding  salts  are  separated 
partly  by  crystallisation  or  by  fractional  distillation,  or,  better,  by  means  of 
ethyl  oxalate,  C202(C2H5O)2,  which  gives  solid  or  liquid  oxamides  [e.g.  solid 
dimethyloxamide,  C202(NH-CH3)2  and  the  ethyl  ester  of  dimethyloxaminic  acid, 
C2H2(OC2H5)-N(CH3)2]. 


A-  M  I  N  E  S  201 

Amines  can  also  be  prepared  by  the  following  reactions  : 

(b)  By  the  action  of  potassium  hydroxide  on  alkyl  isocyanates,  e.g.  ethyl 
isocyanate,  C2H5NCO  +  2KOH  =  K2CO3  +  C2H5-NH2  ; 

(c)  By  reducing  nitro-compounds,  nitrites,  oximes,    or  hydrazones   with 
nascent  hydrogen. 

PROPERTIES.  The  amines  do  not  undergo  hydrolysis  and  are  resistant 
to  the  action  of  acids,  alkalis,  and,  to  some  extent,  oxidising  agents.  The 
hydrogen  combined  with  the  nitrogen  of  amines  can  be  replaced  not  only  by 
alkyl  groups  (see  above),  but  also  by  acid  radicals  (e.g.  by  acetyl,  CH3-CO-) 
and  mixed  amines  with  alkyl  and  acidic  groups  can  also  be  obtained.  A 
characteristic  and  sensitive  reaction  of  the  primary  amines  is  that  with  chloro- 
form in  presence  of  alkali,  which  gives  rise  to  the  unpleasant-smelling  isonitriles  : 
CHC13  +  CH3-NH2  +  3KOH  =  CH3-NC  +  3KC1  +  3H20.  In  alcoholic  solu- 
tion the  primary  and  secondary  bases  form,  with  carbon  disulphide,  deriva- 
tives of  thiocarbaminic  acid,  and  only  when  these  are  derived  from  the 
primary  bases  can  isothiocyanates  be  obtained.  It  is  easier  to  distinguish 
(and  separate)  primary,  secondary,  and  tertiary  amines  by  their  reactions  with 
nitrous  acid.  When  a  hydrochloric  acid  solution  of  the  mixture  is  treated 
with  a  concentrated  solution  of  sodium  nitrite,  the  primary  amine  yields  the 
corresponding  alcohol  (soluble  in  water),  with  evolution  of  nitrogen  : 

CnH2n+1NH2  +  NOOH  =  H20  +  N2  +  CnH2M+1OH. 

The  secondary  amines  give  oily  nitrosamines,  almost  insoluble  in  water  : 
(CnH2W+1)2NH  +  NOOH  =  H20  +  (CnH2n+1)2N-NO ;  with  feeble  reducing 
agents,  the  nitrosamine  is  transformed  into  a  hydrazine,  whilst  with  more 
energetic  reducing  agents  or  with  concentrated  hydrochloric  acid  the  secondary 
amine  is  regenerated,  showing  that  the  nitrous  residue  NO  is  joined  to  the 
iminic  nitrogen  and  not  to  the  carbon.  The  tertiary  amine  does  not  react  with 
nitrous  acid  and  is  hence  left  unchanged  in  the  solution,  from  which  it  can  be 
obtained  by  distillation  in  presence  of  caustic  soda. 

Finally,  the  three  classes  of  amines  can  be  distinguished  by  the  quantities 
of  methyl  iodide  with  which  they  react  to  produce  the  final  quaternary  base 
(see  preceding  page),  with  generation  of  greater  or  less  quantities  of  ionisable 
compounds  (titratable  HI). 

METHYL  AMINE,  CH3-NH2>  is  found  ready  formed  in  certain  plants,  e.g.  in  the  dog- 
mercury  weed  (Mercurialis  perennis).  It  is  formed  in  the  distillation  of  wood  and  occurs 
in  beetroot  and  bone  residues  and  in  herring  brine.  It  is  a  gas  like  ammonia  and  precipitates 
various  metallic  salts,  but,  when  added  in  excess,  does  not  dissolve  nickel  and  cobalt 
hydroxides  ;  it  is  more  highly  basic  and  more  soluble  in  water  than  ammonia,  and  has  a 
strong  odour  of  ammonia  and  rotten  fish.  It  becomes  liquid  at  —  6°  and  at  —  11°  has  the 
sp.  gr.  0-699.  With  sodium  hydroxide  and  bromine  it  gives  acetamide.  Its  hydrochloride, 
CH3  •  NH2,HC1,  is  a  crystalline,  deliquescent  substance  extremely  soluble  in  alcohol.  With 
aluminium  sulphate  its  sulphate  forms  an  alum  containing  24H2O. 

DIMETHYLAMINE,  (CH3)NH,  is  a  liquid  boiling  at  +  7°,  and  is  formed,  together 
with  acetic  acid,  in  the  distillation  of  wood. 

TRIMETHYLAMINE,  (CH3)3N,  is  a  gas  which  liquefies  at  +3°,  and  has  an  intense 
odour  of  rotten  fish.  It  is  found  in  various  plants  (Arnica  montana,  shoots  of  the  pear- 
tree,  &c.),  and  in  herring  brine.  It  is  formed  by  the  decomposition  of  betaine  during  the 
distillation  of  beetroot  molasses  (p.  96). 

ETHYLAMINE,  C2H5-NH2,  is  a  liquid,  b.pt.  +  19°,  and  smells  strongly  of  ammonia, 
which  it  surpasses  in  basicity.  It  dissolves  very  readily  in  water  with  generation  of  heat. 
It  dissolves  aluminium  hydroxide,  and  to  a  small  extent  cupric  hydroxide  but  not  ferric 
or  cadmium  hydroxide. 

DIETHYLAMINE,  (C2H5)2NH,  is  a  liquid,  b.pt.  56°,  and  does  not  dissolve  zinc 
hydroxide. 


202  ORGANIC    CHEMISTRY 

TRIETHYLAMINE,  (C2H5)3N,  is  an  oily  liquid  which  precipitates  metals  from  their 
salts  but  does  not  redissolve  the  precipitates.  It  has  a  strongly  alkaline  reaction  and  boils 
at  89°.  It  is  extremely  soluble  in  cold  water,  but  above  20°  it  becomes  completely  insoluble, 
separating  from  the  water  in  an  oily  layer. 

A  group  of  nitrogen  compounds  which  may  be  considered  as  formed  by  the  condensation 
of  ammonia  (hydrazine,  azoimide,  hydroxylamine,  &c.)  has  been  already  mentioned  in 
vol.  i,  pp.  327  and  332.  The  alkyl  derivatives  of  hydroxylamine,  NH2-OH,  are  divided 
into  two  groups  :  a-alkylhydroxylamines,  in  which  the  alkyl  replaces  the  hydroxylic  hydrogen 
NH2  •  OR,  and  which  hence  have  an  ether  character  and  do  not  reduce  Fehling's  solution  ; 
and  ft-alkylhydroxylamines,  in  which  the  alkyl  radical  replaces  an  amino -hydrogen  and  is 
therefore  joined  to  the  nitrogen,  R — NH — OH  ;  these  reduce  Fehling's  solution  even  in  the 
cold  and  on  energetic  reduction  yield  primary  amines. 

Also  the  Alkylhydrazines,  RNH — NH2,  R2N-NH2,  &c.,  unlike  amines,  reduce  Fehling's 
solution  in  the  cold  and  give  characteristic  reactions  with  aldehydes  and  ketones. 

The  Diazo-compounds  of  the  methane  series  are  of  slight  importance,  whilst  those  of  the 
aromatic  series  are  a  very  important  class  of  compounds  ;  the  former  differ  from  the  latter 
in  that  the  characteristic  divalent  nitrogen  group,  — N=N — ,  has  its  valencies  saturated 
by  only  one  carbon  atom.  Diazomethane,  CH2N2,  which  is  a  yellow,  poisonous  gas,  is 
prepared  from  hydroxylamine  and  dichloromethylamine. 

V.  PHOSPHINES,  ARSINES,  AND   ALKYL  METALLIC  COMPOUNDS 

Like  ammonia,  the  hydrogen  derivatives  of  phosphorus,  arsenic,  antimony,  &c.,  give  rise 
to  alkyl  compounds  which  have  a  very  feebly  basic  character  and  a  very  unpleasant  odour. 

1.  PHOSPHINES.     These  are  gases  or  colourless  liquids  with  repulsive  odours.  Their 
basic  properties  and  their  stability  towards  water  become  more  marked  as  the  number  of 
alkyl  groups  increases.    They  are  readily  oxidisable  with  nitric  acid,  the  remaining  hydrogen 
atoms  of  the  PH3  being  transformed  into  hydroxyl  groups.     The  quaternary  phosphonium 
bases  are  very  strongly  basic,  and,  unlike  the  corresponding  ammonium  bases,  they  lose 
an  alkyl  group  in  the  form  of  a  saturated  hydrocarbon  when  heated,  the  residue  being  a 
trialkylphosphonium  oxide. 

CwH2n+1PH2  (CnH2n+1)2PH          (CMH2n+1)3P          (CnH2n+1)4P-OH 

Primary  phosphine         Secondary  phosphine         Tertiary  phosphine         Tetralkylphosphonium 

hydroxide 

CnH2n+1PO(OH)2      (CnH2n+1)2PO.  OH  (CnH2n+1)3PO 

Alkylphosphonic  acid        Dialkylphosphonic  acid         Trialkylphosphine  oxide 

The  primary  and  secondary  phosphines  are  formed  by  heating  phosphonium  iodide 
with  alkyl  iodides  and  zinc  oxide,  whilst  the  tertiary  phosphines  and  phosphonium  deri- 
vatives are  obtained  from  hydrogen  phosphide,  PH3,  and  alkyl  halogen  compounds. 

2.  ARSINES.     Well-known  primary  and  secondary  compounds  are  :    methylarsenic 
dichloride,  CH3AsCl2  (liquid,  b.pt.  135°)  ;   dimethylarsenic  chloride,  (CH3)2AsCl  (b.pt.  100°)  ; 
dimethylarsine,  (CH3)2AsH  (b.pt.  36°) ;  dimethylarsenic  acid  or  cacodylic  acid,  (CH3)2AsO  •  OH, 
&c.     The  tertiary  arsines  are  obtained  by  the  action  of  sodium  arsenide,  AsNa3,  on  alkyl 
iodides  : 

3C2H5I  +  AsNa3  =  3NaI  +  As(C2H5)3 ; 

they  are  liquids  slightly  soluble  in  water,  with  which  they  do  not  form  bases.  The 
quaternary  arsonium  compounds,  e.g.  (CH3)4AsI  (tetramethylarsonium  iodide),  obtained 
from  the  tertiary  arsines  and  alkyl  iodides,  are,  however,  very  energetic  and  are  able  to 
give,  with  moist  silver  oxide,  tetramethylarsonium  hydroxide.  The  cacodyl 

[(CH3)2As  -  As(CH3)2] 

compounds  were  studied  by  Bunsen  (1837-J843),  who  obtained  cacodyl  oxide, 

(CH3)2As-O.As(CH3)2,  " 

by  distilling  arsenic  trioxide  with  potassium  acetate  (this  reaction  serves  as  a  delicate  test 
for  acetates  in  mixtures) : 

As2O3  +  4CH3-COOK  =  2C02  +  2K2C03  +  [As(CH3)2]20. 
With  hydrochloric  acid,  cacodyl  oxide  gives  cacodyl  chloride,  (CH3)2AsCl. 


ORGANOMETALLIC    COMPOUNDS  203 

Many  of  these  cacodyl  compounds  are  liquids  which  ignite  in  the  air  and  have  nauseating 
odours  ;  the  cacodyl  behaves  like  a  true  electro-  positive  element. 

3.  Various  alkyl  derivatives  are  known  of  antimony  (stibines),  boron,  silicon,  bismuth, 
tin,  &c.,  but  these  are  of  little  practical  importance. 

4.  ALKYLMETALLIC  (Organometallic)  DERIVATIVES.  These  are 
obtained  from  various  metallic  chlorides  or  from  the  metals  themselves  (Zn, 
Hg,  Mg,  Al,  &c.)  by  the  action  of  halogen  derivatives  of  the  hydrocarbons. 
They  are  generally  colourless  liquids  with  low  boiling-points,  and  some  of 
them  are  violently  decomposed  by  water  and  ignite  in  the  air.  Of  importance 
for  many  organic  syntheses  are  the  zinc-alkyls  (see  pp.  32,  96,  and  149). 

ZINC  METHYL  :  Zn(CH3)2,  is  a  colourless,  highly  refractive  liquid,  sp.  gr. 
1-39,  b.pt.  46°,  and  has  an  intense,  repulsive  odour  ;  it  ignites  in  the  air, 
forming  zinc  oxide,  and  with  water  gives  methane  and  zinc  hydroxide.  It  is 
formed  in  two  phases,  as  follows,  and  is  separated  by  distillation  : 

(a)  CH3I  +  Zn  =  Zn(CH3)I  (zinc  methyl  iodide,  solid)  ; 

(b)  2Zn(CH3)I  =  Znl  +  Zn(CH3)2. 

GRIGN  ARD  '  S  REACTION.  Mention  has  already  been  made  of  the  use  of  this  reaction 
in  synthesising  the  saturated  hydrocarbons  (p.  32).  One  molecule  of  a  monohalogen 
(Br  or  I)  compound,  in  presence  of  absolute  ether,  combines  with  an  atom  of  magnesium  : 
Mg  +  C2H5Br  =  C2H5MgBr  (ethyl  magnesium  bromide),  and  with  compounds  containing 
several  carbon  atoms  there  is  always  formed,  as  a  secondary  product,  a  saturated  hydro- 
carbon. The  ether  probably  takes  part  in  the  reaction,  forming  an  intermediate  product 
C2H5.Mg.Br[(C2H6)20]. 

The  latter,  and  also  the  alkyl  magnesium  halogen  compounds,  when  dissolved  in  ether, 
are  highly  reactive  and  form  additive  compounds  with  aldehydes,  ketones,  and  even 
esters  of  mono-  and  poly-basic  carboxylic  acids  ;  with  water  these  additive  compounds 
then  give  the  corresponding  secondary  and  tertiary  alcohols,  the  reaction  occurring  in  the 
following  two  phases  (R  =  alkyl)  : 

/0-MgI 
R-CHO  +  R'Mgl  =  R-C^-R'  ->     +  H2O  =  I-Mg-OH  +  R.CH(OH)-R' 

Aldehyde      Alkyl  mag-  H  Secondary 

nesium  iodide  alcohol 

/OMg-Br 

H  -  COOC2H5  +  C2H5MgBr  =  C2H5  -  C^H  ->     +  C2H5  .  MgBr  = 

Ethyl  formate  XOC2H5 

/OMgBr 
Br.Mg.OC2H5  +  C2H5.CH  ->     +  H2O  =  BrMgOH  +  C2H5.CH(OH).C2H5 

Diethylcarbinol 


If  esters  of  other  monobasic  acids  are  used  instead  of  a  formic  ester,  tertiary  alcohols 
are  obtained,  whilst  esters  of  dibasic  acids  give  dihydric  alcohols.  Hence,  by  means  of 
the  Grignard  reaction,  the  carboxylic  oxygen  of  any  acid  (starting  from  the  corresponding 
ester)  is  ultimately  replaced  by  two  alkyl  residues.  Similar  behaviour  is  also  shown  by  acid 
chlorides  and  anhydrides,  which  also  contain  carbonylic  oxygen  (  —  CO  —  ). 

With  nitriles,  Tcetonimides  and  ketones  are  obtained  : 

yN-Mgl 

R-CN  +  R'Mgl  =  R-Cf  -*     +  H2O  = 

XR' 

IMgOH  +  R.C  (  :  NH).R'  ->   +  H20  =  NH3  +  R.CO-R'(ketone). 
Further,  with  dry  CO2,  alkyl  magnesium  compounds  give  organic  acids  : 

R'Mgl  +  CO2  =  R'-COOMg-I  -v  +  HX  =  IMgX  +  R'-COOH  (acid). 

Other  most  varied  organic  syntheses  have  been  rendered  possible  of  late  years  by  the 
Grignard  reaction. 


204  ORGANIC    CHEMISTRY 

VI.   ALDEHYDES  AND   KETONES,  CwH2nO 

The  elimination  of  two  atoms  of  hydrogen  by  means  of  an  oxidising  agent 
(e.g.  potassium  dichromate  and  dilute  sulphuric  acid,  or  sometimes  even  the 
oxygen  of  the  air),  from  a  primary  or  secondary  alcohol  yields  an  aldehyde  or 
a  ketone  :  R-CH2-OH  +  0  =  H20  +  R-CHO  (aldehyde),  or 

R-CH(OH)R'  +  0  =  H20  +  R-CO-R'  (ketone). 

The  aldehydes  have  a  strong  reducing  action,  as  they  fix  oxygen  and 
become  converted  into  acids  with  the  same  numbers  of  carbon  atoms,  whilst 
the  ketones  resist  oxidising  agents,  and,  if  these  are  very  energetic,  are 
oxidised  to  acids  containing  fewer  carbon  atoms  than  the  original  ketones. 


(a)  ALDEHYDES 

The  first  members  of  this  series  are  neutral  liquids  with  pronounced  and 
often  disagreeable  odours  (formaldehyde  is  a  gas)  and  are  soluble  in  water, 
whilst  the  higher  ones  gradually  become  solid  and  insoluble.  Their  boiling- 
points  are  much  lower  than  those  of  the  corresponding  alcohols. 

The  aldehydes  are  formed  when  a  calcium  or  barium  salt  (or  even  two 
salts)  of  a  monobasic  organic  acid  is  dry  distilled  with  calcium  or  barium 
formate  (reducing  agent):  (R-COO)2Ca  +  (H-COO)2Ca  =  2CaC03  +  2R-CHO. 

They  are  also  obtained  on  heating  with  water  compounds  containing  two 
halogen  atoms  united  to  the  same  carbon  atom  : 

CH3-CHC12  (ethylidene  chloride)  +  H20  =  2HC1  +  CH3-CHO. 
The  constitution  of  the  aldehydes  can  be  deduced  from  their  methods  of 

7° 
formation  (e.g.  the  latter)  and  the  characteristic  aldehyde  group  is  — OC 

XH 

PROPERTIES.  They  are  substances  of  considerable  and  varied  reac- 
tivity. With  oxidising  agents  they  are  transformed  into  acids,  and  this  re- 
ducing property  is  readily  manifested  in  their  reduction  of  ammoniacal  silver 
nitrate  solution  (22  per  cent,  ammonia  solution  and  10  per  cent,  of  dilute  silver 
nitrate  diluted  with  its  own  volume  of  10  per  cent,  sodium  hydroxide  solution  ; 
or  1  grm.  of  silver  nitrate  dissolved  in  30  c.c.  of  water  and  dilute  ammonia 
added  as  long  as  no  precipitate  forms)  or  of  Fehling's  solution  (the  latter,  how- 
ever, is  not  reduced  by  aldehydes  containing  as  many  as  8  or  9  carbon  atoms). 
In  their  turn,  the  aldehydes  are  converted  back  into  the  primary  alcohols 
when  reduced  with  nascent  hydrogen  ;  with  PC15,  they  give  ethylidene 
chlorides  again. 

Hydrocyanic  acid,  ammonia,  sodium  hydrogen  sulphite,  and  sometimes 
alcohol  and  acetic  anhydride  (also  the  alkyl  magnesium  halogen  compounds  : 
see  above,  Grignard's  Reaction)  form  characteristic  additive  products  with  the 
aldehydes  : 

CH3-CHO  +  2C2H5-OH  (+  a  little  HC1)  =  H20  +  CH3-CH(OC2H5)2  (acetal), 

which  is  an  ether  of  the  hypothetical  glycol  (dihydric  alcohol),  CH3-  CH(OH)2  ; 
the  latter,  however,  does  not  exist  in  the  free  state,  since  two  hydroxyl  groups 
cannot  remain  joined  to  one  and  the  same  carbon  atom,  excepting  in  the  case  of 
chloral  hydrate  (see  later)  and  a  very  few  other  substances.1 

They  combine  with  sodium  and  ammonium  bisulphites  (very  concentrated 

1  See  Table  on  opposite  page. 


ALDEHYDES 


205 


solutions)    forming   crystalline    bisulphite   compounds   soluble    in   water   and 
slightly  so  in  alcohol  : 

0  OH 


S0HNa  =  CH 


/ 

-CO- 


H 


H 


S02Na, 


and  these  compounds,  when  heated  with  dilute  acid  or  with  alkali  (even 
Na2C03),  liberate  the  aldehyde  again.  This  reaction  hence  renders  possible 
the  separation  of  aldehydes  from  other  substances. 

The  aldehydes  combine  with  ammonia  forming  crystalline  aldehyde- 
ammonias  soluble  in  water  and  slightly  so  in  alcohol  but  insoluble  in  ether, 
for  example,  CH3-CH(OH)(NH2),  which  gives  the  aldehyde  again  when  heated 
with  a  dilute  acid.  But  formaldehyde,  with  ammonia,  readily  forms  poly- 
merised derivatives,  e.g.  hexamethylenetetramine,  (CH2)6N4. 

With  hydrocyanic  acid  they  form  cyanohydrins  (p.  199). 

An  interesting  change  is  the  aldol  condensation,  that  is,  the  condensation 
of  2  mols.  of  an  aldehyde  brought  about  by  prolonged  heating  with  dilute 
mineral  acids,  dilute  alkalis,  or  even  aqueous  solutions  of  sodium  acetate. 
Possibly  a  molecule  of  water  is  first  added  to  one  of  the  aldehydes  : 


CH, 


X 


,0 


H 


H20  =  CH3 


N 


OH 


this  hypothetical  hydrate  then  condensing  with  another  molecule  of  aldehyde, 
with  separation  of  water  and  formation  of  a  hydroxyaldehyde  (aldol)  : 

,0  //O 


CH3  •  CHX 


CH  •  C 


H 


=  H20 


CH8  •  CH(OH)  •  CH2 


VH 


(fi-hydroxybutyraldehyde).  These  aldols  in  their  turn  readily  lose  a  molecule 
of  water,  forming  an  unsaturated  aldehyde,  which  can  also  be  obtained  directly 
(aldehyde  condensation)  by  heating  the  original  aldehyde  with  a  dehydrating 
agent  such  as  zinc  chloride  : 


CH,-C 


/ 


CH-C 


0 


H 


H 


=H20 


CH,-CH:CH-C 


0 


H 


DERIVATIVES  OP  ACETALS 


Name 

formula 

Boiling-point 

Specific  gravity 

ALKYL  DERIVATIVES 

Mcthylal 

CH2(OCHa)2 

41-30-41-7°  (749-8  mm.) 

0-862  (18°) 

Diethylmethylal  . 

CH2(OC2H6)2 

87° 

0-834  (20°) 

Dipropylmethylal 

CH2(OC,H,)2 

136° 

0-834  (20°) 

Diisopropylmethylal 

CH2(OCaH,)2 

118° 

0-831  (20°) 

Diisobutylmethylal 

CH2(OC4H9)2 

164° 

0-824  (20°) 

Di  i  soamylmcthylal 

CH2(OC5Hn;2  +  H2O 

206° 

0-835  (20°) 

Dihexylmethylal 

CH2(OC,H1S)2 

174°-175° 

0-822  (15°) 

Dioctylacetal 

CH8-CH(OC,H17)2 

289° 

0-848  (15°) 

Dimethylacetal 

CHa-CH(OCH3)j 

63° 

0-865  (22°) 

Diethylacetal 

CH3-CH(OC2H5)2 

102-9° 

0-831  (20°) 

Dipropylacetal 

CH8-CH(OC,H,)2 

147° 

0-825  (22°) 

Diisobutylacetal 

CH3-CH(OC4H!,)a 

170° 

0-816  (22°) 

Di  isoamylacetal 

CHa-C^OCjHnJj 

211° 

0-835  (15°) 

ACID  DERIVAT  VES 

Methylencdiacetate 

CH2(0-CO-CHa)2 

170° 

— 

Ethylencdiacetate 

CH3-CH(O-CO-CH3)2 

169° 

1-073  (15°) 

Ethyleneclipropionate 

CH3-CH(O-CO-C2H5)2 

192° 

1-020  (15°) 

Ethylencdibutyratc 

CH3-CH(O-CO-C3H,)2 

215° 

0-985  (15°) 

Ethylenediisovalerate 

CHa-CH(O-CO-C1H,)2 

225° 

0-947  (15°) 

206  ORGANIC    CHEMISTRY 

The  aldehydes,  especially  form-,  acet-,  and  prop-aldehydes,  &c.,  exhibit  a 
tendency  to  polymerise,  in  the  mere  presence  of  a  little  hydrochloric  or  sulphuric 
acid,  sulphur  dioxide,  zinc  chloride,  &c.  Acetaldehyde,  for  example,  gives 
two  isomerides  :  paraldehyde,  m.pt.  10°,  b.pt.  124°,  and  metaldehyde,  which 
sublimes  at  100°  : 

/0-CH(CH3K 

3C2H40  =  CH3-CH/  )>O. 

X0-CH(CH8r 

These  no  longer  react  with  ammonia,  sodium  bisulphite,  silver  nitrate,  and 
hydroxylamine,  but  they  yield  the  aldehyde  again  when  distilled  in  presence 
of  a  small  quantity  of  dilute  sulphuric  acid. 

With  alkalis,  even  dilute  alkalis,  many  aldehydes,  especially  the  more  simple 
ones  of  the  fatty  series,  resinify,  whilst  some  give  rise  to  an  alcohol  and  an  acid  : 

X° 
2HC-  f       (formaldehyde)  +  H20  =  CH3  •  OH  +  H-  C02H  (formic  acid). 

^U 

With  halogens  the  aldehydes  give  substitution  products,  and  with  hydrogen 
sulphide  various  complex  products  (thioaldehydes,  &c.)  with  characteristic 
odours. 

With  hydroxylamine,  aldehydes  form  aldoximes,  which  are  resolved  into 
their  components  when  boiled  with  acids,  and  yield  nitriles  when  treated  with 
dehydrating  agents  :  CH3-  CHO  +  NH2-  OH  =  H20  +  CH3-  CH  :  N-  OH. 

A  similar  action  is  exhibited  by  the  hydrazines  (as  hydrochloride  or  acetate 
in  acetic  acid  solution  containing  sodium  acetate  ;  the  most  suitable  is  phenyl- 
hydrazine),  which  give  characteristic,  stable,  and  often  crystalline  compounds, 
termed  hydrazones  : 

CH3-CHO  +  C2H5-NH-NH2  (ethylhydrazine)  = 
H2O  +  CH3-CH  :  N-NH-C2H6  (acetaldehyde  ethylhydrazone)  ; 

by  nascent  hydrogen  (4H)  this  is  converted  into  2  mols.  of  primary  amine  : 

2CH3-CH2-NH2. 

Characteristic  of  the  aldehydes  is  also  the  formation  of  crystalline  semi- 
carbazones  by  the  action  of  the  hydrochloride  of  semicarbazide,  NH2  •  CO  •  NH-NH2 
(obtained  by  the  interaction  of  potassium  cyanate  and  hydrazine  hydrate)  : 

R-CHO  +  NH2-CO-NH-NH2  =  H20  +  R-CH  :  N-NH-CO-NH2. 

Both  the  hydrazones  and  semicarbazones  serve  for  the  separation  of  the 
aldehydes  from  other  substances  and  for  their  quantitative  determination. 

Finally  a  characteristic  qualitative  reaction  which  is  given  generally  by  the 
aldehydes  and  is  very  sensitive  is  that  of  Schiff.  It  consists  in  shaking  the 
liquid  to  be  tested  with  a  solution  (0-02  per  cent.)  of  fuchsine  previously 
decolorised  by  a  current  of  sulphur  dioxide.  Traces  of  an  aldehyde  produce  a 
reddish  violet  coloration  (it  is  uncertain  if  pure  ketones  also  give  this  reaction). 

Another  reaction  characteristic  of  the  aldehydes  and  not  given  by  ketones 
is  that  with  benzosulphinehydroxamic  acid  or  with  nitrohydroxylaminic  acid, 

/OH 

OH-NO:N'OH,  which   forms  hydroxamic   acids,   R-C^  the    latter 


producing  a  cherry-red  coloration  with  ferric  chloride. 

FORMALDEHYDE  (or  Methanal),  H-CHO,  is  a  gas  which  liquefies  at 
—  20°  to  a  mobile,  colourless  liquid  having  the  sp.  gr.  0-8153  and  solidifying 
at  —  92°.  It  is  very  soluble  in  alcohol  o^  water,  and  is  placed  on  the  market 


FORMALDEHYDE 


207 


in  the  form  of  40  per  cent,  aqueous  solution  1  under  the  name  of  formalin  or 
formal ;  the  commercial  product  often  contains^l2'to  15  per  cent,  of  methyl 
alcohol  to  prevent  separation  of  polymerised  compounds.  Indeed,  even  in 
the  cold,  formaldehyde  readily  forms  paraformaldehyde,  (CH20)2,  a  white  solid 
soluble  in  water,  or  the  crystalline  trioxymethylene  (or  metaformaldehyde), 
(CH20)3.  Both  of  these  give  the  aldehyde  when  volatilised  by  heat,  and  they 
are  used  thus  as  disinfectants  under  the  names  triformol  and  paraformol. 
Formaldehyde  may  also  give  rise  to  a  mixture  of  saccharine  compounds 
(formose).  With  ammonia  it  gives,  not  an  aldehyde -ammonia,  but  hexa- 
methylenetetramine,  C6H12N4,  which  is  crystalline  and  of  feebly  monobasic 
character.2  With  potassium  hydroxide  it  does  not  resinify,but  yields  methyl 
alcohol  and  formic  acid  (p.  206). 

A  question  which  has  been  under  discussion  for  many  years  is  the  possible  formation 
of  formaldehyde  as  the  first  product  in  the  natural  synthesis  of  carbohydrates  (see  Sugar) 
in  the  leaves  of  plants,  from  carbon  dioxide  under  the  influence  of  chlorophyll. 

Numerous  sensitive  reagents  have  been  employed  to  detect  microscopically  the  transitory 
formation  of  formaldehyde  in  living  leaves  ;  but  almost  all  these  reagents  are  poisonous  to 
plants  and  no  decisive  results  have  been  obtained,  even  those  of  Pollacci  (1907),  who 
distilled  the  leaves  with  water  and  tested  for  formaldehyde  in  the  distillate,  being  doubtful. 
Schryver  (1910)  has  succeeded  in  establishing  the  formation  of  aldehyde  in  green  plants  in 
sunlight,  by  making  use  of  a  very  sensitive  reagent  (detecting  1  part  of  aldehyde  per  million) 
consisting  of  a  solution  of  phenylhydrazine,  potassium  ferricyanide,  and  hydrochloric 

1  The  concentrations  of  commercial  aqueous  solutions  of  formaldehyde  can  be  deduced  from  the  specific 
gravities  by  means  of  the  following  table  (Auerbach,  1905)  : 


Sp.  gr.  at  • 

1-0054 
1-0090 
1-0126 
1-0172 
1-0218 
1-0311 
1-0410 
1-0568 
1-0719 
1-0853 
1-1057 
1-1158 


Grms.  of  CH2O  in  100  c.c. 
of  solution 

2-24 

3-50 

4-66 

6-51 

8-37 
11-08 
14-15 
19-89 
25-44 
30-17 
37-72 
41-87 


Grms.  of  CH2O  in  100  grms. 
of  solution 

2-23 

3-45 

4-60 

6-30 

8-0 
10-74 
13-59 
18-82 
23-73 
27-80 
34-11 
37-53 


If  the  aldehyde  is  pure  and  leaves  no  residue,  the  percentage  by  volume,  if  greater  than  23,  should  be  increased 
by  about  5. 

The  analysis  of  commercial  formalin  is  based  on  the  following  reaction  of  Blank  and  Finkenbeiner : 
2CH2O  +  2NaOH  +  H2O3  =  H2  +  2H2O  +  2H-CO2Na.  Three  grammes  of  the  formaldehyde  solution  are 
poured  into  a  long-necked  flask  containing  25  c.c.  of  2N-caustic-soda  solution  (free  from  carbonates),  the  liquid 
being  mixed  and  50  c.c.  of  hydrogen  peroxide  solution  (neutralised  or  of  known  acidity)  carefully  added,  3  minutes 
being  taken  to  make  this  addition.  After  7  to  8  minutes,  the  excess  of  alkali  remaining  is  titrated  with  2N-sulphurie 
acid.  With  every  cubic  centimetre  of  the  2N-alkali  that  has  reacted  corresponds  0-06  grm.  of  formaldehyde. 
Litmus  purified  several  times  with  alcohol  should  be  used  as  indicator. 

The  estimation  of  the  aldehyde  may  also  be  carried  out  with  ammonia  (see  succeeding  Note). 

Brautigam  (1910)  suggested  determining  formaldehyde  by  adding  to  it  excess  of  clear  calcium  hypochlorite 
solution.  After  a  time  the  solution  deposits  calcium  carbonate,  which  is  filtered,  washed,  and  weighed ;  1  mol. 
of  CaCO3  corresponds  with  1  mol.  of  formaldehyde. 

To  determine  the  methyl  alcohol  which  may  be  present,  5  c.c.  of  the  solution,  diluted  with  100  c.c.  of  water, 
are  distilled  with  an  excess  of  ammonia  (about  10  c.c.  of  concentrated  ammonia),  50  e.c.  of  the  distillate  being 
collected  in  a  100  c.c.  flask  and  made  up  to  volume  with  water.  The  methyl  alcohol  in  5  c.c.  of  this  solution, 
which  contains  only  negligible  traces  of  formaldehyde,  is  determined  by  the  iodine  method  (see  p.  107). 

2  This  reaction  was  proposed  by  L.  Leger  in  1883  as  a  means  of  estimating  formaldehyde  in  commercial 
solutions  :  6CHZO  +  4NH,  =  (CH2)eN«+6H2O  ;  the  reaction  is,  however,  slow  and  the  method  not  very  accurate. 
F.  Hermann  (1911)  has  rendered  it  more  rapid  and  exact  in  the  following  manner.  Pour  cubic  centimetres  of  the 
formalin  are  weighed  into  a  150  c.c.  flask  with  a  ground  stopper,  and  about  3  grms.  of  pure  powdered  ammonium 
chloride  and  exactly  25  c.c.  of  2N-caustic  soda  (equivalent  to  50  c.c.  of  normal  soda)  added.  The  flask  is  stoppered 
and  shaken,  and,  when  the  mass  is  cool,  50  c.c.  of  water  and  4  drops  of  1  per  cent,  methyl  orange  are  added  and  the 
excess  of  alkali  titrated  with  normal  sulphuric  acid.  Deduction  of  the  volume  of  acid  required  from  50  c.c.  gives 
the  volume  of  soda  used  in  liberating,  from  the  ammonium  chloride,  a  corresponding  amount  of  nascent  ammonia, 
which  instantly  transforms  the  aldehyde  into  hexamethylenetetramine.  The  latter  is,  however,  monobasic  and 
reacts  with  part  of  the  sulphuric  acid,  and,  in  order  to  obtain  the  number  of  grammes  of  formaldehyde  in  the 
quantity  of  formalin  taken,  the  number  of  cubic  centimetres  of  soda  arrived  at  above  must  be  multiplied  by  the 
factor  0-06.  If  the  formalin  be  acid  initially,  the  acidity  must  be  determined  separately  by  titration  with  soda 
in  presence  of  phenolphthalein  and  the  50  c.c.  of  soda  increased  accordingly. 


208  ORGANIC    CHEMISTRY 

acid  ;  this  reagent  gives  a  magenta-red  coloration  with  formaldehyde  or  with  the  methylene 
derivative  which  chlorophyll  would  form  with  the  aldehyde. 

MANUFACTURE.  Formaldehyde  is  obtained  by  passing  a  mixture  of  methyl  alcohol 
vapour  and  air  over  copper  or  platinum  gauze  or  the  finely  divided  metals,  which  act  as 
catalysts  (O.  Blank,  Ger.  Pat.  228,697,  1908,  obtained  quantitative  yields  by  using  silver 
precipitated  on  asbestos).  The  product  is  rectified  in  a  column  filled  with  pieces  of  clay. 
Patents  have  been  taken  out  for  the  preparation  of  formaldehyde  by  the  oxidation  of 
methane  with  oxide  of  iron,  hydrogen  peroxide,  &c.  It  is  also  formed  by  the  electrolysis 
of  dilute  methyl  alcohol,  and  some  years  ago  a  patent  was  granted  for  its  preparation  by 
passing  a  mixture  of  formic  acid  vapour  and  hydrogen  through  a  tube  containing  pieces 
of  metal  (e.g.  lead,  iron,  zinc,  nickel,  silver,  &c.),  heated  to  300°. 

Formaldehyde  has  considerable  antiseptic  power,  even  in  aqueous  solution. 
It  is  largely  used  at  the  present  time  as  a  disinfectant  in  houses  and  for  the 
preservation  of  readily  putrescible  substances  (meat,  beverages,  &c.).  Its 
vapour  has  an  acute  and  penetrating  odour  and  irritates  the  eyes.  On 
account  of  the  property  possessed  by  formaldehyde  of  combining  with  proteins 
to  form  insoluble  and  stable  products,  it  is  used  in  the  manufacture  from 
casein  of  articles  of  a  horny  consistency  and  in  making  imitation  pegamoid ; 
also  in  preparing  photographic  films  with  gelatine,  for  rendering  insoluble 
or  hardening  the  coloured  gelatine  for  textile  printing,  and  for  hastening  the 
tanning  of  skins. 

Owing  to  its  great  reactivity,  it  is  largely  used  in  organic  syntheses,  e.g.  in 
the  manufacture  of  aniline  dyes. 

Various  solid  and  liquid  disinfectants  containing  free  aldehyde  are  prepared 
by  means  of  soaps  (soap  solutions  are  also  on  the  market  under  the  names 
of  lysoform  and  ozoform,  the  starting  product  in  the  case  of  the  latter  being 
sulphoricinoleic  acid). 

A  characteristic  and  very  sensitive  reaction  of  formaldehyde  is  that 
proposed  by  Rimini,  according  to  whom  a  mixture  of  phenylhydrazine 
hydrochloride,  sodium  nitroprusside  and  caustic  soda  is  coloured  blue  even 
by  minimum  traces  of  the  aldehyde. 

Formaldehyde  gives  Schiffs  reaction  even  in  presence  of  a  certain  amount 
of  sulphuric  acid,  whilst  acetaldehyde  does  not. 

The  price  of  commercial  40  per  cent,  formaldehyde  is  about  £4  per  quintal, 
while  pure,  powdered  paraldehyde  costs  4s.  to  5s.  per  kilo. 

ACETALDEHYDE  (Ethanal),  CH3-CHO,  is  a  colourless,  mobile  liquid,  sp.  gr.  0-801 
(at  0°),  b.pt.  21°,  and  solidifies  at  —121°.  It  has  an  agreeable  but  suffocating  odour, 
and  it  polymerises  with  moderate  ease,  giving  the  paraldehyde  and  metaldehyde  (see  above). 
It  dissolves  in  water,  alcohol,  or  ether,  and  is  readily  converted  into  acetic  acid  by  oxidising 
agents. 

It  is  prepared  by  pouring  a  mixture  of  3  parts  of  90  per  cent,  alcohol  and  4  parts  of 
concentrated  sulphuric  acid  slowly  into  a  solution  of  3  parts  of  potassium  bichromate  in 
12  of  water,  the  liquid  being  kept  cool  meanwhile.  The  solution  is  then  heated  in  a  reflux 
apparatus  on  a  water-bath  and  subsequently  distilled.  The  mixture  of  alcohol,  aldehyde, 
and  acetal  thus  obtained  is  heated  to  50°  and  the  aldehyde  vapour  passed  into  cold  ether. 
On  passing  ammonia  into  this  solution,  crystallised  aldehyde-ammonia,  CH3  •  CH(OH)  •  NH2, 
separates  ;  this,  when  pressed  and  distilled  with  dilute  sulphuric  acid,  gives  pure  acetalde- 
hyde. The  commercial  aldehyde  is  obtained  from  the  foreshots  of  alcohol  distillation,  from 
which  it  is  separated  by  simple  fractional  distillation. 

It  is  of  importance  in  many  organic  syntheses  and  in  .the  production  of  silver  mirrors. 
The  price  of  50  per  cent,  solutions  is  2s.  per  kilo,  that  of  the  95  to  99  per  cent,  product 
3s.  6d.,  and  that  of  the  purest  aldehyde  15s.1 

1  The  estimation  of  acetaldehyde  is  based  on  the  following  reaction  (Seyewetz  and  Bardin) : 
2Na2SO,  +  2CH.-CHO  +  HaSO4  =  NaaSO4  +  (CH.-CHO,  NaHSO,)z. 

The  aldehyde  is  diluted  to  7  to  8  per  cent,  and  about  10  c.c.  of  this  solution  is  poured  into  40  c.c.  of  10  per  cent, 
pure  sodium  sulphite  solution.     After  the  addition  of  a  few  drops  of  neutralised  alcoholic  phenolphtbaJc.in  solution 


UNSATURATED    ALDEHYDES  209 

METHYLAL,   H.CH(OCH3)2,  and  ACETAL,  CH3.CH(OC2H6)2  (see  p.  204). 

PROP  ALDEHYDE,  C2H5-CHO,  is  found  among  the  tarry  products  from  the 
distillation  of  wood.  Valeraldehyde,  C4H9  •  CHO,  boils  at  92°  and  begins  to  show  a  diminu- 
tion in  solubility  in  water.  Normal  heptaldehyde  (oenantaldehyde),  C6H13-CHO,  is  found 
among  the  products  of  decomposition  of  castor  oil  when  this  is  subjected  to  distillation  in 
a  vacuum.  Nonyl  aldehyde,  C8H17  •  CHO,  occurs  in  the  oxidation  products  of  oleic  acid  or, 
better,  in  the  decomposition  products  of  the  ozonide  of  oleic  acid  (Harries,  Molinari,  &c.) ; 
it  boils  at  about  192°. 

CHLORAL  (Trichloroethanal),  CC13-CHO,  is  the  most  important  halo- 
genated  derivative  of  the  aldehydes.  It  is  a  dense  liquid  with  a  peculiar, 
penetrating  odour  and  boils  at  94-4°.  It  is  prepared  by  passing  chlorine  into 
pure  alcohol  (96  per  cent.)  for  some  days,  the  hydrochloric  acid  formed  being 
collected.  The  liquid  is  then  heated  with  sulphuric  acid  in  a  reflux  apparatus 
until  no  further  evolution  of  hydrogen  chloride  occurs,  the  chloral  being 
distilled  and  subsequently  purified  by  rectification.  Within  recent  times  it 
has  also  been  prepared  electrolytically  :  the  bath  contains  potassium  chloride 
solution  at  100°  and  is  fitted  with  a  diaphragm  ;  alcohol  is  passed  into  the  anode 
chamber,  where  chlorine  is  formed,  and  the  hydrogen  chloride  produced  at  the 
anode  is  neutralised  by  the  potassium  hydroxide  formed  (1  h.p.-hour  yields 
50  grms.  of  chloral). 

Chloral  gives  the  reactions  of  the  aldehydes  and  is  used  in  medicine  as  an 
anaesthetic  and  soporific,  being  first  treated  with  water  to  form  the  crystalline 

OTT 
CHLORAL     HYDRATE,    CC13 •  CH< ::£;,  which  is  readily  soluble  in  water 

(m.pt.  57°)  ;  this  is  one  of  the  few  compounds  having  two  hydroxyl  groups 
united  to  the  same  carbon  atom.  The  crystalline  alcoholates  or  Acetals, 
CC13-CH(OH)-OC2H5  and  CC13-CH(OC2H5)2,  corresponding  with  this  hydrate 
are  known. 

Chloral  costs  about  6s.  per  kilo. 

ALDEHYDES  WITH  UNSATURATED  RADICALS 

ACRYLIC  ALDEHYDE  (Propenal,  Acrolem,  or  Allyl  Aldehyde),  CH2  :  CH-CHO, 

is  formed  when  fats  are  burned,  owing  to  loss  of  water  by  the  glycerol  present  ;  a  similar 
change  takes  place  when  glycerol  is  heated  with  potassium  hydrogen  sulphate  or  boric 
acid.  Acrolein,  which  can  also  be  obtained  by  the  oxidation  of  allyl  alcohol,  is  a  liquid, 
b.pt.  52-4°,  and  has  a  characteristic  pungent  odour.  When  oxidised,  it  yields  acrylic 
acid  and,  when  reduced,  allyl  alcohol.  It  has  all  the  chemical  properties  of  the  aldehydes 
and  polymerises  in  the  course  of  a  few  hours.  With  ammonia,  it  gives  a  solid,  basic 
condensation  product,  soluble  in  water  :  2C3H40  +  NH3  =  H2O  +  C6H9ON  (acrole'ir.- 
ammonia,  which  gives  picoline  on  distillation).  Owing  to  its  double  linking,  acroleiin 
unites  with  2  mols.  of  sodium  bisulphite  and  the  resulting  product,  when  boiled  with  acid, 
gives  up  only  one  bisulphite  molecule,  namely,  that  combined  with  the  aldehyde  group. 

CROTONIC  ALDEHYDE,  CH3.CH  :  CH-CHO,  is  obtained  by  distilling  the  corre- 
sponding aldol,  CH3.CH(OH).CH2.CHO,  at  140°  or  by  the  dehydrating  action  of  zinc 
chloride  or  sodium  acetate  on  the  saturated  aldehyde.  It  is  a  liquid  boiling  at  104°  and 
possessing  a  penetrating  odour,  and  its  constitution  is  shown  by  the  fact  that  it  yields 
crotonic  acid  when  oxidised  with  silver  oxide. 

CITRAL  L(or  Geranial),  (CH3)2C  :  CH.CH2.CH2-C(CH3)  :CH-CHO,  is  a  liquid  of 
pleasant  odour,  b.pt.  229°,  and  occurs  in  many  essences  (of  mandarin,  citron,  lemon,  orange, 
and  most  abundantly — 60  per  cent. — in  that  of  Verbena  Indiana  or  lemon -grass,  from  which 
it  is  separated  by  means  of  its  bisulphite  compound).  It  may  also  be  obtained  by  the  gentle 
oxidation  of  the  corresponding  alcohol,  gerianol,  which  boils  at  230°.  It  exists  in  two  stereo - 
isomeric  forms,  the  cis-  and  trans-modifications.  When  oxidised  with  potassium  bisulphate 
at  170°,  citral  is  transformed  into  cymene  (with  a  closed  ring)  with  separation  of  water. 

the  liquid  is  cooled  to  4°  to  5°  and  titrated  with  normal  sulphuric  acid  until  it  is  decolorised.  This  occurs  when 
no  further  combination  of  aldehyde  and  sulphurous  acid  takes  place.  This  determination  is  not  affected  by  the 
presence  of  alcohol,  acetal,  or  paraldehyde. 

II  14  , 


210  ORGANIC    CHEMISTRY 

CITRONELLAL,  (CH3)2C  :  CHC-H2.CH2.CH(CH3).CH2.CHO,  is  found  with  citral 
in  citron  oil  and  boils  at  208°. 

PROPARGYL  ALDEHYDE,  CH  •  C-CHO,  is  a  solid,  m.pt.  60°,  and  is  obtained 
from  dibroinoacroleiin  by  way  of  the  acetal.  As  it  contains  the  group  CH  :  C,  it  forms 
metallic  derivatives  (see  p.  91). 

(b)  KETONES  (R—  CO—  R') 

These  have  the  carbonyl  group  attached  to  two  alcohol  radicals  and,  if 
the  latter  are  similar,  are  known  as  simple  ketones  and,  if  different,  mixed  ketones. 
The  first  member  must  contain  at  least  three  carbon  atoms.  They  present 
the  same  cases  of  isomerism  as  the  secondary  alcohols,  and  are  metameric  with 
the  aldehydes. 

Up  to  the  Cu-compound  they  are  liquid  and  beyond  that  solid,  but  all 
are  less  dense  than  water.  They  resist  feeble  oxidation  but  energetic  oxidising 
agents  (dichromate  and  dilute  sulphuric  acid)  break  the  chain  of  the  ketone 
at  the  carbonyl  group,  thus  forming  an  acid  with  a  lower  number  of  carbon 
atoms:  CH3-CO-CH3  +  40  =  H20  +  CO2  +  CH3-C02H.  In  mixed  ketones, 
however,  the  carboxyl  is  mainly  united  to  the  smaller  alkyl  radical  (R  or  B'), 
but  the  acid  with  the  higher  alkyl  is  always  formed  to  some  extent.  With 
ammonia,  the  action  is  different  from  that  in  the  case  of  aldehydes  :  water  is 
eliminated  from  2  or  3  mols.  of  ketone  and  di-  and  tri-ketonamines  (or  acetona- 
mines),  e.g.  C6H13ON,  formed.  Further,  the  ketones  do  not  polymerise,  but  they 
form  condensation  products.  They  do  not  react  with  ammoniacal  silver 
solutions  or  with  Fehling's  solution,  and  are  hence  not  reducing  in  character 
(difference  from  aldehydes). 

With  phosphorus  pentachloride  they  give  the  corresponding  dichloro- 
derivatives  ;  for  instance,  acetone  gives  2-dichloropropane,  CH3-CC12-CH3. 

On  reduction,  they  yield  secondary  alcohols,  and  with  very  energetic  oxidis- 
ing reagents  (H202,  &c.),  they  form  characteristic  polymerised  ketonic  per- 
oxides, e.g.  [(CH3)2C02]2,  [(CH3)2C02]3.  With  ethyl  orthoformate  they  give 
acetals,  (CH3)2C(OC2H5)2,  and  similarly  with  mercaptans  they  form  Mercaptols, 
e.g.  (CH3)2C(SC2H5)2,  which,  when  oxidised  with  permanganate,  gives  Sulphonal, 
(CH3)2C(S02C2H5)2. 

Ketones,  which  generally  contain  the  group  CH3-CO-  form,  with  sodium 
bisulphite,  compounds  which  are  crystalline  and  hence  readily  separable  from 
other  substances  : 

(CH3)2CO  +  S03HNa  =  (CH3)2C<j?;?N    (sodium  acetonebisulphite). 

-  3 

This  compound  crystallises  also  with  1  mol.  H20  and  yields  acetone  easily 
when  heated  with  dilute  soda  solution. 

With  hydrocyanic  acid,  ketones  give  the  cyanohydrins  or  nitriles  of  higher 

OH 

acids  :  e.g.  (CH3)2C<CN  . 

With  hydrogen  sulphide,  but  only  in  presence  of  HC1,  &c.,  they  form 
trithioketones,  which  on  heating  give  simple  thioketones. 

With  hydroxylamine,  ketones  readily  form  the  so-called  ketoximes, 
R^CrN-OH,1  similar  to  aldoximes,  and  with  phenylhydrazine  they  give 
phenylhydrazones,  just  as  aldehydes  do  : 


(CH3)2CO  +  NH2-OH  =  H20  +  (CH3)2C  rN-OH  (acetoxime}. 

1  For  the  ketoximes  (as  for  the  aldoximes)  stereoisomerides  exist  as  a  consequence  of  the  stereoisomerism  of 
nitrogen  (see  p.  22),  which  has  been  studied  by  Beckmann,  V.  Meyer,  Auwer,  H.  Goldschmidt,  Hautzsch  arid 
Werner,  Minunni,  &c.  Thus  for  aldoximes  we  have  the  two  following  stereoisomeric  configurations  : 

R—  C—  H  K—  C—  H 

II  (syw-aldoximo)  ;iml  ||         (rtnti-aldoxime), 

N—  OH  OH—  N 


K  E  T  O  N  E  S  211 

Under  certain  conditions,  e.g.  by  the  action  of  acetyl  chloride,  ketoximes 
undergo  an  atomic  transposition  by  which  they  are  converted  into  amides, 
substituted  in  the  ammo-group  (Beckmann  rearrangement),  these  being  tauto- 
meric  with  the  ketoximes  : 

R-C-R'  R-C:O 

II  -  I 

N-OH  NHR'. 

The  action  of  nitrous  acid  (or  its  esters)  yields  isonitrosoketones  : 
CH3-CO-CH3  +  N02H  =  H20  +  CH3-CO-CH  :  N-OH. 

In  presence  of  various  reagents,  e.g.  lime,  potash,  sulphuric  or  hydrochloric 
acid,  &c.,  the  ketones  lose  water  and  undergo  condensation  (whilst  aldehydes 
polymerise)  :  3(CH3)2CO  =  2H20  +  C9H140.  Similar  condensations  occur 
between  ketones  and  aldehydes. 

The  FORMATION  OF  KETONES  takes  place  in  the  dry  distillation  of 
wood  or  of  the  calcium  or  barium  salts  of  many  organic  acids  or  on  simple 
heating  of  the  latter  or  the  anhydrides  of  the  acids  in  presence  of  phosphorus 
pentoxide  :  (CH3  •  C02)2Ca  =  CaC03  +  CH3  •  CO  •  CH3  (acetone)  ;  if  mixed 
ketones  are  required,  a  mixture  of  the  salts  of  two  different  acids  is  used. x  Note- 
worthy also  is  the  formation  of  ketones  by  the  oxidation  of  secondary  alcohols 
(see  p.  103):  CH3-CH(OH)-CH3  +  0  =  H20  +  CH3-CO-CH3.  Also,  with 
powdered  metals  (Sabatier  and  Senderens,  p.  34),  secondary  alcohols  give 
ketones,  hydrogen  being  eliminated. 

Ketones  are  also  formed  by  the  action  of  water  in  the  hot  on  chlorinated 
hydrocarbons  having  two  chlorine  atoms  united  to  the  same  carbon  atom  : 
,(CH3)2CC12  +  H20  =  2HC1  +  CH3-CO-CH3. 

Another  general  method  of  preparing  ketones  is  based  on  the  interaction 
<of  zinc  alkyls  and  acid  chlorides,  the  additive  product  formed  being  immediately 
decomposed  with  water  so  as  to  avoid  the  formation  of  tertiary  alcohols  : 
2CH3-CO-C1  +  Zn(C2H6)2  =  ZnCl2  +  2CH3-CO-C2H6  (methyl  ethyl  ketone). 

Acetone  is  formed  when  acetic  acid  vapour  is  passed  over  a  heated  acetate  or 
base. 

ACETONE  (Propanone),  CH3-CO-CH3,  is  found  in  small  quantities  in  the 
human  organism,  where  it  is  formed  in  larger  amounts  during  certain  diseases 
(diabetes,  acetonuria).  It  is  formed  in  considerable  quantities  in  the  dry 
distillation  of  wood  and  of  other  organic  substances  (calcium  acetate,  sugar, 
gum,  wool -fat,  &c.).  It  is  a  liquid  with  an  ethereal  odour  and  a  characteristic 
burning  taste,  b.pt.  56-3°,  sp.  gr.  0-7921  at  18°.  It  solidifies  at  —94°  and  is 
soluble  in  water  (from  which  it  separates  on  addition  of  soluble  salts),  alcohol, 
ether,  and  chloroform  ;  it  dissolves  fats,  resins,  ethereal  oils,  nitrocellulose, 
&c.,  and  is  readily  inflammable. 

In  aqueous  solution  rendered  alkaline  with  sodium  carbonate,  it  is  oxidised 
with  ease  by  potassium  permanganate,  and  chromic  acid  converts  it  into  acetic 
acid  and  carbon  dioxide.  With  sodium  it  forms  sodium  fi-allyloxide  : 

CH3-C(ONa)  :  CH2. 

whilst  for  ketoximes,  stereoisomerides  exist  if  the  two  alkyl  radicals  are  different : 

B^C— It'  B^-C— R' 

I!  (gyw-ketoxime)  and  II          (antf-ketoxime) 

ff— OH  OH— N 

These  isomerides  are  transformable  one  into  the  other,  and  in  addition  to  their  physical  differences  exhibit  also 
chemical  differences,  e.g.  in  regard  to  the  readiness  with  which  they  lose  water  (aldoximes  giving  nitrites). 

1  This  reaction  can  be  used  to  demonstrate  the  normal  constitution  (absence  of  branching  from  the  carbon 
chain)  of  acids,  ketones,  and  hydrocarbons  (paraffins),  since  on  distilling  an  organic  barium  salt  with  a  normal  C« 
chain  with  barium  acetate,  a  Cll  +  1  ketone  is  obtained  which  should  also  be  normal,  as  the  methyl  group  of  the 
acetate  unites  with  the  carbonyl  at  the  end  of  the  chain  of  the  acid.  On  oxidation,  this  ketone  gives  a  €„  _ !  acid 
which  will  also  be  normal.  From  this  are  prepared  the  ketone  and  then  a  C,,  _  ,  acid,  so  that  normal  products  are 
always  obtained  (also  the  corresponding  hydrocarbons)  by  this  gradual  descent  from  a  high  acid  of  which  the 
constitution  is  known  to  be  normal. 


212  ORGANIC    CHEMISTRY 

In  the  crude  form,  it  is  used  in  lac  and  colour  factories  and  in  a  more  or  less 
pure  state  in  the  manufacture  of  iodoform.  Also  at  the  present  time  pure 
acetone  is  employed  in  large  quantities  for  gelatinising  smokeless  powders  and, 
owing  to  the  intense  burning  taste  it  imparts,  as  a  denaturant  for  spirit,  from 
which  it  cannot  be  separated  by  distillation. 

Industrial  Preparation.  Calcium  acetate  obtained  from  pyroligneous  acid  (which  see) 
is  subjected  to  dry  distillation,  the  temperature  being  controlled  so  that  it  does  not  exceed 
300°  ;  the  vapours  evolved  are  rapidly  cooled  and  condensed,  giving  crude  acetone.  In 
order  to  avoid  superheating  and  irregularity  during  the  distillation,  moist  calcium  acetate 
is  sometimes  employed.  The  acetone  vapour  escaping  condensation  is  easily  recovered 
by  passing  it  through  towers  down  which  a  spray  of  sodium  bisulphite  solution  falls  ;  this 
fixes  the  acetone,  which  can  be  liberated  by  distilling  the  solution  in  presence  of  an  alkali. 
In  France,  Buisine  has  utilised  the  wash-waters  of  dirty  wool  to  prepare  acetone  from  the 
fat  they  contain.  This  process  has  been  tried  on  an  industrial  scale  at  Roubaix,  but  as  yet 
without  marked  success. 

The  crude  acetone  is  purified  by  digesting  it  with  quicklime  and  then  distilling  it  from 
sodium  hydroxide  and  subsequently  over  sodium  sulphite. 

Crude,  impure  acetone  (oil  of  acetone)  is  sold  at  £3  8s.  per  quintal  if  dark  or  £4  if  pale. 
Acetone  for  industrial  purposes  (85  to  90  per  cent.)  sells  at  £6,  the  pure  product  at  £6  16s., 
and  the  chemically  pure  (98  to  100  per  cent. )  at  £7  8s.  per  quintal.  The  bisulphite  compound 
is  also  placed  on  the  market  at  £4  per  quintal  (or  14s.  per  kilo  for  the  chemically  pure). 
In  1908  England  consumed  1500  tons  of  acetone  (worth  £100,000),  which  was  almost  all 
imported  from  the  United  States.  In  1910  England  imported  1100  tons  of  acetone,  of  the 
value  of  £57,000.  In  1910  Italy  imported  438  hectols.  of  the  value  of  £2600. 

Tests  for  Acetone.  These  are  of  especial  importance  for  explosive  factories,  where  a 
highly  purified  product  is  required.  It  should  dissolve  in  water  in  all  proportions  without 
rendering  it  turbid.  When  mixed  with  a  little  0-1  per  cent,  permanganate  solution  it 
should  retain  the  colour  for  some  minutes.  If  acetone  contains  water,  when  mixed  with 
an  equal  volume  of  light  petroleum  (boiling  at  40°  to  60°)  two  layers  are  formed  ;  if  no 
water  is  present,  the  liquids  mix  perfectly.  At  least  95  per  cent,  of  it  should  distil  between 
56°  and  56-5°,  and  it  should  not  redden  blue  litmus  paper.  Kramer's  quantitative  iodo- 
metric  test  (see  p.  107)  should  indicate  at  least  98  per  cent,  of  acetone  ;  Strache's  method, 
in  which  phenylhydrazine  is  employed,  may  also  be  used.1  The  detection  of  acetone  in 
other  substances  is  effected  by  means  of  orthonitrobenzaldehyde  and  caustic  soda,  which 
convert  acetone  into  indigo. 

MESITYL  OXIDE,  CH3.CO-CH  :  C(CH3)2,  is  an  aromatic  liquid  boiling  at  132°. 

PHORONE,  (CH3)2C  :  CH-CO-CH  :  CMe2,  forms  yellow,  readily  fusible  crystals,  and 
is  obtained  by  saturating  acetone  with  hydrogen  chloride. 

BUTANONE  (Methyl  ethyl  ketone) ,  CH3C-O.C2H5,  is  a  liquid,  b.pt.  81°,  and  is 
contained  in  wood-spirit. 

KETENES 

These  constitute  a  group  of  substances  discovered  by  Staudinger  since  1905.  Although 
they  contain  the  ketonic  group,  CO,  they  differ  markedly  from  the  ketones  in  their  great 
reactivity,  since  they  are  unsaturated  compounds,  that  is,  unsaturated  ketones. 

They  are  derived  from  the  type  R2C  :  CO,  which  was  formerly  thought  incapable  of 
existing  in  the  free  state.  The  residues,  R,  may  be  either  aromatic  or  aliphatic  hydro- 
carbon radicals.  All  these  compounds  can  be  derived  from  KETENE,  CH2  :  CO,  which  is  a 
colourless  gas,  b.pt.  —56°,  m.pt.  —151°,  and  was  prepared  in  1908  ;  it  has  a  disagreeable 
odour  (resembling  somewhat  those  of  chlorine  and  acetic  anhydride),  is  poisonous  and  even 
in  small  quantity  produces  intense  headache.  It  is  easily  polymerised  (by  metallic  chlorides 
or  tertiary  bases),  yielding  a  coloured  resin.  It  decolorises  ethereal  bromine  solutions 

1  Strache'»  method  for  the  indirect  estimation  of  compounds  containing  carbonyl  groups  (aldehydes  and  ketones). 
When  to  a  solution  of  an  aldehyde  or  a  ketone  is  added  an  excess  of  a  phenylhydrazine  solution  of  definite  strength, 
the  excess  of  the  latter  which  does  not  combine  may  be  deduced  from  the  amount  of  nitrogen  liberated  on 
decomposing  (oxidising)  in  the  hot  with  Fehling's  solution  [a  mixture  in  equal  volumes  of  the  following  two 
solutions  :  (a)  69-26  grms.  of  air-dried  copper  sulphate  crystals  dissolved  in  water  to  1  litre  ;  (6)  346  grms.  of 
Rochelle  salt  dissolved  in  800  c.c.  of  water  +  105  grms.  sodium  hydroxide,  the  whole  made  up  to  1  litre  with 
water] :  C,HBNH-NH2  +  O  =  H2O  +  C,H,  +  N2.  The  test  is  made  on  0-2  to  0-6  grm.  of  substance  (aldehyde 
or  ketone)  and  the  details  of  the  operation  are  described  in  Zeitschr.  fi'ir  analyt.  Chemie,  1892,  p.  573,  or  in  Hans 
Meyer's  •'  Determination  of  Radicals  in  Carbon  Compounds,"  1899,  p.  65. 


DERIVATIVES    OF    GLYCOL  213 

instantly,  and,  unlike  disubstituted  ketenes,  does  not  undergo  oxidation  in  the  air.  The 
most  stable  and  best  characterised  of  these  compounds  are  dimethyl-,  (CH3)2C :  CO,  and 
diphenyl-ketene,  (C6H5)2C :  CO  ;  monomethyl-,  CH3-CH:CO,  and  monoethyl-ketene, 
C2H5  •  CH  :  CO,  have  properties  similar  to  those  of  carbon  suboxide,  O  :  C  :  C  :  C  :  0,  and 
resemble  the  isocyanates  in  their  great  reactivity.  The  disubstituted  ketenes  are  coloured 
and  readily  oxidise  in  the  air  ;  two  molecules  condense  with  one  of  a  base  (pyridine,  quino 
line),  and  they  unite  with  the  C  :  N  •  group  (benzylideneaniline)  and  with  the  C  :  0  group 
(quinones),  forming  /3-lactams  and  /3-lactones.  All  the  ketenes  combine  with  water, 
alcohols,  or  amines  at  the  double  carbon -linking,  giving  compounds  of  an  acid  nature. 
The  monosubstituted  ketenes  are  also  called  aldoketenes  and  the  disubstituted  ones, 
ketoketenes.  They  are  usually  prepared  by  the  action  of  zinc  on  an  ethereal  solution  of 
acid  halogen  derivative  with  a  second  halogen  in  the  a -position  : 

CH3.CHBr.COBr  +  Zn  =  ZnBr2  +  CH3-CH :  CO. 

a-bromopropionyl  bromide 

The  ketenes  are  easily  transformed  into  acids ;  and  those  that  condense  (the  ketoketenes) 
with  unsaturated  groups  (ethylene  and  carbonyl  compounds,  Schiff's  bases,  thioketones, 
nitroso-and  azo -compounds)  form  compounds  with  a  closed  chain  of  four  or  six  carbon  atoms, 
these  being  resolved  into  two  unsaturated  compounds  when  heated.  The  aldoketenes 
undergo  polymerisation  more  readily,  giving  derivatives  of  cyclobutane  which  decompose 
on  heating. 

B.  DERIVATIVES  OF  POLYHYDRIC  ALCOHOLS 

The  ethers  of  polyhydric  alcohols  are  generally  prepared  by  the  methods  used  for  ethers 
of  the  monohydric  alcohols  and  have  many  properties  in  common  with  these. 

ETHYL  ETHER  OF  GLYCOL,  OH-C2H4.OC2H5,  boils  at  127°  and  the  DIETHYL 
ETHER,  C2H4(OC2H5)2,  at  123°.  Of  the  esters  of  glycbl,  the  mono-  and  di-acetates, 
C2H4(OC2H3O)2,  which  are  liquids  soluble  in  water,  are  well  known.  Glycolchlorohydrin 
or  Monochloroethyl  Alcohol,  OH-CH2-CH2-C1,  boils  at  130°,  is  soluble  in  water  and 
is  prepared  by  passing  hydrogen  chloride  into  hot  glycol.  GLYCOLSULPHURIC  ACID, 
OH  C2H4-O-SO3H,  is  the  sulphuric  ester  of  glycol.  Glycol  Dinitrate,  C2H4(N03)2,  is 
a  yellowish  liquid  insoluble  in  water  and  explode  son  heating ;  it  is  prepared  by  treating 
glycol  with  nitric -sulphuric  mixture  (see  later,  Nitroglycerine).  It  is  readily  hydrolysed 
by  alkali. 

ETHYLENECYANOHYDRIN,  CH2  :  C  :  N-CH2.OH,  is  isomeric  with  Ethyl- 
idenecyanohydrin,  CH3-CH(OH).CN.  Ethylene  Cyanide,  C2H4(CN)2,  obtained  by  the 
action  of  potassium  cyanide  on  ethylene  bromide,  forms  a  crystalline  mass  ;  on  hydrolysis 
it  gives  Succinic  Acid,  C2H4(COOH)2. 

ETHYLENE  OXIDE,  CH2-0-CH2,  isomeric  with  acetaldehyde,  is  a  liquid  with  an 
ethereal  odour,  sp.  gr.  0-898  (at  0°),  b.pt.  12-5° ;  although  neutral  in  its  reaction  it 
precipitates  certain  metallic  hydroxides  from  solutions  of  their  salts.  It  is  formed  on 
distilling  glycolchlorohydrin  with  potash.  It  reacts  readily  and  dissolves  in  water  with 
gradual  formation  of  glycol. 

The  following  compounds  are  also  known  :  Ethylene  M  onothiohydrate,  C2H4(OH)-SH  ; 
Glycol  Mercaptan (Ethan-l  :  2-dithiol), C2H4(SH)2  ;  Dithioglycol  Chloride,  (C2H4C1)2S,  which 
is  a  very  poisonous  liquid.  Hydroxymethylsulphonic  Acid,  CH2(S03H)-OH,  is  solid  and  is 
obtained  from  methyl  alcohol  and  fuming  sulphuric  acid.  MethylenedisulpJionic  (or 
Methionic)  Acid,  CH2(SO3H)2,  is  formed  from  acetylene  and  fuming  sulphuric  acid,  by  way 
of  Acetaldehydedisulphonic  Acid,  CHO-CH(S03H)2,  which  with  lime  gives  formic  acid  and 
methionic  acid  ;  the  latter  is  isomeric  with  ethylsulphuric  acid,  but  cannot  be  hydrolysed. 
Hydroxyethylsulphonic  Acid,  OH-CH2-CH2-S03H  (Isethionic  Acid),  is  a  crystalline  mass 
formed  by  treating  ethyl  alcohol  with  sulphur  trioxide  ;  ethylene  with  S03  gives  Carbyl 
Sulphate,  C2H4(S03)2,  which  forms  sulphuric  and  isethionic  acids  with  water. 

Glycol  forms  also  two  amines:  Hydroxyethylamine,  OH •  C2H4 •  NH2 . (primary  mono- 
valent  base,  or  Hydroxyalkyl  Base,  or  Hydramine),  and  Ethylenediamine,  C2H4(NH2)2 
(primary  divalent  base).  These  may  also  be  regarded  as  derived  from  one  or  two  molecules 
of  ammonia,  in  which  all  or  part  of  the  hydrogen  is  substituted  by  the  hydroxyethyl  group, 
•  C2H4-OH,  or  by  ethylene,  C2H4<^.  Thus,  such  compounds  as  the  following  are  known  : 
NH2-C6H4.OH;'  (NH2)2C2H4;  NH(C2H4.OH)2,  Dihydroxydiethylamine ;  N(C2H4.OH)3, 


214  ORGANIC     CHEMISTRY 


Trihydroxytriethylamine  ;  (NH)z(Q^li)z,Dieihylenediamine;  N2(C2H4)3,  Triethylenediamine  ; 
and  finally  quaternary  bases  containing  alkyl  groups,  e.g.  CTioline  (or  Bilineurine), 
(CH3)3  •  N(  •  OH)  •  C2H4  •  OH,  or  HydroxyetTiyltrimethylammonium  Hydroxide,  which  is 
obtained  from  trimethylamine  and  ethylene  oxide  and  is  found  in  the  bile,  in  egg-yolk, 
and  in  the  brain  in  the  form  of  lecithin  (see  later)  ;  it  is  not  poisonous,  but  when  oxidised 
with  nitric  acid  yields  Muscarine,  CH(OH)2-CH2-N(CH3)3-OH,  which  has  a  distinct 
poisonous  action.  On  putrefaction,  choline  gives  neurine  (or  Trimethylvinylammonium 
hydroxide),  N(CH3)3(C2H3)-OH,  which  is  also  poisonous.  Many  of  these  com- 
pounds are  formed  in  putrefying  proteins  and  in  dead  bodies,  and  are  called 
'ptomaines. 

These  bases  are  prepared  by  the  same  methods  as  the  monovalent  bases  (p.  200),  the 
primary  diamines,  for  example,  being  obtained  by  reducing  the  nitriles,  CnH2n(CN)2,  in 
hot  alcoholic  solution  by  means  of  sodium  or  from  ethylene  bromide  and  alcoholic  ammonia 
at  100°.  They  are  liquid  or  solid  substances  and  have  certain  of  the  characters  of  ammonia. 
Pentamethylenediamine  or  Cadaverine,  NH2  •  CH2  •  CH2  •  CH2  •  ^^2  •  CI^  •  NH2,  boils  at  179° 
and,  being  a  ^-diamine,  can  form  Piperidine,  C5H11N,  with  separation  of  ammonia. 

NH 

Diefhylenediamine.  or   Piperazine,   C2H4<^>,-p,>>C2H4,  melts  at  104°  and  boils  at  146°. 

Tetramethylenediamine  is  called  also  Putrescine. 

TAURINE  (Aminoethylsulphonic  Acid),  NH2-CH2-CH2-S03H,  is  found  in  com- 
bination with  cholic  acid  (as  Taurocholic  Acid)  in  the  bile  of  various^animals  and  also 
in  the  lungs  and  kidneys.  It  forms  monoclinic  prisms  soluble  in  hot  water  but  insoluble 
in  alcohol,  and  has  a  neutral  reaction,  the  basic  and  acid  groups  neutralising  one  another. 
It  is  not  hydrolysable. 

Of  the  derivatives  of  Olycerol,  the  CTilorTiydrins  or  esters  of  hydrochloric  acid  are  of 
interest  ;  they  are  liquids  soluble  in  alcohol  or  ether,  and,  to  a  less  extent,  in  water.  With 
hydrochloric  acid,  glycerol  forms  the  Monochlorhydrin,  C3H5(OH)2C1,  of  which  two 
isomerides  («-  and  ft-)  are  known,  and  the  Dichlorhydrin,  C3H5(OH)C12,  also  existing  in 
two  isomeric  forms.  Either  of  these,  when  treated  with  PO5,  gives  the  trichloro- 
derivative,  C^sCl^1  At  the  present  time  interest  attaches  also  to  the  formins  and  acetins, 
which  are  used  in  the  manufacture  of  non  -congealing  explosives.2 

GLYCIDE  ALCOHOL,  CH2-CH-CH2.OH,  is  a  liquid,  b.pt.  162°,  soluble  in  alcohol 

\0/ 

or  ether,  and  also  in  water,  with  which  it  gives  glycerol  again  ;  with  hydrochloric  acid 
it  gives  the  chlorhydrin.  It  may  be  regarded  as  derived  from  glycerol  by  the  removal  of 
a  molecule  of  water,  and  is  prepared  by  the  separation  of  HC1  from  the  a-monochlorhydrin 
by  means  of  baryta.  It  is  isomeric  with  propionic  acid  and  reduces  ammoniacal  silver 
solution.  Separation  of  hydrogen  chloride  from  the  dichlorhydrin  yields  Epichlorhydrin, 
CH2  —  C-HCH2C1,  which  may  be  regarded  as  the  hydrochloric  ester  of  glycide  alcohol. 

\0/ 

It  boils  at  117°,  has  an  odour  like  that  of  chloroform  and  is  insoluble  in  water.  It  is 
isomeric  with  propionyl  chloride  and  monochloroacetone. 

GLYCEROPHOSPHORIC  ACID,  OH,CH2.CH(OH).CH2.0-PO(OH)2,  is  optically 
active,  as  also  are  its  calcium  and  barium  salts  (laevo  -rotatory).  It  is  interesting  from  the 
fact  that  when  the  hydroxyl-groups  are  esterified  with  palmitic,  stearic,  or  oleic  acid,  and 

1  According  to  Ger.  Pat.  180,668,  the  monochlorhydrin  is  made  by  heating  for  15  hours  in  an  autoclave  at 
120°  a  mixture  of  100  parts  of  glycerol  with  150  parts  of  hydrochloric  acid  (sp.  gr.  1-185).  The  water  is  distilled 
off  and  the  residue  subjected  to  fractional  distillation  in  a  vacuum  (15  mm.  pressure)  ;  after  the  acid  and  water 
have  been  eliminated,  the  monochlorhydrin  distils  over  at  130°  to  150°,  and  the  unaltered  glycerine  at  165°  to  180°. 
If  it  is  to  be  nitrated  and  used  for  explosives,  it  is  sufficient  to  get  rid  of  the  water  and  acid.  According  to  Fr.  Pat. 
370,224,  the  monochlorhydrin  may  also  be  obtained  by  shaking  glycerine  with  the  calculated  quantity  of 
sulphur  chloride  at  a  temperature  of  40°  to  50°  ;  the  water  formed  is  distilled  off  in  a  vacuum  at  60°  to  70°.  The 
a-Monochlorhydrin,  CH2C1-CH(OH)'CH2-OH,  is  obtained  (according  to  Fr.  Pat.  352,750)  bypassing  hydrogen 
chloride  into  glycerine  heated  to  70°  to  100°. 

Like  glycerine  itself,  the  chlorhydrins  are  easily  nitrated,  yielding  non-congealing  explosives  (gee  Inter). 

3  MonoaceMn,  C.3H6(OH)?(O'COCH3),isobtained  by  heatingfor  lOto  15  hoursat  100°  a  mixture  of  10  parts 
of  glycerol  with  15  parts  of  40  to  100  per  cent,  acetic  acid,  the  weak  acetic  acid  (25  to  30  per  cent.)  that  distils 
over  being  condensed  separately.  Ten  parts  of  70  per  cent,  acetic  acid  are  then  added  and  the  weak  acid  —  up 
to  40  per  cent.,  which  distils  at  120°  —  collected  apart.  After  this  the  temperature  is  raised  in  3  hours  to  250°, 
the  weak  acid  still  being  kept  separate.  The  crude  monoacetin  remaining  contains  about  44  per  cent,  of  combined 
acetic  acid  and  about  0-8  per  cent,  of  the  free  acid.  This  acetin  is  soluble  in  water  and  serves  well  for  the  manu- 
facture of  explosive  and  non-congealing  nitroacetins  (see  Explosives)  and  for  gelatinising  the  nitrocellulose 
of  smokeless  powders  (Vender  Ger.  Pat.  226,422,  1906), 


EXPLOSIVES  215 

the  phosphoric  residue  united  to  choline,  it  gives  rise  to  the  important  group  of  lecithins, 
which  are  optically  active  : 

OR  •  CH2  •  CH(OR')  •  CH2 . 0  •  PO(OH)  -  O  •  CH2  •  CH2  •  N(CH3)3  •  OH, 

where  R  and  R'  are  fatty  acid  residues. 

Lecithins  are  found  in  the  brain,  yolks  of  eggs,  and  many  seeds  and  are  soluble  in 
alcohol,  and,  to  a  less  degree,  in  ether  ;  they  give  salts  with  acids  and  with  bases  and  yield 
solid  compounds  with  chloroplatinic  acid  or  cadmium  chloride.  They  are  saponified  by 
baryta,  with  formation  of  choline,  fatty  acids,  and  glycerophosphoric  acid. 

Of  the  nitric  esters  of  glycerine,  the  most  important  is  trinitroglycerine, 
or  trinitroglyceric  ester,  C3H5(ON02)3,  which  is  one  of  the  most  powerful 
explosives.  We  shall  hence  study  it  from  the  industrial  standpoint,  first  dis- 
cussing certain  general  notions  concerning  explosives.  The  manufacture  of  the 
latter  constitutes  one  of  the  most  interesting  industries  of  organic  chemistry, 
partly  because  of  the  varied  mechanical  appliances  which  it  requires. 

EXPLOSIVE  SUBSTANCES 

The  name  explosive  substances,  or  explosives,  is  given,  in  general,  to  those 
solid  and  liquid  bodies  which,  under  the  influence  of  heat,  percussion, 
electrical  discharge,  &c.,  are  transformed  instantaneously  and  completely— 
or  nearly  so — into  a  gaseous  mass  with  an  enormously  increased  temperature. 

If  the  reaction  takes  place  in  a  closed  space,  the  gases  thus  produced  and 
heated  exert  a  very  considerable  pressure  which  can  be  immediately  trans- 
formed into  mechanical  work,  the  enclosing  substance  and  all  the  surround- 
ing objects  being  shattered  with  great  violence  and  noise.  Such  a  phenomenon 
(or  effect)  constitutes  a  so-called  explosion,  and  if  it  attains  very  great  rapidity 
and  power  it  is  termed  a  detonation.  For  a  constant  quantity  of  gas  produced 
in  an  explosion,  the  effect  will  be  the  greater  the  higher  the  temperature 
developed  in  the  reaction. 

THEORY  OF  EXPLOSIVES.  The  chemical  reactions  and  physical  phenomena 
of  explosives  are  produced  under  conditions  differing  greatly  from  those  in  which  physical 
and  chemical  properties  of  substances  are  usually  studied.  The  pressures,  temperatures, 
and  velocities  with  which  we  have  to  deal  in  ordinary  phenomena  are  of  a  very  different 
order  from  that  of  the  enormous  pressures  of  the  gases  in  the  interior  of  the  earth's  crust, 
which  are  measured  in  hundreds  of  thousands  or  millions  of  atmospheres.  So  also  the 
temperatures  in  various  stars,  e.g.  in  the  sun,  reach  thousands  of  degrees,  and  the  velocities 
of  the  planets  hundreds  of  kilometres  per  second.  The  phenomena  now  to  be  considered, 
although  they  do  not  attain  these  enormous  magnitudes,  still  do  approach  them.  Indeed, 
explosions  give  pressures  of  tens  of  thousands  of  atmospheres,  temperatures  of  thousands 
of  degrees,  and  velocities  (of  projectiles)  of  thousands  of  metres  per  second. 

Almost  all  explosive  substances  contain  oxygen  (furnished  by  chlorates,  nitrates,  &c.), 
only  very  few,  such  as  nitrogen  chloride  and  iodide,  and  aniline  fulminate,  being  without 
it.  Mixtures  of  oxidising  agents  with  readily  combustible  substances  (sulphur,  carbon, 
sugar,  &c.)  are  explosive,  but  they  are  less  powerful  than  those  composed  of  single  com- 
pounds which  explode  by  themselves.  This  is  because  the  elements  necessary  for  complete 
combustion  are  in  much  greater  proximity,  being  present  in  the  molecule  of  the  explosive 
itself  ;  examples  of  such  explosives  are  nitroglycerine,  guncotton,  mercury  fulminate, 
picric  acid,  &c. 

The  determination  of  the  theoretical  power  of  an  explosive  requires  a  knowledge  of  : 

(a)  the  chemical  reaction  accompanying  the  explosion,  so  that  the  heat  of  the  reaction, 
the  temperature,  and  the  volume  and  relative  pressure  of  the  gases  formed  can  be  deduced  ; 

(b)  the  velocity  of  the  reaction.     In  order  to  understand  the  theory  of  explosives,  it  is  indis- 
pensable to  call  to  mind  the  fundamental  principles  of  thermochemistry  and  of  thermo- 
dynamics, for  which  the  reader  is  referred  to  the  brief  account  given  in  vol.  i,  pp.  49 
and  57. 


216  ORGANIC    CHEMISTRY 

(a)  The  chemical  reaction  is  deduced  from  the  difference  in  composition  between  the 
explosive  and  the  products  resulting  from  the  explosion.     When  there  is  sufficient  oxygen 
in  the  explosive  to  produce  complete  combustion,  the  nature  and  quantities  of  the  gases 
can  be  calculated  a  priori,  and  from  their  heats  of  formation  their  temperature  can  be 
deduced.     The  total  combustion  of  nitroglycerine,  when  exploded  in  a  closed  space,  gives 
the  following  products  (a) :   2C3H5(NO3)3  =  6C02  +  5H20  +  3N2  +  0. 

When  there  is  deficiency  of  oxygen,  as  in  guncotton  and  other  substances,  it  is  not  easy 
to  foretell  the  products  of  the  reaction,  as  these  vary  with  the  conditions  in  which  the  explo- 
sion occurs,  and  usually  several  reactions  take  place  simultaneously.  Further  the  gases 
found  after  the  explosion  of  such  products  are  probably  not  always  those  formed  at  the 
instant  of  the  explosion,  as  at  such  high  temperatures  certain  substances  (H2O,  CO2,  &c.) 
may  undergo  dissociation  with  absorption  of  heat.1 

(b)  The  heat  developed  in  the  explosion  is  deduced  by  calculation  from  the  thermo- 
chemical  data  of  the  equation,  but  the  practical  result  is  not  in  accord  with  the  theoretical 
calculation,  since  part  of  the  heat  (25  to  30  per  cent.)  that  should  theoretically  be  developed 
is  transformed  into  mechanical  work,  which  is  what  is  utilised  in  practice.     In  calculating 
theoretically  the  heat  of  explosion,  the  heat  of  formation  of  the  explosive  (from  the  elements) 
is  subtracted  from  the  heat  that  should  theoretically  be  developed  in  the  reaction.     The 
heat  of  explosion  varies,  however,  according  as  it  is  determined  at  constant  volume  or 
at  constant  pressure  ;    in  the  latter  case  the  explosion  of  nitroglycerine,  for  example,  is 
effected  in  the  open  air,  since  then  the  volume  varies,  but  the  pressure  is  only  that  of 
the  atmosphere. 

The  heat  cf  formation  of  nitroglycerine  from  its  elements  (see  p.  25)  is  given  by  the 
following  equation  (6) :  C3  +  H5  +  N3  +  O9  =  C3H5(NO3)3  +  98  Gals. 

The  heat  of  reaction  of  nitroglycerine  can  be  calculated  from  equation  (a)  given 
above,  from  which  it  is  seen  that  2  mols.  or  454  grms.  of  nitroglycerine  yield 
6C02  +  5H20  +  3N2  +  O.  The  heat  of  formation  of  6C02  is  6  x  97  =  582  Cals., 
and  that  of  5H20,  5  x  68-5  =  342-5  Cals.  For  the  nitrogen  and  oxygen  there  is  no 
development  of  heat  since  they  are  not  combined,  so  that  the  total  heat  of  reaction 
calculated  on  the  gases  formed  in  the  explosion  of  2  grm.-mols.  of  nitroglycerine  will 
be  924-5  (i.e.  582  +  342-5)  Cals.  From  this  must  be  subtracted  the  heat  of  formation 
from  the  elements  of  2  mols.  of  nitroglycerine,  since  on  decomposing  under  these 
conditions  of  temperature  the  explosive  first  of  all  liberates  its  atoms,  absorbing  as 
much  heat  as  is  evolved  in  its  formation  from  its  elements  (reaction  b),  i.e.  196  (98  x  2) 
Cals.  per  2  mols.  The  atoms  thus  liberated  combine  immediately  to  give  the  gases 
which  result  from  the  explosion,  the  heat  of  formation  of  which  has  already  been 
calculated. 

The  true  theoretical  heat  of  explosion  at  constant  pressure  for  454  grms.  of  nitroglycerine 
will  hence  be  728-5  (i.e.  924-5  -  196)  Cals.,  or  for  a  kilo,  1603  Cals.  The  heat  of  reaction 
at  constant  volume — the  explosion  occurring  in  a  closed  vessel — is  rather  higher,  the 
heat  corresponding  with  the  expansion  of  the  gas  (see  vol.  i,  pp.  26  and  50)  not  being 
absorbed  as  no  expansion  takes  place  ;  theoretically  the  heat  at  constant  volume  is  calcu- 
lated to  be  1621  Cals.  per  kilo.2  Serrau  and  Vieille,  by  direct  practical  measurements, 
found  the  heat  of  explosion  of  nitroglycerine  at  constant  volume  to  be  1600  Cals.,  which 
confirms  the  accuracy  of  the  calculation. 

With  substances  which  themselves  contain  sufficient  oxygen  for  complete  combustion 

The  following  Table  gives  the  percentage  compositions  of  the  gases  resulting  from  the  normal  explosion  of 
various  explosives  in  the  calorimetric  bomb  : 

CO  CO2  O2  CH4  Hj  N2 

Nitrocellulose  powder  46-87  16-8  0-08  1-26  20-44  14-9 


Gelatine  dynamites. 
Carbonite 
Picric  acid 
Trinitrotoluene 


34-0  32-68  0-75  10-0  21-0 

36-0  19-2  2-8  27-6  14-4 

61-05  3-46  0-34  1-02  13-18  21-1 

57-01  1-93  0-11          .     —  20-45  18-12 


For  every  gramme-molecule  of  a  substance  passing  from  the  solid  or  liquid  to  the  gaseous  state,  owing  to 
the  new  volume  occupied,  590  small  calories  (vol.  i,  pp.  26  and  50)  are  absorbed.  In  the  explosion  of  2  mols. 
of  nitroglycerine,  14-5  mols.  of  gas  (6C02  +  5H2O  -f  3N2  +  O)  are  formed,  and  these,  on  expanding,  will 
absorb  14-5  x  590  =  8550  small  calories,  or  8-5  Cals.  per  454  grms.  of  nitroglycerine,  i.e.  18  Cals.  per  kilo. 
This,  added  to  1603,  the  heat  of  reaction  at  constant  pressure,  gives  1621  Cals.  as  the.  heat  of  reaction  at  constant 
volume. 


217 

during  explosion,  it  is  not  easy  to  calculate  theoretically  the  heat  of  explosion,  since  the 
products  of  the  reaction  are  not  exactly  known  ;  in  such  cases,  various  direct  practical 
determinations  must  be  made. 

It  is  not  easy  to  calculate  theoretically  the  temperature  of  the  gases  at  the  moment  of 
explosion,  since  the  specific  heat  of  the  gases  at  such  high  temperatures  cannot  be  deter- 
mined, but  is  certainly  rather  higher  than  the  ordinary  value.  Further,  at  such  tem- 
peratures dissociation  phenomena  occur  which  cannot  be  defined  ;  these,  however,  lower 
the  temperature,  although  not  greatly,  since  with  the  great  pressures  developed  the  disso- 
ciation is  minimal.  On  the  other  hand,  with  the  means  we  possess,  it  is  not  possible  to 
measure  these  temperatures  directly  and  only  approximately  can  they  be  determined 
for  black  powder.  In  general,  however,  they  are  very  high  and  in  some  cases  exceed  4000° 
(for  instance,  by  burning  ballistite  in  the  air,  platinum  withm.pt.  1800°  is  easily  melted), 
but  even  these  temperatures,  deduced  indirectly,  are  much  lower  than  those  calculated 
theoretically.1 

The  temperature  of  ignition  does  not  usually  coincide  with  the  temperature  of  explosion 
since  explosion  is  caused  not  so  much  by  the  temperature  as  by  the  pressure  and  other 
factors  to  be  considered  later  ;  so  that  for  explosion  to  occur,  special  conditions  (detonators) 
are  necessary.  But  for  some  substances,  e.g.  black  powder,  non -compressed  guncotton,  &c., 
the  temperature  of  ignition,  given  in  the  following  Table,  is  identical  or  almost  so  with  that 
of  explosion  : 

Fulminate  of  mercury  .          .          .     200° 

Non -compressed  guncotton    .          .     220°  to  250° 

Nitroglycerine      .          .          .         .218°  (explodes'at  240°  to'250°) 

Black  powder       *>'••'•         •         •     288° 

There  are  thus  explosives  which  explode  when  merely  ignited  with  a  match  and  others 
which  are  exploded  indirectly  by  means  of  detonators^ 

The  mechanical  work,  in  kilogram-metres,  yielded  by  an  explosive  is  calculated  by 
multiplying  the  number  of  calories  developed  in  the  explosion  of  1  kilo  of  the  substance 
by  the  mechanical  equivalent  of  heat  (=  425,  see  vol.  i,  pp.  50  and  51).  For  various 
explosives  this  mechanical  work  (or  potential  energy)  is  given  in  the  following  Table  : 

Nitroglycerine          .  (1  kilo)  =  1600  Gals,  x  425  =  680,000  kilogram -metres 

Explosive  gelatine   .  .  .  =  1530  „  =  650,000  „ 

Dynamite        .          .  .  .  =  1178  „  =  500,000 

Guncotton       .         .  .  .  =  1074  „  =  456,000  „ 

Fine  sporting  powder  .  .  =    849  „  =  360,000  „ 

Potassium  picrate    .  .  .  =    780  „  =  330,000  „ 

Fulminate  of  mercury  .  .  =    403  „  =  170,000  „ 

Nitrogen  chloride     .  '  .  .  =    339  „  =  144,000  „ 

Owing  to  various  causes,  the  total  theoretical  energy  of  explosives  cannot  be  utilised 
practically  ;  e.g.  the  expansion  of  the  gases  at  the  moment  the  projectile  leaves  the  cannon 
or  gun,  the  friction,  the  heating  of  the  barrel,  &c.,  all  constitute  losses  of  the  useful  effect 
of  the  explosive. 

The  volume  of  the  gases  formed  in  the  explosion  can  be  calculated  with  reference  to  0° 
and  760  mm.,  taking  account  of  the  fact  that  at  the  moment  of  explosion  the  water  is 
in  the  state  of  vapour.  But  in  practice  it  is  of  more  importance  to  calculate  the  volume 
at  the  temperature  of  explosion,  when  a  knowledge  of  the  gases  formed  is  possible,  as  is 
the  case  with  nitroglycerine,  and,  in  general,  with  explosives  containing  sufficient  oxygen 

1  Indeed,  water-vapour,  formed  from  Ha  +  0,  should  have  theoretically  a  temperature  of  7927°  (see  Calcula- 
tion, vol.  i,  p  378),  but  in  the  most  favourable  theoretical  conditions  the  oxy-hydrogen  flame  does  not  exceed 
2500°.  For  carbon  dioxide  the  heat  of  formation  is  97,000  cals.,  and  the  specific  heat  0-217,  so  that  for  44  grms. 

97  000 
of    C02  gas  (grm.-mol.)  the  temperature  attainable  would  be  TJTTiESJS  =  10,160°,  and  allowing  for  the  fact 

that  along  with  the  6  mols.  of  CO2  and  5  of  H2O,  the  3  mols.  of  N2  and  half  a  mol.  of  oxygen  formed  in  the  explo- 
sion of  nitroglycerine  are  also  to  be  heated  the  theoretical  temperature  of  the  gases  from  the  explosion  would 

ft 

be  about  7000°.     This  theoretical  temperature  is  determined  in  general  by  the  formula  t  =   — - — TTTT — ^-^ 

where  p,  p',  p"  .  .  .  are  the  weights  of  the  gases  formed  in  the  explosion,  s,  s',  s"  .  .  .  their  specific  heats,  and 
C  the  total  heat  in  caloriesi 


218  ORGANIC    CHEMISTRY 

for  their  complete  combustion.  It  is,  however,  not  easy  to  calculate  the  volume  of  gas 
formed  by  products  containing  an  insufficiency  of  oxygen,  like  guncotton,  &c.,  with  which 
the  gases  vary  quantitatively  and  qualitatively  according  to  the  type  of  explosion  ;  in  such 
cases  the  volume  must  be  determined  directly. 

The  volume  of  gases  is  calculated  (see  vol.  i,  p.  34)  by  means  of  the  general  formula, 

70(1  +  0-00367  1)       .. 

vt-         —  p— 

where  Vf  is  the  required  volume  at  the  temperature  of  explosion  t,  V0  is  the  volume  at  0° 
and  760  mm.  pressure  (which  can  be  found  from  the  weight  of  the  gaj?es  formed),  and 
0-00367  is  the  coefficient  of  expansion  for  all  gases.  For  such  high  temperatures  and 
pressures,  however,  the  coefficient  of  expansion  is  rather  higher  than  that  resulting  from 
Gay-Lussac's  and  Boyle's  laws,  but  this  difference  is  compensated  for  by  the  somewhat 
higher  specific  heat  of  the  gas  at  high  temperatures,  in  consequence  of  which  more  than 
the  theoretical  quantity  of  heat  is  absorbed. 

The  pressure  of  the  gas  is  deduced  from  the  general  formula  given  above,  Vf  being 
diminished  by  the  volume  v  of  the  mineral,  non-gasifiable  residue  (in  the  case  of  dynamite 
or  other  mixtures),  so  that  : 

+  0-00367  Q 


° 


Vt-v 


with  nitroglycerine,  guncotton,  &c.,  v  =  0.  P  is  the  maximum  theoretical  force  of  an 
explosive,  starting  from  its  volume  (solid)  at  the  ordinary  temperature,  but  the  effect  of 
a  given  explosive  will  be  the  greater  as  its  density  increases,  that  is,  the  greater  the  weight 
for  the  same  volume  ;  and  for  guncotton,  for  example,  the  effect  will  be  the  greater  for 
the  same  volume,  the  more  it  is  compressed.  Thus  the  relative  specific  gravities  of 
different  explosives  are  of  importance,  and  in  fact  fulminate  of  mercury,  which  has  a  high 
specific  gravity  (five  times  that  of  ordinary  powder  and  three  times  that  of  nitroglycerine), 
has  a  maximum  rapidity  of  reaction  and  is  the  most  powerful  detonator,  being  capable  of 
exerting  a  force  of  about  27,000  kilos  per  square  centimetre  (atmospheres),  this  being 
about  treble  that  given  by  any  other  known  explosive. 

In  practice,  pressures  higher  than  any  imaginable  may  be  attained  when  the  volume 
occupied  by  a  given  weight  of  explosive  in  a  closed  vessel  is  less  than  the  critical  volume  of 
the  gas  developed,  since  this  critical  volume  (vol.  i,  p.  28)  cannot  be  diminished  by  any 
pressure,  however  great.  If  we  term  charging  density  the  ratio  between  the  weight  of  the 
explosive  in  grammes  and  the  volume  in  cubic  centimetres  occupied  by  it  in  absolutely 
filling  its  envelope  (as  though  it  were  liquid  or  fused),  this  charging  density  corresponds 
with  the  specific  gravity  of  the  explosive  ;  if  this  density  equals  or  exceeds  the 

reciprocal  of  the  limiting  volume  (  -  I   into  which  the  gases  developed  (critical  volume) 

\v' 

can  be  compressed,  the  pressure  attained  will  be  infinitely  great  and  will  rupture  any 
enclosing  vessel,  no  matter  how  resistant  it  may  be.  The  reciprocal  of  the  critical  volume 
of  the  gases  produced  in  the  explosion  is  termed  the  critical  specific  volume  (or  limiting 
density),  and  comparison  of  this  with  the  density  of  charge  leads  to  consequences  of  practical 
importance. 

Limiting  density  Specific  gravity  of 

of  the  gases  the  explosive 

Black  powder     .         .  .  .2-05  ..  1-75 

Nitroglycerine     .          .  .1-40  .  .  1-60 

Powdered  guncotton    .  .  .     1-16  ..  1-20 

Picric  acid  .          .  .  .1-14  ..  1-80 

Fulminate  of  mercury  .  .3-18  .  .  4-42 

.Thus,  black  powder  has  a  charging  density  (or  specific^gravity)  of  1-75  to  1-82,  which 
does  not  reach  the  limiting  density,  so  that  even  if  it  is  exploded  in  its  own  volume  it  does 
not  break  the  envelope  if  the  latter  is  strong  enough  to  withstand  the  pressure  developed, 
namely,  about  29,000  kilos  per  square  centimetre.  For  granular  powder,  the  density  of 
which  is  1  ,  the  pressure  is  only  6000  kilos.  The  real  density  (specific  gravity)  of  compressed 
guncotton  is  1  -2,  that  of  nitroglycerine  1  -6,  and  that  of  picric  acid  1  -8,  all  of  these  being 


VELOCITY    OF    EXPLOSION  219 

superior  to  the  limiting  densities  of  the  corresponding  gases  ;  so  that  when  they  explode 
in  their  own  volume,  all  of  these  explosives  burst  the  most  resistant  envelope,  and,  in  such 
cases,  the  velocity  of  the  explosive  wave  becomes  infinitely  great.  Fulminate  of  mercury, 
although  it  has  the  high  limiting  density  3-18  (owing  to  the  low  critical  volume,  v),  has  a 
specific  gravity  of  4-42  (to  which  the  density  of  charge  approximates)  and  behaves  like 
nitroglycerine,  &c. 

As  it  is  difficult  to  calculate  a  priori  the  pressures  exerted  by  explosives,  it  is  preferable 
to  determine  them  relatively  by  measuring  certain  effects  of  the  ga?es  at  the  instant  of 
explosion  ;  this  is  done,  for  instance,  by  observing  the  crushing  or  deformation  of  small 
cylinders  of  copper  or  lead,  which  are  termed  crushers  (Fig.  179). 

The  total  pressure  depends  on  the  character  of  the  explosive  and  on  the  nature  of  the 
explosion  (see  later),  but  more  especially  on  the  density  of  charge. 

The  specific  pressure  of  an  explosive  is  a  constant  (a),  given  by  the  ratio  of  the  pressure 

P 

(p)  to  the  corresponding  density  of  charge  (d)  of  the  explosive  itself  :  a  —  •= .    This  specific 

a 

pressure  a  is  characteristic  of  any  explosive  and  expresses  the  pressure  developed  ~by  unit 
weight  (1  grm.)  of  an  explosive  in  unit  volume.  The  specific  pressure  is  not  always  the 
maximum  pressure  that  can  be  exerted,  this  depending, 
as  we  have  seen,  on  the  charging  density  in  its  relation 
to  the  critical  volume. 

Velocity  of  reaction.     The  duration  of  the  explosion  is 
of  great  importance,  since  on  it  depends  the  greater  or  FIG.  179. 

less  utility  of  the  explosive  for  different  purposes.     The 

more  rapid  the  explosion  the  better  is  the  heat  developed  utilised,  so  that  this  can  be 
used  almost  entirely  in  heating  and  expanding  the  gases  and  so  increasing  the  pressure 
considerably.  If,  however,  the  reaction  is  slow,  a  large  portion  of  the  heat  is  dissipated 
by  radiation  and  conduction. 

Explosives  with  an  extremely  rapid  reaction  produce  special  effects,  as  they  shatter 
the  envelope  or  rock  in  immediate  contact  with  the  explosive  into  minute  fragments — 
an  effect  often  not  desired.  These  are  termed  shattering  or  detonating  explosives  and  their 
properties  are  utilised  in  certain  cases,  as,  for  example,  where  a  small  cavity  is  to  be  made 
in  a  rock  so  that  a  large  quantity  of  a  progressive  explosive  may  be  subsequently  introduced. 

If  the  reaction,  although  rapid,  is  not  instantaneous,  the  explosion  produces  other 
effects,  for  instance,  the  cleaving  of  large  stones  or  rocks  and  the  projection  of  fragments 
nearer  to  the  exolosive  ;  this  progressive  or  rending  action  is  the  effect  usually  desired 
by  miners. 

According  as  the  gasification  takes  place  more  or  less  instantaneously  (and  the  one  or 
the  other  effect  can  be  obtained  with  the  same  substance  by  adding  inert  materials  to,  say, 
dynamite,  or  mixing  paraffin  with  guncotton),  explosives  are  more  or  less  shattering. 
Thus,  panclastite  is  more  shattering  than  guncotton,  the  latter  more  than  dynamite, 
and  this  more  than  smokeless  powder,  which  is  a  progressive  explosive. 

Many  substances  explode  only  with  detonators  (of  fulminate  of  mercury)  and  the 
cause  of  the  explosion  in  such  cases  is  not  only  the  high  temperature  produced  by  the 
explosion  of  the  detonator,  but  more  especially  the  great  immediate  pressure  resulting 
from  the  instantaneous  production  of  gas,  this  pressure  and  the  sudden  shock  provoking 
the  decomposition  of  the  molecules  of  the  explosive  (Berthelot,  Abel,  Vieille).  The 
duration  of  explosion  or  of  gasification  of  the  detonator  is  500  times  less  than  that  of  the 
explosive  material,  and  the  greater  relative  amount  of  heat  developed  in  "a  certain  time  by 
detonators  explains  their  greater  shattering  power  compared  with  that  of  progressive 
.  explosives.  The  most  highly  shattering  materials  are  :  fulminate  of  mercury,  panclastite, 
compressed  guncotton,  and  nitroglycerine.  The  duration  of  reaction  for  detonators 
is  only  about  T  ^  0  of  a  second,  the  extraordinary  effect  of  these  explosives  being  due  to 
the  enormous  amount  of  energy  developed  (1600  Cals.  for  nitroglycerine)  in  this  short  time 
and  in  the  small  space  containing  them.1 

1  The  velocity  of  combustion  (or  of  deflaaratron)  is  sharply  distinguished  from  the  velocity  of  the  explosive 
reaction  and  is  made  use  of  it  in  certain  cases,  e.g.  in  the  throwing  of  projectiles  (expansive  and  progressive  action)j 
The  velocity  of  combustion  of  explosives  depends  on,  and  increases  with  increase  of,  the  pressure  at  which  they 
decompose.  Another  factor  influencing  the  mode  of  combustion  of  explosives  is  the  maximum  velocity  with 
which  the  pressure  develops. 

The  exponent  of  the  power  of  the  pressure,  which  admits  <  f  passing  from  one  value  to  the  other  in  the  increase 


220  ORGANIC  CHEMISTRY 

As  has  been  already  stated,  the  shattering  effect  of  a  substance  is  rendered  evident  by 
exploding  a  few  grammes  of  it  on  a  cylinder  of  metal  (crusher)  and  the  actions  of  different 
explosives  are  compared  by  means  of  these  deformed  and  disfigured  crushers.  Fig.  180  B 
shows  a  leaden  cylinder  before  the  explosion,  whilst  A  shows  the  same  cylinder  after  10  grms. 
of  dynamite  (a  progressive  explosive)  have  been  exploded  on  it  and  C  the  result  of  the 
explosion  of  10  grms.  of  panclastite  (from  nitrotoluene). 

One  and  the  same  explosive  substance  may  be  made  to  give  either  a  shattering  or  a 
progressive  effect  by  varying  the  velocity  of  the  reaction,  this  usually  depending  on  the 
power  of  the  initial  shock  which  causes  the  explosion.  The  more  powerful  the  initial  shock 
the  greater  is  the  amount  of  kinetic  energy  transformed  into  heat  and  hence  the  higher 
the  temperature  developed  ;  therefore,  also,  the  greater  is  the  pressure  of  the  resultant 
gases  and  the  more  rapid  and  powerful  the  effect  of  the  explosive.  The  effects  vary 
considerably  with  the  manner  in  which  the  explosion  is  induced  ;  thus,  if  a  flame  is  brought 
near  to  non-compressed  guncotton,  the  latter  burns  rapidly  but  does  not  explode  ;  whilst 
if  it  is  compressed  and  subjected  to  the  action  of  a  cap  (detonator)  of  fulminate  of  mercury, 

a  real  and  very  powerful  ex- 
plosion occurs  ;  similar  pheno- 
mena are  observed  with  nitro- 
glycerine and  dynamite.1 

DETERMINATION  OF 
THE  EXPLOSION.  In  order 
to  induce  the  explosive  re- 
action of  a  substance,  it  is 
sufficient  to  bring  it  at  a  single 
point  to  a  certain  initial  decom- 
A  position  temperature  (by  percus- 

FIG.  180.  sion,  detonation,  &c.),  the  sharp 

decomposition  at  this  point  then 

producing  a  new  shock  which  heats  the  neighbouring  points  to  the  decomposition 
temperature,  and  so  on,  the  explosion  being  thus  communicated  to  the  whole  mass  by  a 
true  explosive  wave,  which  is  enormously  more  rapid  than  simple  burning.  From  this  will 
be  understood  the  great  importance  of  detonators,  which  do  not  serve  merely  for  ignition  ; 
and  the  difference  will  also  be  apparent  between  an  ordinary  explosion  by  ignition  and 
percussion  and  that  induced  by  fulminate  of  mercury  detonators. 

When  the  phenomenon  of  explosion  is  studied  more  closely,  it  becomes  evident  that 
the  gases  produced  at  the  point  of  ignition  tend  to  expand  and  hence  to  diminish  the 
pressure  at  that  point  and  also  the  rapidity  of  explosion,  but  if  this  initial  expansion 
is  impeded  the  pressure  and  hence  the  velocity  of  decomposition  increase  rapidly.  In 
practice  miners  obtain  this  effect  by  filling  the  cavity  containing  the  explosive  with  a 

of  the  pressure,  is  called  the  modulus  of  progressirity,  and  serves  to  characterise  the  various  explosives.  Thus, 
this  modulus  varies  from  1-25  to  1-50  for  black  powders  and  from  1-86  to  1-87  for  smokeless  powders,  whilst  that 
of  picric  acid  is  2-82  and  that  of  "Earner's  explosive  (12  per  cent,  of  dinitronaphthalene  -f  88  per  cent,  of  ammonium 
nitrate)  3-25.  As  will  hence  be  seen,  these  last  two  explosives  have  the  dangerous  property  of  furnishing  accidental 
superpressures,  owing  to  undulatory  phenomena  which  always  accompany  the  combustion  of  substances  in- 
flammable with  difficulty.  In  smokeless  powders,  the  moderate  progressivity  compared  with  the  great  power 
constitutes  a  valuable  safeguard  in  their  use  in  firearms  ;  in  this  they  are  surpassed  only  by  black  powders,  which 
are,  however,  much  less  powerful. 

1  The  percussive  force  (kinetic  energy)  of  an  explosive  serves  best  to  establish  the  shattering  power  and  is  calcu- 
lated by  C.  E.  Bichel  by  means  of  the  formula  — -,  where  m  denotes  the  mass  of  the  gases  formed  in  the  explosion, 

or  the  weight  of  the  explosive,  divided  by  9-81  and  v  is  the  velocity  of  detonation  (i.e.  the  time  elapsing  from  the 
beginning  of  the  explosion  to  its  completion  throughout  the  whole  mass).  For  1  kilo  of  an  explosive  gelatine 
(92  per  cent,  of  nitroglycerine  and  8  per  cent,  of  collodion  cotton)  with  the  charging  density,  1-63,  Bichel  gives 
a  velocity  of  detonation  of  7700  metres  per  second,  so  that  the  percussive  force  in  absolute  units  will  be  : 
1  X  77002 
"9^1  x  2  =  3>021'916  kilogram-metre-seconds  ;  for  black  powder  (with  a  charging  density  1-04)  exploded  under 

the  same  conditions  in  a  closed  vessel  with  a  detonating  cap,  the  velocity  of  detonation  is  300  metres  per  second, 

1  x  300« 
so  that  9  gl  x  2  =  4587  kilogram-metre-seconds ;  for  kieselguhr  dynamite  (35  per  cent,  nitroglycerine)  the  velocity 

of  detonation  is  6818,  and  hence  the  percussive  force,  2,369,272  kilogram-metres  per  second ;  for  a  gdatine-dynamite 
(63-5  per  cent.1  nitroglycerine,  1-5  per  cent,  collodion  cotton,  27  per  cent,  sodium  nitrate,  8  per  cent,  wood  meal), 
with  a  charging  density  of  1  67,  the  velocity  of  detonation  is  7000  and  the  percussive  force  2,497,452  ;  for  trinitro- 
toluene, with  a  [charging  density  of  1-55,  the  velocity  was  7618,  and  the  percussive  force  2,957,896  ;  guncotton, 
with  a  charging  density  of  1-25,  had  a  velocity  of  6383,  the  percussive  force  being  2,076,589  ;  and  picric  acid,  with 
a  charging  density  of  1-55,  gave  the  velocity  of  detonation  8183,  and  the  percussive  force  3,412,920 'kilogram- 
metre-seconds. 


EXPLOSION    BY    INFLUENCE  221 

tamping  of  earth  or  stone.  The  same  end  may  also  be  attained  by  increasing  considerably 
the  mass  of  the  explosive  and  the  surface  of  ignition,  and  this  explains  why  certain  sub- 
stances burn,  without  exploding,  in  small  quantities  (guncotton,  nitroglycerine,  &c.),  or 
when  the  ignition  is  confined  to  a  limited  area,  whilst  a  powerful  explosion  may  occur 
when  a  large  quantity  of  explosive  is  used  or  when  it  is  surrounded  by  a  source  of  considerable 
heat. 

For  shattering  explosives  (e.g.  fulminate  of  mercury)  no  tamping  is  used,  since  the 
reaction  is  so  rapid  that  the  atmospheric  pressure,  that  is,  the  air  itself  with  its  inertia, 
is  sufficient  to  maintain  the  pressure  of  the  gases.  Even  fulminate  of  mercury,  if  ignition 
is  effected  by  an  electric  contact  (which  heats  a  platinum  wire  to  redness)  and  under  an 
evacuated  bell-jar,  burns  without  exploding,  thus  confirming  the  tamping  action  of  the 
air  in  the  case  of  detonators  and  even  of  ordinary  explosives  ;  in  fact,  if  a  roll  of 
dynamite  is  exploded  on  a  bridge,  the  latter  is  cut  in  two  owing  to  the  tamping  action 
of  the  air. 

The  explosive,  wave  produced  in  the  explosion  of  gaseous  mixtures  and  of  liquids  and 
solids  is  only  slightly  related  to  waves  of  sound.  The  latter  is  transmitted  from  crest  to  crest 
with  but  little  kinetic  energy,  with  a  small  excess  of  pressure  and  with  a  velocity  depending 
only  on  the  nature  of  the  medium  in  which  it  is  propagated  and  of  equal  magnitude  for  all 
kinds  of  vibrations.  The  explosive  wave,  on  the  contrary,  propagates  the  chemical 
transformation  through  the  mass  of  the  explosive  substance,  communicating  from  point 
to  point  of  the  decomposing  system  an  enormous  amount  of  potential  energy  and  a  great 
excess  of  pressure.  The  sound-wave  is  propagated  in  a  mixture  of  hydrogen  and  oxygen 
with  a  velocity  of  514  metres  per  second  at  0°,  but  the  velocity  of  the  explosive  wave  in  the 
same  mixture  (exploded  at  a  point)  is  2841  metres. 

With  guncotton,  the  velocity  of  this  wave  varies  from  3800  to  5400  metres  per  second 
according  to  the  compression  ;  with  nitroglycerine  it  is  1300,  with  dynamite  2700,  with  picric 
acid  6500,  and  with  nitromannitol  7700  metres  per  second.  This  velocity  depends  only 
on  the  nature  of  the  explosive  and  not  on  the  pressure,  but  it  varies  to  some  extent  with 
the  nature  of  the  envelope.  For  instance,  in  a  rubber  tube  having  a  thickness  of  3-5  mm. 
and  an  internal  diameter  of  5  mm.  and  covered  with  cloth,  ethyl  nitrate  gives  a  velocity 
of  1616  metres  ;  whilst  in  glass  tubes  of  various  diameters  and  thicknesses  the  value  is 
1890  to  2480  metres.  The  propagation  of  the  explosive  wave  bears  no  relation  to  that 
of  ordinary  combustion  (which  is  much  slower).  The  former  occurs  when  the  inflamed 
gaseous  molecules  acquire  the  maximum  velocity  or  energy  of  translation,  i.e.  act  with 
the  whole  of  the  heat  developed  in  the  chemical  reaction. 

Explosion  by  Influence.  If  a  long  row  of  dynamite  cartridges  are  arranged  on  a  flat 
solid  at  distances  of  30  cm.  or  on  a  metal  disc  at  a  distance  of  70  cm.,  explosion  of  the  first 
with  a  fulminate  cap  results  in  the  rapid  and  successive  explosion  of  the  remaining  ones 
simply  by  influence  and  without  the  need  of  detonators  or  fuses.  Air  does  not  conduct 
the  wave  of  explosive  influence  as  well  as  solids,  and  if  the  cartridges  are  suspended  in  the 
air  by  wires  such  explosion  by  influence  does  not  occur.  Water  conducts  the  explosive 
wave  to  a  certain  distance,  but  the  influence  gradually  diminishes  with  increasing  distance 
from  the  centre  of  explosion  (there  have  been  cases  in  which  the  shock  of  a  large  charge  of 
guncotton  has  exploded  neighbouring  torpedoes  ;  to  avoid  these  inconveniences,  so-called 
safety  explosives  are  now  used). 

These  explosive  waves  are  first  propagated  through  the  explosive  itself,  not  by  a  single 
shock — which  would  gradually  weaken  as  it  advanced — but  by  a  very  rapid  series  of  such 
shocks  produced  by  the  propagation  of  the  explosion  from  point  to  point  of  the  whole  mass 
of  the  explosive,  the  kinetic  energy  being  thus  regenerated  along  the  whole  course  of  the 
wave  in  the  exploding  substance. 

An  explosive  wave  is  thus  distinguished  from  an  ordinary  sound-wave  by  the  fact 
that  the  latter  becomes  enfeebled  as  it  advances,  whilst  the  former  is  characterised  by  the 
uniformity  of  the  energy  transmitted  from  point  to  point  by  a  series  of  numerous  and 
successive  explosions  throughout  the  exploding  mass.  Only  the  last  of  these  explosions 
is  transmitted  with  its  energy  to  the  surrounding  air  and  to  the  matter  on  which  the 
explosive  rests,  and,  since  it  is  no  longer  reinforced  (by  other  shocks),  it  weakens  as  it  becomes 
more  remote.  Hence  explosion  by  influence  is  not  due  to  the  fact  that  the  distant  explosive 
transmits  or  propagates  the  explosive  wave  through  its  own  mass,  but  is  owing  to  the  arrest 
and  transformation,  at  the  point  of  impact,  of  the  mechanical  energy — it  being  capable 


222  ORGANIC    CHEMISTRY 

of  similar  (but  not  all)  waves — into  heat  energy,  able  to  cause  decomposition  and  explosion 
of  the  substance  itself. 

The  effects  of  large  charges  of  dynamite  (25  to  1000  kilos)  when  freely  exploded  are 
dangerous  to  buildings  and  to  life  for  a  distance  of  500  metres  and  are  felt  as  far  away  as 
3  kilometres  (L.  Thomas,  1904). 

CLASSIFICATION  OF  EXPLOSIVES.  Explosives  are  to-day  so  numerous  and  are 
prepared  from  such  different  mixtures  and  serve  such  a  variety  of  purposes  that  a 
rigorous  or  rational  classification  is  difficult  or  impossible.  Also  with  a  large  number 
of  classes  there  would  be  many  substances  which  might  belong  to  more  than  one  of 
them. 

It  will  hence  be  preferable  to  limit  ourselves  to  a  description  of  the  various  explosives 
without  any  prearranged  classification.  They  will  be  taken  in  the  following  order  :  (1) 
Dynamites  with  a  basis  of  nitroglycerine;  (2)  Nitrocellulose ;  (3)  Various  smokeless  powders ; 
(4)  Picrate  powders  ;  (5)  Explosives  of  the  Sprengel  type  (the  components  are  explosive  only 
when  mixed)  ;  (6)  Sundry  explosives  ;  (7)  Black  nitrate  and  other  powders  ;  (8)  Chlorate  and 
Perchlorate  powders. 

NITROGLYCERINES 

This  name  is  given  improperly  to  nitric  esters  of  glycerine  since  they  do  not  contain 
true  nitro-groups  (N02)  united  directly  with  carbon  as  is  often  the  case  in  benzene  deriva- 
tives. On  the  contrary,  the  union  is  effected  through  an  intermediate  oxygen  atom,  so  that 
these  compounds  should  rather  be  called  nitrates  of  glycerine. 

Being  a  trihydric  alcohol,  glycerine  can  form  three  such  compounds,  the  only  one  known 
until  quite  recently  being  trinitroglycerine  containing  18-5  per  cent,  of  nitrogen  and  having 
very  considerable  industrial  importance. 

In  1903,  Mikolajczak  prepared  also  pure  DINITROGLYCERINE,  C3H5.OH(ONO2)2, 
containing  15-4  per  cent,  of  nitrogen,  and  he  proposed  to  use  it  as  an  explosive,  as  it 
possesses  almost  all  the  ballistic  advantages  of  trinitroglycerine  and  is  not  easily  frozen  ; 
it  is,  however,  very  hygroscopic  and  readily  soluble  in  water  and  in  acids. 

Dinitroglycerine  is  prepared  by  nitrating  100  parts  of  glycerine  with  400  parts  of  nitric 
sulphuric  mixture  containing  8  to  12  per  cent.  H2O,  60  to  70  per  cent.  H2S04,  and  15  to  32  per 
cent.  HNO3  ;  at  the  end  of  the  reaction,  the  mass  is  poured  into  an  equal  volume  of  water, 
and  the  acid  neutralised  with  calcium  carbonate,  when  the  dinitroglycerine  separates  as  a 
dense,  floating  oil.  During  the  reaction,  the  temperature  is  maintained  at  18°  to  20° 
by  cooling  with  ice.  Dinitroglycerine  is  also  formed  by  dissolving  trinitroglycerine  in  sul- 
phuric acid  and  then  diluting  the  solution  with  a  little  water.  In  whatever  way  it  is  pre- 
pared (e.g.  by  treating  1  part  of  glycerine  with  2  parts  of  sulphuric  acid,  separating  by  means 
of  lime  the  glycerinedisulphuric  acid  formed  and  treating  this  with  nitric  acid,  as  proposed 
by  Escales  and  Novak,  1906),  a  mixture  of  the  two  possible  isomerides  is  always  obtained  : 
dinitroglycerine  K  (i.e.  ay-),  N03-CH2-CH(OH)-CH2-N03,  and  dinitroglycerine  F  (i.e. 
a  (3-),  NO3  •  CH2  •  CH(NO3)  •  CH2 .  OH,  which  was  studied  by  W.  Will  (1908).  The  mixture 
forms  an  almost  colourless,  faintly  yellow  oil,  sp.  gr.  1-47  at  15°,  which  freezes  at  below 
—30°  to  a  glassy  mass,  this  distilling  almost  undecomposed  at  146°  under  reduced  pressure 
(15  mm.)  ;  at  15°  it  is  soluble  to  the  extent  of  8  per  cent,  in  water  and  at  50°  to  the  extent 
of  10  per  cent.  In  dilute  sulphuric  or  nitric  acid  it  dissolves  in  all  proportions  and  by 
sulphuric  acid  (up  to  70  per  cent.)  it  is  transformed  into  mononitroglycerine  and  then  into 
glycerine.  It  is  very  hygroscopic  and,  when  dry,  dissolves  or  gelatinises  nitrocellulose 
(guncotton  or  collodion-cotton)  very  well.  The  two  isomerides  can  be  separated  by  taking 
advantage  of  the  fact  that,  in  the  air,  the  F  compound  absorbs  3  per  cent,  of  water  and  is 
transformed  into  a  crystalline  hydrate,  3(C3H607N2)  +  H20,  whilst  the  other  remains 
liquid.  The  J^-form  gives  a  nitrobenzoyl-derivative  melting  at  81°,  the  corresponding 
compound  of  the  Jf-isomeride  melting  at  94°.  In  the  dry  state,  the  dinitroglycerines 
are  as  useful  for  explosives  as  the  trinitro -compound,  but  when  moist  they  are  much 
inferior.  A  mixture  of  50  per  cent,  dinitro-  and  50  per  cent,  trinitro -glycerine  freezes 
below  —20°. 

Of  MONONITROGLYCERINE,  C3H5(OH)2.NO3)  the  pure  a-  and  /3-isomerides  are 
known  (W.  Will,  1908).  These  are  not  true  explosives  and  dissolve  to  the  extent  of  70  per 
cent,  in  water.  The  n-compound  melts  at  58°  and  boils  at  155°  to  160°  under  15  mm, 
pressure. 


NITROGLYCERINE  223 

Nitrochlorhydrin,  C3H5C1(NO3)2,  and  Tetranitrodiglycerine  (see  p.  184)  have  also 
been  proposed  as  non-congealing  explosives,  but  better  still  for  this  purpose  are  the 
nitroacetins  (V.  Vender)  (see  later).1 

CH2O-NO2 

TRINITROGLYCERINE,  CHO-N02  or  C3H5(O.N02)3. 

CH2O.NO2 

This  was  discovered  in  1846  by  Ascanio  Sobrero,2  who  called  it  Pyroglycerine  and 
established  its  explosive  properties  but  regarded  its  industrial  manufacture  as  too  dangerous. 
Its  chemical  composition  was  determined  by  Williamson  in  1854.  At  first  it  was  used 
only  in  small  doses  as  a  medicine,  owirg  to  its  marked  power  of  inducing  dilatation  of  the 
blood-vessels.  Later,  after  various  unavailing  attempts,  Alfred  Nobel  succeeded  in  applying 
it  industrially,  and  in  1863  established  two  nitroglycerine  factories  in  Sweden,  these  rapidly 
prospering  owing  to  the  great  demands  of  various  nations  for  this  powerful  explosive. 
Nevertheless,  owing  to  the  neglect  of  precautions  by  consumers  in  the  handling  of  nitro- 
glycerine, various  terrible  explosions  occurred  which  almost  resulted  in  the  abandonment 
and  prohibition  of  this  substance.  Fortunately  just  at  this  time  Nobel  discovered  a  very 
happy  solution  of  the  problem  which  completely  eliminated  this  danger,  by  mixing  the 
nitroglycerine  with  inert  substances  (kieselguhr  or  infusorial  earth)  and  thus  obtaining 
dynamite,  this  being  to-day  at  the  head  of  the  great  explosives  industry. 

PROPERTIES.  When  pure  it  is  a  dense  almost  colourless  or  faintly 
yellow  liquid  of  sp.  gr.  1-6  at  15°,  and  when  it  freezes  its  density  increases  by 
almost  one-tenth,  it  is  odourless  and  has  a  sweetish,  burning  taste.  It  is 
almost  insoluble  in  water  (0-16  to  0-20  per  cent,  being  dissolved  at  15°),  is 
not  hygroscopic,  and  dissolves  easily  in  concentrated  alcohol,  ether,  benzene, 
chloroform,  glacial  acetic  acid,  toluene,  nitrobenzene,  acetone,  olive  oil,  and 
concentrated  sulphuric  acid,  and  to  a  less  extent  in  nitric  acid  and  still  less  in 
hydrochloric  acid  ;  it  is,  however,  insoluble  in  carbon  disulphide,  glycerine, 
petroleum,  vaseline,  turpentine,  benzine,  and  carbon  tetrachloride.  In  solu- 
tion it  will  not  explode.  It  evaporates  spontaneously  and  in  very  small 
quantities  even  at  50°,  and  if  gradually  heated  to  109°  it  begins  to  decompose 
with  evolution  of  brown  nitrous  vapours. 

Its  specific  heat  is  0-356,  and  its  heat  of  solidification  23  to  24  Cals. 

Dinitromonochlorhydrin  is  obtained,  according  to  F.  Roewer  (1906),  by  nitrating  the  monochlorhydrin  in 
the  same  manner  as  glycerine  is  nitrated  (see  later),  and  is  then  quickly  separated  from  the  top  of  the  nitric-sulphuric 
acid  mixture  as  an  oil  which  is  easily  rendered  stable  by  washing  with  water  and  soda.  It  forms  a  faintly  yellow, 
mobile  oil  of  aromatic  odour,  sp.  gr.  1-541  at  15°,  soluble  in  alcohol,  ether,  acetone,  or  chloroform,  but  insoluble 
in  water  and  in  acids.  At  180°  it  gives  yellow  vapours,  and  at  190°  boils  without  detonation  or  deflagration, 
and  with  only  slight  decomposition  ;  under  a  pressure  of  15  mm.  it  distils  unchanged  at  121°  to  123°  as  an  almost 
colourless  oil.  It  is  much  more  stable  towards  pressure  than  nitroglycerine,  although  possessing  almost  the  same 
explosive  properties.  It  does  not  freeze  even  at  —  30°  and  is  not  hygroscopic.  It  dissolves  nitrocellulose,  forming 
explosive  gelatine,  and  mixes  readily  with  nitroglycerine,  giving  non-congealing  dynamites  (with  5  to  20  per  cent, 
of  nitrochlorhydrin,  Ger.  Pat.  183,400),  these  being  prepared  by  nitrating  directly  -a  mixture  of  glycerine  and 
chlorhydrin.  In  order  to  avoid  the  inconvenient  effects  on  miners  of  the  hydrochloric  acid  formed  in  the  explosion 
of  nitrochlorhydrin,  potassium  nitrate  is  added  ;  during  the  explosion  this  is  transformed  into  potassium  carbonate, 
which  neutralises  the  acid. 

Dinitroacetylglycenne,  C3H6(ONO2)2(OCOCH8),  is  obtained  by  nitrating  the  monoacetin  in  the  same 
apparatus  as  is  used  for  nitroglycerine,  but  using  an  acid  mixture  containing  a  preponderance  of  nitric  acid,  e.g. 
65  per  cent.  HNO,  and  35  per  cent.  H-jSO,.  The  dinitroacetylglycerine  being  somewhat  soluble  in  water,  it  is 
lost  to  some  extent  during  the  washing.  It  is  a  yellowish  oil,  sp.  gr.  1-45  at  15°,  and  is  soluble  in  alcohol,  acetone, 
ether,  nitroglycerine,  or  nitric  acid,  and  almost  or  quite  insoluble  in  water,  benzene,  or  carbon  disulphide.  It 
contains  12-5  per  cent,  of  nitrogen  and  with  double  its  weight  of  nitroglycerine  gives  a  mixture  with  16-5  per  cent,  of 
nitrogen,  which  has  a  lower  freezing-point  (below  —20°)  than  any  other  mixture  of  these  substances.  It  serves 
well  for  preparing  non-congealing  dynamites,  and  as  it  dissolves  nitrocellulose  easily  it  can  be  used  for  gelatinising 
smokeless  powders. 

Uinitroformylglycerine,  C3H6(ONO2)Z(O- CHO),  is  prepared  in  a  similar  manner  to  the  preceding  com- 
pound, or,  together  with  nitroglycerine,  by  nitrating  the  product  obtained  by  heating  2  parts  of  glycerine  with 
1  part  of  oxalic  acid  for  20  hours  at  140°.  Nitroformin  and  nitroacetin  have  explosive  powers  rather  inferior 
to  that  of  nitroglycerine. 

1  Ascanio  Sobrero  was  born  at  Casalmonferrato  on  October  12,  1812.  He  first  studied  medicine  and  then 
chemistry.  In  1840  he  went  to  complete  his  chemical  studies  in  the  laboratory  of  the  celebrated  Pelouze  at  Paris, 
where  he  stayed  two  years,  and  in  1843  he  worked  in  Liebig's  laboratory  at  Giessen.  In  1845  he  became  Professor 
of  Applied  Chemistry  at  Turin,  where  he  taught  until  1883.  He  died  on  May  26,  1888,  after  a  modest  life,  during 
which  he  filled  various  honorary  social  positions.  It  was  always  his  aim  that  science  should  not  be  made  a  pretext 
or  means  of  dishonorable  undertakings  or  of  business  speculations. 


224  ORGANIC    CHEMISTRY 

At  a  red  heat  it  evaporates  without  decomposing,  but  if  it  begins  to  boil 
vigorously  during  the  heating,  there  is  danger  of  explosion.  According  to 
Champion,  pure  nitroglycerine  in  small  quantities  boils,  giving  yellow  vapours, 
at  185°,  evaporates  slowly  at  194°,  and  rapidly  at  200°,  burns  quickly  at  218° 
and  detonates  with  difficulty  at  241°,  violently  at  257°,  feebly  at  267°,  and 
feebly  with  flame  at  287°  (being  in  the  spheroidal  state). 

When  heated  in  small  quantities  in  the  Bunsen  flame,  it  burns  without 
exploding,  and  if  spread  in  a  thin  layer  on  paper  it  ignites  with  difficulty  and 
burns  only  partially.  Explosion  of  nitroglycerine  can  be  induced  either  by 
violent  percussion  at  a  temperature  of  250°,  or  by  energetic  detonation  (e.g. 
by  explosion  of  fulminate  of  mercury). 

Nitroglycerine  may  be  easily  supercooled  below  its  solidifying  point. 
Kast  (1906)  showed  that  nitroglycerine  represents  a  case  of  monotropic  allo- 
tropy  (see  also  vol.  i,  p.  191),  i.e.  it  has  two  freezing-points,  +  12°  and  +  13-5°, 
corresponding  with  different  crystalline  forms.1 

When  frozen,  nitroglycerine  explodes  with  more  difficulty  than  in  the 
liquid  form.  Pure  nitroglycerine  will  not  redden  blue  litmus  paper  or  turn 
starch  paste  and  potassium  iodide  blue,  unless  it  contains  free  acids  or  nitrous 
compounds  due  to  partial  decomposition. 

Impure  nitroglycerine  readily  decomposes  and  may  explode  spontaneously,  whilst  in 
the  pure  state  it  keeps  indefinitely.  A  sample  of  nitroglycerine  (200  grms.)  prepared  by 
Sobrero  in  1847  is  still  kept  under  water  in  the  Nobel  factory  at  Avigliana. 

When  decomposing,  nitroglycerine  turns  green  owing  to  the  formation  of  N20  and  N203 ; 
C02,  CO,  H2O,  N,  and  0  (see  also  p.  216)  are  also  successively  formed.  In  exploding, 
1  litre  of  nitroglycerine  produces  1298  litres  of  gas,  which,  at  the  temperature  of  explosion, 
occupies  a  space  of  10,400  litres. 

LIn  large  doses  nitroglycerine  is  poisonous  and  its  vapour  causes  headache  (especially 
at  the  back  of  the  head),  giddiness,  and  vomiting.  These  effects  are  produced  even  by 
working  with  or  simply  touching  nitroglycerine  and  are  cured  by  means  of  cold  compresses 
on  the  head,  by  breathing  fresh,  pure  air,  and  by  drinking  coffee  and  taking  suitable 
doses  of  morphine  acetate. 

Workmen  who  handle  the  nitroglycerine  paste  during  the  manufacture  of  the  various 
dynamites  become  habituated  to  it  in  two  or  three  days  and  afterwards  feel  no  ill -effects. 
Nitroglycerine  is  moderately  easily  decomposed  by  alcoholic  potassium  hydroxide  (with 
separation  of  glycerine),  and,  when  necessary,  this  reaction  is  employed  to  destroy  and 
render  harmless  small  quantities  of  nitroglycerine  ;  similarly  benches  or  floors  on  which 
nitroglycerine  is  spilt  are  washed  with  caustic  alkali  solutions  : 

C3H6(ON02)3  +  5KOH  =  KNO3  +  2KNO2  +  CH3.COOK  +  H-COOK  +  3H20  ; 

a  little  ammonia  is  also  formed.     With  reducing  agents  it  gives  ammonia  and  glycerine, 
whilst  with  concentrated  sulphuric  acid  it  yields  nitric  acid  and  glycerinsulphuric  acid. 

1  Both  nitroglycerine  and  dynamites  and  smokeless  powders  prepared  from  it  are  liable  to  solidify,  and  although 
they  are  then  more  stable  the  thawing  is  accompanied  by  danger,  and  when  not  carried  out  with  great  precautions 
has  often  led  to  fatal  explosions,  these  being  sometimes  caused  by  the  mere  rubbing  of  the  crystals.  Indications 
will  be  given  later  of  the  precautions  taken  in  magazines  to  prevent  freezing,  and  mention  may  be  made  here  of  the 
attempts  which  have  been  made  to  render  nitroglycerine  non-congealable.  As  early  as  1895  it  was  proposed  to  add 
nitrobenzene  to  nitroglycerine  to  lower  the  freezing-point,  and  later  the  use  of  orthonitrotoluene  was  suggested  ; 
but  the  practical  results  were  not  very  satisfactory  in  either  case,  the  depression  of  the  freezing-point  being  very 
small.  Substances  were  required  which  were  almost  as  explosive  as  trinitroglycerine,  and  were  insoluble  in  water 
and  stable  on  heating,  and,  in  addition,  were  good  solvents  for  nitrocelluloses  (for  making  smokeless  powders). 
These  conditions  were  well  satisfied  by  the  nitroformins  and  nitroacetins  tested  by  Nobel  as  early  as  1875  but 
rendered  practically  useful  in  1906  by  V.  Vender.  The  best  results  are  given  by  dinitromonoacetin  which  is  obtained 
from  the  monoacetin  of  glycerine  prepared  by  the  ordinary  method  used  for  esterifying  alcohols  with  acids  (see 
later,  Esters).  Forty  parts  of  the  monoacetin  are  introduced  slowly  into  a  mixture  of  100  parts  of  nitric  acid  (sp.  gr. 
1-530)  and  25  parts  of  oleum  or  Nordhausen  sulphuric  acid  (containing  25  per  cent,  of  free  SO 3,  see  vol.  i,  p.  275),  the 
mass  being  cooled  so  that  the  temperature  does  not  exceed  25°.  The  whole  is  then  poured  into  water  and  washed 
with  cold  and  afterwards  with  hot  (70°)  dilute  soda.  By  this  means  an  oil  is  obtained  having  sp.  gr.  1-45  and 
containing  12-5  per  cent,  of  nitrogen  ;  it  is  insoluble  in  water,  carbon  disulphide  or  benzene,  but  dissolves  un- 
changed in  nitric  acid,  nitroglycerine,  methyl  or  ethyl  alcohol,  acetone,  acetins,  &c.  Even  in  the  cold,  it  has 
considerable  solvent  and  gelatinising  power  for  collodion-cotton  and  guncotton  (with  13-4  per  cent,  of  nitrogen) 
and  the  resulting  explosive  gelatines  do  not  freeze  even  at  —20°.  Naukhorf  (1908)  has  proposed  the  addition  of 
nitromethane  or  nitroethane  to  dynamite  to  lower  its  freezing-point,  and  at  the  present  time  liquid  dinitrotoluene  is 
largely  used  for  the  same  purpose. 


MANUFACTURE    OF    NITROGLYCERINE     225 

Characteristic  Reactions.  According  to  Weber,  small  quantities  of  nitroglycerine  are 
detected  by  treatment  with  aniline  and  concentrated  sulphuric  acid  :  a  reddish  purple 
coloration  is  obtained  which  turns  green  on  addition  of  water.  To  establish  the  purity 
and  keeping  qualities  of  nitroglycerine,  the  nitrogen  is  determined  and  Abel's  heat  test 
carried  out  (see  later,  Testing  of  Explosives)  ;  if  it  is  satisfactory,  2  c.c.  of  it  withstands 
20  to  30  minutes'  heating  at  82°  without  giving  sufficient  nitrous  vapours  to  be  detectable 
by  means  of  starch  and  potassium  iodide  paper. 

This  reaction  is,  however,  given  by  nitroglycerine*  kept  for  a  few  days  at  a  temperature 
exceeding  45°,  or  for  a  long  time  below  this  temperature. 

PREPARATION.  It  is  obtained  by  the  action  of  a  mixture  of  nitric  and 
sulphuric  acids  on  glycerine  : 

C3H5(OH)3  +  3HN03  =  3H20  +  C3H5(N03)3. 

The  mono-  and  dinitro-compounds  are  probably  formed  as  intermediate 
products  of  this  reaction. 

The  presence  of  sulphuric  acid,  which  plays  no  apparent  part  in  the  change, 
is  usually  regarded  as  being  necessary  to  maintain  the  nitric  acid  at  a  high 
concentration,  i.e.  to  decompose  the  hydrates  formed  by  nitric  acid  with  the 
water  from  the  reaction  (KN03,  H20 — HN03,  3H20)  and  so  regenerate  mono- 
hydrated  nitric  acid,  which  acts  on  the  glycerine  (Kullgren,  1908).  If  the  func- 
tion of  the  sulphuric  acid  were  merely  to  fix  the  water,  phosphoric  acid  could 
be  used  in  its  place  ;  but  if  this  is  done  no  nitroglycerine  is  obtained. 

The  excess  of  the  nitric-sulphuric  mixture  which  is  always  used  helps  to 
produce  a  moderately  complete  separation  of  the  nitroglycerine,  which  has  a 
slightly  lower  density,  so  that  it  is  possible  to  recover  the  acids  employed. 
Although  nitroglycerine  is  soluble  in  sulphuric  or  nitric  acid  alone,  it  does  not 
dissolve  in  the  mixed  acids.  But  if  one  of  the  two  acids  is  in  large  excess,  a  con- 
siderable amount  of  nitroglycerine  remains  in  solution  and  is  lost.  In  the  nitra- 
tion, the  whole  of  the  glycerine  cannot  be  added  at  one  time,  since  sufficient 
heat  would  in  that  way  be  developed  to  produce  decomposition  and  explosion 
of  the  nitroglycerine  instantaneously  formed.  It  is  also  not  convenient  to 
reverse  the  operation,  that  is,  to  add  the  mixed  acids  gradually  to  the  glycerine, 
the  greater  density  of  the  latter  rendering  rapid  and  homogeneous  mixing 
difficult ;  it  is  hence  preferable  to  run  the  glycerine  slowly  into  the  acid  mixture 
and  to  keep  the  latter  continually  and  thoroughly  stirred  and  cooled. 

MANUFACTURE.  The  theoretical  proportions  of  the  reacting  substances  1  would  be 
100  parts  by  weight  of  glycerine  and  205-43  of  pure  nitric  acid,  the  theoretical  yield  of 
trinitroglycerine  being  then  246-74  parts.  But  on  a  large  scale  the  whole  of  the  nitric 
acid  does  not  come  into  immediate  contact  with  the  whole  of  the  glycerine,  and  it  is  hence 
better  to  use  a  slight  excess  of  nitric  acid  (240  parts  or  even  more)  ;  the  amount  of  sul- 
phuric acid  employed  always  exceeds  that  of  the  nitric  acid  (about  if  times).  In  modern 
factories  the  following  proportions  are  often  used  :  100  kilos  of  glycerine,  240  to  260  kilos 
of  nitric  acid  (98  per  cent.),  and  340  to  360  kilos  of  sulphuric  acid  (96  to  98  per  cent.). 

In  the  best  factories,  the  practical  yield  is  215  to  232  kilos  of  nitroglycerine  per  100 
of  glycerine,  but  in  some  cases  it  amounts  to  only  205  to  210  kilos.  Good  yields  are  obtained 
by  cooling  the  acid  mixture  during  nitration  by  means  of  solutions  from  cooling  machines, 
the  temperature  of  reaction  being  kept  down  to  about  10°. 

The  low  value  of  the  practical  compared  with  the  theoretical  yield  (246-7)  is  due  to  the 
fact  that  towards  the  end  of  the  reaction  there  is  very  little  free  nitric  acid  and  the  last 

1  The  prime  materials  used  in  the  manufacture  of  trinitroglycerine  should  be  subjected  to  rigorous  control ; 
the  glycerine  should  be  pure  and  distilled  and  should  satisfy  the  requirements  indicated  on  p.  188.  The  nitric  acid 
should  have  a  specific  gravity  of  1-500  (48°  B6.  or  about  95  per  cent.  HNO3)  and  should  not  contain  more  than 
1  per  cent,  of  nitrous  acid,  i.e.  it  should  not  be  yellow,  as  otherwise  an  increased  amount  of  heat  is  evolved 
during  nitration  and  the  yield  is  lowered.  The  sulphuric  acid  should  be  pure,  with  a  sp.  gr.  of  1-8405  (i.e.  at 
least  96  per  cent.  H2SO4)  and  acid  containing  more  than  0-1  per  cent,  of  arsenic  should  be  avoided  ;  lead  and 
iron  should  also  be  absent  as  they  might  lead  to  reduction.  When  nitrations  are  carried  out  with  nitric-sulphuric 
acids  almost  free  from  water  (1  to  2  per  cent.)  the  sulphuric  acid  is  replaeed  by  oleum  or  Nordhausen  acid  (see 
vol.  i,  p.  275),  i.e.  acid  containing  20  per  cent,  or  more  of  dissolved  sulphur  trioxide. 

«  15 


226 


ORGANIC    CHEMISTRY 


portions  of  glycerine  added  are  nitrated  only  with  difficulty  and  hence  remain  dissolved  in 
the  sulphuric  acid. 

The  mixture  of  nitric  and  sulphuric  acids,  which  is  prepared  separately,  is  ir.ade  by 
pouring  the  sulphuric  acid  slowly  into  the  nitric  acid  (not  vice  versa)  in  an  iron  vessel, 
the  mixture  being  kept  well  cooled  and  stirred.  With  this  procedure  there  is  no  danger 
of  the  acid  spurting,  and  no  production  of  nitrous  fumes,  since  the  development  of  heat 
is  gradual.  This  mixture  is  forced  by  means  of  elevators  (Montejus)  or  pulsometers 
working  with  compressed  air  (vol.  i,  p.  264)  into  tanks  which  feed  the  leaden  apparatus  in 
which  the  glycerine  is  nitrated. 

During  recent  years,  many  vitriol  and  explosives  works  have  made  considerable  use 
of  Kuhlmann  emulsors  (or  Mammoth  pumps)  for  raising  concentrated  acids,  which  are 
rendered  lighter  by  emulsification  with  air  (see  illustration,  vol.  i,  p.  265). 

The  leaden  nitration  apparatus  is  shown  in  Fig. 
181.  It  is  surrounded  by  a  wooden  jacket  inside 
which  water  circulates.  Inside  the  vessel  are  peri- 
pheral leaden  coils  through  which  large  quantities  of 
cold  water  are  continually  passed  by  means  of  the 
two  tubes  D.  The  tubes  C  lead  dry  compressed  air 
to  the  bottom  of  the  liquid,  which  is  thus  kept 
thoroughly  mixed.  The  tube  F  serves  as  exit  for 
the  air,  and  for  any  nitrous  vapours  which  may  be 
evolved  and  may  be  observed  through  the  window, 
/  ;  these  vapours  are  recovered  in  small  condensation 
towers  sprinkled  with  a  little  water.  The  cold  acid 
mixture  is  first  introduced  through  the  pipe  G.  The 
glycerine,  at  a  temperature  of  20°  to  25°  (if  colder  it 
would  be  too  viscous),  is  measured  in  the  reservoir, 
M,  and  is  passed,  by  means  of  compressed  air  supplied 
through  O,  slowly  into  the  tube  H,  and  thence  into 
a  perforated  circular  pipe  at  the  bottom  of  the  appa- 
ratus. Two  thermometers,  E,  show  the  temperature 
of  the  reacting  mass  at  any  moment. 

The  bottom  of  the  apparatus  is  slightly  inclined 
and  at  the  lowest  part  is  inserted  a  large  stoneware 
tap,  K,  with  an  ebonite  screw  containing  an  aperture 
of  at  least  5  cm.  It  is  convenient  to  have  two  of 
these  taps  so  that,  in  case  of  danger,  the  whole  of 
the  mass  may  be  rapidly  discharged  into  a  vessel  of 
water  underneath  (drowning  of  the  nitroglycerine). 
In  such  an  apparatus,  the  same  quantity  of  nitro- 
glycerine is  produced  each  time  and  the  treatment 
of  100  kilos  of  glycerine  requires  less  than  half  an 
hour.1  In  America  as  much  as  2000  kilos  of 

glycerine  are  worked  at  one  time  in  open  vessels  provided  with  stirrers,  but  the  risk, 
in  case  of  explosion,  is  greatly  increased.  At  the  conclusion  of  the  operation  the  nitro- 
glycerine (sp.  gr.  L-6)  floats  on  the  acids  (sp.  gr.  1-7)  and  is  separated  by  means  of  a 
suitable  decanting  apparatus  (Fig.  182)  to  the  bottom  of  which  the  whole  mass  is  passed 
through  the  tube  K.  The  apparatus  consists  of  a  leaden  tank  with  its  base  sloping  towards 

1  The  temperature  during  the  reaction  should  not  exceed  25°  to  30°,  and  it  can  be  regulated  by  passing  the 
cooling  water  more  or  less  rapidly  through  the  coils,  and,  if  necessary,  through  the  wooden  jacket ;  increase  of  the 
air-current  also  helps  to  lower  the  temperature.  Rise  of  temperature  and  consequent  explosion  were  at  one  time 
due  principally  to  the  use  of  impure  glycerine,  but  nowadays  it  is  generally  due  to  slight  escape  of  water  from  the 
coils.  In  order  to  avoid  such  danger,  the  apparatus  and  coils  are  tested  at  least  once  a  day,  usually  in  the  evening 
when  the  plant  is  free  ;  water  under  pressure  is  forced  into  the  coils  and  jacket  and  left  until  the  morning,  when 
any  leak  can  be  detected.  Although  the  apparatus  is  constructed  of  vety  thick  plates,  the  lead  corrodes  in  time  ; 
tests  made  with  aluminium  apparatus  (proposed  by  Guttler)  have  not  been  very  successful.  Some  works  now  employ 
more  solid  vessels  of  wrought  or  cast  iron,  which  arc  more  easily  cooled. 

Boutmy  and  Faucher  avoid  the  dangers  of  violent  reactions  by  first  dissolving,  e.g.  100  parts  of  glycerine  in 
320  of  sulphuric  acid  and  then  pouring  the  solution  into  a  mixture  of  280  parts  of  nitric  and  280  of  sulphuric 
acid.  After  12  hours  the  reaction  is  complete,  the  yield  being  190  per  cent.,  calculated  on  the  weight  of  the 
glycerine  taken.  This  method  did  not  give  good  results  in  England,  but  lias  bei-n  applied  in  France. 

Kurtz  increases  the  yield  and  accelerates  the  reaction  by  emulsifying  the  glycerine  with  air  and  passing  it 
under  the  acid  mixture,  a  more  intimate  mixture  being  thus  obtained. 


FIG.  181. 


ITROGLYCERINE    PLANT 


227 


FIG.  182. 


the  centre  and  supported  by  a  wooden  structure  ;  the  cover,  C,  is  raised  on  wooden 
joists,  B.  The  tube  D,  with  the  glass  window,  E,  serves  to  carry  off  any  gas  which  may 
be  evolved  ;  a  thermometer  is  inserted  into  the  vessel  at  t.  The  tube  shown  at  the  bottom 

and  in  the  centre  of  the  appa- 
ratus communicates  with  two 
or  three  taps,  H,  and  is  also 
fitted  with  a  window,  F. 

After  half  an  hour,  the  nitro- 
glycerine in  this  vessel  separates 
into  a  distinct  layer,  as  may  be 
seen  through  /.  The  surface  of 
separation  of  the  two  layers 
coincides  very  nearly  with  the 
tap  J ',  so  that  the  nitroglycerine 
can  be  discharged  almost"  com- 
pletely through  the  tube  J  into 
the  lead-lined  wooden  tank,  L. 
The  acid  that  remains  is  dis- 
charged through  one  of  the  taps, 
H,  it  being  noted  through  F  when 
a  turbid  layer  appears,  as  this 
separates  the  acid  from  the  nitro- 
glycerine and  contains  various 
nitro -products  and  certain  im- 
purities.1 

The  tap,  H,  is  then  closed  and  this  liquid  is  passed  through  other  taps  into  suitable 
washing  and  decanting  vessels  (see  later).     The  nitroglycerine  in  L  is  washed  with  water 

1  The  acid  separated  from  the  nitroglycerine  and  containing  about  72  per  cent.  H2SO4,  9  per  cent.  HN03, 
16  per  cent.  H2O,  and  3  per  cent,  of  dissolved  nitroglycerine,  is  collected  in  leaden  tanks  in  which  it  remains  for 
one  or  two  days,  during  which  time  a  small  quantity  (about  0-5  per  cent.)  of  nitroglycerine  separates  at  the  surface. 
The  dangers  of  this  slow  separation  are  some- 
timrs  avoided  by  neglecting  the  nitroglycerine 
which  separates  after  4  to  5  hours  ;  to  avoid 
danger  in  succeeding  nitrating  operations,  a 
large  proportion  of  the  nitroglycerine  remaining 
dissolved  is  decomposed  by  adding  cautiously 
4  to  5  per  cent,  of  water  so  as  to  raise  the  tem- 
perature to  35°  to  40°  and  then  again  mixing 
the  mass  by  means  of  air  (part  of  the  trinitro- 
glycerine  is  thus  transformed  into  soluble  dinitro- 
glyeerine).  These  recovered  acids,  which  are 
utilised  again,  are  first  denitrated  in  the  appa- 
ratus shown  in  Fig.  183.  This  consists  of  a 
cylinder  of  earthenware  or  volvic  stone  filled 
with  fragments  of  silica  (quartz)  or  glass,  on  to 
which  the  acid  from  the  tank,  D,  is  sprayed  ;  a 
current  of  steam  from  the  cock,  a,  together  with 
a  little  air  are  passed  upwards  through  the  tower. 
As  the  temperature  rises  the  organic  matters  are 
oxidised  at  the  expense  of  the  nitric  acid,  which 
thus  gives  oxide  of  nitrogen,  this  passing  with 
the  other  nitrous  vapours  into  the  tube,  H,  which 
is  supplied  with  a  current  of  air  from  the  injec- 
tor, //.  The  mixed  vapours  are  divided  between 
a  double  battery  of  long  vertical  earthenware 
pipes,  G,  where  nitric  acid  of  38°  to  40°  B6. 
condenses,  any  vapour  escaping  being  finally 
condensed  in  a  Lunge-Rohrmann  tower. 

The  sulphuric  acid  at  last  reaches  the  bottom 
of  the  tower,  A,  where  it  collects  in  the  basin, 
E,  and  thence  passes  through  the  leaden  cooling 
coil,  F.  The  acid  thus  obtained  is  darkened  by  the  impurities  present  and  has  a  density  of  about  56°  to  58°  B6  ; 
it  is  usually  concentrated  in  cascade  apparatus  of  the  Negrier  type  or  in  Gaillard  towers  (see  vol.  i,  p.  269). 
-  During  recent  years,  instead  of  the  sulphuric  and  nitric  acids  being  recovered  and  concentrated  separately,  it 
has  been  found  preferable  to  send  the  acid  mixture — after  decomposition  of  the  dissolved  nitroglycerine  (see  above) 
— directly  but  carefully  into  the  boilers  (already  containing  the  sodium  nitrate)  in  which  nitric  acid  is  made. 
Some  prefer  to  revivify  the  acid  mixture,  i.e.  to  bring  it  up  to  its  original  strength  by  adding  the  necessary  quantities 
of  fuming  nitric  and  sulphuric  acids,  so  that  it  can  be  used  again  for  the  production  of  fresh  quantities  of  nitro- 
glycerine ;  for  this  purpose,  sulphuric  acid  or  oleum  is  added  slowly  to  the  required  amount  of  concentrated  nitric 
acid  and  the  mixture  then  poured  into  the  weak  acid.  For  this  process  of  recovering  the  weak  acids  (by  which  the 
2  .">  percent,  or  so  of  nitroglycerine  dissolved  in  the  acid  is  recovered)  to  be  employed,  a  cheap  supply  of  sulphuric 
anhydride  or  oleum  must  be  available  (oleum  at  less  than  4s.  per  quintal). 


^ 


FIG.  183. 


228 


ORGANIC    CHEMISTRY 


and  is  then  agitated  by  passing  compressed  air  through  the  perforated  pipe,  N,  for  about 
fifteen  minutes  ;  the  nitroglycerine  is  allowed  to  settle  and  the  water  decanted  off  by  means 
of  the  upper  tap,  M.  The  washing  with  water  is  repeated  two  or  three  times,  all  the  washing 
water  being  collected  in  a  single  tank.1  Finally  the  nitroglycerine  is  passed  into  a  similar 
vat  where  it  is  stabilised,  i.e.  washed  alternately  with  very  dilute  soda  solution  and  water 
until  the  wash -water  no  longer  has  an  acid  reaction  towards  litmus  and  the  nitroglycerine 
has  a  feeble  alkaline  reaction  (0-01  of  alkalinity,  which  disappears  later). 

In  the  British  Government  factory  at  Waltham  Abbey,  Nathan,  Thomson,  and  Rintoul 

(Eng.  Pats.  15,983,  1901 ;  and 
3020,  1903)  prepare  nitrogly- 
cerine in  large  leaden  vessels 
(a,  Fig.  184)  with  inclined 
bottoms  ;  in  these  300  to  500 
kilos  of  glycerine  are  treated 
at  one  time  and  at  the  end 


of  the  operation,  after  50  to 
60  minutes'  rest,  the  acid 
recovered  from  a  preceding 
operation  is  passed  from  the 
tank,  c,  to  the  bottom  of  a. 


FIG.  184. 


In  this  way  the  nitroglycerine  is  displaced  and  caused  to  discharge  through  s  into  the 
washing  vessel,  e,  exit  for  the  vapours  being  supplied  by  the  tube  o.  When  all  the  nitro- 
glycerine has  been  forced  out,  a  little  of  the  acid  mixture  is  drawn  off  by  the  pipe  i,  2  to 
3  per  cent,  of  water  being  then  slowly  added  to  the  remainder,  which  is  mixed  meanwhile 
with  a  current  of  air.  By  this  means  the  dissolved  nitroglycerine  is  decomposed  and  the 
dangers  of  slow  separation  in  any  of  the  vessels  avoided  (see  preceding  Note).  'The  acid 
is  immediately  denitrated,  after  sufficient  has  been  passed  into  the  tank,  c,  to  displace 
the  nitroglycerine  of  the  succeeding  operation,  b  is  the  tank  in  which  fresh  acid  is 
mixed,  /  the  vessel  for  drowning,  g  that  for  stabilising,  and  h  the  filter  for  the  nitro- 
glycerine, these  two  being  at  a  considerable  distance  from  e  so  that  the  nitroglycerine  may 
be  conducted  to  them  as  soon  as  it  has  undergone  its  initial  rough  washing.  Yields  of 
as  much  as  230  per  cent,  are  obtained  with  this  Nathan  -Thomson  process.  In  Italy  it 
is  used  at  the  Villafranca  (Tuscany)  dynamite 
factory. 

FILTRATION.  The  washed  nitrogly- 
cerine is  carried  in  hardened  rubber  or  ebonite 
buckets  to  the  filters,  which  are  merely  wooden 
frames  covered  with  woollen  cloth  or  felt  to 
retain  the  impurities,  scum,  gummy  matters, 
&c.  By  covering  these  cloths  with  a  layer  of 
dried  salt,  the  emulsified  water  can  also  be 
held  back.  The  cloths  rapidly  become  blocked 
and  are  frequently  renewed.  The  filtration 
is  often,  especially  in  England,  effected  by 
means  of  the  apparatus  shown  in  Fig.  185. 
This  consists  of  a  lead-lined  tank,  A,  with 
inclined  base.  In  the  lid  is  inserted  a  leaden 
cylinder,  G,  with  a  metal  gauze  bottom  on 
which  rests  a  filtering  cloth,  N,  and  on  this  a 
layer  of  sodium  chloride,  O,  covered  by  another  filtering  cloth  kept  stretched  by  a  leaden 
ring,  Q  ;  the  free  part  of  this  cloth  is  folded,  stretched,  and  fixed  by  a  conical  leaden 
weight,  E.  In  place  of  salt,  a  sponge  may  be  employed  to  retain  the  water.  In  some 
cases  complete  separation  of  the  water  from  nitroglycerine  is  obtained  by  leaving  the 
latter  at  rest  for  a  couple  of  days  in  a  tepid  place  (30°)  ahd  then  decanting  it  ;  but  there 

1  The  wash-waters  from  all  the  preceding  operations  are  collected  in  an  inclined  lead-lined  tank  called  the 
labyrinth,  which  is  divided  into  a  number  of  chambers  by  vertical  leaden  walls  perforated  alternately  at  the  top 
and  bottom.  The  wash-waters  enter  slowly  at  one  end  of  the  tank  and  traverse  a  long  up-and-down  course, 
gradually  depositing  the  emulsified  or  suspended  drops  of  nitroglycerine  before  the  opposite  end  of  the  tank  is 
reached.  The  nitroglycerine  collected  at  the  bottom  is  discharged  through  suitable  taps  and  added  to  that  in  the 
washing  apparatus. 


FIG.   185. 


DYNAMITES  229 

is  then  some  risk  owing  to  the  prolonged  accumulation  of  large  quantities  of  nitro- 
glycerine, i 

In  the  working  of  nitroglycerine,  each  operation  is  usually  carried  out  in  a  separate 
building,  that  in  which  the  explosive  is  produced  being  at  a  very  high  elevation,  the  nitro- 
glycerine then  flowing  to  lower  points  for  the  succeeding  operations.  All  these  buildings 
are  of  wood  so  as  to  diminish  the  damage  in  case  of  explosion.  The  floors  of  the  sheds  in 
which  the  nitroglycerine  is  produced  and  of  those  where  it  is  treated  in  the  liquid  state  are 
covered  with  sheet-lead  with  raised  edges  so  that  the  material  may  be  caught  in  case  of 
breakage. 

Where  the  nitroglycerine  is  worked  in  a  pasty  state  (for  dynamites)  the  flooring  is  of 
wood  free  from  crevices. 

If  nitroglycerine  is  accidentally  spilled,  it  should  be  immediately  wiped  up  with 
sponges. 

The  channels  through  which  nitroglycerine  passes  from  one  shed  to  another  are  in  the 
form  of  gutters  furnished  with  removable  covers  and  are  fitted  with  a  longitudinal  pipe 
through  which  warm  water  can  be  circulated  in  winter  and  the  danger  of  freezing  avoided. 
A  disadvantage  attending  the  use  of  these  channels  is  that  an  explosion  in  one  shed  is 
propagated  along  the  channels  to  all  the  other  sheds.  So  that  the  precaution  is  taken  of 
disconnecting  one  section  of  a  channel  when  not  in  actual  use.  In  many  factories  the  nitro- 
glycerine is  transported  in  rubber  pails  (see  above). 

The  windows  of  the  sheds  are  smeared  with  whitening,  as  the  presence  of  curved  parts 
in  the  naked  glass  might  possibly  result  in  the  focusing  of  light  on  the  explosive  material 
and  the  explosion  of  the  latter. 

USES  OF  NITROGLYCERINE.  Small  quantities  are  sometimes  used 
in  medicine  to  induce  dilatation  of  the  blood-vessels,  but  practically  the  whole 
of  the  production  is  used  as  an  explosive.  In  America  it  has  been  long  in  use 
in  the  pure  state  for  large  mining  operations  ;  Mowbray  freezes  it  and  trans- 
ports it  in  large  quantities  on  trains  from  the  factory  to  the  place  of  consump- 
tion, as  he  regards  it  as  less  sensitive  in  the  frozen  state  ;  but  this  view  is  generally 
contested.  It  has  also  been  transported  without  danger  in  solution  in  methyl 
or  ethyl  alcohol,  from  which  it  is  reprecipitated  with  water  at  its  destination. 
Almost  all  the  nitroglycerine  made  is  used  in  the  manufacture  of  various  kinds 
of  dynamites,  dynamite  gelatines,  explosive  gelatines,  smokeless  powder,  &c. 

DYNAMITES.  This  generic  name  is  given  to  explosives  obtained  by 
gelatinising  or  absorbing  nitroglycerine  by  various  other  substances.  We  have 
already  mentioned  that  Alfred  Nobel,  the  father  of  dynamite,  had  from  1860 
to  1864  various  explosions  of  nitroglycerine,  sometimes  of  that  recovered  from 
the  alcohol  in  which  it  had  been  transported  (see  above).  In  his  attempts  to 
diminish  the  dangers  of  nitroglycerine  by  diluting  it  with  inert  substances, 
Nobel  discovered  in  1866  that  it  is  absorbed  by  kieselguhr  (infusorial  earth)  in 
considerable  proportions  (up  to  81  per  cent.),  and  that  in  this  state  its  power 
is  diminished  but  little,  while  it  can  be  safely  handled  and  transported.  He 
found  further  that  this  dynamite  is  exploded  only  by  means  of  a  fulminate  of 
mercury  cap. 

Kieselguhr  is  found  in  a  very  pure  state  in  the  Liineburg  moors,  near  Unterluss  in 
Hanover,  and  in  an  inferior  quality  in  Scotland,  Norway,  and  Italy.  It  consists  almost 
exclusively  of  the  siliceous  remains  of  diatoms,  and  contains  also  traces  of  iron  and  organic 
matter.  Its  particles  are  formed  of  empty  tubes  perforated  in  all  directions,  and  it  is 
this  structure  which  renders  kieselguhr  so  highly  absorbent.  Under  the  microscope,  it 
presents  the  appearance  shown  in  Fig.  186.  At  the  present  time  kieselguhr  dynamite 
has  been  almost  entirely  replaced  by  new  types  (gums  or  gelatines)  described  later. 

If  the  absorbing  substances  are  inert,  like  infusorial  silica  (kieselguhr),  sawdust,  cellulose, 
&c.,  they  form  dynamites  with  inactive  absorbents,  which  contain  about  72  to  75  per  cent, 
of  nitroglycerine,  24-5  per  cent,  of  kieselguhr,  and  0-5  per  cent,  of  soda  for  the  No.  1  quality, 
and  less  nitroglycerine  in  the  Nos.  2  and  3  qualities. 

But  in  the  new  type  of  dynamite  the  solid  matter  consists  of  active  substances,  e.g. 
nitrocellulose,  which  take  part  in  the  explosion.  These  are  dynamites  with  active  absorbents, 


230 


ORGANIC    CHEMISTRY 


the  absorbents  or  bases  being  again  divided  into  nitrates  or  inorganic  oxidising  bases  and 
organic  nitro-absnrbents  (collodion-cotton,  &c.). 

I.     MANUFACTURE  OF  DYNAMITE  WITH  INACTIVE  ABSORBENTS.      The 
kieselguhr   used  must  be  suitably  prepared.     It  is  first  spread  out  in  furnace  chambers 


TIG.  186. 

and  gently  heated  to  eliminate  moisture  and  organic  matter,  and  is  then  more  strongly 
calcined  in  reverberatory  or  muffle-furnaces,  excessive  heating  being  avoided  as  it  may 
destroy  the  absorbing  properties.  It  is  then  ground  into  fine  powder  and  sieved.  The 
flour  thus  obtained  should  not  contain  more  than  1  per  cent,  of  moisture  and  should  be 

immediately  filled  into  sacks  and  consumed  the  same 
day,  as  otherwise  it  might  absorb  moisture.  It  consists 
of  silica  with  traces  of  oxides  of  iron  and  aluminium. 

The  nitroglycerine  is  weighed  in  buckets  of  hard  gutta- 
percha  or  lacquered  compressed  wood-pulp  and  is  carefully 
taken  to  the  mixing-house,  where  it  is  poured  into  wooden 
troughs  lined  with  sheet-lead,  and  containing  the  absor- 
bent. Skilled  workmen  then  mix  the  mass  rapidly  by 
hand  ;  sometimes  rubber  gloves  are  worn,  but  usually  the 
men  prefer  to  do  without  gloves,  as  the  hands  become 
accustomed  to  the  action  of  the  nitroglycerine  in  two  or 
three  days. 

It  is  important  to  obtain  a  homogeneous  mixture,  so . 
that  not  the  least  portion  of  the  kieselguhr  remains  free 
from  nitroglycerine.  After  this  hand-mixing  the  mass  is 
rubbed  through  brass-wire  sieves  (2  to  3  meshes  per  centi- 
metre) arranged  above  lead-lined  wooden  troughs.  The 
dynamite  is  placed  on  the  sieve  with  a  wooden  spatula 
and  pressed  through  with  the  palm  of  the  hand  ;  here, 
too,  the  use  of  rubber  gloves  is  not  popular  with  the 
operatives.  In  the  troughs  the  dynamite  is  in  the  form 
of  fine  grains,  which  should  not  be  too  dry  or  too 
greasy.  If  too  dry,  it  is  passed  again  through  the  sieve  or  mixed  with  more  nitro- 
glycerine, whilst  if  too  greasy  it  is  mixed  with  a  further  amount  of  kieselguhr.  It  is 
then  placed  in  small  portions  in  iiidiarubber  bags  or  in  .wooden  boxes  lined  with  sheet- 
zinc  and  is  removed  to  the  building  where  the  cartridges,  used  especially  in  mines,  are  pre- 
pared. Here  the  dynamite  is  transformed  by  simple  presses  into  rolls,  19,  23,  or  26  mm.  in 
diameter.  A  very  simple  press  devised  by  O.  Guttmann  is  shown  in  Fig.  187.  The  dyna- 
mite is  introduced  into  the  cloth  bag,  m,  and  falls  into  the  tube,  I,  being  pressed  into  this 
by  the  lignum  vitse  or  ivory  piston,  p,  at  the  end  of  the  bar,  d,  which  is  actuated  by  the 


FIG.  187. 


COMPOSITIONS    OF    DYNAMITES  231 

ICVCT,  i  ;  the  cylinder  of  dynamite  issuing  from  the  bottom  of  the  tube,  Z,  is  broken  by  hand 
into  definite  lengths,  which  are  wrapped  in  parchment  paper  or  paraffined  paper.  The 
ordinary  length  is  10  cm.  (discharge  cartridges)  or  2-5  to  5  cm.  (primers).  These  cartridge 
machines  are  sometimes  worked  by  pulleys  and  motors.  In  some  cases  the  boudineuses 
illustrated  later  are  used.  After  the  dynamite  is  wrapped  up,  packets  of  2-5  kilos  are  placed 
in  cardboard  boxes,  which  are  wrapped  and  tied  round  and  filled  in  tens  into  wooden  cases. 
For  military  purposes  the  cartridges  are  put  directly  into  metal  boxes  with  a  socket  in  the 
lid  for  inserting  the  detonator.  For  use  under  water  these  metal  boxes  are  sometimes 
used,  and  sometimes  sausage-skins  or  rubber  bags. 

These  cartridge  buildings  are  usually  small  with  light  walls  and  roof  ;  only  two  or  three 
operatives  work  in  each,  high  earthen  banks  separating  one  man  from  the  next  so  that  the 
effects  of  an  explosion  may  be  mitigated. 

In  place  of  kieselguhr  various  other  absorbents  are  used  at  the  present  time,  e.g.  wood 
meal  (cellulose)  mixed  with  inert  mineral  salts  (calcium  carbonate,  sodium  bicar- 
bonate, &c.). 

First  in  America  and  then  in  -Austria  fulgurite  was  prepared  with  60  per  cent,  of  nitro- 
glycerine, the  remaining  40  per  cent,  consisting  of  wheaten  flour  and  magnesium  carbonate. 
At  Cologne,  Miiller  prepared  a  Wetter- dynamite  (safety  dynamite,  for  use  in  mines  containing 
firedamp  ;  see  later)  by  mixing  10  parts  of  ordinary  dynamite  with  7  parts  of  crystalline 
sodium  carbonate  ;  the  water-vapour  formed  on  explosion  surrounds  the  flame  and  the 
explosive  gases  and  thus  prevents  explosion  of  the  firedamp.  Many  varieties  of  these 
dynamites  are  used  to  a  greater  or  less  extent  in  practice,  e.g.  carbodynamite  containing 
90  per  cent,  of  nitroglycerine  and  10  per  cent,  of  carbonised  cork,  sebastine,  lithoclastite, 
carbonite,  &c. 

Properties  of  Dynamite  with  Inert  Bases.  This  forms  a  pasty  mass  of  reddish  yellow, 
red,  or  grey  colour  according  to  the  quality  of  the  infusorial  earth  employed  ;  to  ensure 
a  uniform  colour  about  0-25  per  cent,  of  burnt  ochre  is  often  added.  It  is  odourless  and 
has  the  sp.  gr.  1  -4  and  the  pasty  consistency  of  wet  modelling  clay  ;  the  inside  of  the  wrapper 
should  show  no  traces  of  nitroglycerine  (sweating).  It  is  much  less  sensitive  to  pressure 
and  percussion  than  nitroglycerine  and,  in  small  portions,  can  be  lighted  and  burned 
without  exploding. 

It  can,  however,  be  exploded  by  powerful  percussion  or  detonation,  or  by  red-hot 
metal,  or  by  heating  suddenly  to  a  high  temperature  or  for  a  long  time  at  70°  to  80°. 
Dynamite  freezes  at  temperatures  below  +  8°  and  then  becomes  less  sensitive  ;  before 
being  used  it  must  be  carefully  thawed  in  warming-pans,  surrounded  by  water  at  a  tem- 
perature not  exceeding  60°  ;  it  must  never  be  thawed  on  a  heated  metal  plate.  Thawed 
dynamite  should  be  used  carefully  as  a  little  nitroglycerine  exudes  during  thawing.  Most 
of  the  dynamite  made  is  used  as  an  explosive  in  mines  and  for  firearms  ;  for  cannon  it 
has  little  use,  owing  to  the  danger  caused  by  sweating  during  the  thawing,  so  that  for 
military  purposes  explosives  are  used  which  are  safer  to  transport  and  not  so  sensitive  to 
shock  or  to  discharge  (explosion  by  sympathy). 

II.  DYNAMITES  WITH  ACTIVE  BASES,  (a)  Pulverulent  Dynamites  with 
Inorganic  Nitrates.  Immediately  after  the  discovery  of  dynamite  with  a  silica  base 
came  the  idea  of  replacing  the  inactive  substance,  which  diminished  the  force  of  the 
nitroglycerine,  by  active  substances  so  that  the  explosive  power  of  the  dynamite  might 
be  increased. 

In  America  such  dynamites  are  often  made  with  40  per  cent,  of  nitroglycerine,  45  per 
cent,  of  sodium  nitrate,  14  per  cent,  of  wood-pulp,  and  1  per  cent,  of  magnesium  carbonate  ; 
these  dynamites  are  well  suited  for  mines  where  no  great  power  but  considerable  safety  is 
required.  In  Europe  mixtures  of  nitroglycerine,  ammonium  nitrate,  fine  sawdust,  sodium 
nitrate,  carbon,  &c.,  are  made  ;  e.g.  20  per  cent,  nitroglycerine,  36  per  cent,  sodium  nitrate, 
25  per  cent,  ammonium  nitrate,  18-5  per  cent,  roasted  rye  flour,  and  0-05  per  cent.  soda. 

In  Austria  Trauzl  in  1867  prepared  a  pasty  mixture  of  nitroglycerine  with  guncotton, 
which  was  not  affected  by  water  and  was  exploded  only  by  fulminate  of  mercury  detonators. 
This  product  was  not  successful,  but  similar  and  improved  preparations  were  subsequently 
made. 

About  this  time  Abel  in  England  prepared  glyoxiline  by  soaking  defibred  guncotton 
and  potassium  nitrate  in  nitroglycerine  ;  this  was  also  unsuccessful. 

(b)  Blasting  Gelatine  and  Gelatine  Dynamite.     Since  these  contain  nitrocellulose,  they 


232 

will  be  mentioned  later  (see  Smokeless  Powders),  after  the  manufacture  of  nitrocellulose 
has  been  described. 

Statistics  of  dynamite  :   see  later  at  the  end  of  the  chapter  on  Explosives. 

NITROCELLULOSE 
(Guncotton  or  Pyroxyline  and  Collodion-Cotton) 

This  substance  should,  to  be  in  order,  be  described  later,  after  cellulose 
(which  is  a  carbohydrate  with  many  alcoholic  groups  and  with  a  molecular 
formula  polymeric  with  C6H1005)  has  been  studied,  but  as  its  properties  and  uses 
are  closely  connected  with  those  of  explosives,  it  is  considered  opportune  to 
include  it  in  the  present  section.1 

CONSTITUTION  OF  NITROCELLULOSE.  The  relation  CwH2wOw  of  the  com- 
ponents  of  cellulose  being  expressed  by  the  more  simple  formula  (C6H10O6)W,  it  is  found  that 
the  maximum  degree  of  nitration  consists  in  the  introduction  of  three  nitric  acid  residues  per 
molecule  of  C6H10O6,  so  that  guncotton  was.  given  the  name  trinitrocellulose,  and  was  repre- 
sented by  the  formula  C6H705(N02)3.  Since  the  use  of  more  dilute  acids  results  in  the 
combination  of  a  less  proportion  of  nitric  acid  residues,  it  is  supposed  that  a  mononitro- 
and  a  dinitro-cellulose  are  also  formed. 

It  was  found  later  by  Eder  that  there  exist  nitrocelluloses  with  compositions  intermediate 
to  those  of  tri-  and  di-nitrocellulose,  and  others  between  the  mono-  and  di-nitro-compounds, 
so  that  it  must  be  supposed  that  cellulose  has  a  formula  at  least  double  that  of  the 
simple  one  given  above  ;  but  the  mononitrocellulose  corresponding  with  this  doubled 
formula,  C12H20010,  i.e.  (C6H10H5)2,  has  not  yet  been  prepared. 

Still  later  Vieille,  by  accurate  study  of  the  nitrocelluloses  prepared  with  acids  of  various 
concentrations,  succeeded  in  preparing  eight  different  types  of  nitrocellulose,  this  result 
indicating  that  Eder's  formula,  which  predicted  only  six,  could  no  longer  serve.  Vieille 
then  proposed  for  cellulose  a  formula  double  that  of  Eder,  i.e.  C24H40020  or  (C6H1005)4. 
according  to  which  twelve  nitrocelluloses  are  theoretically  possible  ;  eight  of  these,  from 
endeca-  to  tetra -nitrocellulose  have  been  actually  prepared.  Mendelejeff,  having  found 
nitrocelluloses  intermediate  to  or  identical  with  these  twelve,  but  different  from  those 
studied  by  Vieille  in  being  soluble  in  a  mixture  of  alcohol  and  ether,  proposed  the  doubling 
of  Vieille 's  formula,  so  that  cellulose  becomes  C48H80040  or  (C6H10O5)8.  To-day,  however, 
it  is  thought  that  these  differences  are  due  to  mechanical  mixtures  of  the  various  nitro- 

1  In  1833  Braconnot  observed  that  when  starch  or  wood  is  treated,  with  concentrated  nitric  acid,  a  mucilaginous 
solution  is  obtained  which,  on  addition  of  water,  yields  a  white  powder  soluble  in  a  mixture  of  alcohol  and  ether  ; 
this  powder,  which  burns  vigorously,  he  called  xyloidin.  In  1838,  by  subjecting  cotton  to  the  same  treatment, 
Pelouze  obtained  a  product  which  exploded  on  percussion  and  was  indeed  nothing  but  xyloidin  ;  he  recommended 
it  as  highly  suitable  for  the  manufacture  of  fireworks.  In  1845  Schonbein  at  Basle,  and  some  months  later,  and 
independently,  Bottger  at  Frankfort  discovered  that  the  nitration  of  cellulose  takes  place  much  more  easily  and 
completely  if  the  cotton  is  treated  with  a  mixture  of  concentrated  nitric  and  sulphuric  acids.  In  order  to  utilise  in- 
dustrially the  guncotton  thus  obtained,  the  two  discoverers  combined  and  kept  their  process  secret.  After  the 
initial  difficulty  in  getting  this  new  explosive  taken  up  in  practice,  the  extraordinary  power  of  guncotton  and  its 
great  advantages  over  black  powder  aroused  considerable  enthusiasm.  But  scarcely  had  it  come  into  general  use  in 
various  countries  than  a  number  of  spontaneous  and  fatal  explosions  in  guncotton  factories  and  magazines,  by 
which  whole  buildings  were  razed  to  the  ground,  created  such  a  panic  that  its  manufacture  was  everywhere 
abandoned.  The  process  of  nitration  was  then  already  known  to  Knop  and  Karmarsch,  and  to  others,  who 
manufactured  guncotton  by  this  simple  process.  And  in  1846  Sobrero  made  use  of  the  nitric-sulphuric  mixture 
for  the  preparation  of  nitroglycerine. 

In  1853  the  Austrian,  Captain  von  Lenk,  ascertained  how  to  render  guneotton  safe.  The  Austrian  Government 
acquired  from  Schonbein  and  Bottger  the  process  of  manufacture  (at  a  price  stated  to  be  30,000  florins,  or  £2500) 
and  maintained  the  secret  of  avoiding  the  spontaneous  decomposition  of  guncotton  until  1862.  Then  von  Lenk 
communicated  the  secret  to  the  French  and  English  Governments,  and  in  1864  patented  the  process  in  America. 
Whilst  in  America  the  manufacture  was  undertaken  on  an  enormous  scale,  in  Austria  and  England  it  was  again 
suspended  on  account  of  further  terrible  explosions  in  the  factories  themselves ;  these  were  explained  by  the 
English  workers  as  due  to  the  insufficient  purification  of  the  nitrocellulose  by  von  Lenk.  In  1865  Abel  discovered 
the  method  of  bestowing  absolute  safety  and  keeping  qualities  on  the  nitrocellulose.  He  used  first  of  all  the 
process  of  washing  proposed  in  1862  by  the  Englishman  J.  Tonkin,  which  consisted  simply  in  complete  washing  with 
abundant  supplies  of  water ;  the  nitrated  cotton  was  then  defibred  or  pulped  in  machines  similar  to  those  em- 
ployed in  paper  factories  and  the  wet  pulp  subjected  to  considerable  pressure.  From  that  time  the  manufacture 
extended  to  all  countries,  in  spite  of  an  English  factory  being  blown  up  in  1871  (apparently  a  criminal  act),  and  in 
recent  times  it  has  acquired  new  and  increased  importance  owing  to  the  discovery  of  smokeless  powder. 

The  process  universally  used  at  the  present  time  in  the  manufacture  of  guncotton  is  that  indicated  by  Abel. 
Before  the  discovery  of  smokeless  powder,  guncotton  had  limited  applications  and  was  not  used  in  mines  since,  in  the 
form  in  which  it  was  prepared,  it  had  an  excessive  shattering  action,  whilst  in  mines  progressive  explosives  are 
usually  required. 


GUNCOTTON  233 

celluloses  rather  than  to  separate  chemical  combinations,  and  further,  that  the  nitration 
is  gradual  and  leads  from  the  more  simple  to  the  more  complex  forms. 

Nitrocelluloses  with  more  than  12-83  per  cent,  of  nitrogen  were  at  one  time  regarded 
as  being  insoluble  in  alcohol-ether,  but  Abel  showed  that  there  are  nitrocelluloses  with 
13-2  per  cent,  of  nitrogen  and  still  soluble  in  this  mixture,  whilst  others  with  only  12-8  per 
cent,  are  insoluble  ;  and  that  this  depends  on  the  method  of  preparation — the  duration  of 
action  of  the  mixed  acids,  the  ratios  and  concentrations  of  the  latter,  and  the  temperature 
at  which  they  act — and  on  the  nature,  purity,  and  dryness  of  the  cotton.  Only  by  following 
exactly  the  directions  is  it  possible  to  obtain  a  constant  percentage  of  nitrogen  and  complete 
solubility  or  insolubility  in  the  mixture  of  alcohol  and  ether. 

It  was  also  once  thought  that  guncotton  was  a  nitro-compound  in  the  true  sense  of 
the  word,  i.e.  that  the  N02  groups  were  united  directly  to  carbon.  But  first  Bechamp  and 
then  others  showed  that  it  is  a  true  nitric  ester  which  can  be  saponified,  with  regenera- 
tion of .  the  cellulose,  by  alkalis,  alkaline  salts,  ammonium  sulphide,  or  ferrous  chloride. 
It  has  been  further  shown  that  with  the  maximum  of  nitrogen  an  oxynitrocellulose 
is  obtained  [oxycellulose  is  (C6H1005)3  +  (C6H1006)n,  so  that  the  nitrocellulose  will  be 
C6H7(N02)3O5  +  C6H7(NO2)3O6,  and  this  with  ferrous  chloride  gives  oxycellulose  ;  nitro- 
mannitol,  treated  similarly,  gives  mannitol  and  not  oxymannitol]. 

PROPERTIES  OF  GUNCOTTON.  Under  the  microscope  nitrocellulose 
has  the  same  appearance  as  ordinary  cotton,  but  in  polarised  light  it  appears 
iridescent.  When  moistened  with  a  solution  of  iodine  in  potassium  iodide 
and  then  with  sulphuric  acid,  nitrocellulose  becomes  yellow  and  cellulose  blue. 
It  is  somewhat  less  white  than  ordinary  cotton,  is  rather  rough  to  the  touch  and 
crackles  when  pressed  with  the  fingers  ;  it  becomes  electrified  when  rubbed  and 
then  appears  phosphorescent  in  the  dark.  It  is  soluble  in  ethyl  acetate,  nitro- 
benzene, benzene,  acetone,  &c.,  but  insoluble  in  water,  alcohol,  ether,  acetic 
acid  or  nitroglycerine,  although  a  mixture  of  nitroglycerine  and  nitrocellulose 
is  soluble  in  acetone,  forming  a  jelly,  cordite  (see  later). 

It  resists  the  action  of  dilute  acids,  but  is  decomposed  slowly  by  concen- 
trated sulphuric  acid  or  hot  alkali,  and  completely  by  hot  sodium  sulphide. 
Decomposition  is  also  effected  by  iron  and  acetic  acid  or  by  ammonium  sul- 
phide or  ferrous  chloride  (Bechamp). 

Flocculent,  loose  guncotton  has  the  sp.  gr.  0-1,  whilst  the  powder  (pulp) 
has  the  sp.  gr.  0-3  and  is  exploded  by  shock  or  percussion  only  at  the  point 
where  it  is  struck,  the  explosion  not  being  propagated  to  the  whole  mass.  When 
ignited,  it  burns  so  rapidly  that  even  when  it  is  placed  on  black  powder,  the 
latter  does  not  burn. 

In  the  form  of  cord,  it  burns  more  slowly  and  may  be  used  as  a  rapid  fuse. 
When  wet  or  compressed  it  has  a  specific  gravity  varying  from  1  to  1-3  (the  abso- 
lute sp.  gr.  is  1-5)  and  it  then  burns  slowly  and  cannot  be  exploded  by  percussion 
or  by  ordinary  detonators  ;  explosion  can,  however,  be  induced  by  detonating 
a  little  dry  guncotton  with  a  fulminate  of  mercury  cap.  The  decomposition 
proceeds  according  to  the  equation  : 

2C6H702(ON02)3  =  500  +  7C02  +  8H  +  3H20  +  6N. 

Less  compressed  guncotton  gives  more  CO  and  H  in  comparison  with  the 
C02  and  H20,  and  hence  has  a  less  effect,  the  development  of  heat  being  smaller. 
No  ash  or  smoke  is  formed,  and  1  kilo  of  guncotton  yields  741  litres  of  gas  (the 
water  being  liquid,  or  982  litres  if  the  water  is  in  the  state  of  vapour),  which  is 
inflammable  and,  owing  to  the  presence  of  carbon  monoxide,  poisonous.  The 
temperature  of  combustion  has  been  given  as  6000°  (i.e.  1071  Cals.  are  developed 
by  1  kilo). 

Unless  guncotton  is  carefully  prepared,  it  undergoes  gradual  change  and 
may  explode  spontaneously,  especially  in  the  light,  and  to  this  are  probably 


234  O  R  G  A  N  I  C    C  H  E  M  I  S  T  R  Y 

due  the  great  explosions  which  occurred  formerly  (1848-1862).  Even  dry, 
granulated  guncotton  becomes  harmless  and  safe  to  handle  if  it  is  immersed 
for  a  moment  in  ethyl  acetate,  as  it  becomes  coated  with  a  gelatinous  layer 
which  dries  it  and  preserves  it,  if  moist,  from  further  evaporation. 

Guncotton  is  transported  in  large  quantities  in  the  wet  state  in  wooden 
boxes  placed  in  others  of  zinc  which  are  sealed  hermetically  to  retain  the 
moisture.  It  is  stored  in  dry  magazines  which  are  situate  at  least  150  metres 
from  any  habitation  and  are  not  surrounded  by  earthworks  so  that  the  more 
serious  effects  due  to  projection  of  debris  may  not  be  added  to  those  of  an 
explosion. 

MANUFACTURE  OF  GUNCOTTON.  Hanks  of  purified  cotton,  free  from  impurities, 
are  employed.  This  cotton  should  fulfil  certain  requirements.1 

The  pure  cotton  is  placed  loose  on  trays  which  are  arranged  in  a  drying-stove  heated 
by  means  of  gilled  pipes  through  which  steam  circulates  ;  the  heating  is  continued  until 
the  proportion  of  moisture  is  less  than  0-5  per  cent.,  after  which  the  cotton  is  allowed  to  cool 
for  12  to  15  hours  in  hermetically  sealed  boxes.  If  not  pure  the  cotton  is  best  defatted 
by  boiling  it  for  2  to  3  minutes  with  2  per  ce'nt.  sodium  hydroxide  solution  ;  it  is  then  washed 
with  water  and  subsequently  treated  with  very  dilute  nitric  acid  in  the  hot.  In  some 
cases  it  is  also  bleached  with  a  weak  solution  of  hypochlorite,  well  rinsed  with  water  and 
dried  in  a  hot-air  oven  as  above.  When  almost  dry  it  is  carded,  dried  completely,  and, 

while  still  hot,  placed    in   hermetically  sealed  boxes 
so  that  no  more  moisture  may  be  absorbed. 

Nitration  is  then  effected  with  a  mixture  of  con- 
centrated nitric  and  sulphuric  acid,  as  follows  :  3  parts 
of  pure  sulphuric  acid  of  sp.  gr.  1-841  (96  per  cent.)  a ic 
poured  into  1  part  of  pure  nitric  acid  of  sp.  gr.  1-516, 
mixing  taking  place  immediately  and  completely 
without  the  aid  of  stirrers.  The  mixture  is  then 
delivered  with  the  help  of  an  acid  elevator  (Monte/jus) 
into  the  nitration  apparatus,  consisting  of  a  cast-iron 

FIG.  188.  vessel,  A  (dipping  pot)  (Fig.  188),  standing  in  a  larger 

vessel,   G,  through  which  cold  water  circulates  from 

H  to  J.  The  cotton  is  immersed  in  small  portions  (300  to  800  grms.)  in  the  acid-bath  and 
is  stirred  with  an  iron  fork.  In  England  1  kilo  of  cotton  is  used  per  160  kilos  of  the  acid 
mixture,  while  in  Germany  1  kilo  of  cotton  is  taken  for  every  40  kilos  of  acid  ;  after  a 
short  time  (15  to  30  minutes)  the  nitrated  cotton  is  removed  with  iron  forks  and  is  placed 
to  drain  on  a  cast-iron  grid  (grate),  B  and  C,  arranged  on  one  side  above  the  vessel ;  before 
it  is  taken  away,  it  is  pressed  with  a  cast-iron  plate,  F,  connected  with  a  lever,  D  E. 

The  acid  mixture  is  renewed  when  it  has  treated  30  to  50  per  cent,  of  its  weight  of  cotton  ; 
also  after  each  portion  of  cotton  is  removed  from  the  bath,  fresh  acid  mixture,  equal  to 
ten  times  the  weight  of  the  cotton  taken  out,  is  added  in  order  to  make  up  for  what  has  been 
absorbed  and  combined.  On  the  German  system  (where  less  acid  is  used)  renewal  takes 
place  more  frequently.  Above  each  of  the  nitrating  vessels  is  a  hood  with  a  strong  draught 
to  carry  off  the  nitrous  vapours  which  are  always  evolved.  Excessive  rise  of  temperature 
gives  a  guncotton  which  contains  less  nitrogen  and  shows  less  complete  insolubility  in 
alcohol-ether  than  are  required  in  practice. 

In  some  factories  the  nitration  is  carried  out  in  a  number  of  small,  deep  and  narrow, 
hemispherical  vessels  of  cast-iron  mounted  on  trolleys.  These  are  charged  in  order  with 
certain  weights  of  acid  mixture  (30  to  50  kilos)  and  dry  cotton  (2  to  4  kilos),  and,  after 
thorough  mixing,  the  trolleys  are  pushed  into  an  oblong  lead-lined  chamber  provided  with 

1  Cotton  for  nitrocellulose  should  be  pure  white  and  should  not  contain  dust  or  fibres  of  jute,  hemp,  or  flax, 
or  woody  matter  or  pods  ;  these  impurities,  when  separated  by  hand  from  200  grms.  of  the  cotton,  should  not 
exceed  0-5  grm.  The  filaments  should  not  be  too  short,  otherwise  they  form  a  paste  during  nitration.  A  small 
piece  thrown  into  water  should  sink  in  two  minutes.  It  should  not  contain  more  than  6-9  per  cent,  of  substances 
soluble  in  ether  (fats,  &c.) ;  in  many  factories  0-5  per  cent,  is  not  allowed.  In  England  the  amount  of  fat  allowed 
is  1-1  per  cent,  extracted  with  ether  in  4  hours  in  a  Soxhlct  apparatus  (sea  Analysis  of  Fats).  The  moisture, 
determined  by  heating  the  cotton  in  an  oven  at  100°  until  its  weight  remains  constant,  should  not  exceed  6  per  rent, 
and  the  cotton  merchant  is  debited  with  any  excess  and  also  with  the  cost  of  drying. 

When  moistened  with  a  few  drops  of  water,  the  cotton  should  maintain  a  neutral  reaction. 

The  ash,  estimated  by  heating  a  few  grammes  of  the  cotton  to  redness  in  a  platinum  capsule  until  it  becomes 
quite  white  and  of  constant  weight,  should  not  amount  to  more  than  0-3  per  cent. 


MANUFACTURE  OF  GUNCOTTON 


235 


as  many  doors  as  there  arc  trolleys.  A  powerful  aspirator  draws  the  nitrous  vapours 
into  a  wooden  flue.  A  battery  of  soaking-pots  is  used  in  such  a  way  that  w.hen  the  last 
is  introduced  into  the  chamber  the  first  has  already  finished  reacting  (30  to  40  minutes), 
and  as  the  pots  are  of  metal  and  relatively  small  and  are  in  a  strong  draught,  the  heat 
developed  is  readily  dispersed.  The  pets  are  removed  from  the  chamber  and  taken  to  the 
neighbouring  centrifugal  machines,  into  which  the  contents  of  the  pots,  which  are  mounted 
on  pivots,  are  tipped.  The  centrifuges  are  similar  to  those  employed  in  sugar  factories  (see 
Sugar)  and  have  a  steel  or  leaded  steel  rotating  basket  ;  aluminium  ones  have  also  been  tried 
but  not  with  great  success.  A  few  minutes'  centrifugation  at  1000  revolutions  per  minute 
removes  the  greater  part  of  the  acid  from  the  guncotton  ;  the  latter  is  immediately  taken 
to  the  washing  machines,  while  the  acid  recovered  is  revivified  in  the  manner  described 
on  p.  227.  If  drops  of  water  or  lubricating  oil  fall  on  to  the  cotton  during  centrifugation, 
the  mass  sometimes  undergoes  sudden  decomposition  with  formation  of  a  dense  cloud  of 
brown  vapour ;  this  does  not  constitute  a  serious  danger,  since  usually  it  is  not  accompanied 
by  explosion. 

In  some  factories  the  nitration  is  nowadays  carried  out  directly  in  the  centrifuges, 
which  may  be  of  naked  or  leaded  steel  or  even  of  earthenware,  although  these  are  heavier 


FIG.  189. 


FIG.  190. 


and  more  fragile  (see  Figs.  189,  190).  The  latter  consist  of  a  double-walled  earthenware 
basket,  the  inner  wall,  d  and  a,  but  not  the  outer  one,  being  perforated  ;  the  two  walls  being 
a  slight  distance  apart,  an  annular  space,  c,  is  left,  which  has  an  outlet  above  in  a  number 
of  holes,  s,  in  the  edge  of  the  bush.  The  whole  is  bound  with  steel  hoops,  t,  to  prevent 
danger  from  projection  in  case  of  fracture.  The  dry  cotton  (7  to  8  kilos  or  more)  is  arranged 
peripherally  inside  the  perforated  basket,  the  acid  being  supplied  by  the  tube,  m ;  the  basket, 
surrounded  by  the  jacket,  6,  and  the  cover,  z,  both  of  earthenware,  is  set  in  motion  by  the 
shaft,  p,  driven  by  the  belt,  r.  The  acid  is  driven  uniformly  through  the  cotton  by  centri- 
fugal force,  rises  through  the  ring  space,  c,  and  issues  from  the  holes,  s,  into  the  channel,  e, 
whence  a  pipe,  /,  carries  it  to  an  elevator  to  be  again  circulated.  The  operation  is  of 
short  duration,  and  the  red  vapours  are  emitted  from  the  tube,  g.  During  nitration,  the 
velocity  of  the  drum  is  relatively  low,  but  at  the  end  the  velocity  is  increased  ;  the  nitrated 
cotton  can  then  be  taken  away  at  once  to  be  washed. 

Use  is,  however,  preferably  made  of  steel  centrifuges  with  circulation  of  the  acid,  as 
proposed  by  Selwig  and  Lange  ;  the  basket,  d,  is  perforated  (Fig.  191)  and  the  cover  is  of 
aluminium  and  hinged  and  is  furnished  with  a  large  tube,  o,  communicating  with  the  pipe 
of  an  aspirator,  n.  The  basket  is  moved  slowly  and  filled  with  the  nitric-sulphuric  mixture 
(e.g.  70  per  cent.  H2S04,  23  per  cent.  HN03  and  7  per  cent,  water)  up  to  the  top  edge  ; 
the  cotton  is  then  introduced  in  packets  (1  kilo  per  50  kilos  of  acid)  and  the  basket  given 
a  velocity  of  20  to  30  turns  per  minute.  This  movement  causes  the  acid  to  circulate 
continuously  through  the  cotton,  and  in  half  an  hour,  the  nitration  of  6  to  8  kilos  of  cotton 
is  complete  ;  the  acid  is  then  discharged  and  the  velocity  increased  to  remove  as  much 
acid  as  possible  from  the  cotton,  which  is  taken  out  and  washed  in  the  ordinary  way. 


236 


ORGANIC    CHEMISTRY 


Excessive  prolongation  of  the  centrifugal  ion  and  excessive  velocity  are  not  only  without 
advantage  but  involve  increased  danger  of  explosion. 

From  August  1905  in  the  Royal  Gunpowder  Factory  at  Waltham  Abbey  (where  2000 
tons  are  produced  per  annum),  guncotton  has  been  made  by  the  displacement  process  of 
J.  M.  and  W.  Thomson  and  Nathan,  which  is  briefly  as  follows. 


FIG.  191. 

Into  the  earthenware  basins,  which  are  furnished  with  aluminium  covers  (Fig.  1 92)  and  are 
connected  in  groups  of  four  by  means  of  leaden  pipes  and  also  communicate  with  exhausters, 
600  litres  of  the  nitric  -sulphuric  mixture  are  placed  ;  about  10  kilos  of  cotton  are  then 
introduced  in  small  portions  into  each  vessel  and  are  pressed  with  perforated  wrought -iron 
plates.  The  nitration  lasts  two  and  a  half  hours,  and  at  the  end  water  is  introduced 
above  the  perforated  plate,  this  displacing  at  the  bottom  a  corresponding  quantity  of  the 
acid  ;  the  acid  thus  recovered  is  reinforced  with  oleum  and  strong  nitric  acid.  The 
displacement  lasts  3  hours,  after  which  the  mass  is  centrifuged  and  the  cotton  washed, 
rendered  stable,  pulped,  &c. 


FIG.  192. 

Since  guncotton  should  have  a  very  definite  nitrogen  content,  different  from  that  of 
collodion-cotton  used  to  gelatinise  nitroglycerine  (see  later),  the  process  of  nitration  is  care- 
fully followed  by  numerous  rapid  analyses  until  suitable  conditions  are  found  for  obtaining 
a  constant  product  ;  after  this  has  been  done,  the  final  control  is  sufficient.  It  has  been 
proposed  to  follow  the  extent  of  nitration  of  cellulose  by  observing  its  behaviour  towards 
polarised  light.  In  recent  years  it  has  been  shown  that  guncotton  of  more  constant  type 
and  more  readily  rendered  stable  is  obtained  if  the  acid  mixture  is  renewed  for  each  nitration  ; 
the  last  processes  described  are  hence  to  be  preferred. 

WASHING.  The  nitrocellulose  from  the  centrifuge  is  passed  directly  into  the  oval 
washing  vessel  (see.  Fig.  193),  which  has  a  longitudinal  partition  down  the  middle  (like 
the  hollander  machines  us-ed  in  paper-making),  and  in  which  a  shaft  furnished  with  beaters 


PULPING 


237 


mixes  the  whole  mass  with  water  ;  the  latter  is  constantly  renewed  and  the  washing 
continued  until  the  acid  reaction  towards  litmus  paper  disappears  (2  to  3  hours).  The  washed 
guncotton  is  either  centrifuged  again  or  put  to  drain  in  wooden  baskets.  Although  it  no 
longer  exhibits  an  acid  reaction,  yet,  as  was  shown  by  J.  Tonkin  in  1862  and  by  Abel  in 
1865  (in  England),  it  still  contains  acid  or  rather  unstable  sulphuric  esters  in  the  small 
channels  of  the  fibres. 

To  separate  these  remaining  traces  of  acid,  the  nitrocellulose  is  rendered  stable  by 
boiling  it  for  two  consecutive  periods  of  12  hours  each  with  water  in  wooden  vats  fitted  with 
perforated  false  bottoms  (one  vat  holds  even  more  than  1000  kilos  of  the  cotton),  beneath 
which  steam  is  passed.  Then  follow  four  more  boilings  of  4  hours  each  with  water  (formerly 
one  or  two  boilings  with  calcium  carbonate  were  also  carried  out),  and  finally  two  or  three 
boilings  each  of  2  hours  with  fresh  water.  This  system  of  washing  was  proposed  by 
Dr.  Robertson  and  employed  with  advantage  in  the  Government  Factory  at  Waltham  Abbey ; 
it  lasts  altogether  48  hours,  is  preferable  to  that  in  which  the  boilings  are  short  at  the 
beginning  and  long  at  the  end,  and  especially  to  that  where  boiling  with,  soda  is  interposed, 
as  the  soda  hydrolyses  the  nitrocellulose  and  transforms  it  partially  into  collodion -cotton 
poor  in  nitrogen  and  soluble  in  alcohol-ether. 

Some  of  the  boiling  may  be  dispensed  with  if  the  nitrocellulose  is  steamed  in  closed  vats. 


FIG.  193. 

PULPING.  In  spite  of  all  the  washing  and  boiling  to  which  it  is  subjected,  the  guncotton 
persistently  retains  a  trace  of  acid,  and  to  remove  this,  the  cotton  is  thoroughly  defibred 
(pulped)  as  was  proposed  by  Tonkin  and  by  Abel  in  1865.  This  operation  is  carried  out  in  hoi- 
landers  similar  to  those  used  for  the  preceding  washing  and  identical  with  those  used  in  the 
manufacture  of  cellulose  for  paper  (see  later,  section  on  Paper,  for  figures  and  cross -sections). 

Pulping  lasts  from  5  to  8  hours,  according  to  the  fineness  required,  but  if  it  is  incomplete, 
inconveniences  are  met  with  in  the  subsequent  compression,  the  desired  density  not  being 
attainable  ;  also  if  pulping  is  carried  too  far,  the  compression  is  disturbed  in  another 
way.  Guttmann  proposed  the  use  of  hot  water  in  pulping,  and  this  possesses  several 
advantages  in  addition  to  saving  time.  In  the  large  wooden  vats,  'as  much  as  200  kilos 
of  guncotton  can  be  treated  at  one  time.  In  some  cases  a  little  calcium  carbonate  is 
added  to  guncotton  to  preserve  it  and  to  neutralise  any  residual  acid  ;  it  is  added  in  powder 
just  before  the  completion  of  pulping. 

If  the  guncotton  thus  prepared  does  not  answer  the  rigorous  tests  to  which  it  is  sub- 
jected (see  later,  Tests  of  Stability),  it  is  rendered  stable  by  again  boiling  it  for  some  hours 
with  water  in  large  wooden  tanks  (sometimes  lined  with  lead),  jets  of  steam,  and  also  of  air  to 
keep  the  mass  moving,  being  passed  in.  In  order  to  separate  the  water,  the  mass  is  placed 
in  suitable  centrifuges  fitted  with  drums  of  fine  metal  gauze  entirely  surrounded  by  linen  ; 
in  other  cases,  the  water  is  separated  as  in  paper-mills  by  placing  the  mass  in  chambers 
having  perforated  brass  floors  covered  with  cloth,  the  pulp  drained  in  this  way  being  finally 
centrifuged.  The  water  separated  from  the  pulp  is  allowed  to  stand  in  suitable  vessels 
to  deposit  the  finer  fibres  it  has  carried  away.  After  centrifugation,  the  pulp  contains 
about  25  to  30  per  cent,  of  water  and  in  this  state  it  can  be  kept  safely  in  zinc  boxes,  in 


238 


ORGANIC    CHEMISTRY 


which  it  can  be  transported  if  it  is  slightly  compressed  and  the  cover  of  the  box  soldered. 
If  properly  prepared,  guncotton  should  not  contain  more  than  3-5  to  4  per  cent,  of  collodion- 
cotton  (soluble  in  alcohol-ether),  but  in  England  7  to  8  per  cent,  is  allowed. 

COMPRESSION  OF  GUNCOTTON.  For  military  purposes,  that  is,  for  cartridges 
and  for  the  blocks  used  for  charging  torpedoes,  the  still  moist  guncotton  is  strongly  com- 
pressed to  render  it  safer  and  more  powerful  owing  to  the  increased  charging  density 
(see  above),  which  reaches  the  value  1-2  with  pressures  of  500  to  1000  atmos.  Fig.  194 
shows  in  section  a  Taylor  and  Challen  hydraulic  press  used  for  this  purpose  ;  this  is  set 
up  in  an  isolated  room  and  can  be  controlled  from  a  distance  so  as  to  avoid  any  great  amount 
of  damage  in  case  of  explosion  during  the  compression,  this  mostly  happening  if  any  hard 
foreign  body  chances  to  be  present  in  the  guncotton. 

To  obtain  the  greatest  density,  the  pulp  is  first  washed  with  hot  water  and  slightly 
compressed  in  the  mould,  d,  by  means  of  the  lever,  h,  the  water  being  drawn  away  under 
the  perforated  base,  c  (covered  with  steel  gauze),  by  a  pump  connected  with  the  tube,  I. 


FIG.  194. 


The  partitions,  I,  are  raised  and  the  mould  passed  through  an  aperture  in  the  wall,  M 
(which  serves  as  a  protection  for  the  workmen),  and  thus  above  the  plate,  n,  of  the  hydraulic 
press  ;  this  plate  is  kept  horizontal  by  four  columns,  S'.  The  mould  is  raised  by  the  piston, 
t ,  of  the  press  so  that  it  is  pressed  against  a  die,  r,  fixed  to  the  cover,  q.  This  cover  is  held 
fast  by  the  four  columns  so  that  the  die  penetrates  the  mould  and  compresses  the  cotton 
under  a  pressure  of  800  to  1000  atmos.  The  degree  of  humidity  after  the  compression  is 
about  10  per  cent.,  and  at  each  operation  a  block  of  1  kilo  is  made,  the  shape  being  adapted 
to  that  of  the  projectile.  Thus  compressed,  guncotton  is  so  hard  and  compact  that  it  can 
be  worked  quite  safely  with  the  plane,  saw,  or  boring  tool,  a  fine  jet  of  water  being  directed 
at  the  point  where  the  cutting  is  taking  place.  To  prevent  compressed  guncotton  from 
losing  moisture  and  from  becoming  mouldy,  it  is  dipped  in  molten  paraffin  wax  ;  or,  better, 
it  is  immersed  for  a  moment  in  ethyl  acetate  (or  acetone),  which  dissolves  a  little  nitro- 
cellulose at  the  surface  and  forms  a  kind  of  impermeable  varnish. 

The  theoretical  yield  of  dry  guncotton  is  185  kilos  per  100  kilos  of  dry 
cotton  ;  practically  171  to  176  kilos  are  obtained. 

USES  OF  GUNCOTTON.  For  the  charging  'of  torpedoes,  moist  com- 
pressed guncotton  has  replaced  all  other  explosives.  It  is  used  also  for  rilling 
grenades,  which  are  then  covered  with  molten  paraffin  wax  to  unite  the  grenade 
and  the  explosive  ;  explosion  is  effected  by  a  detonator  of  dry  guncotton.  It 
is  made  also  into  compressed  cartridges  for  use  in  mines,  a  cavity  being  left  for 
the  detonating  cap  and  the  fuse. 


COLLODION-COTTON  289 

Mixtures  of  granulated  guncotton  and  nitrates  are  placed  on  the  market 
undsr  the  namss  of  tonite,  potentite,  &c.  Abel  obtained  beautiful,  pyrotechnic 
effects  by  saturating  guncotton  with  solutions  of  various  mineral  salts  capable 
of  imparting  different  colours  to  the  flame.  It  is  sometimes  used  for  filtering 
acids,  alkalis,  and  solutions  of  permanganate,  being  resistant  to  these  reagents 
in  the  cold.  Also  it  is  in  some  cases  employed  as  an  electric  insulator  and 
for  bandaging  purulent  sores  and  wounds,  being  first  saturated  with 
potassium  permanganate. 

COLLODION-COTTON  FOR  GELATINE  DYNAMITE,  DYNAMITE,  AND 
SMOKELESS  POWDERS.  During  recent  years,  a  different,  less  nitrated  nitrocellulose, 
collodion-cotton,  has  assumed  very  great  importance  in  the  manufacture  of  smokeless 
explosives.  On  the  other  hand,  guncotton  itself  has,  of  late  years,  been  largely  replaced 
by  compressed,  crystalline,  or  fused  trinitrotoluene  (see  Part  III),  especially  for  military 
and  naval  purposes.  Collodion -cotton  was  at  one  time  thought  to  be  dinitrocellulose, 
soluble  in  a  mixture  of  alcohol  and  ether,  but  it  has  now  been  shown  to  be  a  mixture  of 
various  soluble  nitro -compounds,  which  are  formed  under  different  conditions  from  those 
yielding  guncotton.  Collodion -cotton  should  have  a  constant  nitrogen -content,  and  it 
should  be  readily  soluble  in  a  mixture  of  alcohol  (1  part)  and  ether  (2  parts),  giving  a 
dense  viscous  solution.  If  it  answers  these  requirements,  it  gelatinises  nitroglycerine  well 
and  dissolves  completely  in  it  ;  attention  is,  however,  also  paid  to  the  time  necessary 
for  gelatinisation. 

For  photographic  plates,  extensive  use  was  formerly  made  of  ethereal -alcoholic  solutions 
of  soluble  nitrocellulose  (collodion),  and  in  this  case  importance  was  attached  not  so  much 
to  the  viscosity  as  to  the  proportion  of  nitrocellulose  which  would  yield  an  elastic  film 
of  marked  resistant  properties.  For  this  purpose,  the  nitration  is  carried  out  at  a 
temperature  of  at  least  40°  to  50°,  so  that  the  resulting  collodion  is  less  viscous  ;  also 
the  nitrocellulose  is  not  pulped. 

The  cotton  is  immersed  for  60  to  90  minutes  in  a  mixture  of  1  part  of  96  per  cent, 
sulphuric  acid  (sp.  gr.  1-840)  and  1  part  of  75  per  cent,  nitric  acid  (sp.  gr.  1-442)  at  a 
temperature  of  about  40°. 

The  more  concentrated  the  acid  and  the  more  prolonged  its  action,  the  higher  will  be 
the  nitrogen -content,  but  the  viscosity  will  not  be  decreased  ;  a  high  temperature,  however, 
results  in  diminution  of  the  proportion  of  nitrogen  and  also  of  the  viscosity. 

The  nitration  can  be  effected  in  the  cold,  but  more  concentrated  acids  and  more  pro- 
longed action  are  then  required.  After  nitration  collodion -cotton  intended  for  the 
manufacture  of  gelatine  dynamite  goes  through  all  the  operations  of  washing,  pulping, 
and  boiling  employed  with  guncotton. 

Collodion  cotton  for  gelatine  dynamite  or  smokeless  powder  must  be  subjected  to  a 
drying  process.  Since  the  centrifuged  pulp  still  contains  30  per  cent,  of  water,  whilst 
nitrocellulose  begins  to  decompose  at  70°  (or  even  at  50°  if  badly  prepared)  and  in 
the  dry  state  is  very  sensitive  to  shock  or  percussion,  the  drying  of  collodion-cotton  con- 
stitutes a  very  dangerous  operation.  At  one  time  it  was  dried  by  means  of  indirect  steam, 
but  nowadays  it  is  placed  on  iron  plates  heated  to  40°  to  50°.  When  dry,  it  sometimes 
becomes  electrified  on  rubbing,  and  this  phenomenon  explains  the  frequent  spontaneous 
fires  formerly  occurring  in  the  drying  ovens.  Guttmann  prefers  to  dry  the  collodion-cotton 
on  copper  plates  connected  with  the  earth  by  wires  (to  discharge  the  electricity).  These 
plates  are  perforated  with  conical  holes  0-25  mm.  wide  at  the  top  and  1  mm.  at  the  bottom  ; 
strips  of  leather  are  used  to  prevent  rubbing  of  the  metal  parts.  In  these  ovens,  the  pulp 
is  spread  out  and  is  subjected  to  the  action  of  a  current  of  air  heated  to  40°  (in  some  case," 
also  dried)  and  in  two  days  the  mass  is  dry,  not  more  than  0-1  per  cent,  of  moisture  being 
then  present.  The  dried  material  is  then  carefully  placed  in  rubber  bags  and  stored  in 
air-tight  boxes. 

The  drying  ovens  are  provided  with  alarm-thermometers,  which  also  regulate  the 
temperature  automatically. 

Drying  in  a  vacuum  is  also  employed  (especially  with  fulminate  of  mercury)  and  is  then 
more  rapid  and  takes  place  at  a  lower  temperature,  while  the  danger  of  an  explosion 
is  diminished  owing  to  the  absence  of  the  tamping  effect  of  the  atmospheric  pressure  (see 
p.  221). 


240  ORGANIC    CHEMISTRY 

Collodion -cotton  for  making  ballistite  (see  later)  should  contain  11-75  to  11-95  per  cent, 
of  nitrogen,  whilst  that  for  ordinary  gelatine  dynamites  contains  as  much  as  12  per  cent. 

SMOKELESS  POWDERS.  Even  50  years  ago  attempts  were  made  to  diminish  the 
smoke  produced  by  ordinary  gunpowder  by  diminishing  the  amount  of  sulphur  present, 
but  its  relations  to  the  nitre  and  carbon  cannot  be  greatly  altered.  Potassium  nitrate  was 
then  replaced  by  ammonium  nitrate,  but  this  was  found  to  be  too  hygroscopic  ;  yet  later, 
ammonium  picrate  was  employed  with  better,  but  still  not  satisfactory,  results.  In  1864 
Schulze  prepared  a  smokeless  powder  from  nitrocellulose  obtained  from  pure  wood-cellulose. 
It  gave  good  results  with  sporting  guns,  but  was  too  shattering  for  use  in  warfare,  and  the 
same  was  the  case  with  a  smokeless  powder  prepared  in  1882  by  Walter  Reid  by  granulating 
nitrocellulose  and  gelatinising  it  superficially  with  alcohol  and  ether. 

The  true  solution  of  this  important  problem  is  due  to  Vieille,  who  in  1884  found  that  the 
shattering  action  of  guncotton  could  be  transformed  into  a  progressive  (or  propellant)  action 
by  destroying  the  fibrous  structure  with  suitable  solutions.  To  attenuate  the  rapidity  of 
explosion  of  guncotton  it  must  be  made  as  dense  as  possible  (theoretically  the  fibre  free 
from  interstices  has  the  density  1-5)  and  this  cannot  be  done  practically  with  fibrous 
cotton  (even  when  pulped)  as  a  pressure  of  4000  atmospheres  would  be  necessary.  Vieille, 
however,  dissolved  or  gelatinised  the  nitrocellulose  and  then  recovered  it  by  evaporating 
the  solvent. 

With  the  smokeless  powder  prepared  by  Vieille  in  1885  the  velocity  of  projectiles  from 
cannon  was  increased  by  100  metres  per  second  over  that  obtained  with  ordinary  powder,  the 
pressure  in  the  cannon  being  the  same  in  the  two  cases  ;  hence  guns  of  smaller  calibre 
could  advantageously  be  employed. 

This  amounted  to  a  revolution  in  the  region  of  ballistics,  since,  in  addition  to  the  advan- 
tages of  no  smoke  or  ash,  and  of  the  use  of  lower  calibres,  there  was  also  the  possibility  of 
charging  empty  projectiles  with  these  explosives,  which  are  made  and  kept  so  safely. 
Gelatinisation  is  effected  by  solvents  of  nitrocellulose,  i.e.  by  ether,  acetone,  ethyl  acetate, 
nitroacetylglycerine,  &c.  (see  p.  223). 

I.  SMOKELESS  POWDERS   OF  PURE   NITROCELLULOSE.     The   quantity  of 
dry  nitrocellulose  (6  to  10  per  cent,  of  the  weight  of  solvent)  decided  on  is  introduced  into 
the  kneading  machine  (see  p.  243),  which  is  furnished  with  a  cover,  the  necessary  quantity 
of  solvent  being  then  added  and  the  kneading  continued  for  6  to  8  hours  ;  no  danger  of 
explosion  attends  this  process.     If  a  mixture  of  alcohol  and  ether  is  employed  as  solvent, 
less  highly  nitrated  cellulose  (collodion-cotton)  may  be  used  ;   the  30  per  cent,  of  water 
in  the  moist,  centrifugated  collodion-cotton  is  first  displaced  by  alcohol  and  the  mass  then 
centrifugated  again,  the  amount  of  alcohol  remaining  in  the  cotton  being  calculated  so 
that  the  quantities  of  ether  and  alcohol  required  in  the  kneading  machine  may  be  known. 
This  procedure  offers  the  great  advantage  of  avoiding  the  very  dangerous  drying  of  the 
collodion-cotton.     When  the  gelatine  in  the  kneading  machine  is  homogeneous  and  cold, 
it  is  taken  to  the  rolls,  which  are  similar  to  those  employed  for  ballistite  (see  later). 

The  principal  object  of  rolling  is  to  increase  the  density  of  the  gelatine  and  to  give  it 
a  uniform  composition.  It  is  carried  out  between  ordinary  cylindrical  rolls  with  increasing 
pressure,  so  that  with  repeated  rollings  between  different  rolls,  sheets  varying  in  thickness 
from  half  a  centimetre  to  a  fraction  of  a  millimetre  can  be  obtained.  The  rolls  are  heated 
by  means  of  steam  to  a  temperature  not  exceeding  60°,  so  that  the  solvent  is  gradually 
eliminated  from  the  whole  mass.  One  of  the  most  commonly  used  rolling  machines  for 
thick  sheets  is  shown  in  Fig.  195  and  one  for  thin  sheets  in  Fig.  196.  In  France  preference 
is  given  to  hydraulic  presses  which  give  a  still  more  uniform  product. 

The  thin  sheets  can  then  be  cut  into  fine  strips  by  means  of  rollers  with  superposed 
knives,  as  shown  in  Figs.  197  and  198.  Some  machines  give  a  product  like  cut  tobacco. 
If  the  strips,  as  they  issue  from  the  machine,  are  passed  under  other  cutters  perpendicular 
to  the  first,  pieces  of  various  lengths  or  cubes  can  be  obtained  which  are  convenient  to  carry 
and  to  use. 

Since  these  smokeless  powders  still  contain  small  quantities  of. free  solvent  the  cut 
pieces  are  dried  in  a  well -ventilated  oven  at  about  40°.  This  drying  is  now  carried  out  more 
rapidly  and  with  less  danger  in  a  vacuum  (see  p.  239). 

II.  SMOKELESS  POWDERS  OF  NITROCELLULOSE  AND  NITROGLYCERINE. 
A.     As  we  have  already  seen,  in  dealing  with  the  theory  of  explosives,  the  explosion  of 
nitroglycerine  is  accompanied  by  the  liberation  of  unused  oxygen  ;  on  the  other  hand,  it 


GELATINE    DYNAMITES,    ETC. 

is  known  that  guncotton  does  not  contain  sufficient  oxygen  for  the  complete  combustion 
of  the  carbon  and  hydrogen  present  in  the  nitrocellulose  molecule. 

In  1875,  A.  Nobel  conceived  the  happy  idea  of  associating  the  two  substances  by  dis- 
solving in  nitroglycerine  a  certain  quantity  of  soluble  nitrocellulose,  that  is,  that  used 
in  the  manufacture  of  collodion.  This  procedure  gives  gelatines  of  varying  consistency 


FIG.  195. 


FIG.  196. 


according  to  the  quantity  of  nitrocellulose  (collodion-cotton)  dissolved.  Blasting  gelatine 
is  made  from  90  to  93  per  cent,  of  nitroglycerine  and  7  to  10  per  cent,  of  dry  collodion- 
cotton  ;  gum  dynamites,  on  the  other  hand,  contain  about  97  per  cent,  of  nitroglycerine 
and  3  per  cent,  of  collodion-cotton,  and  when  they  are  mixed  with  about  one-third  of  their 
weight  of  absorbent  substances  (wood-meal,  rye-flour,  sodium  or  ammonium  nitrate)  they 


FIG.  197. 


FIG.  198. 


form  the  gelatine  dynamites,  which  are  still  plastic,  although  less  so  than  the  gum  dynamites, 
and  are  also  less  violent  and  hence  serve  well  for  mining  purposes.  A  common  type  of 
gelatine  contains,  for  instance,  62-5  per  cent,  of  nitroglycerine,  2-5  per  cent,  of  collodion- 
cotton,  25-5  per  cent,  of  sodium  nitrate,  8-75  per  cent,  of  wood  meal,  and  0-75  per  cent,  of 
sodium  carbonate  ;  it  has  a  specific  gravity  of  1-5,  is  exploded  with  a  No.  1  fulminate  of 
mercury  cap,  and  is  sold  in  Austria  for  No.  I  dynamite,  whilst  gelignite  is  sold  for  No.  II 
dynamite  and  contains  45  to  50  per  cent,  of  gum  dynamite  and  about  50  per  cent,  of 
absorbents  as  above. 

II  16 


242  ORGANIC    CHEMISTRY 

At  Christiania  a  non -congealing  gum  dynamite  is  made  from  blasting  gelatine  and  a 
little  nitrobenzene  and  ammonium  nitrate  ;  it  has  a  specific  gravity  of  1-49  and  is  less 
effective  than  the  gelatine  dynamites. 

For  military  purposes  (torpedoes,  cannon,  &c.),  as  much  as  4  per  cent,  of  camphor  is 
added  in  Italy,  Austria,  and  Switzerland  ;  these  gelatines  are  thus  rendered  insensitive 
and  very  safe,  and  they  require  special  detonators  (e.g.  a  mixture  of  60  per  cent,  of  nitro- 
glycerine and  40  per  cent,  of  collodion-cotton  or  compressed  guncotton). 

In  certain  commercial  products  the  collodion -cot  ton  is  replaced  by  nitrated  wood  or 
straw,  while  nitro benzenes,  nitrotoluenes  (especially  liquid  dinitrotoluene),  &c.,  are  used 
instead  of  nitroglycerine.1 

Gelatine  and  gum  dynamites  have  the  appearance  of  plastic  masses,  the  latter,  which 
has  the  sp.  gr.  1-6,  being  especially  horny  and  translucent.  Gum  dynamite  sometimes 
exudes  a'little  nitroglycerine  and  so  loses  in  shattering  force  ;  when  heated  for  a  long  time 
at  70°,  it  swells  up,  becomes  spongy  and  decomposes  with  formation  of  red,  nitrous  vapours  ; 
it  sometimes  ignites  in  metal  boxes  when  exposed  to  the  sun.  It  is  less  sensitive  even  than 
dynamite  (about  six  times  less)  to  percussion  and  special  caps  of  gelatine  dynamite  are 
required  to  explode  it.  It  serves  well  for  use  in  war,  since  it  is  insensitive  to  discharges, 
and  to  render  it  still  less  prone  to  detonation  by  influence  it  is  mixed  with  a  little  camphor. 
When  20  per  cent,  of  collodion -cotton  is  dissolved  in  nitroglycerine,  a  gum  dynamite  is 
obtained  which  is  not  exploded  by  the  most  powerful  caps.  And  ballistite,  which  contains 
30  to  50  per  cent,  of  collodion-cotton,  requires  special  detonators.  After  freezing  and 
thawing,  it  becomes  more  sensitive  and  dangerous,  as  is  the  case  with  dynamite.  It  has  a 
greater  shattering  power  than  dynamite  and  acts  better  than  this  under  water,  which  does 
not  wash  away  the  nitroglycerine  so  easily.  Exudation  of  nitroglycerine  occurs  more  readily 
than  with  dynamite  and  causes  some  degree  of  danger.  It  is  used  as  a  basis  for  the  manu- 
facture of  smokeless  powder.  Gelatine  dynamite  is  safer  to  handle  and  store  than  ordinary 
dynamite,  which  it  is  largely  replacing. 

The  manufacture  of  these  gelatinised  dynamites  requires  collodion-cotton,  which  is 
very  carefully  prepared  and  is  completely  soluble  in  a  mixture  of  alcohol  and  ether,  in 
addition  to  which  it  must  possess  as  great  a  proportion  of  nitrogen  as  possible.  When  it 

1  It  is  impossible  at  the  present  time  to  compare  the  various  commercial  brands  of  dynamite  of  different 
countries:  or  even  of  one  country,  so  varied  are  the  types  and  the  ratios  of  the  components,  sometimes  when  the 
commercial  name  is  the  same.  Thus  No.  1  ammonia  dynamite  (French)  contains  40  per  cent,  of  nitroglycerine, 
45  per  cent,  of  ammonium  nitrate  (this,  when  pure,  is  not  hygroscopic),  5  per  cent,  of  sodium  nitrate,  and  10  per  cent, 
of  wood-meal  or  wheat-flour  ;  the  No.  2  quality  of  the  same  brand  contains  20  per  cent,  of  nitroglycerine,  75  per 
cent,  of  ammonium  nitrate,  and  5  per  cent,  of  wood-meal  In  Germany, the  name  Gelatine  Dynamites  is  given  to 
all  mixtures  prepared  from  explosive  yum  (96  per  cent,  nitroglycerine  gelatinised  with  4  per  cent,  collodion-cotton 
and  a  nitre-base  as  absorbent.  In  England,  however,  No.  2  gelatine ^dynamites  are  called  gelignites,  and  are  often 
formed  of  65  per  cent,  of  the  gum  and  35  per  cent,  of  absorbents  (75  p*er  cent,  nitre,  24  per  cent,  wood-meal — wood- 
pulp  used  for  paper,  in  a  dried  state — and  1  per  cent,  of  soda).  In  Austria,  dynamite  I  is  made  from  65-5  per 
cent,  of  nitroglycerine,  2-1  per  cent,  of  collodion-cotton,  7-41  per  cent,  of  wood-meal,  24-85  per  cent,  of  nitre,  and 
0-26  per  cent,  of  soda  ;  dynamite  II  contains  46  per  cent,  of  nitroglycerine,  &c.,  and  dynamite  II  A,  38  per  cent, 
of  nitroglycerine,  &c.  In  France,  gelatine  dynamites  are  called  gums,  and  are  prepared  in  very  varied  forms, 
e.g.  gum  MB  with  74  per  cent,  of  nitroglycerine,  gum  D  with  69-5  per  cent.,  and  gum  E  with  49  per  cent.  ; 
then  there  are  dynamite  gelatini-  1,  2«,  26,  and  2c  (the  last  with  43  per  cent,  of  nitroglycerine,  &c.),  &c.  In 
Belgium,  gelatine  dynamites  are  called  forcites  ;  forcite  extra  contains  74  per  cent,  of  nitroglycerine,  superforcite 
64  per  cent.,  forcite  No.  2,  36  per  cent.,  Ac. 

In  England  the  types  most  commonly  used  are  :  dynamite  JVo.  I,  with  75  per  cent,  of  nitroglycerine  ;  gelignite 
with  65  per  cent,  of  gelatinised  nitroglycerine  (97  per  cent,  of  nitroglycerine),  25  per  cent,  potassium  nitrate  and 
10  per  cent,  wood-meal ;  blasting  gelatine  with  93  per  cent,  of  nitroglycerine  and  7  per  cent,  of  collodion-cotton  ; 
gelatine  dynamite  with  80  per  cent,  of  gelatinised  nitroglycerine  (with  3  per  cent,  of  collodion -cotton),  15  per  cent, 
of  potassium  nitrate  and  5  per  cent,  of  wood-meal. 

In  Italy  there  is  dinamite-gomma  A  (or  simply  gomma  A,  corresponding  with  the  French  gomme  extra-forte) 
formed  from  92  per  cent,  of  nitroglycerine  and  8  per  cent,  of  collodion-cotton  ;  gomma  B  (corresponding  with  the 
French  gomme  a  la  soude)  with  83  per  cent,  of  nitroglycerine,  5  per  cent,  of  collodion-cotton,  8  per  cent,  of  sodium 
nitrate,  3-7  per  cent,  of  wood-meal,  and  0-3  per  cent,  of  sodium  or  calcium  carbonate  or  ochre.  Commercially, 
however,  the  strength  is  given  in  terms  not  of  nitroglycerine  but  of  gelatine,  that  is,  the  starting  material  is  taken 
as  a  gelatine  formed  by  gelatinising  94  per  cent,  of  nitroglycerine  with  6  per  cent,  of  collodion-cotton,  to  which 
are  then  added  the  various  absorbents  ;  thus  gomma  B  contains  88  per  cent,  of  gelatine  (equivalent  to  83  per  cent, 
of  nitroglycerine).  In  Italy  the  old  kieselguhr  dynamite  is  no  longer  used  and  is  replaced  by  the  so-called  gelatine- 
dinamiti,  which  are  marked  with  various  letters  and  numbers  ;  thus  No.  0,  containing  74  per  cent,  nitroglycerine, 
5  per  cent,  collodion-cotton,  15-5  per  cent,  sodium  nitrate,  5  per  cent.  Vood-meal,  and  0-5  per  cent,  carbonates ; 
Q.D.No.  1,  with  70  to  72  per  cent,  nitroglycerine,  &c. ;  G.  D.  No.  2,  with  about  43  percent. nitroglycerine;  and 
dinamit  2fo.  3,  with  25  per  cent,  nitroglycerine,  54  per  cent,  sodium  nitrate,  19  per  cent,  wood-meal  and  cellulose, 
and  2  per  cent,  soda  and  yellow  ochre.  During  recent  years  there  have  also  been  prepared  in  Italy  gelatine- 
dinamiti  -  suggested  by  Dr.  Leroux — with  8  to  10  per  cent,  of  the  nitroglycerine  (of  No.  1)  replaced  by  as  much 
liquid  (.  initrotoluene,  which  gelatinises  cotton  well  and  gives  non-congealing  dynamites,  more  economical  and  almost 
as  powerful  as,  sometimes  more  powerful  than,  the  corresponding  gelatine  dynamites  ;  these  act  well  in  open  mines, 
but  give  large  quantities  of  unpleasant  fumes,  and  hence  are  unsuitable  for  use  in  galleries,  Ac. 


KNEADING 


243 


FIG.  199. 


is  not  well  prepared,  although  it  dissolves  in  alcohol  and  ether,  it  is  not  readily  and  entirely 
soluble  in  nitroglycerine,  or  it  does  not  retain  the  latter  completely  for  a  long  time.  The 
quality  of  the  collodion-cotton  depends,  then,  on  the  choice  of  a  good  cotton  and  on  exact 
conditions  of  nitration — duration,  purity  of  acids,  temperature. 

This  should  then  be  finely  subdivided  (pulped)  and  dry,  so  that  it  can  be  passed  through 
a  fine  sieve  before  being  mixed  with  the  nitroglycerine,  in  which  it  does  not  dissolve  well 
if  moist.  This  operation  of  gelatinisation  and  kneading  is  termed  in  French  petrinage. 
The  necessary  quantity  of  nitroglycerine  is  placed  in  wide,  shallow  vessels  of  copper 
or  lead  heated  externally  by  hot  water  (50°  to  60°).  After  30  to  60  minutes, 

when  the  temperature  has  reached 
45°  to  50°,  the  required  amount  of 
dry,  powdered  collodion  -  cotton  is 
added  in  small  quantities  and  mixed 
now  and  then  with  a  wooden  spade. 
It  is  then  left  for  a  couple  of  hours 
and  afterwards  thoroughly  mixed  by 
hand,  just  as  dough  is  mixed,  so  as 
to  form  a  homogeneous,  soft  paste  ; 
this,  on  cooling,  forms  a  more  or  less 
hard,  elastic,  translucent  gelatine 
which  constitutes  the  gelatine  or 
explosive  gum.  If,  instead  of  col- 
lodion-cotton alone,  absorbents  are  also  used,  gelatine  dynamites  are  obtained  ;  these 
are  converted  into  rolls  and  cartridges  with  the  machines  already  described  (p.  230). 
When  the  gelatine  is  not  intended  for  the  manufacture  of  ballistite  (see  later),  the 
conversion  into  cartridges  is  effected  by  means  of  an  Archimedean  screw  machine 
(boiidineuse),  similar  to  sausage-making  machines  (Fig.  199). 

The  mixing  for  causing  gelatinisation,  especially  if  other  substances  besides  collodion- 
cotton  are  added,  can  be  carried  out  in 
mechanical  kneading  machines  (Fig.  200) 
mounted  on  a  wooden  platform,  b,  which 
can  be  raised  by  screws  and  cog-wheels, 
g,  e,  and  h,  resting  on  supports,  a  a  ;  on 
this  platform  is  a  double -walled,  copper 
pan,  ij,  which  can  be  surrounded  with 
hot  water  and  can  be  moved  on  rollers. 
Above  are  the  bevel-wheels  and  pulleys 
for  working  the  stirrers,  q  and  r.  The 
nitroglycerine  is  first  heated  to  50°  by 
raising  the  temperature  of  the  water  in 
the  jacket  of  the  copper  pan,  the  latter 
being  then  raised  so  as  to  submerge  the 
stirrers  ;  the  ingredients  necessary  to  give 
the  required  type  of  gelatine  dynamite  are 
then  added.  Mixing  is  complete  in  an 
hour.  Other  forms  of  kneading  machine 
are  used,  e.g.  the  Werner-Pfleiderer  ma- 
chine, which  is  employed  for  smokeless 
powders  and  for  bread-making.  After 
cooling,  the  plastic  dynamite,  which  has 
a  yellowish,  translucent  appearance,  is 
removed  from  the  kneading  machine  to 
a  separate  building  to  be  converted  into  cartridges.  This  is  done  in  special  machines 
(boudineuses)  (Figs.  201  and  202),  furnished  with  endless  screws,  which  force  the  dyna- 
mite or  gum  from  a  hole,  B,  in  continuous  rolls,  these  being  collected  in  definite  lengths 
in  a  casing  of  parchment  paper  or  paraffined  paper,  C. 

B.  Military  Smokeless  Powders.  These  approach  the  gum  dynamites  in  character, 
but  contain  more  collodion -cotton,  so  that  they  are  safer  towards  shock  and  useful  as 
propellants  (only  slightly  shattering). 


FIG.  200. 


244 


ORGANIC    CHEMISTRY 


FIG.  201. 


The  most  important  type  is  that  prepared  by  Nobel  in  1888  under  the  name  of  ballistite 
(after  he  had  been  preparing  since  1878  gum  dynamite  by  gelatinising  nitroglycerine  with 
6  to  10  per  cent,  of  collodion-cotton).  Ballistite  contains  about  50  per  cent,  of  nitroglycerine 
and  50  per  cent.,  or  even  more,  of  collodion-cotton  (with  11-2  to  11-7  per  cent.  N).  To 
incorporate  these  two  substances  thoroughly  and  so  that  there  is  no  danger  in  the  subse- 
quent operations,  use  is  made  of  Lundholm  and  Sayer's  process,  by  which  the  constituents 

are  united  in  presence  of  a  liquid  able  to 
dissolve  neither  of  them.  This  liquid  is 
merely  water,  0-5  to  1  per  cent,  of  aniline 
being  added  to  fix  the  acids  liberated  and 
thus  increase  the  stability  of  the  ballistite. 
The  pulped  collodion-cotton,  contain- 
ing 30  per  cent,  of  water,  as  it  comes  from 
the  centrifuges  (after  boiling)  is  introduced 
into  a  cylinder  of  sheet-lead  containing 
water  at  60°.  The  mass  is  well  stirred  by 
compressed  air  and  the  finely  divided 
nitroglycerine  passed  in  by  means  of  a 
compressed-air  injector.  The  agitation 
is  continued  until  all  the  nitroglycerine 
is  incorporated  with  the  cotton,  none 
remaining  suspended  in  the  water.  The 
mixture  is  left  in  this  condition  for  some 
weeks  and  is  then  centrifuged.  It  is  next 
rolled  at  40°  to  50°  in  various  machines 
similar  to  those  shown  in  Figs.  195  and 
196  on  p.  241.  The  sheets  thus  obtained 
are  then  cut  into  strips,  wires  (flite, 
cordite  *),  cubes,  granules,  or  shreds  (lanite).  The  granulated  smokeless  powder  thus 
obtained  is  sieved,  and  if  in  large  strips  these  are  sifted  by  hand  ;  it  is  then  placed  in  the 
drying  oven,  while  the  scraps  are  softened  in  a  warm  bath  and  again  pressed.  Ballistite 
is  almost  brown  in  colour,  has  a  sp.  gr.  1-63  to  1-65,  and  is  practically  unaffected  by 
moisture  ;  it  inflames  at  180°  without  exploding.  The  gases  formed  in  its  explosion 
contain  no  nitrous  vapours  and  do  not  corrode  the  firearms. 

With  some  smokeless  powders,  attempts  have  been  made  to  replace  the  nitrocellulose 
by  nitrated  starch  and  the  liquid 
solvents  by  the  corresponding  va- 
pours, but  no  advantage  has  yet  been 
procured  in  this  way.  Explosive 
gelatines  can  also  be  obtained  by 
adding  metallic  nitrates  (of  barium 
or  potassium)  to  collodion -cotton  ; 
these  have  diminished  power  but 
possess  the  advantage  of  being  readily 
inflammable.  Mixtures  of  collodion - 
cotton  and  nitropenta-erythritol  have 
recently  been  prepared  for  the  use 
of  large-bore  artillery. 

FIG.  202. 

PROPERTIES  OF  SMOKE- 
LESS POWDERS.     Those  formed  of  nitrocellulose  alone  are  hard  ;  ballistite 

1  CordUe  is  a  smokeless  powder  in  filaments  like  hollow  twine.  Modern  cordites  contain  65  per  cent,  of  guncotton 
(not  collodion-cotton),  30  per  cent,  of  nitroglycerine,  and  5  per  cent,  of  vaseline.  Guncotton,  which  is  Jin- 
soluble  (to  the  extent  of  90  per  cent.)  in  alcohol,  ether,  or  even  nitroglycerine,  can  also  be  gelatinised  by  the  action 
of  a  common  solvent,  e.g.  acetone,  which  gives  a  colloidal  solution  persisting  even  after  evaporation  of  the  solvent. 
The  dry  guncotton  is  first  mixed  by  hand  with  nitroglycerine,  the  mass  being  then  introduced  into  an  ordinary 
kneading  machine,  which  is  of  bronze  and  is  jacketed  to  allow  of  water-cooling  ;  the  acetone  (20  kilos  per  100  kilos 
of  the  paste)  is  then  added  and  kneading  continued  for  at  least  3  hours,  after  which  the  vaseline  is  mixed  in  for 
some  time.  The  mass  tends  to  heat  and  must  be  cooled.  At  the  end  of  the  operation,  lumps  of  the  paste,  roughly 
cylindrical  in  form,  are  introduced  into  the  cylinder  of  the  cordite  press,  whichis  similar  to  that  used  for  making 
macaroni.  The  threads  of  varying  thickness,  length,  and  shape  of  cross-section  thus  obtained  are  then  dried  at 
40°  for  5  to  8  days. 


MELINITE,    LYDDITE  245 

is  not  so  hard,  and  even  in  thick  strips  can  be  bent  and  then  broken  like 
a  very  hard  paste.  They  are  very  resistant  to  the  action  of  water  and 
so  have  a  great  advantage  over  ordinary  powders,  which  are  destroyed  by 
water.  They  also  possess  the  advantages  of  a  high  density,  1-6  or  more 
(see  p.  218). 

Whilst  Vieille's  smokeless  powder  (gelatine  of  pure  guncotton)  withstands 
all  ordinary  conditions  of  temperature  and  moisture,  ballistite,  on  the  other 
hand,  gradually  loses  nitroglycerine  and  so  undergoes  change  of  its  properties 
if  the  humidity  of  the  atmosphere  oscillates  much.  But  these  conditions  are 
rarely  met  with  in  practice,  and  ballistite  is  used  not  only  by  the  Italian  army 
and  navy,  but  also  by  other  Governments,  and  is  in  some  ways  superior  to  the 
cordite  used  in  the  English  and  also,  to  a  certain  extent,  in  the  Italian  armies. 
In  1906,  the  proportions  of  the  components  of  cordite  were  varied  slightly 
and  the  form  altered  to  that  of  ribbons,  being  then  known  as  axite. 
Smokeless  powders  withstand  the  blow  of  a  projectile  and  require  special 
detonators,  fulminate  of  mercury  not  giving  good  results.  They  are  exploded 
by  compressed  guncotton  caps,  which  in  their  turn  are  exploded  by  fulminate 
of  mercury. 

If  accidentally  ignited,  smokeless  powders  are  not  very  dangerous,  since 
they  do  not  explode,  but  regard  must  be  paid  to  the  very  high  temperatures 
(above  3000°)  produced,  as  these  will  melt  iron,  stone,  &c. 

POWDERS  WITH  PICRATE  BASES.  As  early  as  the  fifteenth  century  an  alchemist 
obtained  an  explosive  substance  by  treating  a  kind  of  tar  with  aqua  regia,  but  this  acquired 
no  importance  in  comparison  with  ordinary  gunpowder.  The  explosive  properties  of 
picric  acid  and  its  salts  were  studied  in  the  second  half  of  the  nineteenth  century  and  assumed 
considerable  importance  when,  in  1886,  Turpin  prepared  melinite  from  70  per  cent,  of  picric 
acid  and  30  per  cent,  of  collodion -cotton  previously  rendered  soluble  with  alcohol  and 
ether  ;  this  was  regularly  used  for  some  years  by  the  French  army  in  place  of  dynamite. 
At  the  present  time  fused  picric  acid  (m.pt.  122°;  sp.  gr.  1-6)  is  poured  into  cartridges 
containing  a  fulminate  of  mercury  cap  and  powdered  picric  acid. 

Weight  for  weight,  picric  acid  is  less  effective  than  dynamite,  but,  measured  by  volume, 
its  power  is  greater  than  that  of  dynamite,  the  specific  gravity  of  which  is  1-5.  It  has  also 
the  advantage  over  dynamite  in  that  it  does  not  freeze,  being  already  in  the  solid  state. 

In  England,  melinite  was  followed  in  1888  by  lyddite,  containing  about  87  per  cent,  of 
picric  acid,  10  per  cent,  of  nitrobenzene,  and  3  per  cent,  of  vaseline.  This  is  poured  in  a 
molten  state  into  the  cartridges  and  is  exploded  with  ammonium  picrate  detonators  ; 
it  is  highly  resistant  to  shock.  It  undergoes  decomposition  fairly  readily,  giving  poisonous 
gases. 

These  and  other  picric  acid  or  ammonium  picrate  explosives  have  suffered  considerably 
in  importance  since  the  introduction  of  the  smokeless  powders  described  above.  The  pro- 
perties and  manufacture  of  picric  acid  will  be  described  in  the  section  dealing  with  benzene 
derivatives. 

SPRENGEL  EXPLOSIVES.  In  1 871  H.  Sprengel,  starting  from  the  fact  that  explosion 
is  nothing  but  instantaneous  combustion,  conceived  the  idea  of  preparing  explosives  by 
mixing  a  readily  combustible  substance  with  one  possessing  considerable  oxidising  pro- 
perties ;  the  substances  separately  are  not  explosive  but  become  so  when  mixed,  mixing 
taking  place  only  at  the  spot  where  the  explosive  is  to  be  used. 

This  idea  was  taken  up  later  by  Hellhoff,  who  mixed  nitric  acid  with  nitrated  hydro- 
carbons, and  more  effectually  by  Turpin  and  by  R.  Pictet,  who  mixed  nitrogen  peroxide 
(N2O4)  with  various  nitrated  organic  compounds  and  also  with  CS2  (panclastite,  fulgurite, 
&c. )  ;  but  these  explosives  never  came  into  practical  use. 

Another  form  of  explosive  of  the  Sprengel  type  is  that  with  ammonium  nitrate  as  base  ; 
this  has  been  largely  used  during  recent  years  and  is  five  or  six  times  as  powerful  as 
gunpowder. 

The  most  important  of  these  explosives  is  Favier  powder,  which,  in  its  different  forms, 
usually  consists  of  a  mixture  of  ammonium  nitrate  and  nitronaphthalenes  and  sometimes 
contains  also  sodium  nitrate  (see  later,  Chlorate  Powders). 


246  ORGANIC    CHEMISTRY 

SAFETY  EXPLOSIVES  (for  Mines  Rich  in  Firedamp).1  Firedamp  (see  p.  33)  is  a 
mixture  of  methane  and  air  and  is  formed  particularly  in  coal-mines.  It  burns  at  450° 
and  inflames  at  650°  ;  in  presence  of  spongy  platinum  it  burns  even  at  200°.  For  ignition 
to  occur,  a  cortain  time — at  least  some  seconds — is  necessary.  For  instance,  at  650°  about 
10  seconds  elapse  before  the  explosive  mixture  ignites,  whilst  at  1000°  ignition  occurs  in 
1  second.  This  explains  why,  for  example,  the  gases  produced  at  a  temperature  of  2000°  by 
shattering  explosives  do  not  always  fire  the  explosive  mixture,  the  explosion  occurring 
with  enormous  rapidity  (scarcely  measurable).  The  danger  of  ignition  is  diminished 
by  decrease  of  the  quantity  of  gas  formed,  i.e.  of  explosive  used  for  each  charge  ;  the  very 
hot  gase3  produced  expand  rapidly  and  become  cooled,  so  that  they  are  unable  to  cause 
ignition  of  the  firedamp.  Further,  if  the  heat  of  the  gases  is  efficiently  utilised  to  give 
the  maximum  amount  of  mechanical  work  (splitting  of  the  rock),  the  risk  of  firing  is  dimi- 
nished ;  hence  follows  the  necessity  of  a  good  tamping  for  each  charge  in  order  that  the 
escape  of  the  gases  without  performing  work  may  be  prevented. 

Explosion  in  the  open  is  more  likely  to  ignite  firedamp.  The  use  of  a  powerful  detonator 
is  advantageous,  in  order  that  the  explosion  may  be  sharp  and  rapid.  Mine  explosives 
should  contain  sufficient  oxygen  to  produce  only  C02  and  not  the  poisonous  CO. 

Instead  of  calculating  the  temperature  and  duration  of  explosion,  it  is  preferable  in 
practice  to  make  direct  experiments  with  small  cannons  placed  against  a  rock  at  the  bottom 
of  a  long,  Avide  iron  tube  or  test-chamber  (20  cu.  metres),  containing  an  explosive  gas. 
Discharge  of  the  cannons  should  not  ignite  the  gas  if  the  explosive  is  safe.  In  France  it  is 
prescribed  by  law  that  in  mines  explosives  must  be  used  which  give  gases  of  maximum 
degree  of  oxidation  but  no  inflammable  gas  (CO,  H2)  or  solid  carbide :  further,  the  calculated 
temperature  of  detonation  must  not  exceed  1500°  (or  for  certain  piercing  operations,  1900°). 

Gunpowder,  dynamite,  and  blasting  gelatine  readily  cause  explosion  of  firedamp  in 
mines,  their  temperatures  of  explosion  exceeding  2200°  (as  shown  by  Maillaid  and  Lc 
Chatelier).2  In  order  to  meet  the  requirements  of  a  safety  explosive,  various  ingenious 
processes  are  employed  to  lower  the  temperature  of  the  gases  from  the  explosion  sufficiently 
to  prevent  them  giving  a  flame.  The  charges  are  wrapped  up  and  the  tamping  made  wilh 

1  The  frequent  explosions  occurring  in  mines  have  led  scientific  men  during  the  past  thirty  years  to  make 
attempts  to  mitigate  their  effects  and  to  render  them  less  common.     Commissions  for  this  purpose  have  been  ap- 
pointed in  France  (1880),  Russia  (1887),  Austria  (1891),  and  other  countries.     In  England  the  question  has  been 
studied  by  Macnab  (1876)  and  Abel  (1886)  ;   in  France  by  Mallard  and  Le  Chatelier  (1883),  Watteyne,  &c.  ;   in 
Germany  by  Winckhaus  (1895),  very  systematically  by  C.  E.  Bichel  and  Mettegang  (1904-1907),  who  devised 
various  ingenious  forms  of  indicating  apparatus,  Beyling  (1903-1907)  and  Heise  (1898) ;  and  in  Austria  by  Siersch 
(1896),  Bohm  (1886),  Mayer  (1889),  and  Hess  (1900). 

The  studies  of  Bichel  more  especially  have  shown  that  the  safety  of  an  explosive  for  use  in  mines  (especially 
coal-mines)  depends  simultaneously  on  several  factors,  each  of  which  must  lie  within  definite  limits,  excess  of  one 
of  these  not  being  able  to  compensate  for  deficiency  of  another.  Thus,  for  example,  ordinary  Mack  poicder,  which 
lias  almost  all  the  requisites  of  a  safety  explosive,  cannot  be  employed  for  the  sole  reason  that  the  duration  of  its 
flame  is  too  long  and  so  renders  it  dangerous.  The  principal  factors  establishing  the  safety  of  an  explosive  are  : 
velocity  of  explosion,  temperature  of  the  gases  formed,  length  of  the  flame,  duration  of  the  ilame,  quantity  of 
explosive  used  in  each  explosion,  &c. 

2  Dynamite  and  especially  gunpowder,  if  exploded  without  tamping,  will  certainly  ignite  firedamp  or  even  the 
coal-dust  suspended  in  the  air  of  coal-mines.    The  danger  is  diminished  but  not  excluded  by  tamping,  so  that  even 
in  1853  the  Englishman  Elliot  suggested  replacing  the  explosives  by  quicklime,  a  large  compressed  charge  of  which 
is  placed  in  a  cavity  in  the  rock  ;   the  pipe  from  a  pressure  water-pump  is  then  introduced  and  a  good  tamping 
effected.     The  water,  coming  into  contact  with  the  lime,  increases  the  volume  of  the  latter  2  to  5  times,  and, 
with  the  steam  formed  at  the  same  time,  pressures  of  500  atmos.  can  be  obtained.     In   1880  the  use  of  lime 
cartridges  was  fairly  general  in  mines,  but  they  were  abandoned  later  owing  to  the  unsatisfactory  results  given. 
No  better  fortune  befell  cartridges  of  quicklime,  water,  and  sulphuric  acid,  or  powdered  aluminium  and  sulphuric 
acid  (which  develop  hydrogen),  or  chlorine  and  ammonia  compressed  separately  and  then  united,  or  compressed 
explosive  mixtures  of  oxygen  and  hydrogen.     In  1876,  the  Englishman  Macnab  suggested  tamping  gunpowder 
charges  with  water,  but  this  did  not  always  prevent  explosion  of    the  firedamp ;    the  same  system  applied  to 
dynamite  by  Abel  in  1886  gave  better  results.     In  some  cases,  the  water  is  replaced  by  moist  substances  (sand, 
moss,  <tc.),  which  yield  good  results. 

In  mines  which  give  much  coal-dust  there  is  the  greatest  danger  of  disaster  when  large  charges  (of  more  than 
100  to  150  grms.)  are  used,  and  when  the  coal  contains  22  to  35  per  cent,  of  volatile  products. 

Although  firedamp  ignites  at  650°,  explosives  can  be  used  which  have  a  temperature  of  explosion  only  slightly 
below  2200°  (roburite,  1616°  ;  trestphalite,  1806°  ;  carbonites  for  coal-mines,  1820°  to  1870°,  <tc.),  since  the  gases 
cool  on  expanding.  But  even  these  explosives  are  dangerous  if  the  charges  are  large  (above  300  grms.  for  roburite 
and  westphalite,  and  above  1000  grms.  for  the  carbonites),  since  then  a  momentary  pressure  on  the  air  is  developed 
(especially  if  the  velocity  of  explosion  is  high)  and  a  decided  rise  of  temperature.  Explosives  which,  in  charges  of 
600  to  800  grms  ,  do  not  ignite  the  explosive  mixture  in  the  test-chamber,  may  be  safely  used  in  mines  containing 
firedamp. 

Ordinary  black  powder  is.  as  stated  above,  very  dangerous  in  such  mines.  More  dangerous  still  arc  those 
explosives  which  cause  considerable  dilatation  of  the  leaden  blocks  (see  later,  Fig.  226,  p.  262),  and  those  which 
give,  among  their  products  of  explosion,  carbon  monoxide  and  hydrogen  but  not  oxygen,  since  these  gases  on 
burning  (rapidly)  withdraw  oxygen  from  the  flame  of  the  explosive  and  almost  stifle  it.  A  good  safety  explosive 
ceases  to  be  such  if  it  is  not  always  prepared  with  the  same  care  and  of  equal  uniformity  from  the  same  materials. 


SAFETY    EXPLOSIVES 


247 


water  or  with  gelatine  containing  98  per  cent,  of  water  (or  with  special  sponges  saturated 
with  water,  &c.).  Salts  containing  much  water  of  crystallisation  have  also  been  used 
for  tamping,  but  without  good  results,  the  tamping  being  simply  projected  to  a  distance 
without  evaporation  of  the  water.  A  safer  plan  consists  in  mixing  the  explosive  directly 
with  such  salts,  the  water  of  crystallisation  then  evaporating  with  considerable  absorption 


FIG.  203. 

100  grnis.  of  Gelatine  Dynamite 


FIG.  204. 
100  grms.  of  Dynamite  (Kieselguhr) 


of  heat,  at  the  instant  of  explosion.  Finally,  use  is  made  of  explosives  with  ammon.'um 
nitrate  as  base,  the  temperature  of  explosion  of  the  nitrate  being  only  1130°  and  the  reaction 
occurring  thus  :  NH4N03  =  N2  +  2H2O  +  O.  Since,  however,  the  explosive  effect  of 
ammonium  nitrate  is  small,  it  is  combined  with  other  substances,  e.g.  with  dynamite  or 
with  Favier's  explosive  (ammonite).  In  some  cases,  in  addition  to  the  nitrate,  ammonium 
chloride  is  used,  this  undergoing  dissociation  with  absorption  of  heat  from  the  gases. 


FIG.  205. 
100  grms.  Roburite 


FIG.  206. 
100  grms.  Carbonite 


FIG.   207. 
100  grms.  Grisounitc 


Various  kinds  of  such  explosives  give  good  results,  e.g.  grisounite,  containing  44  per  cent, 
nitroglycerine,  12  per  cent,  nitrocellulose,  and  44  per  cent,  crystallised  magnesium  sulphate 
(MgSO4  +  7H2O)  ;  also  roburite,  with  82  per  cent,  of  ammonium  nitrate,  and  18  per  cent, 
of  dinitro  benzene  ;  Nobel's  wetter-dynamite,  with  53  per  cent,  nitroglycerine,  14-3  per  cent, 
kieselguhr,  and  32-7  per  cent,  magnesium  sulphate  ;  securite,  with  37  per  cent,  ammonium 
nitrate,  34  per  cent,  potassium  nitrate,  and  29  per  cent,  nitrobenzene  ;  westphalite,  con- 
taining 94  per  cent,  ammonium  nitrate,  and  6  per  cent,  resin  ;  carbonitc,  with  25  per  cent. 


248  ORGANIC    CHEMISTRY 

nitroglycerine,  40  per  cent,  wood-meal,  30-5  per  cent,  potassium  nitrate,  4  per  cent,  barium 
nitrate,  and  0-5  per  cent,  sodium  carbonate  ;  vigorite,  containing  30  per  cent,  nitroglycerine, 
49  per  cent,  potassium  chlorate,  7  per  cent,  potassium  nitrate,  9  per  cent,  wood-pulp,  and 
5  per  cent,  magnesium  carbonate.  But  even  these  substances 
are  not  safe  in  the  absolute  sense  of  the  word ;  with  such  addi- 
tions of  inert  products,  the  explosives  lose  in  force  but  gain  in 
safety. 

In  1896  Siersch,  starting  from  the  hypothesis  that  the  smaller 
the  flame  produced  in  an  explosion,  the  safer  will  be  the  explo- 
sive, photographed,  on  dark  nights,  the  flames  produced  by  the 
free  explosion  of  100-grm.  cartridges.  As  will  be  seen  from 
Figs.  203  to  208,  these  flames  are  of  value  although  they  are  not 
absolutely  decisive,  since  the  non -luminous  (ultra-violet)  rays  also 
act  on  the  photographic  plate.  In  Fig.  203  is  seen  a  small 
F  208  luminous  spot  detached  from  the  principal  flame,  this  being  due 

either   to   the   surrounding  gas   being    rendered    incandescent    by 

100  grms.  Gelatine  Dy-      th     ghock    of    the  expiosion,  or  to  subsequent  inflaming   of  the 
namite,   with   tamping  . 

of  wet  paper  gases  of  the  explosion. 

BLACK  POWDER   (GUNPOWDER) 

This  explosive,  which  was  the  first  to  be  employed  in  firearms,  and  was  the  only  one 
available  for  military  and  industrial  purposes  until  after  the  middle  of  the  nineteenth 
century,1  has  latterly  become  relatively  unimportant  owing  to  the  discovery  of  dynamite 
and  smokeless  powders. 

Ordinary  black  powder  is  a  mixture  of  potassium  nitrate,  sulphur,  and  carbon  in  propor- 
tions according  to  the  purpose  for  which  it  is  required.2 

For  black  military  powders,  used  in  guns  and  cannon  in  Italy,  France,  England, 
Russia,  China,  and  the  United  States,  the  maximum  power  is  obtained  without  an  excessive 
rapidity  of  explosion  (so  as  not  to  injure  the  gun  too  much)  with  75  per  cent,  of  potassium 
nitrate,  15  per  cent,  of  carbon,  and  10  per  cent,  of  sulphur  ;  in  Germany  the  proportions 
used  are  74,  16,  and  10  respectively.  Until  a  few  years  ago  erroneous  proportions  were 
still  employed,  namely,  61-5,  23,  and  15-5. 

The  chemical  reactions  occurring  during  the  explosion  of  black  powder  vary  according 
as  the  explosion  takes  place  under  pressure  or  at  the  ordinary  pressure  (deflagration). 
In  the  first  case,  Abel  and  Nobel  obtained,  from  1  grm.  of  ordinary  powder,  0-585  grm. 
of  solid  products,  and  0-415  grm.  of  gas  (258  c.c.),  according  to  the  following  equation  : 
16KN03  +  21C  +  7S  =  13CO2  +  3CO  +  5K2CO3  +  K2SO4  +  2K2S3  +  16N;  in  addition 
there  are  formed  traces  of  potassium  thiocyanate  and  thiosulphate,  and  ammonium 
carbonate,  whilst  traces  of  sulphur  and  nitre  remain  unchanged,  as  the  proportions  taking 

1  It  is  stated,  but  without  any  real  confirmation,  that  the  Chinese  knew  of  gunpowder  as  early  as  the  first 
century  B.C.,  and  that  they  used  it  for  throwing  projectiles  ;  more  certain  is  it  that  they  employed  mixtures  of 
sulphur,  nitre,  and  carbon  to  make  rockets. 

Also  the  ancient  Indians  used  powders  for  the  preparation  of  a  kind  of  aitiflcial  fire.  Greek  fire,  used  in  Greece 
in  the  seventh  century,  was  obtained  with  explosive  powder  and  probably  originated  in  China.  The  Arabs  were 
acquainted  with  inflammable  mixtures  from  very  remote  times,  whilst  true  gunpowder,  containing  sulphur,  carbon, 
and  nitre,  was  prepared  by  them  only  in  the  thirteenth  century,  probably  after  they  had  learnt  the  manufacture 
from  the  Chinese.  They,  however,  studied  its  propulsive  properties  and  constructed  the  first  primitive  guns. 

In  Germany  it  is  stated  that  it  was  the  monk  Berthold  Schwarz  (a  native  of  Freiburg,  where  a  monument  is 
now  erected  to  him)  who  recognised  the  power  of  gunpowder  in  about  1320  and  used  it  for  the  first  time  in  Europe 
in  firearms  ;  so  that  the  discovery,, not  of  the  powder,  but  of  guns  for  throwing  projectiles,  is  due  to  Schwarz. 
After  the  middle  of  the  fourteenth  century,  gunpowder  came  into  use  first  in  Germany,  then  in  Sweden,  Russia, 
and  elsewhere  for  guns  and  cannons.  Macchiavelli  records  that  by  1386  the  Genoese  and  Venetians  had  learnt 
from  the  Germans  the  use  of  powder  with  guns.  According  to  Libri,  cannons  were  made  at  Florence  as  early 
as  1326.  The  projectiles  were  made  first  of  stone,  then  of  stone  covered  with  iron ;  leaden  shot  began  to  be  used 
in  1347,  and  in  1388  Ulrich  Beham  cast  the  first  iron  shot,  which  became  general  in  the  fifteenth  century.  The 
mixing  of  the  ingredients  to  make  the  powder  was  first  carried  out  by  hand,  and  it  was  only  in  1525,  in 
France,  that  powders  were  graded  and  granulated,  the  mixing  being  effected  in  vertical  mills  like  those  used  for 
expressing  oil  from  olives. 

1  After  a  series  of  experiments  in  Brussels  in  1560,  the  best  proportions  for  the  ingredients  were  found  to  be  : 
nitre,  75  per  cent. ;  carbon,  15-62  per  cent. ;  and  sulphur,  9-38  per  cent.  A  thirteenth-century  manuscript  states 
that  the  Arabs  used  74  per  cent,  nitre,  15  per  cent,  carbon,  and  11  per  cent,  sulphur.  A  black  powder  dating 
from  1627  and  discovered  in  1905  during  excavation,  contained  40  per  cent,  nitre,  24  per  cent,  sulphur,  and  37 
per  cent,  carbon.  In  1800  Berthollet  recommended  as  the  most  effective  proportions  :  80  per  cent,  of  nitre,  15 
per  cent,  of  carbon  and  5  per  cent,  of  sulphur.  Berthelot  has  recently  calculated  the  theoretically  best  proportions 
to  give  a  maximum  development  of  heat,  his  results  being  :  84  per  cent,  nitre  +  8  per  cent,  sulphur  +  8  per  cent, 
carbon  ;  this  calculation  assumes  that  the  reagents  are  chemically  pure,  which  in  practice  is  not  the  case. 


MANUFACTURE    OF    GUNPOWDER          249 

part  in  the  above  reaction  are  77-7  nitre,  10-54  sulphur,  and  11-86  carbon.  With  1  grm. 
of  powder  exploded  at  the  ordinary  pressure,  they  obtained  0-769  grm.  of  the  same  solid 
products,  and  0-321  grm.  of  gaseous  products  (about  193  c.c.),  thus  : 

16KN03  +  130  +  6S  =  11CO2  +  2K2C03  +  5K2SO4  +  K2S  +  16N  ; 

traces  of  other  products  are  also  formed,  since  this  equation  represents  82-4  per  cent, 
nitre,  9-5  sulphur,  and  8  carbon. 

Sporting  powder  should  burn  more  rapidly,  and  hence  contains  more  nitre  and  a  brown 
wood-charcoal  of  inferior  quality.  In  different  countries  the  nitre  varies  from  75  to  78 
per  cent.,  the  carbon  from  12  to  15  per  cent.,  and  the  sulphur  from  9  to  12  per  cent.  Nowa- 
days, however,  most  sporting  powders  are  of  the  smokeless  type  with  a  nitrocellulose  base. 
With  mining  powders  the  production  of  a  large  quantity  of  gas  is  required,  so  that  the 
amounts  of  sulphur  (13  to  18  per  cent.)  and  of  carbon  (14  to  21  per  cent.)  are  increased  ; 
if,  however,  the  proportion  of  nitre  is  made  too  small,  the  explosion  becomes  very  slow, 
more  CO  is  produced,  and  the  gases  are  partly  able  to  escape  through  the  fissures  first 
produced  towards  the  end  of  the  explosion,  the  useful  effect  being  thus  diminished.  Hard 
rocks  require  increased  rapidity  of  explosion,  but  with  tufa  or  granite  (to  obtain  large 
blocks)  greater  slowness  of  explosion  is  necessary. 

MANUFACTURE  OF  POWDER.  The  prime  materials  should  be  prepared  with 
great  care.  The  sulphur  should  contain  no  trace  of  sulphuric  acid,  so  that  stick  sulphur 
and  not  flowers  of  sulphur  is  used  ;  if  necessary,  it  is  purified  by  distillation,  and  should 
yield  less  than  0-25  per  cent,  of  residue  on  combustion.  At  the  present  time,  use  is  also 
made  of  the  sulphur  recovered  from  soda  residues  (see  vol.  i,  pp.  199  and  473).  The 
potassium  nitrate  cannot  be  replaced  by  sodium  nitrate,  the  latter  being  more  hygroscopic 
and  impure.  The  nitre  should  contain  less  than  1  part  of  chlorides  per  3000,  and  should 
be  free  from  perchlorates.1  Both  English  nitre  from  India  and  German  conversion  nitre 
are  used,  after  suitable  purification. 

The  wood  charcoal  should  be  highly  porous  and  should  burn  easily  without  leaving  an 
appreciable  quantity  of  ash  ; 2  in  different  countries,  different  kinds  of  wood  are  used : 

1  For  many  years  the  superiority  of  English  powders  could  not  be  explained,  and  it  was  attributed  to  the 
use  of  Indian  nitre,  refined  in  England,  whilst  all  over  Europe,  conversion  nitre,  prepared  in  Germany,  was  em- 
ployed. On  the  other  hand,  the  Germans  showed  that  their  nitre  was  very  pure  as  it  contained  only  0-5  per  cent, 
of  chlorides,  and  they  regarded  the  preference  for  English  powder  as  the  result  of  prejudice.  But  in  1894  the 
elder  Hellich  showed  that  the  conversion  nitre  contained  also  perchlorate,  which  was  not  shown  in  the  estimation 
of  the  chlorides.  Spontaneous  explosions  of  powder  in  Servia  in  1896  were  ascribed  by  Paraotovic  to  the  use  of 
nitre  containing  perchlorates.  In  1897,  Eelbetz  showed  that  the  perchlorate  is  not  distributed  homogeneously 
through  the  crystals  of  nitre,  but  that  some  of  the  latter  contain  more  (and  are  more  explosive)  and  others  less  ; 
hence  the  superiority  and  uniformity  of  powders  free  from  perchlorate  were  explained.  The  perchlorate  in  nitre  is 
estimated  by  Selckmann's  method  (1898)  by  fusing  5  grms.  of  the  nitre  with  20  grms.  of  pure  lead  in  scales  ;  the 
fusion  is  first  gentle  for  15  minutes  until  the  mass  becomes  pasty,  after  which  the  temperature  is  raised  for  a  short 
time.  The  mixture  of  potassium  nitrite,  lead  oxide,  and  chlorides  is  poured  into  water  and  the  chlorides  estimated, 
the  excess  over  the  amount  originally  present  being  due  to  the  chlorates. 

1  Under  similar  conditions,  the  readiness  with  which  powder  burns  is  increased  by  increased  combustibility  of 
the  charcoal.  Hence  it  is  necessary  not  only  to  use  a  suitable  method  of  preparing  the  charcoal,  but  also  to  make 
careful  choice  of  the  wood  to  be  carbonised.  Light,  soft  wood  is  preferred,  and  of  the  different  parts  of  the  plant 
the  best  are  branches  at  least  three  years  old  (5  to  8  cm.  in  diameter) ;  the  bark  is  rejected.  For  powders  to  be 
used  in  guns,  hazel  or  breaking  buckthorn  (Rhamnus  frangula)  or  hemp  stalks  are  used,  whilst  for  cannon  and 
mining  powders,  preference  is  given  to  white  willow  (Salix  alba),  alder,  poplar,  &c.  Hemp-stalk  charcoal  burns 
the  best,  and  about  40  parts  of  it  are  obtained  from  100  of  the  stalks  ;  hazel-wood  gives  only  33  per  cent,  of 
charcoal.  The  wood,  freed  from  bark  and  well  dried  in  the  air  for  2  or  3  years,  still  contains  about  20  per  cent, 
of  moisture.  When  heated  out  of  contact  with  the  air,  it  evolves  combustible  gases,  but  the  greater  part  of  the 
wood  blackens  without  burning  and  forms  charcoal.  It  is  of  importance  to  determine  the  best  conditions  for 
carbonisation.  When  the  temperature  is  not  very  high  (280°  to  340°),  a  light,  reddish,  readily  combustible 
charcoal  is  obtained,  whilst  at  higher  temperatures  a  black,  denser  charcoal  is  obtained  which  burns  slowly  and 
badly,  although  it  is  a  better  conductor  of  heat  and  electricity. 

Rapid  carbonisation  gives  a  diminished  yield,  but  the  charcoal  is  lighter  and  more  friable.  The  charcoal  is 
ground  just  before  using,  as  in  the  powdered  state  it  is  much  more  hygroscopic  and  may  also  inflame  spontaneously. 

Charcoal  prepa»cd  at  270°  is  partially  soluble  in  caustic  soda  solution,  whilst  it  is  insoluble  if  prepared  at 
above  330°. 

Carbonisation  of  wood  in  heaps  or  pits  is  no  longer  employed,  since  the  resulting  charcoal  is  impure  and  non- 
uniform,  owing  to  the  impossibility  of  regulating  the  temperature.  So  that  at  the  present  time  powder  factories 
always  resort  to  charring  by  distillation,  or  charring  in  fixed  or  movable  cylinders,  as  proposed  by  the  English  bishop, 
Landloff,  at  the  end  of  the  eighteenth  century.  The  distillation  may  be  carried  out  in  fixed  horizontal  cylinders 
(two  to  each  furnace),  1-5  metre  long  and  0-65  metre  in  diameter ;  but  with  this  arrangement  discharging  is 
difficult  and  sometimes  the  heated  charcoal  ignite?.  It  is  better  to  used  fixed  vertical  cylinders  with  openings  at 
the  bottom  for  emptying,  or  movable  vertical  cylinders,  which  can  be  rotated  from  time  to  time  during  the 
heating.  In  every  cylinder,  a  space  is  left  for  the  introduction  of  a  pyrometer  to  indicate  the  temperature  of  the 
wood.  The  furnace  is  first  heated  gently,  and  after  three  hours  yellowish  fumes,  composed  of  water,  acetic  acid, 
methyl  alcohol,  &c.,  begin  to  distil.  After  this,  the  distillation  continues  without  further  heating  of  the  cylinder. 
The  gases  are  led  by  pipes  under  the  hearth,  where  they  burn  at  first  with  a  bright  red  flame  and  towards  the 


250 


ORGANIC    CHEMISTRY 


in  Spain,  flax  and  vine  stalks  ;  in  Germany,  breaking  buckthorn,  the  alder,  and  the  willow  ; 
in  France,  the  poplar,  lime,  &c.  ;  and  in  Italy,  hemp  stalks,  &c.  In  some  cases,  charcoal 
from  sugar,  dextrin,  maize,  cork,  &c.,  is  used.  Charcoal  obtained  at  temperatures  exceed- 
ing 430°  is  of  no  use  for  gunpowder. 

PULVERISATION  AND  MIXING  OF  THE  INGREDIENTS.  In  early  times  the 
ingredients  were  ground  and  mixed  by  hand  in  mortars,  but  machine  mills  were  used  as 
early  as  1350.  In  the  seventeenth  century,  the  use  of  wooden  stamps  became  widespread, 
but  these  were  the  cause  of  many  explosions,  so  that  the  vertical  mills  again  came  into 
use,  the  powder  being  kept  moistened  with  water  during  grinding.  At  the  present  time 
the  ingredients  are  powdered  separately,  then  partial  mixtures  of  sulphur  and  charcorvl, 
and  charcoal  and  nitre,  are  made,  these  being  finally  united  and  intimately  mixed.  The 
finer  the  materials  are  powdered  the  better  will  be  the  resulting  powder. 

The  charcoal  and  the  sulphur  may  be 
powdered  in  the  Excelsior  mill  (see  p.  168, 
Fig.  162),  the  product  then  being  sieved 
and  the  coarse  particles  reground.  The  nitre 
is  received  from  the  refiner  in  the  form  of 
flour  and  only  requires  sieving. 

The  binary  mixtures  are  prepared  by  placing 
the  powdered  substances  in  special  iron  drums 
(Fig.  209),  1-1  to  1-2  metre  in  diameter,  and 
0-6  to  1-2  metre  long.  On  the  inner  periphery 
of  the  drum  are  12  to  16  transverse  ribs,  3  to 
4  cm.  thick.  Hard  phosphor-bronze  balls,  15 
to  20  mm.  in  diameter,  are  introduced  with 
the  two  substances  through  the  aperture  a, 
which  corresponds  with  the  hinged  cover  b, 
fixed  on  the  cylindrical  wooden  casing  sur- 
rounding the  drum.  This  wooden  casing  is 
connected  with  a  leather  or  cloth  bag,  c,  by 
Avhich  the  mixture  is  finally  discharged  into 
the  barrels,  d,  these  being  closed  hermetically 
so  as  to  prevent  contact  with  the  air,  which 
might  cause  ignition  (see  vol.  i,  Pyrophoric 
Substances).  . 

The  drum  is  rotated  about  15  to  20  times  per  minute  for  8  to  10  hours,  100  to  150 
kilos  of  the  bronze  balls  being  used  per  200  kilos  of  the  mixed  substances  ;  the  balls  are 
given  a  bumping  motion  by  the  peripheral  ribs  and  so  increase  the  fineness  of  the  powder. 
When  the  aperture,  a,  furnished  with  a  coarse  net,  is  opened  at  the  end,  the  powder  is 
discharged  and  the  balls  retained  for  a  subsequent  operation  (see  also  the  figures  of  ball 
mills,  vol.  i,  p.  512). 

The  ternary  mixture  is  prepared  by  mixing  either  binary  mixture  with  the  third  con- 
stituent or  the  two  binary  mixtures  (carbon  +  sulphur,  and  carbon  +  nitre)  in  the  required 
proportions  in  a  rotating  cylinder  provided  with  stirrers,  or,  better,  in  a  drum  similar  to 
that  just  described.  After  this  the  mass  is  moistened  with  water  and  mixed,  and  then 
introduced  into  a  stamp  mill  (like  that  shown  in  vol.  i,  p.  514),  where  it  is  kept 
moistened  (with  about  10  per  cent,  of  moisture)  without  caking.  The  stamps  make  30  to 
60  blows  per  minute,  and  their  action  is  continued  for  at  least  12  hours  for  cannon  powder, 
8  hours  for  mining  powder,  and  24  hours  for  sporting  powder.  The  cakes  thus  obtained 
then  pass  to  the  granulating  machine. 

In  many  factories,  however,  the  use  of  stamps  has  been  abandoned,  these  being  replaced 

end  of  the  distillation  with  a  bluish  red  flame.  When  the  distillation  is  finished,  the  cover  of  the  cylinder  is  raised 
and  the  charcoal  discharged  into  suitable  movable  cylinders,  which  are  immediately  closed  to  exclude  the  air. 
Into  the  cylinder,  while  still  hot,  another  charge  of  wood  is  at  once  introduced.  Each  charring  lasts  at  least  10 
hours.  In  three  or  four  days  the  charcoal  is  cold  and  is  then  removed  liwiip  by  lump  from  the  cooling  cylinders, 
any  that  is  insufficiently  burnt  being  rejected.  The  colour  of  the  charcoal  is  coffee-black,  the  fracture  beins? 
velvety  and  of  the  same  colour. 

An  improved  process  of  distilling  wood  by  means  of  superheated  steam,  proposed  by  Violette  in  1847  and 
perfected  by  Gossart  in  1855,  was  abandoned  on  account  of  its  excessive  cost. 

In  1899,  H.  GUttler  in  Germany  suggested  the  replacement  of  the  superheated  steam  by  hot  carbon  dioxide 
in  order  to  obtain  a  rapid  charring  ;  after  the  operation,  the  mass  can  be  quickly  cooled  by  a  current  of  cold  carbon 
dioxide. 


FIG.  209. 


MIXING    OF    GUNPOWDER 


251 


by  vertical  iron  runners  (Fig.  210)  about  1-6  metre  in  diameter  and  40  cm.  thick,  and 

weighing  about  5000  kilos  each.     They  rotate  on  a  very  hard  iron  plate  2  metres  in  diameter. 

The  two  runners  are  placed  at  different  distances  from  the  central  shaft,  which  is  actuated 

by  bevel  wheels  above  (as  in  the  figure)  or  below  ; 

suitable  scrapers  detach  the  powder  sticking  to  the 

runners,  and  others  bring  the  powder  from  the  edge  to 

the  centre  and  so  under  the  runners.    This  incorpora- 
tion is  continued  for  3  hours  in  the  case  of  military 

powder  and  for  5  hours  with  sporting  powder,  the 

velocity  of  the  runners  being  10  to  12  revolutions 

per  minute  at  first  and  only  1   revolution  in   20 

minutes  towards  the  end  of  the  operation,  ?o  that 

highly' compressed  cakes  may  be  obtained.     About 

every  hour  the  mass  is  moistened  with  1  to    1-5 

litre  of  distilled  water  for  a  charge  of  20  kilos,  the 

amount  of  water  used  depending  on  the  hygro- 
metric  state  and  tem- 
perature of  the  air.  The 
water  dissolves  the  nitre, 
which  is  thus  distributed 
uniformly  and  in  a  finely 
divided  state  through- 
out the  whole  mass. 

In  some  factories, 
compression  of  the  mois- 
tened ternary  mixtuie 
is  effected  by  means  of 

hydraulic  presses  (Fig.  211)  between  a  number  of  separate 
layers  of  copper  or  ebonite,  a  pressure  of  100  atmos.  being 
applied  for  three-quarters  of  an  hour.  This  procedure  yields 
very  compact  cakes,  having  the  density  1-7  to  1-8. 

It  was   formerly  the   custom   in   France,  and   is   still   in 
Germany,  to   use   roller-presses  (laminoirs)  (Fig.  212)  formed 
of  three  superposed  rolls  ;   the  lowest  one,  C,  of  cast-iron,  is 
driven  directly  and   transmits  the  movement  to  the    middle 
one,  B,  which  is  coated  with  paper  ;    this   then   drives   the 
uppermost  one,  A,  of  chilled  cast-iron.     The  endless  band,  D. 
collects  the  mixture  falling  from  the  hopper,  E,  and  carries  it 
between  B  and  A,  between  which  a  pressure  of  15  to  25  tons 
by  means   of 
A  knife 


FIG.  210. 


FIG.  211. 


can   easily  be  obtained 
the  lever,  L,  and  weights,  P. 
is  arranged  so  as  to  scrape   the    com- 
pressed powder  from  the  band. 

As  a  rule,  moist  compression  gives 
a  more  uniform  and  also  a  deneer 
mass. 

After  compression  the  cakes  still 
contain  5  to  8  per  cent,  of  moisture, 
and  they  are  allowed  to  stand  for  7  to 
8  days  in  well -ventilated  magazine?. 
After  this,  those  from  the  hydraulic 
presses  or  roller-presses  are  first  dried 
(see  later)  and  then  granulated,  whilst 
those  from  the  stamps  or  incorporating  mills,  being  less  moist,  are  granulated  directly. 

GRANULATION.  This  operation  serves  the  purpose  of  preventing  the  separation  of 
the  constituents,  and  of  rendering  the  powder  less  hygroscopic  and  less  compact  (but  not 
less  dense),  since  the  combustion  of  the  granules  is  more  rapid  than  that  of  the  fine 
compact  powder  ;  also,  the  finer  the  granulation  the  more  rapid  is  the  combustion  and 
the  greater  the  mechanical  effect.  The  finest  grains  are  used  for  sporting  powders,,,  then 


FIG.  212. 


252 


ORGANIC    CHEMISTRY 


FIG.  213. 


come  those  for  military  rifles,  the  coarsest  grains  being  for  cannon.  If  sporting  powder 
were  used  for  military  rifles,  the  barrel  would  wear  out  rapidly  and  might  even  split. 

It  was  only  after  1445  that  powder  for  artillery  was  granulated,  it  being  found  that  the 
effect  was  greater  than  that  of  the  non -granulated  and  non-compressed  powder.  Com- 
pression with  stamps  or  rolls  came  into  general  use  in  France  after  1525,  the  compressed 
mass  being  then  broken  up  with  wooden  hammers  and  granulated  ;  for  this  purpose,  the 
mass  was  spread  out  on  a  large  sieve  and  covered  with  a  heavy  disc  of  wood,  the  sieve  being 
then  rotated  and  oscillated  until  all  the  powder  passed  through  it  in  grains. 

Later  the  Lefevre  graining  machine 

d    JL-          -2-  was  devised,  and  this  is  still  in  use  in 

France  and  Germany  ;  this  machine 
grades  the  grains  into  different  sizes 
and  also  eliminates  all  dust,  powders 
showing  more  regular  and  rapid  com- 
bustion being  thus  obtained. 

This  machine  (Figs.' 213  and  214) 
consists  of  an  octagonal  board  with 
sides,  a,  having  a  diameter  of  2-5 
metres  and  suspended  from  the  ceiling 
by  8  ropes,  b.  This  receives  a  circular 
motion  by  means  of  an  eccentric 
formed  of  a  vertical  shaft,  c,  with  an 
elbow-joint.  This  shaft  is  rotated  at 
the  rate  of  75  revolutions  per  minute 
by  the  cog-wheels,  B.  On  the  board 
are  fixed  8  or  10  triple  sieves,  8,  to 
which  the  powder  to  be  granulated  is  supplied  by  leather  or  cloth  tubes,  e.  The  powder 
falls  on  to  the  first  wooden  sieve,  A  (Fig.  214),  with  a  mesh  of  3  to  4  mm.,  the  coarse  lumps 
being  gradually  broken  by  a  disc  of  wood,  c,  weighing  700  grins.  The  grains  then  pass 
on  to  a  second  sieve,  B,  of  metal,  3  to  4  cm.  below,  and  then  to  the  lowest  one,  C,  which 
is  of  hair  and  retains  the  grains  of  the  required  size,  whilst  the  dust  falls  into  D  and  thence 
through  the  leather  pipe,  g,  into  the  barrel,  p  ;  the  uniformly  grained  powder  is  discharged 
into  q  through  /. 

More  common  at  the  present  time  is  the  granulating  machine  with  fluted  rolls,  first 
suggested  in  1819  by  the  Englishman,  Colonel  Congreve,  and  subsequently  improved  in 
various  ways.  This  machine  (Fig.  215)  consists  of  several  pairs  of  bronze  rolls,  A,  B,  C, 
fluted  longitudinally  and  transversely.  The  lumps 
of  powder  from  the  breaker,  F,  are  raised  to  E  by  an 
endless  band,  and  fall  on  to  the  first  rolls,  A,  furnished 
with  small  pyramidal  teeth  projecting  10  mm.,  then  on 
to  the  second  rolls,  B,  with  finer  teeth  (3  mm.),  and 
finally  on  to  the  smooth  rolls,  C,  which  give  the 
powder  the  appearance  of  shining  scales.  The  dis- 
tance between  the  rolls  is  adjustable,  and  the  teeth 
are  kept  clean  by  means  of  a  brush.  The  granulated 
powder  falls  on  to  a  series  of  superposed  sieves,  S, 
which  are  oscillated  at  the  rate  of  150  vibrations  per 

minute,  and  so  grade  the  powder,  the  final  dust  being  discharged  at  m.  Blasting  powder, 
which  has  the  size  of  peas,  is  not  passed  through  the  smooth  rolls.  By  varying  the  mesh 
of  the  sieves,  grains  of  any  desired  magnitude  are  obtainable.  Congreve's  granulating 
machine  gives  a  yield  four  or  five  times  as  great  as  that  of  Lefevre  (for  the  same  con- 
sumption of  power)  and  also  forms  less  dust. 

DRYING.  The  granulated  powder  is  sometimes  dried  by  spreading  it  out  in  layers 
5  cm.  deep  on  cement  floors  exposed  to  the  air  and  sunvand  mixing  it  occasionally  with 
rakes  ;  this  drying  is  continued  until  the  moisture  is  reduced  to  3  per  cent. 

Artificial  drying,  which  is  independent  of  climatic  conditions,  is,  however,  more  com- 
monly used.  In  early  times  the  powder  was  placed  in  copper  pans  heated  directly  over 
the  fire,  but  this  led  to  many  explosions  ;  later  it  was  spread  out  on  cloths  in  a  chamber 
heated  by  a  stove  in  the  centre,  but  this  also  was  dangerous  even  when  the  stove  was 


FIG.  214. 


GLAZING    OF    GUNPOWDER 


253 


FIG.  215. 


outside  the  chamber.  Nowadays  drying  is  generally  effected  by  air  (used  for  the  first 
time  in  England  in  1780)  which  is  heated  by  a  network  of  steam -pipes  and  is  injected  into 
a  drying-room  containing  the  powder  spread  on  cloth  in  layers  5  to  15  cm.  deep,  mixing 
with  wooden  rakes  being  resorted  to  about  every  two  hours.  The  air  passes  through 
the  powder  and  is  carried  off  by  flues  ;  the  drying  takes  8  to  10  hours.  The  fire  of  the 

steam-boiler  is  at  least  100  metres 
from  the  drying-room. 

Dry  powder  can  be  powdered 
between  the  fingers,  giving  a  pale, 
grey  powder,  but  if  not  dry  it  is 
dark  and  sticks  to  the  hands.  In 
some  factories  the  air  used  is  pre- 
viously dried  (and  is  employed 
cold  if  the  nitre  present  tends  to 
effloresce,  but  hot  in  other  cases) 
by  being  forced  with  a  fan,  A, 
(Fig.  216),  through  fused,  spongy 
calcium  chloride  or  concentrated 
sulphuric  acid  contained  in  a 
leaden  vessel,  D.  Thence  it  passes 
into  the  chest,  E,  filled  with  lumps  of  quicklime,  which  holds  back  any  acid  carried  over. 
It  is  then  heated  in  the  brickwork  chamber,  B,  by  a  number  of  pipes,  c,  supplied  with 
steam  at  d  ;  the  warm,  dry  air  then  proceeds  through  the  tube,  V,  to  the  drying-rooms. 

The  proposal  has  also  been  made  to  dry  powder  by  heating  it  in  a  vacuum,  but  such  a 
process  is  too  costly  and  its  efficiency  low.  Drying  need  not  be  complete,  since  the  powder 
has  still  to  be  glazed. 

GLAZING.  The  dried  grains  are  rough,  angular,  and  highly  porous.  In  order  to  give 
a  brighter  appearance  to  the  powder  and  to  render  it  more  uniform  and  dense  and  less  hygro- 
scopic, it  is  treated  in  wooden  glazing  drums  (Champy  drums,  similar  to  those  used  for 
the  binary  mixtures  ;  see  above)  after  having  been  passed  through  a  fine  sieve  to  free  it 
from  adherent  dust.  The  inner  walls  of  the  drum  are  first  moistened  and  the  drum  slowly 
rotated  while  the  powder  is  being  introduced  until  about  300  kilos  are  present,  the  velocity 
being  then  raised  to  12  to  14  revolutions  per  minute  ;  the  finer  the  granulation  the  more 
rapid  must  be  the  rotation.  In  this  way  the  powder  becomes  heated  to  about  50°  and 
assumes  a  gloss  ;  care  must,  however,  be  taken  that  it  does  not  become  too  hot,  and  towards 
the  end  of  the  glazing  the  rotation  must  be  slackened.  A  little  graphite  is  sometimes 
added  (0-25  per  cent.)  to  render  the  powder  less  hygroscopic  and  more  glossy.  Glazing 
takes  4  to  5  hours 
for  blasting  powders 
and  15  to  20  hours 
for  sporting  powder. 
Glazing  is  due  to 
the  rubbing  of  the 
grains  one  against 
the  other.  The  pow- 
der is  subsequently 
dried  completely  in 
the  usual  drying - 
rooms,  or  the  panels 
of  the  drum  may  be  opened  so  as  to  allow  of  the  escape  of  the  warm,  moist  air. 

Polishing  and  sorting  are  carried  out,  after  the  glazing  and  drying,  to  remove  the  last 
traces  of  dust  and  separate  the  different  sizes  of  grains.  For  these  purposes  a  battery 
of  sieves  similar  to  those  of  the  Lefevre  and  Congreve  graining  machines  is  used,  the 
sieving  being  repeated  several  times.  The  dust  contains  about  75  per  cent,  of  carbon. 

PRISMATIC  POWDER  FOR  CANNON.  It  was  shown  by  San  Roberto  as  early  as 
1852  that  cannon  give  better  results  if  charged  with  compressed  cartridges  of  regular  form  ; 
and  the  American,  General  Rodman,  proposed  in  1860  to  make  large  grains  of  regular  shape. 
The  use  of  such  powder  was  extended  in  Russia,  by  General  Doremus,  and  also  in  other 
countries,  but  was  found  to  give  better  results  for  blasting  than  for  military  powder.  In 


-    V 


FIG.  216. 


254  ORGANIC    CHEMISTRY 

England,  Armstrong's  grains,  in  the  form  of  hazel-nuts,  met  with  groat  success  and  are 
still  used.  In  1879,  by  means  of  special  hydraulic  presses  (cam-presses),  Wischnegradtky 
prepared  the  first  prismatic  powders,  six  or  seven  holes  being  left  in  each  prism  (Fig.  217)  to 
diminish  the  initial  pressure  on  the  cannon  and  give  a  more  regular  combustion.  Every 
prism  is  25  mm.  high  and  40  mm.  in  diameter,  and  weighs  40  grms.  ;  it  has  the  density 
1-66  and  bears  the  mark  C.66.  It  is  used  for  15  to  26  mm.  guns,  whilst  that  for  larger 
cannon  has  the  same  volume  but  the  sp.  gr.  1-75  (marked  C.75).  The  brown  prismatic 
powder  of  Rottweil  of  Hamburg  has  the  sp.  gr.  1-86  (C.86),  and  is  used  for  large  cannon, 
since  it  burns  slowly,  gives  little  smoke,  and  keeps  well  ;  it  is  prepared  with  rye -straw 
charcoal  and  contains  78  per  cent,  of  nitre,  3  per  cent,  of  sulphur,  and  19 
per  cent,  of  brown  charcoal. 

PACKING.  Powder  is  packed  in  bags  containing  from  50  kilos,  these 
being  placed  in  barrels  or  cases  coated  inside  with  paper  and  outside  with 
cloth.  Each  case  bears  a  label  of  a  colour  indicating  the  nature  of  the 
powder  (rifle,  cannon,  &c.).  Sporting  powder  is  placed  in  tin  boxes 
holding  100,  200,  500,  1000,  or  2000  grms.,  these  being  then  arranged  in 
Fir  217  cases  containing  25  kilos. 

Powder  for  firing  volleys  or  ball  is  converted  directly  into  cartridges, 
which  are  then  stored  in  cases  in  sawdust,  cotton  waste,  or  similar  packing. 

CHARACTERS   AND    PROPERTIES  OF   BLACK    POWDER.     It  has 

a  slate-grey  colour,  and,  if  too  black,  either  it  is  damp  or  it  contains  too  much 
charcoal.  Certain  military  powders  have  a  brown  colour,  as  they  are  prepared 
with  reddish  brown  charcoal.  If  rubbed  on  a  sheet  of  paper  it  should  not  leave 
a  dirty  mark,  as,  if  it  does,  it  contains  dust  or  moisture.  When  a  small  heap  of 
powder  is  ignited  on  a  sheet  of  white  paper  it  should  burn  rapidly  without 
leaving  a  residue  or  burning  the  paper  ;  if  very  black  spots  remain,  there  is 
excess  of  charcoal,  or  if  yellow  ones,  excess  of  sulphur.  On  exposure  to  the 
air,  good  powder  absorbs  only  1-5  to  2  per  cent,  of  moisture,  whilst  as  much  as 
14  per  cent,  may  be  absorbed  by  inferior  powder.  If  the  moisture -content  of 
powder  is  only  5  per  cent,  it  can  be  removed  without  damage  to  the  powder, 
but  moister  powders  cannot  be  restored  to  their  original  strength  by  drying, 
since  the  grains  become  covered  with  a  crust  of  nitre.  The  finer  the  powder  and 
the  richer  in  charcoal,  the  more  hygroscopic  it  is. 

The  temperatures  of  ignition  and  explosion  are  the  same,  and  ignition  or 
explosion  can  be  produced  by  red-hot  iron  or  any  ignited  substance,  or  with  less 
ease  by  percussion,  shock,  or  discharge.  It  is  more  difficult  to  ignite  by  a  blow 
of  iron  on  copper  or  copper  on  copper  than  by  one  of  iron  on  iron  or  brass,  or 
of  brass  on  brass,  &c.  Powder  ignites  more  readily  by  a  spark  or  red-hot  body 
than  by  a  gas-flame.  Guncotton  burns  on  powder  without  igniting  it.  Different 
powders  ignite  between  270°  and  320°  according  to  the  form  of  the  granulation. 

VARIOUS  POWDERS.  During  recent  years  there  has  been  very  keen  rivalry  between 
different  makers  to  prepare  new  powders  for  special  purposes  (even  for  shooting  pigeons  !), 
and  also  blasting  powders  more  economical  than  black  powder.  For  powders  to  be  used 
immediately  or  stored  in  very  dry  magazines,  the  potassium  nitrate  is  replaced  by  sodium 
nitrate  (although  this  is  more  hygroscopic)  which  is  cheaper  and  gives  a  larger  proportion 
of  oxygen  ;  the  charcoal  has  also  been  partially  replaced  by  other  organic  substances  (tar, 
sawdust,  flour,  and  even  horsedung).  These  powders,  often  short-lived,  are  given  most 
extravagant  names  (violette,  gunn,  fulopite,  pyrolite,  pudrolite,  &c.). 

Chlorate  powders,  first  proposed  by  Berthollet  in  1785  to  obtain  greater  power  and 
containing  potassium  chlorate  instead  of  nitre,  have  nqt  been  very  successful,  and  even 
when  a  part  of  the  nitre  is  restored,  accidental  explosions  often  occur  owing  to  the  great 
sensitiveness  to  shock.  In  America,  Devine  (in  1881)  retains  the  potassium  chlorate 
but  keeps  the  ingredients  of  the  powder  separate  until  required  (as  is  done  with  the 
Sprengel  explosives,  p.  245)  ;  thus  rackarock  for  blasting  contains  79  per  cent,  of  potassium 
chlorate  and  21  per  cent,  of  nitrobenzene  (liquid)  mixed  sometimes  with  picric  acid,  sulphur, 
&c.  These  powders  are  rendered  less  sensitive  to  shock  by  mixing  with  a  little  wax  (e.g. 


PERCHLORATE  POWDERS,  DETONATORS  255 

Brank's  powder).  In  1896,  at  St.  Petersburg,  Jevler  prepared  promethus  from  a  solid 
portion  (potassium  chlorate  +  manganese  dioxide  +  ferric  oxide),  and  a  liquid  portion 
(mononitrobenzene  4-  turpentine  oil  +  naphtha)  ;  a  factory  for  this  explosive  was  erected 
in  Italy  in  1905,  but  it  was  destroyed  by  a  terrific  explosion  in  1909,  ten  persons  being 
wounded  and  five  killed.  In  1901  donnar  was  placed  on  the  market  ;  it  contains  56  per 
cent,  of  chlorate  and  24  per  cent,  of  potassium  permanganate  for  the  solid  part,  and  16  per 
cent,  of  nitrobenzene  and  4  per  cent,  of  turpent'ne  for  the  liquid  part.  Also  nitronaphtha- 
lene  and  castor  oil  (5  to  8  per  cent.)  are  used  to  render  the  mixture  more  stable,  e.g.  with 
cheddite  and  with  pierrile  :  80  per  cent,  of  chlorate  +  12  per  cent,  nitronaphthalene  +  6 
per  cent,  castor  oil  +  2  per  cent,  picric  acid  (or,  better,  2  per  cent,  dinitrotoluene),  the 
whole  being  well  mixed  ;  this  powder  has  double  the  power  of  ordinary  blasting  powder. 

More  advantageous  still  are  thought  to  be  the  potassium  perchlorate  powders  (Nisser 
powder,  1865,  contains  :  perchlorate,  10-5  ;  nitrate,  44-5  ;  bichromate,  2  ;  ferrocyanide, 
1-5  ;  sulphur,  15-5  ;  charcoal,  19-5  ;  and  vegetable  substances,  6-5  per  cent.).  Better 
still  are  those  containing  ammonium  perchhrate,  recently  invented  by  U.  Alvisi  (manlianite  : 
72  per  cent,  perchlorate,  14-75  charcoal,  13-25  sulphur  ;  Cannel  powder  :  80  per  cent^of 
perchlorate  and  20  per  cent,  of  cannel  coal  ;  cremonite,  with  48-85  per  cent,  of  ammonium 
perchlorate,  and  51-15  per  cent,  of  ammonium  picrate  ;  and  the  kratites  obtained  by 
mixing  perchlorates  with  nitroglycerine  and  with  nitrocellulose).  Perchlorate  powders 
should  be  used  cautiously,  and  to  render  them  less  sensitive  without  impairing  their 
great  shattering  power,  they  are  mixed  with  urea,  guanidine,  dicyanodiamidine,  &c.  ;  if 
nitrate  is  added,  the  chlorine  is  fixed,  and  the  explosions  then  obtained  are  especially 
suited  to  mines  with  thin  and  extended  seams. 

In  1905  a  patent  was  taken  out  for  a  powder  containing  47  per  cent,  of  ammonium 
nitrate,  1  per  cent,  of  charcoal,  30  per  cent,  of  orthonitrotoluene,  and  20  per  cent,  of  very 
finely  powdered  aluminium,  the  whole  being  compressed  under  a  pressure  of  5000  kilos 
per  square  centimetre,  and  then  moistened  with  nitrotoluene  in  a  water-bath  at  67°. 

DETONATORS  (Caps,  Fuses).  Detonators  serve  to  produce  explosion  of  explosive 
substances.  For  black  powders  it  is  sufficient  to  produce  a  spark  in  the  mass  by  means 
of  a  heated  fuse,  but  with  nitroglycerine  or  guncotton  explosives,  neither  the  fuse  nor  the 
black  powder  causes  explosion,  ignition  being  the  most  they  produce.  In  these  cases 
use  is  made  of  fulminate  of  mercury,  which  explodes  by  simple  percussion  or  heat,  and 
produces  an  explosive  wave  capable  of  inducing  the  explosion  of  these  explosives.  Moist 
or  paraffined  compressed  guncotton  requires  more  powerful  caps  of  dry  guncotton,  these 
being  then  exploded  by  fulminate  of  mercury  detonators. 

FULMINATE  OF  MERCURY,  (C  :  N-O)2Hg,  the  composition  and  constitution  of 
which  are  given  later  (see  Fulminic  Acid),  was  discovered  by  Howard  in  1799  and  studied 
as  regards  its  constitution  by  Gay-Lussac,  Liebig,  Gerhardt,  Kekule,  &c.  Its  manufacture 
requires  great  care  and  exact  proportions  of  the  reagents.  So  long  as  fulminate  of  mercury 
is  moist  it  presents  no  danger,  but  it  must  be  handled  with  extreme  care  when  dry. 

It  is  best  prepared  by  Chandelon's  process  :  into  a  glass  vessel  of  about  4  litres  capacity 
are  placed  100  grins,  of  mercury,  to  which  are  added  1000  grms.  of  nitric  acid  of  40°  Be. 
(sp.  gr.  1-383),  the  liquid  being  stirred  until  all  the  mercury  is  dissolved.  The  greenish 
liquid  is  allowed  to  cool  to  about  20°  and  is  then  poured  into  a  flask  of  at  least  5  litres 
capacity  containing  635  grms.  of  90  per  cent,  alcohol  ;  bumping  or  fuming  of  the  liquid 
is  of  no  consequence.  Very  soon  the  liquid  begins  to  boil  spontaneously,  to  become 
decolorised  and  to  evolve  gas  and  white  poisonous  vapours  (CO,  ethyl  nitrate  and  acetate), 
and  then  yellow  vapours  of  nitrogen  peroxide. 

The  mass  darkens  slightly,  and  when  the  maximum  fuming  occurs,  80  grms.  of  90 
per  cent,  alcohol  are  added  a  little  at  a  time,  and  then  a  further  quantity  of  55  grms.  of 
alcohol,  the  boiling  being  thus  somewhat  attenuated.  After  it  has  been  left  until  the 
white  vapours  have  disappeared,  there  appears  on  the  bottom  a  voluminous  whitish 
powder,  which  is  the  fulminate  of  mercury.  The  operation  lasts  altogether  15  to  20 
minutes  and  should  be  carried  out  under  a  hood  with  a  strong  draught,  or  else  the  flask 
should  be  fitted  with  a  stopper  and  wide  delivery  tube  to  carry  the  vapours  to  a  flue.  The 
product  is  poured  on  to  a  filter,  washed  10  to  15  times  with  water — until  the  wash-water  no 
longer  shows  an  acid  reaction  1 — and  the  filter  with  the  fulminate  spread  out  on  other 

1  The  filtrate  and  the  wash-water  are  utilised  by  first  neutralising  with  milk  of  lime  or  calcium  sulphide  (or  by 
decomposing  with  hydrochloric  acid) ;  from  the  precipitate  the  mercury  is  recovered,  whilst  witherite  is  added 
to  the  liquid  to  form  barium  nitrate  ;  the  alcohol  is  recovered  by  distillation. 


256 


ORGANIC    CHEMISTRY 


absorbent  paper  in  the  air  (not  in  the  sun)  until  it  is  dry  (about  10  per  cent,  of  moisture 
remaining).  To  dry  it  completely  and  safely,  vacuum  drying-ovens  at  a  temperature  below 
40°  are  now  used. 

Theoretically  100  grms.  of  mercury  should  yield  142  grms.  of  the  fulminate,  but  practi- 
cally about  125  to  128  grms.  are  obtained.  In  the  dry  state,  it  is  sold  at  9s.  6d.  to  12s. 
per  kilo  ;  when  not  used  at  once,  it  is  stored  under  water.  If  necessary,  it  can  be  purified 
by  dissolving  in  hot  water  (solubility  1  :  130),  from  which  it  crystallises  on  cooling.  It  is 
whitish  or  sometimes  faintly  yellow  (if  a  small  quantity  of  HC1  or  Nad  is  added  to  the 
nitric  acid  used  in  its  manufacture,  white  crystals  are  obtained),  poisonous  and  soluble  in 
alcohol.1 

It  has  an  extraordinary  shattering  power  owing  to  its  very  great  rapidity  of  explosion. 
It  is  exploded  by  a  blow  or  by  brisk  rubbing,  and  gives  a  pressure  of  27,400  atmos.  When 


FIG.  218. 


FIG.  219. 


heated  slowly  it  explodes  at  152°.  All  objects  used  in  its  manipulation  must  be  of  wood, 
not  of  iron.  Since  it  is  scarcely  ever  used  alone  for  preparing  caps,  but  is  mixed  with 
an  equal  weight  of  potassium  chlorate  and  about  25  per  cent,  of  antimony  sulphide,  it  is 
sometimes,  in  order  to  avoid  explosion,  made  into  a  paste  with  a  thick  solution  of  gum, 
the  required  quantity  being  poured  into  each  copper  cap  (which  contain  about  15  or  20 
mgrms.  of  fulminate  for  sporting  caps  or  1  to  1-5  grm.  for  caps  to  be  used  with  dynamite 
cartridges),  these  being  then  very  carefully  dried  in  vacuum  drying  ovens.  When,  how- 
ever, these  mixtures  are  prepared  in  the  dry  state,  in  order  to  prevent  explosion  the 
mixing  is  carried  out  in  the  apparatus  shown  in  Figs.  218  and  219.  In  a  leather  box,  e, 
a  leather  bag,  /  (the  so-called  "  jelly-bag  ")  is  suspended  by  the  loops  h,  attached  to  the 
gutta-percha  ring,  g.  To  the  bottom  of  the  bag  and  to.the  ring,  g,  are  joined  several  cords 
on  which  are  threaded  rubber  rings,  alternately  large  and  small.  Another  cord,  n,  attached 

1  Analysis  of  Fulminate  of  Mercury  (Brownsdon's  method)  :  the  fulminate  is  first  purified  by  dissolving 
it  in  potassium  cyanide  and  reprecipitating  it  with  dilute  nitric  acid  ;  it  is  filtered,  carefully  dried,  and  a  weighed 
quantity  of  0-04  to  0-05  grm.  dissolved  in  30  c.c.  of  water.  One  gramme  of  thiosulphate  is  then  added  and  the 
liquid  shaken  and  made  up  to  100  c.c  with  water.  The  free  alkali  in  25  c.c.  of  this  solution  is  then  estimated 
by  titration  with  N/10-sulphuric  acid  in  presence  of  methyl  orange  as  indicator. 


E  S 


257 


to  the  lever,  p  q  s,  admits  of  the  bottom  of  the  bag  being  raised  and  lowered  so  as  to  mix  the 
ingredients.  When  mixing  is  complete  the  bottom  of  the  bag  is  drawn  completely  up,  so 
that  the  contents  fall  into  the  space  between  the  bag  and  the  box  and  thence  into  the 
collecting  vessel,  v. 

The  workman  is  protected  from  the  effects  of  a  possible  explosion  during  the  operation 
by  a  semi -cylindrical  wrought-iron  screen,  t.  The  caps  are  then  very  carefully  charged 
by  compressing  the  mixture  with  a  suitable  machine  or  press,  which  gives  a  pressure 
rising  gradually  to  260  atmos.  (pure  fulminate  will  stand  7000  atmos.  without  exploding, 
but  in  presence  of  other  substances,  e.g.  sand  or  coke  powder,  or  other  hard  body,  it  will 
explode  with  a  very  small  pressure).  During  the  charging  the  operative  is  always  sheltered 
by  iron  screens. 

In  general,  no  attempt  is  made  to  economise  in  detonators,  since  the  explosion  has  a 
greater  and  more  complete  effect  if  the  detonator  produces  the  maximum  initial  violence. 

The  explosion  of  detonators  or  caps,  and  hence  of  the  cartridges  or  charges  of  explosive, 
both  in  blasting  and  military  operations,  is  effected  electrically  or  with  fuses. 

Fuses  should  burn  with  a  definite  velocity  so  as  to  allow  the  miners  to  reach  a  place  of 
safety  before  the  explosion.  This  requirement  is  satisfied  by  the  Eickford  fuses  (devised 
in  1831  by  the  Englishman,  Bickford).  These  consist  of  a  compact  cord  prepared  in  a 


FIG.  220. 


FIG.  221. 


FIG.  222. 


special  manner  from  jute  or  cotton  threads,  which  are  spun  round  one  another  in  opposite 
directions  and  are  rendered  impermeable  by  tar  or  gutta-percha.  These  fuses  or  cords, 
5  mm.  thick,  have  an  empty  central  core,  which  is  then  filled  with  finely  granulated,  com- 
pressed powder.  They  then  burn  with  a  velocity  of  1  metre  in  90  seconds.  To  explode 
black  powder,  it  is  sufficient  to  fix  the  fuse  into  the  mass  of  the  charge,  which  explodes  as 
soon  as  the  flame  reaches  it. 

For  dynamite,  gelatine  dynamite,  and  explosive  gums  or  gelatines,  use  is  made  of  a 
fulminate  of  mercury  detonator  which  explodes  a  dynamite  cartridge,  this  then  causing 
explosion  of  all  the  other  cartridges  (without  caps)  surrounding  it.  The  fuse  is  cut  clean 
and  introduced  into  the  bottom  of  the  copper  cap  containing  the  fulminate,  and  is  fixed 
to  the  cap  by  squeezing  it  with  suitable  pincers  (Fig.  220).  The  parchment  paper  at  one 
extremity  of  the  cartridge  is  then  opened  and  the  cap  thrust  into  the  cavity  left  for  it 
(Fig.  221),  the  paper  being  then  tied  tightly  round  the  fuse  with  string  so  that  the  cap  and 
fuse  cannot  become  detached  from  the  cartridge  (Fig.  222). 

Ordinary  fuses,  which  are  very  irregular,  are  obtained  by  soaking  soft  cotton  cord  with 
lead  or  potassium  nitrate  ;  such  fuses  must  be  well  dried  before  use,  as  they  are  hygro- 
scopic. The  cord  may  also  be  impregnated  with  a  paste  of  gum  and  fine  black  powder  and 
then  dried.  Almost  instantaneous  fuses  may  be  made  from  guncotton. 

The  importance  of  tamping  after  the  introduction  of  the  cap  into  the  charge  has  already 
been  mentioned. 

Electric  fuses  are  used,  especially  for  dynamite  and  fulminate  caps,  and  serve  well  for 
producing  the  simultaneous  explosion  of  several  charges,  this  giving  a  greater  effect  than 
separate  explosions  ;  they  are  also  useful  in  galleries  which  contain  firedamp,  as  the 
II  17 


258  ORGANIC    CHEMISTRY 

latter  would  be  exploded  by  a  burning  fuse.  A  spiral  of  thin  platinum  wire  is  fixed  in 
contact  with  a  little  dry  guncotton  above  the  fulminate  of  the  cap.  The  two  ends  of  the 
wire  are  connected  separately  with  two  insulated  wires  joined  to  a  small  battery,  accumula- 
tor, or  hand  dynamo,  which  heats  the  wire  and  so  causes  explosion.  Use  is  often  con- 
veniently (since  the  fragile  platinum  spiral  is  eliminated)  made  of  an  electric  spark  formed 
between  two  platinum  points  very  near  to  one  another  in  a  mixture  of  potassium  chlorate 
and  antimony  sulphide  contained  in  the  cap  ;  in  this  case  the  sparking  is  effected  by  a 
device  similar  to  a  Leyden  jar  (Borrihardt  exploder)  which  gives  a  high-tension  current,  or 
by  one  utilising  induced  currents  (Breguet  exploder)  ;  these  can  be  placed  at  a  distance 
from  the  charge  by  lengthening  the  conducting  wires. 

DESTRUCTION  OF  EXPLOSIVES.  In  various  cases  it  is  necessary  to  destroy 
explosives,  when  these  have  altered  or  undergone  partial  decomposition,  or  when  residues 
are  left  from  samples  submitted  for  analysis.  With  black  powder  it  is  sufficient  to  im- 
merse it  in  water  and  so  dissolve  out  all  the  nitre,  and  then  to  burn  the  barely  dry  in- 
soluble residue.  Water  does  not,  however,  destroy  nitroglycerine  or  the  various  dynamites  ; 
with  these  the  caps  are  carefully  removed  and  also  the  wrapper  (including  the  parchment 
paper),  the  cartridges  being  placed  in  contact  one  with  the  other  on  a  long  strip  of  paper 
in  a  field  free  from  stones  and  away  from  any  building  ;  they  are  then  sprinkled  with 
petroleum  and  a  long  fuse,  attached  to  the  first  cartridge,  lighted.  In  this  way  the  car- 
tridges burn  without  exploding.  With  frozen  dynamite  cartridges  which  have  undergone 
change,  it  is  dangerous  to  handle  them,  and  they  must  be  very  carefully  exploded  one  by 
one  in  the  open  with  a  fulminate  cap  and  fuse.  Nitroglycerine  can  be  made  into  a  paste 
with  sawdust  and  burnt  as  described  above.  Small  quantities  of  explosives  may  be  burnt 
in  pieces  the  size  of  a  pea,  and  small  dynamite  residues  may  be  decomposed  by  heating 
on  a  water-bath  and  frequently  stirring  with  concentrated  alcoholic  caustic  soda  solution. 
STORAGE  AND  CARRIAGE  OF  EXPLOSIVES.  Explosive  factories  are  placed  at 
a  distance  of  about  1000  metres  from  any  dwelling-house  or  frequented  street.  The 
ideas  underlying  the  construction  of  magazines  are  very  varied.  In  some  countries  (Austria, 
Italy,  France,  and,  in  part,  Germany),  the  prepared  explosives  are  distributed  in  a  number 
of  small  magazines  far  from  the  factory,  and  constructed  of  wood  so  as  to  minimise  the 
danger  from  projection  in  case  of  explosion  ;  they  are  separated  by  large  mounds  of  earth 
as  high  as  the  magazine,  so  that  the  explosive  wave  or  projected  material  may  not  reach 
neighbouring  magazines.  Also  in  some  magazines  a  kind  of  wide  bridge  covered  with 
earth  is  constructed  over  the  magazine  to  annul  or  attenuate  the  effect  of  projectiles  falling 
from  above.  In  England,  however,  it  is  assumed  that,  owing  to  the  perfection  of  the 
systems  of  manufacture  and  of  chemical  and  physical  control  of  explosives,  explosion  is 
not  to  be  regarded  as  possible,  so  that  large,  very  solid  magazines  are  built,  either  wholly 
of  cement  or  partly  of  iron,  the  walls  being  half  a  metre  thick.  The  distance  between  the 
separate  magazines  varies  from  100  to  200  metres,  according  as  the  amount  of  explosives 
stored  is  more  than  2000  or  10,000  kilos.  The  flooring  is  of  wood,  and  the  magazines 
are  heated  in  winter  by  means  of  steam -pipes  in  order  to  prevent  freezing  of  the  explosives. 
In  general  there  are  no  windows,  but  only  double  doors  and  small  apertures  ;  artificial 
illumination,  which  is  rarely  used,  consists  of  lamps  placed  outside  the  apertures  or  electric 
lamps  hermetically  sealed  with  gutta-percha  and  fitted  with  several  glass  coverings  ;  in 
some  cases  the  electric  lamps  are  immersed  in  water. 

Any  person  entering  a  magazine  must  wear  felt  slippers  or  leather  boots  without  nails. 
The  most  serious  danger  is  not  that  of  accidental  explosion  but  that  of  lightning.  When 
storms  threaten  all  work  is  suspended,  while  the  magazines  are  protected  from  lightning  by 
all  the  most  modern  appliances.1  Even  the  methods  of  packing  explosives  and  loading 

1  In  general  the  protection  afforded  by  lightning  conductors  is  due  to  the  fact  that  lightning  is  rendered  harmless 
if  it  meets  good  and  sufficiently  extensive  conductors  of  electricity.  There  is,  however,  always  great  danger  if 
inside  or  outside  the  buildings  protected  there  are  large  masses  of  good  conducting  materials,  such  as  the  iron  and 
lead  pipes  of  dynamite  factories,  as  these  may  cause  deflection  of  the  lightning  even  from  its  path  in  the  lightning 
conductors. 

At  the  Nobel  dynamite  factory  at  Kriimmel  on  the  Elbe,  there  was  a  great  explosion  in  1900,  lightning  striking 
the  iron  compressed-air  pipe  and  being  thus  led  to  the  vessels  full  of  nitroglycerine,  which  consequently  exploded. 

Franklin's  principle,  according  to  which  a  metal  rod  furnished  with  points  should  serve  to  discharge  to  earth 
the  large  electric  charges  of  the  clouds,  is  not  applicable  to  the  protection  of  explosive  factories,  since  such  rods 
on  factories  do  not  discharge  the  clouds  to  a  sensible  extent,  but  can  only  serve  to  conduct  the  lightning  to  earth 
after  the  shock.  Much  more  rational  is  Faraday's  method  of  attempting  to  discharge  the  electricity  of  the  clouds 
or  to  conduct  the  lightning  by  so  many  metallic  wires  as  to  prevent  it  from  subdividing,  no  secondary  circuits 
which  might  produce  sparks  being,  however,  formed.  According  to  Faraday,  the  most  certain  protection  against 
lightning  consists  of  a  metal  cage  surrounding  or  covering  the  building  to  be  protected,  and  many  military  explosives 


ANALYSIS    OF    EXPLOSIVES  259 

them  on  waggons  for  transport  are  subject  to  detailed  regulations  :  by  legislation  dating 
from  1875  in  England  and  from  1905  and  1909  in  Germany,  and  in  Italy  by  a  series  of 
laws  and  regulations  of  various  dates.  In  every  case,  a  despatch  must  be  preceded  by  a 
permit  and  by  a  warning  to  all  the  stations  on  the  route.  Explosives  are  despatched  only 
on  certain  days  and  in  certain  trains.  In  Germany,  chlorate  and  perchlorate  travel  with- 
out restrictions.  Owing  to  the  great  stability  of  modern  explosives,  only  6  out  of  265 
accidents  due  to  explosives  occurred  during  transport. 

ANALYSIS  OF  EXPLOSIVES.  The  quantitative  determination  of  the  components  of 
black  powder  is  comparatively  simple  :  10  to  20  grms.  of  the  sample  are  dried  in  an  oven 
until  constant  in  weight  (moisture)  and  are  then  extracted  with  hot  water,  which  dissolves 
the  nitre,  this  being  weighed  or  analysed  separately.  From  the  dried  residue  the  sulphur 
is  extracted  by  carbon  disulphide  in  a  Soxhlet  extraction  apparatus.  The  residue  then 
contains  the  charcoal,  graphite,  and  any  impurities  (sawdust,  mineral  carbon,  &c. )  which 
can  be  identified  under  the  microscope.  The  density  of  the  powder  is  determined  by 
means  of  a  densimeter,  and  the  size  of  the  grains  and  the  quantity  of  dust  by  suitable 
sieves. 

The  analysis  of  dynamites  and  of  smokeless  powders  is  more  complicated  and  must  be 
carried  out  with  great  care.  In  dynamites  with  inert  bases  the  proportions  of  nitroglycerine, 
moisture,  and  inert  substance  are  determined :  8  to  10  grms.  of  the  dynamite,  cut  into  pieces 
the  size  of  peas,  with  a  wooden  or  bone  spatula,  are  weighed  on  a  clock-glass  and  left  in 
a  desiccator  over  calcium  chloride  (not  sulphuric  acid)  for  some  days  until  of  constant 
weight :  the  loss  in  weight  gives  the  moisture.  The  dried  mass  is  extracted  with  pure 
dry  ether  free  from  alcohol,  in  a  Soxhlet  apparatus  (as  in  the  extraction  of  fat,  which  see), 
the  heating  being  effected  with  water  at  50°  to  60°  and  the  ether  subsequently  distilled  with 
water  at  40°  to  50°  away  from  the  neighbourhood  of  a  flame.  The  nitroglycerine  becomes 
turbid  when  almost  all  the  ether  is  evaporated,  but  clear  again  when  the  evaporation  is 
complete  ;  the  nitroglycerine  is  dried  until  constant  in  weight  in  a  vacuum  desiccator  over 
calcium  chloride.  The  residue  left  in  the  extractor  (kieselguhr  or  other  inert  matter)  is 
dried  at  60°  to  70°  and  weighed.  It  is  sometimes  sufficient  to  determine  the  nitroglycerine 
by  difference  from  the  weight  of  this  residue  ;  the  result  is  exact  enough  and  the  operation 
more  rapid  and  less  dangerous. 

Dynamites  with  active  bases  sometimes  have  complex  compositions  and  the  analysis  is 
not  always  so  easy x  ;  in  general,  the  nitroglycerine  and  collodion-cotton  are  separated 
from  the  residue  by  alcohol  and  ether,  from  which  the  collodion -cotton  is  precipitated 
with  chloroform. 

stores  are  effectually  protected  in  this  manner.  In  1900,  Professor  Weber  proposed  the  protection  of  the  Kriimmel 
explosives  factory  by  fixing  to  iron '  columns  galvanised  wire-netting  (88  meshes  per  sq.  metre)  furnished  with 
metal  points  so  as  to  form  a  kind  of  roof  a  metre  or  more  above  the  factory. 

The  columns  are  also  provided  at  the  top  with  metal  points  and  serve  to  conduct  the  electric  discharge  to  the 
earth.  In  the  wires  forming  the  network  sharp  curves  are  avoided  in  order  to  facilitate  conduction  and  hinder 
any  divergence  of  the  lightning.  Above  the  buildings  of  the  Kriimmel  factory  there  are  24,000  metres  of  metal 
wire  with  five  million  points,  which  may  contribute  in  some  measure  to  discharge  the  clouds,  and  would  certainly 
conduct  the  lightning  to  earth  after  a  discharge.  The  ideal  method  would  consist  in  using  copper  wire  1  crn.  in 
diameter,  but  the  expense  of  this  would  be  enormous.  The  earth-contact  is  made  in  wet  places  with  iron  plates 
or  rails  one  or  two  metres  under  the  soil.  Also  the  metal  piping  (if  not  replaceable  by  rubber  tubing)  and  apparatus 
of  the  various  parts  of  the  factory  are  connected  with  the  earth-conductors  of  the  lightning  conductors,  so  as  to 
avoid  the  formation  of  sparks  in  the  discharge  of  the  lightning. 

It  has  also  been  suggested  that,  where  possible,  the  large  vessels  in  the  separate  buildings  should  be  electrically 
insulated,  both  from  the  lightning  conductors  and  from  the  earth. 

1  For  dynamites  with  active  bases  (containing  nitroglycerine,  collodion-cotton  or  guncotton,  nitrates,  sawdust, 
&c.),  Stillman  and  Austin  (1906)  propose  a  method  of  analysis  which  is  briefly  as  follows  :  The  moisture  is 
determined  on  10  grms.  as  above ;  the  dry  mass  is  then  extracted  several  times  in  the  cold  with  a  mixture  of  1 
part  of  alcohol  and  2  parts  of  ether.  The  residue  (A)  is  dried  and  weighed  (for  its  analysis  see  later),  the  solution 
being  left  to  evaporate  in  the  cold  to  100  c.c.,  to  which  are  added  100  c.c.  of  chloroform  to  precipitate  the  collodion- 
cotton.  The  liquid  is  decanted  on  to  a  tared,  dry,  cloth  filter  on  to  which  all  the  collodion-cotton  is  brought  by 
means  of  chloroform  ;  the  filter  is  dried  in  an  oven  at  40°  and  then  in  a  desiccator  and  weighed  (as  a  check,  it  is 
rcdissolved  in  alcohol  and  ether,  reprecipitated  with  chloroform,  collected  on  a  filter  and  dried  at  40°,  the  collodion 
being  then  detached  from  the  filter,  completely  dried  on  a  watch-glass  in  a  desiccator  and  weighed).  After  the 
collodion-cotton  is  separated,  the  decanted  and  filtered  liquids  are  evaporated  in  a  tared  vessel,  dried  in  a  vacuum 
and  the  remaining  nitroglycerine  weighed. 

If  the  nitroglycerine  contains  traces  of  nitrates,  these  are  extracted  by  repeated  treatment  with  small  quantities 
of  water,  the  solution  being  then  evaporated  and  the  nitrates  weighed.  If  along  with  the  nitroglycerine  there 
are  also  resin,  paraffin,  and  traces  of  sulphur,  it  is  titrated  with  excess  of  normal  alcoholic  caustic  soda  in  the  hot, 
the  excess  of  alkali  being  then  determined  with  normal  acid  in  presence  of  phenolphthalein  :  1  c.c.  of  normal  alkali 
used  in  the  saponittcation  corresponds  with  0-0757  grm.  of  nitroglycerine  (in  case  no  resin  is  present).  After  the 
titration,  the  liquid  is  evaporated  almost  to  dryness  to  eliminate  the  alcohol  and  is  then  diluted  with  water  and 
shaken  with  ether  in  a  separating  funnel. 

The  ethereal  solution  is  separated  and  evaporated,  and  the  residual  paraffin  weighed.      The  aqueous  liquid 


260 


ORGANIC    CHEMISTRY 


The  resistance  to  heat  of  nitroglycerine  and  of  dynamite  is  determined  as  with  nitro- 
cellulose (see  below),  the  nitroglycerine  being  extracted  from  dynamite  by  displacement 
with  water,  and  the  gelatine  explosives  being  mixed  with  double  their  weight  of  chalk  prior 
to  extraction  with  solvents  ;  it  should  withstand  a  temperature  of  70°  for  at  least  15 
minutes  without  colouring  starch  and  potassium  iodide  paper.  In  contact  with  sensitive 
blue  litmus  paper  it  should  not  give  the  slightest  reddening,  as  this  would  indicate  incipient 
decomposition. 

Exudation  of  nitroglycerine  from  dynamite,  in  either  the  cold  or  the  hot,  shows  faulty 
manufacture. 

With  nitrocellulose,  besides  testing  its  solubility  in  a  mixture  of  1  part  of  alcohol  and 
2  parts  of  ether  which  dissolves  collodion-cotton  but  not  guncotton,  the  nitrogen  is  often 
estimated  in  the  Lunge  nitrometer  (vol.  i,  p.  460)  by  shaking  with  concentrated  sulphuric 
acid  ;  or  Schlosing's  method,  as  used  in  France,  may  be  employed  to  ascertain  the  type  of 
the  nitrocellulose  :  into  a  150  c.c.  flask  are  placed  25  grms.  of  pure,  powdered  ferrous 
sulphate,  0-7  to  0-8  grm.  of  nitrocellulose,  and  70  to  80  c.c.  of 
hydrochloric  acid  ;  the  flask  is  shaken  and  then  fitted  with  a  stopper 
through  which  pass  a  delivery-tube  and  another  tube  conveying  a 
current  of  carbon  dioxide  ;  when  all  the  air  is  expelled  the  delivery- 
tube,  dipping  into  a  vessel  of  mercury,  is  covered  with  a  graduated 
tube  filled  half  with  mercury  and  half  with  caustic  soda  solution. 
The  flask  is  then  heated  to  boiling,  when  the  liquid  blackens  and  in 
ten  minutes  all  the  nitric  oxide  is  evolved,  the  last  traces  of  this  gas 
being  driven  out  by  a  stream  of  carbon  dioxide.  The  volume  of  gas 
gives  the  amount  of  nitrogen. 

The  amount  of  non -nitrated  cotton  is  determined  by  boiling  5  grms. 
of  the  substance  with  a  saturated  solution  of  sodium  sulphide,  the 
liquid  being  decanted  after  a  stand  of  24  hours  and  the  treatment 
with  sodium  sulphide  repeated  ;  the  residue  is  finally  collected  on  a 
tared  cloth  filter,  washed  with  boiling  water,  then  with  dilute  hydro- 
chloric acid  and  lastly  with  boiling  water  again  ;  it  is  then  dried  and 
weighed. 

The  resistance  to  heat  (Abel's  heat  test)  of  nitrocellulose  is  of  im- 
portance, as  it  serves  as  a  control  during  manufacture  and  is  used  also 
as  a  test  for  nitroglycerine  :  a  wide-mouthed  glass  flask,  A  (Fig.  223), 
20  cm.  in  diameter,  and  with  no  neck,  is  almost  filled  with  water  and 
is  covered  with  a  leather  disc  pierced  by  four  holes  provided  with  wire 
clips  for  holding  test-tubes  ;  the  flask  is  heated  below  by  a  small  lamp,  F,  placed  under  a 
metal  gauze  and  surrounded  by  a  screen,  D.  The  central  aperture  carries  a  thermometer, 
and  one  of  the  others  a  ther  mo -regulator  (if  necessary),  whilst  in  the  remaining  ones  are 
placed  test-tubes  which  contain  the  nitrocellulose  (1  to  3  grms.)  or  nitroglycerine  (2  c.c.) 
and  dip  into  the  water.  Each  of  the  stoppers  of  the  test-tubes  is  fitted  with  a  hook 
of  glass  tubing  on  which  is  hung  a  piece  of  starch-potassium-iodide  paper  moistened  at 
the  upper  part  with  a  drop  of  dilute  glycerine. 

The  temperature  of  the  bath  is  maintained  at  64°  to  65°  or  at  80°  to  82°,  according 
to  the  commercial  requirements  of  the  explosive.  The  test  is  finished  when  a  faint  brown 
coloration  appears  at  the  edge  of  the  glycerine.  A  good  guncotton  will  withstand  heating 
at  80°  for  half  an  hour  without  browning  the  paper. 

after  separation  of  the  ethereal  solution,  is  heated  with  a  little  bromine  to  oxidise  the  sulphur ;  it  is  then 
acidified  with  HC1,  boiled,  and  the  resin  collected  on  a  tared  filter,  whilst  in  the  filtrate  the  sulphuric  acid  formed 
by  oxidation  of  the  sulphur  is  precipitated  with'  BaCl2. 

The  nitroglycerine  may  be  estimated  by  difference,  by  subtracting  from  the  original  weight  the  insoluble  residue, 
A,  the  paraffin,  the  resin,  the  small  amount  of  sulphur,  and  the  nitrates. 

The  residue,  A,  insoluble  in  alcohol  and  ether  (see  above),  is  extracted  with  hot  water ;  the  undissolved  part 
is  dried  at  70°  and  weighed  (B  =  sawdust  +  sulphur  +  any  insoluble  mineral  substances) ;  the  sulphur  is  extracted 
with  carbon  disulphide,  and  weighed,  this  weight  subtracted  from  B  giving  the  sawdust,  from  which  also  the  weight 
of  ash  left  after  calcining  is  subtracted  if  inorganic  substances  are  present. 

The  aqueous  solution  obtained  from  A  is  evaporated,  dried  at  110°  and  weighed  (C  =  nitrates  +  carbonates  -f 
any  woody  extract) ;  it  is  then  treated  with  a  little  nitric  acid,  evaporated,  dried  and  weighed  (-D) ;  from  the 
difference  between  C  and  D  the  CO2  evolved  and  hence  the  carbonates  can  be  calculated. 

The  mass,  D,  is  melted,  heated  to  redness,  cooled,  treated  with  a  little  dilute  nitric  acid,  evaporated,  dried  at 
110°  and  weighed  (E) ;  this  weight  gives  the  sodium  and  potassium  nitrates.  Subtraction  of  the  weights  of  nitrates 
(E)  and  carbonates  from  C  gives  that  of  the  extractive  matters  and  of  ammonium  nitrate,  if  this  is  present ;  this 
latter  may  be  determined  in  the  aqueous  liquid,  A,  by  estimating  the  ammonia  evolved  in  the  ordinary  way. 


FiG.  223. 


POWER    OF    EXPLOSIVES 


261 


FIG.  224. 


Measurement  of  the  Pressure  or  Heat  of  the  Gases  Developed  by  Explosives.  The 
power  of  an  explosive  is  deduced  principally  from  the  quantity  of  heat  produced  on  explosion 
(see  p.  216),  this  being  measured  in  the  Berthelot-Mahler  calorimetric  bomb  (see  vol.  i,  p.  372). 
Deflagration  is  induced  by  means  of  an  electric  spark,  and  if  considerable  pressure  is  main- 
tained in  the  bomb  by  means  of  air  (or  nitrogen  in  the  case  of  guncotton,  as  this  is  deficient 
in  oxygen,  which  need  not  be  supplied  in  order  to  reproduce  the  conditions  of  an  ordinary 

explosion),  the  products  of  deflagration  are  almost  identi- 
cal with  those  of  explosion.  The  bomb  is  specially  con- 
structed with  various  accessories  to  allow  of  the  analysis 
and  measurement  of  the  gases  produced  in  the  decom- 
position, at  either  low  or  high  pressure,  of  the  explosive. 
The  pressure  of  the  gases  produced  by  the  explosion 
in  a  resistant  chamber,  C  (Fig.  224),  of  soft  sheet  steel 
wrapped  round  with  steel  wire,  is  measured  indirectly  by 
determining  the  crushing  of  a  small  copper  cylinder,  Z 
(crusher),  13  mm.  high  and  8  mm.  in  diameter,  placed 
between  a  fixed  base,  d,  and  a  hardened  steel  piston,  a, 
of  known  surface  which  transmits  the  pressure  of  the 
gases.  The  chamber,  C,  is  fixed  by  two  massive  wrought- 
iron  plates,  D  and  D',  held  together  by  six  thick  rods,  B. 
Deflagration  is  caused  by  rendering  incandescent  a 
platinum  wire  between  the  two  terminals,  6.  In  order 
to  obtain  exact  results  it  is  indispensable  that  there  can 
be  no  escape  of  the  gas,  which  would  also  cause  danger 
from  projection,  the  gas  being  at  a  temperature  of  2000° 
to  3000°  and  a  pressure  of  several  thousand  atmospheres. 

The  deformation  of  the  crushers  is  shown  in  almost  the  natural  dimensions  in  Fig.  179 
on  p.  219. 

The  sensitiveness  of  explosives  to  a  blow  is  determined  empirically  by  allowing  a  given 
weight  of  iron  (ram)  to  fall  from  various  heights  on  to  a  certain  amount  of  explosive  placed 
on  an  iron  block,  the  height  of  the  fall  being  increased  until  explosion  occurs.  The  sensitive- 
ness to  heat  is  measured  roughly  by  throwing  small  pieces  of  the  explosive  on  to  mercury 
heated  to  successively  increasing  tem- 
peratures until  deflagration  takes 
place. 

When  the  power  of  an  explosive 
cannot  be  determined  directly  or  by 
comparison  of  the  practical  effects, 
indirect  tests  must  be  employed, 
although  these  do  not  always  cor- 
respond with  the  actual  effects.  To 
avoid  uncertainty,  the  expression 
power  of  an  explosive,  f,  is  applied 
to  the  product  of  the  volume,  v°,  of 
gas  (reduced  to  0°  and  formed  from 
unit  weight  of  the  explosive),  the 

pressure,    p0,   of   760  mm.,    and   the  FIG.  225. 

absolute   temperature,   T    (calculated 
from  the  products  of  the  reaction),  this  product  being  divided  by  273,  so  that : 


273  ' 

The  power  of  progressive  explosives  may  be  indirectly  determined  by  Guttmann's 
power  gauge  (Fig.  225):  on  a  hollow  block  of  steel,  a  (diameter  of  cavity  35  mm.),  are 
screwed  two  steel  blocks,  b,  and  a  small  firing-plug,  g.  A  trigger,  m,  which  can  be  released 
from  a  distance  by  means  of  a  cord,  serves  to  explode  the  plug.  The  apparatus  is  charged 
by  unscrewing  one  of  the  blocks,  b,  and  introducing  first  a  cylinder  of  drawn  lead,  40  mm. 
long  and  35  mm.  in  diameter,  which  closes  hermetically  the  wide  mouth  of  the  right-hand 
cone  :  then  a  steel  disc  and  one  of  cardboard  of  such  thickness  that  it  makes  20  grms. 


262 


ORGANIC    CHEMISTRY 


of  powder  rest  just  in  the  middle.  This  powder,  which  is  introduced  next,  is  situate  just 
under  the  cap,  h.  Then  follow  a  disc  of  cardboard,  one  of  steel,  and  a  block  of  lead 
similar  to  the  first,  this  closing  the  cavity  to  the  left,  when  the  block,  b,  is  again  screwed 
on.  The  gases  produced  by  the  explosion  have  no  outlet  and  so  force  the  leaden  blocks 
to  the  right  and  left  into  the  conical  holes  to  the  right  and  left.  The  height  of  the  leaden 
cones  projecting  is  compared  with  that  obtained  with  a  standard  explosive  and  thus  gives 
the  power  of  the  explosive. 


FIG.  226. 

For  shattering  explosives,  on  the  other  hand,  good  results  are  obtained  with  Trauzl's 
lead  block,  which  is  in  the  form  of  a  cylinder  200  mm.  in  height  and  diameter.  In  the 
middle  is  a  cavity,  110  mm.  deep  and  20  mm.  wide,  into  which  15  to  20  grms.  of  the  ex- 
plosive are  placed.  A  fulminate  cap,  connected  with  wires  for  firing,  is  inserted  and  the 
bore  tamped  with  well -compressed  sand  and 
chalk.  After  the  explosion,  the  capacity  of  . 

the  cavity  is  measured  with  water.     Fig.  226  \ 

shows  several  of  these  blocks  after  testing  with 
various  explosives.  A  charge  of  15  grms.  of 
No.  1  dynamite  gives  a  volume  of  705  c.c.,  and 


FIG.  227. 


FIG.  228. 


deducting  from  this  30  c.c.  for  the  original  volume,  and  30  c.c.  produced  by  the  1-5  grm.  of 
fulminate  in  the  cap,  there  remain  645  c.c.  due  to  the  explosive,  i.e.  43  c.e.  per  gramme.  To 
obtain  comparable  results  with  explosives  of  the  same  class,  charges  of  equal  weights  must 
be  taken,  otherwise  different  values  are  obtained  for  the  same  explosive  ;  there  are,  besides, 
other  causes  of  error,  which  give  only  a  relative  value  to  this  method  of  determining  the  power. 
Measurement  of  the  Initial  Velocity  of  Projectiles.  For  this  purpose  use  is  made  of 
Le  Boulenge's  chronograph  (Figs.  227  and  228),  which  gives  the  velocity,  V,  by  measuring 


USES    OF    EXPLOSIVES:    STATISTICS       263 

the  time,  T,  taken  by  the  projectile  to  traverse  the  known  distance,  D  (20  to  50  metres), 
between  two  wire  frames,  G,  G'  (Fig.  227),  which  are  cut  through  by  the  projectile  im- 
mediately after  it  leaves  the  gun  and  are  connected  electrically  with  two  quite  distinct 
points  of  the  chronograph,  the  apparatus  being  so  arranged  that  T  lies  between  0-05  and 

D 
0-15  second  ;    V  =  ™  .     The  chronograph  is  formed  of  two  electro -magnets,  a  and  e  (Fig. 

218,  or  C  and  C',  Fig.  217),  joined  to  the  batteries  B  and  B',  and  to  the  corresponding 
wire  frames,  Cr  and  G'.  The  magnet,  a,  attracts  a  tubular  bar  (c,  d,  Fig.  228,  or  C,  Fig.  227) 
of  the  chronometer,  which  terminates  at  the  top  in  a  soft  iron  point  and  is  enlarged  at  the 
bottom  ;  the  magnet,  e  (or  A'  in  Fig.  227),  attracts  a  rod,  /  (or  C',  Fig.  227),  of  the  registrar. 
The  chronometer  bar  is  surrounded  by  a  thin  zinc  or  copper  tube.  The  registrar  is  of  soft 
iron,  has  the  same  weight  as  the  chronometer,  and  is  pointed  at  the  top  and  enlarged 
at  the  bottom.  When  the  projectile  traverses  the  first  frame,  G,  it  interrupts  the  current 
of  the  electro -magnet,  A,  and  the  chronometer  bar,  C,  becomes  detached  from  A  (Fig.  227) 
and  begins  to  fall  freely.  When  it  traverses  the  second  frame,  G',  it  interrupts  the  current 
of  the  electro -magnet,  A',  and  the  registrar,  C',  falls  and  releases  a  hook  which  liberates  a 
horizontal  spring  pointer,  this  immediately  striking  the  falling  chronometer  bar.  The 
mark  on  this  bar  will  be  the  higher  the  lower  the  initial  velocity  of  the  projectile.  Suitable 
tables  deduced  from  simple  formulae  l  give  the  required  velocity. 

The  velocity  of  detonation  is  difficult  to  determine,  since  it  depends  largely  on  the 
resistance  of  the  enclosure  containing  the  explosive  and  on  other  circumstances.  It  is 
determined  roughly  but  with  sufficient  exactitude,  under  similar  conditions,  by  placing  a 
number  of  cartridges  in  a  continuous  row  and  joining  the  two  wires  of  the  Le  Boulenge 
chronograph  to  points  in  the  row  at  a  certain  distance  apart. 

USES  OF  EXPLOSIVES.  The  largest  consumption  of  explosives  is  that 
of  armies  and  navies,  whilst  in  various  civil  operations  these  substances  are 
also  employed  :  in  the  tunnelling  of  mountain  ranges  separating  various  races  ; 
in  lessening  manual  labour  in  the  ploughing  of  the  soil ;  for  disintegrating 
rocks  to  provide  material  for  the  construction  of  houses  to  displace  the  all  too 
numerous  deserts  ;  and  further,  for  preparing  blocks  of  material  to  be  wrought 
by  the  genius  of  man  into  monuments  attesting  to  posterity  the  varied  and 
incessant  progress  of  human  thought  and  labour. 

In  practice  a  sharp  distinction  is  made  between  progressive  explosives,  used 
more  especially  in  mines  for  detaching  large  masses  of  rock  and  for  excavating 
(for  coal,  minerals,  gold,  and  diamonds),  and  shattering  explosives  (dynamite, 
&c.),  employed  for  such  purposes  as  demolishing  walls,  bridges,  and  large 
trees,  or  breaking  the  ice  at  the  surface  of  rivers  and  lakes  when  navigation  is 
prevented.  To  demolish  a  large  tree  it  is  sufficient  to  surround  it  with  a  string 
of  dynamite  cartridges,  explosion  of  one  of  which  will  cause  explosion  of  the 
others  ;  to  break  iron,  e.g.  a  railway  rail,  or  cut  a  bridge,  one  or  more  cartridges 
are  placed  on  it,  covered  with  a  light  tamping  of  earth  and  exploded.  In  sub- 
aqueous works  modern  smokeless  explosives  are  of  great  service,  since  to  their 
great  power  is  added  their  stability  towards  water,  which  acts  as  an  excellent 
tamping. 

STATISTICS  OF  EXPLOSIVES.  In  1908  Italy  produced  764  quintals  of  cheddite, 
580  of  solenite,  556  of  prometheus,  280  of  guncotton,  2153  of  collodion-cotton,  56  of 

1  A  test  is  first  made  in  which  the  chronometer  bar  and  the  registrar  fall  simultaneously.  The  height,  h,  at 
which  the  former  is  struck  corresponds  with  a  time,  t,  which  must  always  be  allowed  for  in  the  subsequent  measure- 
ments, as  it  represents  the  time  required  by  the  registrar  to  release  the  spring.  According  to  the  law  of  bodies 

falling  freely,  h  =  4<#!,  so  that  t  —  \/  —  ;  in  practice,  when  a  time,  T,  elapses  during  the  passage  of  the  projectile 

9  

from  O  to  G',  the  mark  on  the  chronometer  bar  at  the  height,  H,  corresponds  with  a  time,  T  +  t  —  \  — ;    The 

ff 

difference  between  these  two  measurements  gives  the  time  required,  the  velocity  being  then  deduced  from  the 
D 

formula :  V  =   .  /z~7     "  _\  . 


264  ORGANIC    CHEMISTRY 

fulminate  of  mercury,  and  23,000  of  powder  for  fireworks.  The  various  explosives 
factories  in  Italy  employ  almost  3000  workmen. 

The  consumption  of  explosives  in  time  of  war  is  enormous.  Every  shot  of  a  large  gun, 
which  does  not  always  hit  the  mark,  costs  hundreds  of  pounds.  In  the  last  Russo-Japanese 
war,  the  besiegers  of  Port  Arthur  blew  up  part  of  one  of  the  forts  with  a  mine  containing 
5000  kilos  of  dynamite.  During  the  piercing  of  the  Simplon,  1640  tons  of  gelatine 
explosives  were  used,  mostly  with  a  content  of  about  92  per  cent,  of  nitroglycerine.  In 
constructing  the  harbour  of  Genoa,  the  Nobel  Company  exploded  simultaneously  a  number 
of  mines  with  a  total  charge  of  6000  kilos  of  dynamite.  For  the  removal  in  1905  of  a  rock 
that  partially  obstructed  the  Danube  at  Greisenstein,  a  mine  was  laid  with  11,700  kilos 
of  dynamite  ;  280,000  cu.  metres  of  rock  were  detached  at  a  cost  of  about  three -half  pence 
per  cubic  metre.  In  the  American  Independence  Day  fetes,  a  million  pounds  worth  of 
fireworks  are  consumed  every  year. 

In  addition  to  its  enormous  home  consumption,  Germany  exported,  in  1906,  2136  tons 
of  black  powder  of  the  value  of  £320,000  ;  4791  tons  of  other  explosives,  worth  £372,000  ; 
and  7300  tons  of  cartridge  charges  for  guns  and  artillery,  of  the  value  of  £1,000,000. 

In  the  United  States  the  industry  is  a  rapidly  growing  one.  While  the  total  production 
was  £3,400,000  (including  40,000  quintals  of  dynamite)  in  1900,  it  rose  in  1905  to 
£5,920,000,  of  which  £1,760,000  represented  black  powder  ;  £320,000  nitroglycerine  ; 
£3,200,000  dynamite  ;  £800,000  smokeless  powder  ;  and  £35,200  guncotton. 

In  1909  the  United  States  possessed  86  explosives  factories  with  a  total  capital  of 
£10,000,000  and  a  total  annual  output  of  the  value  of  £8,000,000. 

The  world's  production  of  explosives  reaches  a  total  of  350,000  to  400,000  tons,  almost 
the  half  of  this  amount  being  made  in  the  United  State?.  According  to  0.  Guttmann,  the 
production  of  explosives  with  nitroglycerine  as  base  amounted  in  1909  to  more  than 
62,000  tons,  distributed  as  follows  :  United  States,  20,000  tons  ;  Germany,  10,300  ; 
England,  8100  ;  the  Transvaal,  8000  ;  Canada,  5000  ;  Spain  and  Portugal,  3500  ; 
Austria-Hungary,  2300  ;  France,  1500  ;  Switzerland,  Australia,  and  Norway  and  Sweden, 
600  each  ;  Russia,  Italy,  and  Holland  and  Belgium,  about  500  each  ;  and  Greece,  175  tons. 
For  dynamite  for  military  purposes,  Japan  requires  annually  9000  quintals  of  nitroglycerine, 
and  consumes,  in  addition,  9000  quintals  of  other  powders.  Only  a  small  portion  of  these 
is  manufactured  in  Japan,  which  imports  every  year  explosives  of  the  value  of  £80,000 
(from  England,  Germany,  and  Belgium)  ;  in  1909  the  Armstrong  firm  erected  a  cordite 
factory  near  Yokohama.  In  the  Transvaal  mines  explosives  to  the  value  of  £1,440,000 
were  consumed  in  1910. 

EE.  ACIDS 

I.  SATURATED  MONOBASIC  FATTY  ACIDS,   CwHanO2 

These  are  termed  fatty  acids  because  some  of  them  are  contained  in  fats,  from 
which  they  are  prepared.  All  contain  the  characteristic  group,  —  C02H,  the 
hydrogen  of  which  is  replaceable  by  metals.  With  every  hydrocarbon  or  every 
primary  alcohol  of  the  methane  series  corresponds  a  monobasic  fatty  acid. 
The  first  members  are  liquids  having  a  pungent  odour,  and  are  soluble  in  water, 
alcohol,  or  ether,  and  boil  without  decomposing  ;  then  follow  members  of  an 
oily  consistency,  less  soluble  in  water,  and  with  unpleasant  smells  like  that  of 
rancid  butter  or  perspiration  ;  beyond  C10  they  are  solid,  insoluble  in  water, 
soluble  in  alcohol  or  ether,  and  distilling  unchanged  only  in  a  vacuum.  The 
first  members  (up  to  C9  or  C10)  are  volatile  in  steam. 

It  will  be  seen  that  the  boiling-points  of  these  acids  rise  regularly  with 
increase  in  the  number  of  carbon  atoms,  but  the  melting-points  are  higher  in  an 
acid  with  an  even  number  of  carbon  atoms  than  jn  those  immediately  below 
and  above  with  uneven  numbers. 

GENERAL  METHODS  OF  PREPARATION,  (a)  In  dealing  with 
primary  alcohols  and  aldehydes,  it  was  shown  how  simple  oxidation  of  these 
compounds  yields  the  corresponding  acids  containing  the  same  number  of 
carbon  atoms,  whilst  when  secondary  and  tertiary  alcohols  or  ketones  are 


FATTY    ACIDS 

TABLE  OF  THE  SATURATED  MONOBASIC  FATTY  ACIDS 


265 


Formula 

Name 

Melting-point 

Boiling-point 

Specific  gravity 

CH202 

Formic 

+    8-3° 

101° 

1-2187  (20°) 

C2H4O2 

Acetic 

+  16-5° 

118° 

1-0502  (20°) 

C3H6O2 

Propionic 

-22° 

141° 

1-013  (0° 

\ 

C4H802 

j  Normal  butyric 
^Isobutyric 

•    7-9° 

-  79° 

162° 
154° 

0-987  (0° 
0-965  (0° 

1 

(Normal  valeric 

-  58-5° 

185° 

0-956  (0° 

Isovaloric 

-  51° 

174° 

0-947  (0° 

1 

5      10     2 

1  Trimethylacetic 

+  34°-35° 

163° 

0-905  (50 

°) 

[  Methylethylacetic 

— 

173°-174° 

0-938  (20 

°) 

C6H,2O2 

Normal  caproic  (hexoic) 

1-5° 

205° 

0-945  (0° 

C7H14O2 

Normal  heptoic 

-  10° 

223° 

0-921  (15 

°) 

C8H1602 

Caprylic  (octoic) 

+  16-5° 

237-5° 

0-910  (20 

°) 

C9H18O2 

Pelargonic  (nonoic) 

+  12-5° 

186°  \ 

0-911  (12 

°) 

QoHaoOa 

Capric  (decoic) 

+  31-4° 

200° 

OJ 

0-930  (37 

°) 

C11H22O2 

U/idecoic 

28° 

212° 

.3 

— 

r<    w    <"» 

^12      24^2 

Laurie 

44° 

225° 

03 

9 

0-875 

-g 

C^HaeC^ 

Tridecoic 

40-5° 

236° 

OH 

— 

•5 

^14^2802 

Myristic 

54° 

248° 

>  a 

0-862 

bC 

Ci5H30O2 

Pentadecoic 

51° 

257° 

a 

— 

Cj6H32O2 

Palmitic 

62-6° 

268° 

o 
o 

0-853 

" 

Ci7H34O2 

Margaric 

60° 

277° 

+3 

— 

a 

C18H3602 

Stearic 

69-3° 

287° 

0-845 

<3 

C19H38O2 

Nonadecoic 

66-5° 

298% 

— 

C20H4002 

Arachidic 

77° 

— 

— 

C22H4402 

Behenic 

84° 

360°/60  mm. 

— 

C24H4802 

Lignoceric 

80°-81° 

— 

— 

C26H52O2 

Cerotic 

78-5° 

— 

— 

C30H6002 

Melissic 

91° 

— 

— 

oxidised,  the  chain  is  broken  and  acids  with  a  less  number  of  carbon  atoms 
are  obtained. 

(b)  Hydrolysis  of  the  nitriles  (see  these)  in  the  hot  with  potassium  hydroxide 
or  with  mineral  acids  yields  the  amides  (see  these)  as  intermediate  compounds, 
and  then  the  acids  with  one  carbon  atom  more  than  the  alcohols  from  which 
the  nitriles  originate  : 


CH3-CN 


2H20  -  NH3 


CH3-C02H. 


(c)  The  interaction  of  a  zinc-alkyl  with  phosgene  gives  : 

Zn(CH3)2  +  2COC12  =  ZnCl2  +  2CH3-COC1  (Acetyl  chloride), 
which,  on  decomposition  with  water  gives  : 

CH3-COC1  +  H20  =  HC1  +  CH3-CO2H. 

(d)  When  a  hydroxy-acid  is  heated  with  hydrogen  iodide,  separation  of 
water  and  iodine  occurs  and  a  fatty  acid  is  formed. 

(e)  Other  general  reactions  are  those  of  Grignard  (see  p.  203),  those  of  ethyl 
acetoacetate  and  ethyl  malonate  (see  these),  and  those  of  elimination  of  C02 
from  dibasic  acids   (containing  two  carboxyls,  CO  -OH)  and  of  addition  of 
hydrogen  to  unsaturated  acids,  &c. 

PROPERTIES.  In  aqueous  solution  the  acids  are  electrolytically  dis- 
sociated into  the  cations  H  and  the  anions  R-  C02  (see  vol.  i,  p.  91). 

Substitution  of  this  ionic  hydrogen  by  a  metal  yields  salts,  which  in  aqueous 
solution  (when  they  are  soluble)  are  almost  completely  dissociated,  whilst  the 


266  ORGANIC    CHEMISTRY 

hydrogen  of  the  alcohols  is  also  replaceable  by  a  metal  (alkoxide),  but  the 
resulting  alkoxide  is  decomposed  by  water  (hydrolysed). 

The  strength  of  an  acid  (or  its  power)  can  always  be  determined  from  the 
degree  of  dissociation  (vol.  i,  p.  98);  this  decreasing  in  the  following  order  : 
formic,  acetic,  propionic,  normal  butyric,  valeric,  &c.  ;  thus,  with  rise  of  the 
molecular  weight  the  dissociation  diminishes. 

The  hydroxyl  group  of  the  carboxyl  group,  —CO  -OH,  can  sometimes 
be  substituted  by  halogens  (especially  by  chlorine,  by  the  action  of  PC15,  which 
forms  acid  chlorides  or  chloroanhydrides,  e.g.  acetyl  chloride,  CH3-COC1). 

Substitution  of  the  hydroxyl,  (1)  by  SH,  gives  thio-acids,  and  (2)  by  NH2 
yields  the  amides,  e.g.  acetamide,  CH3-CO-NH2  (by  heating  ammonium 
acetate)  ;  under  certain  conditions  these  compounds  all  give  the  acids  from 
which  they  originate. 

It  has  already  been  mentioned  that  the  saturated  hydrocarbons  are  formed 
by  the  electrolysis  of  the  alkali  salts  of  the  corresponding  acids,  with  elimination 
of  C02,  H,  and  0  (the  last  two  from.  the  water  present  as  solvent)  and  also  of 
secondary  products  (unsaturated  ethers  and  hydrocarbons)  ;  if  the  electrolysis 
is  effected  without  a  diaphragm,  alkaline  carbonate  and  bicarbonate  are  formed, 
and  hence  also  a  lower  alcohol.  Carbon  dioxide  can  also  be  eliminated,  and 
hydrocarbons  thus  formed,  from  the  alkali  salts  of  the  acids  by  heating  in 
presence  of  soda-lime  or  baryta,  or  by  reducing  the  acids  with  hydriodic 
acid  and  phosphorus. 

But  if  the  calcium  salts  of  the  acids  are  distilled,  with  or  without  P205,  the 
principal  product  is  a  ketone  formed  from  two  molecules  of  the  acid  : 

(CH3-COO)2Ca  =  CaC03  +  CH3-CO-CH3  ; 

if  the  calcium  salt  is  heated  in  presence  of  calcium  formate,  the  aldehyde 
corresponding  with  the  higher  acid  is  formed. 

The  halogens  also  replace  the  hydrogen  of  the  alkyl  residues  of  the  acids, 
giving  products  which  surpass  in  acids  properties  the  acid  from  which  they  are 
formed.1  By  heating  the  acids  homologous  to  acetic  acid  (which  are  very 

1  Besides  referring  to  what  has  been  stated  in  vol.  i,  p.  91  et  seq.,  we  may  here  quote  the  very  clear  considera- 
tion of  this  question  given  by  Professor  Miolati  on  the  Affinity  Constants  of  Acids.  That  diffeient  acids  possess 
different  strengths  follows,  for  example,  from  the  phenomenon  of  displacement  of  one  acid  from  its  salts  by  another 
acid.  When  sulphuric  acid  is  added  to  a  solution  of  sodium  acetate,  the  characteristic  odour  of  acetic  acid  is 
perceived,  since  the  sulphuric  acid  is  transformed  into  sodium  sulphate  and  a  certain  amount  of  acetic  acid 
is  liberated.  This  quantity  and,  in  general,  the  quantity  of  any  acid  displaced  by  a  second  acid,  is  not  equivalent 
to  the  amount  of  the  latter  added,  but  the  two  acids  divide  the  base  according  to  their  strengths,  i.e.  according  to 
their  affinity  constants,  and  also  to  their  quantities.  The  effect  of  the  latter  factor  may  be  eliminated  by  using 
equivalent  quantities  of  the  two  acids  and  of  the  base,  e.g.  by  causing  an  equivalent  of  an  acid  to  act  on  an  equiva- 
lent of  neutral  salt,  so  that  the  distribution  of  the  base  between  the  two  acids  depends  only  on  their  strengths.  A 
chemical  equilibrium  is  then  established  which  is  represented  by  the  equation  : 

(1-  z)[NaX  +  HX']    ^    z[NaX'+HX]. 

In  order  that  this  method  may  give  exact  results,  it  is  of  course  necessary  that  the  bodies  formed  in  the  condi- 
tions of  the  experiment  be  not  eliminated  either  as  gas,  or  solid,  or  complex  molecules,  &c.,  but  that  they  remain 
to  take  part  in  the  equilibrium.  To  determine  this,  Thomson  made  use  of  the  thermal  change  and  Ostwald  the 
changes  of  volume  and  the  indices  of  refraction,  these  methods  leading  to  the  same  results.  In  general,  any 
physical  property  may  be  used  for  the  analysis  of  the  equilibrated  system. 

If,  for  example,  a  is  the  heat-change  observed  on  neutralising  an  equivalent  of  the  first  acid  with  a  base,  b 
the  corresponding  quantity  for  the  second  acid,  and  c  that  observed  on  adding  an  equivalent  of  base  to  an  equivalent 
of  the  mixed  acids,  it  is  evident  that  c  will  be  equal  to  the  thermal  effect  of  the  neutralisation  of  a  certain  frac- 
tion of  an  equivalent  of  the  first  acid  (1  —  x)  plus  the  thermal  effect  of  the  neutralisation  of  the  complementary 
fraction  of  the  second  acid  : 


fa  —  o  a  —  o 

x 
— -r  is  a  measure  of  the  relative  affinities  of  the  two  acids.  The  following  Table  gives  certain  val 

x) 
lined  by  Ostwald,  x  indicating  the  fraction  of  the  molecule  of  base  taken  up  by  the  acid  given  first : 

x 


es  certain  values  of  x  deter- 


HNO, 
HC1 

CCVCOOH 
CCVCOOH 
CCVCOOH 


CHCVCOOH 
CHCVCOOH 

CHCVCOOH 

CH.C1-COOH 
H-COOH 


0-76 
0-74 

o-7i 

0-92 
0-97 


H-COOH:  CH,-COOH 
H-COOH:  C2H5-COOH 

H-COOH  :  C,H,-COOH  I™,™1' 
CH.-COOH  :  C3H,-COOH  (norm  ) 


0-76 
0-79 
0-80 
0-81 
0-53 


AFFINITY    CONSTANTS 


267 


resistant  to  oxidising  agents)  with  concentrated  sulphuric  acid,  C02  is  evolved, 
whilst  acids  with  carboxyl  united  to  a  tertiary  carbon  atom  (e.g.  formic  or 
trimethylacetic  acid)  evolve  CO  and  are  transformed  by  oxidising  agents  into 
hydroxy-acids  :  (CH3)2  :  CH-COOH  gives  (CH3)2 :  C(OH)-COOH. 

Separation  of  the  fatty  acids  from  mixtures  of  them  is  not  always  easy 
and  is  sometimes  effected  by  taking  advantage  of  their  greater  or  less  volatility 
either  in  steam  or  in  a  vacuum,  or  by  precipitating  with  magnesium  acetate 
or  barium  chloride,  since  in  alcoholic  solution  the  higher  acids  are  precipitated 
first.  Use  is  also  made  of  the  fractional  solution  of  the  calcium,  barium,  or 
lead  salts  in  various  solvents  (alcohol,  ether,  &c.),  or  of  fractional  neutralisa- 
tion followed  by  distillation  of  the  acids  not  neutralised.  From  an  aqueous 
mixture  of  formic,  acetic,  butyric,  and  valeric  acids,  the  last  two  can  be 
separated  by  extraction  with  benzene,  from  which  they  can  be  isolated  by 
shaking  with  baryta  water.  Further  separation  can  then  be  effected  as  above. 


If  we  calculate 


1  -  x 
Nitric  acid    . 
Hydrochloric  acid 
Trichloroacetic  acid 
Dichloroacetic  acid 
Monochloroacetic  acid 
Acetic  acid  . 


,  making  nitric  acid  equal  to  100,  we  obtain  the  following  values  : 


100 

98 

80 

33 

7 

1-23 


Formic  acid  .  .         .         .         .3-9 

Propionic  acid  ....      1-04 

Butyric  acid.  ....      0-98 

Glycollic  acid  .         ...      5-0 

Lactic  acid    .  .         .  3-3 


The  acids  arrange  themselves  in  the  same  order  and  almost  with  the  same  coefficients,  if  other  properties  are 
studied.  All  acids  possess,  for  example,  the  property  of  accelerating  certain  hydrolyses,  such  as  that  of  ethyl 
acetate  and  the  inversion  of  cane  sugar  : 


CHj-COOCaH5  -f  H20 
C12H220U 


C2H6-OH  +  CH3-COOH; 
H20  =  2C6H1206. 


In  these  reactions  the  acid  added  acts  only  by  its  presence  (catalysis),  since  at  the  end  of  the  reaction  it 
remains  unchanged.  But,  on  the  addition  of  equivalent  quantities  of  various  acids,  the  reactions  take  place  with 
greater  or  less  velocities,  i.e.  the  same  quantity  of  ethyl  acetate  or  cane-sugar  is  transformed  in  a  longer  or  shorter 
time  according  to  the  acid  added.  The  velocity  of  the  reaction  is  proportional  to  the  affinity  constant  of  the  acid. 
Finally,  the  acids  are  arranged  in  the  same  order  if  we  compare  their  electrical  conductivities.  According  to  the 
theory  of  electrolytic  dissociation,  the  value  of  the  conductivity  depends  on  the  number  of  molecules  of  the  dis- 
solved acid  which  are  dissociated  into  their  ions,  i.e.  into  hydrogen  ions  on  the  one  hand,  and  acid  ions  on  the 
other.  The  possibility  of  furnishing  hydrogen  ions  in  aqueous  solution  would  hence  be  characteristic  of  the  acid  nature 
of  a  substance,  the  amount  of  these  hydrogen  ions  in  unit  volume  being  a  measure  of  the  acidity.  With  equivalent 
solutions  of  different  acids,  the  strong  acids  will  be  those  which  contain,  in  a  given  volume  of  the  solution,  a  large 
number  of  hydrogen  ions,  and  the  weak  ones  those  containing  only  a  small  number  of  such  ions. 

The  condition  of  an  acid  in  solution  may  hence  be  represented  by  the  expression  : 


AH 


A'  +  H' 


and  we  may  term  the  fraction  of  the  equivalent  which  is  dissociated,  the  degree  of  dissociation,  a.  Without 
entering  into  further  details  it  may  be  mentioned  that  <x  is  related,  besides,  to  the  electrical  conductivity,  also  to 
van  't  Hoff's  coefficient  i,  which  expresses  the  divergence  of  the  osmotic  behaviour  of  solutions  of  electrolytes  from 
the  normal  behaviour  (see  vol.  i,  p.  99). 

The  degree  of  dissociation  varies  with  the  concentration  of  the  solution  of  the  acid,  increasing  with  the  dilution 
towards  the  limiting  value  1,  which  corresponds  with  complete  dissociation.  This  increase  is  small  for  strong 
acids,  i.e.  those  which  contain  a  considerable  number  of  hydrogen  ions  even  in  concentrated  solutions,  but  is  much 
greater  for  the  weak  acids. 

v  100  <x 


CHj-COOH 


CHjCl-COOH 


CHCVCOOH 


32 
1024 


32 
1024 


32 
1024 


2-38 
12-66 


19-9 

68-7 


70-2 
99-7 


1 
4-22 


1 
3-53 


1 
1-42 


v  indicates  the  number 
of  litres  of  solution  containing 
1  gnn.-mol.  of  the  acid. 


The  affinity  constants  given  above  hence  depend  on  the  concentration  of  the  acid,  since  with  this  the  concentra- 
tion of  the  hydrogen  ions — on  which  the  value  of  the  acid  properties  of  a  substance  depends — varies.  An  expres- 
sion which  is  independent  of  v  can,  however,  be  found  by  considering  the  equilibrium  :  HA  ^  H*  +  A',  as  if  it 
were  a  gaseous  equilibrium  and  applying  the  law  of  mass  action  to  it.  If  a  is  the  fraction  of  the  equivalent  which 
is  dissociated,  (1  —  <x)  will  be  that  of  the  non-dissociated  part ;  and,  if  v  is  the  number  of  litres  in  which  the 

gramme-equivalent  is  dissolved,  —  will  be  the  so-called  active  mass  of  the  ions,  i.e.  the  number  of  ions  contained  in 


unit  volume,  and 
gives : 


1- 


the  number  of  undissociated  molecules  in  the  same  unit  volume.    The  law  of  mass  action 


where  A,  is  a  constant  depending  solely  on  the  nature  of  the  equilibrium  —  that  is,  on  the  nature  of  the  reacting 


268 


ORGANIC    CHEMISTRY 


k*  Constitution  of  the  Fatty  Acids.  That  these  acids  actually  contain  carboxy 
groups,  — COOH,  is  indicated  by  the  different  ways  in  which  they  are  formed 
and  decomposed,  but  the  most  characteristic  method  of  preparation  consists 
of  the  hydrolysis  of  the  nitriles,  which  are  obtained  from  the  alkyl  iodides 
by  the  action  of  potassium  cyanide  (see  p.  198).  Two  molecules  of  water 
react  with  one  of  nitrile,  giving  ammonia  and  a  higher  acid  : 

CH3-C  i  N  +  2H20  =  NH3  +  CH3-COOH. 

The  nitrogen  of  the  nitrile  being  detached,  the  group  — COOH  must  neces- 
sarily be  formed,  since,  from  reasons  already  mentioned,  the  formation  of  a 
group  — C(OH)3  is  excluded,  as  three  free  hydroxyl  groups  cannot  remain 
united  to  one  carbon  atom  (although  the  corresponding  ortho-ethers  are  known 
and  also  acetals,  see  pp.  182,  205,  and  209). 

O 

FORMIC  ACID,  H-C<^ 

Methanoic  Acid 

It  was  shown  as  early  as  the  seventeenth  century  that  ants  contained  a 
special  acid,  which  was  characterised  later  as  formic  acid,  and  was  separated 
(by  distilling  with  water)  from  the  wood  ant,  the  migratory  ant,  bees  (and  hence 
from  crude  honey),  the  hairs  of  the  nettle,  pine  leaves,  perspiration,  urine,  &c. 

Until  recently,  in  spite  of  numerous  processes  by  which  it  can  be  syn- 
thesised  (e.g.  by  hydrolysing,  with  acid  or  alkali,  hydrocyanic  acid,  which 

bodies — and  on  the  temperature  ;  ft  is  hence  a  measure  of  the  tendency  of  an  acid  to  dissociate  and  is  called  the 
affinity  constant. 

The.  following  Table  gives  the  numbers  referring  to  acetic  acid  and  two  of  its  chloro-dcrivatives  : 


Acetic  acid 

Monochloroacetic  acid 

Dichloroacetic  acid 

V 

A 

100  a 

106fc 

A 

100  a 

105ifc 

A 

100   a 

18** 

16 

6-5 

1-67 

1-79 

56-6 

14-6 

155 

_ 

_ 

32 

9-2 

2-38 

1-82 

77-2 

19-9 

155 

269-8 

70-2 

5170 

64 

12-9 

3-33 

1-79 

103-2 

26-7 

152 

309-9 

80-5 

5200 

128 

18-1 

4-68 

1-79 

136-1 

35-2 

150 

338-4 

88-0 

5040 

256 

25-4 

6-56 

1-80 

174-8 

45-2 

146 

359-2 

93-4 

5160 

512 

34-3 

9-14 

1-80 

219-4 

56-8 

146 

375-4 

97-6 

— 

1024 

49-0 

12-66 

1-77 

265-7 

68-7 

147 

383-8 

99-7 

~ 

In  this  Table  A  denotes  the  molecular  conductivity  corresponding  with  the  dilution  v,  100  a  the  extent  of 
dissociation  in  per  cent.,  and  105  k  the  affinity  constant  multiplied  by  100,000. 

This  affinity  constant  has  a  markedly  constitutive  character ;  it  increases,  for  instance,  if  a  substituent  of 
negative  nature,  such  as  OH,  Cl,  N,  N02,  <fec.,  enters  a  molecule  and  decreases  if  positive  groups  such  as  NH2 
enter.  The  following  examples  may  be  given  : 


Formic  acid.  .... 
Acetic  acid  ..... 
Propionic  acid  .... 

Substitution  with  halogens  and  similar  groups. 
Monochloroacetic  acid    . 
Dichloroacetic 
Trichloroacetic 
Bromoacetic 
Cyanoacetic 
Thiocyanoacetic 
/3-Iodopropionic 

Substitution  by  hydroxyl. 

Glycollic  acid,  OH-CH2-COOH 
Lactic  acid,  CH,-CH(OH)-COOH  . 
i8-Hydroxypropionic  acid,  OH-CH2-CH2-COOH 


.  k=  127-0.10- 
1-8.10- 
1-3.10- 

.     fc  =      155.10 

=    5100.10- 

about  120,000. 10- 

138.10 

370.10 

260.10 

9-0.10 

.     &=     15-0.10- 

14-0.10- 

3-1.10- 


Substilutwn  by  NH2. 

o-Aminopropionic  acid  (alanine),  CH3-CH(XH,)- COOH     .         ..    k  =      9-0. 10~5 

For  further  examples  and  greater  details,  see  E.  Abegg's  "The  Electrolytic  Dissociation  Theory,"  New  York,  1907. 


FORMICACID  269 

may  be  regarded  as  the  nitrile  of  formic  acid),  it  was  prepared  almost  exclu- 
sively by  heating  crystallised  oxalic  acid  with  glycerine  free  from  water  in  a 
reflux  apparatus,  the  formic  acid  thus  obtained  being  distilled.  For  some 
years,  however,  this  acid  has  been  prepared  very  cheaply  by  Goldschmidt's 
process  (Ger.  Pat.  86,419  and  Fr.  Pats.  342,168  and  362,417),  which  consists  in 
first  forming  sodium  formate  by  the  action  of  carbon  monoxide  under  pressure 
[or  of  generator  gas  (vol.  i)]  on  powdered  sodium  hydroxide  or,  better,  by 
dropping  on  to  coke  heated  to  200°  to  220°  a  solution  of  sodium  hydroxide, 
carbonate,  or  sulphate  and  then  passing  in  a  hot  current  of  carbon  monoxide. 
Similarly  from  milk  of  lime  and  coke  at  250°,  calcium  formate  is  obtained. 

From  the  dry  salts,  almost  anhydrous  formic  acid  is  then  obtained  by  treatment  with 
cold  concentrated  sulphuric  acid  to  which  formic  acid,  already  in  the  free  state,  is  initially 
added  (Fr.  Pats.  341,764  and  393,526)  ;  the  pure  acid  was  formerly  obtained,  but  with 
considerable  loss,  by  distilling  its  salts  with  concentrated  sulphuric  acid. 

According  to  Eng.  Pat.  8438  of  1910,  better  results  are  obtained  by  running  35  parts 
of  concentrated  sulphuric  acid  into  200  parts  of  concentrated  formic  acid,  shaking 
meanwhile  ;  to  this  mixture  quantities  of  50  parts  of  the  dry  formate  and  50  parts 
of  concentrated  sulphuric  acid  are  added  alternately.  Good  results  are  also  obtained  by 
decomposing  the  formates  by  means  of  hydrofluoric  acid  (Ger.  Pat.  209,418,  1907). 
See  also  U.S.  Pats.  970,145  of  1910  (W.  H.  Walker)  and  975,151  of  1910,  in  which  the  decom- 
position of  formates  by  phosphoric  acid  below  145°  is  proposed. 

This  new  process  makes  it  advantageous  to  prepare  oxalates  from  formates,  whilst  the 
latter  were  previously  obtained  from  the  oxalates.  According  to  Fr.  Pat.  413,947  of  1910, 
the  formate  is  run  into  an  evacuated  vessel  maintained  at  550°  to  600°  by  means  of  a 
metal  bath  ;  if  the  temperature  of  the  mass  introduced  is  kept  for  half  an  hour  at  above 
400°,  the  formate  is  transformed  quantitatively  into  pulverulent  oxalate  (150  kilos  for 
every  square  metre  of  heated  surface). 

Almost  anhydrous  formic  acid  is  obtained  by  distillation  over  anhydrous  copper 
sulphate  (Ger.  Pat.  230,171,  1909). 

Pure  formic  acid  is  a  colourless  liquid  with  a  pungent  odour,  sp.  gr.  1-223 
at  0°,  b.pt.  99°  ;  it  solidifies  on  cooling  and  then  melts  at  8' 6°.  If  poured 
on  the  hand  it  produces  very  painful  blisters.  In  aqueous  solution,  a  mixture 
of  constant  composition  distils,  as  is  the  case  with  hydrochloric  acid  (vol.  i, 
p.  158)  ;  at  ordinary  pressure  this  mixture  contains  77-5  per  cent,  of  acid 
and  boils  at  107°.  Unlike  its  homologues  (acetic,  butyric  acid,  &c.),  it  is 
readily  oxidised  by  permanganate,  &c.,  forming  C02  and  H20  ;  hence  its 
great  reducing  power,  owing  to  which,  in  the  hot,  it  separates  silver  from 
silver  salts,  and  first  mercurous  chloride  and  then  mercury  from  mercuric 
chloride  solutions.  Thus  it  behaves  as  an  aldehyde,  the  characteristic  group 

^ 
of  which,  —  Cf      it  does  indeed  contain.     When  heated  in  a  sealed  tube  at 

\H 

160°  or  treated  with  concentrated  sulphuric  acid,  it  decomposes  readily  and 
completely  into  CO  +  H20.  Finely  divided  rhodium,  ruthenium,  or  iridium 
(but  not  platinum  or  palladium)  decomposes  it  completely  into  C02  and  H2. 
Various  bacteria  produce  the  same  change. 

Its  price  has  now  fallen  to  below  72s.  per  quintal  (85  per  cent,  concentration)  and 
owing  to  its  low  molecular  weight  it  can  compete  with  acetic  acid,  a  less  weight  being 
required  to  produce  a  given  acidity.  On  account  of  its  acid  character  and  its  reducing  and 
antiseptic  properties,  it  is  used  to  increase  the  yield  of  alcoholic  fermentations,  in  the 
dyeing  and  printing  of  textiles  where  it  can  replace  lactic  acid  (not  always  advantageously), 
in  the  bichromate  mordanting  of  wool,  and  also  acetic  acid  (in  France  the  consump- 
tion of  acetic  acid  has  diminished  from  this  reason).  Its  use  in  tanning  has  also  been 


Its  strength  is  determined  by  means  of  standard  sodium  hydroxide  solutions,  using 


270  ORGANIC    CHEMISTRY 

phenolphthalein  as  indicator,  but  when  other  acids  are  also  present  it  is  titrated  with 
permanganate  in  acid  solution  or  chromic  acid  in  alkaline  solution.  The  CO  evolved 
when  it  is  treated  with  concentrated  sulphuric  acid  can  also  be  measured.  When  other 
organic  acids  are  present,  the  dilute  mixture  is  treated  with  mercuric  acetate  at  the  boiling 
temperature,  the  mercurous  acetate  which  separates  being  filtered  off  in  the  cold,  dis- 
solved in  nitric  acid,  the  calomel  precipitated  with  sodium  chloride  then  being  weighed. 
Or  dilute  formic  acid  solution  (0-2  grm.  per  litre)  may  be  treated  with  about  15  times 
the  weight  of  mercuric  chloride  (calculated  on  the  acid)  dissolved  in  200  c.c.  of  hot  water, 
the  liquid  being  well  shaken  and  the  mercurous  chloride  precipitate,  after  treatment 
with  caustic  soda,  collected  on  a  Gooch  crucible,  washed,  dried,  and  weighed  ;  multi- 
plication of  the  weight  by  0-097726  gives  the  weight  of  formic  acid  (Franzen  and  Greve, 
1909).  Formic  acid  may  be  detected,  even  in  presence  of  aldehydes,  acetic  acid,  and 
methyl  alcohol,  by  means  of  sodium  bisulphite  solution,  which  gives  a  reddish  yellow 
coloration. 

Presence  of  hydrochloric  acid  as  impurity  may  be  detected  by  dilution  (1  :  20)  and 
addition  of  silver  nitrate  :  oxalic  acid  may  be  detected  by  saturating  with  ammonia 
and  adding  calcium  chloride.  If  no  acr.olein  or  allyl  alcohol  is  present,  it  does  not 
give  a  pungent  odour  after  neutralisation  with  caustic  soda. 

The  commercial  aqueous  acid  costs  24s.  per  quintal  for  a  25  per  cent,  solution  (sp.  gr. 
1-064)  ;  44*.  for  50  per  cent,  solution  (1-124)  ;  62s.  for  75  per  cent,  solution  (1-170)  ; 
72s.  for  85  per  cent.  (1-190)  ;  and  108s.  for  the  96  to  98  per  cent,  acid  (1-217)  The 
chemically  pure  acid  costs  more  than  double  these  prices. 

SALTS  OF  FORMIC  ACID  are  called  formates  and  are  generally  soluble  in  water 
and  crystallisable  ;  almost  all  the  characteristic  properties  and  reactions  of  formic  acid 
(reduction,  &c.)  are  shown  also  by  its  salts.  With  concentrated  sulphuric  acid  in  the 
hot,  they  yield  carbon  monoxide.  Formates  are  obtained  by  the  action  of  carbon  monoxide 
on  metallic  hydroxides  in  the  hot  and  under  pressure  (see  also  Fr.  Pat.  382,001, 1907,  and 
U.S.  Pat.  875,055,  1907).  When  heated  at  200°  to  400°,  the  formates  yield  carbonates 
and  oxalates  and  chemically  pure  hydrogen.  Potassium  formate,  H-COOK,  forms  deli- 
quescent crystals.  Sodium  formate,  H-COONa,  crystallises  well  with  3H20  at  0°  or  with 
2H20  at  17°  and  melts  at  253°  (the  pure  salt  costs  3s.  Id.  per  kilo,  and  the  commercial 
salt,  Is.  Id.).  Ammonium  formate,  H-COONH4,  melts  at  115°  and  at  a  higher  tempera- 
ture decomposes  into  formamide,  water,  and  a  little  hydrocyanic  acid  ;  since,  in  its 
decomposition  when  heated,  it  gives  nitrogen  and  carbon  compounds,  it  is  used  to  harden 
and  cement  steel  (the  pure  salt  costs  as  much  as  9s.  6d.  per  kilo).  The  magnesium,  barium, 
and  calcium  salts  are  also  soluble  in  water  ;  the  last  costs  4s.  (pure)  or  2s.  (impure)  per 
kilo.  Lead  formate  (H-COO)2Pb,  dissolves  only  slightly  in  cold  water,  but  readily  in 
hot,  and  hence  serves  well  to  separate  formic  from  other  acids.  Zinc  formate,  (H-  COO)2Zn, 
is  insoluble  in  absolute  alcohol  and  hence  also  serves  to  separate  formic  acid  from  others. 
Acid  formates,  such  as  H-COONa  +  H-COOH,  are  also  known. 

ACETIC  ACID,  CH3  •  C^ 

X)H 
Ethanoic  Acid 

Although  its  constitution  was  first  determined  by  Berzelius  in  1814, 
acetic  acid  has  been  known  from  the  earliest  times,  since  it  forms  easily  in 
wine  (vinegar),  in  many  vegetable  juices,  in  sour  milk,  in  perspiration,  in 
excreta,  &c.  In  1700  Stahl  obtained  it  in  a  concentrated  form  by  freezing 
the  dilute  acetic  acid,  then  neutralising  with  alkali  and  distilling  the  acetic 
acid  after  addition  of  sulphuric  acid.  It  is  often  formed  in  the  oxidation 
and  combustion  of  many  organic  substances;  of  the  various  synthetic 
processes  for  its  preparation,  that  of  Kolbe  (1843)  may  be  mentioned  : 
perchlorethane,  in  presence  of  water  and  under  the  influence  of  light, 
gives  trichloroacetic  acid  :  CC13-CC13  +  2H20  =  3HC1  +  CC13-COOH,  and 
this  is  reduced  by  nascent  hydrogen  to  acetic  acid.  Commercially  it  is 
obtained  irom  ethyl  alcohol  and,  especially,  by  the  dry  distillation  of  wood 
(see  later). 


ACETIC    ACID 


271 


PROPERTIES.  When  pure,  acetic  acid  forms  a  colourless  liquid  of 
sp.  gr.  1-0553  at  15°  and  a  specific  heat  of  0-522  between  26°  and  96°  ;  it 
solidifies  at  +16-7°  in  white  crystals  (hence  the  name  glacial  acetic  acid, 
which  is  very  hygroscopic  and  has  the  sp.  gr.  1-08  at  0°)  and  boils  at  118°, 
but  evaporates  considerably  below  this  temperature  owing  to  its  high  vapour 
pressure.  It  is  soluble  in  all  proportions  in  water,  alcohol,  and  ether.  Its 
vapours  burn  with  a  bluish  flame.  It  dissolves  many  organic  and  several 
inorganic  substances  (P,  S,  HC1,  &c.).  When  pure  concentrated  acetic  acid 
is  mixed  with  water,  heating  and  contraction  take  place  ;  the  specific  gravity 
increases  on  dilution  of  the  pure  acid  and  reaches  a  maximum  (1-0748)  with 
77  per  cent,  of  the  acid  (corresponding  with  the  hydrate,  C2H402  +  H20), 
afterwards  diminishing  gradually  as  the  dilution  increases.1  Hence  when 
the  density  of  an  acetic  acid  solution  is  given  it  must  be  indicated  whether 
it  refers  to  solutions  containing  more  or  less  than  77  per  cent,  of  the  acid. 
It  cannot,  however,  be  assumed  that  a  chemical  compound,  C2H402  +  H20, 
actually  corresponds  with  the  maximum  density  of  the  aqueous  solution, 
since  at  other  temperatures  the  maximum  densities  correspond  with 
different  compositions  ;  thus,  at  0°  the  maximum  density  is  obtained 
with  80  per  cent,  of  acetic  acid  and  at  40°  with  75  per  cent.  The  strength 
of  acetic  acid  generally  refers  to  the  weight  and  not  to  the  volume  of  the 
acid. 

The  lowest  freezing-point  is  obtained  (—27°)  with  the  aqueous  solution 
containing  60  per  cent,  of  the  acid  (corresponding  with  a  hydrate, 
C2H402  +  2H20),  whilst  solutions  with  84  per  cent,  and  with  10  per  cent. 
freeze  at  —3-2°.  Unlike  those  of  formic  acid  and  of  mineral  acids,  aqueous 
solutions  of  acetic  acid  yield  no  distillate  of  constant  composition. 

The  vapour  density  of  the  acid  indicates  a  mixture  oE  simple  and  double 
molecules  below  250°,  and  simple  molecules  alone  above  this  temperature. 
With  hydrogen  bromide  it  forms  reddish  crystalline  additive  products,  e.g. 
CH3-COOH,  Br2,  4HBr.  Certain  bacteria  decompose  it  into  CH4  +  C02. 

In  contact  with  red-hot  pumice,  acetic  acid  vapour  only  partially  decom 
poses,  giving  acetone,  C02,  and  a  little  phenol  and  benzene.     Chlorine  replaces 

1  Oudcman's  Table  :  specific  gravity  and  concentration  of  acetic  acid  at  15". 


Specific 
gravity 

Per  cent, 
of  acid 
by  weight 

Specific 
gravity 

Per  cent, 
of  acid 
by  weight 

Specific 
gravity 

Per  cent, 
of  acid 
by  weight 

Specific 
gravity 

Per  cent, 
of  acid 
by  weight 

Specific 
gravity 

Per  cent, 
of  acid 
by  weight 

1-0007 

1 

1-0185 

13 

1-0412 

30 

1-0646 

54 

1-0748 

78 

1-0014 

1-5 

1-0192 

13-5 

1-0424 

31 

1-0653 

55  ' 

1-0748 

79 

1-0022 

2 

1-0200 

14 

1-0436 

32 

1-0660 

56 

1-0748 

80 

1-0030 

2-5 

1-0207 

14-5 

1-0447 

33 

1-0666 

57 

1-0747 

81 

1-0037 

3 

1-0214 

15 

1-0459 

34 

1-0673 

58 

1-0746 

82 

1-0045 

3-5 

1-0221 

15-5 

1-0470 

35 

1-0679 

59 

1-0744 

83 

1-0052 

4 

1-0228 

16 

1-0481 

36 

1-0685 

60 

1-0742 

84 

1-0060 

4-5 

1-0235 

16-5 

1-0492 

37 

1-0691 

61 

1-0739 

85 

1-0067 

5 

1-0242 

17 

1-0502 

38 

1-0697 

62 

1-0736 

86 

1-0075 

5-5 

1-0249 

17-5 

1-0513 

39 

1-0702 

63 

1-0731 

87 

1-0083 

6 

1-0256 

18 

1-0523 

40 

1  0707 

64 

1-0726 

88 

1-0090 

6-5 

1-0263 

18-5 

1-0533 

41 

1-0712 

65 

1-0720 

89 

1-0098 

7 

1-0270 

19 

1-0543 

42 

1-0717    ' 

66 

1-0713 

90 

1-0105 

7-5 

1-0277 

19-5 

1-0552 

43 

1-0721 

67 

1-0705 

91 

1-0113 

8 

1-0284 

20 

1-0562 

44 

1-0725 

68 

1-0696 

92 

1-0120 

8-5 

1-0293 

21 

1-0571 

45 

1-0729 

69 

1-0686 

93 

1-0127 

9 

1-0311 

22 

1-0580 

46 

1-0733 

70 

1-0674 

94 

1-0135 

9-5 

1-0324 

23 

1-0589 

47 

1  0737 

71 

1-0660 

95 

1-0142 

10 

1-0337 

24 

1-0598 

48 

1-0740 

72 

1-0644 

96 

1-0150 

10-5 

1-0350 

25 

1-0607 

49 

1-0742 

73 

1-0625 

97 

1-0157 

11 

1-0363 

26 

1-0615 

50 

1-0744 

74 

1-0604 

98 

1-0164 

11-5 

1-0375 

27 

1-0623 

51 

1-0746 

75 

1-0580 

99 

1-0171 

12 

1-0388 

28 

1-0631 

52 

1-0747 

76 

1-0553 

100 

1-0178 

12-5 

1-0400 

29 

1-0638 

53 

1-0748 

77 

~ 

272 


ORGANIC    CHEMISTRY 


first  one  atom  and  then  three  atoms  of  hydrogen  in  the  CH3  group  ;  bromine 
acts  similarly  at  120°,  but  iodine  does  not  react.  It  resists  in  the  cold  the 
action  of  chromic  acid  or  permanganate,  but  when  heated  with  the  latter 
forms  C02  ;  it  is  very  resistant  to  the  action  of  reducing  agents  (sodium 
amalgam,  &c.). 

TESTS  FOR  ACETIC  ACID.  Better  than  by  means  of  the  specific  gravity,  the 
strength  can  be  determined  by  means  of  a  normal  caustic  soda  solution  (1  c.c.  =  0-06004 

grm.  acetic  acid),  a  weighed  quantity  being 
titrated  and  phenolphthalein  used  as  indi- 
cator. When  it  contains  mora  than  2  per 
cent,  of  water,  it  will  no  longer  dissolve 
cedar -wood  or  turpentine  oil.  Metallic  im- 
purities are  detected  by  diluting  10  c.c.  of  the 
acid  to  100  c.c.,  neutralising  with  ammonia 
and  adding  ammonium  sulphide  and  am- 
monium oxalate  ;  if  the  acid  is  pure,  no 
alteration  or  precipitation  should  occur.  If 
there  is  no  sulphuric  acid  present,  dilution 
with  ten  volumes  of  water  and  treatment  with  BaCl2  in  the  hot  will  give  no  precipi- 
tate even  after  an  hour's  rest.  In  absence  of  hydrochloric  acid,  addition  of  nitric 
acid  and  silver  nitrate  gives  no  turbidity  in  the  diluted  acid.  If  no  empyreumatic 
products  are  present,  5  c.c.  of  the  acid  diluted  with  15  c.c.  of  water  will  not  decolorise 
5  c.c.  of  an  N/100-solution  of  permanganate  even  in  fifteen  minutes.  For  the  detection 
of  other  organic  acids  and  for  other  tests,  see  Notes  on  pp.  279  and  284. 

MANUFACTURE  OF  ACETIC  ACID.  The  most  important  prime  material  for  the 
manufacture  of  crude  acetic  acid  is  wood,  alcohol  (from  cereals  and  wine)  being  only 
rarely  used. 


FIG.  229. 


FIG.  230. 

Dry  Distillation  of  Wood.  It  has  been  already  mentioned  (see  p.  36)  that  Lebon  in 
1799  patented  a' process  of  dry  distillation  of  wood  for  producing  illuminating  gas  and 
on  p.  106,  in  dealing  with  the  manufacture  of  methyl  alcohol — also  a  product  of  the  dry 
distillation  of  wood — the  phases  and  crude  products  of  this  distillation  out  of  contact  of 
air  were  described.  A  description  will  now  be  given  of  the  apparatus  used  in  this  industry. 
It  is  not  necessary  to  consider  the  primitive  furnaces  formerly  used,  which  gave  a  minimal 
yield  and  a  slow  and  incomplete  carbonisation,  or  thesvertical  retorts  used  in  the  early 
days  of  this  industry,  although  these  are  again  in  use  nowadays,  but  in  a  far  more  rational 
manner.  These  first  vertical  retorts  were  followed  by  horizontal  ones,  which  are  still 
used  in  many  factories. 

These  are  formed  of  sheet  iron  (10  to  12  mm.  thick)  and  are  about  1  metre  in  diameter 
and  3  metres  in  length  ;  they  are  arranged  in  pairs  in  furnaces  (Fig.  229)  with  suitable 
flues  for  the  hot  gases,  and  they  can  be  charged  and  discharged  by  means  of  hinges  at 


DISTILLATION    OF    WOOD 


273 


FIG.  231. 


the  back,  although  not  very  conveniently.  On  this  account  and  also  in  order  to  obtain 
continuous  working  and  hence  more  efficient  utilisation  of  the  heat  of  the  furnaces,  use  is 
again  being  largely  made  of  vertical  retorts  which  can  be  removed  from  the  furnace  at 
the  end  of  the  operation,  to  be  replaced  immediately  by  other  retorts  already  charged. 
In  Fig.  230,  on  the  left,  is  seen  the  arrangement  of  a  battery  of  these  retorts,  with  a  trolley 

for  raising  and  transporting  the 
charged  retorts,  which  are  then 
emptied  into  the  charcoal  stove 
by  means  of  the  tipping  trolley, 
K.  The  right-hand  side  of  the 
figure  shows  in  detail  the  upper 
part  of  a  retort  charged  with 
wood.  The  capacity  of  each 
retort  is  about  4  cu.  metres  or 
1500  kilos  of  wood;  the  smaller 
pieces  are  placed  at  the  bottom, 
the  medium-sized  ones  next,  and 
the  largest  ones  at  the  top.  In 
order  that  the  retorts  may  not 
be  worn  out  too  rapidly  by  the 
external  heat,  they  are  smeared 
with  a  very  thin  layer  of  earth 
made  into  a  paste  with  water 
and  applied  with  a  brush.  Every 
charge  of  1500  kilos  requires 
•about  1000  kilos  of  coal  for  heating  and  distilling.  If  leaks  are  detected  during  the 
heating,  they  are  closed  with  clay,  and  it  is  for  this  purpose  that  the  retorts  project 
15  to  20  cm.  beyond  the  furnace. 

Although  this  arrangement  is  still  largely  used,  it  necessitates  a  considerable  amount 
of  manual  labour  and  lifting,  so  that  it  has  been  proposed  to  incline  the  retorts  as  in  gas- 
manufacture,  and  to  furnish  them  with  apertures  at  the  top  for  charging  and  others  at 
the  bottom  for  automatically  discharging  them.  Fig.  231  shows  the  section  of  a  battery 
of  these  retorts  (A)  of  the  Mathieu  type,  8  giving  the  cross-section  of  a  retort.  The  wood 
is  charged  automatically  from  the  running  buckets,  c,  suspended  at  g.  At  the  end  of 
the  operation  the  charcoal  is  discharged  below 
into  the  vessel,  P,  which  is  provided  with  a  cover 
to  prevent  the  hot  charcoal  from  igniting  in  the 
air.  The  vapours  from  the  distillation  pass  into 
the  tube,  H,  which  conducts  them  into  a  coil 
cooled  by  the  water  in  T  and  then  into  the  barrel, 
J,  where  the  tar  and  the  pyroligneous  acid  sepa- 
rate ;  the  gas,  which  does  not  condense  but  is 
still  partly  combustible,  is  washed  and  passes 
through  the  pipe,  k,  to  be  burnt  under  the  furnace  - 
hearth,  D  ;  there  is  no  danger  of  explosion  since, 
if  there  is  any  air  in  the  retorts,  it  cannot  com- 
municate with  the  hearth,  the  barrel,  J,  serving 
as  a  water-seal. 

Of  late  years,  use  has  also  been  made  of 
vertical  retorts  (Fig.  232)  with  an  upper  orifice; 
o,  for  charging,  and  a  lower  one,  e,  for  discharging 

(see  Ger.  Pat.  192,295,  November  15,  1906).  From  the  hearth,  b,  the  hot  gases  pass 
to  the  flues  surrounding  the  retort  and  thence  at  8  to  the  shaft ;  the  gases  and  vapours 
from  the  wood  issue  from  the  tube,  n,  and  are  partially  condensed  in  the  refrigerator, 
m.  At  the  end  of  the  distillation,  the  orifice,  e,  is  opened  and  the  charcoal  discharged 
into  the  covered  waggon,  k,  and  conveyed  to  the  store,  whilst  the  retort,  while  still  hot,  is 
filled  with  a  new  charge  of  wood. 

If  the  retorts  are  heated,  not  with  coal,  but  by  the  gases  produced  with  hot  air  in  a 
regenerator  furnace  (see  vol.  i,  pp.  367  and  501),  one-third  of  the  fuel  is  saved.     Every 
n  18 


FIG.  232. 


274 


ORGANIC    CHEMISTRY 


distillation  lasts  from  6  to  8  hours.  The  wood  to  be  distilled  is  either  stacked  in 
piles  for  one  or  two  years  or  dried  in  a  warm  chamber,  which  is  placed  near  the  retort 
furnaces  and  utilises  hot  gases  which  would  otherwise  be  wasted.  It  is  then  cut  into 
lengths,  barked  by  hand  or  machinery,  and  divided  longitudinally  by  circular  saws  or 
hatchets.  The  yield  of  acetic  acid  and  by-products  varies  widely  with  the  kind  of 
wood.  Preference  is  usually  given  to  hard  woods  like  oak,  hornbeam,  and  beech  ; 
of  less  value  are  white  woods,  with  the  exception  of  lime,  which  gives  good  results  ; 

the  wood  of  trees  18  or  20 
years  old,  grown  in  a  dry, 
poor  soil  and  cut  in  winter, 
is  more  suitable  than  young 
wood  or  wood  grown  on 
plains  in  a  moist  or  fertile 
soil  and  cut  at  other 
seasons  of  the  year.1 

UTILISATION  OF  THE 
SAWDUST.  Many 'attempts 
have  been  made,  not  always 
ft,    successfully,   to    utilise    the 
'      various  forms  of    wood  re- 
fuse, especially  the  sawdust. 
But  this  presents  consider- 
able difficulty  owing  to  the 
excessive  moisture,  the  large 
volume,  the    abundance    of 
resins      which      char     and 
FIG.  233.  form  incrustations,  and  the 

low   thermal    conductivity, 
which  prevents  the  heat  from  reaching  the  middle  of  the  retort. 

1  The  yields  obtained  from  100  kilos  of  various  kinds  of  wood,  barked  and  subjected  to  rapid  (R,  about  3  hours) 
or  slow  distillation  (L,  more  than  6  hours)  are  given  below  : 


Aqueous  acid  distillate 

Kind  of  Wood 

Tar 

Strength 

Equal  to 

Dry 
charcoal 

Gas 

» 

Total 

of  acetic 
acid 

puro 
acetic 
acid 

Kilos 

Kilos 

Per  cent. 

Kilos 

Kilos 

Kilos 

Breaking  buckthorn  (Rhamnus  frangula)  branches  L 

7-58 

45-21 

13-38 

6-05 

26-50 

20-71 

Do.             Do.           ...                         R 

5-15 

40-23 

11-16 

4-49 

22-53 

32-09 

Hornbeam  (Carpinus  betulus)  trunk           .         .    L 

4-75 

47-65 

13-50 

6-43 

25-37 

22-23 

Do.            Do  R 

5-55 

42-97 

12-18 

5-23 

20-47 

31-01 

Alder  (Alnus  glutinosa)  trunk           .         .         .    L 

6-39 

44-14 

13-08 

5-77 

31-56 

17-91 

Do.            Do  R 

7-06 

40-70 

10-14 

4-13 

21-11 

31-13 

Aspen  (Populus  tremula)  trunk         .         .             L 

6-90 

40-54 

12-57 

5-10 

25-47 

27-09 

Do.            Do  R 

6-91 

39-45 

11-04 

4-36 

21-33 

32-31 

Birch  (Betvla  alba)  trunk      ';•••.         .         .    L 

5-46 

45-59 

12-36 

5-63 

29-24 

19-17 

Do.            Do  R 

3-24 

39-74 

11-16 

4-43 

21-46 

35-56 

Beech  (Fagus  sylvatica)  trunk  .          .         .         .    L 

5-85 

39-45 

11-37 

5-21 

26-69 

21-66 

Do.            Do.          ...                        R 

4-90 

45-08 

9-78 

3-86 

21-90 

33-75 

Oak  (Quercus  robur)        ....             L 

3-70 

44-45 

9-18 

4-08 

34-68 

17-17 

Do.            Do  R 

3-20 

42-04 

8-19 

3-44 

27-73 

27-03 

Austrian  Pine  (Pinus  laricio)  trunk           .          .    L 

9-30 

42-31 

6-36 

2-69 

26-74 

21-65 

Do.            Do  R 

5-58 

38-19 

5-40 

2-06 

24-06 

32-17 

Pine  (Pinus  abies)  trunk          .         .         .         .    L 

5-93 

40-99 

5-61 

2-30 

25-55 

28-11 

Do.            Do  R 

6-20 

40-15 

4-44 

1-78 

23-35 

32-80 

A  detailed  study  of  the  distillation  of  chestnut  wood  was  made  by  G.  Borghesani  in  1910. 

The  bark  and  branches  always  give  a  smaller  yield. 

The  plant  of  a  small  factory  in  Italy  for  distilling  100  quintals  of  wood  per  day  would  require  a  capital  outlay 
of  about  £5600  (excluding  the  factory)  for  the  purchase  of  a  horizontal  retort  or  cylinder  taking  four  trolley- 
loads  of  25  quintals  each,  a  quenching  drum,  boilers,  pumps,  engines,  copper  coils,  evaporating  and  rectifying 
apparatus,  apparatus  for  the  production  of  calcium  acetate,  methyl  alcohol,  acetone  and  tar,  allowing  10  per 
cent,  for  Customs  duty  and  10  per  cent,  for  erecting  the  plant  and  various  other  expenses. 


UTILISATION    OF    SAWDUST 


275 


The  problem  has  not  yet  been  definitely  solved,  but  the  forms  of  apparatus  which  up 
to  the  present  have  given  the  best  results  are  that  of  Halliday  (1851),  shown  in  Fig.  233, 
and  the  more  recent  one  shown  in  Fig.  234.  Above  the  Halliday  furnace  the  moist 
material  (sawdust,  exhausted  dyewoods,  &c.)  is  dried  slowly  in  a  and  slowly  descends 

a  vertical  screw  moved  by  the  cog-wheel, 
b,  into  the  horizontal  iron  cylinder  ;  there 
the  mass  is  transported  slowly  to  the 
opposite  end  by  a  horizontal  screw  and 
falls  in  a  charred  condition  through  the 
channel,  d,  into  a  water-tank,  where  it  is 
extinguished.  The  vapours  and  gases  from 
the  distillation  issue  at  e  and  pass  to  the 
condensing  apparatus.  The  cylinder  is 
heated  by  the  hot  fumes  from  the  fire,  g, 
several  cylinders  being  heated  at  the  same 
time  in  one  furnace.  In  the  other  type 
of  furnace  (Fig.  234)  the  process  is  also 
continous,  the  wood-waste  being  dried  at 
a,  and  falling  down  outside  a  column 
formed  of  a  number  of  superposed  conical 
rings  which  occupy  almost  the  whole  of 
the  interior  of  the  cylinder,  b  ;  the  gases 
from  the  distillation  pass  inside  this 
column,  the  more  volatile  ones  issuing 
from  the  tube,  c,  and  the  less  volatile  ones 
from  the  lower  tube,  e,  all  being  passed 
along  the  pipe,  S,  to  the  refrigerator.  The 
charred  wood  is  discharged  at  d. 

F.  H.  Meyer  obtains  better  results  by 
using  two  large  retorts  or  cylinders  set 
horizontally  in  a  furnace.  Into  these 
cylinders  run  trolleys  carrying  metal  plates 
The  fire  is  started  and  the  first  cylinder 
heated  and  distilled  rapidly,  the  hot  fumes  then  going  to  heat  the  second  cylinder  and 
so  dry  the  sawdust,  which  is  made  ready  for  distillation,  whilst  the  first  cylinder  is  dis- 
charged and  again  charged  with  fresh  sawdust.  In  Russia  and  America,  large  quantities 
of  resinous  woods  are  distilled,  and  these  yield  considerable  amounts  of  resins  and  oils  (of 
pine,  turpentine,  &c.)  if  superheated  steam  is  used. 
In  1905  the  suggestion  was  made  to  distil  wood 
in  retorts  in  a  current  of  chlorine  so  as  to  obtain 
acetic  and  hydrochloric  (70  per  cent,  of  the 
chlorine  used)  acids  at  the  same  time.  Further, 
Larsen  constructed  rotating  furnaces  for  the  dis- 
tillation of  wood,  and  in  1904  the  attempt  was 
again  made  in  Sweden  to  distil  resinous  woods 
with  superheated  steam  so  as  to  obtain  an  in- 
creased yield  of  turpentine. 

The  liquid  products  from  the  dry  distillation 
of  wood  are  condensed  in  cooling  coils  and  col- 
lected in  large  wooden  vats.  They  consist  mostly 
of  an  aqueous  solution  of  acetic  acid  (about  5  to  8 
per  cent.),  methyl  alcohol  (about  1  percent.),  and 


FIG.  234. 


with  the  sawdust  spread  out  in  thin  layers. 


FIG.  235. 


acetone  (nearly  0-1  per  cent.),  and  of  small  quantities  of  other  acids  (formic,  propionic, 
butyric,  valeric,  caproic,  &c. ).  On  this  liquid  floats  part  of  the  tar,  the  rest  of  which  collects 
at  the  bottom  ;  the  tar  can  be  easily  separated  by  decantation  or  by  means  of  a  centrifuge — 
such  as  is  used  for  the  separation  of  cream  from  milk— a  low  temperature  and  sometimes 
addition  of  a  little  tannin  being  used  to  facilitate  the  separation.1  The  aqueous  solution, 

1  The  tar  is  washed  with  water  and  heated  to  recover  the  acetic  acid  it  contains,  the  tar  thus  obtained  free 
from  acid  being  used  in  the  manufacture  of  rubber  and  of  electric  wires,  its  price  being  8s.  to  10«.  per  quintal. 


276 


ORGANIC    CHEMISTRY 


which  is  brown,  and  has  an  unpleasant  odour  owing  to  the  presence  of  empyreumatic 
products,  can  be  treated  in  various  ways  according  as  crude  acid  or  a  purer  acid  is  required. 
In  the  first  case  it  is  filtered  through  wood-charcoal,  left  to  stand  for  a  week  to  see  if 
any  further  tar  separates,  and  then  distilled,  in  quantities  of  800  litres,  in  a  large  copper 
still  which  has  a  capacity  of  1200  litres  (Fig.  235),  is  heated  by  direct-fire  heat  and  is 
surmounted  by  three  lenticular  rectifying  plates  (Pistorius),  the  outer  surfaces  of  these 
being  cooled  by  running  water.  All  the  methyl  alcohol  and  acetone  first  distil  at  60°  to 
70°,  their  condensation  being  effected  in  the  cooling  coil  ;  when  no  more  alcoholic  liquid 
passes  over  (that  is,  when  the  density  at  15°  reaches  the  value  1-000)  (about  100  litres), 
the  temperature  is  raised  to  95°  and  the  acetic  acid,  which  then  begins  to  distil,  is  collected 
separately.  To  the  200  litres  of  aqueous,  tarry  matter  remaining  in  the  still,  a  further 
quantity  of  700  litres  of  the  crude  pyroligneous  acid  is  added,  the  alcoholic  and  acetic 
acid  portions  being  again  collected  separately  and  the  distillation  continued  until  oily 
or  tarry  drops  appear  in  the  distillate  ;  a  third  charge  is  then  added  and  the  distillation 
carried  out  in  the  same  way,  the  200  to  300  litres  of  tarry  matter  left  being  then  run  off 
and  a  fresh  distillation  of  three  successive  charges  commenced. 

•  The  acetic  acid  thus  obtained  bears  the  name  of  pyroligneous  acid  and  has  a  density 
of  1-013  ;   it  contains  about  5  per  cent."  of  the  pure  acid,  has  an  intense  empyreumatic 


FIG.  236. 

odour  and  rapidly  turns  brown  in  the  air.  None  of  the  attempts  made  to  purify  and 
deodorise  this  product  have  given  satisfactory  results,  and  it  is  preferably  purified  in- 
directly by  adding  milk  of  lime  until  the  reaction  is  alkaline,  stirring  well  and  allowing 
to  stand  until  the  tarry  impurities  collect  on  the  surface  or  at  the  bottom  and  are  hence 
easily  separated  by  skimming  and  decantation. 

The  solution  of  calcium  acetate  is  then  evaporated  to  half  its  volume  and 
treated  with  about  1  per  cent,  of  hydrochloric  acid  to  separate  the  final  traces  of  tarry 
substances  remaining  dissolved.  The  liquid  is  then  evaporated  in  shallow  cast-iron 
pans  heated  with  the  hot  gases  from  the  wood-distillation  furnaces  (evaporation  in  a 
vacuum  saves  fuel  and  gives  a  better  yield).  The  pasty  calcium  acetate  which  remains 
is  heated  to  about  250°  to  decompose  the  tarry  matters  present,  the  heating  being  con- 
tinued until  a  small  portion  of  the  mass  gives  a  solution  no  longer  showing  a  brown  colour. 
For  this,  roasting  continuous  furnaces,  similar  to  Hasenclever's  apparatus  for  the  prepara- 
tion of  calcium  hypochlorite  (see  vol.  i,  p.  494),  are  used,  a  current  of  air  at  about  250° 
being  passed  in  at  the  bottom  of  the  apparatus  in  place  of  the  chlorine.  This  procedure 
yields  a  commercial  product  containing  80  to  82  per  cent,  of  pure  calcium  acetate. 
According  to  U.S.  Pat.  927,135,  1909,  white  calcium  acetate  of  high  grade  (86  to  92  per 
cent.)  is  obtained  if  the  concentration  and  drying  are  carried  out  in  a  vacuum. 

The  separation  of  the  various  components  of  the  crude  pyroligneous  acid  and  the 
simultaneous  preparation  of  calcium  acetate  may  also  be  effected  by  a  process  in  which 


SEPARATION    OFTHE    ACETIC    ACID      277 

three  boilers  are  employed  (Fig.  236).  The  crude,  decanted  pyroligneous  acid  is  pumped 
into  the  large  vat,  A,  from  which  it  passes  to  the  copper  boiler,  J?x  (3000  to  5000  litres), 
where  it  is  boiled  by  means  of  steam-pipes  (steam  entering  at  V  under  3  to  4  atmos. 
pressure  and  the  condensed  steam  issuing  at  S).  The  vapours  of  acetic  acid,  methyl 
alcohol  and  acetone  are  passed  through  the  tube,  t,  to  the  bottom  of  the  second  boiler,  B2 
(1000  to  2000  litres),  filled  with  milk  of  lime  (from  the  lime-tank,  L),  which  soon  becomes 
heated  nearly  to  boiling  but  retains  the  greater  part  of  the  acetic  acid  as  calcium  acetate, 
whilst  the  vapours  proceed  through  the  boiler,  B3,  which  also  contains  milk  of  lime  ; 
finally,  the  methyl  alcohol  and  acetone  vapours  are  condensed  in  the  cooler,  B±,  and 
collected  in  the  reservoir,  D,  after  passing  through  the  test-glass,  m,  which  indicates 
the  density  (see  Fig.  129,  E,  p.  134,  and  Fig.  132,  E,  p.  136).  The  distillation  goes  on  until 
the  density  reaches  the  value  1-00,  this  usually  occurring  when  one-third  or  one-quarter 
of  the  total  liquid  of  the  boiler,  Bv,  is  distilled.  The  first  methyl  alcoholic  liquid  which 
condenses,  being  more  concentrated  (30  to  40  per  cent.),  is  kept  and  rectified  apart  from 
the  remaining  more  dilute  liquid  by  means  of  an  ordinary  rectifying  column,  Hl}  H2,  H3, 
in  Fig.  236  (see  also  Fig.  138,  p.  140). 

The  aqueous  tarry  residue  left  in  B^,  after  evaporation  of  all  the  acetic  acid,  is 
discharged  into  the  movable  tank,  M. 

When  the  liquid  in  the  second  boiler,  B2,  assumes  an  acid  reaction,  the  vapour  from 
Bl  is  passed  into  B3,  whilst  B2  is  discharged  into  the  vat,  Flf  below,  and  again  filled  with 
milk  of  lime,  into  which  the  vapours  from  B3  pass  before  they 
proceed  to  the  condenser,  B± ;  a  similar  change  is  then  made 
when  the  contents  of  B3  become  acid,  and  so  on.  The  calcium 
acetate  (about  20  per  cent.)  is  pumped  to  the  filter-press,  E, 
and  the  clarified  solution  collected  in  the  vat,  C,  which  feeds 
the  evaporating  pans  (iron  or  copper)  which  are  fitted  at  the 
bottom  with  a  lens-shaped  jacket.  This  is  best  seen  in  Fig.  237  ; 
the  steam  for  heating  is  passed  in  at  a  »nd  the  condensed  steam 
runs  off  at  b  ;  f  is  a  hood  fitted  with  counter-weights,  g,  and 
hence  capable  of  being  raised,  its  object  being  to  carry  off  the 
acrid,  irritating  vapours  rising  from  the  pan.  More  effective  are 
pans  with  double  concave  bottoms.  The  concentration  readily  -p,  237 

attains  a  value  of  40  per  cent.  ;  the  liquid  then  becomes  pasty 

and  must  be  stirred,  this  being  continued  until  the  mass  will  crumble  between  the 
fingers.  The  acetate  is  then  lightly  roasted  at  125°  to  145°  on  iron  or  copper  plates 
heated  by  the  hot  gases  from  the  pans  or  from  the  furnaces  used  for  distilling  the 
wood.  By  this  means  the  mass  loses  the  residual  water  and  certain  volatile  tarry  and 
empyreumatic  products  retained  by  the  mass,  which  changes  from  brown  to  grey,  if  it 
is  kept  well  mixed  until  it  can  be  powdered  between  the  fingers.  The  product  is  then 
broken  up  somewhat,  and  sold  in  bags  holding  60  to  70  kilos.  It  contains  80  to  84  per 
cent,  of  pure  calcium  acetate,1  10  to  12  per  cent,  of  water  (half  of  which  is  lost  only  at 
about  150°),  and  6  to  7  per  cent,  of  impurities  (CaCO3,  CaO,  tarry  matters,  &c.). 

F.  H.  Meyer  (Ger.  Pat.  214,558,  1908)  obtains  calcium  acetate  free  from  phenolic 
compounds  (which  calcium  acetate  usually  holds  very  tenaciously  in  the  form  of  an 
emulsion)  by  passing  the  gases  from  the  distillation  of  the  wood — when  freed  from  tar — 
into  a  tower  containing  lumps  of  calcium  carbonate,  which  combines  with  the  acetic  acid 
but  not  with  the  phenols. 

Also  the  fractional  condensation  method  described  in  U.S.  Pat.  969,635, 1910  (I.  Heckel), 
although  somewhat  complicated,  represents  a  marked  improvement. 

To  obtain  acetic  acid  from  calcium  acetate,  the  latter  was  formerly  decomposed  with 
hydrochloric  acid.  Nowadays,  however,  the  decomposition  is  effected  with  concentrated 

1  The  strength  of  commercial  calcium  acetate  is  determined  by  introducing  a  homogeneous  sample  of  5  grms. 
into  a  distilling  flask  with  50  c  c.  of  water  and  50  c.c.  of  pure  phosphoric  acid  (sp.  gr.  1-2) ;  the  mixture  is  shaken 
and  heated  gently  to  avoid  frothing,  the  distillation  products  being  cooled  and  condensed.  When  the  residue 
becomes  dense,  the  distillation  is  continued  in  a  current  of  steam.  The  distillation  is  continued  until  the  distillate 
amounts  to  about  200  c.c. ;  this  is  then  made  up  to  250  c.c.  Part  of  this  liquid  is  tested  for  hydrochloric  and 
phosphoric  acids  and  50  c.c.  of  it  are  titrated  with  normal  caustic  soda  solution  with  phenolphthalein  as  indicator 
to  determine  the  amount  of  acetic  acid  ;  1  c.c.  of  the  normal  soda  solution  corresponds  with  0-079  grm.  of  calcium 
acetate.  This  titration  also  gives,  besides  acetic  acid,  traces  of  other  volatile  acids  contaminating  the  calcium 
acetate,  but  this  error  is  inevitable.  Aqueous  solutions  of  pure  calcium  acetate  have  the  following  densities  : 
5  per  cent.,  1-0330  ;  10  per  cent.,  1-0492  ;  15  per  cent.,  1-0666  ;  20  per  cent.,  1-0874  ;  25  per  cent.,  1-1130  ;  30 
per  cent,,  1-1426. 


278 


ORGANIC    CHEMISTRY 


sulphuric  acid,  the  substances  being  mixed  slowly  in  shallow  iron  pans  arranged  over  a 
furnace  and  fitted  with  covers  and  stirrers  :  for  100  kilos  of  calcium  acetate,  65  to  70  kilos 
of  commercial  sulphuric  acid  of  66°  Be.  In  order  to  avoid  the  formation  of  sulphur 
dioxide  and  other  decomposition  products  at  the  high  temperature  attained  initially 
and  prevailing  during  the  distillation,  K.  Linde  distils  in  a  vacuum  with  steam-heat 
(superheated  if  necessary)  ;  this  procedure  renders  the  operation  more  rapid  and  the 
acetic  acid  purer,  besides  reducing  the  consumption  of  sulphuric  acid  almost  to  the 
theoretical  amount  (60  kilos)  and  allowing  of  the  treatment  of  larger  quantities  of  material 
at  a  time  ;  further,  the  final  portions  of  acetic  acid,  which  are  retained  with  great  tenacity 
by  the  calcium  sulphate,  can  be  more  easily  and  completely  separated.  The  left-hand 
half  of  Fig.  238  shows  diagrammatically  the  arrangement  used  in  treating  calcium  acetate, 
when  vacuum  distillation  is  not  employed.  The  sacks  of  calcium  acetate,  a,  on  the  upper 
floor  are  tipped  through  a  hopper  on  to  the  flat  cast-iron  pans,  b,  fitted  with  stirrers  ; 
the  pans  are  then  closed  and  the  measured  amount  of  sulphuric  acid  in  n  (supplied  from 
the  large  leaden  tanks,  e),  slowly  introduced.  The  mass,  which  begins  to  heat,  is  then 
heated  by  the  fire  underneath,  the  stirrers  being  kept  in  motion  meanwhile. 

The  acetic  acid  is  gradually 
evolved  from  the  copper  tube  lead- 
ing first  to  the  vessel,  c,  where  the 
powder  and  acid  spray  carried  over 
are  deposited,  and  then  to  the  copper 
coils  in  d,  where  the  acetic  acid  is 
condensed  and  cooled,  to  be  col- 
lected in  the  tank,  m  ;  a  lateral  test- 
glass,  containing  an  aerometer,  is 
fitted  to  the  condenser  and  allows 
the  density  of  the  distilled  acid  to 
be  read  off  at  any  moment.  When 
the  vapour-delivery  tube  begins  to 
cool,  the  operation  is  at  an  end  ;  the 
-fire  is  then  covered  with  ashes  and 
the  residual  calcium  sulphate  dis- 
charged through  a  wide  lateral  tube, 

k,  and  conveyed  from  the  factory  by  an  archimedean  screw.  Another  distillation  is 
then  immediately  commenced. 

The  yield  from  100  kilos  of  calcium  acetate  amounts,  under  favourable  conditions,  to 
80  kilos  of  72  to  75  per  cent,  acetic  acid,  which  always  contains  a  few  per  cent,  of  sul- 
phurous acid.  Part  of  the  latter  has  been  already  eliminated  during  the  distillation  as 
uncondensed  gas  and  carried  to  the  chimney.  During  recent  years  the  introduction  of 
vacuum  distillation  has  been  almost  universal,  as  it  economises  fuel,  gives  an  increased 
yield  and  a  purer  product,  and  accelerates  complete  distillation  with  a  minimal  production 
of  sulphurous  acid. 

It  will  be  readily  understood  that  the  use  of  less  concentrated  sulphuric  acid  and  moist 
calcium  acetate  gives  a  more  dilute  acetic  acid.  A  large  part  of  the  acetic  acid  is 
put  on  the  market  as  it  is  or  diluted  with  water  to  bring  it  to  a  concentration  of  40  per 
cent.,  which  is  often  required  practically. 

When,  however,  purer  and  more  concentrated  acid  is  desired,  use  is  made  of  a  rectifying 
column  quite  similar  to  those  employed  in  the  case  of  alcohol  (see  p.  140).  The  column 
is,  however,  constructed  of  copper,  as  this  metal  is  more  resistant  (although  not  com- 
pletely so)  than  others  towards  organic  acids,  if  air  is  excluded.  The  heating  is  carried 
out  with  indirect  steam  under  5  atmos.  pressure,  which  circulates  in  coils  at  the  bottom 
of  the  still.  The  copper  column  is  fitted  inside  with  perforated  plates  of  porcelain  or 
baked  clay  arranged  alternately  with  copper  or  clay  rings  ;  the  condenser  consists  of  a 
copper,  or,  more  rarely,  a  clay  coil.  The  right-hand  half  of  Fig.  238  represents  the 
rectifying  apparatus  :  g  is  the  still,  h  the  column,  /  the  dcphlegmator,  and  i  the  condenser. 
When  the  apparatus  is  not  in  use  it  is  well  rinsed  and  then  completely  filled  with  water, 
in  order  to  prevent  the  acid,  in  presence  of  air,  from  attacking  the  copper.  The  first 
portion  (about  one-tenth)  of  the  distillate  is  kept  separate,  as  it  is  more  dilute  and  contains 
the  sulphurous  anhydride  and  a  large  part  of  the  empyreumatic  products,  and  the  last 


FIG.  239. 


279 

tenth  or  more  is  not  distilled  but  is  also  kept  separate,  being  very  impure.  According  as 
more  or  less  foreshots  and  tailings  are  separated,  a  very  concentrated  (96  to  99  per  cent.) 
acid,  or  one  of  about  80  per  cent,  strength  is  obtained,  both,  however,  containing  traces 
of  copper  and  empyreumatic  products  ;  the  latter  can  be  removed  by  mixing  the  acid 
in  clay  vessels  with  a  little  concentrated  potassium  permanganate  and  then  filtering. 
The  empyreumatic  substances  may  also  be  removed  (e.g.  in  the  manufacture  of  essence 
of  vinegar)  by  distilling  the  acid  over  potassium  chromate.  Traces  of  copper  are  elimi- 
nated by  redistilling  this  acid  from  a  copper  still  by  means  of  indirect  steam,  the  con- 
densing coils  and  tubes  being  of  earthenware  or  silver  and  carboys  being  used  for  collecting 
the  pure,  refined  acid.  Nowadays  it  is  sometimes  considered  preferable  to  construct  the 
small  head  of  the  still  and  the  whole  of  the  refrigerating  coil  of  silver,  as  is  shown  in 
Fig.  239,  since  the  coil  then  conducts  heat  well  and  is  not  much  more  expensive  than  the 
two  earthenware  coils  necessary  to  give  the  same  rapidity  of  condensation  ;  besides  which, 
earthenware  coils  are  fragile  and  of  no  value  when  broken.1  According  to  Ger.  Pat.  220,705, 
1907,  pure  acetic  acid  containing  only  traces  of  S02  can  be  obtained  by  heating  calcium 
acetate  (100  parts)  to  130°  in  a  vacuum  and  then  introducing  a  mixture  (55  parts)  of  equal 
amounts  of  acetic  and  concentrated  sulphuric 
acids  ;  by  continuing  the  heating  in  a  vacuum, 
the  whole  of  the  acetic  acid,  including  that  added, 
distils  over,  the  yield  being  95  per  cent. 

During  the  winter  care  must  be  taken  not 
to  cool  the  condensing  coils  too  much,  as  other- 
wise the  pure  (glacial)  acetic  acid  may  solidify 
and  cause  obstruction.  Also  in  stores  where 
acetic  acid  is  kept  in  wooden  casks,  earthenware 
vessels,  or  carboys,  the  temperature  must  be 
maintained  above  16°  if  a  troublesome  solidifi- 
cation of  large  quantities  of  the  acid  is  to  be 
avoided.  Glacial  acetic  acid  is  also  prepared  by 

distilling  92  parts  of  pure  dehydrated  (by  fusion  at  240°)  sodium  acetate  with  98  parts  of 
concentrated  sulphuric  acid.  In  1901,  the  Renania  chemical  firm  patented  a  process  for 
distilling  calcium  acetate  with  a  sodium  polysulphate,  Na2H3(SO4)2,  which  acts  like 
sulphuric  acid  but  without  giving  secondary  decomposition  products.  Formerly,  glacial 
acetic  acid  was  obtained  by  Melsen's  reaction  (1844),  which  consists  in  adding  potassium 
acetate  to  dilute  acetic  acid  and  evaporating  until  a  salt,  combined  with  acetic  acid, 
crystallises  ;  this  salt,  which  melts  at  148°,  decomposes  at  200°  to  250°,  pure  glacial 
acetic  acid  distilling  and  the  potassium  acetate  (which  decomposes  only  above  300°) 
remaining  for  a  subsequent  operation. 

USES,  STATISTICS,  AND  PRICE  OF  ACETIC  ACID.  Considerable 
quantities  of  commercial  acetic  acid  (35-40  per  cent.)  are  used  in  printing 
and  dyeing  wool  and  silk,  especially  with  alizarin  and  other  dyes  which 
withstand  feebly  acid  baths  ;  it  is  also  largely  employed  for  giving  silk  its 
characteristic  rustling  property  after  dyeing  or  cleaning.  The  pure  acid 
serves  in  the  preparation  of  numerous  acetates  (ammonium,  chromium,  and 
aluminium — which  are  used  in  dyeing  tissues  and  rendering  them  impervious 
— lead,  &c.),  different  esters  and  various  aniline  dyes.  After  it  became 
obtainable  in  a  pure  state,  by  rectification,  it  acquired  great  importance  for 
the  preparation  of  essence  of  vinegar  (various  aromatic  herbs  being  added) 
and,  when  diluted  with  water,  replaces  ordinary  table  vinegar.  It  has  been 
proposed  to  denature  acetic  acid,  to  be  used  in  chemical  industries,  by  addition 
of  formic  acid,  so  that  it  may  be  freed  from  taxation  (see  p.  280). 

1  Testing  of  acetic  acid.  If  no  empyreumatic  products  are  present,  a  mixture  of  10  c.c.  of  the  acid,  15  c.c.  of 
water,  and  1  c.c.  of  0-1  per  cent,  potassium  permanganate  solution  will  remain  reddish  in  colour  for  more  than  one 
minute.  The  acid  should  not  contain  higher  homologous  acids  ;  these  are  detected  by  dissolving  PbO  (litharge) 
in  the  30  per  cent,  acid  until  only  a  faint  acidity  remains,  the  solution  being  then  heated  and  filtered  ;  if  the 
crystals  which  form  are  not  transparent  and  colourless,  but  show  white  flocks  like  mould,  the  acid  is  to  be  rejected. 
The  presence  of  other  organic  acids  in  acetic  acid  can  also  be  detected  by  fractionally  precipitating  the  silver 
salt  and  determining  the  silver  in  the  separate  fractions  by  heating  in  a  crucible.  Pure  silver  acetate  contains 
64-6  per  cent,  of  silver.  For  other  tests  see  p.  272. 


280  ORGANIC    CHEMISTRY 

The  price  of  the  acid  varies  with  the  purity  and  concentration1 ;  ordinary  commercial 
30  per  cent.  (sp.  gr.  1-041)  is  sold  at  about  24s.  ;  the  40  per  cent,  acid  (sp.  gr.  1-052)  at 
30s.  to  325.  ;  and  the  50  per  cent,  acid  (sp.  gr.  1  -061 )  at  40*.  per  quintal.  The  pure  acid 
costs  25  per  cent,  more  than  the  commercial  at  the  same  concentration,  and  the  pure 
glacial  (99  to  100  per  cent.)  88s.  to  92s.  per  quintal. 

There  are  four  or  five  factories  in  Italy  for  the  distillation  of  wood  and  the  preparation 
of  calcium  acetate  and  acetone  (one  firm  alone  distils  300  quintals  of  wood  per  day),  but 
they  work  irregularly,  and  in  recent  years  calcium  acetate  has  been  imported  from  America. 
In  1910,  13,200  quintals  were  imported  (all  from  the  United  States)  at  an  average  price 
of  19s.  per  quintal  ;  in  the  same  year  2212  quintals  of  the  impure  acid  of  less  than  50  per 
cent,  strength  were  imported  at  an  average  price  of  22s.  to  24s.,  and  772  quintals  of  the 
pure  acid  of  more  than  70  per  cent,  strength  at  a  price  of  45s.  to  72s.  per  quintal ;  also 
861  quintals  of  crude  acid  and  1447  of  pure  dilute  acid  were  exported. 

In  1900  the  United  States  produced  400,000  quintals  of  calcium  acetate.2  Germany 
obtained  from  wood  in  1903  more  than  £280,000  worth  of  glacial  acetic  acid  and  exported 
about  35,280  quintals  of  greater  strength  than  30  per  cent.,  this  quantity  diminishing 
to  28,453  quintals  in '1905  and  to  15,700  quintals  in  1910  (also  1360  quintals  less 
concentrated  than  30  per  cent.)  ;  48,OQO  quintals  of  pyroligneous  acid  were  imported 
for  purification. 

In  1900  the  Badische  Anilin-  und  Soda-Fabrik,  Ludwigshafen,  consumed,  merely 
for  the  synthesis  of  artificial  indigo  (chloroacetic  acid  being  prepared  by  means  of  liquid 
chlorine),  more  than  20,000  quintals  of  glacial  acetic  acid  (corresponding  with  100,000 
cu.  metres  of  wood),  the  total  production  of  this  acid  in  Germany  being  about  100,000 
quintals. 

Germany  imported,  in  1904,  182,000  quintals  of  calcium  acetate  ;  205,100  quintals 
in  1905  ;  201,000  in  1906  ;  174,000  in  1908  ;  and  235,450  in  1909  ;  the  production  in 
the  country  did  not  exceed  100,000  quintals. 

France  distils  every  year  the  wood  from  200,000  hectares  of  forest,  obtaining  50,000 
to  55,000  tons  of  distilled  products  of  the  value  £600,000. 

Importation  to  England  was  3700  tons  of  acetic  acid  in  1909  and  4450  tons  (£87,920) 
in  1910  ;  also  3500  tons  of  calcium  acetate  in  1909  and  4300  tons  (£42,470)  in  1910.  The 
United  States  exported  30,000  tons  (£306,000)  of  calcium  acetate  in  1910  and  35,000  tons 
(£318,600) in  1911. 

The  manufacture  of  crude  pyroligneous  acid  in  Italy  is  exempt  from  taxation,  but 
the  rectification  and  production  of  the  pure  acid  are  subject  to  a  manufacturing  tax  of 
12s.  per  quintal  for  acid  of  less  than  10  per  cent,  strength  ;  41s.  for  10  to  30  per  cent, 
acid  ;  72s.  for  30  to  50  per  cent,  acid  ;  100s.  for  50  to  75  per  cent,  acid  ;  129s.  for  70  to 
90  per  cent,  acid  ;  and  144s.  for  stronger  acid.  The  Customs  import  tariff  adds  a  further 
tax  of  19d.  per  quintal  for  crude  pyroligneous  acid  of  less  strength  than  50  per  cent.,  and 
for  the  pure  acid  up  to  10  per  cent.  ;  4s.  Wd.  for  10  to  30  per  cent,  acid  ;  8s.  for  30  to 
50  per  cent,  acid  ;  11s.  for  50  to  70  per  cent,  acid  ;  14s.  for  70  to  90  per  cent,  acid  ;  and 
16s.  for  90  to  98  per  cent.  acid. 

MANUFACTURE  OF  VINEGAR 

Vinegar  is  formed  by  the  acetic  fermentation  (by  means  of  Mycoderma  aceti,  Bacillus 
aceticus,  or  Bacterium  aceti,  seep.  122,  Fig.  114, a)  of  saccharine  liquids  which  have  under- 
gone alcoholic  fermentation,  such  as  wine,  beer,  cider,  &c.  Since  this  transformation 
of  alcohol  into  acetic  acid  takes  place  merely  on  exposure  of  these  liquids  to  the  air,  it  is 

1  The  balance-sheet  for  a  small  factory  treating  10  quintals  of  calcium  acetate  per  day  is  roughly  as  follows  : 
Outgoings  :  10  quintals  of  80  per  cent,  calcium  acetate,  350  lire  +  500  kilos  of  coal  for  decom- 
posing the  acetate,  for  the  first  and  second  distillations,  for  rectification  and  for  generating  steam, 
20  lire  +  6-5  quintals  sulphuric  acid  (66°  Be1.),  41  lire  +  staff  and  general  expenses,  insurances, 
Ac.,  40  lire  +  depreciation  on  machinery  (50,000  lire)  and  buildings  (40,000  lire),  25  lire  +  lubrica- 
tion, lighting,  repairs,  &c.,  18  lire  +  motive  power  8  lire  Total  502  lire. 

Income  :  450  kilos  of  98  per  cent,  acetic  acid,  450  lire  +  300  kilos  30  per  cent,  acetic  acid,  85  lire.    Total  535  lire. 
Capital  employed  (circulating  as  well),  120,000  lire  ;  net  annual  profit,  about  12-5  per  cent. 
2  In  1907  the  United  States  contained  100  distilleries  treating  a  total  of  4,390,000  cu.  metres  of  wood  (1,767.000 
cu.  metres  in   1900)  with  a  mean  yield  per  cubic  metre  of  8  to  10  litres  of  methyl  alcohol  (82  per  cent.),  22  to  25 
kilos  of  calcium  acetate  (80  to  82  per  cent.),  15  to  20  litres  of  tar,  and  0-5  cu.  metre  of  charcoal,  0-6  cu.  metre 
of  wood  being  used  as  fuel  for  heating  the  retorts.     The  best  yields  are  obtained  with  maple-wood,  then  follow 
beech,  birch,  and  the  Coniferae  (which  form  only  10  per  cent,  of  the  total  wood  distilled).     The  numerous  sawmills 
of  the  United  States  yield  150  million  tons  of  waste. 


MANUFACTURE    OF    VINEGAR 


281 


probable  that  vinegar  and  hence  acetic  acid  was  the  first  acid  known  to  man.  The  same 
result  is  obtained  by  treating  alcohol  with  various  oxidising  agents  (chromic  acid,  ozone, 
manganese  dioxide  and  sulphuric  acid,  &c.),  but  acetaldehyde  is  also  largely  formed  in 
these  cases,  which  hence  do  not  compete  in  practice  with  the  biological  process.  The 
composition  of  vinegar  was  studied  by  Berzelius  (1814),  and  Kiitzing  in  1837  showed 
the  importance  of  the  living  organism  of  the  mother-of -vinegar  to  the  formation  of  acetic 
acid,  while  Turpin  in  1840  examined  and  characterised  these  micro-organisms  more 
exactly.  According  to  Liebig,  the  transformation  of  alcohol  into  acetic  acid  is  brought 
about  by  the  catalytic  action  of  certain  nitrogenous  substances  capable  of  fixing  oxygen 
from  the  air  and  of  yielding  it  to  the  alcohol.  In  1868,  however,  Pasteur  showed  that 
this  phenomenon  is  caused  by  a  vegetable  organism,  Mycoderma  aceti,  formed  of  small, 
oblong  cells  (about  3  micro-mm.  long),  slightly  constricted  in  the  middle  (where 
segmentation  then  takes  place)  and  often  arranged  in  chains.  When  these  multiply  at 
the  surface  of  the  alcoholic  liquid,  they  form  first  a  thin  membrane  which  gradually 
thickens,  and  when  this  membrane  is  formed  in  the  body  of  the  liquid  it  becomes  muci- 
laginous and  spreads  through  the  whole  liquid,  giving  a  compact  mass — the  so-called 
mother -of -vinegar — reaching  to  the  surface.  It  develops  very  well  in  slightly  alcohol,  c 
liquids  (3  to  6  per  cent.,  but  better  with  13  per  cent,  of  alcohol,  and  still  more  readily 
in  presence  of  about  1  per  cent,  of  acetic  acid  and  0-1  per  cent,  of  phosphate)  ;  the  most 
favourable  temperature  is  about  30  per  cent.,  acetification  ceasing  at  45°  and  below  6°  ; 
the  action  is  retarded  by  light.  When  the  acetic  membrane  becomes  submerged,  the 
fermentation  ceases  and  only  recommences  with  the  formation  of  a  fresh  superficial 
membrane,  which  can  absorb  oxygen  from  the  air  and  transfer  it  to  the  alcohol  *  : 

CH3-CH2-OH  +  02  =  H20  +  CH3-COOH. 

According  to  this  equation,  the .  theoretical  yield  is  60  grms.  of  acetic  acid  per  46  grms. 
of  alcohol,  but  the  practical  yield  is  15  to  20  per  cent,  less  than  this  ;  under  the  most 
favourable  conditions,  a  liquid  containing  10  per  cent,  of  alcohol  by  volume  yields  a 
vinegar  with  10  per  cent,  of  the  acid  by  weight.  When  almost  all  of  the  alcohol  is 
converted  into  acetic  acid,  part  of  the  latter  begins  to  decompose  into  H20  +  CO2  ;  this 
change  can  be  avoided  by  continuing  to  add  alcohol  to  the  acetic  liquid  or  by  causing 
the  mother-of-vinegar  to  sink,  and  decanting  the  liquid.  The  old  or  slow  wine-vinegar 
process,  known  as  the  Orleans  process,2  has  been  replaced  almost  everywhere  by  the  more 
rapid  German  process,  proposed  by  Schiitzenbach  in  1823  and  subsequently  greatly 
improved.  But  as  early  as  1730  Boerhave  prepared  vinegar — and  in  some  places  his 
method  is  used  even  to-day — by  means  of  two  vats  standing  on  feet  and  communicating 
at  the  bottom  by  means  of  a  tube.  One  vat  is  filled  with  the  wine,  but  the  other  is  only 

1  This  explains  the  harmful  effect  of  vinegar  worms  (small  worms  belonging  to  the  Nematodes),  which   form 
a  transparent,  white,  slimy  mass   moving  along  the   walls  of  the  vessel,  and   breaking  the  skin  of  Myco- 
derma aceti  at  the  surface  of  the  liquid  and  hence 
causing  it  to  sink.     Another  enemy  of  vinegar  is    ~j_ 
the  vinegar  mite  (an  insect  J  mm.  in  length)  which      | 
multiplies  at  an  enormous  rate  and  accumulates  in 
large  masses  in  the  vinegar,  succeeding  in  interrupt- 
in?  the  acetic  fermentation  and  starting  putrefactive 
changes.     In  order  to  prevent  the  entry  of  these 
insects   into   the   vats   and    casks,    the   latter  are 
smeared  outside  with  a  ring  of  birdlime,  to  which 
the  mites  become  fixed.   Also  Mycoderma  vini  hinders 
the  development  of  Mycoderma  aceti,  and  equally 
harmful  to  acetic  fermentation  are  antiseptic  sub- 
stances in  general,  sulphur  dioxide  and   empyreu- 
matic  substances  (including  those  of   pyroligneous 
acid).     Blue  and  violet  light  (hence  white  light,  but 
not  red  or  yellow  light)  likewise  retard  the  growth 
of  Mycoderma  aceti. 

*  This  process  is  one  of  the  oldest  and  was  for- 
merly, and  is  still,  carried  out  more  especially  in  the 


FIG.  240. 


town  of  Orleans,  by  filling  a  number  of  superposed  casks  (Fig.  240)  to  the  extent  of  one-eighth  of  their  volume  with 
good  wine  vinegar  and  then  adding  each  week  about  10  litres  of  wine  (or  wine-dregs,  containing  8  to  10  per  cent, 
of  alcohol,  filtered  through  beech  shavings  in  the  vat,  R  ;  white  wines  are  preferable).  When  the  casks  are  about 
half-full,  the  vinegar  is  made  and  two-thirds  of  it  is  drawn  off  and  either  filtered  through  beech  chips  or  allowed 
to  deposit  in  the  vat,  R',  underneath  ;  the  addition  of  10  litres  of  wine  per  week  is  then  continued.  By  means 
of  the  stove,  X,  the  temperature  is  maintained  at  25°  to  30°.  This  method  gives  a  fine,  aromatic  vinegar,  but  it 
i  svery  slow  and  cannot  be  interrupted  when  desired.  Pasteur  prepared  vinegar  of  an  inferior  quality,  more 
rapidly  by  adding  a  little  vinegar  to  wine  in  wide,  shallow  vats  and  then  sowing  on  the  surface  a  little  pure 
•  Mycoderma  aceti  from  another  vat. 


282 


ORGANIC    CHEMISTRY 


FIG.  241. 


about  half  filled,  the  vinasse  not  being  submerged.  Every  twelve  hours  the  full  vat 
is  half  emptied  into  the  other.  If  the  temperature  is  kept  at  25°  to  30°,  acetification  is 
complete  in  12  to  15  days. 

In  the  German  or  quick  vinegar  process,  wooden  vats,  2-5  to  3  metres  high  and  1-5  to 
2  metres  in  diameter,  are  used  (Fig.  241).  These  are  filled  almost  completely  with  wood 
shavings,  which  are  supported  on  a  perforated  false  bottom,  L,  and  covered  with  a  wooden 
disc  with  perforations  traversed  by  cords  held  by  knots  so 
as  to  form  a  uniform  spray  of  the  alcoholic  liquid  (8  to 
10  per  cent.),  mixed  with  one-fifth  of  its  volume  of  wine- 
vinegar,  over  the  wood  chips.  Six  or  seven  glass  tubes 
passing  through  the  upper  disc  allow  of  a  continuous  circu- 
lation of  air,  which  enters  at  the  periphery  of  the  lower  part 
of  the  vat  through  the  holes,  Zi,  and  through  the  pipe,  E, 
passes  through  the  shavings — which  become  gradually 
warmed  as  acetification  proceeds — and  issues  through  the 
apertures,  Z',  at  the  top.  The  temperature  is  shown  by  a 
thermometer,  T,  inserted  in  a  glass  tube,  reaching  to  the 
middle  of  the  vat.  When  the  temperature  exceeds  40°,  it 
is  lowered  by  a  more  rapid  passage  of  the  alcoholic  liquid, 
which  collects  at  E,  and  is  discharged  by  the  siphon,  H,  to 
be  conveyed  to  the  top  of  the  vat  and  again  circulated 
through  the  shavings,  this  process  being  continued  until 
acetification  is  complete.  In  some  cases  three  such  vats  are  superposed,  the  liquid 
passing  down  through  them  all  ;  after  one  or  two  complete  circulations  the  operation  is 
complete,  although  the  amount  of  acid  formed  is  not  equal  to  that  of  the  alcohol  in  the 
original  liquid. 

The  liquids  thus  obtained  contain  up  to  12  to  13  per  cent,  of  acetic  acid  (14  per  cent, 
cannot  be  exceeded  as  the  Mycoderma  would  then  be 
killed)  and,  if  the  operations  are  conducted  with 
care,  less  than  10  per  cent,  of  the  alcohol  used  is  lost  ; 
otherwise,  especially  if  the  temperature  becomes  too 
high,  so  that  part  of  the  alcohol  evaporates,  the  loss 
may  amount  to  30  to  50  per  cent. 

Vinegar  of  an  inferior  quality  is  largely  prepared 
nowadays  from  various  alcoholic  liquids  made  from 
cereals,  starch,  beetroot,  or  molasses,  just  as  indus- 
trial alcohol  is  prepared.  But  such  vinegar  lacks 
the  pleasant  aroma  of  wine -vinegar. 

It  has  been  proposed  to  accelerate  acetification  by 
means  of  compressed  air,  but  greater  success  has 
attended  the  Michaelis  or  Luxemburg  method,  in 
which  acetification  is  carried  out  in  rotating  casks  (5 
to  6  hectols.)  filled  with  beech  shavings  (washed  first 
with  hot  water  and  then  with  hot  vinegar)  and  tra- 
versed by  two  osier  tubes,  one  along  the  horizontal 
axis  and  the  other  along  the  vertical  axis,  to  allow 
of  the  circulation  of  air.  The  shavings  are  washed 
with  wine -vinegar,  and  the  cask  filled  about  half 
full  with  wine  (Fig.  242).  During  the  first  three 
days  the  casks  are  rotated  three  times  a  day  and 
subsequently  six  times  a  day.  Acetification  is  complete  in  about  eight  days. 

An  ingenious,  rapid,  and  continuous  method  for  the  manufacture  of  vinegar  is  that 
of  Villon  (Fig.  243),  which  makes  use  of  two  drums  (2  metres  by  2  metres),  B  B,  arranged 
inside  in  the  form  of  a  spiral.  The  iron  spirals  are  covered  or  varnished  with  gutta-percha 
and  are  30  metres  in  length,  the  coils  being  10  cm.  apart  and  the  spaces  between  filled 
with  beech  shavings  or  charcoal.  The  drums  rotate  in  opposite  directions,  the  left-hand 
one  rotating  once  in  five  minutes  and  dipping  up  each  time  8  litres  of  the  alcoholic  liquid 
from  the  vessel,  C,  this  liquid  being  then  passed  through  the  axial  tube  to  the  second 
drum,  which  discharges  it  into  the  other  dish,  C.  The  liquid  then  passes  to  a  similar 


FIG.  242. 


CONTINUOUS    VINEGAR    PROCESS 


283 


pair  of  drums  and  thence  to  a  third  pair,  on  leaving  which  the  vinegar  is  ready  ;  by  this 
means  1000  litres  are  produced  in  20  hours.  By  means  of  the  pump,  R,  a  current 
of  air  is  drawn  through  each  drum  to  the  centre,  whence  it  passes  through  the  tube,  V, 
to  a  cooling  coil,  S,  to  condense  the  small  amount  of  acetic  acid  vapour  it  carries  over. 


FIG.  243. 

Another  continuous  and  very  rapid  method,  which  avoids  loss  of  acetic  acid  or  aldehyde 
and  diminishes  the  labour  necessary  by  establishing  more  intimate  contact  between  the 
alcoholic  liquid  and  the  subdividing  material,  is  that  in  which  the  stave  acetifier  (Figs.  244 
and  245)  is  used.  This  consists  of  a  wooden  box,  P,  about  1  metre  wide  and  2  metres 
high,  terminating  at  the  top  in  a  channel,  R.  The  box  is  filled  with  nine  or  ten  layers 
of  thin  beech  sticks  placed  vertically  and  very  close  one  to  the 
other.  The  position  of  the  sticks  in  one  layer  is  crossed  with 
respect  to  that  of  the  sticks  in  the  next  layer.  These  sticks  are 
held  apart  by  small  strips  of  wood  so  as  to  allow  of  the  passage 
of  a  thin  film  of  liquid  downwards  and  of  the  air  upwards.  The 
total  surface  of  the  sticks  in  an  apparatus  of  the  dimensions 
stated  above  amounts  to  more  than  1000  sq.  metres,  so  that  the 
oxidation  is  extraordinarily  rapid,  while  the  working,  which 
may  continue  uninterruptedly  for  years,  is  extremely  regular 

and-  simple.     The   air   enters   at    a 

lateral  slit,  Z,  at  the   bottom,  this 

being  covered  with  gauze  to  prevent 

access  of  harmful  insects ;    and  the 

draught  is  regulated  by  a  slider  in 

the  exit-channel,  R  ;  the  vinegar  is 

discharged  at  E.     The  thermometer, 

T,    shows    the    temperature   of  the 

air  as  it  leaves.      The   figure  shows 

also  the  contrivance  for  feeding  the 

apparatus  regularly  and  continuously 

with  the  alcoholic  liquid.     The  latter 

is  contained  in  the  tank,  B,  in  which 

is  a  wooden  float,  F,  moving  along 

three  vertical  rods,  L,  and  carrying 

the  glass  siphon,  W,  terminating  in 

a    rubber   tube    with    a    regulating 

clip,  n.     The  liquid  from  the  siphon 

falls    into    a   tube,    G,   and    thence 

through  the  tube,  A  C,  to  the  vessel, 

H  (3  litres  capacity),  and,  when  this 
is  full,  it  discharges  through  the  siphon,  r,  on  to  the  perforated  plate,  V,  which  distributes 
the  liquid  as  a  fine  spray  over  the  bundles  of  sticks,  and  is  traversed  by  several  glass  tubes 
to  allow  of  the  escape  of  the  ascending  air.  In  this  way  the  flow  of  liquid  from  B  is 
independent  of  the  amount  of  liquid  present  in  it  at  any  instant  (that  is,  of  the  pressure 
it  exerts).  The  clip,  n,  is  regulated  so  that  the  vessel,  H,  is  refilled  and  discharges  its 
3  litres  of  liquid  every  one  or  two  hours  (or  in  any  other  prearranged  time). 

Attempts  have  been  made  to  replace  the  ordinary  biological  acetification  by  chemical 
oxidation  of  the  alcohol  by  means  of  platinum  black  or  even  of  ozone,  but  neither  method 
has  attained  to  practical  importance. 


FIG.  244. 


FIG.  245. 


284  ORGANIC    CHEMISTRY 

Vinegar  is  kept  in  full  casks  in  stores  like  those  used  for  wine,  but  it  is  not  injured 
by  a  high  air-temperature.  An  excess  of  air  in  the  vessels  and  the  continued  presence 
of  the  mother-of -vinegar  lower  its  strength,  and,  when  this  becomes  too  low,  putrefaction 
may  develop.  Its  keeping  properties  and  aroma  may  be  enhanced  by  pasteurisation 
(see  p.  156)  at  50°  to  60°.  A  weak  vinegar  may  be  strengthened  and  kept  if  a  little  pure 
acetic  acid  is  added  to  it. 

WINE  VINEGAR  (white  or  red)  is  distinguished  from  other  vinegars  by  its  aroma, 
due  partly  to  ethyl  acetate  and  to  small  proportions  of  aldehydes.  It  usually  contains 
6  to  9  per  cent,  of  acetic  acid  and  less  than  1  per  cent,  of  alcohol,  and  has  the  density 
1-015  to  1-020.  The  extract  and  the  ash  have  the  same  compositions  as  those  of  wines, 
the  former  being  rich  in  cream  of  tartar. 

BEER  VINEGAR  contains  4-5  to  6  per  cent,  of  extract  rich  in  maltose,  dextrin, 
albuminoids,  and  phosphates,  and  exempt  from  cream  of  tartar. 

This  vinegar  also  contains  less  acetic  acid  and,  since  it  does  not  keep  so  well  as  that 
from  wine,  is  used  to  break  down  excessively  strong  vinegars. 

ARTIFICIAL  VINEGARS,  prepared  from  purely  alcoholic  liquids  or  from  acetic  acid 
and  a  colouring  material  such  as  caramel,  have  very  little  extract  and  no  cream  of  tartar, 
whilst  the  percentage  of  acetic  acid  sometimes  reaches  12  or  13. 

In  the  ANALYSIS  OF  VINEGAR,  the  density  of  the  extract  and  the  ash  are  deter- 
mined as  with  wine  (p.  156).  The  content  of  acetic  acid  cannot  be  estimated  exactly 
with  a  standard  alkali  solution,  since  other  acids  (tartaric,  succinic,  &c.)  present  influence 
the  titration  ;  nor  do  the  graduated  tubes  (acetometers)  give  accurate  results.  A  more 
exact  determination  is  effected  by  distilling  the  acetic  acid  in  a  current  of  steam,  as  in 
the  analysis  of  calcium  acetate  (p.  277). 

Adulteration  of  vinegar,  which  is  somewhat  frequent,  is  detected  by  the  following  tests  : 
real  wine  vinegar  exhibits  certain  relations  between  the  acetic  acid  and  extract.  In  wine 
the  ratio  is  4  parts  of  alcohol  for  about  1  of  extract,  after  deduction  of  the  sugar  present 
in  sweet  wines  ;  assuming  a  loss  of  15  per  cent,  of  the  alcohol  during  the  conversion  into 
vinegar,  a  pure  wine  vinegar  with  5-31  per  cent,  of  acetic  acid  should  contain  1-08  per 
cent,  of  extract  ;  one  with  7-15  per  cent,  of  acid,  1-44  per  cent,  of  extract  ;  one  with 
8-9  per  cent,  of  acid,  1-8  per  cent,  of  extract,  and  one  with  10-7  per  cent,  of  acid,  2-16 
per  cent,  of  extract,  the  ratio  of  acid  to  extract  always  being  about  4-9  :  1.  Addition 
of  malt  or  beer  vinegar  is  recognised  by  its  reduction  of  Fehling's  solution,  or  by 
concentrating  80  c.c.  of  the  vinegar  to  about  2  c.c.  and  then  adding  alcohol :  the 
formation  of  a  white  precipitate  (dextrin)  soluble  in  water  indicates  such  adulteration 
with  certainty. 

If  mineral  acids  have  been  added,  4  or  5  drops  of  a  dilute  alcoholic  solution  of  methyl 
violet  (1  :  10,000)  will  give  a  greenish  colour  with  25  c.c.  of  the  vinegar  ;  also,  with  zinc 
sulphide,  hydrogen  sulphide  is  evolved  ;  and,  finally,  after  the  vinegar  has  been  heated 
with  a  trace  of  starch,  it  will  not  give  a  blue  colour  with  iodine.  The  presence  of  sulphuric 
acid  in  vinegar  is  detected  by  the  white  precipitate  formed  with  barium  chloride,  hydro- 
chloric acid  by  that  given  by  silver  nitrate  and  oxalic  acid  by  the  formation  of  a  white 
precipitate  with  calcium  chloride. 

Artificial  colouring-matters  are  detected  in  the  same  way  as  in  wine  and  beer,  and 
pyroligneous  acid  by  the  furfural  reaction  (see  this). 

The  price  of  good  wine  vinegar  is  little  less  than  that  of  wine,  but  artificial  vinegars 
are  cheaper. 

France  produces  annually  600,000  to  700,000  hectols.  of  vinegar,  but  in  Italy  the 
production  is  much  less  owing  to  the  competition  of  artificial  vinegar  and  to  the  excessive 
duty  of  17s.  6d.  per  hectol.  ;  in  1904-1905  the  thirty-eight  Italian  vinegar  factories 
consumed  6160  hectols.  of  alcohol,  the  output  of  artificial  vinegar  being  60,000  hectols. 

DERIVATIVES  OF  ACETIC  ACID 

SALTS  OF  ACETIC  ACID.  These  are  termed  acetates,  and  are  all 
soluble  in  water  (the  least  soluble  are  silver  and  mercurous  acetates).  They 
are  readily  formed  by  neutralising  acetic  acid  with  metallic  oxides  or  car- 
bonates, previously  dissolved  in  water.  But  pure  anhydrous  acetic  acid  or 
its  alcoholic  solution  does  not  decompose  alkaline  carbonates,  so  that  C02 


SALTS    OF    ACE  TIC    ACID  285 

precipitates    potassium    carbonate  from  an  alcoholic  solution  of  potassium 
acetate,  acetic  acid  being  liberated. 

Even  in  aqueous  solution,  acetic  acid  undergoes  only  slight  dissociation, 
but  the  acetates  are  considerably  dissociated  and  diminish  the  dissociation 
and  hence  the  acid  characters  of  acetic  acid  (see  vol.  i,  p.  94). 

POTASSIUM  ACETATE  (Normal),  CH3  -COOK,  melts  at  229°  and  is  soluble  in  wate. 
or  alcohol.  It  is  obtained  by  neutralising  potassium  hydrogen  carbonate  (KHCO3)  solution 
with  acetic  acid  and  evaporating  to  dryness.  The  acid  acetate,  CH3-COOK,  C2H4O2, 
is  obtained  by  dissolving  the  normal  acetate  in  acetic  acid  and  separates  from  the  latter 
in  crystals  which  melt  at  148°  and  decompose  at  200°,  liberating  anhydrous  acetic  acid. 

A  Diacid  Potassium  Acetate,  CH3-COOK,  2C2H4O2,  melting  at  112°,  is  also  known. 

The  commercial  refined  normal  acetate  costs  £6  per  quintal. 

SODIUM  ACETATE,  CH3-COONa,  crystallises  from  water  with  3H2O,  melts  at 
100°,  loses  water  and  solidifies  at  a  higher  temperature  and  then  melts  only  at  319°. 

In  the  cold  it  dissolves  to  some  extent  (1  :  23)  in  alcohol  or  in  its  own  weight  of  water, 
giving  a  feebly  alkaline  solution  and  considerable  lowering  of  temperature. 

It  is  prepared  by  neutralising  pyroligneous  acid  almost  completely  with  sodium 
carbonate  and  concentrating  the  solution  (after  removal  of  the  tar  from  the  surface)  to 
27°  Be.  ;  the  crystals  which  separate  on  cooling  are  centrifuged,  but  are  always  reddish 
brown.  The  mother-liquors  (which  readily  become  mouldy)  are  taken  to  dryness  and 
lightly  roasted  to  burn  the  tarry  products.  Crude  sodium  acetate  is  preferably  prepared 
by  treating  calcium  acetate  with  sodium  sulphate  and  then  with  a  little  soda  to  precipitate 
all  the  lime  ;  the  filtered  or  decanted  solution  is  evaporated  to  dryness,  heated  to  250°, 
redissolved  in  water,  concentrated,  and  allowed  to  crystallise. 

According  to  C.  Bauer,  pure  sodium  acetate,  free  from  the  reddish  brown  colour, 
can  be  prepared  directly  from  pyroligneous  acid  by  neutralising  with  sodium  carbonate, 
and  adding  to  the  solution  concentrated  to  27°  Be.,  2  per  cent,  of  caustic  soda,  the  liquid 
being  then  allowed  to  crystallise  in  wide  and  shallow  wooden  vessels.  The  crystals  are 
separated  by  centrifugation  and  redissolved,  the  small  amount  of  free  caustic  soda  being 
then  neutralised  with  commercially  pure  acetic  acid  ;  the  solution  is  boiled  to  expel  the 
excess  of  acetic  acid,  concentrated  to  27°  Be.,  and  left  to  crystallise. 

Acid  sodium  acetates  are  also  known. 

Sodium  acetate  serves  for  the  preparation  of  pure  acetic  acid,  and  is  used  in  dyeing,  &c. 

Crude  red  sodium  acetate  is  sold,  according  to  its  degree  of  purity,  at  28*.  to  30s.  per 
quintal  ;  the  white  purified  crystals  (pharmaceutical)  at  48*.  to  56*.  ;  and  the  doubly 
refined  and  fused  anhydrous  product  at  104*. 

AMMONIUM  ACETATE,  CH3-COONH4,  is  obtained  by  neutralising  hot  glacial 
acetic  acid  with  a  current  of  dry  ammonia  or  with  ammonium  carbonate.  The  pure 
crystals  which  separate  melt  at  113°  to  114°  and,  although  not  highly  hygroscopic,  dis- 
solve readily  in  water  giving  an  alkaline  solution  ;  the  solution  in  acetic  acid  deposits 
the  acid  acetate  melting  at  66°.  The  salt  acts  as  a  sudorific  and  dissolves  lead  oxalate 
and  sulphate.  It  is  used  to  some  extent  in  dyeing. 

.     The  commercial  brown  solution  at  10°  Be.  costs  £2  per  quintal  and  the  pure  solution 
of  the  same  density  49*.  Qd.  ;  chemically  pure  crystals  cost  £10  per  quintal. 

CALCIUM  ACETATE,  (CH3-COO)2Ca  +  2H20.  The  preparation  of  the  commercial 
product  has  already  been  described  on  p.  276.  The  pure  salt  is  obtained  by  repeated 
crystallisation  from  water,  and  costs  up  to  96*.  per  quintal.  Its  solubility  in  water 
diminishes  with  rise  of  temperature  up  to  a  certain  point  and  subsequently  increases. 

FERROUS  ACETATE  (Pyrolignite  of  Iron),  (CH3-COO)2Fe.  The  crude  product, 
used  as  a  mordant  in  the  dyeing  and  printing  of  textiles,  is  obtained  from  pyroligneous 
acid  and  iron  filings,  or  from  calcium  pyrolignite  and  a  concentrated  solution  of  ferrous 
acetate  ;  the  tarry  substances  present  preserve  it  from  oxidation.  A  solution  of  20°  Be. 
costs  12*.  per  quintal  and  one  of  30°  Be.  17*.  Qd.  The  pure  product  is  prepared  by 
dissolving  freshly  prepared  ferrous  hydroxide  in  30  per  cent,  acetic  acid. 

FERRIC  ACETATE,  (C2H3O2)3Fe,  used  as  a  mordant  in  dyeing,  is  obtained  from 
the  ferrous  salt  and  sodium  acetate.  It  gives  a  reddish  brown  solution  in  the  cold,  but 
in  the  hot  and  in  presence  of  a  large  amount  of  water,  a  reddish  brown  mass  of  basic 
ferric  acetate,  Fe(C2H302)2OH,  separates  ;  it  is  this  which  fixes  the  colouring-matters. 


286 

ALUMINIUM  ACETATE  (Normal),  A1(C2H3O2)3,  is  obtained  from  aluminium 
sulphate  and  the  corresponding  quantity  of  lead  acetate.  It  is  known  only  in  solution, 
in  which  it  gradually  undergoes  spontaneous  decomposition  into  acetic  acid  and  the  basic 
acetate  :  A1(C2H302)3  +  H2O  =  A1(C2H302)2OH  +  C2H402. 

When  the  solution  of  the  basic  acetate  is  boiled,  aluminium  hydroxide  and  acetic  acid 
separate  :  A1(C2H302)2OH  +  2H20  =  A1(OH)3  +  2C2H402. 

It  is  used  in  dyeing,  in  the  printing  of  textiles  and  in  the  preparation  of  impermeable 
fabrics.  For  the  last  purpose,  the  material  is  first  soaked  in  aluminium  acetate  solution 
and  then  heated  or  steamed,  A1(OH)3  thus  being  deposited  in  the  pores  of  the  fabric,  which 
is  rendered  impervious  to  water. 

BASIC  ALUMINIUM  ACETATE,  A1(C2H3O2)2OH  +  liH2O,  is  obtained  crystalline 
by  evaporating  a  solution  of  the  normal  acetate  cautiously  at  a  temperature  not  exceeding 
38°  ;  it  is  soluble  in  water.  Dilute  solutions  (4  to  5  per  cent.)  of  the  normal  acetate 
gradually  deposit,  on  the  walls  of  the  containing  vessel,  a  porcelain -like  crust  of  a  basic 
acetate  with  2H2O  or  2^H2O  :  this  is  insoluble  in  water. 

It  is  used,  like  the  normal  salt,  in  dyeing,  textile -printing,  &c. 

SILVER  ACETATE,  C2H3O2-Ag,  is  obtained  crystalline  by  adding  silver  nitrate 
to  a  concentrated  solution  of  an  acetate  (e.g.  that  of  ammonium).  It  is  a  characteristic 
salt  crystallising  from  water  in  shining  needles  (solubility  1  :  100  at  20°,  2-5  :  100  at  80°). 
When  calcined  in  a  porcelain  crucible,  it  leaves,  like  all  organic  silver  salts,  pure  metallic 
silver. 

NORMAL  LEAD  ACETATE  (Sugar  of  Lead),  (CH3COO)2Pb  +  3H2O, 
forms  monoclinic  plates  or  crystals,  has  a  disagreeable,  sweetish  taste,  is 
poisonous  and  exhibits  a  faintly  acid  reaction.  It  is  slightly  soluble  in  alcohol 
and  more  so  in  water  (1  part  dissolves  in  1-5  part  of  water  at  15°,  in  1  part 
at  40°,  or  in  0-5  part  at  100°).  It  loses  the  water  of  crystallisation  over 
sulphuric  acid  or  at  100°  and  then  melts  above  200°. 

It  is  used  as  a  mordant  in  the  dyeing  and  printing  of  textiles  and  also 
in  the  preparation  of  various  lead  salts  and  paints  and  certain  pharmaceutical 
products  ;  further,  for  conferring  hot-drying  properties  on  linseed  oil  to  be  used 
for  varnishes. 

Italy  produced  450  quintals  in  1904,  800  in  1906,  and  1400  (worth  £3680)  in  1908. 
Germany  exported  17,655  quintals  in  1905  and  20,780  (worth  £52,000)  in  1906. 

The  refined  crystalline  product  is  sold  at  48s.  to  56s.  per  quintal,  and  the  chemically 
pure  at  72s. 

It  is  best  prepared  commercially  by  the  Bauschlicher -Bauer  method  (1892-1905) 
from  commercial  pure  60  per  cent,  acetic  acid  (see  Tests  on  pp.  272  and  279)  and  pure 
litharge  containing  99  per  cent,  of  PbO.1  A  pitch-pine  vat  is  fitted  with  a  tight  cover 
with  three  apertures  :  the  central  one  for  the  shaft  of  a  wooden  stirrer,  another  for  a 
copper  cooling  coil  to  condense  the  acetic  acid  vapours,  and  the  third  for  the  neck  of 
a  large  wooden  hopper,  by  means  of  which  the  litharge  is  dropped  on  to  a  wooden  dis- 
tributing roller  provided  with  teeth  and  placed  under  the  lid.  The  required  quantity  of 
acetic  acid  is  heated  to  60°  by  a  copper  steam  coil  in  the  bottom  of  the  vat,  and  the  litharge 
gradually  added  in  the  proportion  of  103  kilos  per  100  kilos  of  60  per  cent,  acetic  acid  ; 
each  100  kilos  added  require  about  an  hour  to  dissolve  if  the  stirrer  is  kept  in  motion 
and  the  temperature  does  not  exceed  65°.  The  solution  has  a  density  of  70°  to  72°  Be. 
and,  if  it  does  not  show  an  acid  reaction,  it  is  slightly  acidified  with  acetic  acid,2  and 
the  mother -liquor  (35°  to  37°  Be.)  from  a  preceding  operation  added  in  such  amount  that 
the  density  becomes  50°  to  52°  Be.  The  solution  at  65°  is  then  allowed  to  clarify  in  a 
couple  of  tightly  closed  wooden  vats,  each  fitted  with  a  horizontal  rail  carrying  strips 
of  lead  dipping  into  the  liquid  so  as  to  remove  the  small  amount  of  copper  present.  After 
5  to  6  hours  the  solution  is  passed  through  a  cloth  filter-press  with  wooden  channels, 
and  is  then  left  to  crystallise  in  wooden  vessels  for  8  to  10  days — until  the  density 

1  It  should  contain  neither  iron,  which  would  colour  the  crystals,  nor  aluminium,  which  would  render  flrltation 
difficult. 

2  The  subsequent  crystallisation  is  rendered  difficult  if  the  solution  contains  basic  acetate,  the  presence  of  this 
being  inferred  from  the  turbidity  produced  on  mixing  a  little  of  the  liquid  with  an  equal  volume  of  1  per  cent, 
corrosive  sublimate  solution. 


SALTS  OF  ACETIC  ACID          287 

of  the  mother -liquor  falls  to  35°  Be.  in  winter  or  37°  in  summer.  After  the  liquid  has  been 
decanted,  the  mass  of  small  crystals  (more  concentrated  and  hotter  solutions  give  larger 
crystals)  is  treated  in  a  copper  centrifuge  and  dried  in  wooden  boxes  placed  in  a  vacuum 
apparatus  at  a  temperature  not  exceeding  300.1 

MONOBASIC  LEAD  ACETATE  (Subacetate  of  Lead),  (C2H302)2Pb  +PbO+H20, 
and  Dibasic  Lead  Acetate,  (C2H3O2)2Pb  +  2PbO,  are  obtained  by  melting  the  normal 
acetate  with  a  greater  or  less  proportion  of  litharge  (3:1  for  the  monobasic  salt)  on  the 
water-bath  ;  the  former  is  readily  soluble  and  the  latter  only  slightly  so  (1  :  18  at  20° 
and  1  :  5-5  at  100°)  in  water.  The  lead  acetate  of  the  pharmacopoeia  is  a  2  per  cent,  solution 
of  the  monobasic  salt,  and  is  used  as  a  medicine,  for  weighting  silk,  for  decolorising 
vegetable  juices,  and  for  preparing  white -lead  and  aluminium  acetate.  The  anhydrous 
salt  costs  104s.  per  quintal. 

NORMAL  CHROMIC  ACETATE,  Cr(C2H3O2)3  +  H2O,  is  obtained  from  calcium 
or  lead  acetate  and  chrome  alum  or  chromic  sulphate.  It  gives  a  violet  solution,  which 
becomes  green,  without  decomposing,  when  heated. 

Basic  Chromium  Sulphate  is  obtained  in  a  similar  way  from  basic  chromium  sulphate 
or  by  adding  ammonia  or  sodium  hydroxide  or  carbonate  to  a  solution  of  the  normal 
acetate.  The  basicity  increases  with  the  amount  of  alkali,  the  compound  O2(C2H302)50H, 
being  gradually  converted  into  Cr2(C2H302)2(OH)4  or  even  more  basic  salts  still.  The 
more  basic  the  acetate  the  more  will  it  decompose  on  boiling  and  the  more  readily  it 
will  serve  as  a  mordant  in  dyeing  or,  better,  in  printing,  since  the  reducing  action  of  the 
textile  fibres  or  of  .the  colouring-matters  or  of  other  organic  substances  added,  results 
in  the  separation  of  the  true  mordant,  Cr(OH)3,  which  forms  stable  lakes  with  the  dyes 
(alizarin,  hematin  from  log-wood,  &c.). 

Commercial  chromium  acetate  solutions  at  20°  Be.  are-  sold  at  32s.  per  quintal,  those 
of  40°  Be.  at  56s.,  and  the  solid  at  120s.  ;  the  chemically  pure  acetate  costs  8s.  per  kilo. 

STANNOUS  ACETATE,  Sn(C2H3O2)2,  is  obtained  by  treating  stannous  chloride 
with  lead  acetate  or  by  dissolving  freshly  precipitated  stannous  hydroxide  in  dilute  acetic 
acid.  Its  solution  is  used  as  a  mordant  or  corrosive  in  printing  cotton  with  substantive 
dyes  (see  this,  Part  III). 

The  20°  to  22°  Be.  solution  costs  48s.  per  quintal. 

NORMAL  CUPRIC  ACETATE  (Crystallised  Verdigris) ,  Cu(C2H3O2)2  +  H2O,  is 
obtained  by  dissolving  the  basic  acetate  (true  verdigris)  in  acetic  acid  or,  better,  by 
decomposing  copper  sulphate  solution  with  lead  acetate.  It  forms  clinorhombic,  dark 
green  prisms  and  is  readily  soluble  in  hot  water  (1:5)  or  in  alcohol.  It  is  used  in  medicine 
and  has  been  suggested  as  a  means  of  combating  the  Peronospora,  which  attacks  the 
vine.  It  costs  2s.  6d.  per  kilo. 

BASIC  COPPER  ACETATE  (Verdigris),  [>Cu(C2H3O2)OH]  +  5H2O,  is  obtained 
by  arranging  sheets  of  copper  with  flannel  saturated  with  hot  vinegar,  acetic  acid,  or 
acid  vinasse,  in  between.  The  crust  of  acetate  is  detached  from  the  plates  and  sold  in 
cakss  either  dry  or  with  30  par  cent,  of  moisture.  It  forms  blue  needles  or  scales,  which 
effloresce  in  the  air  and  become  green,  owing  to  loss  of  water. 

It  dissolves  only  slightly  in  water  and,  when  heated  in  the  dry  state,  gives  off  acetic 
acid  and  water.  When  pure,  it  is  completely  soluble  in  excess  of  ammonium  carbonate 
solution. 

It  was  formerly  used  as  a  colouring-matter,  but  is  now  used  for  the  preparation  of 
Schweinfurth's  green  (copper  aceto-arsenite),  Cu(C2H3O2)2,  3CuAs204,  by  mixing  with  the 
requisite  proportion  of  arsenious  anhydride  solution  ;  this  gives  a  beautiful  green  colouring- 
matter,  which  is  still  used  to  some  extent,  although  it  is  very  poisonous  owing  to  the 
evolution  of  hydrogen  arsenide  in  the  air. 

In  cakes  or  balls,  the  basic  acetate  costs  £6  per  quintal,  whilst  the  refined  powder 
costs  £8  10s. 

1  Analysis  of  lead  acetate  is  effected  by  dissolving  5  grms.  of  it  in  water,  precipitating  the  lead  with  a  known 
quantity,  in  slight  excess,  of  normal  sulphuric  acid,  making  up  to  250  c.c.  and  then  adding  a  volume  of  water  about 
equal  to  that  of  the  precipitate.  In  50  c.c.  of  the  nitrate,  the  sulphuric  acid  is  precipitated  with  barium  chloride, 
the  weight  of  the  resulting  barium  sulphate  giving  the  quantity  of  sulphuric  acid  which  has  remained  in  combination 
with  the  lead.  Another  50  c.c.  of  the  filtrate  is  titrated  with  normal  caustic  potash,  the  total  acidity  thus  found 
being  due  to  acetic  acid  and  excess  of  sulphuric  acid ;  deduction  of  the  latter  then  gives  the  amount  of  acetic 
acid  existing  in  combination  in  the  lead  acetate 


288  ORGANIC    CHEMISTRY 

PROPIONIC  ACID,   C3H602orCH3-CH2-COOH 

This  acid  is  obtained  by  hydrolysing  ethyl  cyanide  (see  p.  199)  and  also  by  the  action 
of  certain  micro-organisms  on  calcium  lactate.  It  is,  however,  usually  prepared  by 
fermenting  wheat-bran,  or  is  extracted  from  crude  pyroligneous  acid,  being  formed  in 
small  quantity  in  the  dry  distillation  of  wood  ;  it  can  also  be  easily  obtained  by  oxidising 
normal  propyl  alcohol  with  chromic  anhydride.  For  some  years  it  has  been  manufactured 
by  the  Effront  process  (see  p.  155)  from  the  residues  of  beetroot  molasses  :  1000  kilos 
of  molasses  yield  75  kilos  of  ammonium  sulphate  and  95  to  120  of  fatty  acids  consisting 
largely  of  propionic  acid  (see  also  section  on  Sugar). 

It  is  a  liquid  of  sp.  gr.  0-992  and  resembles  acetic  acid  in  odour  and  in  physical  and 
chemical  properties.  It  boils  at  141°  and  solidifies  at  —22°.  It  forms  crystalline  salts 
soluble  in  water,  and  its  esters  have  a  fruity  aroma.  Chemically  pure  propionic  acid 
costs  32s.  per  kilo,  and  the  commercial  acid  formerly  cost  14s.  6d.,  but  nowadays  the 
Effront  process  yields  a  much  cheaper  commercial  acid,  which  in  practice  may  be  used 
to  replace  formic  and  acetic  acids,  these  being  more  difficult  to  purify. 

BUTYRIC  ACIDS,   C4H8O2 

Two  isomerides  are  known  of  different  structures,  their  constitutional 
formulae  being  deduced  from  their  methods  of  synthesis. 

(1)  NORMAL  BUTYRIC  ACID  (Butanoic  or  Propylcarboxylic  Acid  or  Buty- 
ric Acid  of  Fermentation),  CH3 •  CH2  •  CH2  •  COOH,  is  the  more  important  of  the 
two  isomerides  and  exists  in  butter  in  the  form  of  glyceric  ester  to  the  extent 
of  4  to  5  per  cent.  It  is  formed  also  in  sweat  and  occurs  in  solid  excreta  and  in 
decomposing  cheese,  as  well  as  among  products  of  fermentation  of  glycerine. 

It  is  obtained,  not  by  synthesis  (see  p.  265),  but  by  the  butyric  fermenta- 
tion of  starch-paste  in  presence  of  a  little  tartaric  acid,  putrefied  meat  or 
cheese  being  added  after  a  few  days  (pure  cultures  of  special  bacteria  are  also 
used  at  the  present  time)  ;  it  is  also  obtained  from  acid  skim  milk  by  treat- 
ment with  powdered  marble  and  converting  the  calcium  lactate  into  calcium 
butyrate,  then  into  the  sodium  salt,  and  finally,  by  means  of  H2S04,  into 
the  free  acid.  It  is  also  obtained  from  molasses  residues  by  Effront's  process 
(see  above). 

It  forms  an  oily  liquid,  sp.  gr.  0-958  at  14°,  boiling  at  162°  and  solidifying 
in  scales  at  19°.  It  dissolves  in  water,  alcohol,  or  ether,  burns  with  a  bluish 
flame,  and  gives  crystalline,  slightly  soluble  salts. 

Calcium  Butyrate,  (C4H702)2Ca  +  H2O,  is  less  soluble  in  hot  than  in  cold 
water. 

The  esters  have  pleasant,  fruity  odours,  and  are  used  to  produce  artificial 
rum.  Commercial  concentrated  butyric  acid  costs  4s.  per  kilo  ;  the  50  per 
cent,  acid  2s.  6d.  ;  and  the  chemically  pure  (100  per  cent.)  5s.  I0d.  The 
concentrated  esters  are  sold  at  2s.  Qd.  to  5s.  per  kilo. 

PT-T 

(2)  ISOBUTYRIC  ACID  (2-Methylpropanoic  or  Dimethylacetic    Acid),  ;:::3>CH- 

Crla 

COOH,  resembles  the  preceding  acid,  but  is  less  soluble  in  water.  It  boils  at  154°  and 
solidifies  at  —79°,  and  occurs  free  in  arnica  and  carob  roots  and  as  ester  in  chamomile  oil. 
It  can  be  obtained  by  the  ordinary  synthetic  processes  and  is  less  resistant  than  the 
normal  acid  to  oxidising  agents.  The  pure  acid  costs  40s.  per  kilo  and  the  commercial  acid 
about  one-half  as  much. 

The  Calcium  Salt,  Ca(C4H7O2)2,  is  more  soluble  in  hot  water  than  in  cold. 

VALERIC  ACIDS,   C5H10O2 

The  four  isomerides  predicted  by  theory  are  known. 

(1)  NORMAL  VALERIC  ACID  (PentanoicorPropylacetic  Acid),CH3-  [CH2]3-COOH, 
is  a  dense  liquid  (sp.  gr.  0-956  at  0°),  boiling  at  185°  and  solidifying  at  —58-5°.  It  is 
obtained  synthetically  from  propylmalonic  acid  or  butyl  cyanide  and  is  met  with  in 


HIGHER    FATTY    ACIDS  289 

pyroligneous  acid  ;  it  is  slightly  soluble  in  water.  The  pure  product  costs  5d.  per 
gramme. 

CH 

(2)  ISOVALERIC  ACID,  ):u3>CH.CH2-COOH,  is  found  free  or  in  the  form  of 

Crl3 

esters  in  animals  (fat  of  the  dolphin,  sweat  of  the  feet,  &c.)  and  vegetables  (roots  of 
Valeriana  officinalis),  and  from  the  latter  can  be  extracted  by  boiling  with  solutions  of 
soda  or  by  distilling  with  water  containing  phosphoric  acid.  It  is  a  liquid  (sp.  gr.  0-947 
at  0°),  bailing  at  174°  and  solidifying  at  — 15°  ;  it  has  a  disagreeable  odour  of  stale  cheese. 
It  is  often  obtained  by  oxidising  fusel  oil  with  dichromate  and  sulphuric  acid.  The  pure 
acid  costs  96s.  per  kilo. 

Its  esters  are  used  as  artificial  fruit  essences  and  cost  from  10s.  to  16s.  per  kilo. 

(3)  ETHYLMETHYLACETIC  ACID  (Methyl-2-butanoic  or  Active  Valeric  Acid), 

PTT 

s  ^>CH-COOH,  is  optically  active  as  it  contains  an  asymmetric  carbon  atom  (see 
C2H5 

p.  18)  ;  it  occurs  naturally  with  iso valeric  acid.  The  inactive  mixture  of  the  two 
oppositely  active  acids  can  be  resolved  into  its  active  components  by  means  of  the 
brucine  salts.  It  boils  at  174°. 

(4)  TRIMETHYLACETIC  ACID  (Dimethyl  -  2  -  propanoic  or  Pivalic  Acid), 
(CH3)3  :  C-COOH,is  a  solid,  m.pt.  35°,  b.pt.  163°.  It  has  an  odour  resembling  that  of 
acetic  acid,  and  it  can  be  obtained  from  tertiary  butyl  cyanide. 

HIGHER  ACIDS 

Of  the  numerous  isomerides  theoretically  possible  and  of  the  many  actually 
known,  mention  will  be  made  only  of  some  of  the  more  important  which  occur 
naturally  and  are  usually  of  the  normal  structure  and  with  even  numbers  of 
carbon  atoms. 

NORMAL  CAPROIC  ACID,  C6H12O2  or  CH3-[CH2]4-COOH,  is  a  liquid  boiling  at 
205°  and  solidifying  at  —1-5°.  It  is  volatile  in  steam,  has  an  unpleasant  odour  like 
rancid  butter,  #nd  is  found  free  in  Limburger  cheese  and  coco -nut  oil,  and  as  glyceride 
in  goats'  butter.  It  is  formed  on  oxidising  proteins  or  higher  fatty  acids  (unsaturated). 

HEPTOIC  ACID  (CEnantic  Acid),  C7H14O2  or  CH3-[CH2]5-COOH,  is  formed  on 
oxidation  of  castor  oil  or  wnanthaldehyde.  It  is  a  liquid  boiling  at  220°  and  solidifying 
at  —20°.  It  differs  from  its  lower  homologues  by  exhibiting  a  slight  odour  of  fat. . 

CAPRYLIC  ACID  (Octoic  Acid),  C8H16O2  or  CH3-[CH2]6  COOH,  solidifies  at  16-5° 
and  boils  at  237-5°  ;  it  is  found  in  coco -nut  oil  and  as  glyceride  in  ordinary  butter  and  that 
of  goats. 

NONOIC  ACID  (Pelargonic  Acid),  C9H18O2  or  CH3-[CH2]7-COOH,  is  a  liquid  boiling 
at  254°.  It  is  formed  by  oxidising  oleic  acid  or  by  decomposing  the  ozonide  of  oleic  acid 
(Molinari  and  Soncini,  1905)  with  dilute  alkali.  In  nature  it  occurs  in  Pelargonium 
roseum. 

DECOIC  ACID  (Capric  Acid),  C10H2oO2  or  CH3-[CH2]8-COOH,  is  a  solid,  melting 
at  31-4°  and  boiling  at  200°  under  100  mm.  pressure.  It  also  is  found  in  coco-nut  oil 
and  goats'  butter. 

UNDECOIC  ACID,  CUH22O2  or  CH3-[CH2]9-COOH.  Distillation  of  castor  oil  under 
reduced  pressure  yields  the  unsaturated  undecenoic  acid,  C11H20O2,  which  gives  undecoic 
acid  on  reduction  with  hydrogen.  It  melts  at  28°  and  boils  at  212°  (100  mm.). 

LAURIC  ACID,  C12H2402  or  CH3-[CH2]10-COOH,  is  a  solid,  melting  at  44°  and 
boiling  at  225°  (100  mm.)  ;  it  occurs  in  the  form  of  glyceride  in  laurel  berries. 

MYRISTIC  ACID,  C14H28O2  or  CH3-[CH2]12-COOH,  melts  at  54°  and  boils  at  248° 
(100  mm.).  It  is  found  as  glyceride  (myristin)  in  the  nutmeg  (Myristica  moschata)  and 
in  ox-gall,  and  abounds  in  the  seeds  of  Virola  Venezuelensis. 

PALMITIC  ACID  (Hexadecoic  Acid),  C16H32O2  or  CH3- [CH2]14-COOH, 
forms  a  moderately  transparent  white  mass,  which  readily  softens  and  melts 
at  62-6°.  It  is  insoluble  in  water  and  crystallises  from  alcohol  in  scales  or 
needles.  It  boils  unchanged  at  268°  under  100  mm.  pressure,  or,  with  partial 
decomposition,  at  339°  to  356°  under  the  ordinary  pressure. 

ii  19 


290  ORGANIC    CHEMISTRY 

It  is  one  of  the  normal  components  of  animal  and  vegetable  fats,  in  which 
it  occurs  as  a  glyceride  (palmitin),  and  is  easily  obtained,  together  with  oleic 
acid,  from  palm  oil  by  hydrolysing  and  then  decomposing  the  soap  formed  ; 
the  palmitic  acid  is  then  isolated  by  fractional  crystallisation.  Japanese 
vegetable  wax  consists  almost  exclusively  of  palmitin.  The  industrial  treat- 
ment of  fats  and  oils  for  the  extraction  of  the  corresponding  fatty  acids 
(palmitic,  stearic,  and  oleic)  will  be  described  in  the  section  dealing  with  the 
manufacture  of  soap  and  candles. 

Commercial  palmitic  acid  is  also  known  by  the  inaccurate  name  of  palmitin 
and  is  likewise  manufactured  by  melting  oleic  acid  with  potassium  hydroxide 
(Varrentrapp's  reaction) :  C18H3402  +  2KOH  =  H2  +  CH3-  C02K  +  C16H3102K 
(potassium  palmitate,  which  gives  palmitic  acid  under  the  action  of  mineral 
acid). 

Its  alkali  salts  (soaps)  are  soluble  in  alcohol  or  water,  but  considerable 
dilution  of  the  aqueous  solutions  results  in  the  separation  of  an  acid  salt  and 
liberation  of  alkali.  Whilst  in  alcoholic  solution  these  soaps  show  virtually 
normal  molecular  weights,  the  aqueous  solutions  show  no  rise  in  the  boiling-' 
point,  the  soaps  thus  behaving  as  colloids  in  these  solutions  (see  vol.  i,  p.  102). 
The  other  salts  (palmitates)  are  insoluble  in  water  and,  in  some  cases,  soluble 
in  alcohol ;  mineral  acids  liberate  palmitic  acid  from  them. 

The  commercial  acid  costs  £4  per  quintal,  the  refined  product  £8,  and  the 
doubly  refined  25s.  Qd.  per  kilo. 

MARGARIC  ACID,  C17H34O2  or  CH3- [CH2]15-COOH,  was  for  a  long 
time  thought  to  exist  in  fats,  but  it  has  been  shown  that  a  mixture  of  palmitic 
(C18)  and  stearic  (C16)  acids  was  being  dealt  with.  Synthetically  it  can  be 
obtained  by  hydrolysing  cetyl  cyanide,  C16H33-CN,  and  by  other  methods. 
It  melts  at  60°  and  distils  unchanged  at  277°  under  100  mm.  pressure. 

STEARIC  ACID,  C18H36O2  or  CH3- [CH2]16-COOH,  which  is  improperly 
known  commercially  as  stearine  (and  is  then  mixed  with  palmitic  acid),  and 
its  separation  from  oleic  acid  will  be  described  when  dealing  with  candles. 

As  glyceride,  it  occurs  with  that  of  oleic  acid  as  one  of  the  principal 
constituents  of  fats  and  oils,  and  is  usually  prepared  industrially  from  beef 
suet.- 

Synthetically  it  can  be  obtained  by  the  reducing  action  of  hydrogen  on 
oleic  acid  (see  this),  and  the  constitution  of  the  latter  being  known,  that  of 
stearic  acid  follows  directly.  Industrial  application  is  now  made  of  this 
process,  the  catalytic  reaction  of  Sabatier  and  Senderens  being  employed. 

It  forms  a  somewhat  soft  white  mass,  melting  at  69-3°,  and  crystallises 
from  alcohol  in  shining  scales.  It  boils  unchanged  at  287°  under  100  mm. 
pressure  or  with  partial  decomposition  at  359°  to  383°  under  the  ordinary 
pressure. 

It  is  insoluble  in  water,  soluble  slightly  in  light  petroleum,  and  more 
readily  in  alcohol,  ether,  benzene,  or  carbon  disulphide. 

Its  salts  behave  like  those  of  palmitic  acid.  The  lead  salts  of  these  high 
fatty  acids  are  obtained  by  boiling  the  fats  or  oils  with  lead  oxide  and  water. 
This  lead  soap  is  used  for  the  preparation  of  lead  plaster,  and  is  used  in  the 
manufacture  of  varnish.  Stearic  acid  made  into  a  paste  with  gypsum  forms 
a  kind  of  artificial  ivory. 

Italy  imported,  especially  from  France,  England,  and  Belgium,  17,080 
quintals  of  stearic  acid  in  1906  ;  12,50P  in  1908  ;  and  14,450  (of  the  value 
of  £63,570)  in  1910. 

CEROTIC  or  CEROTINIC  ACID,  C27H54O2,  is  found  free  in  beeswax  (together  with 
Melissic  Acid,  C30H60O2),  as  ester  in  Chinese  wax  and  as  glyceride  in  the  fat  of  raw 
wool.  It  melts  at  78-5°  and  is  converted  by  oxidising  agents  into  various  acids  with  lower 
molecular  weights. 


PREPARATION    OF    UNSATURATED    ACIDS     291 


II.  UNSATURATED  MONOBASIC  FATTY  ACIDS 
A.  OLEIC  or  ACRYLIC  SERIES,  CWH2«_2O2  (Olefine-Carboxylic  Acids) 


Empirical 
formula 

Name  of  acid 

Constitutional  formula 

Melting- 
point 

Boiling- 
point 

C3H402 

Acrylic  acid                             » 

CH2:  CH-CO2H 

13° 

140° 

rVinylacetic  acid  .       . 

CH2:  CH-CH2-CO2H 

-39° 

163° 

C4H802 

r    .      .    J  Solid  crotonic  acid 
IC   I  Liquid  crotonic  acid 

CH3-CH  :  CH-CO2H  (cis) 
CH3-CH  :  CH-CO-H  (trans) 

72° 
15-5° 

181° 
169° 

vMetacrylic  acid    . 

CH2:  C(CH3)-CO2H 

16° 

161° 

/'Angelic  acid    . 

CH8—  C—  CO2H 

(8  structural  isomerides  and  one    I 

II 

45° 

185° 

CjH,O2 

stereoisomeride)                   j 

CH3—  C—  H 

VTiglic  acid 

CH3  C—  CO2H 

II 

65° 

198-5° 

H—  C—  CH3 

C,H100.2 

(Not  all  stereoisomcrides  known)  Pyrotcrebic  acid    . 

(CH3)2:C:CH-CH2-CO2H 

—  15° 

207° 

C,H,2O2 

Do.                          -y-Allylbutyric  acid  . 

CH2:CH-[CH2]4-CO2H 

— 

226° 

C,H120, 

Do,                          Teracrylic  acid 

(CH3),  :  C:  C(CH3)-CH2-CO2H 

— 

218° 

Ci0HlsO, 

Do.                          Citronellic  acid 

CH2:C(CH3)-[CH2]4-CH(CH3)-CH2-CO2H 

— 

152" 

(18  mm.) 

CUH2002 

Do.                          Undeceiioic  acid    . 

CHS:CH-[CH2]S-CO2H 

24-5° 

213-5° 

(100  mm.) 

Ci6H30O2 

Do.                          Hypogseic  acid 

CH3-[CH2],-CH:CH-[CH2]6-CO2H 

— 

— 

rOleic  acid 

CH3-[CH2],-CH:CH-[CH2]7-CO2H  (cis) 

14° 

223° 

C18H3402 

Do. 

(10  mm.) 

vElaidic  acid  . 

CH3-  [CH2j,-CH:CH-  [CH2],-CO2II(</-<m*) 

51° 

225° 

(10  mm.) 

C18H3402 

Do.                       /  Iso-oleic  acid 

CHVfCHsVCH:  CH-  [CH2]e-CO2H  (?) 

44° 

— 

\  Aa|3-oleic  acid 

CH3-[CH2]14-CH  :  CH-CO2H 

•58° 

— 

I  Erucic  acid  . 

CHj-LCHjlv-CH-CH-tCHjlu-CO-iH 

34° 

254-5° 

(10  mm.) 

C221I,202 

Do.                      -<  Brassidic  acid 

CH,  •  [CH2],  •  CH  :  CH  •  [CH,]U  •  COaH 

65° 

256° 

(10  mm.) 

^Isoerucie  acid 

CH3-[CH2]8-CH:  CH-  [CH2]10-CO2H  (?) 

55° 

— 

Their  importance  is  due  to  the  fact  that  certain  of  them  occur  as  glycerides 
in  many  fats  and  oils. 

GENERAL  PROCESSES  OF  FORMATION.  The  following  are  the  most 
important  of  these  : 

(1)  The  unsaturated  halogen  derivatives  of  unsaturated  alcohols  can  be 
transformed  into  cyanogen  derivatives,  which  give  the  corresponding  acids 
on  hydrolysis  (see  p.  199)  : 


CH2:CH-CH2-OH 
CH2:CH-CH2-CN- 


CH2:CH-CH2-Br — > 
CH2:CH-CH2-COOH. 


(2)  Oxidation  of  unsaturated  alcohols  and  aldehydes  with  mild  oxidising 
agents  (silver  oxide  or  the  oxygen  of  the  air)  which  do  not  attack  the  dcuble 
linking  ;  allyl  alcohol  and  acrolei'n  give  acrylic  acid. 

(3)  Of  general  use  is  Perkin's  reaction  applicable  especially  to  the  aromatic 
series,  but  of  service  also  for  the  fatty  series  :    when  an  aldehyde  is  heated 
with  the  sodium  salt  of  a  saturated  fatty  acid  in  presence  of  an  anhydride 
(e.g.  acetic  anlrydride)  and  then  treated  with  water,  the  resulting  products 
are  the  saturated  acid  corresponding  with  the  aldehyde  used  and  an  unsaturatc  d 
acid,  which  always  has  the  double  linking  between  the  a-  and  /3-carbon  atoms, 
the  a-carbon  atom  being  that  adjacent  to  the  carbonyl  group,  CO.     If  the 
chain  united  to  the  aldehyde  group  is  denoted  by  R,  the  intermediate  phases 
of  this  reaction  are  probably  as  follow  : 

(a)  R  •  CHO  +  CH3  •  CO  •  0  •  CO  •  CH3  give,    by  aldol  condensation, 
R-CH(OH)-CH2-CO-0-CO-CH3;      this    unstable    compound    immediately 


292  ORGANIC    CHEMISTRY 

separates  water,  giving  R  •  CH  :  CH  •  CO  •  O  •  CO  •  CH3,  treatment  of  this  product 
with  water  yielding  the  unsaturated  acid  : 

(6)  R-CH  :  CH-CO-0-CO-CH3+H20  =  CH3-COOH  +  R-CH  :  CH-COOH. 

It  is  evident  that,  if  only  one  hydrogen  atom  is  united  to  the  carbon  atom 
adjacent  to  the  carbonyl  group  of  the  original  anhydride,  the  first  phase  of 
the  reaction,  but  not  the  second,  will  be  possible,  so  that  only  a  saturated 
hydroxy-acid  will  be  obtained  : 

R-CHO  +  CH-CO-0-O-CH  +  H20  = 


R-CH(OH)-C-COOH  +  (CH3)2 :  CH-COOH. 

/\ 
CH3CH3 

The  presence  of  the  sodium  salt  of  the  iatty  acid  is  indispensable  to  all 
these  reactions,  but  its  function  has  not  yet  been  explained. 

(4)  Similar  to  Perkin's  synthesis  is  the  reaction  between  an  aldehyde  (or 
an  a-ketonic  acid,  R-CO-COOH,  which  possibly  loses  C02  and  thus  gives 
an  aldehyde)  and  malonic  acid  in  presence  of  glacial  acetic  acid,  a  mixture 
of  unsaturated  monobasic  acids  with  the  double  linking  in  the  a  /3-  or  /3  y- 
position  being  obtained  and  C02  split  off : 


(a]  R-CH2-CHO  +  CH2 

Malonic  acid 

(6)  2R  •  CH2  •  CH(OH)  - 

2C09  +  2H20  +  R-CH2-CH:  CH-COOH  +  R-CH  :  CH-CH2-COOH. 

a  /3-acid  £  7-acid 

It  should  be  noted  that  this  reaction  always  gives  also  a  condensation 
product  of  1  mol.  of  the  aldehyde  and  2  mols.  of  malonic  acid,  this  product 
then  losing  C02  and  yielding  a  saturated  dibasic  acid  : 


CH(COOH)2  ~  CHa  •  COOH 

(5)  When  monohalogenated  saturated  fatty  acids   (especially  those  with 
the  halogen  in  the  j3  -position)  are  heated  with  alcoholic  potash  or  sometimes 
even  with  water  alone,  a  molecule  of  halogen  hydracid  is  eliminated  and  the 
unsaturated  acid  formed   (similar  to  the  reaction  giving  unsaturated  hydro- 
carbons, p.  88)  :     • 

CH2I-CH2-COOH  =  HI  +  CH2  :  CH-COOH. 

/3-Iodopropionic  acid  Acrylic  acid 

(6)  By  separating  a  molecule  of  water  from  monohydroxy  -acids  by  means 
of  distillation  or  a  dehydrating  agent  (H2S04,  PC15,  P205)  or  sometimes  by 
merely  heating  with  caustic  soda  solution,  the  unsaturated  monobasic  fatty 
acids  are  formed  : 

CH3-CH(OH)-CH2-COOH  =  H20  +  CH3-CH  :  CH-COOH. 

/3-Hydroxybutyric.  acid  Crotonic  acid 

GENERAL  PROPERTIES.  The  number  of  double  bonds  is  ascertained 
by  the  same  methods  as  are  applied  to  unsaturated  hydrocarbons  (see  pp.  88 
and  89)  —  by  addition  of  either  halogen  or  ozone.  These  unsaturated  acids 
are  more  energetic  than  the  corresponding  saturated  acids  with  the  same 


PROPERTIES    OF    UNSATURATED    ACIDS     293 

numbers  of  carbon  atoms,  as  can  be  seen  from  their  ionisation  constants 
(vol.  i,  p.  92).  They  are  more  easily  oxidisable  than  the  saturated  acids, 
powerful  oxidising  agents  rupturing  the  carbon  atom  chain  at  the  double 
linking,  the  position  of  which  can  hence  be  established  by  a  study  of  the  com- 
positions of  the  two  acids  formed. 

When  boiled  with  10  per  cent,  caustic  soda  solution,  unsaturated  acids 
with  a  double  linking  (A)  in  the  )3y-position  undergo  displacement  of 
this  linking  with  the  partial  formation  of  unsaturated  acids  with  a 
double  bond  in  the  a/3-position  (Fittig,  1891-1894)  ;  this  is  formed  from 
an  intermediate  hydroxy-acid,  an  equilibrium  being  established  as  indicated 
below  : 

R-CH  :  CH-CH2-COOH  +  H20  ^  R-CH2-CH(OH)-CH2-COOH  ±; 

/3  y-acid  /3-Hydroxy-acid 

H20  +  R-CH2-CH  :  CH-COOH. 

a  /3-acid 

In  general  this  reaction  preponderates  towards  the  formation  of  the  a /3-acid 
and  not  vice  versa,  the  carboxyl  group  apparently  exerting  an  attraction  on 
the  double  linking. 

When  an  unsaturated  acid  is  fused  with  caustic  soda  or  potash,  the  double 
linking  is  displaced,  giving  an  a  /3-acid,  the  new  molecule  immediately  splitting 
at  the  double  bond,  the  resultant  products  being  acetic  acid  and  another 
saturated  acid.  This  displacement  of  the  double  linking  was  unknown  until 
a  few  years  ago,  so  that  oleic  acid,  for  example,  which  gives  palmitic  and 
acetic  acids  quantitatively  when  fused  with  potash,  was  regarded  as  an 
a  /3-unsaturated  acid.  It  has,  however,  been  shown  (see  later]  that  the  double 
bond  of  oleic  acid  is  in  the  middle  of  the  molecule,  the  action  of  the  potash 
causing  displacement  of  this  bond  before  the  molecule  is  resolved  : 

CH3-  [CH2]7-CH  :  CH-  [CH2]7-COOH — *  CH3-  [CH2]14-CH  :  CH-COOH 

Oleic  acid  o./3-Oleic  acid 

CH3-  [CH2]14-CH  :  CH-COOH  +  2KOH  +  0  = 
CH3-  [CH2]14-COOK  -(-  H2O  +  CH3-COOK. 

Potassium  palmitate 

The  acids  of  the  oleic  and  acrylic  series,  and  unsaturated  compounds  in 
general,  exhibit  a  tendency  to  polymerise ;  the  mere  action  of  sodium  alkoxide 
on  the  crotonic  esters  produces,  in  addition  to  other  reactions,  the  following 
change  : 

CH3  C02-CH3  CH3  C02'CH3 

CH  CH  CH  CH2 

II            +11                                     II  I 

CH  CH  C CH 


CO,- 


j         CH3  CO2*CH3         C.tL3 

Methyl  crotonate  Methyl  dicrotonate 

Instances  of  stereoisomerism  among  unsaturated  compounds  have  already 
been  described  on  pp.  16  and  17,  and  it  is  only  necessary  to  state  here  that,  of 
the  two  stereoisomerides  corresponding  with  one  and  the  same  formula,  one 
is  less  stable  than  the  other,  into  which  it  is  easily  and  directly  transformed 
(the  inverse  change  only  takes  place  indirectly)  by  mere  heating  or  by  the 
action  of  concentrated  sulphuric  acid,  caustic  soda,  a  little  nitrous  acid,  or 
a  trace  of  bromine  in  the  presence  of  light. 


294 


ACRYLIC  ACID  (Propenoic  Acid) 
C3H4O2  or  CH2  :  CH-COOH 

This  acid  was  prepared  for  the  first  time  (Redtenbacher,  1843)  by  oxidising  acrolein 
CH2  :  CH  •  CHO,  with  silver  oxide.  It  is  now  more  readily  obtained  indirectly,  by  the 
action  ot  gaseous  hydrogen  chloride,  which  gives /3-chloropropaldehyde,.CH2Cl-CH2- CHO, 
this  being  converted  by  nitric  acid  into  the  corresponding  /3-chloropropionic  acid, 
CH2C1-CH2-COOH  ;  when  the  last  compound  is  boiled  with  a  solution  of  alkali,  it  loses 
HC1,  yielding  acrylic  acid. 

Another  convenient  synthesis  is  the  following  :  allyl  alcohol  (a,  see  below)  with  bromine 
gives  dibromopropyl  alcohol  (b),  which,  on  oxidation,  yields  a/3-dibromopropionic  acid(c), 
and  this,  by  the  action  of  either  zinc  in  presence  of  dilute  sulphuric  acid  (or  water)  or 
reduced  copper  (containing  iron)  loses  bromine  and  gives  acrylic  acid  (d) : 

CH2  CH2Br  CH2Br  CH2 

II  I  I  II 

CH          - — >      CHBr    '  — >      CHBr       — *     CH 

.CH2.OH  CH2-OH  COOH  COOH 

a  b  c  d 

Acrylic  acid  is  a  liquid  soluble  in  water  and  having  a  pungent  odour  almost  like  that 
of  acetic  acid  :  it  has  the  sp.  gr.  1-0621  at  16°,  boils  and  polymerises  at  about  140°,  and 
when  cooled  forms  tabular  crystals  melting  at  13°.  With  nascent  hydrogen,  it  is  trans- 
formed into  propionic  acid,  whilst,  when  fused  with  potash,  it  gives  acetic  and  formic 
acids. 

CROTONIC  ACIDS,  C4H6O2 

Isomeric  unsaturated  acids  of  this  formula  are  possible  theoretically — two  stereo- 

isomerides  and  the  others  structural  isomerides.  The  following  acids  have  actually  been 
prepared  : 

(a)  CH2  :  CH-CH2.COOH,  vinylacetic  acid  ; 

H— C— C02H 

(ba)          ||  ,  cis  /3-methylacrylic  acid  (solid  crotonic  acid) ; 

H— C— CH3 

H— C— C02H 

(&/3)  ,  trans  /3-methylacrylic  acid  (liquid  crotonic  acid)  ; 

CH3— C— H 

CH 
(c)  CH2  :  Ck^-^-JL-p  methylmethyleneacetic  or  a-methylacrylic  acid. 


With  the  general  formula,   C4H6O2,  there  corresponds  also  ethylene-acetic  cr  tri- 

rnethylenecarboxylic  acid,     |       NCH-COOH,  but  this  does  not  belong  to  the  olefine- 

CH2/ 

carboxylic  acids  as  it  contains  no  double  linking,  and  it  will  therefore  be  studied  with 
the  cyclic  compounds. 

(a)  VINYLACETIC  ACID,    CH2  :  CH-CH2.CO2H,has  been  prepared,  only  recently, 
by  distilling  /3-hydroxglutaric  acid  in  a  vacuum  : 

O-tL2  •  OO2-rL  C.H2 

CH-OH  C02  +  H20  +  CH 

CH2-CO2H  CH2-C02H 

and  also  by  first  brominating  (with  bromine  dissolved  in  CS2)  allyl  cyanide,  hydrolysing 
the  product,  and  finally  removing  the  bromine  by  means  of  zinc  dust  and  alcohol,  thus  : 


CROTONIC  ACIDS  295 

CH2  CH2Br  CH2Bri  CH2 

ii         r  r  ir 

CH        —  >       CHBr      -  >  CHBr      -  >  CH 


CN  CN  C02H  C02H 

Vinylacetic  acid  is  a  very  hygroscopic  liquid,  which  solidifies  when  cooled  to  a  low 
temperature  ;  it  melts  at  —39°  and  boils  at  163°.  Its  calcium  salt,  (C4H5O2)2Ca,  H2O. 
crystallises  from  water  in  shining  needles. 

When  boiled  with  5  per  cent,  sulphuric  acid  solution,  it  is  transformed  into  the  solid 
crotonic  acid,  CH2  :  CH  •  CH2  .  COOH  —  >  CH3  .  CH  :  CH  •  COOH. 

This  transposition  of  the  double  linking  is  also  effected  by  boiling  with  caustic  soda 
solution,  but  in  this  case,  a  preponderance  of  /3-hydroxy  butyric  acid  is  formed  at  the 
same  time. 

H—  C—  C02H 
(5a)  ORDINARY  or  SOLID  CROTONIC  ACID,  ||  (cis  ft-methylacrylic 

H—  C—  CH3 

acid  or  cis  ethylideneacetic  acid;  also  wrongly  known  as  a-crotonic  acid).  Its  constitution 
follows  from  its  synthesis  from  a-bromobutyric  acid  (or  rather  its  ester)  by  the  elimi- 
nation of  HBr  under  the  action  of  alcoholic  potash  : 

CH3.CH3.CHBr.CO2H  -  HBr  +CH3.CH  :  CH-C02H. 

Prom  water  (solubility  1  in  12)  the  acid  crystallises  in  shining  needles  melting  at 
71°  to  72°  ;  it  boils  at  181°  to  182°,  has  an  odour  resembling  that  of  butyric  acid,  and  is 
found  free  in  crude  pyroligneous  acid.  Its  calcium  and  barium  salts  contain  no  water 
of  crystallisation  and  are  very  soluble  in  water. 

When  gently  oxidised  in  alkaline  solution  with  permanganate,  it  gives  afi-dihydroxy- 
butyric  acid,  CH3-CH(OH)-CH(OH)-C02H,  which  cannot  form  a  lactone,  so  that  neither 
of  its  hydroxyl  groups  is  in  the  y-position  ;  the  double  linking  of  the  crotonic  acid  must 
hence  be  between  the  a-  and  /3  -carbon  atoms.  When  halogen  hydracids  are  added  to  it, 
the  halogen  goes  to  the  ft  -position.  With  nascent  hydrogen  it  gives  butyric  acid. 

H—  C—  CO2H 

(6/3)  LIQUID  CROTONIC  ACID,  ||  (trans  fl-methylacrylic  acid  or  iso- 

CH3—  C—  H 

crotonic  or  allocrotonic  acid  ;  known  improperly  as/3-crotonic  acid).  This  acid  is  prepared 
from  ethyl  acetoacetate,  which,  with  PC15,  gives  probably  a  chloracetic  ester,  the  latter 
losing  a  molecule  of  HC1  and  yielding  the  two  stereoisomeric  chloroisocrotonic  acids  (or  the 
corresponding  ethyl  esters)  ;  these  two  isomerides  can  be  separated,  the  one  formed  in 
greater  proportion  being  readily,  and  the  other  difficultly,  distilled  in  steam.  The  latter 
gives  solid,  and  the  other  liquid,  crotonic  acid  on  reduction  with  sodium  amalgam  : 

(a)  CH3  •  CO  •  GIL,  .  CO  •  OC2H5  +  PC15  =  CH3  -  CC12  •  CH2  •  CO  •  OC2H5  +  POC13. 

Ethyl  acetoacetate  Intermediate  product 

(b)  CH3  .  CC12  •  CH2  •  CO  •  OC2H5  =  CH3  •  CC1  :  CH  •  CO  •  OC2H5  +  HC1. 

Two  stereoisomerides 

(c)  CH3  .  CC1  :  CH  .  CO  .  OC2H5  +  H2  =  CH3  •  CH  :  CH  •  CO  •  OC2H5  +  HC1. 

Ethyl  ester  of  crotonic  acid 

The  isocrotonic  acid  thus  obtained  is  liquid,  but  is  not  pure,  as  it  always   contains 
ordinary  crotonic  acid  and  a  little  tetrolic  acid,  CH3-C  :  C-CO2H.     Only  within  recent 
1  This  |3  y-dibromobutyric  acid,  when  boiled  with  water,  gives  a  p-bromobutyrolactone  : 
CHjBr  CH2  -  O 

CHBr  =  HBr  +  CHBr 

I  I 

CH2-COOH  CH2  -  CO 

Lactones  are  not  usually  formed  by  acids  brominated  in  the  a-  or  /3-position,  but  only  with  those  where  th& 
bromine  atom  is  in  the  y-position.  it  may  hence  be  concluded  that  the  double  linking  in  vinylacctic  acid  is  also 
in  the  /3  y-position,  since  its  brominated  derivative  gives  a  lactone,  which  is  formed  only  when  there  is  halogen  in. 
the  y-position. 


296  ORGANIC    CHEMISTRY 

years  (1895  and  1904)  has  it  been  separated  from  these  admixtures,  either  by  means  of 
its  sodium  salt,  which  is  more  soluble  in  alcohol,  or  by  means  of  its  quinine  salt,  which  is 
less  soluble  hi  water  than  that  of  crotonic  acid. 

After  such  purification  it  is  found  that  pure  liquid  crotonic  acid  forms  crystals  melting 
at  15-5°  and  boiling  at  169°  under  the  ordinary  pressure  or  at  74°  under  a  pressure  of 
15  mm.  The  calcium  salt,  (C4H6O2)2Ca,  3H20,  forms  large  prisms,  and  the  barium  salt, 
(C4H5O2)2Ba,  H20,  large  plates. 

When  heated  above  100°,  it  is  converted  partially  into  normal  crotonic  acid,  and  in  order 
to  avoid  this  change  during  distillation  the  operation  is  carried  out  in  a  vacuum  ;  the 
transformation  is  instantaneous  and  quantitative  in  presence  of  a  trace  of  bromine  in 
aqueous  solution  or  of  carbon  disulphide  under  the  influence  of  direct  sunlight. 

That  the  structure  of  isocrotonic  acid  is  the  same  as  that  of  crotonic  acid  and  not  of 
vinylacetic  acid  is  supported  by  the  fact  that  isocrotonic  acid  gives  no  lactonic  derivative 
(see  above)  and  also  by  the  fact  that  the  peroxyozonides  of  these  two  acids,  obtained  by 
Harries  and  Langheld  (1905)  by  the  action  of  ozonised  oxygen  and  having  the  structure 

CH3-CH — CH-C^  ,  give  with  water  the  same  decomposition  products,  namely, 

O-O-O 
hydrogen  peroxide,  acetaldehyde,  and  glyoxylic  acid,  CHO  •  C02H. 

(c)  METHYLMETHYLENEACETIC  ACID  (a-Methylacrylic,  Metacrylic  or  Methyl- 

CH 

propenoic  Acid),  CH2  :  C<T^/^  \T,  can  be  obtained  by  separation  of  water  from  a-hydroxy- 
^\»U2ti 

isobutyric  acid  and  also  by  elimination  of  a  molecule  of  HBr  from  a-bromoisobutyric  acid  : 


CH3.C.Br.C02H  =  HBr  +  CH2  : 

i  L/U2Jtl 

CH3 

This  synthesis  indicates  the  constitution  of  metacrylic  acid,  which  is  confirmed  by  the 
observation  that  reduction  of  this  acid  by  means  of  sodium  amalgam  gives  isobutyric 
acid,  this  having  a  known  constitution. 

Metacrylic  acid  crystallises  readily  from  water  in  shining  prisms  which  melt  at  +16° 
and  boil  at  161°,  or  at  60°  to  63°  under  12  mm.  pressure.  It  has  a  strong  but  not  un- 
pleasant odour  of  bad  mushrooms  and  occurs  in  Roman  chamomile  ;  it  dissolves  very 
readily  in  alcohol  or  ether.  It  exhibits  a  marked  tendency  to  polymerise,  more  especially 
at  130°,  but  also  hi  the  cold  when  in  contact  with  concentrated  hydrochloric  acid.  The 
calcium  salt  forms  crystals  very  soluble  in  water. 

PENTENOIC  ACIDS,  C6H8O8 

Several  isomeric  pentenoic  acids  are  known,  those  which  have  been  most  closely 
studied  being  : 

(a)  ANGELIC  ACID  (a-Ethylidenepropionic,  a/3-Dimethylacrylic  or  2-Methyl-2- 

CH3— C— C02H 
butenoic-i  Acid),  .     The  double  linking  in  this  acid  must  be  in  the 

0*n3 — C — H 

a  /3-position,  since  lactonic  derivatives  are  unknown.      On  protracted  heating  it  is  trans- 
formed into  the  stereoisomeric  t;glic  acid. 

Angelic  acid  was  first  found  in,  and  is  still  obtained  from,  the  roots  of  Angelica  arc- 
angelica,  and  as  ether  in  Roman  chamomile  oil.     The  pure  crystals  melt  at  45°,  boil  at  185°, 
and  are  only  slightly  soluble  in  water  or  volatile  hi  steam. 
CH3— C— C02H 

(b)  TIGLIC  ACID,  ,  often  occurs  with  angelic  acid  and  is  formed  in  the 

H— C— CH3 

decomposition  of  various  more  complex  organic  compounds.  It  can  be  prepared 
synthetically  from  acetaldehyde  and  ethyl  a-bromopropionate  in  presence  of  zinc,  a 
ydroxy-acid  being  formed  as  an  intermediate  compound.  It  forms  transparent  crystals, 
.mp.  65°,  b.pt.  198-5°,  and  is  slightly  soluble  in  cold  and  readily  in  hot  water  ;  it  has  a 
pleasant  smell  and  is  volatile  in  steam. 


PENTENOIC    ACIDS  297 

ftl 

PYROTEREBIC  ACID  (2-Methyl-2-pentenoic-5  Acid) ,  ~;,3>C  :  CH-CH2-COOH, 

^**3 

is  formed  by  the  distillation  of  an  oxidation  product  (terebic  acid)  of  oil  of  turpentine 
<(  together  with  the  lactone  of  isocaproic  acid,  see  below). 

(CH3)2.C.CH(C02H).CH2 

|  =      C02  +  (CH3)2  :  C :  CH .  CH2 .  COOH. 

0 CO 

Terebic  (yy-dimethylparaconic)  acid  Pyroterebic  acid 

That  pyroterebic  acid  really  has  this  constitution  is  shown  by  the  fact  that/  on 
reduction  with  hydriodic  acid,  it  gives  isocaproic  acid  of  the  known  constitution 
•(CH3)2.CH.CH2-CH2.COOH.  The  position  of  the  double  linking  is  confirmed  by  the 
great  ease  with  which  it  is  converted  into  isocaproic  lactone  on  prolonged  boiling  or  by 
the  action  of  a  small  quantity  of  hydro bromic  acid  : 


(CH3)2  :  C  :  CH-CH^CC-OH  *  (CH3)2  :  C— CH2— CH2 

—CO 


•w 

c- 


Pyroterebic  acid  is  a  colourless  liquid  solidifying  at  —15°  and  boiling  at  207°  ;  it  is 
lighter  than  water,  which  dissolves  it  with  difficulty. 

y-ALLYLBUTYRIC  ACID  (i-Heptenoic-7  Acid),  CH2  :  CH.[CH2]4.CO2H,  is 
obtained  from  cycloheptanone  (or  siiberone)  by  Wallaces  reaction,  passing  through  the 
oxime,  amine,  &c. : 

CH2  •  CH2  •  CH2v  CH2  •  CH2  •  CH  •  2COOH 

|  '  \co  -*  I 

CH2  •  C.U2  •  CHjj  OH2  •  OH  :  CH2 

Cycloheptanone  y-Allylbutyric  acid 

It  is  a  liquid  boiling  at  226°  and,  on  oxidation,  is  converted  into  adipic  acid, 
COOH-  CH2 •  CH2  •  CH2  •  CH2 -  COOH. 

TERACRYLIC  ACID  (2  :  3-Dimethyl-2-pentenoic-5  Acid),  (CH3)2 :  C  :  C(CH3) • 
CH2-COOH,  is  homologous  with  pyroterebic  acid  and  is  also  obtained  by  distilling  an 
oxidation  product  (terpenylic  acid)  of  oil  of  turpentine  : 

CH2.C02H 

(CH3)2  :  C-  CH  -  CH2         =      CO2  +  (CH3)2  :  C  :  C(CH3) .  CH2 .  C02H. 

Teracrylic  acid 
O CO 

Terpenylic  acid 

It  is  a  liquid,  b.pt.  218°,  and  is  slightly  soluble  in  water  ;  with  HBr  it  forms  hepta- 
lactone,  the  y  -position  of  the  double  linking  being  thus  confirmed. 

CITRONELLIC  ACID  (Dextro-rotatory),  CjoHisOjj.  It  has  not  yet  been  definitely 
decided  which  of  the  two  following  formulae  must  be  attributed  to  this  acid  : 

CH3, 

\C-  [CH2]3.CH(CH3).CH2.C02H  (2  :  Q-Dimethyl-l-octenoic-8  acid). 
CH./ 

S3>c  :  CH'  [CH2]2.CH(CH3).CH2.C02H  (2  :  6-Dimethyl-2-octenoic-8  acid). 
C±i3 

It  is  a  liquid  boiling  at  152°  under  18  mm.  pressure,  has  a  faint  odour  of  capric 
acid  and  is  obtained  by  the  oxidation  of  citronellal  (an  aldehyde,  C^H^O,  abundant  in 
ethereal  oils). 

One  of  the  two  formulae  must  be  attributed  to  Rhodinic  Acid  (leevo-rotatory), 
obtained  by  oxidising  rhodinol,  C|0H200. 

An  inactive  i-Rhodinic  Acid  is  also  known,  this  being  obtained  by  the  reduction 
(sodium  in  amyl  alcohol)  of  geranic  acid,  (CH3)2 :  C :  CHC-H2-CH2.C(CH3) :  CH-C02H, 
•the  hydrogen  beingadded  only  at  the  a  /3-double  linking. 


UNDECENOIC  ACID,  CH2  :  CH.[CH2]8-CO2H.  The  position  of  the  double  linking 
in  this  acid  is  confirmed  by  the  fact  that,  on  oxidation,  the  acid  yields  considerable 
quantities  of  Sebacic  Acid,  COaH^CHaJg-COaH. 

It  is  obtained  (about  10  per  cent.)  on  distilling  castor  oil  under  reduced  pressure.  It 
forms  crystals  melting  at  24-5°  and  boils  unchanged  at  213-5°  (100  mm.).  When  reduced 
with  hydrogen  iodide,  it  gives  normal  undecoic  acid,  the  non-branched  character  of  the 
carbon  atom  chain  being  thus  proved. 

HYPOG-<EIC  ACID,  CH3.[CH2]7-CH  :  CH.[CH2]5.C02H,  was  formerly  thought  to 
exist  in  Arachis  hypogcea,  but  the  acid  there  present  has  been  shown  to  be  another  acid 
(arachic  acid).  It  can  be  prepared  by  fusing  stearolic  acid  with  potash,  an  intermediate 
product  with  two  double  bonds  being  probably  formed  : 

CH3 .  [CH2]7 .  C  I  C •  [CH2]5 .  CH2 . CH2 . C02H  — > 

Stearolic  acid 
CH3 •  [CH2]7 •  CH  :  CH •  [CH2]5 . CH  :  CH. C02H  > 

Hypothetical  intermediate  acid 

CH3.C02H  +  CH3-  [CH2]7.CH  :  CH.  [CH2]5.CO2H, 

Acetic  acid  Hypogseic  acid 

OLEIC  ACID,  C18H34O2 
(CH3.[CH2]5-CH  :  CH.[CH2]7-CO2H) 

This  acid  is  very  abundant  in  nature  in  the  form  of  glyceride  (triolein), 
especially  in  vegetable  and  animal  oils  and  fats.  After  hydrolysis  of  the  fat, 
the  fatty  acids  are  liberated  and  from  these  the  oleic  acid  separates,  as  it  is 
liquid,  whilst  the  others  are  solid.  Although  Chevreul  discovered  oleic  acid 
at  the  beginning  of  the  nineteenth  century,  it  was  only  in  1846  that  its 
composition  was  definitely  established  by  Gottlieb. 

In  the  subsequent  section  dealing  with  soap  and  candles,  the  method 
of  preparing  oleic  acid  on  a  large  scale  (Italy  imported  47,300  quintals  of 
"oleine,"  of  the  value  of  £132,000,  and  exported  35,541  quintals,  of  the  value 
of  £99,500,  in  1910)  will  be  described  in  detail ;  at  the  present  juncture,  only 
the  constitution  and  the  methods  of  obtaining  pure  oleic  acid  will  be  con- 
sidered. Oils  rich  in  olein  (olive  oil,  almond  oil,  lard,  &c.)  are  hydrolysecl 
with  caustic  potash  in  the  hot,  the  fatty  acids  being  separated  from  the  trans- 
parent soap  thus  obtained  by  means  of  hydrochloric  acid  ;  these  acids  are 
then  heated  for  several  hours  with  lead  oxide  at  100°,  and  the  resulting  lead 
salts  dried  and  extracted  with  ether.  This  solvent  dissolves  only  the  lead 
oleate,  the  oleic  acid  being  freed  from  the  lead  by  means  of  hydrochloric  acid. 
The  oleic  acid  thus  obtained  is  purified  by  transforming  it  into  the  barium 
salt  and  crystallising  it  from  dilute  alcohol,  or  by  repeatedly  freezing  (at 
—  6°,  --  7°)  and  squeezing  the  solid  oleic  acid,  which,  when  pure,  melts  at 
14°  and  has  a  specific  gravity  of  0-900  in  the  liquid  state  ;  it  has  neither  smell 
nor  taste  and,  in  alcoholic  solution,  shows  no  reaction  towards  litmus.  In  the 
air  and  when  kept  for  a  long  time,  the  acid  turns  brown,  assumes  an  acid 
reaction  and  taste,  and  undergoes  partial  oxidation.  Under  a  pressure  of 
10  mm.,  it  boils  unchanged  at  223°  ;  it  can  also  be  distilled  without  alteration 
by  means  of  steam  superheated  to  250°. 

The  salts  of  oleic  acid  (and  of  other  high  fatty  acids)  form  the  soaps  ;  the 
alkali  salts  are  soluble  in  water  and  separable  from  this  by  salt  (NaCl),  in 
saturated  solutions  of  which  they  are  completely  insoluble.  The  calcium, 
barium,  lead,  &c.,  salts  or  soaps  are  insoluble  in  water. 

The  action  of  concentrated  sulphuric  acid  has  already  been  mentioned 
(see  Iso-oleic  Acid). 

An  important  and  characteristic  reaction  of  oleic  acid  is  its  almost  quantita- 
tive transformation,  by  a  little  nitrous  acid  (also  by  heating  at  200°  with 
sulphurous  acid  or  sodium  bisulphite),  into  the  stereoisomeric  Elaidic  Acdi, 


OLEIC    ACIDS 

which  separates  from  alcoholic  solution  in  white  scales  melting  at  51°  to  52° 
and  boiling  unchanged  at  225°  under  a  pressure  of  10  mm.1 

That  these  two  isomeric  acids  have  direct  (normal)  carbon -atom  chains  is  shown  with 
certainty  by  the  fact  that,  on  reduction  (e.g.  with  hydriodic  acid  and  phosphorus  2),  each 
of  them  takes  up  two  hydrogen  atoms  giving  stearic  acid,  which  is  known  to  have  an 
unbranched  carbon-atom  chain  ;  also  with  bromine,  they  give  dibromo -derivatives  of 
stearic  acid,  and,  with  permanganate,  dihydroxystearic  acid,  C^gH^C^OH)^ 

The  position  of  the  double  linking  in  the  molecule  was  under  discussion  for  a  number 
of  years  and  until  quite  recently  this  linking  was  held  to  be  at  the  end  of  the  chain  next 
the  carboxyl  group,  i.e.  in  the  a  /3 -position,  CH3-  [CH2]l4-CH  :  CH-COOH,  since  fusion 
of  these  two  acids  with  caustic  potash  resulted  in  the  formation  of  palmitic  acid  ( Varren- 
trapp's  reaction,  p.  290).  But  this  proof  no  longer  seemed  sufficient  when  it  was  shown 
that  fusion  with  potash  generally  displaced  the  double  bond.  On  the  other  hand,  Baruch 
(1894)  succeeded  in  eliminating  hydrogen  bromide  from  the  dibromide  of  oleic  acid,  thus 
obtaining  stearolic  acid,  which  has  a  triple  bond  in  the  middle  of  the  molecule.  Also  the 
products  of  oxidation  (by  permanganate)  of  oleic  acid  consist  partly  of  pelargonic  and 
azelaic  acids,  which  contain  nine  carbon  atoms,  this  reaction  hence  indicating  that  the 
oleic  acid  molecule  breaks  in  the  middle  of  the  chain,  at  the  position  of  the  double  linking. 

The  most  certain  proof  of  the  constitution  of  oleic  acid  has  been  advanced  only  recently 
as  a  result  of  the  study  of  the  ozonide  of  oleic  acid  and  of  its  decomposition  products 
(E.  Molinariand  Soncini,  1905  and  1906  ;  C.  Harries,  1906).  The  ozone  is  added  quanti- 
tatively at  the  position  of  the  double  bond  (see  p.  88),  and,  according  as  ozonised  air 
(E.  Molinari)  or  ozonised  oxygen  (Harries)  is  employed,  so  the  simple  ozonide  r 

CH3  -  [CH2]7 •  CH CH •  [CH2]7 .  COOH 

0—0—0 

or  a  peroxide  of  the  ozonide  : 

CH3 •  [CH2]7 •  CH— CH-  [CH2]7 . C-  OH 

I          I  II 

o — o  o 

w         II 

o 

is  obtained. 

Decomposition  of  these  ozonides  (of  oleic  and  elaidic  acids)  with  dilute  alkali  or  water 
in  the  hot  results  in  the  formation  of  acids  (nonoic,  azelaic,  and  others)  or  aldehydes  (nonyl 
and  semiazelaic)  with  nine  carbon  atoms,  showing  that  the  molecule  is  ruptured  at  the 
position  of  the  central  double  linking. 

ISO-OLEIC  ACID,  C18H34O2.  With  concentrated  sulphuric  acid,  elaidic  and  oleic 
acids  give  Stearinsulphuric  Acid,  C17H34(O-SO3H) -C02H,  which,  with  hot  water,  loses 
sulphuric  acid  and  gives  hydroxystearic  acid,  C17H34(OH)-C02H  (with  the  OH  at  the 
position  10).  When  distilled  under  reduced  pressure  (100  mm.)  or  with  superheated 
steam,  this  acid  loses  water  and  gives  a  considerable  quantity  of  a  white,  solid  acid — 
iso-oleic  acid — which  is  readily  soluble  in  alcohol  and  slightly  so  in  ether,  from  which  it 
crystallises  in  plates,  melting  at  44°  to  45°.  The  addition  of  the  molecule  of  water  to 
oleic  or  elaidic  acid  should  take  place  at  the  central  double  linking  (provided  the  sulphuric 
acid  does  not  previously  displace  this  linking)  and  the  subsequent  separation  of  water 
should  occur  at  two  carbon  atoms  adjacent  to  the  double  linking,  so  that  the  probable 
constitution  of  iso-oleic  acid  is,  CH3[CH2]8-CH  :  CH- [CH2]6-C02H.  But  various  facts 
are  known  which  throw  doubt  on  the  accuracy  of  this  formula. 

Aa^-OLEIC  ACID  (2-Octadecenoic-iAcid),  CH3-[CH2]14-CH  :  CH-CO2H,  is  pre- 
pared by  the  removal  of  1  mol.  of  halogen  hydracid  from  the  a -halogen  derivative  of 
stearic  acid.  It  forms  white  crystals  melting  at  58°  to  59°,  does  not  take  up  ozone  in 
cold  chloroform  solution,  and  gives  palmitic  acid  when  treated  with  permanganate. 

1  From  an  industrial  point  of  view  the  transformation  of  a  liquid  fatty  acid  into  a  solid  one  is  of  interest,  but 
this  change  is  not  utilisable  in  practice  as  it  only  proceeds  well  with  fairly  pure  and  fresh  oleic  acid  and  not  with 
the  commercial  acid,  which  may  be  old  and  possibly  polymerised  (see  also  later  section  on  Hydrolysis  of  Pats). 

2  According  to  Ger.  Pats.  141.029  and  211,669,  1907,  the  reduction  can  also  be  effected  by  hydrogen  in  presence 
of  finely  divided  nickel  (E.  Endmann,  Sabatier  and  Senderens*  reactions  [see  pp.  34,  59,  and  103  ;    also  later, 
Hydrolysis  of  Fats) 


300 


ORGANIC    CHEMISTRY 


ERUCIC  ACID  (9-Docosenoic-22  Acid),  CH3-[CH2]7.CH  :  CH-[CH2]n.CO2H,  is 
found  as  glyceride  in  the  oil  of  black  and  white  mustard,  and  in  tho.se  of  grape-seed  and 
ravison,  from  which  it  is  readily  extracted.  It  is  obtained  crystalline  from  alcohol  in 
shining  needles  melting  at  34°,  and  boils  at  254-5°  under  a  pressure  of  10  mm. 

It  forms  a  lead  salt  soluble  in  ether,  as  does  oleic  acid,  and,  like  the  latter,  it  is  readily 
transformed  into  its  stereoisomeride,  Brassidic  Acid,  by  the  action  of  a  little  nitrous 
acid  or  of  sulphurous  or  hydrobromic  acid  in  glacial  acetic  acid  solution.  This  isomeride 
crystallises  from  alcohol  in  leaflets  melting  at  65°,  and  boils  at  256°  under  a  pressure  of 
10  mm.  ;  its  lead  salt  is  slightly  soluble  in  hot  ether. 

These  two  isomerides  are  not  reduced  by  sodium  amalgam,  but  with  hydriodic  acid 
they  yield  the  saturated  behenic  acid,  C22H44O2.  When  fused  with  potash,  they  give 
arachic  (C20H40O2)  and  acetic  acids.  They  yield  various  oxidation,  bromination,  and 
esterification  products.  They  have  normal  carbon -atom  chains  and  the  position  of  the 
double  linking  is  indicated  by  the  fact  that  nonoic  acid,  CH3-  [CH2]7-COOH,  and  brassylic 
acid,  C02H- [CH2]11-CO2H  (and  also  a  little  arachic  acid),  are  among  the  products  of 
oxidation  by  nitric  acid,  while  elimination  of  HBr  from  the  dibrominated  product  gives 
the  corresponding  behenolic  acid,  which  has  a  triple  bond  and  is  of  known  constitution. 

ISOERUCIC  ACID,  CH3.[CH2]8.CH  :  CH.[CH2]10-C02H  (?),  is  obtained  by  adding 
hydrogen  iodide  to,  and  then  removing  it  from,  erucic  acid  (just  as  with  iso-oleic  acid), 
and  it  appears  that  the  double  linking  is  not  displaced  during  these  changes,  since  decom- 
position of  the  dibromide  of  this  acid  (i.e.  elimination  of  HBr)  gives  the  same  behenolic 
acid  as  is  given  by  erucic  acid,  while  oxidation  with  nitric  acid  also  gives  nonoic  and 
brassylic  acids.  Isoerucic  acid  should  hence  have  the  same  constitution  as  erucic  and 
brassidic  acids,  so  that,  contrary  to  theoretical  indications,  three  isomerides  would  seem 
to  exist  ;  this  requires  confirmation.  This  acid  melts  at  54°  to  56°. 


B.  UNSATURATED  MONOBASIC  ACIDS  OF  THE 
SERIES  CnH2n_402 

The  members  of  this  series  may  be  divided  into  two  groups,  as  is  the  case 
with  the  hydrocarbons  of  the  diolefine  and  acetylene  series  (see  p.  90)  :  acids 
having  a  triple  linking  (propiolic  series)  and  those  having  two  double  linkings 
(diolefine  series). 

(a)  ACIDS  WITH  TRIPLE  LINKING 
(Propiolic  or  Acetylenecarboxylic  Series) 


Name 

Constitutional  formula 

Melting- 
point 

Boiling- 
point 

C,H2O2      Acetylenecarboxylic  (propiolic) 

acid  ....... 

HC  !C-CO,H 

9° 

83°  (50  mm.) 

C4H4O2     Methylacetylenecarboxylic 

(tetrolic)  acid      . 

CH3-C  ;C-CO2H 

76-5° 

203° 

C6H  6O2      Ethyl-acetylenecarboxylic  acid  . 

C2H6-C  !C-CO2H 

50° 

— 

C.H802      Propyl- 

C3H7-C  IC-CO2H 

27° 

125°  (20mm.) 

C6H8O2      Isopropyl- 

C3H,-C  ;C-CO2H 

38° 

115° 

C,H,0O2    n-Butyl- 

C4H9-  i  C-CO2H 

— 

135° 

C,H,0Oa    tert.-Butyl- 

C4H9-Ci  C-C02H 

47° 

116° 

C8H12O2    n-Amyl- 

C5Hn-Ci  C-CO2H 

5°. 

149° 

C6H14O,    n-Hexyl- 

C6HI3-Ci  C-CO2H 

—  10° 

— 

C10H10O2  n-Heptyl- 

C,HIS-C;  c-co2H 

6°-10° 

166°  (20  mm.) 

Ci2H20O2  n-Nonyl- 

C,H19-C:  C-CO2H 

30° 

—  . 

CnHuOs   Dehydroundecenoic  acid  . 

CH  i  C-[CH2]8-CO2H 

42-8° 

175°  (15  mm.) 

CnH18O2   Undccolic  acid 

CH3-Ci  C[CHoJ,.CO2H 

59-5° 

— 

C19H32O2  Stearolic  acid 

CH3-  [CH,],-C  :  C-  [CH,]7.C02H 

48° 

— 

C1SH32O2  Tariric  acid     .... 

CH3-  [CH2110-C  •  C-[CK»]4-CO2H 

50-5° 

— 

C22H40O2  Behenolic  acid 

CH3-[CH2j,-Ci  C-[CHoiu-CO2H 

57-5° 

PREPARATION.     These  acids  can  be  obtained  by  the  following  reactions  : 
From  a  sodium  alkyl  acetylide  (suspended  in  ether),  by  the  action  of  C02 
(a)  or  of  ethyl  chlorocarbonate  (b)  : 


PROPIOLICACIDS  301 

(a)  ,  CH3-C  1  C-Na  +  C02  =  CH3-C  •  C-C02Na. 

Sodium  methylpropiolate 

(6)  C3H7-C  !  C-Na  +  C1-CO-OC2H5  =  NaCI  +  C3H7-C  •  C-CO-OC2H5. 

Ethyl  propylacetylenecarboxylate 

Various  other  acids  of  this  series  having  the  triple  linking  at  a  distance 
from  the  carboxyl  group  (and  hence  much  more  stable  than  the  preceding, 
which,  when  heated,  lose  C02  and  give  acetylene  hydrocarbons)  are  obtained 
by  the  elimination  of  2HBr  (by  the  action  of  alkali)  from  acids  of  the  oleic 
series,  this  reaction  being  similar  to  that  taking  place  with  unsaturated  hydro- 
carbons (see  p.  91) : 

CH3-  [CH2]7-CHBr-CHBr-  [CH2]7-C02H  = 

Dibromide  of  oleic  acid 

2HBr  +  CH3-  [CH2]7-C  :  C-  [CH2]7-C02H. 

Stearolic  acid 

PROPERTIES.  Acids  of  the  type  R-C:  C-C02H,  when  treated  with 
sodium  in  absolute  alcoholic  solution,  take  up  4  atoms  of  hydrogen,  giving 
acids  of  the  saturated  series  ;  they  also  combine  easily  with  2  atoms  of  bromine, 
but  the  second  pair  of  bromine  atoms,  required  to  produce  saturation,  are 
added  only  with  difficulty  (the  action  of  light  facilitates  the  reaction)  ;  when 
boiled  with  alcoholic  potash,  they  take  up  a  molecule  of  water,  forming 
saturated  j3-ketonic  acids  : 

R-C  i  C-C02H  +  H20  =  R-CO-CH2-C02H; 

with  aqueous  potash,  however,  they  yield  methyl  ketones,  separation  of 
C02  also  taking  place  ;  tert.-butyltetrolic  acid  does  not  react.  The  amines 
and  hydrazine  also  give  characteristic  reactions  with  these  acids.  The  esters 
of  the  acids  have  pleasant  odours  and  are  used  in  perfumes. 

Acids  with  a  triple  bond  do  not  unite  with  the  ozone  of  a  current  of 
ozonised  air  (E.  Molinari,  1907  and  1908),  but  yield  peroxyozonides  with 
ozonised  oxygen  (Harries,  1907  ;  see  p.  299). 

PROPIOLIC  ACID  (Propinoic,  Propargylic,  or  Acetylenecarboxylic  Acid), 
CH  •  C'CO2H,  is  obtained  by  heating  the  aqueous  solution  of  potassium  acetylene  - 
dicarboxylate  : 

C— C02H  C— H 

III  =      C02  +    III 

C— COjK  OCO2K 

Propiolic  acid  is  a  liquid  with  a  more  intense  odour  than  acetic  acid  ;  it  has  the 
sp.  gr.  1-139,  is  soluble  in  water,  alcohol,  or  ether,  solidifies  at  4°,  melts  at  9°,  and  distils 
unchanged  at  a  pressure  of  50  mm. 

The  alkali  and  alkaline -earth  salts  are  extremely  soluble  in  water. 

Prom  its  esters,  metallic  acetylides  (p.  91 )  are  readily  prepared.  Under  the  action  of 
light  and  in  a  vacuum,  it  undergoes  partial  polymerisation,  yielding  benzenetricarboxylic 
acid. 

TETROLIC  ACID  (2-Butinoic  or  Methylpropiolic  Acid),  CH3-C  i  C  CO2H,  is 
obtained  by  eliminating  HC1  from  the  /3-chloro -derivative  of  crotonic  or  isocrotonic 
acid.  It  crystallises  from  water  in  rhombic  plates,  melting  at  76-5°  and  boils  unchanged 
at  203°,  but  it  distils  only  with  difficulty  in  a  current  of  steam. 

Under  the  action  of  sod'um  in  alcoholic  solution  (but  not  with  sodium  amalgam  in 
aqueous  solution),  it  takes  up  hydrogen  with  formation  of  butyric  acid.  When  oxidised 
with  permanganate  in  alkaline  solution,  it  yields  acetic  and  oxalic  acids. 

DEHYDROUNDECENOIC  ACID  (i-Undecinoic-n  Acid),  HC  •  C-[CH2]8.C02H, 
obtained  by  heating  dibromoundecenoic  acid  with  alcoholic  potash,  melts  at  42-8°.  On 
oxidation,  it  forms  sebacic  acid,  C02H- [CH2]8-CO2H.  It  readily  forms  acetylides. 


302  ORGANIC    CHEMISTRY 

Treatment  with  alcoholic  potash  at  180°  converts  it  into  the  isomeric  Undecolic 
Acid  (2-undecinoic-ll  acid),  CH3-C  :  C- [CH2]7-CO2H,  melting  at  59-5°;  the  latter 
"is  hence  formed  with  the  dehydroundecenoic  acid,  if  the  reaction  referred  to  above 
takes  place  at  a  high  temperature.  Oxidation  of  undecolic  acid  yields  azelaic  acid, 
C02H-  [CH2]7'CO2H  ;  it  does  not  give  acetylides,  owing  to  the  absence  of  the  charac- 
teristic acetylenic  hydrogen  atom  (see  p.  90). 

STEAROLIC  ACID  (g-Octadecinoic-i  Acid),  CH3.[CH2]7-C  I  C-[CH2]7-CO2H,  is 
readily  obtained  by  boiling  dibromostearic  acid  (prepared  by  brominating  oleic  or  elaidic 
acid)  with  alcoholic  potash.  It  melts  at  48°,  and  under  the  influence  of  sulphuric  acid 
takes  up  water,  giving  a  ketostearic  acid.  When  oxidised  with  permanganate,  it  takes 
up  2  atoms  of  oxygen,  giving  diketostearic  acid,  whilst  with  nitric  acid  it  is  resolved 
into  nonoic  and  azelaic  acids  (it  is,  however,  stable  in  the  air,  and  thus  differs  from 
oleic  and  linolic  acids) : 

C— [CH2]7  •  CH3  CO  •  [CH0]7  •  CH3 

HI  __^      CH3.[CH2]7.C02H  +  CO2H.[CH2]7.(X)2H. 

C—  [CH2]7-C02H  CO-[CH2]7-CO2H  Nonoic  acid  Azelaic  acid 

Stearolic  acid  Diketcstearic  acid 

Stearolic  acid  unites  with  2HI,  and  the  resulting  diiodostearic  acid,  when  heated  with 
alcoholic  potash,  gives  stearolic  acid  again,  but  in  two  isomeric  forms,  having  the  triple 
linking  in  the  8  to  9  and  10  to  11  positions  respectively. 

The  constitution  of  stearolic  acid  was  confirmed  by  Harries  (1907)  by  decomposing 
the  peroxyozonide  of  the  acid,  obtained  by  the  action  of  ozonised  oxygen  (ozonised  air 
does  not  yield  an  ozonide,  see  p.  299) : 

0-C-[CH2]7.CH3 

0£|      ||  /OH       +2H20  = 

X0-C.[CH2]7.C/ 

>0=  O 

Peroxyozonide  of  stearolic  acid 

H202  +  CH3.[CH2]7.C02H  +  C02H-[CH2]7.C02H. 
Nonoic  acid  Azelaic  acid 

TARIRIC  ACID  (6-Octadecinoic-i  Acid),  CH3.[CH2]10-C  :  C-[CH2]4-CO2H,  is 
isomeric  with  stearolic  acid  and  melts  at  50-5°  ;  as  glyceride,  it  forms  the  principal 
component  of  the  fat  of  the  fruit  of  Picramnia  Camboita.  It  is  the  first  compound  with  a 
triple  bond  resulting  from  the  vital  process  of  an  organism.  It  is  stable  in  the  air  and 
yields  stearic  acid  on  reduction  with  hydriodic  acid,  so  that  its  molecule  contains  a 
normal  carbon  atom  chain.  Energetic  oxidation  with  permanganate  or  nitric  acid  yields 
lauric  acid,  CH3-  [CH2]10-CO2H,  and  adipic  acid,  C02H-  [CH2]4-C02H. 

BEHENOLIC  ACID  (9-Docosinoic-22  Acid),  CH3.tCH2j7-CiC-tCH2Jn.C02H, 
melting  at  57-5°,  is  obtained  from  the  dibromide  of  erucic  or  brassidic  acid,  in  the 
same  way  as  stearolic  acid  is  formed  from  oleic  acid.  Its  constitution  follows  from  its 
behaviour  towards  reducing  and  oxidising  agents  and  from  the  transformation  of  its 
oxime  (Beckmann). 

(6)  ACIDS  WITH  TWO  DOUBLE  BONDS,  CnH2W_4O2 
(Diolefine  or  Sorbine  Series) 

These  acids  are  prepared  synthetically  by  methods  analogous  to  those 
used  for  obtaining  a/3-unsaturated  acids,  for  example,  by  treating  a/3-un«atu- 
rate'd  aldehydes  with  malonic  acid  in  presence  of  pyiidine  : 

CH2  :  CH-CHO  +  C02H-CH2-C02H  = 

Acrolein 

C02  +  H20  +  CH2  :  CH-CH  :  CH-CO2H. 

/S-Vinylacrylic  acid 

The  acids  of  4he  sorbine  seiics,  in  which  the  two  double  linkings  are 


DIOLEFINICACIDS  303 

conjugated — that  is,  one  in  the  a/3-  and  the  other  in  the  y  ^-position  and  there- 
fore separated  by  a  simple  linking — can  be  reduced  by  sodium  amalgam  in 
aqueous  solution  (in  presence  of  a  stream  of  C02  to  fix  the  alkali)  ;  only  two 
hydrogen  atoms  are  then  added,  one  for  each  double  linking,  and  a  new  double 
linking  remains  in  the  place  of  the  simple  linking  previously  separating  the 
two  original  double  bonds  : 

X-CH:CH-CH:CH-C02H  +  H2  =  X-CH2-CH  :  CH-CH2-C02H. 

When  these  sorbinic  acids  are  oxidised  with  permanganate,  two  hydroxyl 
groups  enter  at  the  a  /3-double  linking,  while  the  chain  is  broken  at  the  y  £- 
double  linking  with  formation  of  an  aldehyde  (which  then  undergoes  oxida- 
tion) and  racemic  acid  : 

X .  CH  :  CH  •  CH  :  CH  •  C02H  — >  X  •  CHO  +  C02H  •  CH(OH)  •  CH(OH)  •  CO2H, 

Racemic  acid 

When  they  are  heated  with  aqueous  ammonia,  2  mols.  of  the  latter  are  added 
at  the  double  linking  and  two  diamino-acids  formed. 

On  heating,  acids  of  the  sorbine  series  readily  polymerise  ;  hence,  when 
they  are  heated  with  lime  or  baryta,  not  only  is  C02  removed  and  diolefine 
hydrocarbons  obtained,  but  di-  and  tri-molecular  condensation  occurs,  giving 
more  complex  hydrocarbons  which  are  probably  of  cyclic  structure. 

/3-VINYLACRYLIC  ACID  (i  :  s-Pentadienoic,  Acid),CH2  :  CH-CH  :  CH-CO2H,  is 

synthesised  by  the  method  given  above.  It  forms  prisms  showing  a  grey  reflex,  and 
dissolves  slightly  in  cold  water,  but  readily  in  hot.  At  80°  it  melts  to  a  mobile  liquid, 
which,  at  100°  to  115°,  becomes  dense  and  syrupy  and  then  suddenly  decomposes  with 
evolution  of  gas.  In  carbon  disulphide  solution  it  unites  with  four  atoms  of  bromine. 

SORBINIC  or  SORBIC  ACID  (2:  4-Hexadienoic  Acid),  CH3-CH  :  CH-CH  :  CH- 
CO2H,  occurs  in  considerable  quantities  in  mountain-ash  berries.  It  melts  at  134-5°,  boils 
at  228°  with  partial  decomposition,  is  odourless  and  dissolves  readily  in  alcohol  or  ether. 

DIALLYLACETIC  ACID  (i  :  6-Heptadiene-4-methyloic  Acid),  CH2:CH-CH2- 
CH(CO2H)  -CHo-CH  :  CH2,  is  obtained  synthetically  from  acetoacetic  acid  by  two  separate 
introductions  of  the  allyl  residue.  It  is  a  liquid,  sp.  gr.  0-950,  b.pt.  219°  to  222°,  and  has 
an  unpleasant  smell.  Oxidation  with  nitric  acid  leads  to  the  rupture  of  the  carbon  atom 
chain  at  the  two  double  linking-;  and  formation  of  tricarballylic  acid  : 

CO2H-CH2^~-H-  pp.  TT 
C02H-CH2> 

GERANIC  ACID  (2  :  6-Dimethyl-2  :  6-octadienoic-8  Acid),  (CH3)2  :  C  :  CH-CH2. 
CH2-C(CH3)  :CH-CO2H,  is  obtained  either  by  oxidation  of  the  corresponding  aldehyde 
(citral)  with  silver  oxide,  or  by  elimination  of  water  from  citraloxime  by  the  action  of  acetic 
anhydride  and  hydrolysis  of  the  resulting  nitrile  with  alcoholic  potash.  It  has  also  been 
obtained,  by  a  series  of  reactions,  from  methylheptenone,  (CH3)2  :  C  :  CH-  CH2  •  CH2  •  CO  •  CH3. 

It  is  a  colourless  liquid  of  not  very  pleasing  odour  and  boils  a't  153°  under  a  pressure 
of  13  mm.  When  shaken  with  70  per  cent,  sulphuric  acid  it  yields,  among  other  products, 
the  iso merle  a-cycloyeranic  acid,  melting  at  106°  : 

CH,CH,  CH,CHo 


/C  /C\ 

HC          CH-CO2H  -  >  H2C          CH-CO2H 

I            II  II 

H2C          C-CH3  H2C          C-CH3 


H2  H 

Geranic  acid  a-Cyclogeranic  acid 

LINOLIC    ACID,  Ci8H32O2.     In  the  form  of   glyceride,   this  acid  is  an  important 
eon.tituent  of  drying  oils  (linseed,  sunflower  -seed,  &c,).     From  these  oils  a  mixture  of 


304  ORGANIC    CHEMISTRY 

unsaturated  fatty  acids  can  be  obtained  which  gives  the  nitrous  acid  reaction  (solidifica- 
tion, owing  to  the  formation  of  elaidic  from  oleic  acid)  only  to  a  slight  degree  ;  it  contains 
less  hydrogen  but  not  less  carbon  than  oleic  acid  and  is  readily  oxidised  and  thickened 
by  the  oxygen  of  the  air.  The  salts  of  these  drying  acids  are  still  more  readily  oxidisable 
than  the  acids  themselves,  and  their  lead  salts,  like  that  of  oleic  acid,  are  soluble  in  ether. 
The  various  components  of  this  mixture  of  fatty  acids  —  with  two  or  three  double  linkings 
—  have  not  been  completely  separated,  but  as  they  fix  2  mols.  of  ozone  (Molinari  and 
Soncini,  1905),  give  a  tetrabromostearic  acid,  C18H32O2Br4,  with  bromine,  and  with  alkaline 
permanganate  yield  a  tetrahydroxystearic  (sativic)  acid,  C^H^C^OH)^  which  gives  stearic 
acid  with  hydrogen  iodide,  the  mixture  must  contain  an  acid  with  two  double  bonds. 
This  is  linolic  acid,  C^H^O^  which  has  not  been  obtained  pure,  although  its  stereo- 
isomerides—  a-Elaeostearic  Acid,  melting  at  43°  to  44°,  and^Telfairic  Acid,  obtained 
from  telfairia  oil,  m.pt.  6°  and  b.pt.  220°  to  225°  under  13  mm.  pressure  —  have  been 
prepared  crystalline.  Distillation  of  ricinelaidic  acid  gives  a  further  isomeride,  which 
has  a  normal  structure,  contains  two  double  linkings,  and  melts  at  53°  to  54°. 

(c)  ACIDS  WITH  THREE  DOUBLE  BONDS,  CWH2M^6O2 

CITRYLIDENE  ACETIC  ACID  (2:6-  Dimethyl  -2:6:8-  decatrienoic  -  10  Acid), 
CH3-C(CH3)  :CH-CH2-CH2.C(CH3)  :CH-CH  :CH-CO2H,  is  a  mobile  oil,  distilling  at 
175°  under  a  pressure  of  18  mm.,  and  is  formed  by  condensing  1  mol.  of  citral  with  1  mol. 
of  malonic  acid  in  presence  of  pyridine  : 


CH3.C(CH3)  :  CH.CH2.CH2.C(CH3)  :  CH-CHO  +  C02H  •  CH2  •  CO2H  = 

Citral  Malonic  acid 

H20  +  C02  +  CuHuA.. 

Citrylideneacetic  acid 

LINOLENIC  AND  ISOLINOLENIC  ACIDS,  C18H30O2,  are  components  of  the 
mixture  of  drying  acids,  but  have  not  yet  been  isolated  in  a  pure  state.  But  with  bromine 
two  hexabromostearic  acids,  C18H3002Br6,  and  with  permanganate  two  hexahydroxy- 
stearic  acids,  C18H3002(OH)6,  have  been  obtained  and  these  must  be  derived  from  two 
acids  containing  three  double  bonds.  The  fatty  acids  of  linseed  oil  contain  50  per  cent. 
of  these  two  acids,  together  with  linolic  and  oleic  acids,  whilst  the  other  drying  oils 
contain  linolic  acid  in  preponderating  amount. 

The  constitution  of  Linolenic  Acid  was  definitely  established  by  E.  Erdmann, 
Bedford,  and  Raspe  (1909)  by  decomposing  the  corresponding  tri-ozonides.  The  three 
double  bonds  occur  in  a  normal  chain  : 

CH3  •  CH2  -  CH  :  CH  •  CH2  •  CH  :  CH  .  CH2  -  CH  :  CH  .  [CH2]7  .  CO2H. 

The  ozonides  of  two  stereoisomerides  were  prepared,  their  products  of  decomposition 
being  :  propaldehyde,  malonic  dialdehyde,  and  azelaic  semialdehyde. 

Fish  oil  contains  another  isomeride,  Jecorinic  Acid,  C18H30O2,  which  has  been 
little  studied. 

III.  POLYBASIC  FATTY  ACIDS 
A.  SATURATED  DIBASIC  ACIDS,  C«H8n(COaH)8 

These  acids  are  dibasic,  since  they  contain  two  carboxyl  groups  and  form 
two  series  of  derivatives  :  acid  and  normal. 

In  general  they  are  crystalline  substances,  which  distil  unchanged  in  a 
vacuum  (beyond  C3)  and  are  soluble  in  water.  The  members  with  even 
numbers  of  carbon  atoms  have  lower  melting-points  than  their  immediate 
neighbours  in  the  series  with  odd  numbers  of  carbon  atoms,  and  the  differences 
thus  shown  diminish  as  the  number  of  carboii  atoms  increases.  The  solu- 
bility in  water  is  greater  with  the  acids  containing  an  odd  number  of  carbon 
atoms  than  for  the  others,  and  in  both  cases  it  diminishes  with  increase  of 
molecular  weight.  The  dissociation  constant  is  very  high  for  oxalic  acid, 
and  diminishes  considerably  in  the  higher  homologues,  which  are  hence  less 
energetic  acids. 


SATURATED    DIBASIC    ACIDS 

TABLE  OF  THE  NORMAL  SATURATED  DIBASIC  ACIDS 


305 


Empirical 
formula 

Name 

Structural  formula 

Melting- 
point 

C2H204 

Oxalic  acid       -.        ... 

COOH-COOH 

189°  (anhyd.) 

C3H404 

Malonic   ,,           .          »        -  .  .  ' 

C02H.CH2.C02H 

132° 

C4H604 

Succinic  „       •    «.         .'•'•• 

CO2H.[CH2]2.CO2H 

182° 

C5H804 

Glutaric  ,,           »         .          . 

C02H.[CH2]3.CO2H 

97-5° 

C6H10O4 

Adipic     ,,           .    •      .          ... 

C02H.[CH2]4.C02H 

149° 

C7H12O4 

Pimelic    ,,         '  .      '    , 

CO2H.[CH2]5.C02H 

103° 

CgH14O4 

Suberic    ,,           .          . 

CO2H.[CH2]6.OC2H 

141° 

C9H1604 

Azelaic     ,,            .          . 

CO2H.[CH2]7.CO2H 

106° 

QoHi8O4 

Sebacic    „           .         .          »s        . 

CO2H.[CH2]8.CO2H 

133° 

C12H22O4 

Decamethylenedicarboxylic    acid  . 

C02H.[CH2]10.C02H 

125° 

Ci3H2404 

Brassylic  acid     ,         i          . 

C02H.[CH2JU.C02H 

112° 

^14H26O4 

Dodecamethylencdicarboxylic  acid 

C02H-[CH2]12.C02H 

123° 

Ci7H3204 

Roccellic  acid     .          .    ..';.• 

CO2H.[CH2]15.CO2H 

132° 

METHODS  OF  PREPARATION.  In  addition  to  the  usual  methods  of 
oxidising  monobasic  fatty  acids,  primary  hydroxy -acids,  alcohols,  and  glycols, 
an  important  and  general  method  consists  in  hydrolysing  the  nitriles  (see 
p.  199)  or  cyano-derivatives  of  the  acids,  these  being  obtained  from  halogen 
alkyls  with  a  less  number  of  carbon  atoms. 

Dibasic  acids — always  of  higher  molecular  weight — are  also  obtained  by 
the  condensation  of  2  mols.  of  the  esterified  monopotassium  salt  of  a  lower 
dibasic  acid  by  electrolysis  in  Hofer's  apparatus  : 


GH,-COOCJB, 


CH2-COOK        .H-OH 


CH2-COOK 
CH2-COOC2H5 

2  mols.  Potassium  ethyl  succinate 


COOC2H5 


-  2C0    +  2KOH  +  H 


i 


H2 

Ethyl  adipate 


PROPERTIES.  The  constitution  is  deduced  from  the  synthesis  in  which 
compounds,  especially  the  nitriles,  of  known  constitution  are  employed. 
Structural  isomerism  commences  with  the  acids  containing  four  carbon  atoms. 
Those  acids  which  have  the  two  carboxyls  united  to  different  carbon  atoms 
(i.e.  other  than  oxalic  and  malonic  acids  and  their  derivatives),  in  presence 
of  dehydrating  substances  (PC15,  COC12,  &c.),  or  on  heating,  lose  a  molecule  of 
water  and  form  a  kind  of  cyclic  compound,  known  as  an  internal  anhydride : 


CH2-COOH 


CH-CO 


!H2-COOH 

Succinic  acid 


CHyCOOH 


CHC 


=  H20 


=  H20 


H,-COOH 


Glutaric  acid 


Succinic  anhydride 

CH2— CO 


H2    O 


CH2—  CO 

Glutaric  anhydride 


The  ready  formation  of  these  anhydrides  by  the  reaction  of  the  two 
terminal  carboxyl  groups  (w,  w')  is  readily  explained  by  arranging  the  carbon 


20 


306 


ORGANIC    CHEMISTRY 


atoms  in  space  (see  p.  18  et  seq.),  with  their  valencies  in  the  directions  of 
the  angles  of  regular  tetrahedra.  Thus,  with  succinic  acid,  which  contains 
four  carbon  atoms,  the  two  hydro  xy  Is  of  the  carboxyl  groups  are  found  to  be 
moderately  close  together  (Fig.  246),  whilst  in  glutaric  acid  the  two  hydroxyls 
are  almost  superposed,  so  that  water  readily  separates,  forming  a  closed  ring 
(Fig.  247). 

Similarly  the  amides  (which  see)  or  the  ammonium  salts  of  these  acids 
readily  form  imides  (see  later),  which  can  be  hydrolysed  like  the  amides : 

CH2-COONH4 


CH2-COOH 

Monoammonium  succinate 


=     2H20 


CH2-CCK 


Succinimido 


COOH 
OXALIC  ACID  (Ethandioic  Acid),    I  has-  been    known    from    the 

COOH 
earliest  times,  since  it  occurs  frequently  in  nature  in  plants,  especially  in 


FIG.  246. 


FIG.  247. 


sorrel,  in  the  form  of  acid  potassium  oxalate,  and  also  as  incrustations  of 
calcium  oxalate  in  plant-cells  and  in  the  roots  of  rhubarb. 

It  is  often  formed  in  the  oxidation  of  organic  substances  (sugar,  wood, 
starch,  &c.)  by  nitric  acid  or  permanganate,  or  by  fused  caustic  potash. 

It  is  obtained  synthetically  by  heating  sodium  or  potassium  formate 
rapidly  (best  in  a  vacuum  at  280°):  2H-COONa  =  Na2C204  +  H2  (the 
reverse  change,  from  oxalic  to  formic  acid,  has  already  been  referred  to  on 
p.  269),  or  by  passing  carbon  dioxide  over  metallic  sodium  heated  to  about 
350°  :  2Na  +  2C02  =  Na2C204. 

Its  industrial  manufacture  was,  until  recently,  carried  out  exclusively 
by  the  method  devised  by  Gay-Lussac  in  1829  and  applied  by  Dale  in  1856  : 
sawdust  (1  part)  moistened  with  caustic  soda  solution  (2  parts,  sp.  gr.  1-4) 
is  heated  at  about  240°  and  frequently  stirred  with  iron  plates  until  a  greenish 
yellow  mass  is  formed.  While  still  hot,  this  is  dissolved  in  water  and  the 
solution  filtered  and  concentrated  to  38°  Be.  When  cold,  the  solution 
deposits  crude  sodium  oxalate,  which  is  dissolved  in  a  small  quantity  of  boiling 
water  and  precipitated  as  insoluble  calcium  oxalate  by  means  of  lime.  The 
precipitate  is  made  into  a  paste  with  water  and  the  oxalic  acid  liberated  by 
addition  of  sulphuric  acid.  The  liquid  is  decanted  and  concentrated  until 


307 

the  whole  of  the  calcium  sulphate  separates,  the  oxalic  acid  being  then  allowed 
to  crystallise  out  and  subsequently  purified  by  repeated  recrystallisation. 

At  the  present  time,  the  acid  and  also  the  various  alkaline  oxalates  are 
prepared  by  Goldschmidt's  process  (see  p.  269),  which  consists  in  heating 
a  mixture  of  potassium  formate  or  carbonate  with  a  little  potassium  oxalate 
and  a  slight  excess  of  alkali  (3  to  4  per  cent.).  From  the  oxalate  thus  obtained 
the  oxalic  acid  is  liberated  by  means  of  sulphuric  acid. 

It  crystallises  in  odourless  and  transparent  monoclinic  prisms,  H2C204  + 
2H20,  which  have  a  marked  acid  taste,  effloresce  in  the  air,  and  dissolve  in 
13  parts  of  cold  or  0-3  to  0-4  part  of  hot  water.  The  crystals  lose  their 
water  of  crystallisation  partially  at  30°  and,  after  dehydration,  sublime. 
When  heated  moderately  strongly  or  treated  with  concentrated  sulphuric 
acid,  oxalic  acid  decomposes  into  CO,  C02,  and  H2O.  It  is  poisonous  and  is 
used  in  the  dyeing  and  printing  of  textiles  and  of  wool ;  it  serves  for  bleaching 
straw,  removing  rust  stains  from  textiles,  purifying  glycerine  and  stearine, 
cleaning  brass,  &c. 

The  acid  is  estimated  by  means  of  normal  caustic  soda  solution  in  presence  of  phenol  - 
phthalein,  or  of  decinormal  potassium  permanganate  solution  in  presence  of  sulphui.c 
acid  in  the  hot : 

2KMnO4  +  5H2C2O4  +  3H2S04  =  K2S04  +  10C02  +  8H20  +  2MnS04. 

Ammoniacal  impurities  are  detected  with  Nessler's  reagent  (vol.  i,  p.  539),  and,  when 
pure,  the  acid  should  leave  no  ash,  and  0-5  grm.  of  it  should  dissolve  completely  when 
shaken  with  100  c.c.  of  ether. 

The  commercial  crystallised  acid  is  sold  at  56*.  to  60s.  per  quintal,  whilst  the  doubly 
purified  product  costs  £4  and  the  chemically  pure  128*.  Italy  imported  the  following 
quantities  at  72*.  per  quintal :  1160  quintals  in  1907,  960  in  1908,  755  in  1909,  and  1890, 
costing  £6424,  in  1910.  In  Russia,  four  factories  produced  about  8500  quintals  of  oxalic 
acid  in  1909,  by  heating  sawdust  with  alkali.  In  1908  Germany  exported  51,000  quintals 
of  oxalic  acid  and  potassium  oxalate,  and  44,700  quintals  in  1909.  In  1911  the  United 
States  imported  1600  tons  of  oxalic  acid  of  the  value  £33,000. 

SALTS  OF  OXALIC  ACID.  Owing  to  the  presence  of  two  carboxyl  groups  in  the 
molecule,  oxalic  acid  gives  both  acid  and  neutral  salts.  The  alkaline  oxalates  are  soluble 
in  water  and  are  often  used  instead  of  the  acid,  especially  in  dyeing. 

NORMAL  POTASSIUM  OXALATE,  K2C2O4,  used  to  be  obtained  by  neutralising 
the  acid  with  potassium  carbonate,  concentrating  and  allowing  to  crystallise.  Nowadays 
it  is  prepared  by  Goldschmidt's  method  (see  above).  It  dissolves  in  three  parts  of  water, 
crystallises  with  1H2O  and  readily  effloresces  in  the  air.  It  costs  84s.  to  88*.  per  quintal, 
or,  when  chemically  pure,  £6. 

ACID  POTASSIUM  OXALATE  (or  Potassium  Hydrogen  Oxalate),  KHC2O4,  is 
obtained  by  dissolving  the  neutral  oxalate  (1  mol.)  and  oxalic  acid  (1  mol.)  in  water, 
concentrating  and  allowing  to  crystallise,  when  it  separates  with  1H20.  It  has  a  bitter, 
acid  taste,  is  poisonous  and  dissolves  in  14  parts  of  hot  water. 

POTASSIUM  TETROXALATE  (Commercial  Salt  of  Sorrel),  KHC2O4  +  H2C2O4  + 
2H2O,  does  not  effloresce  or  lose  its  water  of  crystallisation  in  the  air.  It  is  obtained  by 
mixing  a  hot,  saturated  solution  of  potassuim  oxalate  with  the  calculated  amount  of 
saturated  oxalic  acid  solution.  It  costs  84*.  to  88*.  per  quintal,  or,  if  chemically  pure,  128*. 

CALCIUM  OXALATE,  CaC2O4,  crystallises  with  2H2O  and  is  obtained  from  a 
solution  of  a  soluble  oxalate,  containing  either  ammonia  or  acetic  acid,  by  addition  of 
a  soluble  calcium  salt.  It  is  insoluble  in  water  or  acetic  acid. 

FERROUS  OXALATE,  FeC2O4,  or,  better,  Ferrous  Potassium  Oxalate, 
K2Fe(C2O4)2  +  H2O,  gives  a  yellow  aqueous  solution  owing  to  the  colour  of  its  cation. 
FeC2O4".  It  possesses  strong  reducing  properties  and  is  largely  used  on  this  account, 
while  it  serves  also  as  a  good  photographic  developer. 

POTASSIUM  FERRIC  OXALATE,  K2Fe3(C2O4)3,  gives  a  green  aqueous  solution 
owing  to  the  colour  of  its  cation,  Fe(C2O4)3'".  In  the  light  it  yields  C02  and  potas'ium 
ferrous  oxalate,  and  it  is  used  in  the  platinotype  method  of  photography. 


808 


ORGANIC    CHEMISTRY 


CO  H 
MALONIC  ACID  (Propandioic  Acid),  H4C3O4  or  CH2<£Q2"  forms  crystals  melting 

at  132°  and  is  readily  soluble  in  water  (1:1-4  at  15°),  alcohol,  or  ether.  It  occurs  in  the 
beetroot  and  is  obtained  synthetically  by  hydroly.sing  cyanoacetic  acid  prepared  from 
a  hot  aqueous  solution  of  potassium  chloroacetate  and  potassium  cyanide  : 

/~n  ^NXT  /^/~v  TT 

CH2<C02H 

Chloroacetic  acid 


Cyanoacetic  acid 


Malonic  acid 


Like  all  compounds  containing  two  carboxyl  groups  united  to  the  same  carbon  atom, 
it  evolves  C02  when  heated  above  its  melting-point,  acetic  acid  being  formed.  Higher 
monobasic  acids  are  similarly  obtained  from  alkylated  malonic  acids  : 

C"H3  •  CH2  •  CH2  •  CH<^ ^  _  _j  =  CO2  +  CH3-0112<C'l"l2-(-'H2-CO2jl. 
Normal  propylmalonic  acid  Normal  valeric  acid 

Malonic  acid  forms  an  ester,  ETHYL. MALON ATE,  CH2<^2'£225>  which  is  of  great 


importance,  since  it  allows  of  the  synthetical  preparation  of  the  most  varied  higher  dibasic 
acids,  and  from  these,  by  loss  of  carbon  dioxide,  of  the  corresponding  monobasic  acids. 
This  ester  is  obtained  by  passing  gaseous  hydrogen  chloride  into  cyanoacetic  acid  dissolved 
in  absolute  alcohol ;  it  is  then  separated  by  distillation,  as  it  boils  at  198°.  At  15°  it 
has  the  sp.  gr.  1-061. 

The  hydrogen  atoms  of  the  methylene  group  of  this  ester  can  be  replaced  by  one  or 
two  atoms  of  sodium  (or  halogens)  giving  highly  reactive  sodiomalonic  esters.  The  sodium 
in  these  can  be  substituted  by  one  or  two  alkyl  groups  simply  by  treatment  with  an  alkyl 

HOMOLOGUES  OF  MALONIC  ACID 


Name  of  acid 

Formula 

Melting- 
point 
of  acid 

Boiling-point 
of  the 
diethyl  ester 

Methylmalonic            .  . 

CH3.CH(C02H)2 

about  130° 

190°-193° 

Dimethylmalonic 

(CH3)2  :  C(C02H)2 

192°-193° 

196° 

Ethylmalonic    .         .. 

C2H5.CH(CO2H)2 

112° 

210° 

Diethylmalon  ic 

(C2H5)2  :  C(C02H)2 

124° 

230° 

Propylmalonic 

C2H5-CH2.CH(CO2H)2 

93-5° 

219°-222° 

Dipropylmalonic 

(C2H5.CH2.)2:C(C02H)2 

156° 

248°-250° 

Isopropylmalonic 

(CH3)2:CH-CH(C02H)2 

86° 

213°-214° 

Methyiethylmalonic  . 

(CH3)(C2H5)C(C02H)2 

118° 

207°-208° 

Butylmalonic    . 

C2H5-CH2.CH2.CH(C02H)2 

98-5° 

— 

sec.  Butylmalonic 

C2H5  •  CH(CH3)  •  CH(CO2H)2 

76° 

224°-225° 

Isobutylmalonic 

(CH3)2:  CH-CH2.CH(C02H)2 

107° 

225°-226° 

Diisobutylmalonic     . 

[(CH3)2  :  CH-CH2.  ]2C(C02H)2 

145°-150° 

245°-255° 

Methylpropylmalonic 

(CH3)(C2H5.CH2.)C(C02H)2 

106°-107° 

220°-223° 

Methylisopropylmalonic 

[(CH3)2CH](CH3)  :  C(C02H)2 

124° 

221° 

Pentylmalonic  . 

C2H5  •  CH2  •  CH2  •  CH2  •  CH(C02H)2 

82° 

— 

Isoamylmalonic 

(CH3)2CH.CH2.CH2.CH(C02H)2 

98° 

240°-242° 

Diisoamylmalonic 

[(CH3)2CH  -  CH2  •  CH2  •  ]2C(CO2H)2 

147°-148° 

278°-280° 

2-Methylbutylmalonic 

(CH3)(C2H5)CH  •  CH2  •  CH(C02H)2 

90°-91° 

244°-246° 

tert.  Amylmalonic 

(CH3)2(C2H5)C-CH(C02H)2 

— 

238° 

sec.  Amylmalonic 

(C2H6)2CH.CH(C02H)2 

52°-53° 

242°-245° 

Methylisobutylmalonic 

(CH3)2CH-  CH2-  C(CH3)(C02H)2 

122° 

230°-235° 

Ethylisopropylmalonic 

(CH3)2CH.C(C2H5)(C02H)2 

131°-131-5° 

232°-233° 

Cetvlmalonio     . 

CH3.[CH2]15-CH(C02H)2 

121-5°-122° 

— 

Dicetylmalonic 

[CH3.(CH2)15.]2:C(C02H)2       - 

86°-  87° 

— 

Dioctylmalonic 

[CH3-(CH2)7.]2:C(C02H)2 

75° 

338°-340° 

MALONIC    ACID    DERIVATIVES  309 

iodide,  sodium  iodide  being  separated  at  the  same  time.  The  resulting  products  are 
higher  homologues  of  the  malonic  ester  and  hence  yield  the  corresponding  homologues 
of  malonic  acid  on  hydrolysis.  The  hydrolysis  of  the  esters  of  dibasic  acids  by  alkali 
takes  place  in  two  stages,  the  second  ester  group  being  hydrolysed  more  slowly  than  the 
first. 

Treatment  of  ethyl  malonate  (1  mol.)  with  sodium  (1  or  2  atoms)  results  in  the  evolu- 
tion of  hydrogen  and  the  formation  of  the  solid  mono-  or  di-sodiomalonic  ester  : 


"NTa  •  fTlV2  '     25  f^     ^-C02  •  C2H5 

<C02.C2H5    '          ^2<C02.C2H6 

The  sodium  of  the  monosodio  -compound  can  be  replaced  by  an  alkyl  group  and  the 
remaining  methylene  hydrogen  then  replaced  by  sodium,  which  can  subsequently  be 
substituted  by  an  alkyl  group  different  from  the  first. 

An  example  of  this  synthesis  is  as  follows  : 

CH3I  -  Nal  +  C 


Hydrolysis  of  the  final  ester  yields  Methylethylmalonic  Acid. 
Homologues  of  succinic  acids  can  be  obtained  as  follows  : 


r^r\     /*i  TT 

4-  Tir    PTT^          2 '  ^2n5 

PO     P  TT  -Dr'^-'Jt:1<^-,pTj 

Ethyl  sodiomethylinalouate  Ethyl  a-bromopropionate 

C02  •  C2H5 
NaBr  +  CH,- 


C02  •  C2H5 

When  this  complex  ester  is  saponified  and  the  acid  thus  formed  heated  to  expel  C02 
from  one  of  the  carboxyl  groups  united  to  the  same  carbon  atom,  symmetrical  dimethyl- 
succinic  acid  is  obtained  : 

C02H                                           CO2H    C02H 
CH3  -  C  •  CH<^E2H  -  CO2  +  CH3  •  CH CH .  CH3 

I  ^"^3 

CO2H 

Also  2  mols.  of  ethyl  sodiomethylmalonate  (or  ethyl  sodiomalonate  or  its  homologues) 
can  be  condensed  in  ethereal  solution  by  means  of  bromine  or  iodine  : 

CO2-C2H5  C02-C2H5 

CO    P  TT 
2CH3  •  CNa<£Q2 ;  £2^5  +  I2  =  2NaI  +  CH3 .  C—        —  C .  CH3 

C02-C2H5  C02.C2H5 

Ethyl  dimethylethanetetracarboxylate 

Hydrolysis  of  this  ester  gives  the  corresponding  acid  and  the  latter  loses  2CO2  on 
heating,  yielding  dimethylsuccinic  acid.  Similiarly,  succinic  acid  may  be  obtained  from 
ethyl  sodiomalonate,  and  homologous,  symmetrical  alkylsuccinic  acids  by  condensirg 
2  mols.  of  ethyl  sodioalkylmalonate  containing  alkyl  groups  higher  than  methyl  : 

CO2H     CO2H  CO2H     C02H 

i    I  i     r 

CH3  •  C—     — C  •  CH3  =  2CO2  +  CH3  -  CH CH .  CH3 

Dimethyleuccinic  acid 
C02H     C02H 


310 


ORGANIC    CHEMISTRY 


SUCCINIC  ACIDS,  C4H6O4  (Two  Isomerides) 

(a)  ORDINARY  SUCCINIC  ACID  (Butandioic  or  Ethylenesuccinic  Acid), 
CO2H'CH2'CH2'CO2H,  occurs  in  nature  in  various  plants,  in  the  unripe  grape,  in  certain 
lignites,  and,  more  especially,  in  amber,  from  which  it  is  obtained  by  distillation  or 
fermentation. 

Alcoholic  fermentation  also  yields  a  small  amount  of  succinic  acid,  which  thus  forms 
a  normal  constituent  of  wine.  Ehrlich  (1909)  has  shown  that,  in  the  alcoholic  fermenta- 
tion of  sugar,  the  succinic  acid  is  formed  from  the  glutamic  acid  resulting  from  the 
decomposition  of  the  cells  of  the  ferment.  Numerous  syntheses  also  lead  to  the  formation 
of  succinic  acid  ;  e.g.  the  reduction  by  hydrogen  of  fumaric  or  maleic  acid,  these  being 
unsaturated  dibasic  acid?,  C4H404  ;  hydrolysis  of  ethylene  cyanide,  CN  •  CH2  •  CH2  •  CN, 
obtained  from  ethylene  bromide,  C2H4Br2  (see  above)  ;  reduction  of  the  hydroxy-acids, 
malic  and  tartaric  acids,  by  means  of  hydricdlc  acid  ;  heating  of  ethyl  ethanetricarboxylate 
above  its  melting-point : 


'=    CO9 


CH9.C09H 


CH9.COpH 


CHo.COoH 


Various  alkylsuccinic  acids  are  obtained  by  syntheses  with  ethyl  malonate. 
HOMOLOGUES  OF  SUCCINIC  ACID 


Name  of  acid 

Composition 
of  acid 

Melting-point 
of  acid 

Melting-point 
of  the  anhydride 

Methylsuccinic            .          .          . 

C6H804 

112° 

37° 

Ethylsuccinic    .          . 

C6H10O4 

99° 

Liquid 

symm.  Dimethylsuccinic  (fumaroid)     . 

C6Hio04 

209° 

43° 

,,                     „                 (maleinoid)    . 

C6H10O4 

129° 

91° 

asymm.              „                    .... 

C7H12O4 

140°-141° 

31° 

Propylsuccinic            .         ..         .          ,          , 

C7H12O4 

91° 

Liquid 

Isopropylsuccinic 

C7H12O4 

114° 

,, 

symm.  Methylethylsuccinic  (fumaroid) 

C7H1204 

180° 

— 

„                           ,,                (maleinoid) 

C7H1204 

101°-102° 

Liquid 

asymm. 

C7H12O4 

104° 

,, 

Trimethylsuccinic      ..... 

C7H12O4 

152° 

38° 

Butylsuccinic    ...... 

CsH14O4 

81° 

— 

Isobutylsuccinic         ..... 

C8H14O4 

109° 

Liquid 

symm.  Methylpropylsuccinic  (fumaroid) 

CsH14O4 

158°-160° 

„ 

„                         ,,                    (maleinoid) 

CgH14O4 

92°-93° 

,, 

„       Methylisopropylsuccinic  (fumaroid)  . 

CsH1404 

174°-175° 

.46° 

,,                         „                         (maleinoid) 

CgH14O4 

125°-126° 

Liquid 

,,       Diethylsuccinic  (fumaroid) 

C8Hj404 

189°-190° 

,, 

,,                         „         (maleinoid) 

CsH1404 

129° 

,, 

asymm.                 „               .... 

CgH1404 

86° 

» 

o  a  -Dimethyl  -a  -ethylsuccinic 

CsH14O4 

139°-140° 

,, 

Tetramethylsuccinic            . 

CsH14O4 

200° 

147° 

Isoamylsuccinic          ..... 

C9H1604 

75°-76° 

— 

n-Hexylsuccinic          ..... 

CioHi8O4 

87° 

57° 

symm.  Dipropylsuccinic  (fumaroid) 

CioHi804 

182°-183° 

Liquid 

,,                         „             (maleinoid)    . 

C10H1g04 

119°-121° 

,, 

n-Heptylsuccinic        ..... 

C11H20O4 

90°-91° 

— 

symm.  Diisobutylsuccinic  (fumaroid) 

Ci2H2204 

195° 

Liquid 

...                        ,,               (maleinoid) 

Ci2H22O4 

97°-98° 

,, 

Tetrae  thy]  succinic 

Ci2H22O4 

149° 

86° 

Tetrapropylsuccinic  ..... 

Pi6H3004 

137° 

— 

PYROTARTARICACIDS  311 

Pure  succinic  acid  crystallises  in  monoclinic  plates,  m.pt.  182°,  b.pt.  235°,  having 
a  disagreeable  acid  taste.  When  subjected  to  distillation,  it  loses  water  and  yields 
succinic  anhydride.  Its  solubility  in  water  is  1  :  20  at  the  ordinary  temperature,  and 
it  is  highly  resistant  to  the  action  of  oxidising  agents. 

Calcium  succinate  is  soluble  in  water  ;  ferric  succinate  is  used  in  the  estimation  of  iron. 

(b)  ISOSUCCINIC     ACID     (Ethylidenesuccinic     or     Methylpropandioic      Acid), 

CO  H 

^u,  forms  needles  or  prisms  which  melt  at  130°  with  evolution  of  CO2  and 


formation  of  propionic  acid.  It  is  more  soluble  in  water  than  its  isomeride,  but  yields 
no  anhydride.  It  is  obtained  by  synthesis  from  ethyl  malonate,  or  by  treatment  of 
«-bro  mo  propionic  acid  with  KCN  and  subsequent  hydrolysis. 

PYROTARTARIC  ACIDS,    C5H8O4  (Four  Isomerides) 

(a)  GLUTARIC  ACID  (Normal  Pyrotartaric  or  Pentadioic  Acid), 
COaH-CH^CHa-CHg-COijH,  forms  crystals  melting  at  97-5°  and  is  readily 
soluble  in  water.  It  is  obtained  from  1  niol.  of  methylene  iodide  and  2 
mols.  of  ethyl  sodiomalonate,  the  intermediate  product  being  hydrolysed 
and  2  mols.  of  C02  then  eliminated  by  heating  : 

2  •  C2H5 


CHI   =  2NaI  +  CH 


22 


CH?-C02H 


CH2  =  2CO2  +    CH2 

CH<rC°2H  CH2-C02H 

'^-tKx.prj  TT  * 

'^2"-  Glutaric  acid 

(6)  PYROTARTARIC  ACID  (Methylbutandioic  Acid), 

C02H-CH2-CH-C02H 

CH3 

is  formed,  together  with  pyruvic  acid,  when  ordinary  tartaric  acid  is  subjected 
to  dry  distillation  •,  synthetically  it  is  prepared  from  ethyl  acetoacetate.  It 
forms  small  triclinic  crystals  melting  at  117°  and  its  anhydride  is  known. 
Since  it  contains  an  asymmetric  carbon  atom,  it  exists  in  two  optically  active 
stereoisomerides . 

HIGHER  HOMOLOGUES 

The  dialkylsuccinic  acids  (see  above]  contain  two  asymmetric  carbon  atoms 
and  give  rise  to  important  cases  of  stereoisomerism.  Together  with  the  homo  - 
logues  of  glutaric  and  adipic  acids,  they  are  found  among  the  products  of  decom- 
position of  the  terpenes  and  hence  serve  to  establish  the  composition  of  these. 

/3-METHYLADIPIC  ACID,  CO2H-CH2-CH(CH3)-CH2-CH2-C02H,  melts 
at  85°  and  occurs  along  with  menthol,  &c.,  in  the  oxidation  products  of 
numerous  ethereal  oils. 

AZELAIC  ACID,  CO2H  •  [CH2]7  -CO2H,  is  now  obtained  easily  and  cheaply  by  decom- 
posing the  ozonides  of  oils  and  of  the  corresponding  unsaturated  fatty  acids,  especially 
of  oleic  acid  (E.  Molinari,  Soncini,  and  Fenaroli,  1906-1908).  The  acid  originally  cost 
£24  per  kilo,  but  can  now  be  sold  for  a  few  shillings.  It  is  obtained  well  crystallised  from 
benzene  or  from  water,  in  which  it  dissolves  easily  in  the  hot  but  only  slightly  in  the 
cold  (1-648  per  cent,  at  55°,  0-817  per  cent,  at  44-5°,  0-214  per  cent,  at  22°,  and  0-212  per 
cent,  at  15°);  it  is  soluble  also  in  alcohol  or  ether,  melts  at  106°,  and  gives  a  calcium  salt 
which  dissolves  in  cold  but  not  in  hot  water. 


312  ORGANIC    CHEMISTRY 

HIGHER  HOMOLOGUES  OF  OLEFINEDICARBOXYLIC  ACIDS 


Name  of  Acid 

Structure 
X  =  COaH 

Melting-point 
of  acid 

Melting-point 
of  the 
anhydride 

Boiling-point 
of  the 
anhydride 

Dimethylfumaric    (a-methyl- 

CHS-CX:CX-CH3 

239°-240° 

.  



mesaconic) 

Ethylfumaric  (y-methylmesa- 

conic)       .... 

CH3-CH2-CX:CHX 

194°-196° 

— 

— 

Ethylmaleic     (y-mcthylcitra- 

conic)       .... 

CH,-CHa-CX:CHX 

100° 

Liquid 

229° 

a-Methylitaconic  . 

CH2:CX-CHX-CH8 

150°-151° 

62°-63° 

— 

V-Methylitaconic  . 

CH8-CH:CX-CH2X 

166°-167° 

— 

— 

Propylfnmaric 

CH3-CH2.€H2-CX  :  CHX 

174°-175° 

— 

— 

Propylmaleic 

CH3-CH2-CH2-CX:CHX 

93°-95° 

•  — 

243°-245° 

y-Ethylitaeonic    . 

CH3-CH2.CH2  :  CX-CH2X 

162°-167° 

— 

— 

Allylsuccinic 

CH2:  CH-CH,-CHX-CH2X 

92°-93° 

Liquid 

About  20° 

Isopropylfumaric  . 

(CH3)2CH-CX:CHX 

185°-186° 

— 

•  — 

Isopropylmaleic   . 

(CH3)2CH.CX:CHX 

91°-93° 

+  5° 

138°  (61  mm.) 

•yy-Uimethylitaconic  (teraconic) 

(CH3)2C:CX-CH2X 

160°-161° 

44° 

197°  (22  mm.) 

•y-Methylene-y-methylpyro- 

tartaric    .... 

CH2:  C(CH,)-CHX-CH2X 

146°-147° 

Liquid 

— 

Methylethylmaleic 

CH3-CH2-CX  :CX-CH3 

— 

,, 

230° 

a-Ethylitaconic    .          .        .. 

CH2:CX-CHX-CH2-CH3 

150° 

52° 

•  —  • 

ay-Dimethylitaconic      .         . 

CH3-CH:CX-CHX-CH3 

202° 

Liquid 

131°  (16  mm.) 

aa-Dimethylitacouic 

CH2:CX-CX(CH3)2 

142-5° 

,, 

210°-215° 

Butylfumaric 

C2H5-CH2-CH2-CX  :  CHX 

170° 

•  — 

— 

Butylmaleic          .          ... 

C2H5-CH2-CH2-CX  :  CHX 

80° 

—  , 

— 

•y-Propylitaconic  . 

C2H6-CH2-CH  :  CX-CH2X 

159°-160° 

— 

— 

Isobutylfumaric 

(CH3)2CH-CH2-CX  :  CHX 

183° 

— 

— 

Isobutyhnalcic     .         .         . 

(CH3)2CH-CH2-CX  :  CHX 

78°-81° 

— 

— 

•y-Isopropylitaconic 

(CH3)2CH-CH  :  CX-CH2X 

189°-192  ° 

— 

•  — 

Metliylpropylmalcic 

CH3-CH2-CH2-CX  :  CX-CH, 

•  — 

Liquid 

241°-242° 

Mcthylisopropylmaleic 

(CH3)2CH-CX  :CX-CHa 

— 

,, 

240°-242° 

Diethylmaleic 

CgHg-CX  :  CX-CgHj 

— 

„ 

239°-240° 

•y-Methyl-a-ethylitaconic 

CH3-CH:CX-CHX.C2HS 

136° 

" 

143°  (12  mm.) 

C6H804 
CeH6O3 
C6H8O4 


B.  UNSATURATED  DIBASIC  ACIDS 
I.  OLEFINEDICARBOXYLIC  ACIDS,  CWH2W_4O4 


C4H4O4  Fumaric  acid 

„  Maleic  acid    . 

C5HeO4  Mesaconic  acid 

„  Citraconic  acid 

„  Itaconic  acid 


Glutaconic  acid 
Pyrocinchonic  acid 


Pyrocinchonic  an- 
hydride 


COoH-CH 

II 
CH-C02H 

HC-CO2H 

II 
HC-CO2H 

CO2H.C-CH3 

II 
CH-CO2H 

CH3.C-CO2H 

II 
CH-C02H 

CH2:C-CO2H 

CH2-C02H 

CO2H  -  CH  :  CH  •  CH2 .  CO2H 
CH3.C-C02H 


CH3.C-C02H 
CH3-C— CO, 

CHo-C— CO- 


>0 


melts  at  200°  (sublimes) 

130°  boils  at  160° 
202° 
91° 
161° 
132° 


o/3-Hydromucic  acid  C02H  •  CH2  •  CH2  -  CH  :  CH-C02H 
/3y-         „  „      C02H.CH2.CH:CHjCH2.CO2H 


96°  boils  at  223° 

169°  (stable) 
195°  (labile) 


FUMARIC    AND    OLEIC    ACIDS  318 

As  far  as  the  carboxyl  groups  are  concerned,  these  acids  have  chemical 
properties  similar  to  those  of  the  saturated  dibasic  acids  (see  p.  305),  whilst 
as  they  are  unsaturated  compounds,  they  are  able  to  combine  with  2  atoms  of 
hydrogen  or  halogen  or  with  1  mol.  of  a  halogen  hydracid. 

They  are  usually  prepared  from  the  mono-  and  di-halogen  substitution 
products  of  succinic  acid  and  its  homologues  by  removing  either  1  mol.  of 
halogen  hydracid  (by  heating  with  KOH)  or  2  atoms  of  halogen  : 

CH2  •  C02H  HBr  +  C02H  •  CH 

I  —  II 

CHBr-C02H  CH-C02H 

Monobromosuccinic  acid  Fumaric  acid 

Distillation  of  the  saturated  dibasic  hydroxy-acids  results  in  the  removal 
of  1  mol.  of  H20  and  the  formation  of  unsaturated  acids. 

The  most  interesting  cases  of  stereoisomerism  were  considered  on  p.  21. 
When  fumaric  acid  is  either  heated  or  treated  with  PC15,  POC13,  or  P205,  it 
is  converted  into  maleic  anhydride.  Maleic  acid  is  transformed  into  fumaric 
acid  by  heating  at  200°  in  a  sealed  tube  or  by  the  action  of  bromine  or  of 
various  acids  in  presence  of  sunlight. 
.  FUMARIC  ACID  (trans-Butendioic  Acid),  C4H4O4  or  CO2H-CH, 

II 
HC-C02H 

forms  small  white  prisms  which  have  a  marked  acid  taste  and  are  almost 
insoluble  in  water  ;  it  does  not  melt  but  sublimes  at  about  200°,  subsequently 
losing  water  and  becoming  converted  largely  into  maleic  anhydride. 

It  is  moderately  widespread  in  certain  vegetable  organisms,  e.g.  in  fungi, 
truffles,  Iceland  moss,  and  especially  in  Fumaria  officinalis.  It  can  be  prepared 
by  the  ordinary  synthetical  methods  and  also  by  the  action  of  phosphorus 
and  bromine  on  succinic  acid,  the  product  obtained  being  decomposed  by 
heating  with  water. 

It  is  stereoisomeric  with  maleic  acid  (see  p.  21)  and  its  reduction  to  normal 
succinic  acid  by  means  of  nascent  hydrogen  confirms  its  constitution,  which 
is  also  deduced  from  the  decomposition  of  the  corresponding  ozonide  (Harries). 

The  Silver  Salt,  C4H204Ag2,  is  slightly  soluble  in  water,  and  the  same  is  the 
case  with  the  barium  salt,  C4H2O4  Ba  +  3H20,  which  in  boiling  water  becomes 
insoluble  and  separates  in  the  anhydrous  form,  C4H204Ba. 

MALEIC  ACID  (cis-Butendioic  Acid),  C4H4O4  or  CH-C02H  forms  large 

II 
CH-CO2H 

prisms  melting  at  130°  and  having  an  unpleasant  taste  ;  it  boils  at  160°, 
losing  water  and  becoming  converted  partially  into  maleic  anhydride.  It  is 
readily  soluble  in  water. 

Its  ready  transformation  into  maleic  anhydride  is  explained  by  the  stereo- 
chemical  relations  considered  on  p.  21  et  seq.,  and  in  many  general  methods 
of  preparing  the  acid,  the  anhydride  is  first  obtained. 

The  Barium  Salt,  C4H2O4Ba  +  H2O,  is  soluble  in  hot  water,  from  which 
it  crystallises  well. 

Electrolysis  of  the  alkali  salts  of  fumaric  and  maleic  acids  yields  acetylene. 
When  heated  with  sodium  hydroxide  at  100°,  these  two  acids  are  converted 
into  inactive  maleic  acid. 

ITACONIC  ACID  (Methylenesuccinic  Acid),  C5H6O4  or  CH2  :  C-CO2H,  is  a  white 

CH2-C02H 

substance  melting  at  161°  and  non-volatile  in  steam.  It  is  obtained  by  the  action  of 
water  on  its  anhydride,  the  latter  being  formed  by  the  interaction  of  citraconic  anhydride 


314  ORGANIC-CHEMISTRY 

and  water  at  150°.  Hydrogen  converts  it  into  pyrotartaric  acid  and  permanganate  into 
hydroxyparaconic  acid.  On  electrolysis  it  yields  allene,  CH2  :  C  :  CH2. 

MESACONIC  ACID  (Methylfumaric  Acid),  C5H6O4  or  CO2H-C-CH3,  is  formed  by 

II 
HC-CO2H 

heating  citraconic  or  itaconic  acid  with  water  at  200°  or  by  treatment  of  citraconic  acid 
with  dilute  HNO3  or  concentrated  NaOH,  or  with  traces  of  bromine  in  sunlight.  It  is 
difficultly  soluble  in  water,  melts  at  202°,  and  does  not  distil  in  steam.  When  electrolysed 
it  forms  allylene,  CH3-C  :  CH,  while  with  hydrogen  it  gives  pyrotartaric  acid  and  with 
permanganate,  pyrotartaric  and  oxalic  acids.  It  forms  a  barium  salt,  C5H404Ba  +4H2O. 
CITRACONIC  ACID  (Methylmaleic  Acid), C5H604  or  CH3-C  CO2H,  is  formed  from 

II 
HC  CO2H 

the  corresponding  anhydride  and  water.  It  melts  at  91°,  differs  from  the  two  preceding 
acids  by  being  very  soluble  in  water,  distils  in  steam  and  readily  gives  the  anhydride 
again.  On  electrolysis  it  yields  allylene,  while  with  hydrogen  it  forms  pyrotartaric  acid. 

GLUTACONIC  ACID,  C5H6O4  or  CO2H-CH  :  CH-CH2-CO2H,  is  isomeric  with  the 
three  preceding  acids  and  is  obtained  by  hydrolysing  the  corresponding  ester  with  HC1  ; 
it  melts  at  132°  and  the  hydrogen  of  its  CH2-group  is  replaceable  by  sodium  (see  p.  309). 

Of  the  higher  homologues  of  these  acids  mention  may  be  made  of  the  alkylitaconic 
acids,  with  which,  on  heating  with  NaOH  solution,  the  position  of  the  double  linking 
changes,  giving  alkylmesaconic  and  alkylaticonic  tfcids  (Fittig),  e.g.  isdbutylaticonic  acid 
(CH3)2CH-CH  :  CH.CH(CO2H).CH2.CO2H,  which  melts  at  93°  ;  with  alkalis  these  acids 
undergo  the  reverse  change  to  some  extent. 

The  calcium  and  barium  salts  of  the  alkylmesaconic  acids  are  readily  soluble  in  water, 
and  those  of  the  alkylitaconic  acids  slightly  soluble. 

Of  these  homologous  acids,  the  following  deserve  mention  : 

PYROCINCHONIC  ACID  (Dimethylmaleic  or  Dimethylfumaric  Acid),  C6H8O4  or 
CO2H-C  =  C-CO2H.  Of  the  two  stereoisomerides,  only  dimethylmaleic  acid  was  until 

I         I 
CH3  CH3 

recently  known  and  then  only  as  the  anhydride,  namely,  pyrocinchonic  anhydride  (m.pt. 
96°,  b.pt.  223°).     Dimethylmaleic  acid  cannot  exist  in  the  free  state,  as  it  immediately 
gives  up  water,  forming  the  anhydride  ;  its  esters  are,  however,  known. 
CH8.C.COv 

The    anhydride,  ^)O,  may  be  prepared  in  various  ways,  e.g.  by  distilling  in 

CHg-C-CXK 

steam  the  product  of  the  interaction  of  pyrotartaric  acid  and  sodium  succinate.  But 
a  better  yield  is  obtained  by  first  preparing  the  riitrile  of  methylacetoacetic  acid  and 
distilling  this  in  a  vacuum. 

According  to  A.  Bischoff,  the  stereoisomeride,  Dimethylfumaric  Acid,  CH3-C-CO2H. 

II 
C02H.C-CH3 

could  not,  owing  to  stereochemical  considerations,  be  formed  in  the  free  state.  But 
Fittig  and  Kettner  (1899)  and  also  E.  Molinari  (1900)  have  succeeded  in  isolating  it  in 
various  ways.1  It  forms  white  crystals,  m.pt.  152°  ;  its  amido -derivatives  have  also 
been  prepared. 

1  Fittig  and  Kettner,  making  use  of  the  property  of  variant  acids,  homologous  with  citraconic  acid,  of  yielding 
the  corresponding  fumaroid  isomeride  when  simply  heated'with  alkali,  obtained  from  pyrocinchonic  anhydride,  the 
two  acids  :  one  melting  at  151°,  to  which  is  ascribed  the  constitution  CH2 :  C-CO2H  (p-methylitaconic  acid),  and 

I 

CH,-  CH-COjH 
another  melting  at  240°  and  regarded  as  CH,-C-COaH  (dimelhylfumaric  acid).     It  is   highly   probable,    for  the 

II 

COjH-C-CH, 
following  reasons,  that  the  latter  constitution  should  be  attributed  to  the  acid  melting  at  151°. 

By  a  long  series  of  investigations  (1881  to  1896),  Korner  and  Menozzi  showed  that,  in  general,  the  treatment 
of  a-amino-acids  with  methyl  iodide  in  presence  of  caustic  potash  yields  the  corresponding  betaines  (condensed  alkyl- 
substituted  amines) ;  but  the  p-amino-acids,  if  similarly  treated,  always  yield  the  corresponding  unsaturated,  non- 
nitrogenous  acids  of  the  fumaroid  type  (betaines  being  probably  formed  as  intermediate  products).  As  the  same 
f)-amino-acid  can  be  obtained  from  the  two  stereoisomeric  unsaturated  acids,  this  general  reaction  renders  it  possible  to 
pass  from  a  malenoid  unsaturated  acid  to  the  corresponding  fumaroid  stereoisomeride  By  applying  this  reaction 
to  pyrocinchonic  anhydride,  E.  Molinari  arrived  at  the  expected  stereoisomeride  (dinxthylfumaric  acid),  melting 
at  152°. 


TRIBASIC    ACIDS 

Bauer  (1904)  made  the  interesting  observation  that  dimethylfumaric  acid  and,  in 
general,  compounds  containing  carboxyl  or  alkyl  or  phenyl  groups  or  bromine  atoms 
united  to  two  carbon  atoms  connected  by  a  double  linking  do  not  unite  with  bromine. 

HYDROMUCONIC  ACIDS,  C6H8O4.  Of  these  are  known  (1 )  the  a/3 -unsaturated  acid, 
C02H-CH2-CH2-CH  :  CH-C02H,  which  is  stable  and  melts  at  169°  ;  with  permanganate 

S  y  ft  a 

it  yields  succinic  acid.  (2)  The  unstable  /3y-acid,  C02H.CH2-CH  :  CH-CH2-CO2H,  which 
melts  at  195°  and  is  obtained  by  reducing  muconic  acid  ;  when  heated  with  alkali,  it  is 
converted  into  the  stable  isomeride,  whilst  with  permanganate  it  gives  malonic  acid, 
C02H.CH2.C02H. 

Of  the  DIOLEFINEDICARBOXYLIC  ACIDS,  only  Muconic  Acid,  CO2H-CH  : 
CH-CH  :  CH-CO2H,  melting  above  260°,  need  be  referred  to. 

Of  the  ACETYLENEDICARBOXYLIC  ACIDS,  mention  will  be  made  only  of 
Acetylenedicarboxylic  (Butindioic)  Acid,  CO2H-C  i  C-CO2H,  which  melts  and 
decomposes  at  175°  ;  it  crystallises  with  2H2O.  It  is  obtained  on  removing  HBr  from 
dibromo-  or  isodibro  mo -succinic  acid  by  means  of  potash. 

Diacetylenedicarboxylic  Acid,  CO2H-C  i  C-C  :  C-CO2H  +  H2O,  turns  dark  red  in 
the  light  and  explodes  at  177°.  When  reduced  with  sodium  amalgam,  it  yields  hydro  - 
muconic  acid. 

Tetracetylenedicarboxylic  Acid,  CO2H-C  i  C-C  :  C-C  I  C-C  i  C-CO2H,  forms  white 
crystals  which  blacken  rapidly  in  the  light  and  explode  violently  on  heating. 

C.  TRIBASIC  ACIDS 

These  have  usually  been  obtained  synthetically  and  are  not  very  stable 
since  they  readily  yield  carbon  dioxide  and  dibasic  acids  on  heating  ;  their 
esters,  however,  exhibit  increased  stability.  Their  properties  and  methods  of 
preparation  vary  according  as  the  carboxyl  groups  are  united  to  one  or  to 
various  carbon  atoms. 

Of  the  many  such  acids  known,  the  following  may  be  mentioned  : 

TRICARBALLYLIC  ACID  (symm.  waw-  Propanetricarboxylic  or  Pentanedioic-3- 
methyloic  Acid),  CH2-C02H,  occurs  in  the  deposits  left  on  concentrating  beet-sugar  juices 

CH-CO2H 

CH2-CO2H 

in  vacuo.  Synthetically  it  is  obtained  by  converting  glycerol  into  the  tribromohydrin 
or  allyl  tribromide,  which  is  treated  with  potassium  cyanide  to  give  the  corresponding 
tricyano -compound,  the  latter  being  then  hydrolysed  to  tricarballylic  acid  ;  the  con- 
stitution of  the  acid  is  thus  proved.  This  acid  forms  white,  prismatic  crystals  melting 
at  166°.  It  can  also  be  prepared  by  reducing  unsaturated  tricarboxylic  acids  (e.g.  aconitic 
acid). 

CO2H  CO2H  CO2H 

CAMPHORONIC  ACID  (aa/3-Trimethylcarballylic  Acid),  CH3-C C. CH2 

CH3     CH3 

is  formed  on  oxidising  camphor,  of  which  it  serves  to  indicate  the  constitution  ;  it  melts 
at  135°.' 

ACONITIC  ACID  is  an  unsaturated  tribasic  acid  of  the  constitution  C02H-CH2- 
C(CO2H) :  CH-CO2H,  and  is  found  in  beetroot,  sugar-cane,  Aconitum  napellus,  &c.  It  is 
obtained  synthetically  by  eliminating  C02  from  citric  acid  by  the  action  of  heat  or  of 
various  reagents.  It  melts  at  191°,  losing  C02,  and  forming  itaconic  anhydride.  It 
dissolves  readily  in  water  and  with  nascent  hydrogen  generates  tricarballylic  acid,  its 
structure  being  indicated  by  this  reaction. 


316  ORGANIC    CHEMISTRY 

D.  TETRABASIC  ACIDS 

These  are  formed  from  ethyl  sodiomalonate  (see  p.  309)  by  means  of  an  unsaturated 
ester,  e.g.  of  fumaric  acid.  When  heated,  they  lose  C02,  forming  tribasic  and,  better, 
dibasic  acids. 

Olefinetetracarboxylic  Acids  are  also  known. 


FF.  DERIVATIVES  OF  THE  ACIDS 
I.  HALOGEN  DERIVATIVES 

One  or  more  of  the  hydrogen  atoms  of  an  alkyl  group  united  with  carboxyl 
can  be  replaced  by  halogens,  the  carboxyl  group  being  left  intact.  The 
halogen  derivatives  of  the  acids,  thus  obtained,  are  more  markedly  acid  in 
character  than  the  original  substances.  They  are  obtained  by  the  action  of 
chlorine  or  bromine  in  sunlight  or,  better,  by  heating  the  acid  with  the  halogen 
in  presence  of  a  little  water  or  sulphur. 

On  the  other  hand,  the  hydroxyl  of  the  carboxyl  group  can  be  replaced, 
forming  acid  halides  ;  —CO  —X  (by  treating  the  acid  with  phosphorus  chloride 
or  bromide).  That  the  halogen  has  replaced  the  hydroxyl  group  is  shown 
by  the  fact  that  these  acid  halides  yield  the  original  acids  when  treated  with 
cold  water,  whilst  halogens  are  not  displaced  from  alkyl  residues  in  this  way. 
These  acid  chlorides  and  bromides  readily  give  the  monochloro-  and  mono- 
bromo-  acids  when  treated  further  with  chlorine  or  bromine. 

(a)  HALOGENATED  ACIDS 

When  the  carbon  atom  (a),  to  which  the  carboxyl  group  is  attached,  is 
not  united  directly  with  hydrogen  [e.g.  in  trimethylacetic  acid,  (CH3)3C-C02H], 
bromine  is  not  taken  up  (see  p.  315).  The  constitution  of  a  halogenated  acid, 
or  rather  the  position  of  the  halogen  atom,  is  deduced  from  that  of  the  cor- 
responding hydroxy-acid  (containing  a  hydroxyl -group  in  place  of  the  halogen) 
obtained  by  heating  the  halogenated  acid  with  sodium  carbonate  solution  or 
with  water  and  lead  oxide. 

On  the  other  hand,  the  passage  from  hydroxy-acid  to  the  corresponding 
halogenated  acid  can  be  effected  by  treatment  with  phosphorus  chloride  or 
bromide. 

The  acid  character  becomes  more  marked  on  passing  from  the  iodo-  to  the 
bromo-  and  then  to  the  chloro-compounds  and  also  increases  with  the  number 
of  halogen  atoms  in  the  molecule. 

While  the  a-halogenated  acids  readily  yield  the  corresponding  hydroxy- 
acids,  the  /3-acids  yield  the  corresponding  unsaturated  acids  (see  p.  292)  and 
may  even  lose  C02,  giving  unsaturated  hydrocarbons.  But  the  y-halogenated 
acids,  when  heated  with  sodium  carbonate  solution  or  with  water  alone,  give 
up  a  molecule  of  halogen  hydracid  and  yield,  not  the  unsaturated  acids,  but 
lactones  (see  p.  295). 

When  halogenated  acids  are  prepared  by  the  interaction  of  an  unsaturated 
acid  with  a  halogen  hydracid  (e.g.  HI),  the  halogen  becomes  attached  to  the 
least  hydrogenated  carbon  atom  (see  p.  96).  Thus,  with  a  A^-acid,  where 
the  double  linking  is  between  the  a-  and  |3-carb«n  atoms,  the  halogen  unites 
with  the  latter. 

The  halogenated  and  poly-halogenated  acids  exhibit  isomerism,  since  the 
halogen  atom  may  be  joined  to  the  a,  ft,  y,  &c.,  carbon  atom,  or  several  halogen 
atoms  may  be  united  with  one  and  the  same  carbon  atom  or  with  different 
ones. 


ACIDHALIDES  317 

When  heated  with  potassium  cyanide,  the  mono-haloid  acids  yield  cyano 
acids  : 

CH2C1-COOK  +  KCN  =  KC1  +  CN-CH2-COOK. 

Potassium  chloroacetate  Potassium  cyanoacetate 

With  sodium  sulphite  they  give  dibasic  sulpho-acids,  the  sulphonic  group 
of  which  is  readily  replaced  by  hydroxyl  by  boiling  with  alkali : 

Na2S03  +  Cl-CH2-COONa  =  NaCl  +  S03Na-CH2-COONa. 

Sodium  sulphoacetate 

With  reference  to  the  affinities  of  the  halogenated  acids,  see  Note  on  p.  268. 

MONOCHLORACETIC  ACID  (Chlorethanoic  Acid),  CH2C1-COOH,  is  prepared  by 
the  general  method,  that  is,  by  passing  dry  chlorine  into  hot  acetic  acid  in  presence  of 
acetic  anhydride,  phosphorus,  or  sulphur.  It  forms  rhombic  crystals  which  corrode 
the  flesh  and  melt  at  62°  ;  on  solidification  an  unstable  modification  is  obtained  which, 
for  some  time,  melts  at  52°  ;  it  boils  at  186°.  When  heated  with  water  or  alkali  it  gives 
Hydroxyacetic  Acid  (glycollic  acid),  OH-CH2-CO2H;  with  ammonia  it  yields  Amino- 
acetic  Acid  (glycineor  glycocoll),  NH2  •  CH2  •  C02H. 

The  properties  of  the  other  halogenated  acids  are  given  in  the  Table  on 
the  next  page. 

(b)  ACID  HALIDES 

Of  these  compounds  the  most  important  are  the  chlorides  of  the  acid 
radicals,  which  are  termed  acichlorides  or  chloranhydrides .  Although  acetyl 
chloride,  CH3-CO-C1,  is  readily  obtainable,  it  has  not  been  found  possible  to 
prepare  formyl  chloride,  H-  CO-  Cl,  a  mixture  of  CO+HC1  being  always  obtained. 

These  compounds  are  usually  colourless  liquids,  which  have  pungent  odours 
and  fume  strongly  in  the  air,  the  moisture  in  the  latter  liberating  hydrogen 
chloride.  Their  boiling-points  are  below  those  of  the  corresponding  acids, 
and  they  distil  without  decomposing  ;  the  higher  members  are,  however,  solid 
and  do  not  distil  unchanged  even  in  a  vacuum. 

The  principal  methods  for  preparing  these  substances  are  as  follows  : 

(a)  The   organic   acid  is   heated   for   a   short   time   on  the   water-bath 
with  PC15  (with  higher  acids.),  PC13  (with  acids  below  C10)  or,  in  some  cases, 
sulphuryl  chloride,  S02C12 : 

CUH23-CO-OH  +  PC15  =  CnH23-CO-Cl  +  HC1  +  POC135 

Laurie  acid 

the   phosphorus    oxychloride   and    hydrochloric    acid    being    eliminated   by 
distillation  in  vacua  ;  or, 

3CH3-CO-OH  +  2PC13  =  3CH3-CO-C1  +  3HC1  +  P203, 

the  acetyl  chloride  thus  formed  being  separated  by  distillation,  the  P203 
being  left  in  the  residue. 

(b)  With  thionyl  chloride  the  acids  yield  the  chloranhydrides,  the  other 
products  formed  at  the  same  time  being  volatile  and  hence  easily  removable  : 
X-CO-OH  +  SOC12  =  X-CO-C1  +  HC1  +  S02. 

(c)  In  some  cases  the  acid  is  treated  simply  with  HC1  in  presence  of  a 
dehydrating  agent,  (P205)  :   CH3-CO-OH  +  HC1  =  H20  +  CH3-CO-C1. 

CHEMICAL  PROPERTIES.  The  great  reactivity  of  the  chlorine  atom 
of  these  substances  renders  them  of  considerable  importance  in  chemical 
syntheses.  Water,  ammonia  (amines),  and  alcohols  decompose  them  in  the 
cold  with  great  violence  : 

CH3-CO-C1  +  H20  =  HC1  +  CH3-CO-OH 

CH3-CO-C1  +  NH3  =  HC1  +  CH3-CO-NH2  (acetamide) 

CH3-CO-C1  +  C2H5-OH  =  HC1  +  CH3-CO-OC2H6  (ethyl  acetate), 


318 


ORGANIC    CHEMISTRY 


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A  NH  YD  RIDERS  319 

With  organic  salts  they  yield  anhydrides  : 

CH3-CO-C1  +  CH3-CO-ONa  =  NaCl  +  CH3-CO-0-CO-CH3. 
Sodium  amalgam  reduces  them  to  aldehydes  and  then  to  alcohols. 

ACETYL  CHLORIDE  (Ethanoyl  Chloride),  CH3-CO-C1,  is  a  liquid  boiling  at  51° 
and  having  the  sp.  gr.  1-105  at  20°.  It  is  prepared  by  mixing  5  parts  of  glacial  acetic 
acid  and  4  parts  of  phosphorus  trichloride  in  the  cold,  heating  for  a  short  time  at  40° 
and,  after  evolution  of  HC1  ceases,  distilling  the  acetyl  chloride  and  purifying  it  by  recti- 
fication. Water  decomposes  it  with  development  of  heat. 

It  is  employed  in  organic  synthesis,  since  it  readily  yields  acetyl  derivatives  of  alcohols 
and  of  primary  and  secondary  amines. 

The  commercial  product  costs  3s.  to  4s.  per  kilo,  and  the  chemically  pure  14*. 

The  boiling-points  of  the  higher  homologues  of  acetyl  chloride  rise  with  the  molecular 
weight  and,  with  isomerides,  that  with  the  normal  constitution  has  the  highest  boiling- 
point  ;  the  specific  gravity  diminishes  as  the  molecular  weight  increases. 

Acetyl  iodide  boils  at  108°,  propionyl  chloride  at  108°  (the  bromide  at  104°  and  the 
iodide  at  127°)  ;  normal  butyryl  chloride  boils  at  101°  (the  bromide  at  128°  and  the  iodide 
at  146°)  and  isobutyryl  chloride  at  92°  (the  bromide  at  116°)  ;  isovaleryl  chloride  boils  at 
114°(the  bromide  at  143°  and  the  iodide  at  168°)  and  trimethylacetyl  chloride,  (CH3)3G-  CO-  Cl, 
at  105°. 

II.  ANHYDRIDES 

The  anhydrides  of  organic  acids  were  discovered  by  C.  Gerhardt  in  1851 
and  correspond  with  those  of  the  inorganic  acids,  that  is,  they  may  be  regarded 
as  products  of  the  condensation  of  2  mols.  of  acid  with  expulsion  of  1  mol. 
of  water.  And  here  also,  the  organic  anhydrides,  when  they  are  at  all  soluble, 
take  up  water  and  regenerate  the  acids.  With  organic  acids,  however,  more 
varied  and  interesting  cases  are  presented,  since  2  mols.  of  different  acids 
can  condense  (mixed  anhydrides),  while  internal  anhydrides  can  be  formed  by 
condensation  between  the  two  carboxyl  groups  of  a  dibasic  acid. 

The  anhydrides  may  be  regarded  also  as  oxides  of  acid  radicals,  e.g.  acetic 

anhydride,  cH^CO>0'  °r  acetyl  °xide'  (CH3'C°)20- 

PROPERTIES.  The  first  members  of  the  series  are  liquid,  the  higher  ones 
solid  ;  they  generally  dissolve  but  slightly  in  water,  their  transformation  into 
acids  being  very  slow.  They  have  a  neutral  reaction  and  are  soluble  in  ether 
and  often  in  alcohol. 

With  ammonia  and  the  primary  and  secondary  amines,  they  form  amides 
and  ammoniacal  salts:  (CH3CO)20  +  2NH3  =  CH3-CO-NH2  (acetamide) 
+  CH3-CO-ONH4  (ammonium  acetate). 

When  heated  with  an  alcohol,  they  give  the  corresponding  ester  and  acid  : 

(CH3CO)20  +  C2H5-OH  =  CH3-COOC2H5  +  CH3-COOH. 

With  halogen  hydracids  in  the  hot  they  yield  the  halides  of  the  acids  and 
the  free  acids  :  (CH3CO)2O  +  HC1  =  CH3-CO-C1  +  CH3-COOH. 

Aldehydes  combine  with  anhydrides,  forming  esters,  while  sodium  amalgam 
reduces  anhydrides  to  aldehvdes  and  alcohols. 

GENERAL  METHODS  OF  PREPARATION,  (a)  By  the  action  of  acid 
chlorides  on  the  dry  alkali  salts  of  the  corresponding  acids  : 

CH3-CO-C1  +  CH3-COONa  =  NaCl  +  cH3.CO>a 

(6)  The  same  result  is  obtained  by  the  action  of  phosphorus  oxychloride 
(or  phosgene  COC12)  on  a  mixture  of  the  alkali  and  alkaline-earth  salts  of 
the  corresponding  acid,  the  acid  chloride  being  formed  as  an  intermediate 
product. 


320  ORGANIC    CHEMISTRY 

(c)  The  higher  anhydrides  are  obtained  from  the  corresponding  acids  by 
the  action  of  acetyl  chloride  : 

CH3-COC1  +  2X-COOH  -  HC1  +  CH3-COOH  +  (X-CO)aO. 

(d)  The  formation  of  anhydrides  from  the  acids  by  the  subtraction  of 
water  (by  means  of  P205)  gives  low  yields,  the  best  being  obtained  with 
palmitic  and  stearic  acids  (using  acetic  anhydride  in  the  hot  as  dehydrating 
agent). 

The  properties  of  the  best-known  anhydrides  are  given  in  the  following 
Table  : 


Formula 

Name 

Melting- 
point 

Boiling-point 

Specific  gravity 

(CH3.CO)2O 

Acetic  anhydride 

,  

136-5° 

1-078  (at  21°) 

(C2H5.CO)20 

Propionic  anhydride  ~    v 

— 

168-6° 

1-034  (at  0°) 

(C3H7.CO)20 

norm.  Butyric  anhydride 

— 

192° 

0-978  (at  12-5°) 

5> 

Iso  butyric  anhydride 

— 

182° 

0-958  (at  16-5°) 

(C4H9.CO)20 

Isovaleric  anhydride 

— 

215° 

— 

» 

Trimethylacetic  anhydride 

— 

190° 

— 

(C5HU.CO)20 

norm.  Caproic  anhydride 

— 

242° 

0-928  (at  17°) 

(C6H13.CO)20 

CEnanthic  anhydride 

+  17° 

257° 

0-912  (at  17°) 

(C7H15.CO)20 

Caprylic  anhydride 

—1° 

186°  (15  mm.) 

— 

(C8H17-CO)20 

Pelargonic  anhydride 

+  16° 

207° 

— 

(CUH23.CO)20 

Laurie  anhydride    . 

+  41° 

166°  (vacuum) 

— 

(Ci3H27.CO)20 

Myristic  anhydride 

+  51° 

198° 

— 

(C^H^-CO^O 

Palmitic  anhydride 

55°-66° 

— 

— 

(C17H3B.CO)20 

Stearic  anhydride  .          . 

72° 

— 

— 

ACETIC  ANHYDRIDE  (Ethanoic  Anhydride),  (CH3-CO)2O,  is  of  some  importance 
industrially  owing  to  its  formation  of  acetyl  derivatives  with  alcohols  or  with  primary 
or  secondary  amines.  It  is  a  suitable  reagent  for  determining  how  many  hydroxyl  groups 
an  organic  substance  contains  (see  Acetyl  Number,  p.  189).  It  is  a  colourless,  very  mobile 
liquid,  sp.  gr.  1-078  at  21°,  b.pt.  136-5°,  and  has  a  pungent  odour. 

It  is  prepared  by  dropping  5  parts  of  acetyl  chloride  on  to  7  parts  of  dry  powdered 
sodium  acetate,  which  is  kept  cool  meanwhile.  The  mixture  is  subsequently  gently  heated 
for  a  short  time  and  the  anhydride  then  distilled  off  on  a  sand-bath.  It  is  purified  by 
redistillation  in  presence  of  a  little  anhydrous  sodium  acetate,  the  portion  boiling  at 
the  correct  temperature  being  collected.  It  is  also  prepared  industrially  by  method  (b) 
given  above  (Ger.  Pats.  161,882  ;  also  132,605  and  146,690). 

Commercial  acetic  anhydride  costs  about  £18  per  quintal,  and  the  highly  purified 
product  (puriss.)  £24. 

The  anhydrides  of  di-  and  poly-basic  acids  are  not  of  great  importance  and  are  con- 
sidered to  some  extent  in  dealing  with  the  corresponding  acids  (succinic,  pyrocinchonic, 
&c.) ;  with  water  they  yield  the  acids  with  moderate  readiness  (see  pp.  305  and  314). 

III.  HYDROXY-ACIDS 
A.  SATURATED  DIVALENT  MONOBASIC  ACIDS 

These  may  be  regarded  as  derived  from  monobasic  acids  by  the  substitu- 
tion of  an  atom  of  hydrogen  (not  that  of  the  carboxyl  group)  by  a  hydroxyl 
group.  These  acids  possess,  at  the  same  time,  acidic  and  alcoholic  characters 
and  are  hence  termed  divalent  monobasic  acids  or  divalent  alcohol  acids.  The 
hydroxyl  and  the  carboxyl  groups  may  be  substituted  at  the  same  time,  the 
compounds  then  exhibiting  the  general  properties  of  the  acids  and  alcohols, 
in  addition  to  new  and  special  characters  varying  with  the  position  occupied 
by  the  carboxyl  relatively  to  the  hydroxyl  (see  pp.  295  and  297). 


HYDROXY-ACIDS  821 

They  are  usually  syrups  which  may  undergo  crystallisation  ;  in  comparison 
with  the  corresponding  fatty  acids,  the  hydroxy-acids  are  more  soluble  in 
water  and  in  alcohol,  but  less  soluble  in  ether.  They  do  not  distil  unchanged 
and  often  lose  water,  forming  anhydrides. 

GENERAL  METHODS  OF  PREPARATION,  (a)  By  oxidising  dihydric 
alcohols  so  as  to  transform  the  primary  alcoholic  group  into  carboxyl. 

(6)  By  boiling  unsaturated  acids  with  sodium  hydroxide,  so  that  a  mole- 
cule of  water  is  added  at  the  double  bond. 

(c)  By  substituting  the  halogen  of  a  monohalogenated  monobasic  acid  by 
hydro xyl ;    this  is  effected  by  treatment  with  KOH  or  with  silver  acetate, 
the  diacetate  formed  in  the  latter  case  being  hydrolysed  by  heating  with 
sodium  carbonate  : 

CH2C1'COOH  +  H20  =  OH:CH2-C02H  +  HC1. 

Monochloracetic  acid  Glycollic  acid 

(d)  a -Hydroxy-acids  are  obtained  by  hydrolysing  the  nitriles  formed  on 
treating  the  aldehydes  or  ketones   (having  one  atom  of  carbon  less)  with 
hydrocyanic  acid  : 

CH3-CH<™  +  2H20  =  NH3  +  CH3-CH(OH)-COOH. 

Ethyl  idenecyanohydrin 

Glycolcyanohydrin,  OH  •  CH2  •  CH2  •  CN,  yields  ethylenelactic  acid, 
OH-CH2-CH2-COOH. 

(e)  By  the  action  of  nitrous  acid  on  amino-acids  : 

COOH-CH2-NH2  +  NO- OH  =  H20  +  N2  +  COOH-CH2-OH. 

Glycocoll 

( / )  By  reducing  aldehydic  or  ketonic  acids  : 

CH3-CO-COOH  +  H2  =  CH3-CH(OH)-COOH. 

Pyruvic  acid  Lactic  acid 

(g)  By  oxidation  of  acids  containing  a  tertiary  carbon  atom,  >CH-COOH, 
with  permanganate. 

PROPERTIES  AND  CONSTITUTION.  The  constitutions  of  these  acids 
can  always  be  deduced  from  the  syntheses  indicated  above.  That  they  con- 
tain an  alcoholic  group  is  shown  by  the  fact  that  the  hydroxylic  hydrogen 
can  be  replaced  by  an  alkyl  group,  giving  true  non-hydrolysable  ethers. 
Similarly  the  presence  of  a  carboxyl  group  is  shown  by  the  formation  of 
hydrolysable  esters.  The  isomerism  exhibited  is  the  same  as  with  the  haloid 
derivatives  of  the  acids. 

The  number  of  alcoholic  hydroxyl  groups  is  determined  by  the  acetyl 
number  (see  p.  189).  The  reactivity,  which  corresponds  with  the  dissociation 
constant,  increases  with  the  proximity  of  the  hydroxyl  to  the  carboxyl  group. 

a-,  /3-,  •/-,  and  g-hydroxy-acids  are  distinguished  also  by  the  products 
resulting  from  the  elimination  of  one  or  more  molecules  of  water. 

Thus,  a-hydroxy-acids,  when  heated,  lose  2  mols.  of  H20  per  2  mols. 
of  acid,  the  hydroxyl  group  of  the  one  reacting  with  the  carboxyl  group  of 
the  other  ;  the  compound  formed  is  called  a  lactide  and  is  a  double  ester, 
which  yields  the  acid  again  on  hydrolysis  with  hot  water  or  dilute  acid  : 

CO-CH-CH3 

COOH-CH(OH)-CH3  | 

=  2H20  +  60 

CH3-CH(OH)-COOH  I 

CH3-CH-CO 

2  mols.  Lactic  acid  Lactide 

II  21 


322  ORGANIC    CHEMISTRY 

Further,  a-hydroxy -acids,  if  heated  with  sulphuric  acid,  yield  the  aldehydes 
or  keton.es  from  which  they  can  originate  (see  above),  formic  acid  being  also 
formed. 

The  |3-acids,  however,  lose  only  1  mol.  of  water,  giving  unsaturated  acids 
(see  p.  292),  while,  when  boiled  with  10  per  cent,  potassium  hydroxide  solution, 
they  give  at  the  same  time  aft-  and  ay-  unsaturated  acids— a  reversible  reaction 
leading  to  a  position  of  chemical  equilibrium  ;  when  heated  with  sulphuric 
acid  they  form  acids  of  the  acrylic  series. 

The  y-  and  S-acids  lose  1  mol.  of  water,  yielding  lactones  (internal 
anhydrides)  : 

OH-CH2-CH2-CH2-COOH  =  H20  +  CH2-CH2-CH2-CO 

•y-Hydroxybutyric  acid 

o 


Butyrolactone 

which  are  almost  always  formed  when  attempts  are  made  to  liberate  these 
hydroxy-acids  from  their  salts.  -The  lactones  are  neutral  liquids  soluble  in 
water,  alcohol,  and  ether  ;  they  dis.til  unchanged  and  with  alkali  form  the 
salts  of  the  corresponding  hydroxy-acids. 

When  the  hydroxy-acids  are  heated  with  sulphuric  acid,  they  furnish  the 
corresponding  fatty  acids. 

GLYCOLLIC  ACID  (Hydroxyacetic  or  Ethanoloic  Acid),  OH-CH2-COOH,  crystal- 
lises in  needles  or  plates  melting  at  80°,  and  is  soluble  in  water,  alcohol,  or  ether.  In 
nature  it  is  found  in  immature  eggs  and  in  the  leaves  of  the  wild  vine. 

It  can  be  obtained  by  the  general  methods  .given  above  and  also  by  oxidising  alcohol 
or  glycol  with  dilute  nitric  acid  or  by  reducing  oxalic  acid  with  nascent  hydrogen.  It  is 
usually  prepared  by  hydrolysing  monochloracetic  acid  with  KOH  [general  method  (c)]. 

Of  some  interest  is  the  formation  of  the  various  anhydrides  of  glycollic  acid,  these 
being  formed  by  the  removal  of  1  mol.  of  H2O  from  two  mols.  of  the  acid  as  follows  : 

(1)  From  the  two  alcohol  groups,  giving   a   true   ether  with  two  free  acid  groups, 


.- 

rnnw  diglycollic  acid,  m.pt.  148°;    (2)  from  the  two  carboxyl  groups;   this 

OH  •  CH  •  CO 
should  give  the  anhydride  of  glycollic  acid,  r  'nrC>0»  wmch  ig  n°t  yet  known  ; 

vJ-ii  •  v_y-Tl2  •  \j\J 

(3)    from   one  alcohol   and   one    acid  group,  giving    a   true  ester,   glycolglycollic   acid, 

s  gives  eit 

CH    CO 
* 


OH  •  CH  •  CO 

.  ~>O.     Also  loss  of  2H2O  from  the  two  alcoholic  and  acidic  groups  gives  either 
COOH  • 


(1)  Diglycollic  anhydride  (anhydride    and    ether    at    the    same    time), 

j-2  • 

(melting  at  97°  and  boiling  at  240°),  or,  when  each  molecule  of  water  separates  from  1 

CTT     CO 

alcoholic  and  1  acidic  group,   (2)  the  isomeric  glycollide,    O^^2'    r  ^>0,  melting  at  86°. 


Glycollic  acid  forms  a  calcium  salt,  (OH-CH2-COO)2Ca  +  3H20,  insoluble  in  water. 
The  most  important  derivative  of  glycollic  acid  is 

GLYCOCOLL  (Glycine  or  Aminoacetic  or  Aminoethanoic  Acid),  COOH  CH2-NH2, 
which  is  the  first  member  of  the  amino-acid  series  so  important  to  vegetable  physiology. 
It  is  obtained,  together  with  secondary  products,  by  the  action  of  concentrated 
ammonia  solution  on  monochloracetic 


CHoCl-COOH  +  2NH3  =  NH4C1  +  NH2  .  CH2  .  COOH. 

It  is  always  formed  in  the  decomposition  of  hippuric  acid  (benzoylglycocoll)  with  HC1, 
or  by  the  action  of  acid  or  alkali  on  gelatine. 

It  can  also  be  obtained  by  the  reduction  of  ethyl  cyanocarboxylate  by  means  of  nascent 
hydrogen  or  from  cyanogen  and  boiling  hydriodic  acid. 

Its  homologues  are  prepared  synthetically  in  various  ways,  e.g.  by  treating  aldehyde- 
ammonias  with  hydrocyanic  acid  and  hydrolysing  the  amino  -cyanides  thus  obtained  with  HC1. 

Glycocoll  crystallises  in  rhombic  columns  soluble  in  4  parts  of  water  but  insoluble 
in  alcohol  or  ether  ;  it  has  a  sweetish  taste  and  melts  and  decomposes  at  230°. 


LACTIC    ACIDS  32B 

The  fact  that  the  amino -group  cannot  be  expelled  by  hydrolysis 
establishes  the  structure  of  glycocoll.  It  behaves  as  both  acid  and 
base,  forming  salts  with  acids  and  also  with  bases.  Its  copper  salt 
separates  in  large,  dark  blue  needles  on  dissolving  cupric  oxide  in  hot  glycocoll 
solution  :  (C2H4O2N)2Cu  +  H20.  With  ferric  chloride  it  gives  an  intense 
red  coloration.  When  heated  with  baryta,  it  loses  C02,  forming  methyl- 
amine  ;  with  nitrous  acid  it  gives  glycollic  acid. 

Various  alkyl  and  other  derivatives  have  been  obtained  synthetically  from 
glycocoll : 

CH2-NH-COCH3  CH2-NH-CH3  CH2— N(CH3)3 

I  ;       I  ;         I       I 

COOH  COOH  CO — O 

Aceturic  acid  Sarcosine  Betaine 

(derived  from  riaffeine  and  from  creatine)        (from  the  beet) 

With  nitrous  acid,  the  esters  of  glycocoll  yield  ETHYL  DIAZOACETATE, 

N\ 
NH2-CH2-COO-C2H5  +  HN02  =  2H20  +    ||  ">CH-COOC2H5,    which    is  -a 

W 

yellow  oil  boiling  at  141°  and  readily  decomposes  and  reacts  with  evolution 
of  nitrogen  ;  it  serves  for  the  synthesis  of  pyrazole. 

LACTIC  ACIDS,  OH-C2H4-C02H 

The  two  structural  isomerides  foreseen  by  theory  are  known  :  a-  and 
/3-hydroxypropionic  acids.  Also  the  a-acid  exists  in  two  stereoisomeric 
forms  (I  =  laevo-  and  d  =  dextro-rotatory)  owing  to  the  presence  of  an 
asymmetric  carbon  atom  (p.  18)  and  in  an  inactive  form  (i  =  inactive),  con- 
sisting of  a  mixture  in  equal  proportions  of  the  two  stereoisomerides.  These 
lactic  acids  form  anhydrides  similar  to  those  of  glycollic  acid  (see  above). 

The  lactic  acids  give  Uffelman's  reaction,  that  is,  they  cause  the  amethyst- 
coloured  solution  obtained  on  adding  a  drop  of  ferric  chloride  to  a  dilute 
salicylic  acid  solution  to  turn  yellow  ;  this  reaction  is  also  given  by  citric, 
oxalic,  and  the  tartaric  acids. 

(1)  i-ETHYLIDENELACTIC  ACID  (I  +  d)  (2-Propanoloic  or  a-Hydroxy- 
propionic  Acid  or  Ordinary  Lactic  Acid  of  Fermentation),  CH3-CH(OH)-COOH, 
is  found  in  milk  rendered  acid  by  the  action  of  the  lactic  acid  bacillus  (see 
Fig.  114,  p.  122),  in  milk-sugar  (also  cane-  and  grape-sugars,  gum,  starch,  &c.) 
which  undergoes  acid  fermentation  (lactic  fermentation)  even  in  absence  of 
air,  although  oxygen  facilitates  the  change.  Cabbage  fermented  with  vinegar 
and  salt  (Sauerkraut),  gastric  juice,  putrefied  cheese,  fresh  fodder  siloed,  and 
fermented  muscular  juices  and  the  brain1  also  contain  free  lactic  acid. 

When  pure  it  melts  at  18°  and  boils  at  120°  under  12  mm.  pressure,  but 
usually  it  forms  a  dense  syrup  soluble  in  water,  alcohol,  or  ether.  It  is  opti- 
cally inactive,  as  it  consists  of  a  racemic  mixture  of  dextro-  and  Isevo-acids 
(see  pp.  19  and  20).  The  two  modifications  can  be  separated  by  crystallisation 

1  It  appears  now  to  be  proved  that  the  lactic  acid  in  the  human  organism  is  formed  in  proportion  to  the 
muscular  and  cerebral  work,  and,  together  with  carbon  dioxide,  which  is  also  a  waste  product  of  the  cells  of 
the  organism  during  wakefulness,  produces  sleep.  While  we  sleep,  the  blood  carries  off  these  waste  products  more 
easily,  the  cells  then  recovering  their  function  and  their  sensibility.  The  connection  between  sleep  and  fatigue  is 
well  known  and  is  shown  not  only  by  the  fact  that  after  great  muscular  or  cerebral  fatigue  sleep  is  more  profound, 
but  by  the  results  of  the  following  experiment :  if  the  blood  of  a  very  tired  dog  is  injected  into  the  veins  of  another 
dog  in  a  normal  state,  this  dog  soon  exhibits  signs  of  great  fatigue  and  goes  to  sleep  ;  these  results  are  not  observed 
if  the  blood  injected  is  that  of  a  non-fatigued  dog.  During  heavy  muscular  labour,  the  air  expired  contains  more 
CO2  than  in  a  state  of  repose  and  more  still  than  during  sleep.  The  carbon  dioxide  diminishes  the  oxygen  so 
much  needed  by  the  muscles  and  brain,  so  that  the  activity  of  these  remains  depressed.  As  is  well  known,  lactic 
acid  has  a  depressing  action  on  the  nervous  cells,  injection  of  the  acid  into  the  veins  of  any  person  inducing  symp- 
toms of  fatigue  and  sleepiness  and  finally  sleep.  The  continuance  of  sleep  is  due  to  the  fact  that  the  blood 
flows  more  slowly  to  the  brain,  to  which  it  hence  carries  less  oxygen.  It  appears,  indeed,  to  be  proved  that  in 
general  five  or  six  hours'  sleep — very  deep  for  two  hours — is  sufficient  for  the  blood  to  wash  away  these  waste 
products  of  active  cellular  work  and  to  restore  activity  to  all  the  cerebral  centres. 


324  ORGANIC    CHEMISTRY 

of  the  strychnine  salts  or  by  cultivating  in  the  solution  Penicillium  glaucum, 
which  first  destroys  the  Isevo-acid  (see  p.  22).  When  heated,  the  active  acid 
is  transformed,  to  the  extent  of  one-half,  into  the  optical  eriantiomorph,  so 
that  the  inactive  racemic  acid  is  obtained.  If  kept  in  a  desiccator,  it  is  partly 
converted  into  anhydride  owing  to  loss  of  water.  When  distilled  under  reduced 
pressure,  it  yields  water,  carbon  dioxide  and  lactide  (see  above).  If  heated 
with  dilute  sulphuric  acid  it  decomposes,  like  many  other  a-hydroxy-acids, 
into  acetaldehyde  and  formic  acid. 

PREPARATION.  Various  processes  have  been  tried  for  the  preparation  of  lactic  acid. 
For  instance,  3  kilos  of  cane-sugar  and  15  grms.  of  tartaric  acid  are  dissolved  in  13  litres  of 
boiling  water.  In  a  few^days'  time,  after  the  cane-sugar  has  been  converted  into  glucose 
and  levulose,  4  litres  of  acid  milk  and  100  grms.  of  putrefied  cheese  (also  1-5  kilo  of  zinc 
carbonate  to  fix  the  lactic  acid,  which  otherwise  would  arrest  the  lactic  fermentation)  are 
added  and  the  mixture  left  for  a  week  at  a  temperature  of  40°  to  45°,  by  which  means 
the  maximum  production  of  lactic  acid  is  obtained.  The  acid  separates  as  zinc  lactate  in 
crystalline  crusts  which,  after  purification  (by  recrystallisation),  are  suspended  in  water 
and  decomposed  with  H2S  in  order  to  remove  the  zinc  as  insoluble  sulphide.  The  filtered 
liquid  is  concentrated  to  a  syrupy  consistency  and  then  extracted  with  ether,  which  does 
not  dissolve  the  impurities  (zinc  salts,  mannitol,  &c.)  ;  on  evaporation  of  the  ether,  pure 
syrupy  lactic  acid  is  obtained.1  Besides  the  decomposition  of  the  sugar,  various  secondary 
reactions  always  accompany  lactic  fermentation,  and  the  yield  of  the  acid  is  scarcely 
20  per  cent,  of  the  weight  of  the  sugar  taken. 

A  better  yield  is,  however,  obtained  by  Larrieu's  process  (Fr.  Pat.  206,506),  which  con- 
sists in  treating,  say,  900  kilos  of  starch  with  100  kilos  of  malt  and  with  hot  water  to  bring 
the  temperature  to  50°,  this  being  finally  raised  to  75°,  the  mass  being  continually  stirred. 
Half  a  kilo  of  ammonium  nitrate  is  next  added  to  the  vat  and  then  the  lactic  ferment,  the 
temperature  being  maintained  at  50°  to  60°  for  20  to  30  days,  and  the  acid  formed  being 
gradually  half  saturated  with  soda.  The  mass  is  ultimately  filtered  and  the  liquid  con- 
centrated to  a  sp.  gr,  of  1-21  (25°  Be.),  mixed  with  500  kilos  of  powdered  calcium  carbonate 
and  filtered.  The  solution  of  calcium  lactate  is  decomposed  with  the  calculated  quantity  of 
sulphuric  acid,  the  calcium  sulphate  being  removed  by  filtration  and  the  aqueous  lactic 
acid  evaporated  to  a  syrupy  consistency. 

Jacquemin  prepares  the  acid  from  worts  similar  to  those  employed  in  breweries  (barley 
mashed  at  50°  with  malt,  then  boiled  to  destroy  the  diastase  and  cooled  to  45°)  by  the 
addition  of  pure  lactic  ferment  and  calcium  carbonate.  After  5  to  6  days,  the  mash  is 
filtered  and  concentrated,  the  calcium  lactate  being  then  decomposed  in  the  usual  way  with 
sulphuric  acid. 

Dreher  works  in  a  similar  manner,  but  with  glucose  solutions  containing  1  per  cent,  of 
nutrient  substances  for  the  ferment  (e.g.  sodium  phosphate,  nitre,  salt,  &c.). 

Industrially,  however,  lactic  acid  is  now  always  obtained  from  milk  residues  (whey 
or  molasses  of  milk-sugar,  which  remain  after  the  removal  of  the  butter  from  the  milk 
in  the  separator  ;  also  cheese  by  coagulation  with  rennet  in  the  hot).  The  whey  is  con- 
centrated in  open  vessels  or,  better,  in  vacuum  pans,  to  16°  Be.,  and  is  then  introduced 
into  wooden  vessels  in  which,  at  a  temperature  of  40°,  the  lactic  ferment  is  added  in  the 
form  either  of  part  of  the  liquid  from  a  previous  fermentation  or  of  putrefied  cheese. 
Powdered  chalk  is  added  to  neutralise  the  acid  formed,  the  liquid  being  stirred  from  time 
to  time  and  the  fermentation  allowed  to  continue  for  10  to  12  days.  After  decantation, 
the  calcium  lactate  is  decomposed  with  dilute  sulphuric  acid,  the  liquid  mass  being  well 
mixed.  In  some  cases,  before  the  calcium  lactate  is  decomposed,  it  is  separated  by  con- 
centrating the  solution,  and  is  recrystallised  from  a  little  hot  water,  which  should  dissolve 
20  per  cent,  of  it.  The  calcium  sulphate  formed  is  removed  by  passing  the  mass  through 

1  Kiliani  treats  500  grms.  of  inverted  sugar  with  250  grms.  of  water  and  15  grms.  of  sulphuric  acid  at  50°  to  60° 
for  2  hours,  and  then  adds  gradually  400  c.c.  of  concentrated  caustic  soda  solution  (1 : 1),  the  liquid  being  kept 
boiling  meanwhile. 

The  soda  is  subsequently  neutralised  with  50  per  cent,  sulphuric  acid  and  the  solution  left  for  24  hours  to 
deposit  crystalline  sodium  sulphate.  The  lactic  acid  is  extracted  with  alcohol — which  does  not  dissolve  the  sul- 
phate— the  alcohol  being  recovered  by  distillation.  The  crude  lactic  acid  remaining  is  diluted,  saturated  with 
Zinc  carbonate  and  evaporated  ;  the  zinc  lactate  is  then  allowed  to  separate  and  is  filtered  off,  redissolved  in  hot 
water  and  decomposed  with  HjS.  After  filtration,  the  liquid  is  concentrated  in  vacua,  pure  lactic  acid  being  thus 
obtained. 


LACTIC    ACIDS  325 

a  filter-press  (see  figure  in  the  section  on  Sugar)  and  the  clear  lactic  acid  solution  con- 
centra  ted  in  a  double -or  triple-effect  apparatus  until  it  attains  a  concentration  of  50  per 
cent.  The  further  small  quantity  of  gypsum  which  is  then  deposited  is  separated  by 
filtration,  the  resulting  yellowish  brown  liquid  representing  commercial,  crude,  50  per  cent. 
(by  weight)  lactic  acid.  This  should  not  contain  more  than  1-5  per  cent,  of  ash,  and 
should  not  contain  sulphate  or  reduce  Fehling's  solution. 

The  lactic  acid  prepared  from  the  molasses  of  milk-sugar  factories  is  more  impure  than, 
the  above. 

According  to  a  patent  filed  in  1905,  lactic  acid  is  also  obtained  from  a  mixture  of  bran 
and  barley,  and  an  English  patent  (No.  26,415,  1907)  describes  the  preparation  of  pure, 
concentrated  lactic  acid  by  the  distillation  of  the  commercial  50  per  cent,  acid  in  a  rapid 
current  of  air  or  of  an  indifferent  gas. 

Very  pure  lactic  acid  is  obtained  by  extracting  the  crude  product  with  amyl  alcohol — 
which  does  not  dissolve  the  impurities  (sugar,  gum,  mineral  substances) — and  distilling 
in  vacua.  The  impurities  are  estimated  by  titrating  the  acid  with  normal  caustic  potash 
solution  in  presence  of  phenolphthalein. 

USES  AND  PRICE.  Until  a  few  years  ago  the  uses  of  lactic  acid  were  limited  to  the 
preparation  of  soluble  lactates  for  medicinal  purposes,  but  its  manufacture  has  recently 
been  considerably  extended  owing  to  its  employment  in  the  dyeing  of  wool,  silk,  &c., 
in  place  of  tartaric  acid,  tartar  and  oxalic  acid,  for  the  reduction  of  the  chromium  com- 
pounds with  which  wool  to  be  treated  with  fast  dyes  (alizarin  dyes,  &c.)  is  mordanted. 
For  the  same  reasons  it  is  advantageously  employed  in  the  chrome  tanning  of  skins,  its 
value  in  this  case  being  sometimes  regarded  as  due  to  its  ability  to  keep  calcium  salts  in 
solution  and  thus  prevent  the  formation  of  certain  harmful  deposits.  The  crude  50  per 
cent,  acid  is  most  commonly  sold,  and  it  is  necessary  to  ascertain  whether  by  50  per  cent, 
is  meant  50  kilos  per  100  litres  or  per  100  kilos  of  solution  ;  in  the  former  case  the  strength 
of  the  acid  is  only  43  per  cent,  by  weight  (i.e.  100  kilos  contain  43  kilos  of  acid). 

Commercial,  brown,  50  per  cent,  lactic  acid  costs  about  64s.  per  quintal  ;  the  paler, 
yellow  product  of  the  same  strength,  105s.  ;  the  pure  (sp.  gr.  1-21),  3s.  Id.  per  kilo,  and 
the  chemically  pure  12s.  per  kilo.  Italy  imported  the  following  quantities  of  pure  lactic 
acid  at  104s.  per  quintal :  996  quintals  in  1907  ;  650  in  1908  ;  520  in  1909  ;  and  490  in 
1910,  when  the  amount  exported  was  51  quintals.  The  import  duty  in  Italy  is  12s.  per 
quintal. 

Salts  of  Lactic  Acid  are  generally  soluble  to  some  extent  in  water.  Calcium 
lactate,  (C8H5O3)2Ca  +  5H2O,  forms  mammillary  aggregates  of  white  needles  soluble  in 
9-5  parts  of  cold  water,  and  in  all  proportions  in  hot  water  ;  it  is  insoluble  in  cold  alcohol. 
The  water  of  crystallisation  is  evolved  in  a  vacuum  desiccator  or  on  heating  to  100°. 
At  250°  it  loses  H20,  giving  calcium  dilactate,  which  is  less  soluble  in  alcohol  than  the 
original  salt.  Zinc"  lactate  and  ferrous  lactate  crystallise  with  3H20,  the  latter  in  yellowish 
crystals  ;  both  are  used  in  medicine. 

ALANINE,  CH3-CH(NH2)  -COOH,  is  obtained  from  the  corresponding  aldehyde- 
ammonia  by  the  action  of  hydrocyanic  acid.  From  the  inactive,  synthetical  compound, 
the  active  stereoisomerides  are  separated  by  means  of  the  strychnine  or  brucine  salts. 
The  action  of  PC15  expels  both  the  hydroxyl-  and  the  amino-groups,  giving  lactyl  chloride, 
CH3  •  CHC1  •  COC1,  which  gives  a-chlorpropionic  acid,  CH3  •  CHC1  •  COOH,  when  treated  with 
water. 

(2)  d-ETHYLIDENELACTIC   ACID    (Paralactic  or  Sarcolactic  Acid)  differs  from 
ordinary  lactic  acid  only  in  the  greater  solubility  of  its  zinc  salt  ( +  2H20),  and  the  less 
solubility  of  its  calcium  salt  (  +  4H2O).      It  is  found  in  Liebig's  extract  of  meat,  and  it  is 
contained  in  the  muscular  juices,  and  is  also  formed  in  certain  lactic  fermentations. 

(3)  Z-ETHYLIDENELACTIC  ACID  is  formed  during  the  fermentation  of  aqueous  cane- 
sugar  solutions  by  Bacillus  acidi  Icevolactici. 

(4)  ETHYLENELACTIC  ACID  (Hydracrylic,  /3-Hydroxypropionic  or  3-Propanoloic 
Acid),  OH  -CH2  -CH2-COOH,  differs  from  its  isomerides  in  that,  when  heated,  it  loses  a  mole- 
cule of  water,  giving,  not  the  anhydride,  but  acrylic  acid,  CH2  :  CH-CO2H.     Further,  with 
oxidising  agents  it  gives,  not  acetic  acid,  but  oxalic  acid  aijd  carbon  dioxide.     It  con- 
tains no  asymmetric  carbon  atom  and  is  hence  optically  inactive.     It  can  be  prepared 
synthetically  from  (1)  /3-iodopropionic  acid,  or  (2)  ethylene,  CH2  :  CH2,  by  addition  of 
hypochlorous   acid,  giving    OH-CH2-CH2Cl,^which    is  then  converted  into  the  nitrile 


326  ORGANIC    CHEMISTRY 

OH  •  CH2  •  CH2  •  CN,  hydrolysis  of  the  latter  giving  ethylcnelactic  acid.  The  acid  is  a 
colourless,  syrupy  liquid  and  forms  a  calcium  salt  ( +  2H2O)  and  a  readily  soluble  zinc 
salt  ( +  4H2O). 

HYDROXYBUTYRIC  ACIDS,  OH-C3H6-C02H 

Five  isomerides  are  theoretically  possible,  four  being  known  :  two  a-acids,  one  fi-acid, 
and  one  y-acid  (prepared  only  as  salts). 

a -HYDROXYBUTYRIC  ACID,  CH3-CH2-CH(OH) -CO2H,  melts  at  43°  and  is  syn- 
thesised  as  the  inactive,  racemic  form,  which  can  be  resolved  into  its  active  components 
by  means  of  brucine  (see  p.  22). 

a-HYDROXYISOBUTYRIC  ACID  (Acetonic  or  2-Methyl-2-propanoloic  Acid), 
OH  -C(CH3)2-C02H,  melts  at  79°,  boils  at  212°,  and  is  obtainable  by  various  synthetical 
methods  from  dimethylacetic  acid,  acetocyanohydrin,  a-aminobutyric  acid,  &c. 

/3-HYDROXYBUTYRIC  ACID,  CH3-CH(OH) -CH2-CO2H,  is  obtained  by  oxidising 
aldol  or  reducing  acetoacetic  acid,  these  methods  of  formation  indicating  its  constitution. 
It  forms  a  syrup  and  its  Isevo-isomeride  is  found  in  the  blood  and  in  diabetic  urine. 

HIGHER  HYDROXY-ACIDS 

H-HYDROXYVALERIC  ACID,  CH3-CH2-CH2-CH(OH)  -C02H,  melts  at  29°. 
ei-HYDROXYISOVALERIC  ACID,  (CH3)2CH-CH(OH)  -CO2H,  melts  at  86°. 

METHYLETHYLGLYCOLLIC  ACID,  ,?23>C<?"     ,  melts  at  68°. 

U2ri5  CU2rl 

a-HYDROXYCAPROIC  ACID  (Leucinic  Acid),  CH3-[CH2]3-CH(OH) -CO2H,  melts 
at  73°  and  is  obtained  from  leucine  (see  later). 

a-HYDROXYMYRISTIC  ACID,    CH3- [CH2]n -CH(OH) -CO2H,  melts  at  51°. 

a-HYDROXYPALMITIC  ACID,    CH3- [CH2]13-CH(OH) -C02H,  melts  at  82°. 

a-HYDROXYSTEARIC  ACID,  CH3- [CH2]15-CH(OH) -C02H,  melts  at  84°  to  86°, 
and  is  formed  by  the  action  of  cold  concentrated  sulphuric  acid  on  olcic  acid,  this  method 
being  sometimes  used  practically  to  prepare  solid  fatty  acids  from  liquid  oleic  acid  (see 
section  on  Fats). 

The  Sulphuric  Ether  of  a-Hydroxystearic  Acid,  C18H35O2(OSO3H),  is  used  in  the 
dyeing  of  cotton  with  Turkey-red  (see  below). 

Various  other  ft  -hydro xystearic  and  dihydroxystearic  acids,  with  melting-points  higher 
than  those  of  the  liquid  fatty  acids  which  yield  them,  are  also  known. 

B.     MONOBASIC  UNSATURATED  HYDROXY-ACIDS 

The  o-Hydroxyolefinecarboxylic  Acids  are  prepared  by  hydrolysihg,  with  HC1  in  the 
cold,  the  nitriles  obtained  by  the  addition  of  hydrogen  cyanide  to  olefinic  aldehydes. 
If  the  double  linking  (A)  is  in  the  /By-position,  these  hydroxy -acids  are  converted  into 
y-ketocarboxylic  acids  when  boiled  with  dilute  HC1  ;  thus,  a-hydroxypentenoic  acid, 
CH3  •  CH  :  CH  •  CH(OH)  •  CO2H,  yields  levulinic  acid,  CH3  -  CO  •  CH2  -  CH2 .  CO2H. 

Several  /3-Hydroxyolefinecarboxylic  Acids  are  known.  The  most  simple  is 
ft-hydroxyacrylic  or  formylacetic  acid,  CO2H-CH  :  CH-OH,  which,  like  the  others,  readily 
forms  esters  and  halogen  derivatives. 

y-  and  S-Hydroxyolefinecarboxylic  Acids  are  known  mostly  in  the  form  of  lactones 
(see  pp.  295  and  322). 

RICINOLEIC  ACID  (Hydroxyoleic  Acid),  C18H34O3,  or  CH3-  [CH2]5-CH(OH)  CH2- 
CH  :  CH  •  [CH2]7-CO2H,  constitutes,  in  the  form  of  glyceride,  the  greater  proportion  of 
castor  oil,  and,  on  dry  distillation  under  reduced  pressure,  decomposes  into  cenanthal- 
dehyde,  C7H14O,  and  undecylenic  acid,  C11H20O2.  It  solidifies  at  —  6°  and  melts  at 
+  4°.  It  forms  lead  and  barium  salts  soluble  in  ether,  and,  when  fused  with  KOH,  yields 
sebacic  acid,  C8H16(C02H)2,  and  sec.  octyl  alcohol.  It  Torms  a  solid  bromide  and  an  oily 
ozonide  (by  the  addition  of  ozone)  which  decomposes,  giving,  among  other  products,  a 
large  proportion  of  azelaic  acid  (Molinari  and  Caldana,  1909),  the  position  of  the  double 
linking — established  by  Goldsobel  (1894)  by  means  of  ricinostearolic  acid — being  thus 
confirmed.  By  nitrous  acid  it  is  transformed  into  the  isomeric  ricinelaidinic  acid,  melting 
at  63°.  By  decomposing  the  ozonide  of  methyl  ricinoleate,  Haller  and  Brochet  (1910) 


TURKEY-RED    OIL  327 

obtained  fi-hydroxypelargonic  acid,  CH3-  [CH2]5-CH(OH)-C02H,  azelaic  acid  and  the 
corresponding  semi-aldehyde.1 

By  treating  castor  oil  slowly  with  cold,  concentrated  sulphuric  acid,  ricinosulphuric 
acid  is  obtained,  this  being  the  most  important  constituent  of  Turkey-red  oil,  which  is 
used  in  large  quantities  in  the  dyeing  and  printing  of  cotton  textiles  with  alizarin  red 
(Adrianople  red).*  It  is  also  used  for  greasing  wool  to  be  spun  and  for  dressing  textiles. 

The  treatment  of  castor  oil  with  concentrated  sulphuric  acid  yields  ricinoleic  acid 
more  or  less  polymerised  or  condensed  into  anhydrides,  glycerolsulphuric  esters  of  ricinoleic 
acid  and  a  preponderating  proportion  of  ricinosulphuric  acid,  which  is  an  ester  of  sulphuric 
acid  soluble  in  water  :  C^H^Ca-OH  +  H2SO4  =  H20  +  C^HggOa  •  0  •  S03H.  This  acid 


1  Ricinoleic  Acid  was  prepared  pure  by  Krafft  (1888)  by  hydrolysing  castor  oil,  the  fatty  acids  thus  obtained 
being  cooled  at  0°  and  the  solid  acids  separated  by  squeezing  (at  10°).  The  dry  lead  or  barium  salt  was  then 
prepared  and  extracted  with  ether,  which  leaves  undissolved  the  last  traces  of  the  salts  of  the  solid  fatty  acids  ; 
the  salt  of  ricinoleic  acid  is  dissolved  and  gives  the  pure  acid. 

With  concentrated  sulphuric  acid,  the  acid  gives  (Benedikt  and  Ulzer,  1887  ;  Juillard,  1894  and  1895  ;  Chonow- 
sky,  1909,  and  especially  Ad.  Grtin,  1906  and  1909)  ricinoleinsulphonic  acid,  C17H32(O-SO3H)-CO2H  ;  by  hot 
water  this  acid  is  hydrolysed  with  separation  of  sulphuric  acid  and  formation  of  a  condensed  ester  (ritinolein- 
ricinoleic  ester),  CI7H32(OH)-CO-O-Ci7H32-CO2H,  the  condensation  taking  place  between  the  carboxyl  group  of  one 
molecule  and  the  hydroxyl  of  another  ;  only  one  acetyl  group  is  introduced  into  the  molecule  of  this  compound  by 
the  action  of  acetic  anhydride.  Various  isomeric  condensed  anhydrides  of  dihydroxystearic  acids  are  also  easily 
prepared  :  these  are  solid  and  have  the  constitution  C17H33(OH)2.CO.O.C|,H33(OH).CO2H  (4  isomerides)  and 
can  be  converted  into  the  corresponding  dihydroxygtearic  acids.  One  of  the  latter  melts  at  90°  and  is  optically 
active  ([a]D  =  +  6-45°),  two  melt  at  69-5°  and  108°  respectively  and  are  inactive,  while  the  fourth  melts  at  126° 
and  is  active  ;  the  positions  of  the  two  hydroxyl  groups  seem  to  be  9  and  12,  or  10  and  12  (for  those  with  the 
higher  melting-points). 

The  action  of  sulphuric  acid  on  nlive  oil  partly  decomposes  the  triolein  into  glycerol  and  oleic  acid  and  partly 
transforms  it  only  into  diolein.  To  some  extent  the  double  linking  of  oleic  acid  fixes  H2O  and  forms  hydroxy- 
stearic  acid,  which  is  partly  converted  into  the  sulphuric  ester  of  1  :  \Q-dihydroxystearic  acid.  Besides  free  ricinoleic 
acid,  undccomposed  glycerides  and  glycerol,  Turkey-red  oil  contains  (according  to  Juillard),  the  sulphuric  ester 
of  ricinoleic  acid,  dihydroxystearic  acid  and  the  two  corresponding  mono-  and  di-sulphuric  esters,  as  well  as 
diricinoleic  acid  and  other  polymerides  (up  to  pentaricinoleic  acid). 

The  phenomenon  of  polymerisation  is,  indeed,  of  great  importance  as  regards  the  effects  produced  in  practice 
by  the  sulphoricinate. 

1  Turkey-Red  Oil  (or  sulphoricinate)  is  prepared  by  treating  castor  oil  —  in  an  open,  double-bottomed,  iron 
vessel  furnished  with  a  stirrer  —  with  20  per  cent,  (in  summer)  or  25  per  cent,  (in  winter)  of  concentrated  sulphuric 
acid  (66°  Bi'-.),  which  is  added  very  slowly  during  5  or  even  8  hours,  so  that  the  temperature  of  the  mass  never 
exceeds  35°  ;  if  these  precautions  are  neglected,  SO2  is  evolved.  When  necessary,  the  temperature  is  moderated 
by  passing  cold  water  through  the  jacket.  The  mixture  is  left  for  some  hours  until  a  small  portion  is  found  to 
be  soluble  in  water.  The  mass  is  then  discharged  into  a  wooden  vat  containing  a  quantity  of  sodium  chloride  or 
sulphate  equal  to  that  of  the  oil  treated.  After  mixing,  the  liquid  is  allowed  to  stand  for  some  hours,  the  excess 
of  acid  (10  to  12  per  cent,  is  fixed  in  the  sulphoricinate)  being  next  removed  by  decanting  the  aqueous  portion 
and  washing  the  remainder  in  the  same  manner  and  afterwards  with  two  successive  quantities  of  water  half 
saturated  with  common  salt  ;  sufficient  concentrated  ammonia  or  sodium  hydroxide  solution  is  then  added  to  give 
a  neutral  (or  amphoteric)  reaction.  The  quantity  and  concentration  of  the  alkali  to  be  added  arc  determined 
by  a  preliminary  test  on  a  small  portion,  which  gives  also  the  content  in  fatty  acids  of  the  commercial  ricinatc.  It 
is  usually  a  clear,  yellowish  solution,  which  gives  a  clear  solution  when  diluted  with  2  to  4  vols.  of  water  and  a 
milky  emulsion  when  mixed  with  5  to  6  vols  of  water  or  with  dilute  alkali. 

The  commonest  strengths  are  40,  50,  and  60  per  cent,  of  total  fat  (liberated  from  the  alkali),  which  is  estimated 
by  Herbig's  method  (1906)  ;  10  grins,  of  the  sulphoricinate  are  dissolved  in  50  c.c.  of  hot  water,  25  c.c.  of  dilute 
HC1  being  then  added  and  the  solution  boiled  for  4  or  5  minutes,  during  which  time  it  is  kept  stirredjto  avoid  spurting. 
It  is  next  cooled  (and,  if  desired,  the  volume  of  the  washed  fatty  acids  can  be  measured  in  a  burette)  and  extracted 
in  a  separating  funnel  with  200  c.c.  of  ether,  which  is  washed  with  three  separate  quantities  of  15  to  20  c.c.  of 
water.  The  ether  is  distilled  off  from  a  tared  flask,  the  fat  being  heated  over  a  naked  flame  and  shaken  for  a 
couple  of  minutes,  dried  at  105°  for  half  an  hour  and  weighed.  When  neutral,  not  sulphonated,  fats  are  present, 
they  are  determined  by  treating  30  grms.  of  the  sulphoricinate  with  50  c.c.  of  water,  20  c.c.  of  ammonia,  and 
30  c.c.  of  glycerol,  the  whole  being  extracted  with  ether,  which  is  washed  with  water  and  evaporated  in  a  tared 
dish.  To  ascertain  if  the  sulphoricinate  is  the  ammonium  or  sodium  compound,  tests  are  made  for  these  bases 
in  the  wash-water  separated  in  estimating  the  total  fat  ;  the  ammonia  is  estimated  by  heating  with  excess  of 
alkali  and  collecting  the  ammonia  in  a  standard  solution  of  sulphuric  acid,  while  the  soda  is  determined  by 
evaporating  to  dryness,  calcining  the  residue  and  weighing  as  sodium  sulphate. 

If  the  sulphoricinate  were  not  prepared  from  castor  oil  (inferior  products  are  obtained  from  olive  oil  with  a 
larger  amount  of  sulphuric  acid),  it  will  give  a  turbid  solution  in  alcohol,  while  the  acetyl  number  (see  p.  189)  of  the 
total  fat  is  only  5  to  10  (for  olive  oil),  that  of  true  sulphoricinate  being  usually  140  and  always  above  125.  Further, 
the  iodine  number  of  the  acids  of  true  sulphoricinate  is  never  lower  than  68  to  70,  whilst  with  other  oils  it  is  decidedly 
lower  than  70.  In  the  Zeiss  olcorefractometer  the  fatty  acids  of  pure  sulphoricinate  give  a  reading  of  74. 

The  complete  analysis  of  a  good  sulphoricinate  gave  58  per  cent,  of  total  fat  (composed  of  47  per  cent,  of 
insoluble  fatty  acids,  1-5  per  cent,  of  neutral  fats  and  9-5  per  cent,  of  fatty  sulpho-acids  soluble  in  water),  1-8  per 
cent,  of  ammonia,  and  4-6  per  cent,  of  sulphuric  acid.  In  true  sulphoricinates,  however,  the  ratio  of  sulphuric  to 
sulphoricinic  acid  should  not  be  4-6  :  9-5,  but  rather  4-6  :  22,  and  the  sulpliuric  acid  as  sodium  or  ammonium  sulphate 
should  not  exceed  0-2  to  0-3  per  cent.  The  soluble  sulpho-acids  are  estimated  by  treating  10  grms.  of  the  total 
fatty  acids  with  (not  more  than)  10  c.c.  of  ether  and  30  c.c.  of  saturated  sodium  chloride  solution  free  from  sul- 
phates ;  the  mixture  is  shaken  and  filtered  through  a  moist  filter,  the  sulpho-acids  in  the  filtrate  being  precipitated 
with  barium  chloride. 

The  price  of  Turkey-red  oil  is  based  on  its  content  of  total  fat  and  is  usually  about  lOrf.  per  unit  of  fat  per 
100  kilos  of  sulphoricinate.  This  content  is  often  determined  in  a  graduated  burette,  by  decomposing  a  given 
quantity  of  the  sulphoricinate  with  sulphuric  acid,  diluting  with  water  and  measuring,  in  the  burette,  the  fat 
which  rises  to  the  surface  after  some  hours. 


328  ORGANIC    CHEMISTRY 

is  separated  from  water  by  addition  of  salt  or  dilute  mineral  acid  in  the  cold  ;  it  is  only 
slightly  soluble  in  ether,  and  its  calcium,  lead,  &c.,  salts  are  insoluble  in  water.  Ricino- 
sulphuric  acid  is  not  decomposed  in  the  hot  by  water  or  dilute  alkali,  but  it  decomposes 
readily  into  sulphuric  and  ricinoleic  acids  when  boiled  with  dilute  hydrochloric  or  sulphuric 
acid.  By  using  an  excess  of  concentrated  sulphuric  acid,  Grim  (1907)  obtained  9  :  12- 
dihydroxystearic  acid.  Ricinosulphuric  acid  or  its  sodium  or  ammonium  salt  is  of  im- 
portance in  Turkey-red  oil,  since,  when  the  latter  is  diluted  with  water,  it  serves  to  keep 
in  a  state  of  solution  the  castor  oil  or  other  unaltered  oil  always  found  in  greater  or  larger 
quantity  in  Turkey -red  oil. 

Treatment  of  olive  oil  or  oleic  acid  with  sulphuric  acid  yields  hydroxystearosulphuric 
acid,  which  is  saturated,  C^gH^C^  (oleic  acid)  +  H2SO4  =  C18H35O2  •  O  •  SO3H ;  so  that 
the  iodine  number  may  be  used  to  distinguish  true  sulphoricinates  from  saturated  ones, 
which  are  unable  to  undergo  those  characteristic  oxidations  necessary  to  dyeing  operations. 
With  an  excess  of  sulphuric  acid,  •hydroxystearosulphuric  acid  takes  up  a  molecule  of 
water,  yielding  sulphuric  acid  and  hydroxystearic  acid  (saturated),  C18H35O2  •  OH. 

C.     POLYVALENT  MONOBASIC  HYDROXY-ACIDS 

These  are  derived  from  polyhydric  alcohols  by  the  oxidation  of  one  primary 
alcoholic  group  to  carboxyl,  the  other  two  or  more  alcoholic  groups  remaining 
unaltered  ;  they  exhibit  behaviour  analogous  to  that  of  lactic  acid.  The 
number  of  the  hydro xyls  is  deduced  from  the  acetyl  number  (see  p.  189). 
These  acids,  which  are  gelatinous  and  crystallise  with  difficulty,  are  some- 
times obtained  by  the  gradual  oxidation  of  saccharine  substances  or  of 
unsaturated  acids. 

GLYCERIC  ACID  (o/3-Dihydroxypropionic  or  Propandioloic  Acid),  OH  CH2-CH 
(OH)  -GO2H,  obtained  by  oxidising  glycerol  with  nitric  acid,  exists  in  optically  active  forms,1 
and  is  soluble  in  alcohol,  water,  or  acetone  (which  does  not  dissolve  glycerol).2  As  has  already 
been  mentioned,  dihydroxystearic  acid,  QgH^O^OH^,  is  formed  by  oxidising  oleic  acid. 

ERYTHRIC  ACID  (Butantrioloic  Acid),  OH-CH2- [CH(OH)]2-CO2H,  is  formed  on 
gentle  oxidation  of  fructose  or  erythritol  and  is  monobasic  and  tetravalent. 

Of  the  pentavalent  monobasic  acids,  four  pentonic  or  pentantetroloic  isomerides, 
C4H5(OH)4-C02H,  are  known,  namely,  arabonic  acid  (by  oxidising  arabinose),  and 
ribonic,  xylonic,  and  lyxonic  acids. 

Saccharinic  or  hexantetroloic  acid,  C5H7(OH)4-CO2H,is  obtained  by  treating  glucose 
or  fructose  with  lime,  while  iso-  and  meta-saccharinic  acids  are  also  known  as  salts,  which 
are  readily  obtained  from  the  lactones. 

The  hexonic  acids  or  hexanpentoloic  acids,  C5H6(OH)5  -CO2H,  are  known  in  some  cases 
only  as  lactones  and  are  obtained  by  reduction  of  the  corresponding  dibasic  acids  (saccharic 
acid,  &c.)  or  by  gentle  oxidation  (with  bromine  water)  of  the  corresponding  sugars  (hexoses), 
to  which  they  are  closely  related  : 

Mannose,  C6H12O6,  yields  mannonic  acid,  C6H12O7. 
Galactose        „  „       galactonic    „  „ 

Glucose  „  „       gluconic       „  „ 

Gulose  ,,  „       gulonic         „  „ 

Idose  ,,  „       idonic          „  „ 

Talose  ,,  ,,      talonic         „  „ 

These  acids  can  be  obtained  synthetically  by  hydrolysing  the  nitriles  (see  pp.  265 
and  268)  of  the  simpler  sugars  (pentoses). 

1  From  the  racemic  form,  the  Isovo-modification  can  be  obtained  by  fermenting  the  ammonium  salt  with 
Penlcillium  glaucum,  and  the  dextro-form  by  the  direct  action  of  Bacillus  ethaceticus. 

1  It  forms  a  calcium  salt,  (C3H5O4)2Ca  +  2H2O,  soluble  in  water,  whilst  the  lead  salt  is  only  slightly  soluble 
in  cold  water.  Among  the  derivatives  of  this  acid  are  serine,  OH  •  CH2  •  CH(NH2)  •  CO2H,  which,  being  an  amino- 
derivative,  has  a  neutral  reaction  and  forms  salts  with  both  acids  and  bases ;  it  is  obtained  by  boiling  silk-gum 
with  dilute  sulphuric  acid  and  is  soluble  in  water  but  insoluble  in  alcohol  or  ether. 

Among  the  higher  derivatives  are  (1)  ornithine  (aS-diaminoraleric  acid),  NH2-CH2-CII2-CH2-CH(Nn2)-CO2n, 
which  is  formed  on  decomposition  of  arginine,  contained  in  germinating  lupins,  and  (2)  lysine,  or  ae-diamino- 
caproic  acid,  NH2- [CH2]4-CH(NH2)-CO2H,  which  is  obtained  on  decomposing  casein  or  glue  with  hydrochloric 
acid. 


ALDEHYDIC    ACIDS  329 

Further,  the  hcxonic  acids  yield  the  sugars  on  reduction,  or  the  dibasic  acids  on  oxida- 
tion with  nitric  acid. 

These  acids  can  be  separated  one  from  another  by  the  phenylhydrazine  reaction  ; 
all  of  them  have  the  same  constitution,  but  they  differ  in  the  spatial  arrangement  of 
the  groups  composing  the  molecule,  since  they  are  stereoisomerides  containing  various 
asymmetric  carbon  atoms  : 

OH  •  CH2  •  CH(OH)  •  CH(OH)  -  CH(OH) .  CH(OH) .  CO2H, 

and  for  each  of  these  acids,  except  talonic,  the  dextro-  (d),  laevo-  (I),  and  inactive  (i)  forms 
are  known. 

Some  of  these  stereoisomeric  forms  are  transformed  into  others  simply  by  the  action  of 
pyridine  and  a  little  water  (e.g.  rf-mannonic  acid  gives  rf-gluconic  acid  and  vice  versa),  and 
the  inactive  forms  are  resolved  into  their  active  constituents  by  means  of  the  strychnine 
salts  (see  p.  22). 

The  HEPTONIC  ACIDS  are  also  derived  from  the  corresponding  sugars,  the  heptoses 
(see  later),  e.g.  rliamnohexonic  acid,  C6H8(OH)5-C02H,  from  rhamnose,  glucoheptonic  acid, 
C6H7(OH)6.C02H,  &c. 

D.  MONOBASIC  ALDEHYDIC  ACIDS 

(and  Aldehydic  Alcohols  and  Dialdehydes) 

GLYOXYLIC  or  ETHANOLOIC  ACID,    CO2H-CHO  +  H2O,  gives  up  the  molecule 

of  water  with  which  it  is  combined  without  decomposing,  and  may  be  regarded  as  having 
a  structure  similar  to  that  of  chloral  hydrate,  C02H-CH(OH)2  ;  the  salts  also  correspond 
with  this  formula,  although  they  retain  the  aldehydic  character.  It  occurs  widespread 
in  nature  in  sour  fruit  (gooseberries,  &c.),  and  is  obtained  synthetically  by  heating  di- 
bromoacetic  acid,  CO2H-CHBr2,  with  water,  by  reducing  oxalic  acid  electrolytically,  or  by 
oxidising  ethyl  alcohol  with  nitric  acid.  It  crystallises  with  difficulty,  dissolves  in  water 
and  distils  in  steam. 

FORMYLACETIC  ACID  (Semi-aldehyde  of  Malonic  Acid),  CO2H-CH2-CHO,  is 
obtained  as  aoetal  from  the  acetal  of  acrolein.  The  isomeric  /3-hydroxyacrylic  acid 
(hydroxymethyleneacetic  acid),  C02H-CH :  CH-OH,  is  also  known  and  is  obtained  as  ester 
by  a  synthesis  similar  to  that  of  ethyl  acetoacetate  (see  p.  332).  It  condenses  readily 
to  trimesic  acid,  C6H3(C02H)3. 

GLYCURONIC  ACID,  CO2H- [CH(OH)]4-CHO,  is  obtained  by  reducing  saccharic 
acid,  and,  as  lactone,  melts  at  175°. 

GLYCOLLIC  ALDEHYDE  (Ethanolal),  OH  -CH2-CHO,  is  obtained  by  the  action  of 
baryta  water  on  bromoacetaldehyde  in  the  cold.  It  is  known  only  in  aqueous  solution  and 
may  be  regarded  as  the  simplest  member  of  the  sugar  group,  of  which  it  gives  all  the 
reactions  ;  it  reduces  Fehling's  solution,  even  in  the  cold.  When  oxidised  with  bromine 
water  it  gives  glycollic  acid,  whilst  in  presence  of  dilute  alkali  it  condenses,  forming  tetrose. 
If  heated  in  a  vacuum,  it  condenses  to  a  syrup,  which  retains  the  reducing  character.  With 
phenylhydrazine  acetate  it  yields  glyoxal  phenylosazone. 

GLYCERALDEHYDE,  OH-CH2-CH(OH) -CHO,  is  obtained  together  with  dihy- 
droxyacetone  (as  glycerose)  by  oxidising  lead  glycerate  with  bromine,  or  by  hydrolysis 
of  its  acetal.  On  condensation,  it  gives  acrose. 

ALDOL,  CH3-CH(OH)  -CH2-CHO  (see  p.  205),  which  belongs  to  this  group  of  com- 
pounds, forms  a  dense  oil  soluble  in  water. 

GLYOXAL  (Ethandial),  CHO-CHO,  is  the  dialdehyde  of  glycol,  and  hence  combines 
with  2  mols.  of  bisulphite  [C2H2O2(S03HNa)2  +  H2O]  or  hydrocyanic  acid.  It  is  formed, 
together  with  glycollic  acid,  by  gentle  oxidation  of  acetaldehyde  with  nitric  acid.  It  forms 
a  white  mass  which  is  soluble  in  alcohol  or  ether  and  absorbs  water  with  avidity.  Even 
in  the  cold,  alkalis  transform  it  into  glycollic  acid,  OHO- CHO  +  H2O  =  OH-CH2.CO2H. 

CH-NH  .NH-CH 

With  concentrated  ammonia,  it  gives  glycosine,  \\  x^'^v  I    ' 

CH—  W         ^N  — CH 

CH-NH, 

verted  to  a  large  extent  into  glyoxaline  (iminazole),  \\  ^^-' 

CH— W 


330  ORGANIC    CHEMISTRY 

E.  MONOBASIC  KETONIC  ACIDS 
(and  Keto-alcohols,  Diketones  and  Keto-aldehydes) 

Ketonic  acids  show  all  the  general  reactions  of  acids — i.e.  of  the  carboxyl 
group  (p.  266) — and  of  ketones — i.e.  of  the  carbonyl  group,  CO  (p.  204).  Their 
constitution  can  be  deduced  from  the  various  syntheses  and  from  the  known 
constitution  of  the  hydroxy-acids  derived  from  them  on  reduction. 

Interesting  behaviour  is  shown  by  the  esters  of  the  fi-ketonic  acids,  which, 
owing  to  the  mobility  of  a  hydrogen  atom  adjacent  to  the  carbonyl,  reacts 
sometimes  in  the  ketonic  form  and  sometimes  in  the  isomeric  enolic  form, 
which  represents  an  unsaturated,  tertiary  alcohol : 

CH3-CO-CH2-C02C2H5    ^±     CH3-C(OH):CH-C02C2H5. 

Ethyl  acetoacetate  (keto-form)  Ethyl  hydroxycrotonate  (enol-form) 

The  enolic  form  is  stable  only  as  derivatives,  e.g.  the  acetyl-derivatives, 
CH3-C(0-CO-CH3) :  CH-C02C2H5,  these  derivatives  being  the  more  stable, 
the  more  negative  the  residues  introduced  in  the  direction  of  the  carboxyl. 

This  phenomenon  is  tautomerism  or  pseudoisomerism  (see  p.  17). 

If  the  a-carbon  atom,  adjacent  to  the  carbonyl,  has  one  of  its  hydrogen 
atoms  replaced  by  an  alkyl  group,  thus,  CH3-CO-CHR-C02C2H5,  the  pheno- 
menon of  tautomerism  is  still  observed,  but  this  ceases  to  be  the  case  when 
both  these  hydrogen  atoms  are  replaced,  as  in  CH3-CO-CR2-C02C2H5.  The 
mobile  hydrogen  causing  the  tautomerism  is  solely  that  situate  between  two 
carbonyls  (1:3  diketones)  : 

— CO— CH2— CO—     ±i^     ^C(OH):CH-CO— 

so  that  such  behaviour  is  not  shown  by  acetylformic  acid,  CH3-CO-C02H  ; 
diacetyl,  CH3-CO-CO-CH3  ;  acetonylacetone,  CH3-CO-CH2-CH2-CO-CH3  ; 
levulinic  acid,  CH3-CO-CH2-CH2-C02H,  &c. 

The  tautomeric  forms  can  be  distinguished  and  are  stable  in  the  crystalline 
state,  even  near  the  melting-point ;  the  reciprocal  transformation  is  continuous 
and  very  rapid  in  either  the  fused  or  dissolved  state,  the  two  forms  finally 
attaining  proportions  varying  with  the  conditions  (especially  temperature 
and  nature  of  solvent).  If  separation  of  the  two  forms  by  means  of  a  reagent 
is  attempted,  the  equilibrium  is  displaced  and  the  second  tautomeric  form 
is  transformed  into  the  one  which  has  reacted,  so  that  the  mixture  behaves 
as  a  single  substance,  unless  two  reagents  are  used  which  act  with  equal 
velocities  on  the  two  forms  giving  different,  separable  compounds  ;  syntheses 
with  ethyl  chlorocarbonate  appear  to  correspond  with  these  conditions,  which 
are,  however,  not  easy  to  obtain. 

When  separated,  the  two  forms  can  be  readily  distinguished,  since  the 
enol  gives  an  intense  coloration  with  ferric  chloride,  with  which  the  ketone 
does  not  react.  After  some  days,  however,  the  coloration  yielded  by  the  former 
becomes  paler,  while  a  colour  also  appears  in  the  mixture  of  ketone  and  ferric 
chloride,  a  condition  of  equilibrium  between  the  two  forms  being  slowly  arrived 
at  in  each  case.  Sometimes  the  enolic  form  remains  unchanged  fora  long  time 
in  chloroform  solution,  although  when  dissolved  in  alcohol  it  is  transformed 
more  or  less  completely  into  the  ketonic  form  in  the  course  of  a  few  days. 

The  enolic  form — which  is  soluble  in  alkali,  whereas  the  ketone  is  insoluble 
— gives  (like  all  compounds  containing  a  double  bond)  a  greater  dispersion  and 
refraction  of  light,  and  also  a  greater  electromagnetic  rotation  of  the  plane  of 
polarisation,1  than  the  corresponding  isomerides  without  double  bonds. 

1  Polarised  light  passes  unchanged  through  a  tube  containing  an  inactive  liquid,  but  if  the  tube  is  surrounded 
by  a  wire  through  which  an  electric  current  passes,  the  plane  of  polarisation  is  deviated,  and,  under  equal  condi- 
tions of  temperature  and  current,  the  deviation  is  greater  for  a  compound  with  a  double  bond  than  for  the  isomericle 
without  such  a  bond. 


KETONIC    ACIDS  331 

METHODS  OF  PREPARATION.  Ketonic  acids  are  formed  by  gentle 
oxidation  of  secondary  hydro  xy-acids  ;  thus,  lactic  acid  gives  pyruvic  acid, 
CH3-CH(OH)-C02H  +  O  =  H2O  +  CH3-CO-C02H. 

The  a-ketonic  acids  are  usually  obtained  by  hydrolysing  the  nitriles,  this 
reaction  indicating  the  constitution  : 

CH3-CO-CN  +  2H2O  =  NH3  +  CH3-CO-C02H. 

Acetyl  cyanide  Pyruvic  acid 

/3-Ketonic  acids  are  obtained  as  esters  by  the  action  of  sodium  or  sodium 
ethoxide  on  ethyl  acetate  or  its  homologues  (see  the  Ethyl  Malonate  Synthesis, 
p.  309),  thus  : 

/ONa 
CH3-C02C2H5  +  C2H5-ONa  =  CH3-C^OC2H5 

Ethyl  acetate  Sodium  ethoxide  **"*l**i 


CH3-C0C2H5  +  CH3-C02C2H5  = 
XOC2H5 

2C2H5-OH  +  CH3-C(ONa)  :  CH-C02C2H5. 

Ethyl  sodioacetoacetate 

Acetic  acid  then  readily  expels  the  sodium  and  liberates  ethyl  acetoacetate, 
which  has  not  the  enolic  but  the  ketonic  constitution,  CH3-CO-CH2-C02C2H5. 
The  total  reaction  is  hence  as  follows  : 

CH3-C02C2H5  +  CH3-C02C2H5  =  C2H5-OH  +  CH3-CO-CH2-C02C2H5. 

Similarly  diketones  are  obtained  by  the  interaction  of  ethyl  acetate  and 
simple  ketones  in  presence  of  sodium  ethoxide  : 

CH3-C02C2H5  +  CH3-CO-CH3  =  C2H5-OH  +  CH3-CO-CH2-CO-CH3. 

This  ethyl  acetate  synthesis  has  been  largely  used  to  prepare  compounds 
of  most  varied  characters.  Ethyl  formate  acts  similarly,  giving  hydro  xy- 
methylene  derivatives  [containing  the  group  —  C(OH)  =  ],  which  are  isomeric 
with  the  keto-aldehydes  : 

CH3-CO-CH3  +  H-C02C2H5  =  C2H5-OH  +  OH-CH  :  CH-CO-CH3. 

Acetone  Ethyl  formate  Hydroxymethyleneacetone 

y-Ketonic  acids  are  obtained  by  the  ketonic  decomposition  (see  later)  of 
the  products  of  reaction  of  ethyl  sodioacetoacetate  with  esters  of  a-halogenated 
acids  : 

CH3-CO-CHNa-C02C2H5  +  R  •  CHI  •  C02C2H5  = 

NaI  +  CH3-CO-CH<^™'£°2C2H5    —  >     +  H20    —  -» 

UUjl^HLg 

C02  +  C2H5-OH  +  CH3-CO-CH2-CHR-C02C2H5. 

v        ft 

Properties  of  Ketonic  Acids.  While  the  a-  and  y-ketonic  acids  are  stable, 
the  /3-acids  readily  lose  C02,  giving  the  corresponding  ketones.  Reduction 
of  y-ketonic  acids  yields,  not  hydroxy-acids,  but  y-lactones. 

As  we  saw  was  the  case  with  malonic  acid  (see  p.  309),  the  esters 
of  /3-ketonic  acids  contain  a  hydrogen  atom  readily  replaceable  by  metals, 
e.g.  ethyl  sodioacetoacetate,  CH3-CO-CHNa-C02C2H5. 

Further,  ketonic  acids  readily  form  condensation  products  :  with  aniline 
they  give  quinolines  ;  with  phenylhydrazine,  pyrazoles,  &c. 

PYRUVIC  ACID,  CH3-CO-CO2H,  is  obtained  by  the  dry  distillation  of 
tartaric  or  raccmic  acid,  an  intermediate  product  in  the  reaction  being  possibly 
glyceric  acid  (formed  by  loss  of  CO2),  which  then  loses  water  and  yields 


332  ORGANIC    CHEMISTRY 

pyruvic  acid.  It  is  formed  also  by  oxidising  lactic  acid  with  permanganate 
or  by  hydrolysing  acetyl  cyanide.  Pyruvic  acid  is  a  liquid  with  an  odour 
of  acetic  acid  and  of  meat-extract,  and  is  soluble  in  water,  alcohol,  or  ether. 
It  boils  at  165°  and  solidifies  at  9°.  It  is  a  more  energetic  acid  than  propionic 
owing  to  the  presence  of  a  carbonyl  group  in  close  proximity  to  the  carboxyl. 
Its  constitution  is  indicated  by  the  fact  that  with  nascent  hydrogen  it  gives 
ethylidenelactic  acid.  It  readily  forms  condensation  products  (e.g.  benzenes  ; 
and  with  ammonia,  pyridine  compounds).  When  heated  at  150°  with  dilute 
sulphuric  acid,  it  loses  CO2,  forming  acetaldehyde.  Electrolysis  of  a  con- 
centrated solution  of  potassium  pyruvate  results  in  the  union  of  the  anion 
of  the  acid,  CH3-CO-COO'  with  the  ion  OH',  cyanogen  and  acetic  acid  being 
formed  ;  at  the  same  time  two  anions  combine  with  loss  of  2C02  and  formation 
of  diacetyl,  CH3-CO-CO-CH3.  This  represents  the  general  behaviour  of 
potassium  salts  of  ketonic  acids  on  -hydrolysis. 

Of  the  derivatives,  cysteine  (a-amino-/3-thiolactic  acid),  SH-CH2-CH(NH2)- 
C02H,  and  cystine,  the  corresponding  disulphide,  may  be  mentioned. 

a-Ketobutyric  acid,  CH3-CH2-CO-C02H,  has  no  special  importance. 

ACETOACETIC  ACID  (/3-ketobutyric  acid),  CH3-CO-CH2-CO2H,  is 
obtained  in  the  free  state  by  cautious  hydrolysis  of  its  ester,  and  forms  an 
extremely  acid  liquid  soluble  in  water,  in  which  it  gives  a  red  coloration 
with  ferric  chloride  ;  when  heated,  it  readily  loses  C02  with  production  of 
acetone. 

ETHYL  ACETO ACETATE,  CH3-CO-CH2-C02C2H5,  is  of  far  greater 
importance  than  the  free  acid,  owing  to  the  very  varied  syntheses  in  which 
it  finds  application.  This  ester  is  obtained  in  the  form  of  its  crystalline 
sodium  derivative  by  the  action  of  sodium  and  alcohol  (sodium  ethoxide) 
on  ethyl  acetate  (see  above). 

Ethyl  acetoacetate  (freed  from  sodium  by  means  of  acetic  acid)  is  a  liquid 
having  a  pleasant,  fruity  odour,  and  dissolves  readily  in  alcohol  or  ether  and 
slightly  in  water,  in  which  it  gives  a  red  coloration  with  ferric  chloride.  It 
has  a  neutral  reaction  and  a  specific  gravity  of  1-030  ;  it  boils  at  181°  and 
is  found  in  diabetic  urine.  When  boiled  with  dilute  alkali  or  dilute  sulphuric 
acid,  it  undergoes  ketonic  decomposition,  forming  C02,  acetone  and  alcohol : 

CH3-CO-CH2-C02C2H5  +  H20  =  C02  +  C2H5-OH  +  CH3-CO-CH3. 

With  concentrated  alcoholic  potassium  hydroxide,  it  undergoes  acid 
decomposition,  producing  2  mols.  of  acetic  acid  : 

CH3-CO-CH2-C02C2H5  +  2H20  =  C2H5-OH  +  2CH3-C02H. 

Its  great  reactivity  is  due  to  the  readiness  with  which  one  of  the  hydrogen 
atoms  is  replaceable  by  metals  (Ba,  Al,  Zn,  Ag,  Cu,  &c.,  in  ammoniacal  solu- 
tion), especially  by  sodium.  Ethyl  sodioacetoacetate,  CH3 •  CO  •  CHNa  •  C02C2H5, 
is  a  white  solid  soluble  in  water,  while  ethyl  acetoacetate  is  soluble  in  alkali, 
from  which  it  is  reprecipitated  by  acids.  The  sodium  is  readily  replaced  by 
different  alkyl  groups  by  the  action  of  the  corresponding  alkyl  iodides  (see 
the  analogous  syntheses  with  Ethyl  Malonate,  p.  309).  Since  the  compounds 
thus  obtained  can  be  subjected  to  either  acid  or  ketonic  decomposition,  it  will 
readily  be  seen  how  very  varied  acids  and  ketones  can  be  obtained  by  means 
of  ethyl  acetoacetate.  For  instance,  the  action  of  normal  octyl  iodide  on 
ethyl  sodioacetoacetate  yields  methyl  nonyl  Jcetone,  a  constituent  of  oil  of  rue  : 

CH-3CO-CHNa-C02C2H5  +  I-CH2-  [CH2]G-CH3  = 
Nal  +  CH-C 


KETO-ALCOHOLS    AND    DIKETONES       333 

this  compound,  by  ketonic  decomposition,  giving  methyl  nonyl  ketone,  which 
must  hence  have  the  normal  structure  CH3-CO-CH2-  [CH2]7-CH3. 

Further,  by  eliminating  the  sodium  from  ethyl  sodioacetoacetate  by  means 
of  iodine,  the  two  residues  combine,  forming  ethyl  diacetylsuccinate : 

2CH3  •  CO  •  CHNa  •  C02C2H5  +  Ia  =  2NaI  +  CH3  •  CO  •  CH  •  CO2C2H5 

CH3-CO-CH-C02C2H5 

and  this  ester,  on  ketonic  decomposition  (boiling  with  20  per  cent,  potassium 
carbonate  solution),  reacts  with  2H20  and  gives  2C02,  2C2H5-  OH  and  acetonyl- 
acetone,  CH3-CO-CH2-CH2-CO-CH3,  which  has  a  normal  carbon-atom  chain 

4321 

and  is  a  1  :  4  diketone. 

Ethyl  acetoacetate  also  combines  with  formaldehyde  (in  presence  of 
diethylamine),  with  acetone  and  with  ammonia  ;  with  aniline  it  gives  di- 
phenylcarbamide.  With  one  or  two  mols.  of  sulphuryl  chloride  it  gives  ethyl 
chloracetoacetate  (b.pt.  194°,  sp.  gr.  1-19  at  14°)  or  ethyl  dichloracetoacetate, 
CH3-CO-CC12-C02C2H5,  which  boils  at  206°  and  has  the  sp.  gr.  1-293  at  16°. 

LEVULINIC  ACID,  CH3-CO-CH2-CH2-C02H,  is  obtained  synthetically  by  the  acid 
decomposition  of  the  product  of  reaction  of  ethyl  acetoacetate  and  ethyl  chloracetate. 
It  can  be  prepared  by  boiling  hexoses,  cane-sugar,  cellulose,  gum,  starch,  &c.,  with  con- 
centrated hydrochloric  acid. 

It  melts  at  33°  and  boils  at  239°  with  slight  decomposition,  or  at  144°  under  12  mm. 
pressure. 

It  is  sometimes  used  in  the  printing  of  textiles. 

KETO-ALCOHOLS 

ACETONEALCOHOL  or  ACETYLCARBINOL  (Propanolone) ,  CH3-CO-CH2-OH, 

is  formed  by  heating  either  grape-sugar  with  fused  potassium  hydroxide  or  a  mono-halo- 
genated  acetone  with  barium  carbonate.  It  is  a  liquid  which  boils  almost  unchanged  at 
147°  and  reduces  Fehling's  solution  even  in  the  cold. 

DIHYDROXY ACETONE,  OH-CH2-CO-CH2-OH,  is  formed  together  with  glycer- 
aldehyde  by  oxidising  glycerol  with  nitric  acid.  It  has  a  sweet  taste  and  may  indeed  be 
regarded  as  a  triose  sugar.  It  crystallises  in  colourless  plates  and  reduces  Fehling's  solution 
in  the  cold. 

BUTAN-2-OL-3-ONE  (Dimethylacetol),  CH3>CO-CH(OH) -CH3,  also  reduces 
Fehling's  solution  and  is  obtained  by  reducing  diacetyl.  It  is  a  liquid  soluble  in  water 
and  boils  at  142°. 

The  higher  homologue,  acetoisopropyl  alcohol,  CH3.CO.CH2.CH(OH).CH3,  b.-pt.  177°, 
is  also  known  and  is  formed  by  the  condensation  (by  means  of  alkali)  of  aldehyde 
with  acetone.  Removal  of  water  from  this  compound  yields  Ethylideneacetone, 
CH3.CO.CH :  CH  •  CH3,  boiling  at  122°. 

DIKETONES 

All  diketones  give  mono-  and  di-oximes,  and  mono-  and  di-hydrazones,  the  latter  (as 
with  the  aldehydes)  bearing  the  name  of  osazones  and  being  usually  yellow.  They  often 
exhibit  tautomerism  and  give  rise  to  various  cyclic  condensation  products. 

DIACETYL  or  a-DIKETOBUTANE  (Butandione),  CH3 -CO  -CO  -CH3,  is  prepared  by 
the  general  method  for  diketones,  namely,  by  treating  methyl  ethyl  ketone,  CH3  •  CO  •  C2H5, 
with  amyl  nitrite  and  a  little  HC1,  the  CH2  group  being  transformed  into  —  C  :  NOH,  giving 
an  isonitrosoketone,  thus  : 

CH3.CO.CH2.CH3  +  N02.C6HU      — >     CHg-CO-C-CHg 

N-OH; 

when  boiled  with  dilute  sulphuric  acid,  this  compound  loses  the  hydroxyiminic  group  (as 
hydroxylamine),  the  diketone  remaining. 


334  ORGANIC.  CHEMISTRY 

It  is  a  yellow  liquid  which  has  a  penetrating  odour,  dissolves  in  water  and  boils  at  88°, 
giving  yellowish  green  vapour  (sp.  gr.  0-973  at  20°).  With  hydrogen  peroxide,  diacetyl 
is  converted  quantitatively  into  2  mol.s.  of  acetic  acid  : 

CH3.CO-CO.CH3  +  H2O2  =  2CH3.C02H. 

ACETYLACETONE,  CH3  •  CO  •  CH2  •  CO  •  CH3.  The  best  general  method  for  preparing 
1  :  3-dikctones  consists  in  treating  an  ester  with  sodium  ethoxide  : 

/ONa 

R.CO2C2H6  +  C2H5.ONa  =  R-C^OC2H5; 

XOC2H6 

this  compound,  when  treated  with  a  ketone,  R'-CO-CH3-,  loses  2  mols.  of  alcohol  and  yields 

/ONa 

R-C^  ,  from  which  the  sodium  is  expelled  by  a  dilute  acid.     This  enolic  form, 

XXH-COR' 
OH 
— C^  ,  readily  passes  into  the.  ketonic  form,    —  CO  —  CH2  — ,  thus  giving  the 

^CH- 
compound  R  •  CO  •  CH2 .  CO  •  R'. 

Another  general  method  for  obtaining  1  :  3-diketones  consists  in  treating  the  sodium 
derivatives  of  acetylene  homologues  with  an  acid  chloride  and  then  acting  on  the  acetylenic 
product  with  sulphuric  acid,  so  that  it  combines  with  water  : 

CH3.[CH2]4-C  :.  Na  +  CH3.CO-C1  =  Nad  +  CH3-  [CH2]4-C  :  C-CO.CH3  ; 

Amylacetylene  Acetyl  chloride 

the  latter  +  H2O  >  CH3.  [CH2]4.CO.CH2.CO.CH3. 

As  in  ethyl  acetoacetate  and  ethyl  malonate,  the  two  hydrogen  atoms  of  the  methylene 
group  between  the  two  carbonyl  groups  are  here  also  replaceable  by  metals,  giving  volatile 
compounds  which  are  soluble  in  chloroform,  benzene,  &c.,  and  differ  from  true  salts,  their 
solutions  exhibiting  very  slight  electrical  conductivity. 

Acetylacetone  has  a  pleasant  odour  and  boils  at  137°.  When  boiled  with  water  it 
yields  acetone  and  acetic  acid. 

ACETONYLACETONE  (y-Diketohexane  or  Hexa-2  :  5-dione),  CH3-CO.CH2.CH2- 
CO'CH3,  is  obtained  by  ketonic  decomposition  of  the  product  of  interaction  of  ethyl  aceto- 
acetate and  ethyl  chloracetate  (see  also  Levulinic  Acid)  ;  it  boils  at  194°  and  has  an 
agreeable  smell. 

KETO-ALDEHYDES  AND  HYDROXYMETHYLENEKETONES 

PYRUVIC  ALDEHYDE  (Methylglyoxal  or  Propanolone),  CH3  -CO  -CHO,  is  a  volatile 
oil  obtained  by  decomposing  its  oxime  (isonitrosoacetone)  with  dilute  acid  (see  Diacetyl). 

ACETOACETALDEHYDE,  CH3.CO-CH2-CHO,  was  formerly  thought  to  have  been 
obtained  in  the  free  state,  but  more  exact  study  has  now  shown  the  compound  in  question 
to  be  the  unsaturated  isomeride,  HYDROXYMETHYLENEACETONE,  CH3-CO-CH  : 
CH-OH,  which  has  an  acid  character  and  is  obtained  by  the  interaction  of  acetone  and 
ethyl  formate  in  presence  of  sodium  ethoxide  (see  Ethyl  Acetoacetate).  It  boils  at  100° 
and  readily  condenses  into  1:3:  5-triacetylbenzene,  C6H3(CO-CH3)3. 


F.  POLYVALENT  DIBASIC  HYDROXY-ACIDS  AND  THEIR 

DERIVATIVES 

TARTRONIC  ACID  (Hydroxymalonic  or  Propanoldioic  Acid), 
C02H-CH(OH)-CO2H,  is  formed  by  the  spontaneous  decomposition  of  nitro- 
tartaric  acid  and  is  obtained  synthetically  by  oxidising  glycerol  with  potassium 
permanganate,  by  eliminating  bromine  from  bromomalonic  acid  by  the  action 
of  moist  silver  oxide,  or  by  reducing  Mesoxalic  Acid,  CO(C02H)2.  It  crystal- 
lises with  2H2O  and  melts  at  184°,  losing  C02  and  forming  polyglycollides. 
It  is  soluble  in  water,  alcohol,  or  ether. 


TARTARICACIDS  335 

MALIC  ACID  (Hydroxysuccinic  or  Butanoldioic  Acid),  CO2H-CH(OH)- 
CH2-CO2H,  occurs  in  abundance  in  unripe  fruits  (apples,  grapes,  quinces, 
and  sorb-apples,  from  which  it  is  extracted).  Its  crystals  melt  at  100°  and 
it  dissolves  in  water  or  alcohol  and,  to  a  slight  extent,  in  ether.  When 
subjected  to  dry  distillation,  it  gives  fumaric  acid  and  maleic  anhydride. 
Synthetically  it  is  obtained  from  maleic  or  fumaric  acid  or  asparagine, 
and  also  by  the  action  of  moist  silver  oxide  on  bromosuccinic  acid,  and  by 
the  reduction  of  tartaric  acid  by  means  of  hydriodic  acid. 

As  it  contains  an  asymmetric  carbon  atom,  malic  acid  forms  three  optically 
different  stereoisomerides,  all  of  which  are  known.  Natural  malic  acid  is  Isevo- 
rotatory,  that  derived  from  (^-tartaric  acid  dextro-rotatory,  and  that  obtained 
by  other  syntheses  inactive  but  resolvable  into  active  components  by  fractional 
crystallisation  of  the  cinchonine  salt. 

It  gives  an  acid  calcium  salt  readily  soluble,  and  a  normal  salt  slightly 
soluble  in  water.  The  presence  of  the  alcoholic  group  is  proved  by  the  forma- 
tion of  acetylmalic  acid  (see  p.  189). 

For  the  amido-derivatives,  asparagine,  &c.,  see  later. 

Of  the  higher  homologues  of  malic  acid,  the  following  are  known  :  Four 
isomeric  acids,  C3H5(OH)(C02H)2  (a-  and  fi-hydroxyglutaric  acids,  itamalic 
and  citramalic  acids)  ;  diaterebinic  acid,  C5H9(OH)(C02H)2,  which  readily 
forms  a  lactone,  and  terebinic  acid~C7H1004. 

TARTARIC  ACIDS,  CO2H-CH(OH)-CH(OH)-C02H 

These  are  dibasic  and  tetravalent,  as  they  contain  two  secondary  alcoholic 
groups.  The  presence  of  two  asymmetric  carbon  atoms  leads  to  the  existence 
of  four  stereoisomerides,  which  have  already  been  considered  on  p.  20 : 
(1)  ordinary  or  d-tartaric  acid  ;  (2)  Z-tartaric  acid  ;  (3)  racemic  or  para-  or 
di-tartaric  acid  ;  (4)  i-  or  meso-  or  anti-tartaric  acid. 

They  are  obtained  synthetically  from  dibromosuccinic  acid, 
C02H-CHBr-CHBr-C02H,  and  moist  silver  oxide,  from  glyoxal  cyano- 
hydrin,  from  glyoxylic  acid  by  reduction,  from  mannitol  by  oxidation  with 
nitric,  acid  and  from  fumaric  or  maleic  acid  by  oxidation. 

(1)  d-TARTARIC  ACID.  This  is  the  ordinary  tartaric  acid,  which  occurs 
abundantly  as  such,  and  as  monopotassium  tartrate  (tartar)  in  many  fruits 
— especially  in  the  grape,  and  hence  in  wine,  from  which  it  is  extracted  in  a 
manner  to  be  described. 

Dextro-rotatory  tartaric  acid  forms  hemimorphic,  monoclinic  prisms  with 
a  decided  and  pleasant  acid  taste.  It  is  readily  soluble  in  water  or  alcohol 
and  almost  insoluble  in  ether.  One  hundred  parts  of  water  dissolve  114  parts 
of  the  acid  at  0°,  125-7  at  10°,  139-4  at  20°,  156-2  at  30°,  176  at  40°,  195  at 
50°,  217-5  at  60°,  243-6  at  70°,  273-3  at  80°,  306-5  at  90°,  and  343-3  at  100°. 
The  acid  melts  at  170°,  giving  rise  to  various  anhydrides  and  to  pyruvic  and 
pyrotartaric  acids  ;  ultimately  it  carbonises  with  an  odour  of  burnt  bread 
or,  if  the  temperature  is  raised  considerably,  of  burnt  sugar. 

Energetic  oxidising  agents  convert  it  into  tartronic  acid  or  dihydroxy- 
tartaric  acid  and  finally  into  formic  acid,  carbon  dioxide,  &c.  In  the  hot, 
it  reduces  ammoniacal  silver  solutions  (see  p.  346  for  a  sensitive  reaction  for 
tartaric  acid).  Certain  bacteria  transform  it  into  succinic  acid.  When 
burned,  tartaric  acid  and  tartrates  emit  an  odour  of  burnt  bread,  thus  differing 
from  citric  acid  and  citrates,  which  give  a  pungent  odour. 

Owing  to  the  presence  of  alcoholic  groups,  tartaric  acid,  like  glycerol, 
hinders  the  precipitation  by  alkali  of  many  metallic  oxides,  e.g.  of  cupric 
oxide  in  Fehling's  solution  (containing  caustic  soda,  copper  sulphate,  and 
sodium  potassium  tartrate  ;  see  Sugar  Analysis),  the  intensely  blue,  soluble 


336  ORGANIC    CHEMISTRY 

C02Na-CH-(X 
compound,  /Cu,   being  formed  ;    this   compound  is   not  pre- 

COaK  •  CH-Cr 
cipitable  by  alkalis,  since  the  copper  no  longer  functions  as    cation,  but    is 

— 0-CO-CH-Ov 
contained  in  the  anion,  yCu,  which  migrates  to  the  positive 

— o-co-CH-cr 

pole  or  anode  when  the  salt  is  electrolysed. 

Tartaric  acid  is  used  in  dyeing,  in  the  wine  industry,  in  the  preparation 
of  aerated  beverages  (lemonade),  in  medicine,  &c. 

The  following  salts  of  tartaric  acid  may  be  mentioned,  acid  potassium 
tartrate  being  considered  more  in  detail  later. 

ACID    POTASSIUM    TARTRATE  (Cream  of  Tartar),   C02H-CH(OH).CH(OH). 

CO2K,  is  slightly  soluble  in  water  or  in  dilute  alcohol,  and  has  a  pleasant  acid  taste.     For 
its  commercial  preparation,  see  Tartar  Industry. 

NORMAL  POTASSIUM  TARTRATE,  C4H406K2  +  *H2O,  is  readily  soluble  in 
water  and  separates  from  highly  concentrated  solutions  in  monoclinic  prisms. 

SODIUM  POTASSIUM  TARTRATE  (Rochelle  Salt),  C4H4O6NaK  +  4H20,  is  pre- 
pared by  saturating  cream  of  tartar  solution  with  sodium  carbonate.  Copper  and  iron, 
present  as  impurities,  are  removed  by  means  of  hydrogen  sulphide,  the  solution  being  then 
heated  with  good  animal  charcoal,  filtered,  concentrated  and  allowed  to  crystallise  ;  the 
Rochelle  salt  separates  in  thick  columns  readily  soluble  in  water  and  slightly  so  in  alcohol. 
It  is  used  to  reduce  silver  salts  in  the  silvering  of  mirrors  and  also  for  medicinal  purposes 
and  to  prepare  Fehling's  solution.  It  costs  about  £7  per  quintal. 

CALCIUM  TARTRATE,  C4H4O6Ca  +  4H2O,  is  insoluble  in  water  but  soluble  in  cold 
sodium  hydroxide  solution,  from  which  it  separates  on  heating  as  a  jelly,  which  redisf-olves 
on  cooling.  It  dissolves  in  acetic  acid,  thus  differing  from  calcium  oxalate. 

TARTAR  EMETIC  (or  Potassium  Antimony  1  Tartrate),  C4H4O6(SbO)K  +  AH2O,  is 
prepared  by  precipitating  SbOCl  from  a  solution  of  SbCl3  by  means  of, water,  boiling  the 
precipitate  with  soda  solution  and  dissolving  the  Sb2O3  thus  formed  in  a  solution  of  4  or  5 
times  its  weight  of  potassium  hydrogen  tartrate  in  50  parts  of  water.  After  nitration  and 
concentration  the  solution  deposits,  on  cooling,  efflorescent,  trimetric  pyramids,  which  are 
soluble  in  water  (1  :  13  at  20°,  1  :  6  at  50°)  but  insoluble  in  alcohol.  It  is  poisonous  and 
is  used  in  medicine  as  an  emetic  and  in  dyeing  cotton  as  a  mordant  for  basic  dyes  (price 
about  £9  10s.  per  quintal).  Germany  imported  2019  quintals  in  1908  and  3914  in  1909, 
the  respective  exports  being  10,303  and  10,899  quintals  in  the  two  years. 

(2)  Z-TARTARIC  ACID  differs  from  the  d-acid  only  in  the  opposite  sign  of  its  rotation 
and  in  the  opposed  hemihedry  of  its  crystals.     Mixing  of  the  concentrated  aqueous  solu- 
tions of  the  two  acids  results  in  development  of  heat  and  the  formation  of  inactive  tartaric 
acid. 

(3)  RACEMIC  ACID  (ParatartaricAcid),(C4H606)2  +  2H2O,  represents  a  mixture  of 
dextro-  and  laevo -tartaric  acids  in  equal  proportions,  and  is  hence  optically  inactive  (see 
p.  20).     When  heated  alone  or,  better,,  in  presence  of  concentrated  caustic  soda  solution, 
either  the  rf-acid  or  the  meso-acid  (see  below)  is  transformed  into  racemic  acid.     The  latter 
is  obtained  from  the  mother -liquors  of  ordinary  d-tartaric  acid.     The  molecular  weight, 
determined  cryoscopically  or  from  the  vapour  densities  of  the  esters,  corresponds  with 
the  simple  molecule,  C4H606.     It  forms  triclinic  crystals  which  effloresce    in    the   air, 
and  is  less  soluble  than  the  active  acids.     From   sodium  ammonium  racemate    crystals 
(C4H406)2Na2(NH4)2  +  2H2O,    Pasteur    separated    those    showing    dextro-    from    those 
showing  laevo  -hemihedry,  thus  resolving  racemic  acid  into  its  optically  active  constituents. 
Only  in  the  crystalline  state  is  the  molecule  of  racemio  acid  regarded  as  double  that  of 
tartaric  acid,  whilst  in  dilute  aqueous  solution  it  is  assumed  to  be  decomposed  completely 
into  the  two  optical  antipodes. 

(4)  MESOTARTARIC  ACID,  C4H606  +  H2O,  is  optically  inactive  and  is  not  merely  . 
a  mixture  of  the  active  compounds.     It  is  obtained  by  prolonged  boiling  of  d-tartaric  acid 
with  excess  of  caustic  soda.     Its  potassium  salt  is  more  soluble  in  water  than  those  of  the 
other  tartaric  acids, 


TARTAR   INDUSTRY  337 

THE  TARTAR  INDUSTRY 

MANUFACTURE  OF  POTASSIUM  BITARTRATE  (Cream  of  Tartar  or  Potassium 
Hydrogen  Tartrate).  Although  the  crude  prime  material  of  this  industry  is  very  abundant 
in  Italy  in  wine  residues,  it  is  only  within  the  last  few  years  that  the  working  has  been  placed 
on  a  rational  basis,  the  tartar  being  refined  and  tartaric  acid  prepared.  Although  these 
prime  materials  are  subject  to  an  export  duty  (Is.  9d.  per  quintal),  the  exportation  from 
Italy  amounted  to  about  178,000  quintals,  worth  £480,000,  in  1905,  and  178,500  quintals, 
worth  £416,000,  in  1910.  The  treatment  of  these  products  requires,  besides  special  tech- 
nical ability,  also  considerable  quantities  of  fuel,  and  to  this  is  partly  due  the  difficulties 
of  the  Italian  manufacturers. 

Cream  of  tartar  occurs  abundantly  in  the  green  extremities  of  vine -shoots  and  in  the 
grape,  and  part  of  it  remains  in  the  pressed  vinasse.  The  vinasse  of  southern  grapes  con- 
tains as  much  as  4  per  cent,  of  cream  of  tartar,  and  that  of  other  grapes  from  2  to  2-5 
per  cent.  Vinasse  that  has  not  been  in  contact  with  the  fermenting  must,  and  that  of 
second  wines  have  practically  no  commercial  value.1 

Another  portion  of  the  cream  of  tartar  which  remains  dissolved  in  the  must  gradually 
separates  (lees)  as  fermentation  proceeds — cream  of  tartar  being  less  soluble  in  alcoholic 
liquids  (wine) — and  finally  part  of  it  is  deposited  as  a  crystalline  crust  on  the  walls  of  the 
casks  during  the  winter,  the  solubility  being  less  in  the  cold.  One  litre  of  water  dissolves 
3-2  grms.  of  tartar  at  0°,  4  grms.  at  10°,  5-7  grms.  at  20°,  9  grms.  at  30°,  13  grms.  at  40°, 
18  grms.  at  50°,  24  grms.  at  60°,  32  grms.  at  70°,  45  grms.  at  80°,  57  grms.  at  90°,  69  grms. 
at  100°,  82  grms.  at  110°,  and  94  grms.  at  120°.  In  an  alcoholic  liquid  (with  10  per  cent, 
of  alcohol)  the  solubility  is  reduced  almost  to  one-half  ;  the  solubility  is  also  slightly 
diminished  by  the  tartaric  acid  and  increased  by  the  mineral  acids  of  the  wine. 

These  crude  products  are  of  different  colours  according  as  they  are  obtained  from  white 
wines  (white  tartar)  or  red  wines  (red  tartar),  and  according  to  the  degree  of  purity. 

Fresh  wine  lees  (forming  about  5  per  cent,  of  the  wine)  are  slimy,  of  a  dirty  red 
colour,  and  contain  yeasts,  colouring-matters,  cream  of  tartar  (10  to  25  per  cent.),  and 
calcium  tartrate  (6  to  20  per  cent.).  Italian  wine  lees  are  the  richest  in  potassium  bitartrate 
and  the  poorest  in  calcium  tartrate.  When  removed  from  the  vats,  the  lees  are  placed  to 
drain  in  strong  bags  suspended  by  cords,  the  bags  being  afterwards  tied  up  and  pressed 
slightly  in  a  press.  They  are  then  removed  from  the  bags  and  dried  in  the  air,  being 
turned  from  time  to  time.  When  pressed  and  almost  dry,  they  contain  more  than  double 
as  much  tartar  as  when  in  the  fresh  state  (about  10  per  cent,  of  moisture,  6  to  10  per  cent, 
of  lime,  3  to  5  per  cent,  of  sand,  25  to  40  per  cent,  of  tartaric  acid).  In  some  large  wineries 
the  lees  are  passed  directly  to  the  filter-presses,  cakes  which  are  readily  dried  being  thus 
obtained. 

The  crude  tartar  contains  45  to  70  per  cent,  of  potassium  bitartrate  and  calcium 
tartrate,  and,  if  washed  and  crystallised  once  from  hot  water,  this  content  may  increase  to 
75  to  87  per  cent.,2  the  product  being  then  placed  on  the  market  under  the  name  of  crystals. 

1  One  quintal  of  grapes  yields  30  to  35  kilos  of  vinasse  and  65  to  70  of  must,  so  that  the  annual  Italian  produc- 
tion of  40,000,000  quintals  would  correspond  with  20  to  25  million  quintals  of  vinasse,  containing,  on  the  average 
more  than  3  per  cent,  of  tartar.     The  tartar  is  estimated  by  the  method  of  Carles  :  a  kilo  of  the  vinasse  is  chopped 
and  mixed,  and  100  grms.  weighed  and  boiled  for  10  minutes  with  700  c.c.  of  water  in  a  litre  flask,  the  liquid  being 
subsequently  made  up  to  the  mark  with  distilled  water.     Five  hundred  cubic  centimetres  of  the  filtered  solution  are 
concentrated  to  about  100  c.c.,  70  c.c.  of  saturated  calcium  acetate  solution  being  then  added  to  the  boiling  liquid  ; 
after  mixing,  the  liquid  is  allowed  to  cool  for  12  hours,  the  precipitated  calcium  tartrate  being  then  collected  on 
a  tared  filter,  washed  with  water,  dried  at  60°,  and  weighed.    Multiplication  of  the  result  by  2  and  deduction  of 
5  per  cent,  (to  allow  for  the  volume  occupied  by  the  vinasse  in  the  litre  flask)  gives  the  calcium  tartrate  per  100 
grms.  of  vinasse  ;  further  multiplication  by  0-723  gives  the  corresponding  amount  of  potassium  hydrogen  tartrate. 
Ciapetti  has  rendered  this  method  more  exact  by  transforming  the  calcium  tartrate  (by  potassium  bioxalate  in  the 
hot)  into  potassium  hydrogen  tartrate,  filtering  and  washing  the  residue,  concentrating  the  filtrate  and  adding 
alcohol  to  precipitate  the  potassium  bitartrate  ;  the  latter  is  washed,  redissolved  in  hot  water  and  titrated  with 
decinormal  caustic  soda  solution  (see  below,  Analysis  of  Tartar). 

2  Analysis  of  Tartar.     Tartar  being  a  rather  expensive  substance  (£6  to  £8  per  quintal),  it  is  frequently 
adulterated  with  sand,  gypsum,  Ac.     It  is  always  bought  and  sold  on  its  strength,  the  potassium  bitartrate  or  the 
total  tartaric  acid  (thus  including  both  the  calcium  tartrate  and  the  free  tartaric  acid)  being  determined. 

A  homogeneous  sample  is  finely  ground  and  sieved,  the  residue  being  again  ground. 

A  test  which  is  not  very  exact  but  is  rapid  and  largely  used  is  the  direct  titration  test.  The  coarse  impurities,  sand, 
clay,  sulphur,  woody  matter,  yeasts,  &c.,  arc  estimated  by  boiling  a  known  weight  of  the  crude  tartrate  with  water 
acidified  with  HC1,  and  collecting,  washing,  drying,  and  weighing  the  residue  on  a  tared  filter;  the  residue  is 
sometimes  ashed. 

The  calcium  carbonate  is  determined  by  treating  with  an  acid  in  the  calcimeter  and  measuring  the  carbon 
dioxide  evolved,  and  the  total  lime,  including  that  of  the  tartrate,  by  calcining  a  given  weight  of  the  tartar, 
II  22 


338  ORGANIC    CHEMISTRY 

As  a  rule  60  to  70  per  cent,  of  the  total  tartar  is  extracted  from  the  vinasse  after  the 
alcohol  has  been  distilled  off  with  steam  in  the  manner  indicated  on  p.  143.  The  forms  of 
apparatus  there  shown  give  almost  saturated,  boiling  solutions  of  tartar  (the  remaining 
vinasse  being  centrifuged  or  pressed  to  remove  all  the  tartaric  liquors),  which  are  allowed 
to  cool  in  shallow,  wooden  vessels.  In  these  vessels  are  hung,  after  some  time,  strings 
studded  with  tartar  crystals,  on  which  less  impure  crystals  gradually  form.  The  deposit 
forming  on  the  walls  of-  the  vessels  is  of  a  less  degree  of  purity,  and  that  on  the  bottom 
contains  many  coloured  impurities.  In  5  to  6  days  the  crystallisation  is  complete,  more 
rapid  and  complete  separation  being  attained  in  very  cold  places  or  by  the  use  of  artificial 
cooling.  The  mother -liquors  decanted  from  the  tartar  may  be  utilised  again  for  extraction 
of  vinasse,  but  when  they  become  too  rich  in  impurities  or  mucilaginous  substances,  they 
are  either  used  as  fertilisers,  since  they  contain  potassium  salts,  or,  better,  are  treated 
(Carles,  1910)  at  boiling  temperature  with  60  grms.  of  potassium  ferrocyanide  per  hectolitre, 
the  iron,  alumina,  copper,  &c.,  present  being  thus  removed  ;  the  clarified  liquid  is  treated 
with  lime  to  separate  calcium  tartrate,  the  potassium  salts  being  recoverable  from  the 
filtered  solution  by  the  Alberti  process  (see  later).1  The  dregs  deposited  during  the  extrac- 

dissolving  out  the  potassium  carbonate,  treating-  the  residual  calcium  carbonate  with  excess  of  standard  nitrous 
acid  solution,  and  measuring  the  excess  of  the  acid  by  titration  with  soda  solution.  The  total  lime  is,  however, 
best  estimated  by  dissolving  2  grms.  in  HC1,  neutralising  with  ammonia,  precipitating  with  ammonium  oxalatc, 
and  heating  on  a  water-bath,  the  precipitate  being  subsequently  collected  on  a  filter,  ignited  in  a  platinum  crucible 
and  weighed  as  CaO. 

The  titration  test  of  the  quantity  of  acid  potassium  tartrate  is  carried  out  by  dissolving  a  weighed  amount 
(2  to  3  grms.)  of  the  tartar  in  water  and  titrating  the  boiling  solution  with  N/4-sodium  hydroxide  solution,  using 
very  sensitive  litmus  paper  as  indicator ;  1  c.c.  of  N/4-caustic  soda  solution  corresponds  with  0-047  grm.  of 
potassium  bitartrate.  Multiplication  of  the  amount  of  bitartrate  by  0-798  yields  the  corresponding  amount  of 
tartaric  acid. 

For  international  trade,  the  potassium  bitartrate  is  nowadays  estimated  by  the  filtration  process,  which  largely 
excludes  errors  due  to  the  presence  of  tannin  substances  and  other  impurities  which  also  react  with  litmus  : 

2-35  grms.  of  the  substance  (crude  tartar,  sludge  or  lees)  are  heated  to  boiling  for  5  minutes  with  400  c.c.  of 
water  in  a  500  c.c.  flask  ;  water  is  again  added  and  the  whole  cooled,  made  up  to  500  c.c.,  mixed  and  filtered  through 
a  folded  filter.  Of  the  filtrate  250  c.c.  are  heated  to  boiling  and  titrated  with  N/4-potassium  hydroxide  solution 
(standardised  with  pure  bitartrate),  sensitive  litmus  paper  being  used  as  indicator. 

For  more  exact  determinations,  Rammer's  recrystallisation  method  is  employed  : 

4-7025  grms.  of  substance  (molecular  weight  of  tartar  divided  by  40)  are  heated  to  boiling  with  30  to  40  c.c. 
of  water  in  a  100  c.c.  flask,  the  solution  being  then  neutralised  with  N/4-caustic  soda,  of  which  1  to  2  c.c.  in 
excess  are  added.  The  volume  is  made  up  to  100  c.c.,  and  of  the  filtered  solution,  20  c.c.  are  rendered  decidedly 
acid  with  acetic  acid  and  treated  with  100  c.c.  of  a  mixture  of  alcohol  and  ether,  which  separates  the  potassium 
bitartrate  completely  in  crystals.  These  are  collected  on  a  filter,  washed  with  alcohol  and  ether,  redissolved  in 
boiling  water,  and  titrated  with  N/20-soda  solution. 

Determination  of  the  total  tartaric  acid.  This  gives  the  total  content  of  potassium  bitartarate,  calcium  tartrate, 
and  free  tartaric  acid.  The  Goldenberg-Geromont  hydrochloric  acid  process,  which  was  formulated  as  follows  at 
the  Congress  of  Applied  Chemistry  at  Turin  in  1902,  is  generally  used  : 

Six  grammes  of  the  substance  are  treated  for  8  to  10  minutes  in  a  small  beaker  with  9  c.c.  (for  products  poor  in 
tartar)  or  13  c.c.  (for  richer  products)  of  cold  HC1  (sp.  gr.  1-10),  the  whole  being  then  washed  into  a  100  c.c.  flask, 
made  up  to  volume,  mixed,  and  passed  through  a  dry  pleated  filter.  Fifty  cubic  centimetres  of  the  filtrate  are 
boiled  for  10  to  15  minutes  in  a  tall  250  to  300  c.c.  beaker  with  5  (or  10)  c.c.  of  concentrated  potassium  carbonate 
solution  (66  grms.  in  100  c.c.  of  water),  the  liquid  being  then  washed  into  a  100  c.c.  flask,  cooled,  made  up  to 
volume,  and  filtered  through  a  pleated  filter.  Fifty  cubic  centimetres  of  this  filtrate  are  takdfc  to  dryncss  in  a 
half-litre  dish,  redissolved  in  5  c.c.  of  boiling  water,  and  vigorously  stirred  with  4  to  5  c.c.  of  glacial  acetic  acid ; 
when  the  liquid  is  cold,  100  to  110  c.c.  of  96  per  cent,  alcohol  are  mixed  in,  and  the  potassium  bitartrate  allowed 
to  deposit.  This  is  filtered  under  pressure,  the  dish,  rod,  and  filter  being  repeatedly  washed  with  alcohol.  The 
filter  and  the  bitartrate  are  then  washed  into  the  same  dish  with  boiling  water,  with  which  the  volume  is  made 
up  to  about  300  c.c.  The  liquid  is  then  boiled  and  titrated  with  N/4-alkali,  the  end-point  being  determined  with 
sensitive  litmus  paper. 

To  eliminate  the  error  due  to  the  volume  occupied  by  the  impurities  in  the  original  flask,  0-7  per  cent,  is  deducted 
from  the  total  content  in  the  case  of  low-grade  tartars  (containing  less  than  20  per  cent,  of  bitartrate)  and 
0-7  —  (n  x  0-02)  in  the  case  of  those  containing  20  to  50  per  cent.,  n  being  the  excess  percentage  over  20 ;  beyond 
50  per  cent,  the  correction  becomes  almost  zero. 

1  In  many  places  the  vinasse  is  placed  in  vats  fitted  with  false  bottoms,  steam  being  passed  in  below  while  a 
spray  of  mother-liquor  (red  liquors)  falls  from  above  ;  as  many  hectolitres  of  these  liquors  are  employed  as  there  are 
quintals  of  vinasse.  In  this  manner,  the  first  solution  of  the  tartar  is  obtained  almost  boiling  and  almost  saturated  ; 
it  is  purified  by  percolating  slowly  through  the  vinasse  (the  steam  expels  the  air  and  condenses).  A  second  extrac- 
tion gives  a  less  completely  saturated  solution,  which  is  utilised  for  further  extractions.  Finally,  the  vinasse  is 
not  pressed  but  is  washed  with  water  and  a  little  hydrochloric  acid  to  extract  the  calcium  tartrate,  exhaustion 
being  then  obtained  by  means  of  cold  water  (Tarulli's  method).  The  mother-liquors  from  the  crystallisation,  when 
they  become  too  impure  or,  in  some  cases,  even  after  the  first  crystallisation,  are  treated  with  milk  of  lime  to  pre- 
cipitate all  the  dissolved  tartar,  while  the  liquors  from  the  second  and  third  extractions  are  used  for  fresh  quantities 
of  vinasse. 

To  obtain  purer  solutions  from  the  vinasse,  to  avoid  losses  occasioned  by  the  presence  of  lime  in  the  water,  and 
to  extract  calcium  tartrate  at  the  same  time,  Ciapetti  exhausts  the  vinasse  with  dilute  solutions  of  sulphurous  and 
hydrosulphurous'acid — which  do  not  dissolve  the  colouring-matters  or  the  pectic  or  albuminoid  substances — and 
allows  refined,  white  cream  of  tartar  (!)to  crystallise  out;  the  mother-liquors  are  utilised  further.  This  method 
was  tried  in  various  works,  but  did  not  give  the  results  expected  of  it.  Extraction  on  the  Ciapetti  system  may  also 
be  carried  out  in  the  series  of  stills  used  for  the  distillation  of  the  vinasse  (see  later,  Tartaric  Acid,  Gladysz  Process). 

The  fresh  vinasse  or  the  deposits,  if  not  to  be  worked  up  at  once,  may  be  kept  for  socie  months  if  tartaric 


EXTRACTION    OF    TARTAR  339 

tion  of  the  cream  of  tartar  from  the  vinasse  contain,  in  the  dry  state,  30  to  60  per  cent,  of 
potassium  bitartrate  and  10  to  20  per  cent,  of  calcium  tartate. 

The  refining  of  crude  tartar  from  vinasse,  lees,  &c.,  is  very  difficult  with  the  poorer 
products,  and  in  practice  rich  and  poor  materials  are  often  mixed  so  as  to  give  a  content 
of  60  to  65  per  cent,  when  a  highly  refined  tartar  is  not  required. 

The  crude  tartar  or  other  mixture  should  first  be  ground  and  then  sieved  to  remove 
pieces  of  wood  and  other  impurities.  In  order  to  destroy  certain  impurities  and  protein 
substances  and  hence  hasten  the  filtration  of  the  subsequent  aqueous  solutions,  the  lees 
or  low-quality  tartar  are  heated  in  revolving  iron  cylinders  until  the  temperature  reaches 
160°  to  180°,  the  loss  in  weight  being  8  to  12  per  cent.  It  is  then  introduced  into  a  per- 
forated copper  cylinder  placed  almost  on  the  bottom  of  a  large  wooden  vessel  furnished 
with  copper  or  aluminium  steam  coils.  Care  is  taken  not  to  use  an  excess  of  water,  which 
would  involve  waste  of  fuel,  and  generally  6  to  8  parts  of  water  are  taken  per  1  part  of 
tartar.  A  hood  is  usually  fitted  over  the  vessel  to  carry  off  the  steam  from  the  boiling 
solution.  In  order  to  transform  the  calcium  tartrate  present  into  potassium  bitartrate, 
3  kilos  of  hydrochloric  acid  (20  Be.),  and  3  kilos  of  potassium  sulphate  (previously  dis- 
solved in  20  litres  of  water)  are  added  to  the  water  per  kilo  of  lime  (CaO)  contained  in  the 
calcium  tartrate  (see  method  of  determination  given  above).  The  liquid  is  stirred  occa- 
sionally, boiled  for  an  hour  and  allowed  to  settle  for  about  a  further  hour,  after  which  either 
the  bitartrate  solution  is  decanted  by  means  of  a  tap  a  short  distance  from  the  bottom,  or 
the  whole  mass  is  passed  through  a  filter-press.  The  liquid  is  left  to  cool  in  a  cold  place  in 
ordinary  crystallising  vessels,  or,  better,  in  copper  or  aluminium  basins,  a  somewhat  impure 
and  reddish  brown  tartar  crystallising  out.  Rather  purer  tartar  may  be  obtained  by  col- 
lecting the  crystals  separating  while  the  solution  is  cooling  to  35°  to  40°,  small  crystals 
being  ensured  by  occasional  stirring  ;  the  tepid  mother -liquors  are  then  decanted  and 
crystallised  in  a  cold  place. 

The  brown  mother -liquors  are  used  repeatedly  to  dissolve  fresh  quantities  of  the  crude 
tartar  substances  in  the  hot.  The  brown  crystals  are  detached  from  the  crystallising 
vessels  by  means  of  suitable  spatulas  and  redissolved,  in  a  wooden  vessel  similar  to  that 
previously  used  (with  a  perforated  bottom  for  the  crystals),  in  10  to  12  times  their  weight 
of  water,  which  is  boiled  by  indirect  steam  supplied  through  copper  or  aluminium  coils. 
Decoloration  is  effected  by  adding,  after  half  an  hour's  boiling,  about  1  per  cent,  of  animal 
charcoal  (well  washed  with  hydrochloric  acid  and  thoroughly  rinsed  ;  for  very  impure 
tartar  from  lees  as  much  as  6  to  8  per  cent,  of  animal  charcoal  is  used.)  After  mixing 
and  an  hour's  boiling,  about  1  per  cent,  of  kaolin  free  from  chalk  (washed  with  HC1)  is 
well  mixed  in  in  the  hot  and  the  liquid  either  filter-pressed  or  left  for  2  to  3  hours  so  that 
the  kaolin  may  carry  down  all  the  suspended  charcoal.  In  some  cases  the  solutions  are 
clarified  by  adding  tannin  and  gelatine  (50  grms.  of  the  latter  and  250  of  tannin  dissolved 
separately)  after  the  kaolin  and  before  filtration.  The  pale  yellow,  clear  solution  is  decanted 
(the  first  and  last  portions,  which  are  rather  turbid,  being  kept  separate)  and  crystallised 
in  wooden  crystallising  vessels  or  in  copper  or  aluminium  basins  ;  in  three  or  four  days  the 
crystallisation  is  complete.  The  mother -liquors  are  used  to  dissolve  fresh  brown  crystals, 
since  they  contain  a  little  free  tartaric  acid  which  dissolves  many  of  the  impurities  better 
than  water  does,  and  so  results  in  the  separation  of  purer  crystals.  After  the  removal  of 
the  mother-liquor,  the  crystals  are  washed  repeatedly  with  very  pure  water  (condensed),  a 
trace  of  hydrochloric  acid  being  added  to  the  first  washing  water  if  the  crystals  show  any 
superficial  turbidity.  They  are  finally  dried  on  cloths  in  a  desiccator  at  60°  with  the  help 
of  a  current  of  air. 

In  France  and  also  in  certain  Italian  factories,  Carles  has  applied  a  method  of  extracting 
the  tartar  which  consists  in  treating  100  parts  of  the  crude,  powdered  tartar  with  400  parts 
of  water  at  70°,  containing  sufficient  sodium  carbonate  to  transform  all  the  potassium 
bitartrate  into  the  highly  soluble  sodium  potassium  tartrate  (1  :  1-2).  This  solution  is 
decanted  or  filtered  and  treated  with  more  than  the  amount  of  hydrochloric  or  sulphuric 
acid  necessary  to  neutralise  the  soda  added  ;  this  leads  again  to  the  formation  of  the 
slightly  soluble  potassium  bitartrate,  which  crystallises  out  (96  per  cent,  purity)  on  cooling. 
Vinasse  is  also  extracted  more  readily  by  this  alkaline  method. 

fermentation — which  would  destroy  part  of  the  cream  of  tartar — is  prevented,  either  by  addition  of  0-05  per  cent, 
of  sodium  thiosulphate  or  by  maintaining  the  vinasse  strongly  compressed,  under  chalk  and  sand,  in  wooden  Tats 
(tartaric  fermentation  is  caused  principally  by  Bacillus  saprot/enes  vini).  The  yields  of  tartar  and  alcohol  are 
determined  oil  a  small^uaiitity  (5  kilos)  of  the  vinassc  in  a  small  Savalle  distilling  and  macerating  apparatus. 


340  ORGANIC    CHEMISTRY 

The  recent  process  of  Can toni-Chau terns  and  Degrange  (1910)  refines  the  tartar  almost 
in  the  cold  and  effects  a  marked  economy  of  chemical  products.  This  method  serves  well 
also  for  poor  products  (20  per  cent,  lees),  which  are  heated  as  described  above  and  washed 
first  with  cold  sodium  carbonate  solution  in  a  series  of  vessels,  next  slightly  with  water,  and 
finally,  slowly  and  systematically  with  dilute  hydrochloric  acid. 

In  the  first  case,  sufficient  soda  is  added  to  convert  the  tartar  almost  completely  into 
sodium  potassium  tartrate,  which  can  be  extracted  with  the  minimum  quantity  of  water. 
The  treatment  with  hydrochloric  acid  dissolves  the  remainder  of  the  tartar  and  also  the 
calcium  tartrate.  The  amount  of  the  acid  used  is  chosen  so  that,  when  the  alkaline  and 
acid  solutions  are  united,  it  neutralises  the  soda  first  used.  The  hydrochloric  acid  solution 
is  mixed  previously  with  the  amount  of  oxalic  acid  required  to  precipitate  the  whole  of  the 
lime  present  in  the  crude  tartar  as  calcium  tartrate,  while  sufficient  potassium  chloride  is 
added  to  the  alkali  solution  to  transform  all  the  tartaric  acid,  existing  as  calcium  tartrate, 
into  potassium  bitartrate.  Mixing  of  the  two  solutions  in  the  cold  results  in  the  precipita- 
tion of  almost  all  the  cream  of  tartar  in  a  white,  highly  pure  state,  and  of  the  calcium 
oxalate.  After  filtering,  the  dark  mother -liquors  are  kept  for  subsequent  operations,  while 
the  solid  residue  is  treated  with  the  calculated  (on  the  solubility  of  the  tartar)  quantity 
of  water  at  90°,  a  little  oxalic  acid  being  added  to  render  the  calcium  oxalate  less  soluble. 
The  mass  is  then  filtered  or  centrifuged  (if  necessary,  decolorised  with  a  small  amount  of 
animal  charcoal),  the  clear  liquid,  on  cooling,  depositing  refined  tartar  of  a  purity  of  99  to 
99-5  per  cent.  The  mother -liquor  is  used  to  initiate  the  solution  of  further  quantities  of 
crude  tartar,  &c.  Oxalic  acid  may  be  recovered  from  the  calcium  oxalate. 

A  process  which  allows  of  the  conversion  of  calcium  tartrate  into  potassium  bitartrate 
consists  in  boiling,  say,  100  kilos  of  the  calcium  tartrate  (85  per  cent.)  with  1500  litres  of 
water  and  53-5  kilos  of  potassium  bisulphate  (or  a  mixture  of  35  kilos  of  the  neutral  sulphate 
and  24-6  kilos  of  sulphuric  acid  at  60°  Be.)  for  half  an  hour,  decanting  and  filtering  the 
liquid,  from  which  pure  potassium  bitartrate  (up  to  98  per  cent. )  crystallises  on  cooling. 

This  process  is  a  modification  of  that  of  Martignier  (Fr.  Pat.  Nov.  23,  1889),  who 
transforms  calcium  tartrate  into  normal  potassium  tartrate  by  decomposition  with  normal 
potassium  sulphate  ;  after  filtration  and  concentration  and  addition  of  the  calculated 
amount  of  sulphuric  acid,  the  solution  deposits  potassium  tartrate. 

If  the  cream  of  tartar  crystals  are  not  pure  but  contain  small  proportions  of  calcium 
tartrate,  they  do  not  give  perfectly  clear  solutions  in  water.  When  the  pale  mother -liquors 
from  the  final  refining  are  somewhat  impure,  they  are  used  in  place  of  the  brown  liquor  to 
dissolve  the  crude  material,  the  highly  impure  brown  liquors  being  used  in  the  manufacture 
of  tartaric  acid  or  added  in  small  amounts  to  the  prime  tartaric  materials. 

STATISTICS  AND  USES.  The  exports  of  crude  tartar  substances  (vat  deposits, 
wine  lees,  &c.)  from  Italy  are  as  follow  :  in  1887,  150,000  quintals,  worth  £1,000,000  ; 
in  1896,  147,566,  and  in  1903,  164,000  quintals.  The  importation  of  crude  tartar  and  lees 
amounted  to  1424  quintals  in  1887,  3975  quintals  in  1896,  2356  quintals  in  1902,  and  3356 
quintals  in  1903. 

The  total  Italian  production  of  tartar,  &c.,  in  1905  has  been  estimated  at  £1,600,000, 
but  this  is  probably  in  excess  of  the  truth,  since  the  world's  production  was  valued  at  about 
£2,800,000.  Crude  tartar  and  lees  pay  an  export  duty  from  Italy  of  Is.  9d.  per  quintal, 
no  import  duty  being  levied  ;  refined  tartar  pays  an  import  duty  of  3*.  2d.  Italy  con- 
tains about  200  crude  cream  of  tartar  works,  but  only  very  few  manufacturing  refined 
tartar. 

In  1905  Germany  imported,  for  refining,  26,000  quintals  of  crude  tartar,  worth  £129,600 ; 
26,914  quintals  in  1908,  and  20,263  quintals  in  1909,  the  exports  being  12,250  and  11,535 
quintals  respectively.  In  1890,  more  than  51,000  quintals  were  imported,  and  in  1896 
about  57,000  quintals,  the  corresponding  exportation  being  about  5000  quintals  of  the 
refined  product.  France  produces  annually  61 ,000  quintals  of  refined  cream  of  tartar.  The 
imports  of  tartaric  acid  into  England  were  1850  tons  in  1909  and  2250  tons  (£203,365)  in 
1910,  when  the  exports  were  valued  at  £31,300  ;  in  1911the  imports. amounted  to  £200,300, 
and  the  exports  to  £38,240.  The  imports  of  cream  of  tartar  were  3550  tons  in  1909,  4100 
tons  (£307,000)  in  1910,  and  £301,940  in  1911. 

Crude  cream  of  tartar  is  bought  and  sold  at  ll^d.  to  14|d.  per  unit  of  strength,  and  the 
refined  at  Is.  Id.  or  more. 

Cream  of  tartar  is  largely  used  in  dyeing,  in  the  bichromate  mordanting  of  fast 


MANUFACTURE  OFTARTARIC  ACID    341 

wool  dyes,  &c.,  and  in  the  printing  of  textiles.  Considerable  quantities  are  used  in  the 
United  States  for  preparing  powder  which  is  added  to  dough  to  render  the  bread  light  and 
elastic  ;  this  powder  contains  69  per  cent,  of  tartar  and  31  per  cent,  of  sodium  bicarbonate. 

MANUFACTURE  OF  TARTARIC  ACID.  This  acid  is  prepared  by  decomposing 
its  salts  (cream  of  tartar,  lees,  calcium  tartrate,  &c.),  the  dark  mother-liquors  and  the 
deposits  and  sludges  of  cream  of  tartar  factories  being  most  commonly  employed. 

Attempts  were  at  one  time  made  to  liberate  the  acid  from  its  soluble  salts  by  treating 
these,  in  hot  solutions,  with  hydrofluosilicic  acid,  which  separates  as  insoluble  potassium 
fluosilicate,  the  solution  of  tartaric  acid  remaining  being  filtered,  concentrated  and  crys- 
tallised. The  potassium  fluosilicate  is  treated  with  calcium  carbonate  to  convert  it  into 
insoluble  calcium  fluosilicate,  which  yields  hydrofluosilicic  acid  under  the  action  of  an 
energetic  acid.  Tartaric  acid  has  also  been  prepared  by  treating  solutions  of  its  salts  with 
barium  carbonate  and  then  with  barium  chloride,  the  latter  precipitating  the  neutral 
potassium  tartrate  partly  formed  by  the  former  reagent. 

At  the  present  time,  however,  the  method  most  commonly  used  consists  in  treating 
boiling  cream  of  tartar  solutions  with  milk  of  lime  or  powdered  calcium  carbonate.  In  this 
way  half  of  the  tartar  is  converted  into  insoluble  calcium  tartrate  and  the  other  half  into 
the  soluble  normal  potassium  tartrate,  the  latter  being  then  separated  as  the  insoluble 
calcium  salt  by  addition  of  calcium  sulphate  or  chloride  : 

2C4H506K  +  CaC03  =  H20  +  CO2  +  C4H406Ca  +  C4H406K2  ; 
C4H4O6K2  +  CaSO4  =  K2S04  +  C4H406Ca. 

The  acid  is  liberated  from  calcium  tartrate  by  means  of  sulphuric  acid  : 
C4H406Ca  +  H2SO4  =  CaSO4+  C4H606. 

According  to  the  nature  of  the  materials  employed,  various  procedures  are  adopted. 

Crude  tartar  is  freed  from  coarser  impurities  by  passing  through  a  wide -meshed 
sieve,  heated  if  necessary  (see  above),  ground  to  a  fine  granular  condition  and  placed  in  a 
wooden  vessel,  where  it  is  treated  with  8  to  10  times  its  weight  of  boiling  water.  The  mass 
is  well  mixed  with  a  stirrer  and  heated  to  boiling  by  a  steam  jet,  most  of  the  tartar  then 
dissolving.  A  paste  of  calcium  hydroxide  (sieved)  is  then  added  until  a  small  portion  of  the 
liquid  gives  only  slight  effervescence  with  calcium  carbonate  (as  a  rule,  160  grms.  of  quick- 
lime, made  into  a  10  per  cent,  paste,  are  required  for  each  kilo  of  potassium  tartrate),  the 
mixture  being  then  boiled  for  15  minutes. 

In  this  way  calcium  tartrate  is  precipitated,  while  normal  potassium  tartrate  remains 
in  solution.  The  latter  is  then  precipitated  as  calcium  salt  by  boiling  with  a  slight  excess 
of  gypsum  or  of  calcium  chloride  solution  (300  grms.  of  the  chloride  per  kilo  of  tartrate 
used)  for  about  two  hours  ;  a  little  precipitated  calcium  carbonate  is  finally  added  to 
precipitate  the  neutral  tartrate  as  completely  as  possible.  In  some  cases,  however,  the 
liquid  is  left  slightly  acid  to  prevent  separation  of  iron  and  aluminium  salts.  It  is,  indeed, 
necessary  to  ensure  the  absence  from  the  various  reagents  (lime,  chalk,  gypsum,  &c.) 
of  iron,  aluminium,  and  especially  magnesium,  the  latter  forming  magnesium  tartrate,  which 
is  ultimately  found  as  magnesium  sulphate  in  the  tarfaric  acid  after  the  calcium  tartrate  has 
been  treated  with  sulphuric  acid.  The  boiling  liquid  is  kept  mixed  and  is  afterwards  either 
allowed  to  cool  to  40°  and  decanted  or  passed  immediately  to  the  filter-press  ;  after 
repeated  washings  with  hot  and  cold  water,  the  crude,  dry  tartrate  is  placed  on  the  market 
and  the  filtrate  either  rejected  or  evaporated  to  obtain  the  potassium  chloride  present. 
But  where  the  calcium  tartrate  is  converted  into  tartaric  acid,  it  is  not  necessary  to  filter 
and  dry  it,  the  tartrate,  after  the  first  decantation,  being  mixed  with  various  separate 
amounts  of  water,  which  are  drawn  off  when  the  precipitate  settles.  The  calcium  tartrate 
remaining  can  then  be  treated  in  the  same  vessel  with  sulphuric  acid  as  described  above. 

The  procedure  is  rather  more  complicated  in  the  case  of  wine  lees  (sediments,  sludge, 
&c.),  as  the  tartrate  cannot  be  extracted  merely  by  treatment  with  water  and  filtration, 
owing  to  the  presence  of  considerable  amounts  of  mucilaginous  protein  substances 
(ferments),  which  impede  filtration.  The  moist  lees  (drained  in  bags  and  pressed)  contain 
as  much  as  8  per  cent,  of  cream  of  tartar,  or,  if  dried  in  the  sun,  still  more. 

These  lees  are  nowadays  worked  by  the  Dietrich  and  Schnitzer  process  (1865) :  they  are 
first  powdered  and  mixed  by  means  of  stirrers  and  then  heated  for  5  to  6  hours  in  iron 


842  ORGANIC    CHEMISTRY 

autoclaves  (4  metres  high  and  1-4  wide  for  15  quintals  of  lees)  at  4  to  5  atmos.  pressure, 
direct  steam  being  admitted  by  copper  coils  and  the  air  first  allowed  to  escape.  The  albu- 
minoids are  thus  coagulated  together  with  large  quantities  of  colouring-matters,  and  the 
mass  can  then  be  easily  filtered,  but  before  this,  it  is  discharged  into  a  lead-lined  wooden 
vessel  (holding  10  to  12  cu.  metres)  containing  3  cu.  metres  of  water  and  the  amount  of 
hydrochloric  acid  (20°  to  22°  Be.)  corresponding  with  the  quantity  of  tartar  previously 
determined  (100  kilos  of  potassium  bitartrate  require  60  kilos  of  hydrochloric  acid  at 
20°  Be.,  or  54-5  kilos  at  22°  Be.).  The  mass  is  well  mixed  and  passed  through  the  filter- 
press,  in  which  it  is  washed  with  water.  The  tartaric  acid  is  then  separated  from  the  solu- 
tion as  calcium  tartrate,  as  described  above. 

Lees  may  be  treated  economically  and  well  by  the  process  of  Cantoni,  Chautems,  and 
Degrange  described  above. 

To  utilise  the  potash  salts  of  the  filtrate  from  the  calcium  tartrate,  A.  Albert!  (U.S. 
Pat.  757,295,  1910)  decomposes  the  organic  substances  in  the  hot  with  calcium  chloride, 
filters  and  concentrates  in  a  vacuum. 

The  second  phase  of  the  manufacture  of  tartaric  acid  consists  in  the  decomposition  of 
the  calcium  tartrate  by  means  of  sulphuric  acid  (see  above)  and  in  the  subsequent  crystallisa- 
tion of  the  tartaric  acid. 

The  calcium  salt  in  the  decantation  or  washing  vessels,  or  as  cakes  from  the  filter-presses, 
is  broken  up  and  suspended  in  5  to  6  times  its  weight  of  water  in  lead-lined  wooden  vessels 
furnished  with  stirrers  covered  with  lead  and  with  coils  for  indirect  steam-heating.  After 
the  liquid  paste  has  been  well  stirred,  the  sulphuric  acid,  previously  diluted,  is  added  in 
such  amount  that,  after  an  hour's  stirring  at  60°  to  70°,  there  is  still  a  slight  excess  of 
sulphuric  acid,  detectable  by  the  faint  green  coloration  imparted  to  a  solution  of  methyl 
violet.  Too  great  an  excess  of  sulphuric  acid  produces  blackening  of  the  tartaric  acid 
solution  during  concentration,  whilst  deficiency  of  sulphuric  acid  results  in  the  formation  of 
turbid,  impure  tartaric  acid  crystals  ;  but  when  a  little  free  sulphuric  acid  is  present,  fine 
shining  crystals  are  obtained.  Usually  1  kilo  of  sulphuric  acid  at  66°  Be.  is  employed  per 
3  kilos  of  dry  calcium  tartrate.  The  solution  is  boiled  for  a  couple  of  hours,  left  to  cool, 
and  the  calcium  sulphate  which  forms  separated  by  means  of  a  filter-press,  washed  with 
a  little  tepid  water  (this  being  added  to  the  filtrate),  and  then  with  much  cold  water  (this 
being  used  for  treating  subsequent  quantities  of  calcium  tartrate).  The  tartaric  acid  solu- 
tions were  at  one  time  concentrated  in  shallow,  lead-lined,  wooden  vessels  containing 
leaden  steam-coils.  But  nowadays  concentration  is  carried  out  in  vacuum  pans  which 
are  similar  to  those  described  later  in  dealing  with  the  sugar  industry  and  are  of  lead  and  of 
considerable  thickness. 

The  liquid  is  evaporated  until  it  becomes  almost  syrupy,  and  is  then  discharged  into 
wooden  vessels  containing  stirrers,  which  cool  the  concentrated  solution  rapidly  and  thus 
cause  the  tartaric  acid  to  separate  in  small  crystals.  The  cold  mass  is  quickly  separated 
from  the  mother -liquor  in  a  centrifuge,  the  crystals  being  washed  with  a  fine  spray  of  cold 
water.  The  mother-liquors  are  then  concentrated  until  they  give  crystals,  this  process 
being  carried  out  three  times  ;  they  are  finally  treated  with  milk  of  lime  to  separate  the 
residual  tartaric  acid  as  calcium  tartrate,  which  is  filtered  and  worked  up  with  the  other 
calcium  tartrate.  The  tartaric  acid  crystals  are  dissolved  in  one-half  their  weight  of 
boiling  water  (if  necessary,  the  solution  is  decolorised  with  animal  charcoal  and  filtered) 
and  the  liquid  left  to  crystallise,  the  crystals  thus  obtained  being  centrifugcd  and  dried  on 
sheets  of  lead  in  a  current  of  air  at  30°  ;  the  mother-liquors  are  used  to  dissolve  fresh 
quantities  of  the  small  crystals. 

The  final  yield  is  about  90  to  95  per  cent,  of  the  total  tartaric  acid  in  the  prime  materials 
when  these  are  poor  (e.g.  lees  with  20  to  25  per  cent,  of  tartar)  or  97  to  99  per  cent,  when 
richer  prime  materials  (70  to  80  per  cent,  of  tartar)  are  used. 

A  process  still  little  used  but  worked  successfully  for  many  years  in  the  Montredon 
factory  near  Marseilles  is  that  of  Gladysz  (Ger.  Pat.  £7,352,  October  15,  1885),  which  is 
based  on  the  following  observations:  (1)  When  calcium  tartrate  is  suspended  in  water 
and  saturated  with  sulphur  dioxide,  soluble  calcium  bisulphite  is  formed  and  the  tartaric 
acid  liberated  ;  (2)  when  this  solution  is  heated  to  66°,  the  sulphurous  acid  is  expelled 
and  all  the  tartaric  acid  precipitated  as  pure  crystallised  calcium  tartrate;  (3)  if  in  (1) 
potassium  bitartrate  is  used  instead  of  calcium  tartrate,  potassium  bisulphite  and  tartaric 
acid  are  formed,  and  on  heating  the  liquid  to  80°,  sulphur  dioxide  is  evolved  and  pure 


TARTARIC    ACID    STATISTICS  343 

potassium  bitartrate  separated  in  a  crystalline  state  ;  (4)  potassium  tartrate,  when  treated 
with  calcium  bisulphite,  gives  potassium  bisulphite  and  calcium  bitartrate  ;  the  latter 
separates  at  100°,  when  the  potassium  bisulphite  gives,  with  lime,  calcium  bisulphite  and 
caustic  potash,  which  can  also  be  utilised. 

In  practice  Gladysz  proposed  to  suspend  the  tartar  in  lumps  in  lead-lined  wooden 
vessels,  and  into  these— hermetically  sealed  and  arranged  in  a  series  of  five  or  six — to  pass 
sulphur  dioxide.  The  solutions  (10°  to  12°  Be.)  thus  obtained  are  sent  to  the  concentration 
apparatus,  which  communicates  with  towers  to  condense  the  sulphur  dioxide  (see  vol.  i, 
p.  245).  When  the  latter  is  completely  evolved,  the  liquid  is  kept  at  125°  for  a  short  time 
to  separate  crystalline  calcium  tartrate,  which  is  collected  by  means  of  a  centrifuge,  while 
the  solution  is  concentrated  further  and  allowed  to  cool  in  shallow  lead-lined  wooden 
vessels  to  deposit  the  potassium  tartrate.  As  a  rule,  however,  the  hot  potassium  tartrate 
solution  is  treated  directly  with  calcium  chloride  and  a  little  lime,  so  that  it  yields  insoluble 
calcium  tartrate,  which  is  more  easily  separated.  From  this  calcium  tartrate,  pure 
tartaric  acid  is  then  obtained  in  the  ordinary  way.  Although  theoretically  no  sulphur 
dioxide  should  be  lost  in  this  process,  in  practice  about  15  per  cent,  is  lost  in  winter  and 
20  per  cent,  in  summer. 

The  Gladysz  process,  somewhat  modified  by  Ciapetti,  is  used  in  Italy  in  the  manufacture 
of  tartar  from  vinasse,  lees,  &c.  (see  p.  338). 

USES  AND  STATISTICS  OF  TARTARIC  ACID.  This  acid  is  used  in  considerable 
quantities  to  replace  the  more  expensive  citric  acid  in  the  preparation  of  beverages, 
liquors,  and  aerated  waters,  and  in  wine-making.  Large  quantities  are  consumed  in  the 
mordanting  of  wool  and  silk,  to  reduce  chromium  salts,  &c.,  in  the  printing  of  textiles, 
manufacture  of  dyes,  photography,  medicine,  &c.  Refined  tartaric  acid  pays  an  import 
duty  in  Italy  of  8s.  per  quintal  and  in  the  United  States  and  Spain  of  25  per  cent,  ad 
valorem. 

Italy  possesses  four  tartaric  acid  factories  :  at  Carpi,  Agnano  (Pisa),  Barletta,  and 
Milan.  The  last  two  are  the  more  important,  and  are  able  to  produce  together  as  much  as 
30,000  quintals  per  annum. 

The  world's  production  in  1905  was  about  110,000  quintals,  of  which  Italy  produced 
6700  quintals  ;  England  and  the  United  States,  each  more  than  25,000  ;  Germany,  about 
15,000  ;  France,  about  8000  (13,000  in  1910)  ;  and  Austria -Hungary  about  10,000  quintals. 
Germany  exported  17,000  quintals  of  the  refined  acid  in  1908  and  19,000  in  1909,  in  which 
year  the  importation  was  3240  quintals.  In  1909,  England  imported  18,500  quintals  and 
exported  3500.  Italy  imported  981  quintals,  worth  £10,200,  in  1902  ;  1050  quintals  in 
1905  ;  1658  in  1907  ;  1574  quintals,  worth  £15,216,  in  1909  ;  2976  quintals  (one-third 
from  Austria),  worth  £27,380,  in  1910.  Exports  from  Italy  amounted  to  17,000  quintals 
in  1907  ;  19,300  in  1908  ;  15,050,  worth  £141,480,  in  1909,  and  21,774  quintals,  worth 
£195,966,  in  1910.  In  1907,  four  Russian  factories,  worked  by  a  syndicate,  produced 
6000  quintals  of  tartaric  acid  and  sold  it  at  £20  per  quintal.  In  1911  the  United  States 
imported  12,500  tons  (£575,400)  of  tartar. 

In  1904,  Argentine  imported  950  quintals,  and  in  1909,  4650  quintals.  But  there  is 
now  a  factory  at  Buenos  Ayres  which  can  produce  3500  quintals  per  annum. 

Pure  tartaric  acid,  which  formerly  cost  £14  per  quintal,  is  now  sold  at  £10  to  £10  8s. 

ARTIFICIAL  TARTARIC  ACID.  In  1889  a  process  was  patented  by  Basset,  and  in 
1891  a  similar  but  improved  one  by  Naquet  for  obtaining  tartaric  acid  from  starch  (1  to 
5  of  water)  by  saccharifying  with  an  equal  weight  of  hot  sulphuric  acid  (51°  Be.),  then 
adding  double  this  quantity  of  sulphuric  acid  and  almost  as  much  sodium  nitrate  and 
heating  at  100°.  When  the  reaction  becomes  very  vigorous,  the  temperature  is  moderated 
and  the  heating  continued  at  80°  to  90°  for  2  to  3  days,  the  evaporated  water  being  first 
replaced  and  the  liquid  concentrated  to  a  syrup  when  evolution  of  gas  ceases.  In  this 
manner  all  the  saccharic  acid  is  decomposed  ;  the  sulphuric  and  oxalic  acids  are  then 
neutralised  with  calcium  carbonate  and  the  tartaric  acid  subsequently  worked  up  in  the 
usual  manner  by  way  of  its  calcium  salt. 

One  hundred  kilos  of  starch  should  give  theoretically  140  of  calcium  tartrate  corre- 
sponding with  56  kilos  of  tartaric  acid,  but  in  practice  the  yield  of  the  acid  does  not  exceed 
55  to  60  per  cent,  of  this  theoretical  amount. 

TRIHYDROXYGLUTARIC  ACID,  CO2H- [CH(OH)]3-CO2H,  should  exist  in  four 
stereoisomeric  forms,  of  which  the  dextro-,  Isevo-  and  racemic  (m.pt.  127°)  compounds 


344  ORGANIC    CHEMISTRY 

are  known.  They  are  obtained  by  the  oxidation  of  xylose  or  arabinose,  and,  on  reduction, 
give  glutaric  acid,  their  constitution  being  thus  confirmed. 

SACCHARIC  ACID,  CO2H-  [CH  (OH)  ]4-CO2H,  forms  ten  stereoisomerides,  which  are 
all  known  and  are  closely  related  to  the  sugars.  Saccharic  acid  is  formed  as  a  rule  in  the 
oxidation  of  sucrose,  glucose,  mannitol,  and  starch  (e.g.  with  nitric  acid).  It  is  deliquescent 
and  soluble  in  water,  and  when  heated  or  fused  is  converted  into  saccharone,  which  is  a 
dextro-rotatory  lactone  melting  at  about  150°. 

MUCIC  ACID,  CO2H-  [CH(OH)]4-CO2H,  is  the  stereoisomeride  of  saccharic  acid  which 
is  constantly  inactive.  It  is  obtained  on  oxidising  lactose,  dulcitol,  gum,  &c.,  and  forms 
a  white  powder  very  slightly  soluble  in  water. 

KETONIC  DIBASIC  ACIDS 

Ethers  of  these  acids,  like  those  of  /3-ketonic  acids  (ethyl  acetoacetate,  &c.  ; 
see  p.  332),  show  both  ketonic  and  acid  decompositions,  and  also  a  new  method 
in  which  carbon  monoxide  separates. 

MESOXALIC  ACID  (Dihydroxymalonic  Acid),  CO2H-CO-C02H  +  H2O  or 
C02H-C(OH)2-C02H,  shows  ketonic  behaviour  in  agreement  with  the  first  formula,  but 
the  molecule  of  water  cannot  be  separated  from  the  deliquescent  prisms  even  at  100°,  and, 
further,  derivatives  (esters,  &c.),  are  known  which  correspond  better  with  the  second 
formula,  whilst  the  latter  also  explains  well  why  mesoxalic  acid,  when  heated  with  water, 
loses  C02  and  gives  glyoxylic  acid,  CO2H-CH(OH)2.  The  structure  of  the  acid  likewise 
follows  from  its  formation  by  the  action  of  barium  hydroxide  on  ethyl  dibromomalonate  : 

CBr2(C02C2H6)2  +  Ba(OH)2  =  BaBr2  +  C(OH)2(C02C2H5)2. 

Its  ketonic  constitution  is  confirmed  also  by  the  fact  that  it  gives  tartronic  acid, 
CO2H-CH(OH).C02H,  on  reduction. 

OXALACETIC  ACID  (Butanonedioic  Acid),  CO2H-CH2.CO-CO2H,is  not  known  in 
the  free  state,  but  is  formed  as  ether  by  condensation  of  ethyl  oxalate  and  ethyl  acetate  in 
presence  of  sodium  ethoxide  (see  Ethyl  Acetoacetate).  It  also  splits  up  in  two  ways 
according  as  it  is  treated  with  dilute  sulphuric  acid  (giving  pyruvic  acid,  CO2,  and  alcohol) 
or  with  alkali  (giving  oxalic  and  acetic  acids).  Being  a  ketone,  it  forms  an  oxime. 

The  alcoholic  solution  is  coloured  dark  red  by  ferric  chloride  and  hence  corresponds 
with  the  enolic  form,  C2H5.O-CO.CH  :  C(OH).C02C2H5.  This  ester,  like  ethyl  aceto- 
acetate, is  used  in  many  syntheses,  the  hydrogen  of  the  methylene  group  being  replaceable 
by  sodium,  &c. 

ACETONEDICARBOXYLIC  ACID  (Pentanonedioic  Acid),  C02H  •  CH2  •  CO  •  CH2  • 
C02H,  forms  crystals  which  melt  at  135°,  losing  2CO2,  and  giving  acetone.  It  is  formed 
by  the  action  of  concentrated  sulphuric  acid,  in  the  hot,  on  citric  acid  : 

CH2.C02H  CH2-C02H 

H     =    C0  +  H°  +  C0 


CH2.C02H  CH2.C02H 

Citric  acid 

The  constitution  of  citric  acid  is  shown  by  its  formation  from  acetonedicarboxylic 
acid  by  the  action  of  hydrogen  cyanide  and  subsequent  hydrolysis. 

The  hydrogens  of  the  two  methylene  groups  are  replaceable  by  sodium,  so  that  this 
acid  can  be  used  in  syntheses  similar  to  those  effected  by  ethyl  acetoacetate. 

DIHYDROXYTARTARIC  ACID,  CO2H-CO-CO-C02H  +  2H2O,  or,  better, 
C02H-C(OH)2-C(OH)2-C02H,  melts  and  decomposes  "at  98°  and  forms  a  sodium  salt, 
which  is  sparingly  soluble  and  decomposes  readily  into  CO2,  and  sodium  tartronate, 
CO2H-CH(OH)-CO2Na. 

It  is  obtained  by  the  action  of  nitrous  acid  on  an  ethereal  solution  of  pyrocatechol, 
guaiacol,  &c.,  and  also  by  the  spontaneous  decomposition  of  nitrotartaric  acid.  Sodium 
bisulphite  converts  it  into  glyoxal,  while  with  hydroxylamine  it  forms  the  dioxime 


CITRIC    ACID  345 

corresponding  with  the  diketonic  form,  With  phenylhydrazine-sulphonic  acid,  it  forms 
tartrazine,  a  beautiful  yellow  colouring-matter  largely  used  in  dyeing  wool  and  silk. 

Of  the  higher  ketonic  acids  the  following  may  be  mentioned  :  hydro- 
chelidonic  acid  (acetonediacetic  acid),  CO(CH2-CH2-C02H)2;  diacetosuccinic 

CH3- CO* CH- C02H  OHfC'O'PH  VCO  H 

acid,  ;  and  diacetylqlutaric  acid,  CH2<C/-iTT //-(/-»  ntT\  n/VSj 

CH3.CO-CH-C02H  H3).',02H 

the  esters  of  which  give  rise  to  tetrahydrobenzene  derivatives  or,  in  presence 
of  ammonia,  to  pyridine  derivatives. 

G.  POLYVALENT  TRIBASIC  HYDROXY-ACIDS 

ETHANETRICARBOXYLIC  ACID,  C02H-CH2-CH(CO2H),,,  and  ASYM. 
PROPANETRICARBOXYLIC  ACID,  CO2H-CH2-CH2-CH(C02H)2.  These 
two  acids  are  stable  in  the  form  of  esters,  but  in  the  free  state  they  readily 
decompose,  liberating  C02  and  forming  dibasic  acids. 

TRICARBALLYLIC  ACID  (Symm.  Propanetricarboxylic  or  Pentadioic- 
3-methyloic  Acid),  CO2H-CH2-CH(C02H)-CH2-C02H,  melts  at  163°  and  is 
very  soluble  in  water. 

It  is  found  in  unripe  beets  and  occurs  abundantly  in  the  deposits  of  the 
vacuum  pans  of  sugar  factories.  Synthetically  it  is  obtained  from  aconitic 
acid l  by  the  addition  of  hydrogen  and  from  citric  acid,  which  loses  its  hydroxyl 
group  when  treated  with  hydriodic  acid. 

Its  constitution  is  shown  by  its  synthesis  from  glycerol  by  way  of  the 
tribromhydrin  and  tricyanohydrin,  C3H5(CN)3,  the  latter  being  hydrolysed. 

CH.,-C02H 

CITRIC  ACID,    €<?*?„ 
I       v/U2rl 

CH2-C02H 

This  acid  is  deposited  from  its  aqueous  solutions — if  these  are  not  too 
hot — in  large,  rhombic  prisms  containing  1H20,  which  is  given  up  partly  in 
dry  air  and  completely  at  130°.  It  melts  at  153°  and  at  a  higher  temperature 
decomposes  into  aconitic  and  itaconic  acids,  citraconic  anhydride,  C02,  and 
acetone.  It  is  readily  soluble  in  water  (135  :  100  at  15°  and  200  :  100  at  the 
boiling-point)  or  alcohol  (53  :  100  at  15°  and  about  double  as  much  in  80 
per  cent,  alcohol),  and  to  a  slight  extent  in  ether  (9  :  100).  It  was  dis- 
covered by  Scheele  in  1784  and  studied  by  Liebig  in  1838.  It  occurs 
abundantly  in  nature  in  the  lemon  (4-5  per  cent,  in  the  unripe  lemon),  orange, 
gooseberry,  and  other  fruits,  and  in  small  quantities  in  cows'  milk,  the 
shoots  and  leaves  of  the  vine,  tobacco,  and  fungi,  and  as  calcium  salt  in  the 
beet,  willow,  &c. 

Industrially  it  is  obtained  by  the  lime  method  described  later  (see  p.  349). 
Synthetically  it  may  be  prepared  from  acetonedicarboxylic  acid  by  the 
action  of  hydrocyanic  acid  and  subsequent  hydrolysis.  The  constitution 
thus  indicated  is  confirmed  by  its  formation  from  symm.  dichlorhydrin, 
CH2C1-CH(OH)-CH2C1,  which  on  oxidation  gives  symm.  dichloracetone, 

CH-CO2H 

II 

1  Aconitic  Acid  is  the  corresponding  unsaturated  acid,  C-CO2H    .     It  melts  at.  191°,  and  is  readily  soluble 

I 

CH2-CO2H 

in  water;  it  is  an  energetic  acid  and  is  converted  into  tricarballylic  acid  by  nascent  hydrogen.  It  is  prepared 
by  heating  dry  citric  acid,  which  loses  a  molecule  of  water. 

It  occurs  naturally  in  the  sugar-cane,  beet,  Aconitum  napellus,  &c. 


346  ORGANIC    CHEMISTRY 

and  hence  by   the   introduction    of   cyanogen  groups  and  hydrolysis  yields 
citric  acid  : 

CH2C1  CH2C1  CH2C1  CH2-CN  CH2-C02H 


ooga 

CH2C1  CH2C1  CH2C1  CH2-CN  CH2-C02H 

Citric  acid  was  prepared  some  years  ago  (Fabrique  de  produits  chimiques 
de  Thann  et  de  Mulhouse)  by  Wehmer's  biological  process  (Ger.  Pat.  72,957 
of  1893),  according  to  which  glucose  is  fermented  by  certain  moulds  (Citromyces 
Pfefferianus  and  Glaber,  and  Mucor  pyriformis),  the  yield  being  about  55  per 
cent,  of  the  sugar.  In  1909  E.  Buchner  and  H.  Wiistenfeld  studied  the  most 
favourable  conditions  for  the  development  of  Citromyces  citricus,  but  arrived 
at  no  practical  results. 

When  heated  for  a  long  time  with  water,  citric  acid  forms  a  little  aconitic 
acid,  into  which  it  is  transformed  -completely  by  concentrated  hydrochloric 
acid.  It  is  readily  oxidised  to  acetone,  oxalic  acid,  and  carbon  dioxide. 

Like  tartaric  acid,  citric  acid  hinders  the  precipitation  of  the  metallic 
hydroxides  from  their  salts  by  ammonia.1 

Citric  acid  is  used  in  large  quantities  for  lemonade  and  in  pharmacy  and  for  effer- 
vescent drinks  (citrate  of  magnesia)  ;  it  is  employed  also  in  dyeing,  analysis,  &c.  In 
normal  seasons,  the  price  is  about  £14  per  quintal. 

SALTS  OF  CITRIC  ACID.  Being  tribasic,  this  acid  forms  three  series  of  salts,  as 
well  as  two  different  monosubstituted  acids  and  two  disubstituted  acids.  The  alkali 
salts  are  all  soluble  in  water,  almost  all  of  the  others  being  insoluble,  although  dissolving 
in  alkali  citrates  owing  to  the  formation  of  double  salts  ;  in  such  solutions,  the  metals 
are  no  longer  precipitable  by  ammonia,  phosphates,  or,  alkali  carbonates.  When  heated, 
many  citrates  give  salts  of  aconitic  acid. 

CALCIUM  CITRATE.  (C6H5O7)2Ca3  +  4H20.  If  calcium  hydroxide  is  added  to  a 
dilute  solution  of  citric  acid,  no  precipitate  forms  in  the  cold  but  one  separates  in  the 
hot.  In  presence  of  ammonia,  calcium  chloride  gives  no  precipitate  in  the  cold,  while 
that  formed  in  the  hot  partly  dissolves  on  cooling  but  does  not  dissolve  in  caustic  soda, 
and  so  differs  from  calcium  tartrate  (see  p.  336).  In  moderately  concentrated  solutions, 
calcium  chloride  precipitates  calcium  citrate,  although  incompletely,  even  in  the  cold  ; 
in  the  hot,  precipitation  is  complete.  The  water  of  crystallisation  is  wholly  expelled  at 
about  200°. 

Calcium  citrate  is  soluble  in  ammonium  citrate  with  formation  of  a  double  salt 
precipitable  by  alcohol. 

The  manufacture  and  statistics  of  calcium  citrate  are  considered  later. 

BARIUM  CITRATE  is  less  soluble  in  cold  water  than  the  calcium  salt. 

MAGNESIUM  CITRATE,  (C6H6O7)2Mg3,  is  formed  by  dissolving  magnesium  car- 
bonate in  citric  acid  solution.  It  is  used  as  a  purgative  and  is  then  prepared  by  heating 
a  mixture  of  105  parts  of  powdered  citric  acid  with  30  parts  of  magnesium  oxide  cautiously 
at  100°  to  105°,  pouring  the  fused  mass  on  to  porcelain  tiles  and  powdering  when  cold. 
Large  quantities  of  effervescent  magnesia  are  prepared  nowadays  as  a  purgative  and 
refreshing  drink  by  mixing  magnesium  citrate  with  sodium  bicarbonate  and  small  pro- 
portions of  citric  acid  and  sugar,  and  granulating  the  mass  with  addition  of  a  little  glucose. 

1  Tests  and  Reactions  for  Citric  Acid.  Denigis'  reaction  is  characteristic  and  serves  to  detect  small  quanti 
ties  of  the  acid  :  the  solution  is  heated  to  boiling  with  one-twentieth  of  its  volume  of  Denigis'  reagent  (5  grins. 
of  mercuric  oxide,  80  c.c.  of  water,  and  20  c.c.  of  concentrated  sulphuric  acid),  3  to  10  drops  of  an  approximately 
decinormal  potassium  permanganate  solution  being  added  ;  a  white,  crystalline  precipitate  is  formed  immediately 
even  with  traces  of  citric  acid.  The  reaction  is  not  masked  by  the  presence  of  tartaric,  oxalic,  malic,  sulphuric, 
or  phosphoric  acid,  although  the  amount  of  permanganate  used  must  then  be  slightly  increased. 

The  presence  of  tartaric  acid  —  which  is  a  common  adulterant  —  in  citric  acid  may  be  detected  by  the  addition 
of  potassium  acetate,  the  acid  potassium  citrate  thus  formed  being  readily  soluble,  whilst  acid  potassium  tartrate 
is  only  slightly  soluble.  Minimal  quantities  of  tartaric  acid  may  be  also  detected  as  follows  :  1  grin,  of  the 
powdered  substance  is  heated  for  a  few  minutes  on  the  water-bath  with  1  c.c.  of  20  c.c.  ammonium  molybdate 
solution  and  a  few  drops  of  0-25  per  cent,  hydrogen  peroxide  solution  ;  in  presence  of  even  0-001  grm.  of  tartaric 
acid,  a  bluish  coloration  is  obtained.  The  presence  of  oxalic  acid  is  easily  discovered,  since  in  the  cold  and  in 
an  ammoniacal  solution  calcium  oxalate  is  insoluble,  whilst  calcium  citrate  is  soluble. 


CITRUS    INDUSTRY  347 

Citric    acid  and,  to  some  extent,  magnesium  citrate  are  often  adulterated  with  tartaric 
acid,  which  is  cheaper. 

CITRATE  OF  IRON  is  obtained  as  a  dark  red  colloidal  solution  by  dissolving  ferric 
hydroxide  in  cold  citric  acid  solution.  Such  solutions  of  different  concentrations  give, 
on  heating,  various  citrates  of  iron  which  are  soluble  in  ammonium  citrate  and  more 
or  less  soluble  in  water,  and  have  been  studied  in  recent  years  in  relation  to  their  colloidal 
character. 

CITRUS  INDUSTRY 

Citric  acid  is  manufactured  from  the  juice  of  lemons  yielded  especially  by  the  following 
three  plant  species :  Citrus  limonium,  Citrus  bergamia  (bergamot),  and  Citrus  limetta  (or 
wild  lemon  cultivated  by  the  English  in  Guiana  and  the  East  Indies).  Lemons  are 
cultivated  most  extensively  in  Sicily  and  Calabria  and  to  a  considerable  extent  also  in 
Spain.  The  cultivation  is  of  little  importance  in  Greece,  the  Sandwich  Islands,  and  the 
East  Indies,  but  is  rapidly  increasing  in  Australia.  During  recent  years  the  production 
of  oranges  and  lemons  has  made  rapid  strides  in  California  and  in  Florida,1  where  it  is 
already  about  double  that  of  Sicily.  It  is  pleasing  to  note  that  plantations  of  oranges 
alone  are  being  more  and  more  largely  replaced  by  those  of  lemons. 

Only  the  refuse  lemons  (one-fourth  of  the  total  production)  are  used  for  the  manu- 
facture of  citric  acid,  as  they  cost  only  half  as  much  as  the  picked  fruit. 

The  first  operation  to  which  the  lemons  are  subjected  is  peeling,  a  workman  removing 
the  peel  with  three  cuts  of  a  knife,  cutting  the  lemon  in  two  and  throwing  it  into  a  tub  ; 
the  peel  is  collected  separately  for  the  preparation  of  essence.  A  skilled  operative  can 
peel  more  than  4000  lemons  a  day.  From  8000  lemons,  pressed  in  a  suitable  press, 
600  litres  of  juice,  containing  4-5  to  6  per  cent,  of  citric  acid,  are  obtained  ;  only  9  to 
10  per  cent,  of  the  total  acid  exists  as  calcium  citrate.2  The  juice  does  not  keep  well 

1  The  lemon  orchards  in  Sicily  are  found  especially  on  the  coast  from  Palermo  to  Cefalu  (about  one-fifth  of 
the  total  production  of  lemons  and  oranges)  and  on  the  coast  near  Messina  (more  than  double  that  of  Palermo- 
Cefalu),  usually  on  irrigated  lands,  but  sometimes  in  cool  non-irrigated  districts.  The  stocks  are  obtained  from 
the  seed  of  the  wild  orange  (called  by  the  Sicilians  arancia  agr<±,  or  sour  orange).  The  plants  from  these  seeds 
are  planted  out  in  the  orchards  in  their  third  year  and  are  placed  from  3  to  5  metres  apart,  according  to  the 
nature  of  the  soil,  to  the  wind,  and  to  custom.  After  a  year  the  stock  is  grafted  from  an  adult  plant.  Fructifi- 
cation occurs  after  a  further  three  years  and  reaches  its  maximum  in  ten  years.  The  flowering  of  the  lemons 
on  tho  same  plant  is  progressive  and  lasts  the  whole  of  May  ;  from  the  latter  half  of  June  to  the  beginning  of 
October  the  plants  are  watered  every  fortnight.  The  maturation  of  the  fruit  is  gradual  from  November  to  the 
end  of  April  and  the  harvest  is  gathered  in  three  periods,  the  best  fruit  being  those  of  the  middle  one — December 
to  February  ;  the  last  fruit,  plucked  in  April  and  the  beginning  of  May,  arc  poorer  in  juice  and  thicker  in  the 
peel.  In  the  coast  district  of  Messina,  the  harvest  finishes  at  the  beginning  of  March. 

Lemons  have  also  been  forced  in  Sicily  during  the  past  few  years,  the  highly  valued  summer  fruit  being  thus 
obtained  ;  these  are  called  verdelli  (high  quality)  and  bianchetti  (lower  quality).  In  this  case  the  plants  are  not 
watered  during  June  and  July,  the,  leaves  withering  and  all  the  young  fruit  falling.  In  August,  water  in  abun- 
dance is  given  at  intervals,  and  sodium  nitrate  applied  as  fertiliser.  The  plant  then  suddenly  becomes  very 
vigorous,  and  in  a  few  days  is  covered  with  new  flowers,  the  fruit  ripening  rapidly  from  the  end  of  May  to  the 
close  of  the  summer,  and  that  gathered  in  June  or  July  being  of  the  highest  quality.  Such  plants  give  an  increased 
crop,  especially  if  manured,  and  the  fruit  commands  more  than  double  the  ordinary  prices.  This  procedure  is 
followed  in  orchards  where  the  soil  is  not  moist  and  can  be  left  to  dry  completely  and  where  the  lemons  are  not 
alternated  with  oranges  or  other  crops  requiring  watering. 

Under  favourable  conditions,  a  good  lemon  plant  should  yield  on  an  average  1000  lemons  a  year  (some  very 
large  plants  give  several  thousands).  The  price  varies  considerably,  8s.  to  16s.  per  1000  being  paid  for  the  fruit 
on  the  tree  and  as  mueh  as  24s.  for  the  gathered  fruit ;  forced  lemons  cost  at  least  20s.  per  1000,  the  price  in 
1907  exceeding  40s.  The  cost  of  gathering,  packing,  and  freight  to  the  port  varies  from  Is.  "id.  to  3s.  2d.  per 
1000.  The  refuse  lemons,  which  form  about  one-fourth  of  the  crop  (or  more  if  the  demand  for  lemons  is  small), 
cost  about  half  as  much  as  the  other  fruit  (5s.  to  6s.  per  1000  on  the  average),  although  on  rare  occasions  the 
price  reaches  8s.,  and  in  1908,  at  the  height  of  the  crisis,  it  fell  to  2s.  per  1000. 

*  Fresh  lemon  juice  contains  also  7  to  9  per  cent,  of  glucose,  0-2  to  0-8  per  cent,  of  saccharose  (according  as 
the  lemons  are  sour  or  ripe),  certain  extractive,  gummy,  and  pectic  substances  (about  0-2  per  cent,  for  ripe  and 
0-8  per  cent,  for  unripe  fruit),  and  about  0-5  to  0-7  per  cent,  of  inorganic  salts.  The  presence  of  these  substances 
renders  it  impossible  to  crystallise  the  citric  acid  merely  by  concentrating  the  juice,  even  when  all  the  glucose 
is  transfoimecl  into  alcohol  (5  to  6  per  cent.).  So  that,  even  at  the  present  time,  the  citric  acid  is  separated  by 
Scheele's  classical  and  rather  costly  process,  according  to  which  it  is  first  converted  into  calcium  citrate.  The 
high  price  of  fuel  has  prevented  the  establishment  of  the  citric  acid  industry  in  Sicily,  and  the  preparation 
of  the  acid  has  been  monopolised  for  a  long  time  by  England  and,  at  the  present  time,  largely  by  Germany.  Both 
these  countries  receive  the  raw  material  from  Sicily,  to  a  small  extent  as  lemons  packed  in  barrels  containing 
sea-water,  partly  as  concentrated  juice  (ugro  cotto),  but  mostly  as  calcium  citrate. 

In  consequence  of  the  development  of  lemon-growing  in  Spain,  and  especially  in  California  and  Australia, 
and  also  owing  to  an  agreement  entered  into  by  the  manufacturers  of  citric  acid,  the  condition  of  the  Sicilian 
growers  became  so  critical  that  in  1903  the  Italian  Minister  of  Agriculture  offered  a  prize  of  £6000  for  improve- 
ments in  the  industry  or  new  processes  of  value  to  the  cultivators.  This  sum  was  largely  wasted  by  Commissions 
who  achieved  nothing  or  by  rewarding  certain  favoured  individuals.  However,  at  the  end  of  1904,  Professor 
Ilestuccia,  of  Messina,  announced  to  the  Government  the  discovery  of  a  process  for  the  direct  extraction  of  citric 
acid  by  simple  concentration  of  the  juice,  to  which  was  previously  added  a  trace  of  a  substance — the  nature  of 


348  ORGANIC    CHEMISTRY 

(better  if  pasteurised  at  63°  to  65°),  and  is  usually  concentrated  at  once  in  open  pans 
with  direct-fire  heating  until  the  specific  gravity  reaches  60°  on  the  citrometer  (1-2394, 
0^28°  Be.),  and  the  product  represents  a  blackish  decoction  containing  300  to  400  grins, 
of  citric  acid  per  litre  (that  from  the  bcrgamot  of  Calabria  and  Messina  contains  300  grms., 
while  that  produced  in  the  Sandwich  Islands  and  in  the  Republic  of  Dominica  from 
lemons  of  the  limetta  species  has  a  density  of  1-32  and  contains  about  575  grms.  of  citric 
acid  per  litre).  The  boiling  decoction  is  passed  through  a  cloth  and  is  collected  in  casks 
for  transport. 

The  commercial  value  of  the  juice  (agro  cotto)  depends  on  the  content  of  citric  acid, 
and  is  determined  either  by  diluting  the  juice  and  titrating  with  normal  caustic  soda 
or  by  precipitating  in  the  hot  as  calcium  citrate  and  weighing  the  latter.  This  estimation 
is  preceded  by  a  qualitative  examination  to  ascertain  if  salt  has  been  added  to  increase 
the  specific  gravity  (test  with  silver  nitrate  in  presence  of  a  little  nitric  acid)  or  if  sulphuric 
or  hydrochloric  acid  has  been  added  to  raise  the  degree  of  acidity  (test  with  silver  nitrate 
or  barium  chloride  in  presence  of  a  little  nitric  acid). 

In  the  large  modern  factories,  the  juice  is  treated  in  almost  the  same  manner  as  in  the 
manufacture  of  tartaric  acid  (see  p.  341) :  into  100-hectol.  vessels  provided  with  stirrers 
and  cold-water  coils  are  placed  20  hectols.  of  concentrated  juice  and  80  hectols.  of  water, 
the  liquid  being  then  well  mixed  for  thirty  minutes  and  allowed  to  ferment,  the  glucose 
being  thus  converted  into  alcohol  and  the  juice  clarified.  By  passing  very  cold  water 
through  the  coil  the  temperature  of  the  liquid  is  lowered  to  5°,  and  a  large  part  of  the 
dissolved  and  suspended  extractive  and  mucilaginous  matters  separated  ;  in  presence 
of  a  little  tannin,  these  matters  coagulate  and  do  not  redissolve  (50  litres  of  sumach 
extract  at  10°  Be.  are  sufficient,  the  liquid  being  stirred  for  15  to  20  minutes  immediately 
after  the  addition).  The  solution  is  then  passed  to  the  filter-presses  and  thence  into 
20-hectol.  wooden  vats  or  into  brickwork  vessels  similar  to  the  preceding  ones,  but 
provided  with  perforated  coils  for  direct-steam  heating.  The  boiling  liquid  is  now 
neutralised  exactly  with  dense  milk  of  lime  or  with  powdered  calcium  carbonate.  The 
latter  causes  frothing  and  sometimes  overflow  of  the  liquid,  but  precipitates  a  purer 
calcium  citrate,  the  hydroxide  throwing  down  many  pectic  and  colouring  matters.  For 
every  100  kilos  of  citric  acid  present  (titrated)  45  kilos  of  quicklime  (57  of  slaked  lime 
or  80  of  the  carbonate)  are  added.  After  stirring  while  hot,  the  insoluble  tricalcic  citrate 
— which  forms  immediately — is  passed  at  once  through  the  filter-presses  and  washed 
with  very  hot  water  for  ten  minutes,  with  tepid  water  for  ten  minutes,  and  with  cold 
water  for  five  minutes.  In  Sicily,  calcium  citrate  is  prepared  in  a  primitive  method  (with 
slaked  lime  often  containing  magnesia,  which  yields  soluble  magnesium  citrate,  this 
being  lost)  and  is  sold  dry  with  a  content  of  64  per  cent,  of  citric  acid.  300  kilos  of  calcium 
citrate  of  this  strength  require,  on  the  average,  100,000  lemons,  the  peel  of  which  yields 
37  kilos  of  essence  selling  at  6s.  ±d,  per  kilo.  The  total  cost  of  manufacturing  calcium 
citrate  and  essence  from  100,000  lemons  is  about  £10.  The  cakes  of  calcium  citrate 
from  the  filter-presses  are  mixed  in  a  20-hectol.  lead-lined  vessel  with  15  hectols.  of  cold 

which  he  did  not  reveal  (picric  acid  I)— and  a  little  animal  charcoal.  But  this  process  only  led  to  further  waste 
of  money. 

In  1910,  Peratoner  and  Scarlata  suggested  the  following  new  process  for  extracting  the  essence  and  citric 
acid  from  the  lemons  directly,  without  conversion  of  the  acid  into  the  calcium  salt.  The  juice  obtained  by 
squeezing  the  minced  lemons  in  hydraulic  presses  is  partly  distilled  in  a  vacuum  on  a  water-bath  at  60°  to  recover 
the  essence  and  then  concentrated  in  vacuo  at  70°  until  it  acquires  a  syrupy  consistency  (one-tenth  of  the  original 
weight).  When  the  syrup  is  cold,  all  the  citric  acid  is  extracted  by  treatment  with  a  mixture  of  alcohol  and  ether, 
in  which  many  of  the  impurities  are  insoluble.  The  alcohol  and  ether  are  recovered  by  distillation,  and  the 
residue  diluted  with  a  little  water,  filtered,  and  concentrated  in  vanto  ;  after  standing  for  twelve  to  twenty-four  hours 
it  sets  to  a  yellowish  red  crystalline  mass  which,  after  defecation  and  decolorisation  in  the  ordinary  way  (animal 
charcoal,  Ac.),  gives  pure  colourless  crystals,  the  yield  being  60  to  70  per  cent.  The  remaining  acid  can  be 
separated  from  the  mother-liquor  as  citrate. 

In  spite  of  the  favourable  opinion  expressed  by  Professors  Garelli  and  Patern6,  this  process  does  not  seem  to 
have  been  applied  practically. 

Meanwhile  the  crisis  in  the  industry,  which  had  apparently  lessened  as  a  result  of  the  good  crops  and  prices 
of  1906  and  1907,  became  aggravated  in  1908  owing  to  the  diminished  demand  for  lemons,  to  the  American 
crisis,  to  the  agreement  between  the  producers  of  citric  acid  to  limit  the  amount  of  raw  material  required — thus 
lowering  prices  and  exhausting  the  usual  stocks  of  treated  products — and,  finally,  to  the  abundant  production, 
since  refuse  lemons  did  not  sell  for  2*.  6d  per  1000  at  the  beginning  of  1908  and  did  not  pay  for  gathering. 

Various  measures  have  been  taken  by  the  Italian  Government  to  protect  the  citric  acid  industry  in  Sicily, 

1  but  it  should  be  possible,  in  the  present  advanced  condition  of  technical  chemistry,  to   develop  this  industry 

without  such  aid.      The  sulphuric  acid  required  is  now  made  in  Sicily  itself,  and  by  the  use  of  multiple-effect 

evaporating  plant,  the  consumption  of  coal  may  be  reduced  to  a  minimum.     In  1911  a  large  citric  acid  factory 

was  erected  in  the  vicinity  of  Palermo  by  the  firm  of  Goldenbcrg,  from  Winckel,  near  Wiesbaden  (see  later). 


CITRIC    ACID    STATISTICS  349 

water,  the  lime  of  the  citrate  being  then  neutralised  exactly  with  dilute  sulphuric  acid 
(1  :  5)  (with  100  kilos  of  citric  acid  in  the  juice  correspond  400  kilos  of  this  dilute  acid)  ; 
a  slight  excess  of  sulphuric  acid  is  always  added,  since  the  presence  of  unaltered  calcium 
citrate  would  hinder  the  crystallisation  of  the  citric  acid. 

The  acid  is  added  in  portions  at  the  rate  of  5  litres  per  minute,  the  liquid  being  kept 
well  mixed  and  direct  steam  applied  through  a  perforated  leaden  coil.  The  mass  is  boiled 
for  ten  to  fifteen  minutes,  the  steam  then  suspended  and  the  whole  mixed  for  thirty 
minutes.  The  calcium  sulphate  is  then  removed  by  means  of  a  filter-press  and  is  washed 
with  200  litres  of  boiling  water,  which  is  added  to  the  first  filtrate,  and  then  with  cold 
water,  which  is  afterwards  used  for  treating  fresh  calcium  citrate.  The  citric  acid  solutions 
from  the  filter-presses  contain  only  minimal  quantities  of  sulphuric  acid  and  certain 
blackish  extractive  matters.  Concentration  of  the  solution  was  formerly  carried  out  in 
lead-lined  wooden  vessels,  4  metres  long,  2  metres  wide,  and  25  cm.  deep,  containing 
closed  steam  coils.  Evaporation  should  be  rapid  and  the  temperature  should  never 
exceed  65°  to  70°.  When  the  liquid  reaches  46°  (sp.  gr.  1-3),  almost  all  the  calcium 
sulphate  previously  remaining  in  solution  separates  ;  the  clear  liquid  is  then  siphoned 
into  a  similar  vessel  underneath,  the  concentration  being  continued  until  a  crystalline 
skin  forms  at  the  surface  of  the  liquid,  which  is  next  transferred  to  wooden  crystallising 
vessels,  2  metres  x  70  cm.  x  20  cm.  (deep)  ;  the  inner  surface  is  polished  with  plumbago. 
After  two  days,  the  dark  brown  mother-liquors  are  removed  and  the  yellowish  brown 
crystals  centrifuged.  In  order  to  separate  traces  of  dissolved  iron  from  the  mother- 
liquor,  this  is  treated  with  a  little  potassium  ferrocyanide  and  filtered  ;  two  or  three  further 
crops  of  dark-coloured  crystals  are  obtained,  the  very  dark  mother-liquor  finally  obtained 
being  added  to  fresh  lemon -juice. 

In  modern  factories  the  citric  acid  solution,  freed  from  calcium  sulphate  by  filter- 
pressing,  is  concentrated  in  vacuum  apparatus,  just  as  in  the  sugar  and  tartaric  acid 
industries.  In  this  way,  the  temperature  does  not  exceed  60°  to  65°  and  with  a  triple- 
effect  apparatus,  not  only  rapidity  but  also  economy  of  fuel  is  attained  (see  vol.  i,  p.  442, 
and  also  section  on  Sugar). 

The  brown  crystals  first  obtained  are  refined  and  decolorised  by  dissolving  them  in 
rather  more  than  double  their  weight  of  water  and  boiling  the  solution  with  animal  char- 
coal previously  treated  with  hydrochloric  acid  and  with  other  substances,  as  already 
mentioned  in  considering  the  refining  of  tartaric  acid  (p.  342). 

In  all  the  washing  and  refining  operations,  pure  water  with  little  hardness  is  always 
employed. 

STATISTICS  AND  PRICES.  The  production  of  oranges,  lemons,  &c.,  in  Italy 
(Calabria  and  Sicily)  is  as  follows  : 

In  the  five  years  1891-1895,  2-60  thousand  millions  of  fruit  per  annum 
„       „      1896-1900,  3-72 
„       „      1901-1905,  5 
year  1907 1  6 

In  1909,  Italy  exported  1,109,000  quintals  of  oranges  and  2,560,600  quintals  of  lemons 
(£920,000),  and  in  1910, 1,204,300  quintals  of  oranges  (£481,720)  and  2,670,000  of  lemons 
(£929,840). 

Sicily  exported  : 

14,428  quintals  of  agro  cotto,  value  £36,360  in  1903 

21,448  „  „  „  „  £54,050  „  1904 

12,000  „  „  „  „  £35,520  „  1905 

6,000  „  „  „  „  £18,000  „  1907 

7,500  „  „  „  „  £22,000  „  1908 

1,000  „  „  „  „  £3,200  „  1909 

As  the  exportation  of  agro  cotto  diminished,  that  of  calcium  citrate  (in  casks  called 
pipes,  holding  305  kilos)  increased  as  follows  : 

1  While  in  other  years  the  picked  lemons  for  use  as  fruit  sold  for  12s.  or  even  16s.  per  1000  (i.e.  1J  canlaros  = 
about  125  kilos),  and  the  forced  fruit  for  as  much  as  32s ,  the  quotations  in  July  1908  were  as  follow  :  ripe  lemons 
(gathered  in  winter  and  spring),  5s.  <ld.  to  8s.  per  1000 ;  verdelli,  17s.  0<i  to  20s. ;  bianchetti,  8s.  to  10s. ;  for 
pressing,  2s.  to  2s.  4d. 

X 


350 


ORGANIC    CHEMISTRY 


1903 
1904 
1905 
1906 
1907 
1908 
1909 
1910 


32,793  quintals,  value  £135,160  ;   mean  price,    92s.  per  quintal 


54,310 
41,259 
51,498 
61,684 
77,101 
23,800 
64,755 


£221,240  ; 
£181,520  ; 

£227,800  ; 
£444,120  ; 
£400,920  ; 
£123,808  ; 
£414,400  ; 


1005. 

1085. 


1605. 
1205. 
100s. 
1275. 


In  1909,  on  account  of  the  crisis  in  the  industry,  exportation  diminished  considerably, 
and  the  price  fell  as  low  as  81 5.  Gd.  per  quintal. 

The  calcium  citrate  l  exported  went  to  the  following  countries  : 


1905 

1906 

1907 

1908 

1909 

1910 

Quintals 

Quintals 

Quintals 

Quintals 

Quintals 

Quintals 

Austria-Hungary    . 

1,900 

600 

1,340 

3,371 

701 

2,142 

Belgium 

2,400 

2,600 

3,930 

2,678 

560 

1,723 

France. 

10,000 

15,300 

20,700 

20,915 

6,874 

14,203 

Germany 

1,200 

1,900 

2,150 

2,854 

508 

2,125 

England       --. 

8,800 

9,400 

10,000 

12,877 

3,834 

13,097 

United  States 

15,600 

21,000 

21,400 

24,147 

10,400 

24,488 

In  1903,  281  works  in  Calabria  and  Sicily  for  the  preparation  of  agro  cotto  employed 
a  total  of  4000  workmen  and  240  h.p. 

The  annual  production  of  refined  citric  acid  in  Europe  varies  from  35,000  to  40,000 
quintals  and  the  price  from  2165.  to  280s.  per  quintal.  In  general  the  price  rises  and 
falls  with  that  of  tartaric  acid,  the  difference  between  the  prices  of  the  two  acids  being 
due  to  the  different  degrees  of  acidity  (3  carboxyls  in  one  case  and  2  in  the  other)  and 
molecular  weights  (152  and  192). 

In  1897  Germany  imported  2350  quintals  and  exported  1070  quintals 
„  1902         „  „  3060        „        „          „          1630       „ 

,,  1905         „  „  „        „          „          3793      „ 

„  1909         „  „  about  1926        „        „          „          3668       „ 

Germany  also  imported  3600  quintals  of  lemon-juice  in  1908  and  1700  quintals  in  1909. 

Italy  imported  about  1140  quintals  (600  from  Germany)  of  citric  acid  in  1907  ;  1644 
in  1908  ;  1437  (£9268)  in  1909  ;  and  1094  in  1910  ;  the  exports  were  only  10  quintals 
in  1909.  The  import  duty  in  Italy  was  formerly  85.  per  quintal,  but  was  raised  in  1909 
to  £2  to  protect  a  large  factory,  with  £40,000  capital,  erected  in  1910-1911  near  Palermo 
by  the  firm  of  Goldenberg,  which  also  makes  sulphuric  acid  and  tartar  products.  The 
first  certain  result  of  this  procedure  will  be  to  raise  the  price  of  citric  acid  in  Italy  by 
£2  per  quintal,  while  Italian  citric  acid  will  be  much  cheaper  in  other  countries  than 
in  Italy. 

In  Austria  there  are  two  citric  acid  factories,  which,  in  1906,  imported  544  quintals 
of  calcium  citrate  from  Sicily,  1450  from  Turkey,  and  4356  from  Greece.  France  has 
two  factories,  these  importing  18,113  quintals  of  Sicilian  calcium  citrate  in  1906.  In 
Germany  there  are  nine  citric  acid  works  and  four  of  pure  citrates,  13,180  quintals  of 
Sicilian  calcium  citrate  being  imported  in  1908.  In  England  there  are  ten  works,  almost  all 
in  London.  The  United  States  have  three  very  large  factories  which  produce  more  than 
10,000  quintals  of  citric  acid  and  import  also  a  certain  quantity  from  Europe,  although 

1  M.  Spica  (1910)  has  suggested  a. simple,  rapid,  and  exact  method  for  the  analysis  of  calcium  citrate,  the 
content  of  citric  acid  being  obtained  from  the  volume  of  carbon  monoxide  generated  when  the  citrate  is  heated 
with  concentrated  sulphuric  acid.  2  grins,  of  the  cjtrate,  moistened  in  a  flask  on  the  water-bath,  are  treated 
with  25  c.c  of  concentrated  sulphuric  acid.  By  means  of  a  current  of  carbon  dioxide,  all  the  carbon  monoxide 
is  driven  into  a  nitrometer  similar  to  that  illustrated  in  BMg.  16  (p.  10),  the  carbon  dioxide  being  absorbed  in 
caustic  soda.  Each  c.c.  of  CO  at  0°  and  760  mm.  corresponds  with  0-009407  grin,  of  citric  acid,  C6H8O7  +  H^O  ; 
the  method  cannot  be  used  with  citrate  adulterated  with  oxalate  or  tartrate. 


THIO-ACIDS,    AMINO-ACIDS,    ETC.         351 

the  protective  duty  is  63s.  per  quintal  ;    calcium  citrate,  which  is  all  imported,  is  free 
from  duty. 

Of  the  HIGHER  POLYBASIC  HYDROXY-ACIDS  the  following  may  be  mentioned : 
desoxalic  acid,  CO2H-CH(OH)-C(OH)(C02H)2,  which  forms  deliquescent  crystals  and, 
on  boiling  with  water,  loses  CO2  and  gives  uvic  acid  ;  hydroxycitric  acid  (dihydroxytri- 
carballylic  acid),  C3H3(OH)2(C02H)3,  found  in  the  beet  ;  acetonetricarboxylic  acid  and 
various  acids  which  contain  four,  five,  or  even  more  carboxyl  groups  and  are  of  synthetic 
and  not  of  natural  origin. 

IV.  THIO-ACIDS  AND  THIO-ANHYDRIDES 

These  may  be  regarded  as  acids  or  anhydrides  in  which  an  oxygen  atom  is  replaced  by 
sulphur,  as  in  THIOACETIC  ACID  (Ethanthiolic  Acid),  CH3- CO -SH,  which  is  obtained 
by  the  action  of  phosphorus  pentasulphide  on  acetic  acid  and  is  a  colourless  liquid  boiling 
below  100°,  giving  an  odour  of  acetic  acid  and  hydrogen  sulphide  ;  these  two  compounds 
are  also  formed  by  the  action  of  water  on  the  acid.  ETHANTHIOLTHIOLIC  ACID, 
CH3-CS-SH,is  a  dithio-acid,  and  ACETYL  SULPHIDE,  (CH3-CO)2S,  a  thio-anhydride. 
The  esters  corresponding  with  these  acids,  e.g.  ETHYL  THIO ACETATE,  CH3-CO-SC2H5, 
a  liquid  boiling  unchanged  and  yielding  the  acid  and  mercaptan  on  hydrolysis,  are  also 
known. 

V.  AMIDO-ACIDS,  AMINO-ACIDS,  IMIDES,  AMIDINES,  THIOAMIDES, 
IMINO-ETHERS,  AND  ANALOGOUS  COMPOUNDS 

A.  AMIDO-ACIDS  (AMIDES)  AND  DERIVATIVES 

Like  the  amines  (see  p.  200),  the  amides  may  be  regarded  as  derivatives 
of  ammonia,  the  hydrogen  atoms  of  which  are  replaced,  not  by  alkyl,  but  by 
acid  radicals. 

There  are  thus  primary,  secondary,  and  tertiary  amides,  which  are  obtained 
by  the  replacement  of  one,  two,  or  three  atoms  of  hydrogen,  and  are  sharply 
distinguished  from  the  amines,  as  they  are  readily  hydrolysed  by  alkali,  acid, 
or  superheated  water,  giving  ammonia  and  the  corresponding  acids.  They 
are  generally  crystalline  substances  soluble  in  alcohol  or  ether,  and  the 
lower  members,  especially  of  the  primary  amides,  dissolve  also  in  water. 
Their  boiling-points  are  much  higher  than  those  of  the  corresponding 
amines. 

Amides  are  also  known  in  which  one  or  two  atoms  of  the  ammoniacal 
hydrogen  are  replaced  by  alkyl  radicals,  i.e.  alkylated  amides,  e.g.  ethyl- 
acetamide  or  acetylethylamine,  CH3-CO-NH-C2H5,  and  dimethylacetamide, 
CH3-CO-N(CH3)2,  from  which,  on  hydrolysis,  only  the  acid  is  separated, 
the  alkyl  residue  or  residues  remaining  joined  to  the  amino-group,  forming 
noii-hydrolysable  amines. 

PREPARATION.  (1)  By  dissolving  an  alkyl  cyanide  (nitrile)  in  con- 
centrated sulphuric  acid,  either  with  or  without  concentrated  acetic  acid, 
concentrated  hydrochloric  acid  or  hydrogen  peroxide,  a  molecule  of  water 
is  added:  CH3-CN  +  H2O  =  CH3-CO-NH2.  By  heating  acids  or  anhy- 
drides with  nitriles,  secondary  or  tertiary  amides  are  formed. 

(2)  The  action  of  ammonia  solution  or  solid  ammonium  carbonate  on 
acid  chlorides  yields  primary  amides,  whilst,  if  the  ammonia  is  replaced  by 
an  arnine,  an  alkylated  amide  is  obtained  : 

CH3-CO-C1  +  2NH3  =  NH4C1  +  CH3-CO-NH2 
CH3-CO-C1  +  2NH2-C2H5  =  C2H5-NH2,  HC1  +  CH3-CO-NH-C2H5. 

Ethylamine  hydrochloridc  Ethylacetamide 

On  the  other  hand,  the  anhydrides  give,  with  ammonia,  the  primary 
anhydride  and  an  ammonium  salt. 


352  ORGANIC    CHEMISTRY 

(3)  By  heating  ammonium  salts  of  the  fatty  acids  in  closed  vessels  at 
about  250°,  primary  amides  are  formed  : 

CH3-C02NH4  =  H20  +  CH3-CO-NH2. 

Properties.  Unlike  the  amines,  the  amides  have  only  a  very  feeble  basic 
character,  owing  to  the  presence  of  the  negative  acid  radical,  and  only  the 
primary  ones  give  additive  products  with  acids,  e.g.  CH3-CO-NH2,  HC1, 
acetamide  hydrochloride,  which  is  decomposed  even  by  water.  Also  certain 
sodium  and  mercuric  derivatives  are  known,  e.g.  (CH3-CO-NH)2Hg,  which 
exhibit  the  amides  as  feebly  acid  compounds,  one  of  the  hydrogen  atoms  of 
the  amido-group  being  replaceable  by  metals. 

With  nitrous  acid,  amides  react  similarly  to  primary  amines,  giving  the 
acid  and  liberating  nitrogen  : 

CH3-CO-NH2  +  N02H  =  H20  +  N2  +  CH3-C02H. 

Removal  of  water  from  primary  amides  by  means  of  phosphorus  penta- 
chloride  or  pentoxide  results  in  the  formation  of  alkyl  cyanides  (nitriles). 

By  the  gradual  action  of  bromine  in  presence  of  alkali,  the  corresponding 
amine  with  one  less  carbon  atom  is  finally  obtained,  while  urea  derivatives, 

WTT-  POPTT 

such  as  methylacetylurea,  CO^ivH-CH  3'  are  ^orme(*  as  intermediate  pro- 
ducts, these  being  decomposable  by  excess  of  alkali  ;  an  intermediate  bromo- 
compound,  e.g.  acetobromamide,  CH3-CONHBr,  is  also  formed,  this  giving 
the  amine  with  liberation  of  C02 : 

CH3-CO-NHBr  +  KOH  =  KBr  +  C02  +  CH3-NH2. 

When,  however,  the  acid  residue  contains  more  than  five  carbon  atoms, 
the  nitrile  is  obtained  instead  of  the  amine,  which  is  acted  on  by  the  bromine  : 
CnH2w+1-CH2-NBr2  =  2HBr  +  CnH2M+1-CN.  Since  the  nitriles  can  be  con- 
verted into  the  acids  containing  one  less  carbon  atom  than  the  amides  from 
which  they  originate,  it  is  hence  possible  to  pass  gradually  from  higher  acids 
to  more  and  more  simple  ones. 

The  ready  hydrolysability  and  the  methods  of  formation  of  amides  confirm 
their  constitutional  formula,  X-CO-NH2.  But  with  the  alkali  salts,  the 
existence  of  the  isomeric  modification,  X-C(OH):NH  (see  Tautomerism, 
pp.  17  and  330)  is  assumed,  but  if  the  hydrogen  of  the  hydroxyl  or  amino- 
group  is  replaced  by  an  alkyl  residue,  no  tautomeric  forms  occur,  only  true 
structural  isomerides,  X  •  CO  •  NHR  and  X  •  C(OR)  :  NH.  The  latter  are  termed 
imino-ethers  and  are  derived  from  the  hypothetical  imino -hydroxides  of  the 
acids,  e.g.  CH3-  C(OH)  :  NH.  They  are  prepared  by  the  action  of  a  nitrile 
on  an  alcohol  in  presence  of  gaseous  hydrogen  chloride  ;  thus,  with  HCN, 
the  hydrochloride  of  formiminic  ether,  CH(OC2H5)  :  NH,  is  obtained  as  a  white 
powder. 

It  is  worthy  of  mention  that  Effront  decomposes  amino-acids  on  an 
industrial  scale  by  means  of  special  ferments  so  as  to  obtain  fatty  acids  and 
ammonia  from  them  (see  pp.  155  and  288). 

FORMAMIDE  (Methanamide),  H  •  CO  -NH2,  prepared  as  described  above,  is  a  liquid 
which  is  soluble  in  water  and  alcohol,  boils  at  200°  with  partial  decomposition,  and  gives 
ammonia  and  carbon  monoxide  when  rapidly  heated  ;  with  P2O5  it  yields  HCN,  and 
with  chloral,  an  additive  product,  chloralamide,  which  is  used  as  an  antiseptic  and  hypnotic. 

ACETAMIDE  (Ethanamide),  CH3-CO-NH2,  forms  needles  melting  at  82°  and  boils 
at  222°.  Diacetamide,  (CH3-CO)2NH,  melts  at  78°,  boils  at  223°,  and  is  obtained  by 
heating  acetamide  with  acetic  anhydride. 

OXAMIC  ACID,  CO2H-CO-NH2,  is  the  monamide  of  oxalic  acid  and  is  obtained 
as  a  white,  crystalline  powder,  slightly  soluble  in  cold  water,  when  ammonium  oxalate  is 
heated. 


SUCCINIMIDE  353 

OXAMIDE,  NH2-CO-CO-NH2,  is  the  diamide  or  normal  amide  of  oxalic  acid,  and 
is  obtained  by  the  partial  hydrolysis  of  cyanogen  or  by  distillation  of  ammonium  oxalate. 
In  appearance  it  closely  resembles  oxamic  acid  and  it  is  insoluble  in  water  or  alcohol 
and  is  readily  hydrolysed  ;  elimination  of  water  (by  P205)  from  it  leads  to  cyanogen. 

SUCCINAMIC  ACID,  CO2H-CH2-CH2-CO-NH2,  is  analogous  to  oxamic  acid,  and 
succinamide,  NH2  •  CO  •  CH2  •  CH2  •  CO  •  NH2,  is  prepared  similarly  to  oxamide,  to  which 
it  is  analogous  ;  succinamide  crystallises  from  water  in  shining  needles,  and  decomposes 
at  200°  into  ammonia  and  succinimide. 

Of  the  amides  of  hydroxy-acids,  only  the  following  need  be  mentioned  : 

GLYCOLL  AMIDE,  OH-CH2-CO-NH2,  which  is  obtained  by  treating  the  ester  of 
glycollic  acid  with  ammonia  or,  better,  by  heating  ammonium  tartronate  at  150°,  melts 
at  120°  and  has  a  sweet  taste.  The  diglycollamides,  NH2-CO>CH2'O>CH2'CO2H  and 
(CH2-CO-NH2)20,  are  also  known,  the  latter,  on  heating,  giving  ammonia  and  digly- 

PTT    .  p/1 

collimide,  0<;±2  ^r>NH,  which  melts  at  142°. 
vll2  *  L/U 

MALIC  ACID,  CO2H-CH2-CH(OH)-CO2H,  forms  two  amides  by  means  of  its  two 
carboxyl  groups,  an  amine  by  means  of  its  alcoholic  group  (aspartic  acid),  and  also  an 
amino  -amide  (asparagine). 

MALAMIC  ACID,  NH2-CO-CH2-CH(OH)-C02H,  is  known  best  as  its  crystalline 
ethyl  ester,  which  is  formed  by  the  action  of  ammonia  on  an  alcoholic  solution  of  ethyl 
malonate. 

MAL  AMIDE,  NH2-CO-CH2-CH(OH)-CO-NH2,  is  formed  by  the  action  of  ammonia 
on  ethyl  malonate  in  the  dry  state. 

B.  IMIDES  AND  IMINO-ETHERS 

Attention  must  be  drawn,  not  so  much  to  the  secondary  amides  (in  which 
two  hydrogen  atoms  of  ammonia  are  replaced  by  two  acid  residues,  as  in 
diacetamide,  (CH3-CO)2NH,  which  contains  the  iminic  group,  NH)  or  to  the 


tautomeric  form  of  the  primary  amides  (with  X-C\  corresponds  the 

XNH2 


isomeride  X  •  C<         ,  which  is  well  known  in  the  form  of  imino-ethers,  X  • 


or,  in  the  case  of  the  imidohydrin  of  glycollic  acid,  OH-CH2-CV         ,  in  the 

X 


free  state)  as  to  the  imides  of  certain  dibasic  acids. 

CCK 
OXIMIDE,     )      /NH   (perhaps  with  the  double  formula),  is  formed  on 

or 

elimination  of  water  from  oxamic  acid  (by  PC15). 

CHa-C<X 
SUCCINIMIDE,     |  /NH,  is  obtained  by  heating  succinic  anhydride 

CH-2CCT 

in  a  current  of  ammonia  or  by  heating  the  diamide  or  rapidly  distilling  mono- 
ammonium  succinate,  as  has  been  mentioned  on  p.  306,  where  the  reason  was 
given  for  the  ready  formation  of  the  closed-ring  internal  anhydrides. 

Succinimide  melts  at  126°  and  boils  at  288°,  crystallises  with  1H20  and 
exhibits  the  characters  of  an  acid,  the  iminic  hydrogen,  influenced  by  the  two 
carboxyl  groups,  being  replaceable  by  acids.  On  the  other  hand,  when  they  are 
treated  with  alkali,  these  imides  gives  the  amides  from  which  they  originate, 

CH2-CCk  CH2-C02H 

a  molecule  of  water  being  added  :    I  /NH  +  H20  =   I 

CH2-C(/  CH2-CO-NH2 

It  is  interesting  that,  when  succinimide  is  distilled  over  zinc  dust,  it  yields 
H  23 


354  ORGANIC    CHEMISTRY 

CH:CH, 

pyrrole,  \  /NH,  while,  if  it  is  heated  in  alcoholic  solution  with  sodium 

CH  :  GET 

0x12*  Oxl2\ 

(reduction),  it  gives  Pyrrolidine,    |  /NH. 

CH^  •  CH2 

CH2-C(X 
AlsoPhenylsuccinimide(Succinanil),  |  /N-C6H5,  is  known  and  its 

CH2-C(T 

various    transformations    confirm    the  symmetry  of  its   own  structure  and 
consequently  also  that  of  succinimide. 

PT-T   •  PO 

GLUTARIMIDE,  CH2<^2  ^>NH,  is  obtained  by  distilling  ammonium 

glutarate  ;   it  melts  at  152°  and  gives  a  little  pyridine  when  heated  with  zinc 
dust. 


C.  AMINO-ACIDS  AND  THEIR  DERIVATIVES 

In  the  amino-acids,  it  is  the  hydrogen  in  direct  union  with  carbon  that  is 
replaced  by  the  NH2-group,  the  carboxyl  group  remaining  intact,  so  that 
these  compounds  have  both  acidic  and  basic  functions  and  can  hence  be  readily 
separated  from  other  substances,  since  after  the  carboxyl  is  esterified,  salts 
such  as  the  hydrochlorides  of  the  amino-group  are  formed. 

These  substances  and  their  derivatives  are  of  considerable  importance  in 
animal  and  vegetable  physiology,  since  they  are  found  among  the  products 
of  the  gradual  synthesis  and  decomposition  of  the  proteins  in  the  living 
organism  ;  they  are  also  of  interest  theoretically,  as  they  form  intermediate 
products  in  various  chemical  syntheses. 

The  a-amino-acids  are  readily  obtained  by  the  action  of  ammonia  on  the 
cyanohydrins  of  ketones  and  aldehydes  and  hydrolysis  of  the  remaining 
nitrile  group : 

/OH  /NH2 

CH,-  Cf-H     +  NH,  =  H90  +  CH, 


L3    ^\  JJL         i     •L'J"13          J-L2V-'     i     VyJ-L3 

XCN  XCN 

Nitrile  of  lactic  acid  Nitrile  of  alaiiiiie 

sNH 

2H2O  =  NH3  -f-  Clla'Cx; — JH 


CN  C02H 

Alaninc  (a-Aminopropionic  acid) 

They  are  also  formed  generally  by  reducing  the  oximes  of  ketonic  acids 
or,  better,  by  the  action  of  ammonia  on  halogenated  acids  : 

C02H-CH2C1  +  NH3  =  HC1  +  C02H-CH2-NH2. 

We  may  also  mention  the  interesting  Korner-Menozzi  reaction  (see  p.  314), 
which  allowed  these  authors,  by  inverting  the  reaction,  to  pass  from  the  esters 
of  unsaturated  acids  (fumaroid  or  maleinoid  form)  to  a  single  form  of  the 
corresponding  saturated  amino-acids  by  simple  treatment  with  ammonia  (or 
even  an  alkylamine  in  alcoholic  solution). 

With  nitrous  acid,  the  amino-acids  give  hydroxy-acids  and  they  give 
many  reactions  analogous  to  those  of  the  hydroxy-acids  and  varying  with  the 
position  of  the  amino-group. 

Two  molecules  of  an  a-amino-acid  readily  lose  2  mols.  of  water,  giving 
a  kind  of  anhydride  with  an  imido-ketonic  character  : 


GLYCINE,    BETAINE,    ASPARTIC    ACID     355 


C02H-CH2-NH2  CO-CH2-NH 

=  2H2O  +  | 

NH    CH-C0H  NH-CH-CO 


2        22  2 

The  y-amino-acids,  however,  give  internal  anhydrides  analogous  to  the 
lactones  and  termed  Lactams  : 

C02H  •  CH2  •  CH2  •  CH2  •  NH2  =  H20  +  CO  •  CH2  •  CH2  •  CH2 

—  NH 


The  /3-amino-acids,  when  heated,  evolve  ammonia  and  give  unsaturated 
acids. 

GLYCOCOLL  (Glycine,  Aminoacetic  or  Aminoethanoic  Acid,  or  Amine  of  Glycollic 
Acid),  CO2H-CH2-NH2,  is  formed  on  boiling  gelatine  with  alkali  [Ba(OH)2]  or  acid 
(dilute  H2SO4)  or  on  heating  hippuric  acid  (benzoylglycocoll)  with  dilute  acid  : 
CO2H.CH2.NH.CO.C6H5  +  H2O  =  CO2H.CH2-NH2  +  C6H5-CO2H  (benzoicacid).  Syn- 
thetically it  is  obtained  from  monochloracetic  acid  and  concentrated  ammonia  (see 
p.  322)  ;  if  the  ammonia  is  replaced  by  methylamine,  sarcosine,  CO2H  •  CH2  •  NH  •  CH3, 
m.pt.  115°,  is  obtained,  or  if  by  trimethylamine,  betaine  (see  p.  323)  is  formed  : 


C02H.CH2C1  +  N(CH3)3  =  HC1  +  CO.CH2.N(CH3)3. 


Betaine,  C5HH02N,  crystallises  with  1H2O,  which  it  loses  at  100°,  or  in  a  desiccator 
over  sulphuric  acid.  It  dissolves  in  water  or  alcohol,  from  which  it  is  precipitated  by 
ether  or  as  betaine  hydrochloride,  by  hydrochloric  acid.  This  solid  hj'drochloride  ;s  soluble 
in  water,  which  hydrolyses  it  to  a  considerable  extent,  the  solution  then  behaving  like 
hydrochloric  acid.  Owing  to  this  property  it  is  sold,  under  the  name  of  acidol,  in  pastilles 
containing  exact  and  suitable  doses  for  stomach  complaints,  and  replaces  solutions  of 
hydrochloric  acid  for  this  purpose  ;  the  same  effect  as  that  of  the  acid  is  thus  obtained 
by  a  solid  product.  Betaine  is  a  feeble  base,  and  is  not  decomposed  even  by  boiling  aqua 
regia  ;  at  high  temperatures  it  decomposes,  giving  trimethylamine.  It  occurs  abundantly 
in  beet-sugar  molasses  (10  to  12  per  cent.,  besides  1  to  2  per  cent,  of  leucine  and  isoleucine 
and  5  to  7  per  cent,  of  glutamic  acid),  from  which  it  is  extracted  by  means  of  alcohol  ; 
after  evaporation  of  this  solvent,  it  is  separated  as  hydrochloride. 

The  action  of  tertiary  amines,  other  than  trimethylamine,  with  mor.ochlo!  acetic  acid 
gives  various  compounds  to  which  is  given  the  name  of  BETAINES. 

Substitution  in  the  amino-group  of  the  amino-acids  also  yields  other  interesting 
compounds,  e.g.  Aceturic  Acid  (acetylglycocoll),  C02H  •  CH2  •  NH  •  CO  •  CH3,  melting  at  206°. 

The  properties  of  glycocoll  and  its  salts  are  given  on  p.  322. 

In  the  amino-acid  group  is  also  found  SERINE  or  a-amino-/3-hydroxypropionic  acid, 
CO2H-CH(NH2)-CHg-OH,  which  is  obtained  on  boiling  silk  gelatine  with  dilute  sulphuric 
acid  or  syntheticaHy  from  glycollic  aldehyde,  ammonia,  and  hydrocyanic  acid.  LEUCINE 
(a-aminoisocaproic  acid),  CO2H-CH(NH2)-CH2-CH(CH3)2,  is  obtained  synthetically  by 
hydrolysing  the  nitrile  of  isovaleraldehyde-ammonia,  and  is  usually  found  with  glycine 
among  the  products  of  decomposition  of  the  proteins  by  acid  or  alkali,  and  is  then  optically 
active  (the  carbon  atom  adjacent  to  the  carboxyl  being  asymmetric). 

ASPARTIC  ACID  (Aminosuccinic  Acid),  C02H-CH2-CH(NH2)-CO2H,  is 
one  of  the  most  important  products  obtained  by  the  decomposition  of  proteins 
by  acid  or  alkali.  It  occurs  in  abundance  (laevo-rotatory)  in  beet-sugar 
molasses,  and  has  been  prepared  by  various  synthetic  methods,  e.g.  by  the 
action  of  ammonia  on  bromosuccinic  acid. 

Three  stereoisomerides  are  known,  two  of  them  being  optically  active 
owing  to  the  presence  of  an  asymmetric  carbon  atom.  They  are  obtained  in 
small,  tabular,  dimetric  crystals,  soluble  to  some  extent  in  hot  \vater.  Their 
cold  solutions  and  also  acid  solutions  of  the  dextro-rotatory  acid  have  a  sweet 


356  ORGANICCHEMISTRY 

taste,  but  hot  solutions  or  alkaline  solutions  of  the  Isevo -rotatory  acid  are 
without  taste. 

They  give  the  general  reaction  of  amines  and  amides  with  nitrous  acid, 
being  converted  into  malic  acid.1 

The  higher  homologue  of  aspartic  acid  is  Glutamic  Acid  (a-aminoglutaric 
acid),  C02H  •  CH(NH2)  •  CH2  •  CH2  •  C02H. 

Among  the  DIAMINO-ACIDS  we  have  Lysine,  C02H-CH(NH3)-  [CH2]4-NH2,  which 
is  obtained  by  the  action  of  acids  on  proteins  or  by  synthetical  methods  ;  on  putrefaction 
it  gives  pen  tame  thylenediamine. 

Ornithine,  C02H-CH(NH2)-  [CH2]3-NH2,  is  the  lower  homologue  of  lysine  and  gives 
tetramethylenediamine  (putrescine)  on  putrefaction. 

Taurine  (Ethyleneaminosulphonic  Acid),  SO3H'CH2'CH2-NH2,  is  found  in  ox-bile 
combined  with  cholic  acids  as  taurocholic  acid  (for  properties  of  taurine,  see  p.  214). 

Cysteine  (Thioserine),  C02H-CH(NH2)-CH2'SH,  is  formed  by  the  reduction  of  cystine, 
C02H-CH(NH2)-CH2-S-S-CH2-CH(NH2)-CO2H,  which  occurs  in  urinary  sediments 
(calculi). 

ASPARAGINE,  NH2-CO-CH2-CH(NH2)-CO2H,  is  the  amide  of  aspartic 
acid.  It  was  first  found  in  asparagus,  but  is  moderately  widespread  in  almost 
all  vegetables  (beet,  potatoes,  beans,  vetches,  peas,  &c.)  during  the  germina- 
tion period,  and  the  dry  seeds  of  certain  lupins  contain  as  much  as  30  per 
cent.  The  constitution  of  asparagine  is  confirmed  by  the  various  syntheses 
leading  to  its  production. 

It  crystallises  with  1H20  in  Isevo-hemihedral,  trimetric  prisms,  soluble  in 
hot  water  but  insoluble  in  alcohol  or  ether. 

With  aqueous  cupric  acetate  solution,  it  forms  a  blue,  well-crystallised 
copper  salt  (C4H703N2)2Cu,  insoluble  in  water.  It  is  isomeric  with  malamide, 
from  which  is  differs  in  the  possession  of  both  acid  and  basic  characters.  It 
is  Isevo -rotatory  and  has  an  unpleasant,  insipid  taste,  but  vetch  seedlings 
contain  a  dextro-rotatory  asparagine  which  has  a  sweet  taste  (Piutti,  1886), 
but  does  not  unite  with  the  Isevo -rotatory  form — also  present  in  the  seedlings 
• — to  give  the  inactive  modification.  Pasteur  stated  that  the  substance 
composing  the  nerves  of  the  palate  behaves  as  an  optically  active  combination 
which  acts  differently  towards  the  dextro-  and  Isevo-  asparagines. 

Asparagine  is  converted  into  aspartic  acid  by  hydrolysis  and  into  malic 
acid  by  the  action  of  nitrous  acid. 

ASPART  AMIDE,  NH2-CO-CH2-CH(NH2)-CO-NH8,  is  the  diamide  or 
normal  amide  of  aspartic  acid. 

Numerous  higher  homologues  of  aspartic  acid  (Homo- Aspartic  Acids)  and 
of  asparagine  (Homo- Asparagines)  are  known. 

D.  AMIDO-  AND  IMIDO-CHLORIDES 

With  both  the  primary  amides  and  also  the  alkylated  amides,  the  oxygen  is  readily 
replaced  by  chlorine  by /the  action  of  PC16.  Thus,  acetamide  gives  acetamido-chloride, 
CH3-CC12-NH2,  and  ethylacetamide,  ethylacetamido-chloride,  CHS  •  CC12 '  NH  •  C2H6.  Both 
of  these  compounds  readily  lose  HC1,  forming  imino-chlorides,  e.g.  acetimino-chloride, 
CH3-CC1:NH,  and  ethylacetimino-chloride,  CH3-CC1 :  N-C2H6.  These  imino-chlorides, 
like  amido-chlorides,  are  readily  decomposed  by  water  into  hydrogen  chloride  and  amide. 
These  chlorinated  compounds  react  easily  with  aromatic  substances  and  with  hydrogen 
sulphide,  ammonia,  and  amines,  the  chlorine  being  thus  replaced  by  sulphur  or  by  amino- 
residues,  forming  thioamides,  e.g.  CH3-CS-NHX,  and  amidines,  e.g.  CH3-C(NH2) :  NX2. 

1  By  the  action  of  nitrons  acid  on  tho  ethyl  ester  of   glycocoll,  Curtius  obtained  Ethyl    Diazoacetate 

*\ 

II  yCH-COjCjHs,  as  a  yellow  oil  with  a  peculiar  odour;    when  heated  with  water  it  explodes,  losing  nitrogen 

N' 

and  taking  up  water  to  form  ethyl  glycollate. 


IMINOTHIOETHERS,    AMIDINES  357 

E.  THIOAMIDES 

These  are  well-crystallised  compounds,  more  acid  in  character  than  the  amides,  and 
hence  capable  of  forming  metallic  derivatives  and  of  dissolving  in  alkali.  Besides  by  the 
reaction  just  mentioned  they  are  obtained  by  the  addition  of  H2S  to  nitriles  : 
CH3-CN  +  H2S  =  CH3-CS-NH2  (thioacetamide  or  ethanethioamide)  ;  on  heating,  the 
opposite  change  occurs. 

Phosphorus  pentasulphide  replaces  the  oxygen  of  amides  by  sulphur,  thus  forming 
thioamides.  With  H2S,  isonitriles  give  the  alkylated  thioamides  of  formic  acid, 
CN-X  +  H2S  =  H-CS-NHX. 

Thioamides  are  readily  hydrolysed  (by  alkali,  hot  water,  &c.),  with  formation  of 
H2S,  NH3  (or  amine),  and  the  corresponding  acids  : 

X-CS-NHX'  +  2H20  =  X-C02H  +  NH2X'  +  H2S. 


F.  IMINOTHIOETHERS 

The  thioamides  (and  especially  their  derivatives)  can  exist  in  the  isomeric  or  tauto- 
meric  form,  X-C(SH) :  NH,  in  which  the  hydrogens  of  both  the  sulphydryl  and  the  imino- 
group  are  replaceable  by  alkyl  groups,  Iminothioethers,  e.g.  X-C(SX') :  NH,  being  then 
formed.  These  are  prepared  by  the  action  of  alkyl  iodides  on  the  thioamides  (ako  from 
thioalcohols,  nitriles,  and  gaseous  hydrogen  chloride),  e.g.  CH3-CS-NH2  +  CH3I  = 

/S-CH3 
CH3-C^  ,  HI  (acetiminothiomethyl  hydriodide). 

^NH 

The  iminothioethers  are  easily  hydrolysed  (by  HC1),  forming  ammonia  and  esters  of 
thio -acids  : 

yS-CH3 

CH3-(\  +  H2O  =  NH3  +  CH3-CO-SCH3. 

^NH 

G.  AMIDINES 

When  the  amides  or  alkylamides  are  heated  with  amines  in  presence  of  a  dehydrating 
agent  (like  PCl^),  the  oxygen  of  the  amide  is  substituted  by  an  imino-residue  : 

/NH2 
X-CO-NH2  +  R-NH2  =  H2O  +  X-C/ 

^NR 

/NHX' 
X-CO-NHX'  +  R-NH2  =  H2O  +  X-C/ 

XNR 

These  compounds  are  obtained  also  from  thioamides,  isothioamides,  iminochlorides, 
or  iminoethers  by  the  action  of  ammonia  or  of  primary  or  secondary  amines  : 

,NH 

CH3-CS-NH2  +  NH3  =  H2S  +  CH3-Cf          (acetamidine  or  ethanamidine). 

XNH2 

NH  ,NH 

+  R-NH2  =  X-C(  +  HSX'. 

SX'  \NHR 

When  nitriles  are  heated  with  the  hydrochlorides  of  primary  (of  the  aromatic  series 
also)  or  secondary  amines  (not  with  NH4C1),  alkylami dines  are  obtained  : 

CH3-CN  +  R-NH2  =  CH3-C(:  NH)-NHR. 

Properties.  The  amidines  (or  amimides)  are  bases  and  usually  of  the  aromatic  series  ; 
they  are  easily  hydrolysed  (by  boiling  with,  alkali  or  acid),  giving  (when  the  iminic  hydrogen 


358  ORGANIC    CHEMISTRY 

is  not  replaced  by  an  alkyl  group)  ammonia  (or  an  amine)  and  a  nitrile  ;  the  same  change 
occurs  on  dry  distillation.     With  H2S  they  give  first  an  additive  product  : 

/NHX'  ; 
X-C(:  NH)-NHX'  +  H2S  =  X-CSH 


this  product  then  decomposes  in  two  senses,  giving  (a)  X-CS-NHX'  +  NH3  and 
(6)X-CS.NH2  +  X'-NH2. 

With  CS2,  amidines  give  thioamides  and,  at  the  same  time,  thiocyanic  acid  or  an  alkyl 
thiocyanate. 

H.  HYDRAZIDES  AND  AZIDES 

Introduction  of  an  acid  residue  into  hydrazine,  H2N-NH2  (see  vol.  i,  p.  327),  gives  the 
primary  hydrazides  or  monoacylhydrazides,  e.g.  CH3-CO-NH-NH2  (acetylhydrazide)  and 
H-CO-NH-NH2  (formhydrazide,  m.pt.  54°)  ;  two  acid  radicals  give  secondary  hydrazides 
or  dihydrazides,  e.g.  CH3-CO-NH-NH-CO-CH3  (diacethydrazide,  which  melts  at  138° 
and  is  prepared  from  hydrazine  hydrate  and  acetic  anhydride). 

They  are  readily  hydrolysable,  and  reduce  ammoniacal  silver  nitrate  solution  in  the 
cold  and  Fehling's  solution  on  heating.  The  primary  hydrazides  are  more  highly  basic 
than  the  amides,  and  so  give  more  stable  salts.  Nitrous  acid  acts  on  primary  hydrazides, 
forming  azides,  which  are  derivatives  of  hydrazoic  acid  (see  vol.  i,  p,  327)  : 

/? 

CH3-CO.NH.NH2  +  HNO2  =  2H20  +  CH3-CO.N/  || 

\N 

These  resemble  the  acichlorides  in  many  properties,  but  are  explosive  and,  when  heated 
with  alcohol,  give  urethanes  and  liberate  nitrogen  : 

/N 

CH3-CON^  ||    +  C2HG-OH  =  N2  +  CH3-NH-CO,C2H6,  methylurethane, 

\N 

which  can  be  hydrolysed  with  formation  of  C02,  alcohol,  and  methylamine.  It  is  hence 
possible  to  pass  from  an  acid  to  an  amine  with  one  carbon  atom  less,  by  way  of  the 
hydrazide  and  azide. 

I.  HYDROXYLAMINE-DERIVATIVES  OF  ACIDS 

Hydroxylamine  or  its  residues  can  be  united  to  acid  residues,  forming  Hydroximic 
(or  hydroxamic)  Acids,  e.g.  CH3-C(:  N-OH)OH  (ethylhydroxamic  acid,  m.pt.  59°),  and 
Amidoximes,  X-C(:  N*OH)-NH2.  The  hydroxamic  acids  have  an  acid  character  and 
are  formed,  with  evolution  of  ammonia,  by  the  action  of  hydroxylamine  on  amides. 

Also  Formyloxime  Chloride,  CH(:  N-  OH)C1,  is  known,  this  being  obtained  by  treating 
mercury  fulminate  in  the  cold  with  HC1  ;  it  forms  needles,  which  are  readily  decom- 
posable, volatile,  and  soluble  in  ether. 

The  Amidoximes  are  formed  by  the  addition  of  nitriles  to  hydroxylamine, 
CH3CN  +  NH2-OH  =  CH3-C(:  NOH)NH2.  If  hydrogen  cyanide  is  employed,  ISURET 
(Methanamidoxime  or  Methenylamidoxime),  CH(:  NOH)NH2,  isomeric  with  urea, 
would  be  obtained. 

VI.  CYANOGEN  COMPOUNDS 

Some  cyanogen  compounds,  especially  Hydrocyanic  Acid,  HCN,  potassium 
cyanide,  and  ferro-  and  ferricyanides,  have  already  been  dealt  with  in  vol.  i, 
pp.  397,  437,  and  650.  We  have  to  consider  here  the  numerous  and  varied 
organic  derivatives  of  cyanogen,  which  are  of  some  interest  as  they  often 
exist  in  polymerised  forms  and  almost  always  in  two  isomeric  modifications, 
sharply  differentiated  by  their  chemical  properties  :  derivatives  of  nitriles, 
X  -C  :  N,  and  of  isonitriles,  C  ;N-X  (see  also  p.  199). 

CYANOGEN,  (CN)2,  is  a  highly  poisonous  gas  with  a  pungent  odour 
recalling  that  of  bitter  almonds  ;  it  is  liquid  at  —21°  and  solid  at  —34°.  It 


CYANOGEN    DERIVATIVES  359 

is  found  in  the  gas  from  blast-furnaces  and  occurs  largely  in  the  tail  of  Halley's 
comet,  which  approached  the  earth  in  May  1910.  It  is  obtained  by  the 
elimination  of  water  from  ammonium  oxalate  or  oxamide  (NHg-CO-CO-NHg), 
by  the  action  of  P205  in  the  hot,  or  by  heating  a  solution  of  copper  sulphate 
with  potassium  cyanide,  and  is  commonly  prepared  by  heating  cyanide  of 
silver  or  of  mercury,  Hg(CN)2  =  Hg  +  (CN)2 ;  as  a  secondary  product, 
PARACYANOGEN,  (C3N3)2,  or  (CN)X  is  formed  as  a  brown  powder. 

It  burns  with  a  purple  flame,  dissolves  readily  in  alcohol  or  water  (4  :  1), 
and  its  solutions  gradually  become  brown,  with  formation  of  oxalic  acid, 
formic  acid,  hydrocyanic  acid,  ammonia, and  urea,  and  deposition  of  Azulmic 
Acid  (brown  powder).  With  H2S  it  forms  the  thioamides  :  RUBEANHYDRIC 
ACID,  NH2-CS-CS-NH2,  and  FLAVEANHYDRIC  ACID,  NC-CS-NH2. 

CYANOGEN  CHLORIDE,  NC-C1,  is  of  importance  in  the  synthesis  of  many  cyanogen 
compound-!,  and  is  formed  by  the  action  of  chlorine  on  hydrocyanic  acid  or  metallic 
cyanides  :  NC-H  +  C12  =  HC1  +  NC-C1.  It  is  a  colourless  gas  which  is  easily  liquefied, 
boils  at  15-5°,  has  a  pungent  odour,  and  dissolves  in  water.  In  presence  of  HC1  it  poly- 
merises, forming  Cyanogen  Trichloride  (melts  at  145°,  boils  at  190°).  With  KOH  it 
forms  potassium  cyanato,  NOOK. 

CYANIC  ACID,  NC-OH,  is  a  liquid  of  penetrating  odour  and  only  slight  stability, 
even  at  the  ordinary  temperature. 

It  is  obtained  by  the  dry  distillation  of  cyanuric  acid  (q.v.)  and  condensation  of  the 
vapours  in  a  freezing  mixture.  It  undergoes  change,  even  at  the  ordinary  temperature 
and  with  slight  explosions,  into  a  compact,  white  isomeride,  which  is  polymerised  iso- 
cyanic,  acid  or  cyamelide  (O  :  C  :  NH)X  ;  this,  on  dry  distillation,  gives  cyanic  acid  again. 

Its  salts  are  more  stable,  but  when  attempts  are  made  to  liberate  the  acid  from  these 
by  the  action  of  mineral  acids,  immediate  hydrolysis  occurs  : 

NO- OH  +  H20  =  C02  +  NH3. 

If  it  is  liberated  by  dilute  acetic  acid,  the  isomeric  cyanuric  acid  is  obtained. 

The  alkyl  derivatives  of  cyanic  acid  exhibit  two  isomeric  forms  :  Cyanates,  N  :  C-OX, 
and  Isocyanates,  O  :  C  :  NX. 

Potassium  Cyanate,  NCOK,  forms  white  scales  soluble  in  alcohol  or  water,  and  is 
obtained  by  oxidising  solutions  of  potassium  cyanide  by  means  of  potassium  perman- 
ganate or  dichromate,  or  by  fusing  potassium  cyanide  or  ferrocyanide  with  Pb02  or  Mn02  : 
NCK  +  0  =  NCOK. 

Ammonium  Cyanate,  NO-  ONH4,  is  isomeric  with  urea,  into  which  it  can  be  converted. 
It  is  obtained  by  neutralising  cyanic  acid  with  ammonia  and  forms  a  moderately  stable, 
white,  crystalline  mass. 

ETHYL  ISOCYANATE,  CO  :  NC2H5,  is  prepared  by  distilling  potassium  cyanate 
with  either  potassium,  ethyl  sulphate,  or  ethyl  iodide.  It  is  a  liquid  of  penetrating  odour 
arid  boils  at  60°.  It  does  not  behave  as  a  true  ester  (true  esters  of  cyanic  acid 
do  not  exist),  since  the  action  of  acid  or  alkali  yields,  not  alcohol,  but  ethylamine  ; 
CO  :  NC2H5  +  H2O  =  C02  +  C2H5-NH2.  Hence  the  nitrogen  is  united  directly  to  the 
alkyl  group,  so  that  the  structure  is  not  N  :  C-OC2H5,  but  O  :  C  :  NC2H5. 

Ethyl  isocyanate  is  instantly  decomposed  by  water,  forming  derivatives  of  urea  ; 
the  latter  are  also  formed  by  the  action  of  ammonia  or  amino -bases. 

CYANURIC  ACID,  (NC)3(OH)3,  is  a  polymeride  of  cyanic  acid  and  on  heating  urea 
— which  contains  the  constituents  of  ammonia  and  cyanic  acid — either  alone  or  in  a 
current  of  chlorine  so  as  to  eliminate  the  elements  of  ammonia,  there  remain  those  of 
cyanic  acid,  which  polymerise  to  cyanuric  acid.  It  crystallises  with  2H20  in  prisms, 
effloresces  in  the  air,  and  is  readily  soluble  in  hot  water.  When  heated  with  HC1,  it 
hydrolyses  slowly  to  NH3  and  C02  ;  with  PC15  it  gives  the  chloride  of  cyanuric  acid. 
It  is  a  tribasic  acid  and  forms  a  violet,  crystalline  copper  salt  ;  its  sodium  salt  is  insoluble 
in  concentrated  alkalis.  Like  cyanic  acid,  it  gives  rise  to  two  series  of  derivatives,  e.g. 
Ethyl  Cyanurate,  (NC)3(OC2H5)3,  which  is  a  colourless  liquid  giving  alcohol  on  hydrolysis. 
It  is  only  slightly  stable,  and  is  readily  transformed  into  the  isomeride  of  the  other  series, 
Ethyl  Isocyanurate,  (CO)3(NC2H5)3,  which  is  formed  by  polymerisation  of  ethyl  isocyanate, 
or  by  distilling  the  cyanurate  with  potassium  ethyl  sulphate.  On  hydrolysis  it  gives 


360  ORGANIC    CHEMISTRY 

ethylamine,  this  confirming  its  constitution,  which  is  shown  by  the  following  closed-ring 
formulas  to  be  clearly  different  from  that  of  ethyl  cyanurate. 

O  OC2H6 


C2H5—  N         N—  C2H5  N 

II  II  I 

0:C          C:0  C2H50-C          C-OC2H5 


Ethyl  cyanurate 
C2H6 
Ethyl  isocyanurate 

FULMINIC  ACID,  C  :  NOH,  is  readily  volatile  but  unstable,  and  is  decomposed  by 
concentrated  hydrochloric  acid  into  hydroxylamine  and  formic  acid,  chloroformyloxime, 
GHClrN-OH,  being  formed  as  intermediate  product.  Kekule  regarded  fulminic  acid 
as  a  nitroacetonitrile,  N02'CH2-CN,  but  Nef  subsequently  attributed  to  it  the  consti- 
tution CrN-OH,  the  carbon  being  divalent.  With  bromine,  mercury  fulminate  (see 
p.  255)  gives  the  compound 

Br-C:N-0 


Br 


•C:N-0 


Silver  fulminate  is  even  more  explosive  than  the  mercury  salt. 

F.  C.  Palazzo  (1907-1910)  has  prepared  various  additive  products  of  fulminic  acid 
with  different  acids  (HBr,  HI,  HSCN,  HN02>  N3H).  With  hydrazoic  acid  at  -12°,  he 
obtained  two  isomerides  with  different  constitutions,  probably  with  intermediate  forma- 
tion of  Triazoformoxime : 

CH N— OH 

N3H  +  C :  NOH  -  5t  >C :  N-OH        — >         || 

3  N  •  N  :  N 

Triazoformoxime  N -hydroxytetrazole  (m  pt.  145°) 

The  other  isomeride  also  is  possibly  a  tetrazole  derivative. 

By  the  action  of  hydrogen  sulphide  on  mercury  fulminate  suspended  in  water,  L. 
Cambi  (1910)  obtained  and  isolated  the  Formothiohydroxamic  Acid  predicted  by  Nef  : 

H-C:NO-H 
H-S 

THIOCYANIC  ACID  AND  ITS  DERIVATIVES 

THIOCYANIC  ACID  (Rhodanic  Acid),  NC-SH,  is  a  yellow  liquid  of  penetrating 
odour,  stable  only  when  anhydrous  in  a  freezing  mixture  or  when  in  very  dilute  aqueous 
solution.  At  ordinary  temperatures  it  polymerises  to  a  yellow  mass.  It  is  obtained  from 
its  mercury  salt  (see  later)  by  the  action  of  hydrochloric  acid. 

In  concentrated  aqueous  solution,  it  undergoes  conversion  into  a  yellow  crystalline 
mass  of  Perthiocyanic  Acid,  (CN)2S3H2. 

Cyanogen  Sulphide,  (NC)2S,  may  be  regarded  as  a  kind  of  anhydride  of  thiocyanic 
acid,  and  is  obtained  from  silver  thiocyanate  and  cyanogen  iodide.  It  forms  colourless 
plates  which  have  a  pungent  odour  and  are  readily  soluble  in  water. 

Thiocyanuric  Acid,  (NC)3(SH)3,  is  polymeric  with  thiocyanic  acid,  and  is  obtained 
by  the  action  of  sodium  sulphide  on  cyanogen  chloride.  ^It  is  a  yellow  powder  and  gives 
salts  corresponding  with  a  tribasic  acid.  Its  trimethyl  salt  is  formed  by  polymerisation 
of  ethyl  thiocyanate  by  heating  at  180°. 

POTASSIUM  THIOCYANATE  (or  Rhodanate),  NC-SK,is  obtained  by  fusing  potas- 
sium cyanide  with  sulphur,  or  evaporating  a  solution  of  potassium  cyanide  and  yellow 
ammonium  sulphide,  or,  better  still,  by  fusing  potassium  ferrocyanide  with  potassium 


THIOCYANATES  361 

carbonate  and  sulphur  ;  as  prime  material  the  mass  used  for  the  purification  of  illumi- 
nating gas  is  nowadays  employed  (vol.  i,  p.  651).  It  forms  colourless  prisms  soluble  in 
boiling  alcohol  and  to  a  greater  extent  in  water  with  absorption  of  heat. 

AMMONIUM  THIOCYANATE  (or  Rhodanate),  NC-SNH4,  forms  colourless,  tabular 
crystals  soluble  in  alcohol,  and  readily  so  in  water.  It  is  obtained  by  heating  together 
CS2,  NH3,  and  alcohol  :  CSS  +  NH3  =  NOSH  +  H2S,  When  heated  it  is  transformed 
into  the  isomeric  thiourea.  It  serves  for  the  preparation  of  other  thiocyanates,  and  is 
extracted  in  large  quantities  from  the  exhausted  Laming  mixture  of  gasworks  (see 
p.  46),  which  contains  1  to  4  per  cent,  of  it. 

MERCURIC  THIOCYANATE,  (NC-S)2Hg,  is  prepared  from  a  mercuric  salt  and 
ammonium  thiocyanate,  and  forms  a  white,  insoluble  powder  which  swells  up  to  a  very 
considerable  extent  when  heated  (Pharaoh's  serpents). 

SILVER  THIOCYANATE  is  precipitated  as  a  white  mass  on  mixing  silver  nitrate 
and  ammonium  thiocyanate.  The  latter  gives,  with  ferric  salts,  a  dark  red  coloration 
of  FERRIC  THIOCYANATE  (sensitive  indicator  in  the  titration  of  silver  with  thio- 
cyanate) and  this,  with  potassium  thiocyanate,  gives  a  violet  double  salt,  (NOS)6FeK3. 

Hydrogen  sulphide  decomposes  the  thiocyanates,  NOSH  +  H2S  =  NH3  +  CS2, 
while  with  concentrated  sulphuric  acid,  addition  of  water  and  decomposition  into  ammonia 
and  carbon  oxysulphide  occur 

NOSH  +  HaO  =  COS  +  NH3. 


For  thiocyanic  acid  there  are  two  series  of  isomeric  derivatives,  corresponding  with 
the  two  general  formulae:  N  :  OSX  (alkyl  thiocyanate)  and  S  :  C  :  N-X  (mustard  oils). 

ETHYL  THIOCYANATE,  NC-SC2H5,  is  a  colourless  liquid  with  a  marked  odour  of 
garlic  ;  it  boils  at  142°  and  is  very  slightly  soluble  in  water.  It  is  formed  by  the  action 
of  cyanogen  chloride  on  mercaptides,  or  by  distillation  of  potassium  thiocyanate  with 
potassium  ethyl  sulphate.  As  it  has  the  constitution  of  a  true  ester,  it  is  hydrolysed 
by  alcoholic  potash  with  formation  of  alcohol  and  potassium  thiocyanate.  But  in  certain 
reactions  it  behaves  like  the  isomeric  mustard  oils.  Nascent  hydrogen  converts  it  into 
merceptan,  since  the  alkyl  is  united  to  sulphur,  and  the  action  of  nitric  acid  in  the  hot  yields 
ethylsulphonic  acid. 

ALLYL  THIOCYANATE,  NC-SC3H5,  boils  at  161°,  and  has  a  garlic-like  odour; 
it  undergoes  change  into  the  isomeric  mustard  oil,  slowly  at  the  ordinary  temperature 
and  more  rapidly  on  distillation. 

The  Mustard  Oils  (Isothiocyanates)  are  obtained  from  the  corresponding 
thiocyanates  simply  by  heating.  They  are  also  formed  by  the  action  of 
carbon  disulphide  on  the  corresponding  primary  amines,  CS2  +  X-NH2  = 
H2S  +  S  :  C  :  NX,  this  change  taking  place  by  way  of  the  intermediate 
alkylamine  salt  of  alkyldithiocarbamic  acid  (see  later),  which  is  distilled  with 
mercuric  chloride.  Mustard  oils  are  also  formed  when  an  alkylated  thiourea 
is  distilled  with  phosphoric  or  concentrated  hydrochloric  acid. 

Their  structure  is  indicated  by  their  formation  of  primary  amine  on  hydro- 
lysis :—  S  :  C  :  NX  +  2H20  =  C02  +  H2S  +  X-NH2.  The  isothiocyanic  acid, 
S  :  C  :  NH,  from  which  these  mustard  oils  are  regarded  as  derived,  is  not 
known  in  the  free  sta.te. 

METHYL  MUSTARD  OIL  (Methyl  Isothiocyanate),  SC  :  NCH3,  melting  at  34°  and 
boiling  at  119°  ;  Ethyl  Mustard  Oil,  SC  :  NC2H5,  boiling  at  134°  ;  and  Propyl  Mustard 
Oil,  SC  :  NC3H7,  boiling  at  153°,  are  of  little  importance.  More  interesting  is 

ALLYL  MUSTARD  OIL  (or  Ordinary  Mustard  Oil  ;  Allyl  Isothiocyanate), 
S  :  C  :  NC3H5,  which  is  prepared  by  distilling  Sinapis  nigra  (black  mustard)  with  water  ; 
it  is  obtained  synthetically  by  the  reactions  given  above.  It  is  a  liquid  with  a  pungent 
odour  recalling  that  of  mustard  and  raises  blisters  on  the  skin  ;  it  is  sparingly  soluble  in 
water  and  boils  at  150-7°. 


362  ORGANIC    CHEMISTRY 

CYANAMIDE  AND  ITS  DERIVATIVES 

CYANAMIDE,  NC-NH2,  is  a  white  crystalline  substance,  melting  at  40° 
and  dissolving  very  slightly  in  water,  alcohol,  or  ether.  It  is  obtained  by 
passing  a  current  of  cyanogen  chloride  into  an  ethereal  solution  of  ammonia  : 
2NH3  +  NOC1  =  NH4C1  +  NC-NH2.  It  is  also  formed  by  desulphurising 
thiourea,  NH2-CS-NH2,  by  means  of  HgO,  which  removes  H2S. 

It  is  obtained  abundantly  and  in  a  pure  state  by  extracting  calcium 
cyanamide  (see  later)  systematically  with  water,  neutralising  the  saturated 
solution  with  sulphuric  acid,  filtering  from  the  calcium  sulphate,  concen- 
trating in  a  vacuum,  again  filtering  from  the  gypsum,  concentrating  anew, 
and  extracting  the  crystalline  mass — formed  on  cooling— with  ether,  which 
does  not  dissolve  gypsum,  dicyanamide,  and  other  impurities.  Evaporation 
of  the  ether  yields  pure  cyanamide  in  almost  theoretical  yield  (Baum,  1910). 

With  lapse  of  time,  or  rapidly  at  150°,  cyanamide  changes  into  the  poly- 
meric dicyanodiamide  (see  later).  It  behaves  both  as  a  weak  base  forming 
unstable  crystalline  salts,  and  as  a  weak  acid  giving  metallic  salts,  e.g. 
NC-NHNa,  NONAg2,  &c.  The  most  important  of  these  is  calcium  cyan- 
amide,  NC-NCa,  which  was  considered  in  detail  in  vol.  i,  p.  309,  in  the  dis- 
cussion of  the  utilisation  of  atmospheric  nitrogen  ;  it  is  formed  by  the  action 
of  nitrogen  on  calcium  carbide  and  forms  an  excellent  nitrogenous  fertiliser. 

In  presence  of  dilute  acid,  cyanamide  fixes  a  molecule  of  water,  giving 
urea  :  NONH2  +  H20  =  NH2-CO-NH2  ;  with  hydrogen  sulphide  it  yields 
thiourea.  Cyanamide  also  gives  two  series  of  isomeric  alkyl  derivatives  of 
the  general  formulae  N  :  C*NX2  and  XN  :  C  :  NX.  Compounds  of  the  latter 
formula  are  derived  from  the  hypothetical  carbodi-imide,  NH  :  C  :  NH  ;  for 
example,  carbodiphenylimide,  C6H5N :  C :  NC6H5,  boiling  at  330°,  is  well 
characterised. 

DIETHYLCY  AN  AMIDE,  NC-N(C2H5)2,  is  formed  by  the  action  of  ethyl  iodide 
on  the  silver  salt  of  cyanamide,  its  structure  being  indicated  by  the  products — 
C02  +  NH3  +  NH(C2H5)2 — obtained  on  hydrolysis  with  dilute  acid.  Methyl-  and 
ethyl-cyanamide  are  also  known. 

DICYANODIAMIDE,  (NC-NH2)2,  is  formed,  as  has  already  been  mentioned,  from 

NH 
cyanamide  ;  certain  of  its  reactions  indicate  the  structure  NC-NH-C^  (Bamberger). 

XNH2 

It  forms  acicular  crystals  or  small  flat  prisms.  When  heated  strongly  and  rapidly,  it  is 
converted  into  a  white  insoluble  powder,  MELAM,  C6H9Nn  or  [(NC)3(NH2)2]2NH,  this 
being  an  imide  of  melamine,  into  which  it  is  transformed  by  sulphuric  acid  or  ammonia. 

MELAMINE  (Cyanurtriamide),  (NC)3(NH2)3,  is  a  crystalline  basic  substance,  insoluble 
in  alcohol  or  ether.  When  it  is  boiled  with  acid,  the  amino-groups  are  gradually  replaced 
by  hydroxyl  groups,  giving  AMMELINE,  (NC)3(NH2)2OH,  then  AMMELIDE, 
(NC)3NH2(OH)2,  and  finally  Cyanuric  Acid,  (NC)3(OH)3. 

As  usual,  the  alkyl  derivatives  form  two  isomeric  series,  derivatives  being  known 
of  a  hypothetical  Isomelamine,  (CNH)3(NH)3,  among  these  being  the  polymerised 
alkylcyanamides. 

VII.  DERIVATIVES  OF  CARBONIC  ACID 

True  carbonic  acid,  0  :  C(OH)2,  is  not  knowjn  in  the  free  state,  since  two 
hydroxyl  groups  cannot  exist  in  combination  with  the  same  carbon  atom 
(see  p.  182),  but  it  is'supposed  to  exist  in  aqueous  solution,  and  salts  corre- 
sponding with  this  formula  are  stable  and  well  known  (carbonates  and  bicar- 
bonatesj.  Also  important  organic  derivatives,  similar  to  those  already  studied 
for  other  dibasic  acids  (amides,  chlorides,  esters,  &c.),  are  known.  The  acid 
derivatives  are  less  stable  than  the  normal  ones. 


CARBONIC    ACID    DERIVATIVES  363 

ESTERS  OF  CARBONIC  ACID 

ETHYL  CARBONATE,  CO(OC2H6)2,  is  a  liquid  which  is  insoluble  in  water,  boils  at 
126°,  and  has  a  pleasant  odour.  It  is  formedjby  the  interaction  of  ethyl  chlorocarbonate 
and  alcohol:  C2H5-OH  +  C1-CO-OC2H5  =  HC1  +  CO(OC2H5)2,  and  also  from  silver 
carbonate  and  ethyl  iodide.  Mixed  esters,  containing  different  alkyls,  also  exist. 

ETHYLCARBONIC  ACID,  CO(OH)-OC2H5,  is  known  only  as  salts,  e.g.  Potassium 
Ethylcarbonate,  CO(OK)-OC2H5,  which  is  obtained  by  the  action  of  CO2  on  an  alcoholic 
solution  of  potassium  ethoxide  and  forms  shining  scales,  giving  alcohol  and  potassium 
carbonate  when  treated  with  water. 

CHLORIDES  OF  CARBONIC  ACID 

Carbon  Oxychloride  (phosgene) ,  COC12,  has  already  been  described  (vol.  i,  p.  394). 

CHLOROCARBONIC  ACID,  COC1-OH,  is  the  acid  chloride  of  carbonic  acid,  but 
is  not  stable  and,  when  liberated,  decomposes  into  CO2  and  HO.  Its  esters  are,  however, 
well  known,  the  action  of  phosgene  on  absolute  alcohol  giving,  for  example,  ethyl  chloro- 
carbonate (Ethyl  Chloroformate),  C1-CO-OC2H5,  thus:  C2H5-OH  +  COC12  =  HC1  + 
C1-CO-OC2H5. 

This  ester  is  a  liquid,  having  a  pungent  odour,  boiling  at  93°  and  readily  decomposing 
under  the  action  of  water  ;  it  is  used  largely  in  organic  syntheses  to  introduce  carboxyl 
into  the  molecule. 

AMIDES  OF  CARBONIC  ACID 

The  acid  amide,  NH2  •  CO  •  OH,  is  Carbamic  Acid,  and  the  normal  amide,  NH2  •  CO  •  NH2, 
urea. 

CARBAMIC  or  CARBAMINIC  ACID,  NH2-CO-OH,  is  obtained  as  ammonium  salt 
— ammonium  carbamate,  NH2-CO-ONH4 — by  the  direct  union  of  dry  CO2  and  NH3  ; 
a  white  mass  is  thus  obtained  which,  even  at  60°,  dissociates  into  C02  +  NH3.  In  aqueous 
solution  this  salt  does  not  precipitate  solutions  of  calcium  salts  at  the  ordinary  tem- 
perature, since  calcium  carbamate  is  soluble,  but  in  the  hot  the  salt  decomposes  into 
C02  and  NH3  and  gives  a  precipitate  of  calcium  carbonate. 

Ethyl  carbamate  or  URETHANE,  NH2-CO-OC2H5,  is  also  well  known  and  is  obtained 
by  the  action  of  ammonia  or  ethyl  carbonate,  CO(OC2H5)2  +  NH3  =  C2H5-OH  + 
NH2-CO-OC2H5>  or,  more  easily,  by  treating  ethyl  chlorocarbonate  with  ammonia: 

COC1(OC2H5)  +  2NH3  =  NH4C1  +  NH2  •  CO  •  OC2H6. 

It  melts  at  48°  to  50°,  is  soluble  in  water,  and  is  used  as  a  soporific.  t 

The  following  are  also  known:  iodourethane,  NHI •  CO •  OC2H5  ;  ethylurethane, 
NHC2H5-CO-OC2H5  (boils  at  175°);  nitrourethane,  N02  •  NH •  CO  •  OC2H5  ;  carbamidyl 
chloride,  NH2-CO-C1  (melts  at  50°  and  boils  at  61°)  ;  and  diethyl  iminodicarfamate, 
NH(CO-OC2H5)2,  which  is  the  imide  of  urethane. 

Urethane  derivatives  are  readily  hydrolysable  with  alkalis  and  yield  ammonia  and 
urea  when  heated. 

UREA  (Carbamide),  CO(NH2)2,  is  the  final  oxidation  product  of  nitrogenous  com- 
pounds in  the  living  organism,  and  the  adult  human  being  produces  about  30  grms.  of 
it  a  day  ;  it  is  found  in  general  in  the  urine  of  carnivora  (where  it  was  first  discovered) 
and  in  other  animal  fluids.  It  crystallises  in  shining  needles  soluble  in  water  and  in 
alcohol,  but  insoluble  in  ether  ;  it  melts  at  132°  and  sublimes  in  a  vacuum.  It  is  formed 
from  ammonium  cyanate  by  simple  rearrangement  under  the  action  of  heat  (Wohler) : 
NC-ONH4  =  CO(NH2)2.  Escales  (1911)  found  that  when  urea  is  distilled  or  sublimed 
in  a  vacuum,  the  reverse  reaction,  i.e.  formation  of  ammonium  cyanate,  occurs.  Urea 
is  also  obtained  by  the  action  of  ammonia  on  ethyl  carbonate  or  carbamic  acid  : 

CO(OC2H5)2  +  2NH3  =  2C2H5-OH  +  CO(NH2)2. 

Many  other  reactions  give  urea,  e.g.  oxidation  of  thiourea,  action  of  water  on  cyanamide, 
&c.,  but  in  the  laboratory  it  is  prepared  by  treating  with  barium  carbonate  the  urea 
nitrate  obtained  by  evaporating  urine  in  presence  of  nitric  acid,  or  by  heating  ammonium 
sulphate  solution  with  potassium  ferrocyanide  or  cyanate  : 

(NH4)2S04  +  2NCOK  =  K2S04  +  2CO(NH2)2. 


364 


ORGANIC    CHEMISTRY 


When  heated  it  is  decomposed  into  ammonia,  biuret  (see  later),  cyanuric  acid, 
and  ammelide.  It  is  readily  hydrolysed  by  acids,  alkalis,  or  even  hot  water  : 
CO(NH2)2  +  H2O  =  C02  +  2NH3,  and  is  decomposed  by  nitrous  acid  or  sodium  hypo- 
chlorite  : 

2HNO2  +  CO(NH2)2  =  3H2O  +  C02  +  2N2. 


It  exhibits  the  properties  of  a  base  and  of  a  weak  acid,  giving  salts  with  acids  (e.g. 
Urea  Nitrate,  CO(NH2)2,  HNO3,  which  is  soluble  in  water  and  slightly  so  in  nitric  acid, 
and  with  concentrated  sulphuric  acid  gives  the  highly  acid  Nitrourea,  NH2-CO-NH-NO2), 
and  with  bases,  e.g.  CO(NH2)2, 2HgO.  It  also  crystallises  with  other  salts,  e.g.  CO(NH2)2  + 
NaCl  +  H20,  CO(NH2)2  +  AgN03,  &c.  Mercuric  nitrate  precipitates  urea  quantita- 
tively from  its  neutral  aqueous  solutions  as  2CO(NH2)2  +  Hg(N03)2  +  3HgO. 

Urea  forms  various  alkyl  derivatives  ;  thus  ethyl  cyanate  and  ethylamine  give  symm. 
or  vL-diethylurea,  which  is  isomeric  with  unsymm.  or  /3-diethylurea,  NH2-CO-N(C2H5;?  : 
CO-NC2H5  +  C2H6-NH2  =  CO(NHC2H6)2.  The  constitutions  of  these  alkyl  derivatives 
are  determined  by  study  of  the  products  of  their  hydrolysis. 

"M'TT 

Readily  hydrolysable  alkylisoureas,  NH  :  C<^rvV25  are  also  known. 

O-A. 

SEMICARBAZIDE,  NH2-CONH'NH2,  which  is  obtained  from  potasdum  cyanale 
and  hydrazine  hydrate,  may  also  be  regarded  as  a  derivative  of  urea.  It  has  already 
been  seen  that  this  base  (which  melts  at  96°)  gives  crystalline  compounds  (semicarbazones) 
with  ketones  and  aldehydes  (seep.  206).  CARBAZIDE  (Carbohydrazide) ,  CO(NH-NH2)2, 
melts  at  152°,  and  is  obtained  from  esters  of  carbonic  acid  by  the  action  of  hydrazine 
hydrate. 

Acetylurea,  NH2-CONH  CO-CH3,  and  Allophanic  Acid,  NH2 •  CO •  NH •  C02H  (not 
known  free,  but  as  salts),  are  obtained  from  acid  chlorides  and  urea. 

The  formation  of  ureides  (compounds  of  urea  and  mono-  and  dibasic  acids)  takes 
place  with  monobasic  divalent  acids  or  with  an  alcohol  and  acid.  Such  a  reaction  gives 
Hydantoic  Acid  (glycoluric  acid),  NH2-CO-NH-CH2-CO2H,  which,  when  evaporated  in 

.NH-CO 
presence  of  HC1,  loses  water  and  forms  Hydantoin,  C0<^  |      ,  the  latter  giving  first 

\NH-CH2 
hydantoic  acid  and  then  C02,  NH3,  and  glycine  on  hydrolysis. 

When  urea  is  heated  at   160°,  2   mols.   condense  with  separation  of  ammonia  and 

yCO-NH2 
formation  of  Biuret,  NH<^  |       ,  which  crystallises  with  1H2O  and  is  soluble  in  water 

XCO-NH2 

or  alcohol  ;   in  alkaline  solution  it  gives   a   characteristic  violet   coloration  with  a  little 
copper  sulphate. 

DERIVATIVES  OF  THIOCARBONIC  ACID 

More  or  less  complete  substitution  of  the  oxygen  of  carbonic  acid  by 
sulphur  gives  a  series  of  unstable  compounds,  which  form  stable  alkyl  deriva- 
tives and  exhibit  various  cases  of  isomerism  indicated  by  varying  products 
of  hydrolysis.  These  numerous  sulphur  compounds  are  reducible  to  three 
types,  according  as  they  contain  (1)  the  nucleus  SC<C,  thiocarbonic  or  thio- 
carbamic  compounds,  (2)  the  nucleus  OC<C,  carbonyl  or  carbamic  compounds, 
or  (3)  the  group  H-N  :  C<C,  iminocarbonic  or  iminocarbamic  compounds. 

The  following  are  the  principal  compounds  of  these  types,  which  have  been  thoroughly 
studied  in  the  form  of  their  alkyl  derivatives  : 


Trithiocarbonic  acid 
Dithiocarbonic  acid 

Monothiocarbonic  acid 
Dithiocarbamic  acid 


.     SC(SH)2 


OH 

NH2 

SH 


Monothiocarbamic  acid     . 

Thiocarbamide 
Thiophosgene 
Thiocarbamidyl  chloride  . 


.  SC< 


NH2 


SC  : 


G  U  A  N  I  D  I  N  E  365 


Dithiocarbonylic  acid        .          .     CO(SH)2 

OTT 

Monothiocarbonylic  acid  . 
Monothiocarbonylamic  acid 


NH2 


Iminodithiocarbonic  acid          HN  :  C(SH)2 


Iminomonothiocarbonic  acid 


CTT    , 

~TT« 

Iminothiocarbamic  acid    .      HN:C<TriTT2 

oxl 


THIOPHOSGENE  (Carbon  Sulphochloride),  SCC12,  is  a  red  liquid  which  fumes  in  the 
air,  attacks  the  mucous  membrane,  and  boils  at  68°  to  74°.  It  is  prepared  by  the  action 
of  chlorine  on  carbon  disulphide,  the  intermediate  compound,  CC13'SC1,  thus  obtained 
being  reduced  with  stannous  chloride.  It  is  more  stable  towards  water  than  phosgene, 
and  with  ammonia  gives,  not  thiourea,  but  ammonium  thiocyanate. 

TRITHIOCARBONIC  ACID,  CS3H2,  is  obtained  as  sodium  salt  by  the  action  of 
carbon  disulphide  on  sodium  sulphide.  The  free  acid  is  a  brown  unstable  oil  and  its 
ethyl  ester,  SC(SC2H5)2,  a  liquid  boiling  at  240°. 

POTASSIUM  XANTHATE,  KS-SC-OC2H5,  is  the  ether  of  the  potassium  salt  of 
dithiocarbonic  acid.  It  is  formed  by  the  action  of  CS2  on  C2H5-OK  and  crystallises  in 
shining  needles  soluble  in  water  and  to  a  less  extent  in  alcohol.  With  copper  sulphate  it 
gives  copper  xanthate  as  an  unstable  yellow  powder  which  is  used  in  indigo  printing. 

XANTHIC  or  XANTHONIC  ACID,  HS-SC-OC2H6,  is  liberated  from  its  potassium 
salt  (see  above)  and  forms  an  oil  insoluble  in  water  ;  it  readily  decomposes  into 
C2H5-OH  +  CS2. 

DITHIOCARBAMIC  ACID,  NH2-SC-SH,  is  obtained  as  ammonium  salt  by  the 
action  of  ammonia  on  an  alcoholic  solution  of  CS2  : 

2NH3  +  CS2  =  NH2-SOSNH4. 

In  the  frea  state  this  acid  forms  an  unstable,  reddish  oil  (decomposing  into  SH2  + 
thiocyanic  acid)  and  its  ethyl  ester,  NH2-SOSC2H5,  is  dithiourethane,  whilst  thiourethane 
will  bo  NH2-CO-SC2H6  and  is  isomeric  with  xanthogenamide,  NH2-CS-OC2H5. 

Ethylamine  Ethyldithiocarbamate,  C2H6-NH-SOSH,  NH2-C2H5,  is  formed  similarly 
by  the  action  of  carbon  disulphide  on  ethylamine  ;  in  the  hot  it  gives  diethylthiourea, 
SC(NHC2H5)2,  the  mercuric  salt  of  which  gives  the  corresponding  mustard  oil  with  water 
in  the  hot,  whilst  the  alkylated  dithiocarbamic  acids  obtained  with  secondary  amines 
do  not  give  mustard  oils  under  these  conditions. 

THIOC  ARE  AMIDE  (Thiourea),  SC(NH2)2>  is  only  partly  obtained  on  heating 
ammonium  thiocyanate  at  130°,  the  reaction  being  reversible.  It  forms  crystals  melting 
at  172°,  and  dissolving  in  water  and  in  alcohol,  giving  neutral  solutions  ;  it  has  a  bitter 
taste.  On  hydrolysis  it  yields  C02  +  H2S  +  NH3.  As  has  already  been  stated,  it  is 
converted  into  urea  by  permanganate,  cyanamide  by  mercuric  oxide,  and  potassium 
thiocyanate  and  ammonia  by  alcoholic  potash  at  100°.  It  behaves  as  a  weak  acid  and  a 
weak  base,  and  its  derivatives,  in  some  cases,  correspond  with  the  tautomeric  formula, 


oTT  2  (hypothetical  iminothiocarbamic  acid). 

About  10,000  kilos  of  thiourea  are  produced  annually  by  two  factories,  one  French 
and  the  other  German,  for  preserving  loaded  silk  from  corrosion,  the  Gianoli  process 
(see  later,  under  Silk)  being  used.  Owing  to  this,  the  price  of  thiourea  has  been  lowered 
from  £2  to  5s.  6d.  or  6s.  6d.  per  kilo. 

Acetylthiourea,  Sulphohydantoin,  &c.  are  also  known. 


GUANIDINE  AND  ITS  DERIVATIVES 
GUANIDINE    (Iminourea    or    Iminocarbamide),     NH  :  C<^jj2     forms 

crystals  readily  soluble  in  water  or  alcohol.  It  is  a  strong  base,  absorbing 
carbon  dioxide  from  the  air,  but  is  converted  into  salts  by  one  equivalent 
of  acid.  The  fatty  acid  salts  are  converted  on  heating  into  guanamines, 
which  form  crystals  of  peculiar  shape. 

It     is     obtained     by     heating     cyanamide     with     ammonium     iodide  : 


366  ORGANIC    CHEMISTRY 

NH4I  +  CN-NH2  =  NH  :  C(NH2)2,  HI  ;  or,  better,  as  thiocyanate  by  heating 
thiourea  with  ammonium  thiocyanate  at  190°  : 

NCS-NH4  +  SC(NH2)2  =  H2S  +  NH  :  C(NH2)2,  NC-SH. 

It  may  also  be  obtained  from  dicyanodiamide  by  the  action  of  aqua  regia 
(C.  Ulpiani,  1907). 

Guanidine  is  readily  hydrolysed,  forming  first  ammonia  and  urea  and 
then  C02  and  NH3. 

Guanidine  Nitrate,  NH  :  C(NH2)2,  HN03,  is  converted  by  concentrated  sulphuric 
acid  into  nitroguanidine,  NH  :  C(NH2)(NH-NO2),  and  this,  on  reduction,  gives  amino- 
guanidine,  NH  :  C(NH2)(NH-NH2).  The  latter  gives  hydrazine,  (NH2)2,  NH3,  and  CO2 
011  hydrolysis  with  acid  or  alkali,  whilst  with  nitrous  acid  it  yields  Diazoguanidine 
(iminocarbamideazide),  NH  :  C(NH2)-N3,  which  is  resolved  by  alkali  into  hydrazoic  acid 
(see  vol.  i,  p.  327)  and  cyanamide. 

From  aminoguanidine  can  be  obtained  Azodicarbonamide,  NH2-CO-N  :  N-CONH2, 
and  Hydrazodicarbonamide,  NH2-CONH-NH-CONH2. 

GLYCOCYAMINE,  NH  :  C(NH2)-NH-CH2-CO2H,  is  formed  by  the  union  of  glycocoll 

.NH-CO 
with  cyanamide,  and  if  water  is  lost  Glycocyamidine,  NH  :  C<^  |       ,  is  obtained.     If 

XNH-CH2 

however,  instead  of  glycocoll,  its  methyl  -derivative  is  taken,  sarcosine,  CO2H-CH2- 
NH-CH3  (melts  at  115°  and  is  neutral),  results,  creatine  and  creatinine  being  obtained 
similarly. 

CREATINE,  NH  :  C(NH2)-N(CH3)-CH2-CO2H,  is  obtained  from  meat-extract,  being 
a  stable  component  of  muscle.  It  has  a  neutral  reaction  and  is  soluble  in  water  and 
sparingly  so  in  alcohol  ;  it  crystallises  with  1H2O,  has  a  bitter  taste  and,  when  heated 
with  acid,  loses  1  mol.  of  water  of  constitution  and  forms  creatinine  ;  on  complete 
hydrolysis,  it  gives  urea  and  sarcosine. 

NH  --  CO 
CREATININE,    NH  :  C\  j     is  a  weak  base  and    dissolves  very  readily  in 

XN(CH3)-CH2 

water,  giving  creatine  again.  It  is  one  of  the  constituents  of  urine  and  forms  a 
characteristic  zinc  salt,  2  mols.  of  creatinine  combining  with  1  mol.  of  ZnCl2.  When 
hydrolyscd,  it  gives  ammonia  and  methylhydantoin. 

URIC  ACID  AND  ITS  DERIVATIVES 

When  the  two  amino  -groups  of  urea  condense  with  the  two  carboxyl 
groups  of  a  dibasic  acid  with  expulsion  of  2  mols.  of  water,  ureides  (see  above) 

xNH-CO 
are    obtained.       Thus    oxalic    acid    yields     parabanic    acid,    C0<f  |    ; 

XNH-CO 
WIT  •  f^O 
malonic  acid,  barbituric  acid,  CO<NH-  CO>CH2  ;    tartroriic  acid,  dialluric 


- 
acid,  and  mesoxalic  acid,  alloxan,  C0<™/  CO>CO.      If,  however,  only  one 

molecule  of  water  is  eliminated,  one  amino-  and  one  carboxyl-group  remaining 
unchanged,  uroacids  are  obtained,  e.g.  oxaluric  acid,  NH2-CONH-CO-C02H, 
and  alloxanic  acid  (from  mesoxalic  acid). 

These  ureides  are  usually  well  crystallised,  and  are  aminic  and  also 
markedly  acid  in  character.  On  hydrolysis,  they  give  first  the  corresponding 
uroacid  and  then  urea  and  free  acid.  They  are  sometimes  formed  on  oxida- 
tion of  diureides  (see  below)  ;  thus  parabanic  acid  is  obtained  by  oxidising 
uric  acid  with  nitric  acid.  The  alcohol-acids  and  the  aldehydo-acids  also 
give  such  condensations  (see  above),  yielding,  for  example,  Jiydantoin,  Tiydantoic 
acid,  and  allanturic  acid  (from  glyoxylic  acid). 


THEURICACIDGROUP  367 

When  2   raols.    of   urea   take   part  in  the   condensation,   diureides  are 
obtained,  these  forming  the  uric  acid  group  [ 


(5)  C—  NIL 

|  ||  )CO  (8) 

(3)  NH  --  C—  NHX 

(4)        O) 

and  its  derivatives  :  xanthine,  caffeine,  theobromine,  guanine,  hypoxanthine, 
alloxanthine,  purpuric  acid,  allantoin,  &c.  The  positions  of  the  substituent 
groups  are  indicated  by  the  bracketed  numbers  shown  in  the  above  formula  for 
uric  acid.  During  recent  years  successful  attempts  have  been  made,  by  means 
of  ethyl  cyanoacetate,  to  synthesise  all  these  xanthine  bases  and  to  convert 
them,  one  into  the  other  (see  Berichte  der  deutsch.  chem.  Gesells.,  1899,  32, 
p.  435). 

As  a  general  rule,  the  ureides  and  diureides  have  a  more  or  less  marked 
acid  character  and,  as  they  contain  no  carboxyl  group,  this  acidity  is  explained 
as  due  to  the  existence  of  these  compounds  in  tautomeric  forms,  just  as  is 

CH2—  C(k 
the  case  with  succinimide,  \  /NH.     In  the  latter,  it  is  assumed  that 

CH2—  CCT 

the  iminic  hydrogen  atom  is  very  mobile  and  undergoes  displacement  and 
union  with  the  oxygen  of  the  neighbouring  carbonyl  group,  a  double  linking 
between  carbon  and  nitrogen  being  formed  and  an  acid  hydroxyl  group 
capable  of  forming  salts  with  metals.  The  tautomeric  formula  of  Succinimide 

OH2-C(OHk  /N:OOH 

would  hence  be    |  /N,  and  that  of  Parabanic  Acid  C0\         I 

CH2  --  COT  NN:C-OH 

similar  formula?  hold  for  uric  acid  and  barbituric  acid,  the  latter  functioning 
as  a  dibasic  acid  (in  this  case,  however,  the  acid  character  is  perhaps  to  be 
attributed  to  the  hydrogen  of  the  methylene  group,  CH2). 

Several  diureides  are  found  in  nature,  e.g.  in  guano,  in  the  urine  and 
muscles  of  carnivora,  in  the  excreta  of  serpents,  in  articular  concretions,  and 
in  certain  plants  (theobromine  in  cocoa,  caffeine,  &c). 

The  constitutional  formulae  of  the  more  important  diureides  are  as  follow  : 


N(CH8)-CO  /NH 

C0<  I  C0(  >CH       0<  | 

\N(CHe)-CO  \NH-    —CO/  C<CO-NH>CO 

Dimethylparabanic  acid  Methyluracyl  Alloxanthine 

(cholestrophane) 

~  NH—  CH—  NIL 


CQ  -  c 

—  NH  \  / 

XNH2   CO—  NH/ 


Murexlde  Allantoin 

N  —  C  —  N    v  N  —  C  —  N   . 

II     II        >o  II     II        >ci 

CH    C  —  NH/  CC1   C  —  NH/ 

N  =  CH  N  =  CC1 

Purine  Trichloropurinc! 


368  ORGANIC    CHEMISTRY 

CH3-N  —  CO  CH3-N  — C— Nv 

II  I        II  >CH 

CO    CH-NH-CO-NH2  CO    C  — NH/ 

II  II 

CH3-N-CO  CH3-N-CO 

Dimethylpscudouric  acid  Theophylline 

CH3-N-C  — N.  N C Nv  NH-C  — N. 

I        II  >H  ||          ||  )CH  |  ||  \CH 

CO    C— NfCH.,)/  CH      C  —  NH/  CO       C  —  NH/ 

CH3-N  — CO  NH— CO  NH  — CO 

Caffeine  Hypoxanthine  Xanthine 

N  — C  —  Nv  NH  — C  —  N. 

II        II  >H  |  ||  >CH 

CH    C  — NH/  NH:C         C  — NH/ 

N=C-NH2  .  NH  — CO 

Adenine  Guanine 

URIC  ACID,  C5H403N4.  Syntheses  of  uric  acid  are  many  and  various  ;  from  cyano- 
acetic  acid,  or  glycocoll  or  isodialuric  acid,  by  heating  with  urea  ;  from  aminobarbituric 
acid  and  potassium  cyanate  ;  from  ethyl  acetoacetate  and  urea,  passing  through  methyl- 
uracyl,  nitrouracyl,  hydroxyuracyl,  and  isodialuric  acid.  The  following  scheme  represents 
the  various  steps  of  the  synthesis  from  malonic  acid  :  * 

NH2  CO- OH  NH  — CO  NH  —  CO 

CO         +        CH2         — >        CO         CH2       — >        CO         C-.N-OH  — > 

I  I  I  I    '  II 

NH2  CO -OH  NH  —  CO  NH  —  CO 

Urea  Malonic  acid  Barbituric  acid  Violuric  acid 

NH  —  OC  NH  —  CO  NH  —  CO 

II  II  II 

CO         CH-NH2      — >     CO         CH  —  NHX       — >        CO         C  —  NHV 

II  II  >o  |         ||          >co 

NH  —  CO  NH  —  CO       NH2/  NH  —  C  —  NH/ 

Uramil  Pseudouric  acid  Uric  acid 

Uric  acid  is  a  feeble  dibasic  acid  (see  above),  and  forms  a  white,  amorphous  substance 
insoluble  in  alcohol  or  ether  and  almost  insoluble  in  water.  It  dissolves,  however,  in 
concentrated  sulphuric  acid,  from  which  it  separates  unchanged  on  dilution  with  water. 
It  is  extracted  from  guano,  the  excrements  of  serpents,  and  the  urine  of  carnivora. 

Evaporation  of  uric  acid  with  dilute  nitric  acid  and  treatment  of  the  residue  with 
ammonia  yields  murexide,  which  forms  yellowish  green  crystals  which  give  a  purple 
aqueous  solution,  turning  blue  on  addition  of  alkali  (characteristic  reaction  for  uric  acid). 

THEOBROMINE  (3  :  7-Dimethyl-2  :  6-dioxypurine),  C7H8O2N4  or 

CH3-N  —  C Nv 

I  II  ^TTT 

II  /CH' 

CO      C  —  N(CH3)/ 

NH— CO 

is  extracted  from  cocoa,2  and  forms  white,  bitter-tasting  crystals,  slightly  soluble  in  water 

1  The  constitution  ofwic  add  was  demonstrated  first  by  Medicus,  ajid  later,  by  various  syntheses,  by  E  Fischer 
(Liebig's  Annalen,  1882,  215,  p.  253).  The  presence  of  a  chain,  — C — C — C — ,  and  of  a  carbonic  acid  residue 
is  shown  by  the  formation  of  urea  and  alloxan  when  uric  acid  is  treated  in  the  cold  with  nitric  acid.  The  presence 
ot  four  imino-groups  is  deduced  from  the  fact  that,  by  introduction  of  four  methyl  groups  and  subsequent  hydro- 
lysis, the  four  atoms  of  nitrogen  are  eliminated  as  methylamine.  A  large  part  of  the  uric  acid  molecule  is  rendered 
evident  by  the  formation  of  allantoin  (of  known  constitution)  on  oxidation  with  alkaline  permanganate,  and  by 
the  formation  of  methylurea  and  methylalloxan  on  oxidation  of  dimethyluric  acid. 

*  Cocoa  and  Chocolate.  Cocoa  is  placed  on  the  market  in  the  form  of  large  violet  seeds  of  Theobroma  cacao, 
which  grows  well  in  the  Antilles.  Mexico,  Guatemala,  Java,  Borneo,  Esmerelda  (equator),  &c.  The  red  or  brown 


ESTERS  369 

or  alcohol.  It  behaves  as  a  weak  acid  and  a  weak  base.  With  methyl  iodide,  the  silver 
salt  yields  caffeine. 

CAFFEINE,1  C8H1002N4  +  H2O  (constitution  given  above),  is  identical  with  theine  2  ; 
it  forms  shining  nredles  which  readily  sublime,  are  sparingly  soluble  in  alcohol  and  in 
water,  and  have  a  rather  bitter  taste.  Synthetically  it  is  obtained,  for  example,  from 
ethyl  cyanoacetate  or  malonic  acid  and  dimethylurea. 

GUANINE,  C5H5ON5  (constitution  given  above),  is  a  di-acid  base,  but  forms  salts 
also  with  bases.  It  is  a  white  powder  insoluble  in  water  but  soluble  in  ammonia.  On 
oxidation  with  potassium  chlorate  and  hydrochloric  acid,  it  gives  carbon  dioxide,  para- 
banic  acid,  and  guanidine. 

XANTHINE,  C6H4O2N4  (constitution  given  above),  is  a  white  powder  and  acts  as 
both  acid  and  base.  It  is  obtained  from  guanine  by  the  action  of  nitrous  acid,  and  its 
lead  salt  reacts  with  methyl  iodide,  giving  theobromine. 

ADENINE,  C6H5N6  (constitution  given  above),  forms  shining  needles  and  is  a  base 
occurring  in  tea  and  in  ox-pancreas.  It  is  formed  by  decomposition  of  the  nuclein  of 
the  cell-nuclei  and  is  hence  of  physiological  importance. 

VIII.  ESTERS 
(Oils,  Fats,  Waxes,  Candles,  Soaps) 

The  compounds  or  esters  formed  by  alcohols  with  inorganic  acids  have 
already  been  studied  (see  p.  196),  and  we  shall  now  consider  the  esters  resulting 

mature  fruits  resemble  cucumbers,  each  containing  50  to  60  seeds  like  beans.  Tbe  seeds  are  separated  from  tbe 
pulp,  heaped  in  casks  for  4  to  5  days  to  initiate  the  fermentation  which  increases  the  perfume,  and  then  dried 
in  the  sun.  The  chemical  composition  differs  considerably  with  the  variety  :  fatty  substance  (cocoa-butter),  35  to 
45  per  cent. ;  proteins,  3  to  18  per  cent. ;  cellulose,  3  to  25  per  cent. ;  gums  and  starch,  3  to  15  per  cent. ;  ash, 
3  to  4  per  cent.  Cocoa-butter  (or  cacao-butter)  is  extracted  by  pressing  the  seeda  hot,  and  forms  a  faintly  yellow 
mass  of  pleasing  odour  j  it  melts  at  29°  to  31°,  and  contains  the  glycerides  of  arachic,  palmitic,  oleic,  stearic,  and 
lauric  acids. 

In  the  manufacture  of  chocolate,  the  seeds  are  washed  in  suitable  sieves  and  then  gently  and  cautiously  heated 
for  30  to  40  minutes  to  facilitate  skinning.  They  are  next  crushed  in  mortars  or  rotating  cylinders,  the  flour 
obtained  being  made  into  a  paste  with  sugar  and  is  worked  for  a  long  time  on  stone  rollers,  different  ingredients 
and  flavouring  matters  being  added  to  give  the  different  kinds  of  chocolate ;  the  homogeneous  paste  then  passes 
to  the  moulds.  Good  chocolate  contains  from  40  to  60  per  cent,  of  cocoa,  the  rest  being  sugar ;  ordinary  qualities 
contain  10  to  15  per  cent,  of  starch. 

Italy  imported  12,000  quintals  of  cocoa  in  1901,  93,000  in  1908,  and  24,000  (including  5200  quintals  in  powder 
or  paste),  worth  £185,200,  in  1910,  in  addition  to  3380  quintals  of  cocoa-butter  of  the  value  of  £48,680.  Cocoa 
costs  about  £8  per  quintal,  and  pays  an  import  duty  of  £4  (in  Italy).  The  imports  of  chocolate  into  Italy  were 
8000  quintals  in  1901 ;  10,900  in  1908 ;  15,000,  worth  £180,000,  in  1910  ;  the  import  duty  being  £5  4*.  per 
quintal.  Italy  exports,  on  the  average,  2300  quintals  of  chocolate,  of  the  value  £28,000,  per  annum. 

1  Coffee  consists  of  the  seeds  of  one  of  the  Rubiacese  (Coffea  arabica),  which  grows  spontaneously  in  Southern 
Ethiopia  and  Arabia,  and  is  cultivated  on  an  enormous  scale  in  India,  the  Antilles,  Madagascar,  and  South  America. 
It  is  an  evergreen  plant,  6  to  9  metres  high  and  of  pyramidal  habit,  with  greyish  branches  and  lanceolated  leaves, 
the  flowers  (at  the  base  of  the  leaf)  being  white  and  pleasant-smelling,  like  jessamine.  The  fruit  forms  drupes 
like  cherries,  the  epicarp  passing  from  yellow  to  green  to  red  to  brownish,  and  the  mesocarp  being  yellow  and 
of  agreeable  taste.  The  endocarp  is  divided  into  two  compartments  surrounded  by  coriaceous  membrane  and 
each  containing  a  seed,  which  has  one  convex  and  one  flat,  furrowed  face,  and  is  covered  by  a  friable  pellicle 
the  endosperm  (albumen)  is  yellowish  or  greenish  and  horny. 

The  form  of  the  seed  varies  with  the  kind  of  the  coffee  (Coffea  mauritiana,  laurina,  llberica,  &c.).  Moclu 
coffee  berries  are  small  and  the  Australian  ones  large,  whilst  those  from  the  Antilles  are  intermediate  in  size. 

The  cultivation  of  coffee  has  received  a  considerable  impulse  in  Brazil,  where  as  much  as  400,000  tons  (almost 
half  the  total  production  of  the  world)  are  now  produced.  Of  the  Antilles  coffees,  the  most  highly  valued  is  that 
from  Porto  Rico. 

Coffee  berries  are  composed  of  celluloses  (18  per  cent.),  fatty  matters  (12  per  cent.),  gummy  and  saccharine 
substances  (10  per  cent.),  nitrogenous  compounds  (12  per  cent.),  mineral  salts  (4  to  5  per  cent.),  a  tannin  (caffe- 
tannic  acid,  8  per  cent.),  caffeine  (0-8  to  1-3  per  cent.),  caffearine  and  water  (11  per  cent.) .  When  roasted,  coffee 
develops  aroma  and  loses  15  to  20  per  cent,  in  weight,  but  increases  in  volume  by  one-third,  while  the  sugar 
caramelises  and  the  cellulose  carbonises  partially,  forming  a  brown  oil  which  is  denser  than  water,  dissolves  in 
ether,  and  constitutes  the  aromatic  substance  (caffeone).  Boasted  coffee  contains,  on  the  average,  1-5  per  cent, 
of  water,  13  per  cent,  of  nitrogenous  substances,  0-8  per  cent,  of  sugars,  13-5  per  cent,  of  fats,  4-8  per  cent,  of 
ash,  0-9  per  cent,  of  caffeine,  and  46  per  cent,  of  non-nitrogenous  substances ;  to  hot  water  this  coffee  gives  up 
about  25  per  cent,  of  its  weight. 

In  1900  Italy  imported  141,000  quintals  of  coffee ;  in  1908,  227,600  quintals ;  and  in  1910,  253,000  quintals 
(about  four-fifths  from  Brazil),  of  the  value  of  £1,062,080  ;  the  former  Customs  duty  of  £6  per  quintal  was  lowered 
slightly  in  1909. 

»  Tea  is  an  evergreen  shrub,  Thea  chinensis  (order  Ternstrcemiaceae),  cultivated  in  China,  Japan,  British  India, 
Java,  Ceylon,  and  Brazil.  The  leaves  (similar  to  those  of  the  white  willow)  are  twisted,  dried,  and  folded,  prior 
to  rapid  immersion  in  boiling  water  and  drying  on  heated  plates  (4  kilos  of  leaves  yield  1  kilo  of  tea).  Com- 
mercially the  numerous  varieties  are  grouped  into  three  types :  green,  black,  and  scented,  the  last  two  being 
slightly  fermented.  The  active  alkaloid  is  Theine  (see  above).  The  best  infusion  of  tea  is  obtained  by  macerating 
for  thirty  minutes  in  cold  water  and  then  adding  boiling  water,  the  liquid  being  poured  off  before  it  becomes 
very  brown  and  excessively  rich  in  tannin  (20  grms.  of  tea  per  litre  of  slightly  hard  water).  France  imported 
475,000  kilos  of  tea  in  1882  and  1,160,000  kilos  in  1906.  Italy  imported  69,000  kilos  in  1908  and  73,600  kilos, 
of  the  value  of  £11,120,  in  1910,  the  Customs  duty  being  £10  per  quintal, 

II  24 


370  ORGANIC    CHEMISTRY 

from  the  substitution  of  the  typical  hydrogen  of  organic  acids  by  alkyl  radicals. 
Various  isomerides  exist  with  these  compounds,  e.g.  methyl  butyrate  is 
isomeric  with  ethyl  propionate,  butyl  formate  with  propyl  acetate.  Attention 
will,  however,  more  especially  be  paid  to  the  esters  of  glycerine  (glycerides), 
since  on  these  are  based  the  fat,  oil,  soap,  and  candle  industries. 

PREPARATION.  These  esters  can  be  obtained  by  the  general  methods 
already  described  (loc.  cit.),  e.g.  by  the  action  of  the  acid  chlorides  or 
anhydrides  on  the  alcohols  or  sodium  alkoxides  : 

C2H5-CO-C1  +  C2H5-OH  =  HC1  +  C2H5-COOC2H5. 

They  are  also  formed  by  the  interaction  of  the  silver  salt  of  the  acid  and 
the  alkyl  iodide,  and  by  the  action  of  gaseous  hydrogen  chloride  on  a  hot 
alcoholic  solution  of  the  nitrile  of  the  acid.  Further,  the  alcohols  and  acids 
themselves  react,  slowly  in  the  cold  and  more  rapidly  although  not  completely 
in  the  hot,  with  formation  of  esters  : 

C2H5-OH  +  CH3-C02H  =  CH3-C02C2H5  +  H20. 

In  practice  the  preparation  is  carried  out  as  follows  :  the  dry  organic 
acid  is  mixed  with  an  excess  of  absolute  alcohol  and  the  mixture  saturated 
with  dry  hydrogen  chloride  gas,  left  for  some  time  in  a  moderately  warm 
place  and  then  poured  into  water  ;  the  ester  separates  in  an  insoluble  form 
after  neutralisation  of  the  aqueous  liquid  with  alkali  in  the  cold. 

In  this  reaction  the  acid  chloride  is  probably  formed  as  an  intermediate 
product:  CH3-C02H  +  HC1  =  H20  +  CH3-COC1 ;  the  latter— which  with 
water  might  give  the  reverse  reaction — being  in  presence  of  excess  of  the 
alcohol,  forms  the  ester  (equation  given  above).  But  esterification  is  never 
complete,  the  reaction  being  a  reversible  one  : 

CwH2n+1-OH  +  CnH2n02  '«,. >  H20  +  CwH2n_102-CwH2n+1. 

After  a  certain  time  a  system  is  obtained  which  contains  given  quantities  of  alcohol 
(a),  acid  (b),  water  and  ester  (z).  The  same  equilibrium  is  attained  by  mixing  1  mol.  of 
ester  and  1  mol.  of  water  as  by  mixing  1  mol.  of  acid  and  1  mol.  of  alcohol,  and  this 
equilibrium  is  represented  by  the  following  equation  for  bimolecular  reactions  (see  vol.  i, 
p.  67) :  k(a — z)(b — z)  =  ^z2,  where  a  and  b  represent  the  respective  initial  concentra- 
tions of  alcohol  and  ester  and  z  that  of  the  ester,  and  water  when  equilibrium  is  reached, 
all  expressed  in  mols.  (gram-molecules)  ;  k  and  Tc^  are  constants  depending  on  the  nature 
of  the  reaction  and,  according  to  a  definite  law,  slightly  on  the  temperature.  If,  for 

convenience,  -r  is  made  equal  to  K,  the  equation  becomes  :    (a — z)(b — z)  =  Kzz. 

With  46  grms.  of  alcohol  and  60  grms.  of  acetic  acid  (gram-molecules),  it  is  found 
experimentally  that  K  =  0-25,  and,  as  a  and  b  both  assume  the  value  1,  1  mol.  of 
each  reacting,  the  equation  becomes  (1 — z)2=0-25z2,  i.e.  1 — z—0-5z  or  z  =  f .  This 
means  that  when  a  state  of  equilibrium  is  reached,  the  system  contains  J  mol.  of  acetic 
acid  +  £  mol.  of  alcohol  +  f  mol.  of  ester  +  f  mol.  of  water.  Every  substance  partici- 
pating in  the  equilibrium  acts  in  proportion  to  its  mass.  If  the  above  equation  is  given 

ft  ___  2  5* 

the  form  =  K ,  it  becomes  evident  that,  in  order  to  displace  the  equilibrium 

z  b  —  z 

so  as  to  have  a  greater  value  of  z  (i.e.  of  esterification),  the  value  of  a  must  be  increased 
and  that  of  6  decreased,  esterification  being  complete  when  a  =  oo.  The  same  final 
result  is  o'btained  when  b  is  much  greater  than  a,  esterification  again  being  complete 
when  b  =  oo.  In  practice,  almost  complete  esterification  is  attained  when  1  mol.  of 
acid  is  employed  per  10  mols.  of  alcohol  or  vice  versa.  That  the  game  result  is  obtained 
with  excess  of  alcohol  as  with  excess  of  acid  is  shown  by  the  above  equation,  since,  if 
instead  of  TO  mols.  of  both  acid  and  alcohol,  n  times  as  many  molecules  of  acid  are  taken,  the 

equation  becomes  :  =  K ;  whilst  if  n  times  as  many  molecules  of  alcohol  are 


PREPARATION    OF    ESTERS 

Vi    Wi 2 

taken,  it  becomes  :  -         —  =  K  -    — •     But  these  two  equations  are  identical,  multiplica- 
tion of  the  terms  of  the  former  bv  — giving  the  latter. 

m  —  z 

The  limit  of  esterification  is  modified  but  slightly  by  change  of  temperature  and 
amounts,  in  the  case  of  acetic  acid,  to  62-2  per  cent,  at  10°  and  to  66-5  per  cent,  at  220°. 

The  esters  of  monohydric  alcohols  and  monobasic  fatty  acids  are  neutral 
liquids  lighter  than  water  (0-8  to  0-9)  and  pleasant  smelling  (some  forming 
artificial  fruit  essences)  ;  they  are  slightly  soluble  in  water  (the  first  members 
more  soluble  than  the  higher  ones)  and  they  boil  undecomposed. 

By  means  of  Grignard's  reaction  (see  p.  203),  they  yield  tertiary  alcohols. 

The  esters  are  hydrolysed  into  their  components  when  heated  with  alkali, 
mineral  acid,  or  aluminium  chloride,  or  superheated  with  water.  The  mineral 
acid  has  a  purely  catalytic  accelerating  action  on  the  following  reaction  due 
to  the  water,  which  is  very  slow  in  its  action  : 

CH3-C02C2H5  +  H20  =  C2H5-OH .+  CH3-C02H. 
With  bases,  the  hydrolysis  is  expressed  by  the  equation  : 

CH3-C02C2H5  +  NaOH  =  C2H5-OH  +  CH3-C02Na. 

The  hydrolysing  velocity  of  acids  and  bases  depends  on  their  degrees  of 
dissociation,  i.e.  on  their  strengths,  so  that  feeble  acids  and  bases  hydrolyse 
far  more  slowly  than  the  strong  ones.  In  the  case  of  acids,  the  hydrolysis 
is  caused  by  the  hydrogen  ions,  and  in  that  of  bases  by  the  hydro xyl  ions. 
In  the  latter  instance,  however,  the  velocity  of  hydrolysis  is  greater  than 
with  acids,  and  with  methyl  acetate,  the  value  of  K  for  decinormal  potassium 
hydroxide  is  1350  times  that  for  decinormal  hydrochloric  acid.  In  the  hydro- 
lysis of  fats,  the  acids  of  which  are  feeble  and  the  resultant  salts  therefore 
hydrolytically  dissociated  to  a  marked  extent  (i.e.  even  with  excess  of  fatty 
acid,  there  always  remains  free  base  or  hydroxyl  ions)  complete  hydrolysis 
is  obtained  industrially  with  a  quantity  of  base  (e.g.  lime)  much  lass  than  that 
required  theoretically. 

As  has  been  already  mentioned,  the  first  ethers  of  the  monobasic  acids  and 
monohydric  alcohols  are,  in  general,  substances  of  pleasing  odour  and  are 
used  with  suitable  admixtures  as  artificial  fruit  essences.1 

ETHYL  FORMATE,  H-COOC2H5,  boils  at  55°  and  is  used  for  artificial 
rum  or  arrack. 

ETHYL  ACETATE,  or  Acetic  Ester,  CH3-COOC2H5,  is  used  in  medicine 
and  for  the  preparation  of  ethyl  acetoacetate,  which  is  of  considerable  import- 
ance in  organic  syntheses.  It  is  prepared  by  heating  alcohol  with  acetic  and 
sulphuric  acids  under  the  conditions  given  above.  It  boils  at  77°  and  has  the 
sp.  gr.  0-9238  at  0°.  Methyl  Acetate  boils  at  57-5°  and  has  the  sp.  gr.  0-9577. 

AMYL  ACETATE,  CH3-COOC5Hn,  is  used  in  alcoholic  solution  as  essence 
of  pears.  It  boils  at  148°. 

1  Commercial  fruit  essences  are  prepared  from  the  following  mixtures  of  esters,  and  cost  from  2«.  6d.  to  5«. 
per  kilo : 

Essence  of  -pineapple  :  25  grms.  ethyl  butyrate  +  135  grms.  amyl  valerate  +  5  grms.  chloroform  +  5  grms. 
aldehyde  +  850  grms.  alcohol. 

Essence  of  apples  :  50  grms.  ethyl  nitrite  +  50  grms.  ethyl  acetate  +  100  grms.  amyl  valerate  +  40  grms. 
glycerol  +  7-5  grms.  aldehyde  +  7-5  grms.  chloroform  +  745  grms.  alcohol. 

Essence  of  pears:  200  grms.  amyl  acetate  +  50  grms.  ethyl  acetate  +  100  grms.  ethyl  nitrite  -f'20  grms. 
glycerol  +  630  grms.  alcohol. 

Essence  of  apricots  :  35  grms.  benzaldehyde  +  190  grms.  amyl  butyrate  +  10  grms.  chloroform  +  765  grms 
alcohol. 

Essence  of  strawberries  :  27  grms.  amyl  acetate  +  18  grins,  amyl  valerate  +  9  grms.  amyl  butyrate  +  9  grms. 
amyl  formate  +  15  grms.  ethyl  acetate  +  7  grms.  essence  of  violets  +  915  grms.  alcohol. 

Essence  of  peaches  :  100  grms.  amyl  valerate  +  100  grms.  amyl  butyrate  -\-  20  grms.  ethyl  acetate  -f-  10  grma. 
benzaldehyde  +  770  grms.  alcohol. 


ETHYL  BUTYRATE,  C3H7-  COOC2H5,  boils  at  121° and  is  used  as  essence 
of  pineapple  and  in  rum. 

ISOAMYL  ISOVALERATE,  C4H9-COOC5Hn,  boils  at  194°  and  is  used 
in  essence  of  apples. 

The  higher  esters  form  constituents  of  waxes  (Cetyl  Palmitate, 
C16H3102C16H33 ;  Melissyl  Palmitate,  C16H3]02C30H61  ;  Ceryl  Cerotate, 
C26H5102C26H53,  &c.)  These  higher  esters  distil  unchanged  only  in  a  vacuum  ; 
under  ordinary  pressure  they  decompose  into  olefines  and  fatty  acids. 

Esters  of  Polybasic  Acids  are  prepare  d  by  the  general  methods  described 
above  ;  acid  esters  are  obtainable  if  one  or  more  of  the  carboxyl  groups  are 
not  esterified. 

The  esters  of  oxalic  acid  are  obtained,  for  instance,  by  heating  anhydrous 
oxalic  acid  with  alcohols,  the  normal  ester  being  separated  from  the  acid 
ester  by  fractional  distillation. 

The  importance  of  Malonic  Esters  in  organic  syntheses  has  already  been 
illustrated  on  pp.  308  et  seq.  ;  the  normal  methyl  ester  boils  at  181°  and  the 
ethyl  at  198°  (sp.  gr.  1-068  at  18°).  The  two  hydrogen  atoms  united  with 
the  middle  carbon  atom  can  also  be  replaced  by  alkyl  groups.  Thus,  for 
example,  Ethyl  Dimethylmalonate,  (C2H5-  CO2) :  C(CH3)2,  is  obtained  from  the 
sodium  derivative  by  treatment  with  methyl  iodide.  These  compounds, 
when  heated,  lose  C02  and  yield  alkylacetic  derivatives.  Similar  relations 
are  found  with  the  alkyl  derivatives  of  succinic  acid  or  esters. 

The  preparation  of  Ethyl  Acetoacetate  and  its  importance  in  organic 
syntheses  have  been  dealt  with  on  p.  332. 

The  Normal  Methyl  Ester  of  succinic  acid,  CH3-CO2-CH2-CH2-C02-CH3, 
melts  at  19°  and  boils  at  80°  under  10  mm.  pressure ;  the  ethyl  ester  boils  at 
216°. 

GLYCERIDES,  OILS,  FATS 

Glycerol  being  a  trihydric  alcohol,  its  three  alcoholic  groups  may  be 
partially  or  wholly  esterified  by  acid  residues.  It  suffices,  indeed,  to  heat 
glycerol  with  fatty  acids  to  obtain  mono-,  di-,  and  tri-glycerides.  These 
glycerides  are  also  formed  by  the  action  of  the  tissues  of  the  pancreas  on  a 
mixture  of  oleic  acid  and  glycerol,  a  still  better  method  for  synthesising  fats 
being  the  treatment  of  the  sulphuric  ethers  of  glycerol  with  fatty  acids  dis- 
solved in  concentrated  sulphuric  acid.  Most  fats  and  oils  are  formed  of 
triglycerides,  which,  according  to  the  nature  of  the  fatty  acid  saturating  the 
three  alcoholic  groups  of  the  glycerol,  are  termed  Tripalmitin  (melts  at  60°), 
Tristearin  (melts  first  at  55°  and,  after  resolidification,  at  71-6°),  and  Triolein 
(liquid,  solidifying  at  about  0°). 

Triolein,  which  is  the  principal  component  of  liquid  fats  and  especially 
of  olive  oil,  is  formed  by  the  esterification  of  the  glycerol  molecule  with  3  mols. 
of  oleic  acid  (see  p.  298)  : 

CH2-OO-C18H33 

CH-00-C18H33 

CH2-0-0-C18H33V 

Mono-  and  di-glycerides  are  not  found  in  the  fats  (only  ravison  oil  contains 
a  diglyceride,  dicrucin ;  see  also  esters  of  polyhydric  alcohols  and  glycerol 
with  mineral  acids,  pp.  213,  222  et  seq.}. 

Certain  fats  (butter,  cocoa-butter)  contain  mixed  triglycerides,  i.e.  with 
different  acid  radicals,  some  of  them  being  of  acids  of  low  molecular  weights, 


REICHERT    AND    HEHNER   NUMBERS      373 

soluble  in  water.1  A.  Griin  (1906-1909)  synthesised  mixed  glycerides  con- 
taining three  acid  residues,  all  different.2  The  most  simple  glyceride  is 
Triformin,  C3H5(C02H)3,  which  was  obtained  crystalline  by  P.  van  Romburgh 
(1910)  by  protracted  heating  of  glycerol  with  100  per  cent,  formic  acid  ;  it 
crystallises  with  difficulty,  melts  at  18°,  boils  at  266°  (762  mm.  pressure), 
and  at  210°,  under  ordinary  pressure,  decomposes.  It  is  hydrolysed  slowly 
by  cold  water,  rapidly  by  hot. 

Oils  and  fats  have  coefficients  of  expansion  greater  than  those  of  other 
liquids  (100  litres  of  olein  at  0°  become  101-6  at  20°). 

Fats  and,  still  more,  waxes  contain  also  non-glyceride  components,  e.g. 
Cetyl  Alcohol,  C16H340,  which,  as  such  or  as  palmitic  ester,  forms  one  of  the 
principal  constituents  of  spermaceti  fat.  Cerotic  Acid,  C27H52O2,  and  its  ester 
occur  in  large  proportions  in  wax.  Non-hydrolysable  substances  (cholesterol, 
phytosterol,  isocholesterol,  aromatic  alcohols,  &c.)  are  always  found  in  small 
quantities  in  fats  (olive  oil,  about  0-75  per  cent.  ;  ravison  oil,  1  per  cent.  ; 
cotton-seed  oil,  1-6  per  cent.  ;  lard,  0-25  per  cent.  ;  cod  liver  oil,  0-5  to  3  per 

1  Volatile  fatly  acids  soluble  in  water.  The  number  of  c.c.  of  decinormal  potassium  hydroxide  solution  required 
to  neutralise  the  volatile  fatty  acids  soluble  in  water  from  5  grms.  of  the  fat,  constitutes  the  so-called  Reichert- 
Meissl-Wollny  number  and  serves  to  ascertain  the  purity  of  certain  fats,  especially  of  butter.  The  deter- 
mination is  made  as  follows  :  exactly  5  grms.  of  the  fat  (melted  at  a  low  temperature  and  rapidly  filtered)  are 
heated  in  a  flask  of  about  350  c.c.  capacity  with  10  c.c.  of  alcoholic  potash  (20  grms.  of  KOH  in  100  c.c.  70  per 
cent,  alcohol)  on  a  water-bath  with  frequent  shaking  until  almost  all  the  alcohol  is  evaporated  ;  the  remainder 
of  the  alcohol  is  completely  expelled  by  shaking  the  flask  and  introducing  a  current  of  air  every  half- minute. 
After  about  twenty  minutes,  when  the  smell  of  alcohol  is  no  longer  detectable,  100  c.c.  of  distilled  water  are 
added,  the  heating  being  continued  until  a  clear  solution  is  obtained  (if  the  liquid  does  not  become  clear  the  test 
must  be  commenced  anew,  hydrolysis  being  incomplete).  To  the  tepid  solution  are  then  added  40  c.c.  of  dilute  sul- 
phuric acid  (1  vol.  cone.  H£SO4  +  10  vols.  water)  and  a  few  fragments  of  pumice,  the  flask  being  then  placed  on  a 
double  wire-gauze  and  the  liquid  distilled,  the  dimensions  of  the  apparatus  being  shown  in  mm.  in  Fig.  248.  In  about 
half  an  hour,  exactly  110  c.c.  of  liquid  distil  over  ;  this  is  mixed  and  filtered  through  a  dry  filter,  100  c.c.  of  the 
filtrate  being  titrated  with  decinormal  KOH  solution  in  presence  of  phenolphthalein.  The 
volume  of  the  alkali  used  is  increased  by  one-tenth  of  its  value  (the  volume  of  the  distillate 
being  110  c.c.)  and  diminished  by  the  number  of  c.c.  of  the  alkali  obtained  from  a  control  ex- 
periment made  without  fat  as  a  check  on  the  reagents  employed.  The  result  is  the  Reichert- 
Meissl-Wollny  number.  At  the  present  time  many  laboratories  employ  the  Leffmann- 
Beam-1'olenske  method,  which  effects  more  rapid  hydrolysis  (see  later,  Butter).  For  butter 
the  limits  for  this  number  allowed  by  law  are  26  to  31-5  (Municipal  Laboratory  of  Milan),  the 
butter  being  suspected  if  it  gives  a  value  of  22  to  23,  although  the  butter  of  certain  districts 
and  from  certain  animals  may,  in  exceptional  cases,  give  a  number  as  low  as  21.  The  value 
for  rancid  butter,  even  two  months  old,  is  only  slightly  lower  (by  about  2)  than  the  normal. 

Insoluble  fatty  acids.  The  quantity  of  fatty  acid  insoluble  in  water  obtainable  from 
100  parts  of  fat  is  called  the  Hehner  number,  and  is  determined  as  follows  :  into  a  flask 
of  about  200  c.c.  capacity  are  dropped,  from  a  weighed  vessel  containing  the  dry  filtered 
fat,  3  to  4  grms.  of  the  substance,  the  vessel  being  then  reweighed  exactly.  After  addition 
of  50  c.c.  of  alcohol  and  1  to  2  grms.  of  KOH,  the  flask  is  heated  on  a  water-bath  for 
five  minutes,  a  clear  solution  being  obtained.  If  the  addition  of  a  drop  of  water  produces 
turbidity,  saponification  is  incomplete,  and  the  heating  is  continued  for  a  further  period 
of  five  minutes,  the  liquid  being  then  tested  as  before.  Evaporation  is  then  continued 
until  there  remains  a  dense  mass,  which  is  taken  up  in  100  to  150  c.c.  of  water,  acidified 
with  dilute  sulphuric  acid,  and  heated  until  the  clear  fatty  acids  float  on  the  surface. 
The  liquid  is  then  poured  on  a  dry,  tared  filter  (about  12  cm.  in  diameter  and  in  a  funnel 
either  without  a  neck  or  with  a  very  short  one),  previously  half  filled  with  hot  water.  The 
acids  are  washed  with  boiling  water  until  the  washing  water  ceases  to  show  an  acid 
reaction  (as  much  as  2  litres  of  water  are  sometimes  required).  The  filter  is  then  cooled 
in  a  beaker  of  water  so  that  the  fatty  acids  solidify.  The  filter  is  then  detached  from 
the  filter  and  introduced,  with  the  acids,  into  a  tared  beaker,  which  is  heated  in  an  oven 
at  100°  to  102°  until  its  weight  remains  almost  constant  (difference  between  two  weighings  less  than  1  mgrm.). 
The  weight  of  fatty  acids,  referred  to  100  parts  of  fat,  represents  the  Hehner  number. 

Unadulterated  fats  generally  have  Hehner  numbers  of  95  to  97  (for  butter  it  is  87-5  ;  for  coco-nut  oil,  85  to 
92  ;  for  palm  oil,  91). 

1  The  synthesis  of  triolein  has  been  applied  practically  by  G.  Gianoli  (1891)  to  diminish  the  ranc'dity  of  oils, 
especially  of  olive  oil  obtained  from  the  husks  by  means  of  carbon  disulphide.  This  oil  contains  20  to  30  per 
cent.,  or  even  more,  of  oleic  acid,  and  is  heated  in  an  autoclave  with  the  corresponding  quantity  of  glyc-erol  (or 
even  a  slight  excess)  at  250°  in  a  slow  stream  of  CO2,  or  in  a  vacuum  with  a  trace  of  oxalic  acid  to  facilitate  mixing 
of  the  liquids  and  avoid  blackening  of  the  mass  owing  to  the  presence  of  hydroxy-acids  ;  the  distillation  of  the 
water  formed  in  the  reaction  is  hastened  by  adding  fragments  of  tin  to  the  mass.  This  procedure  yields  a  neutral 
or  almost  neutral  oil  with  an  iodine  number  less  than  75  and  a  marked  viscosity,  so  that  it  can  be  used  even  for 
mixing  with  lubricating  oils.  Bellucci  (1911)  also  achieved  an  almost  quantitative  synthesis  by  heating  together 
the  theoretical  proportions  of  glycerol  (1  mol.)  and  fatty  acid  (3  mols.)  at  180°  to  260°  for  two  hours  in  a  vacuum, 
so  as  to  expel  the  water  formed,  which  would  otherwise  produce  the  reverse  reaction  ;  in  a  current  of  CO2,  the 
same  reaction  takes  place  at  the  ordinary  pressure.  A.  Walter  (1911)  obtained  a  mixture  of  tri-  and  di-oloins 
by  treating  glycerol  and  acetic  acid  in  presence  of  the  enzymes  of  castor  oil  seeds,  which  act  as  catalysts.  Indeed, 
catalysts  cause  reversible  reactions,  and  while  in  presence  of  water  the  enzymes  of  castor  oil  seeds  hydrolyse  fats 
(see  p.  409)  with  formation  of  glycerol  and  fatty  acids,  if  water  is  excluded  as  much  as  35  per  cent,  of  tne  fatty 
acids  can  be  converted  into  glycerides. 


FIG.  248. 


374 


ORGANIC    CHEMISTRY 


cent.  ;  tallow,  0-02  to  0-6  per  cent.  ;  bone-fat,  0-4  to  2-4  per  cent.  ;  wool-fat 
more  than  7  per  cent.).  The  oils  of  cereals  and  of  Leguminosece  contain 

abundant  amounts  of  LECITHIN,   (ClsHS502)2CsH5-POll<^r  „    nw5  wni°h 

is  decomposed  by  the  enzyme  of  the  pancreas  or  castor  oil  seed,  but  not  by 
that  of  the  blood  (serum-lipase) .  The  fat  of  peas  contains  1-17  per  cent,  of 
phosphorus  or  30-4  per  cent,  of  lecithin,  and  that  of  wheat,  0-25  per  cent,  of 
phosphorus  or  6-5  of  lecithin  ;  the  amount  of  lecithin  is  obtained  by  multi- 
plying that  of  phosphorus  by  26. 

Fresh  fats  and  oils  contain  minimal  proportions  of  free  fatty  acids  (less 
than  1  per  cent.),  these  increasing  with  lapse  of  time,  especially  if  the  fats  are 
not  melted. 

This  rancidity  is  facilitated  by  sunlight  and  also  by  the  protein  sub- 
stances of  unrefined  fats  and  oils.  Coco-nut  oil  does  not  readily  turn 
rancid,  but  with  olive  oil  the  proportion  of  free  oleic  acid  reaches  25  per 
cent.,  and  with  palm  oil  as  much  as  70  per  cent,  of  free  acids  may  be  formed. 
The  taste  and  smell  of  fats  depend,  not  on  the  glycerides,  but  on  other 
substances. 

The  specific  gravity  of  oils  and  fats  varies  from  0-875  to  0-970  (see  Table 
given  later)  and  is  determined  by  means  of  an  aerometer  or  Westphal  balance 
(see  vol.  i,  p.  73).  They  are  almost  completely  insoluble  in  water,  acetone, 
or  cold  alcohol  (this  dissolves  a  certain  amount  of  castor  oil  and  of  olive- 
kernel  oil).  The  solubility  increases  in  boiling  alcohol  and  is  complete  in 
ether,  chloroform,  carbon  disulphide  or  tetrachloride,  petroleum  or  petroleum 
ether  (in  the  last  two,  castor  oil  is  slightly  soluble,  while  ether  dissolves  a  little 
pure  tristearin).1 

When  heated  on  a  spatula  held  some  distance  above  a  flame,  all  fats  give 
greenish  flames  owing  to  the  presence  of  carbon  monoxide  and  sodium  ;  also 
all  fats  are  blackened  by  osmium  tetroxide  (sensitive  reaction). 

Oils  dissolve  small  quantities  of  sulphur  or  phosphorus  and  larger  quan- 
tities of  soaps  even  when  they  are  dissolved  in  ether  or  petroleum 
ether. 

The  oxygen  of  the  air  exerts  a  marked  and  rapid  influence, 
as  it  is  fixed  by  the  drying  oils  (linseed,  walnut,  hemp-seed,  poppy- 
seed,  &c.),  which  are  thus  transformed  into  varnishes,  this  occur- 
ring more  readily  if  the  oils  are  boiled  with  oxide  of  lead  or 
of  manganese. 

With  the  other — non-drying — oils,  the  air  (together  with  light) 
gradually  causes  rancidity,  which,  however,  some  attribute  to  the 
action  of  bacteria,  or  rather  to  hydrolysing  and  oxidising  enzymes ; 
however  this  may  be,  the  acidity  increases  owing'  to  formatioli 
of  butyric,  caproic,  oleic,   &c.,  acids,   but  the  rancid  taste  and 
smell  are  due    more    especially  to  the  formation  of  aldehydic, 
,*   ketonic,  and   ethereal   substances,    hydroxy-acids,    and    volatile 
;<^   acids  which  can  be  eliminated  by  repeated  washing  with  dilute 
*   solution  of  alkali  and  subsequently  of  bisulphite  (for  the  alde- 
hydes and  ketones,  see  later,  Renovated  Butter). 

1  To  determine  the  quantity  of  fat  contained  in  any  solid  substance,  a  weighed  portion  of 
the  latter  in  a  finely  divided,  dry  state  (5  to  15  grins,  are  taken  and,  if  pasty,  mixed  with 
fragments  of  pumice)  is  introduced  into  a  filter-paper  cartridge  situate  in  a  Soxhlet  apparatus 
(Fig.  249). 

The  Soxhlet  apparatus  is  connected  at  the  bottom  with  a  tared  flask  resting  on  a  water- 
bath,  and  at  the  top  with  a  reflux  condenser.      From   100  to  150  c.c.  of  petroleum  ether  or 
ether  are  then  added  and   extraction  continued   for  2  to  4   hours  in  such  a  way  that  the 
FlG.   249.         solvent  siphons  over  15  or  20  times  per  hour.     A  calcium  chloride  tube  may  be  attached  to 
the  extremity  of  the  condenser  to  prevent  access  of  moisture  from  the  air.     The  solvent  is 
afterwards  evaporated  from  the  flask  and  the  residual  fat  dried  at  100°  to  102°  until  almost 
constant  in  weight. 

ILc  difference  between  the  weight  of  fat  and  that  of  the  original  substance  gives  the  solids  not  fat. 


IODINE    NUMBER:    REFRACTIVE    INDEX     375 

When  fats  turn  rancid,  the  iodine  number1  is  lowered  and  the  index  of 
refraction?  the  dropping  or  melting  point  (see  pp.  5  and  16),  and  the  acetyl 
number  (see  p.  189)  rise.  In  butter  rancidity  is  facilitated  by  the  presence  of 
the  casein  and  milk-sugar,  which  give  rise  to  other  decompositions.  Although 
not  rigorously  exact,  the  degree  of  rancidity  is  expressed  by  the  number  of 
c.c.  of  normal  potash  necessary  to  neutralise  100  grins,  of  the  fat.  A  butter  with 
10°  of  rancidity  should  be  rejected.  The  free  fatty  acids  in  fats  and  oils  are 
usually  determined  with  a  decinormal  alkali  solution,  5  to  10  grms.  of  the  fat 
being  dissolved  in  50  to  60  c.c.  of  a  perfectly  neutral  mixture  of  alcohol  and 
ether  (1:2)  and  phenolphthalein  being  used  as  indicator.  The  acid  number 
gives  the  number  of  mgrms.  of  KOH  necessary  to  neutralise  1  grm.  of  fat. 

By  passing  a  current  of  air  through  oils  heated  to  70°  to  120°,  the  so-called 
blown  or  oxidised  oils,  rich  in  triglycerides  of  hydroxy-acids,  are  obtained. 
These  are  dark  in  colour  and  have  the  density  of  castor  oil  (but  are  soluble 
in  petroleum  ether),  but  if  "  blown  "  in  the  cold  for  a  longer  time,  they  are 

1  The  Iodine  Number  is  characteristic  of  a  fat  (see  Table,  p.  378),  and  expresses  the  percentage  of  iodine 
absorbed  by  the  fat  (i.e.  by  its  unsaturated  components,  e.g.  oleic  acid  or  the  corresponding  glycerides,  two  atoms 
or  iodine  being  fixed  for  each  double  linking,  see  p.  87).  This  determination  requires  :  (1)  An  iodine  solution 
obtained  by  mixing,  48  hours  before  using,  equal  volumes  of  the  two- following  solutions  :  (a)  25  grms.  of  iodine  in 
500  c.c.  of  pure  95  per  cent,  alcohol,  and  (6)  30  grms.  of  mercuric  chloride  in  500  c.c.  of  pure  95  per  cent,  alcohol ; 
(2)  a  sodium  thiosulphate  solution,  prepared  by  dissolving  24  grms.  of  the  pure  salt  in  a  litre  of  water,  the  titre 
in  iodine  being  ascertained  as  follows  :  3-8657  grms.  of  pure,  dry  potassium  dichromate  are  dissolved  in  water 
at  15°  and  the  solution  made  up  to  a  litre  ;  exactly  20  c.c.  of  this  solution  are  introduced  into  a  flask  with  a  ground 
stopper,  about  15  c.c.  of  a  10  per  cent,  potassium  iodide  solution  (free  from  hydroxide)  being  added  and  then 
5  c.c.  of  concentrated  hydrochloric  acid.  This  procedure  results  in  the  liberation  of  exactly  0-2  grm.  of  iodine. 
The  thiosulphate  solution  is  run  into  this  from  a  burette  until  the  solution  is  only  faintly  yellow.  A  few  drops 
of  fresh  starch-paste  are  then  added  and  addition  of  the  thio- 
sulphate continued  until  the  blue  colour  disappears.  It  is  thus 
found  how  much  iodine  corresponds  with  1  c.c.  of  thiosulphate 
solution,  the  strength  of  which  remains  constant  for  several 
months. 

The  iodine  number  is  determined  by  dissolving  a  known 
weight  of  the  fat  or  oil  (0-2  to  0-5  grm.  or,  for  drying-oils,  0-1  to 
0-12  grm.),  in  a  500  to  800  c.c.  flask  with  a  ground  stopper, 
in  15  c.c  of  pure  chloroform  and  adding  25  c.c.  of  the  iodine 
solution  (prepared  forty-eight  hours  previously,  as  stated 
above) ;  if,  after  two  hours,  the  liquid  is  no  longer  very  brown, 
a  further  measured  volume  of  iodine  solution  is  added  and  the 
whole  left  in  the  dark.  After  six  hours  the  excess  of  iodine  left 
unabsorbed  by  the  fat  is  determined  by  adding  20  c.c.  of  a  10 
per  cent.  KI  solution,  diluting  with  150  c.c.  of  water,  and  add- 
ing more  KI  if  the  reddish  brown  solution  is  not  clear.  The 
excess  of  iodine  is  then  titrated  with  the  thiosulphate  solution 
in  the  manner  already  described.  Immediately  afterwards,  25 
c.c.  of  the  iodine  solution  employed  are  titrated.  The  difference 
between  the  two  values  thus  obtained,  expressed  as  grammes  of 
iodine  per  100  grms.  of  the  fat,  represents  the  iodine  number. 

1  The  index  of  refraction  is  measured  in  the  Zeiss  Butyro- 
refractometer  (Fig.  250),  by  observing  the  total  reflection  of 
a  very  thin  layer  of  oil  or  fat  situate  between  two  prisms,  p, 
mounted  in  the  two  chambers,  A  and  B  (the  latter  rotates  on 
the  hinge,  C,  so  as  to  squeeze  uniformly  the  film  of  oil  smeared 
in  p  ;  the  screw,  F,  fixes  B  against  A).  Indirect  light  from  the 
sun  or  from  a  powerful  sodium  lamp  is  passed  through  the 
prisms  by  means  of  the  mirror,  •/,  and  the  limit  between  the 
light  and  dark  portions  of  a  scale  reading  from  0  to  100  is  read 
through  the  eye-piece,  K.  A  thermometer,  M,  indicates  the 

temperature  at  which  the  observation  is  made,  and  this  temperature  can  be  regulated  (so  as  to  melt  solid  fats) 
by  passing  water,  at  a  higher  or  lower  temperature,  in  at  E  and  through  the  rubber  tube,  D,  to  the  outflow,  e. 
The  refraction  is  usually  stated  in  the  centesimal  degrees  of  the  Zeiss  scale,  the  temperature — normally  25° — 
being  indicated.  Values  obtained  at  other  temperatures  can  be  referred  to  the  normal  temperature  by  adding 
or  subtracting  0-55  for  each  degree  above  or  below  25°  (the  number  0-55  is  accurate  for  butter,  but  slightly 
inexact  for  other  fats). 

The  index  of  refraction  is  obtained  from  the  reading  on  the  Zeiss  scale  by  adding  to  the  value  1-4220  as  many 
ten -thousandths  as  are  obtained  by  multiplying  the  scale  degrees  by  7-8  when  the  reading  is  between  0  and  30  ; 
7-5  if  between  30  and  50  ;  7-3  if  between  50  and  70  ;  and  7-0  if  between  70  and  100.  (This  procedure,  too,  gives 
accurate  values  for  butter,  but  slightly  inaccurate  ones  for  other  fats).  Thus,  30°  on  the  Zeiss  scale  would  corre- 

7-  8 
spond  with  a    refractive    index  of  1-4220  +  30  X  ,nnn/.   =  1-4220  +  6-0234  =  1-4454,  which    agrees    almost 

10000 
exactly  with  the  true  index  of  refraction  (1-4452) ;    similarly,  60°  on  the  scale  means  a  refractive  index  of 

7  3 
1-4220  +  60  x  — =  1-4658.     Inversely,    the   scale  reading  is  obtained    by    subtracting    1-4220   from   the 

refractive  index  and  dividing  the  remainder  by  7-8,  7-5,  7'3,  or  7-0. 

The  colour  of  the  line  of  demarcation  on  the  scale  sometimes  gives  an  indication  of  impurity  in  the  fat,  being 
colourless  for  pure  butter,  blue  if  margarine  is  present,  and  orange  with  admixtures  of  certain  other  fats. 


FiG.   250. 


376 


ORGANIC    CHEMISTRY 


obtained  almost  colourless.  Blown  oils  are  valued  as  lubricants.  If  the 
blowing  is  continued,  yellow  or  brown  gelatinous  masses  are  obtained.  With 
the  exception  of  the  iodine  number  and  the  Hehner  number — which  are 
lowered — the  chemical  and  physical  constants  of  blown  oils  (thickened oils,  &c.) 
are  higher  than  those  of  the  original  oils.  Oils  also  fix  ozone  in  proportion 
to  the  unsaturated  fatty  acids  they  contain,  and  at  the  same  time  become 
denser  (see  p.  299)  ;  olive  oil  has  an  ozone  number  of  15-8  (grms.  of  ozone 
fixed  per  100  grms.  of  oil,  Fenaroli,  1906)  ;  maize  oil,  21  ;  linseed  oil,  33  ; 
and  castor  oil,  16.  Also  sulphur  is  dissolved  and  combined  in  amount  increasing 
with  the  proportion  of  glycerides  of  unsaturated  acids  present,  giving  very 
viscous,  brown  liquids,  sometimes  almost  solid  and  gummy. 

Chlorine  acts  on  fats,  partly  replacing  hydrogen  and  partly  combining 
directly. 

Iodine  is  added  slowly,  but  the  addition  becomes  rapid  in  alcoholic  solution 
and  in  presence  of  mercuric  chloride  (Hiibl). 

Addition  of  concentrated  Sulphuric  Acid  to  oils  results  in  the  development 
of  heat  and  the  evolution  of  sulphur  dioxide  ;  in  the  cold,  sulphuric  ethers 
of  the  triglycerides  are  formed.1 

Dilute  Nitric  Acid,  in  the  hot,  slowly  oxidises  fats,  while  the  concentrated 
acid  attacks  them  with  evolution  of  red  vapours. 

Nitrous  Acid  renders  non-drying  oils  denser  and  solidifies  them,  the  triolein 
being  converted  into  trielaidin  (see  p.  298)  ;  the  drying  oils  remain  liquid, 
although  their  specific  gravity,  viscosity,  and  saponification  number  increase, 
and  the  iodine  number  and  Hehner  number  (per  cent,  of  insoluble  fatty  acids) 
diminish. 

When  burnt,  fats  give  the  characteristic  odour  of  acrolei'n,  which  is  derived 
from  the  glycerol. 

On  paper,  fats  and  oils  produce  a  translucent  spot,  insoluble  in  water 
(different  from  glycerol). 

All  these  reactions  serve  as  qualitative  and  quantitative  tests  to  establish 
the  purity  of  fatty  substances  (see  later). 

WAXES.  Unlike  fats,  waxes  are  usually  composed,  not  of  triglycerides,  but  of  esters 
derived  from  the  higher  monohydric  alcohols  (e.g.  cetyl,  myricyl,  and  ceryl  alcohols, 
cholesterol,  &c.),  and  sometimes  dihydric  alcohols  also.  They  contain,  in  addition,  the 
high  acids  (e.g.  palmitic,  stearic,  cerotic,  oleic,  &c.)  and  alcohols  in  the  free  state.  Further, 
beeswax  contains  as  much  as  15  per  cent,  of  high  melting-point  hydrocarbons. 

They  form  homogeneous  mixtures  in  all  proportions  when  fused  with  fats  and  give 
also  a  greasy  spot  on  paper,  but  they  yield  no  odour  of  acrolei'n  when  burned  (unlike 
fats)  and  do  not  become  rancid  when  exposed  to  the  air. 

The  commonest  waxes  are  beeswax,  Japanese  wax,  spermaceti 
wax  (from  whales),  and  carnauba  wax  (from  the  leaves  of  certain 
palms). 

Beeswax  forms  the  hexagonal  cells  of  beehives.  After  the  honey 
has  been  expressed,  the  mass  is  melted  with  water  to  remove  im- 
purities ;  on  cooling,  a  solid  layer  of  crude  wax  separates  at  the 
surface,  and  this,  after  melting  and  casting  into  blocks,  forms  virgin 
or  yellow  wax.  This  is  placed  on  the  market  in  various  qualities 
and  colours,  some  of  them  being  olive-brown  ;  they  bear  the  name 
of  the  place  of  origin  and  can  be  bleached  with  varying  facility. 


FIG.  251. 


1  Maumene1  found  that  the  rise  of  temperature  produced  by  sulphuric  acid  of  definite 
concentration  serves  to  distinguish  different  fats  (see  Table  given  later).  This  constant 
(Maumeni'  number)  is  nowadays  determined  by  means  of  the  Tortelli  thermo-oleometer 
(1905).  20  c.c.  of  the  oil  are  poured  into  the  glass  receiver,  A  (Fig.  251),  the  jacket  of 
which  has  been  evacuated.  The  oil  is  stirred  with  the  thermometer,  B,  fitted  with 

platinum  vanes  and  the  initial  temperature  read.    5  c.c.  of  concentrated  sulphuric  acid  (sp.  gr.  1-8413  or  66°  B6.) 

are  then  added  from  a  pipette  in  thirty  seconds,  the  liquid  being  kept  sHrred  as  long  as  the  temperature  rises. 

The  rise  of  temperature  is  the  Maumeni-  number.     If  the  sulphuric  acid  has  not  the  density  given  above,  but  is 

allowed  to  absorb  even  traces  of  moisture,  discordant  results  are  obtained. 


HYDROLYSIS    OF    FATS  377 

The  European  waxes  have  the  following  physical  and  chemical  constants,  which  allow 
of  the  detection  of  the  frequent  adulteration  to  which  they  are  subjected  :  melting-point, 
62°  to  64°  ;  solidification  point,  60°  ;  specific  gravity  at  98°  to  100°,  0-822-0-847  ;  saponi- 
fication  number,  95  to  97  (rarely  88  to  105)  ;  acidity  number,  19  to  22  ;  difference  between 
saponification  number  and  acid  number  (ester  number),  74  to  76  ;  iodine  number,  8  to  11  ; 
degrees  on  the  Zeiss  butyro-refractometer  at  40°,  44  to  45-5  (rarely  42).  Foreign  waxes 
have  somewhat  different  constants. 

The  bleaching  of  the  wax  is  effected  by  melting  it  several  times  with  slightly  acidified 
water,  allowing  it  to  cool  slowly  so  as  to  separate  the  impurities  more  thoroughly  and 
then  causing  it  to  solidify  in  thin  layers  on  a  cylinder  half  immersed  in  water  and  exposing 
these  to  the  sun  and  air  for  five  to  six  weeks.  A  more  expeditious  method  of  bleaching 
consists  in  treatment  with  hydrogen  peroxide  or  other  oxidising  agent  (dichromate  and 
dilute  sulphuric  acid),  or  with  animal  charcoal.  The  white  wax  thus  obtained — often 
improved  in  appearance  by  the  addition  of  4  to  5  per  cent,  of  tallow — presents  almost 
the  same  physical  and  chemical  constants  as  the  virgin  wax,  the  iodine  number  alone 
being  lowered  by  1  to  7. 

The  wax  is  insoluble  or  only  slightly  soluble  in  cold  alcohol  or  ether,  but  dissolves 
in  the  boiling  solvents.  It  dissolves  in  the  cold  in  chloroform,  oil  of  turpentine,  carbon 
disulphide,  or  fatty  oils.  It  resists  dilute  caustic  alkalis  and  concentrated  alkali  car- 
bonates. It  is  used  for  making  candles,  waxed  cloth  and  paper,  mastics,  artificial  fruit 
and  flowers,  &c. 

Carnauba  Wax  is  exuded  from  the  leaves  of  certain  palms  (Corypha  cerifera)  of  Brazil 
and  Venezuela.  In  the  crude  state,  it  is  hard  and  brittle,  and  of  a  yellowish  green  colour  ; 
it  melts  at  83°  to  88°,  has  an  acid  number  of  4  to  8,  a  saponification  number  of  80  to  95, 
an  ester  number  of  75  to  76,  and  an  iodine  number  of  7  to  13,  and  contains  more  than 
50  per  cent,  of  non-hydrolysable  substances.  It  is  used  for  the  manufacture  of  candles 
and,  mixed  with  potash  (soft)  soap,  forms  the  encaustic  with  which  pavements  are  cleaned. 

Japanese  Wax  is  the  fat  extracted  from  the  fruit  of  certain  Japanese  and  Chinese 
trees  of  the  order  Terebinthacese  (Rhus  succedanea,  R.  vernicifera,  and  R.  sylvestris).  It 
differs  from  beeswax  in  having  an  ester  number  of  about  200  and  a  saponification  number 
of  about  220.  It  is  completely  hydrolysable,  since  it  consists  of  glycerides  of  palmitic, 
stcaric,  and  arachic  acids,  and  contains  also  9  to  13  per  cent,  of  free  palmitic  acid. 

STATISTICS.  The  United  States  imported  2100  tons  (£142,600)  of  vegetable  wax  in 
1910  and  2200  tons  (£199,400)  in  1911.  In  1900  Italy  imported  about  1000  quintals  of 
wax,  almost  all  in  the  raw  state,  and  exported  about  1900  quintals  of  crude  yellow  and 
1100  quintals  of  white,  treated  sorts.  In  1906,  the  imports  were  1452  quintals  ;  in  1908, 
1015  quintals  ;  and  in  1910,  1070  quintals  (of  the  value  of  £14,000).  In  1906  Germany 
imported  more  than  25,000  quintals  of  wax  and  exported  more  than  4000,  besides  10,000 
of  candles,  &c.  England  imported  3350  tons  of  wax  in  1909  and  3070  tons  (£259,049) 
in  1910.  Yellow  beeswax  costs  up  to  £15  per  quintal,  and  the  bleached  wax  £17. 

Hydrolysis  (Saponification)  of  Fats  and  Waxes.  The  term  saponification 
is  applied  to  the  decomposition  of  fats  into  the  alcohols  and  acids  composing 
them,  with  simultaneous  addition  of  a  molecule  of  water  (hydrolysis),  by 
heating  with  water  under  pressure  at  200°  or  by  the  action  of  acid  or  alkali 
(see  p.  371)  ;  when  alkali  is  used,  the  alkali  salt  (soap)  of  the  fatty  acid  and 
not  the  free  acid  itself  is  obtained  : 

C3H5(O.OC18H35)3  +  3KOH  =  C3H5(OH)3  +  3C18H3502K. 

Tristeariu  Glycerine  Potassium  stearate 

The  mechanism  of  the  saponification  of  fats. was  for  long  a  matter  of  con- 
troversy. Some  regarded  it  as  occurring  gradually,  1  mol.  of  fat  first 
reacting  with  1  of  alkali  (bimolecular  reaction)  (see  vol.  i,  p.  67)  and  di-  and 
mono -glycerides  being  formed  as  intermediate  products,  whilst,  according  to 
others,  saponification  was  a  single  (tetramolecular)  reaction.  Only  since 
the  investigations  of  Geitel  (1897),  Lewkowitsch  (1898-1901)  and,  more 
especially,  Kremann  (1906),  does  it  appear  to  be  established  with  certainty 
that  saponification  is  gradual,  consisting  of  successive  bimolecular  reactions, 


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ANIMAL    OILS    AND    FATS  379 

Saponification  with  lime,  baryta,  or  lead  oxide  is  never  so  complete  as 
with  caustic  potash  or  soda  in  the  hot,  while  with  an  alcoholic  solution  of  caustic 
potash  or  soda  it  is  complete  and  rapid,  formation  of  the  ethyl  ester  of  the 
fatty  acids  and  liberation  of  glycerine  first  occurring  and  then  complete 
hydrolysis  of  the  ethyl  ester.  The  latter  can  be  obtained  directly  from  fats 
by  heating  with  slightly  acidified  alcohol. 

Sodium  and  potassium  carbonates' do  not  attack  the  fats. 

A  process  has  been  patented  for  saponifying  fats  with  sulphur  dioxide 
or  bisulphite  in  autoclaves  at  10  to  15  atmos.  pressure,  or  even  directly  with 
sodium  chloride  and  ammonia  (Garelli,  1907  ;  see  later,  Soaps). 

Waxes  and  wool-fat  are  also  saponified,  although  with  less  ease,  in  the 
same  way ;  with  a  2N-alcoholic  caustic  potash  solution  and  heating  under 
pressure,  saponification  is,  however,  complete. 

No  matter  how  difficult  the  saponification  of  a  fat,  it  can  be  rendered 
complete  even  in  the  cold  by  the  Henriques  process,  which  consists  in  dis- 
solving, say,  3  to  4  grms.  of  the  fat  in  25  c.c.  of  petroleum  ether  and  25  c.c. 
of  normal  alcoholic  potash,  the  mixture  being  shaken  from  time  to  time  during 
a  period  of  twelve  hours  ;  on  heating,  waxes  are  also  dissolved  in  this  manner. 
To  determine  the  quantity  of  alkali  fixed  (saponification  number)^  the  excess 
of  alkali  is  titrated  with  normal  acid  solution. 

Dilution  of  the  saponified  waxes  with  a  considerable  amount  of 
water  results  in  the  separation  of  the  higher  alcohols,  which  can  be  extracted 
with  ether.  Spermaceti  contains  40  to  60  per  cent,  of  these  insoluble  alcohols 
(which  are  known  industrially  as  non-saponifiable  substances),  beeswax 
53  per  cent.,  and  carnauba  wax  55  per  cent. 

ANIMAL  OILS  AND  FATS 

It  is  not  possible  here  to  study  in  detail  all  fats,  so  that  only  the  more 
important  ones,  the  processes  of  treating  which  are  partially  applicable  to 
the  others,  will  be  considered. 

Classification  of  fats  into  those  of  animal  and  those  of  vegetable  origin 
or  into  solids  (tallow,  lard,  sheep's  tallow,  goose  grease,  and  coco-nut  butter) 
and  liquids  (oils),  is  of  no  practical  value,  but  it  is  necessary,  with  the  liquid 
vegetable  fats,  to  distinguish  between  those  which  have  drying  (linseed, 
walnut,  poppy-seed)  from  those  with  non-drying  properties  (olive,  colza,  arachis, 
castor,  cotton-seed,  maize,  &c.). 

Animal  fats  are  usually  melted  (by  direct-fire  heat  or  by  steam)  or  com- 

1  The  Saponification  number,  or  KiMstorf  number,  indicates  the  number  of  milligrams  of  KOH  necessary 
to  saponify  1  grm.  of  fat  or  wax  completely.  The  determination  is  made  as  follows  :  1-5  to  2-2  grm.  of  the  filtered 
fat  is  weighed  into  a  150  to  200  c.c.  wide-necked  flask,  to  which  is  then  added  25  c.c.  of  seminormal  alcoholic 
KOH  solution  prepared  with  90  per  cent,  alcohol  and  also  25  c.c.  of  neutralised  alcohol.  The  mixture  is  then 
heated  for  15  to  20  minutes  in  a  reflux  apparatus  on  a  water-bath  previously  heated  to  boiling,  and,  while 
still  tepid,  is  titrated  with  seminormal  hydrochloric  acid  (not  sulphuric  acid,  which  would  precipitate  K2SO4), 
using  phcnolphthalein  as  indicator.  Multiplication  of  the  number  of  c.c.  of  seminormal  KOH  solution  actually 
consumed  in  the  saponiflcation  by  0-0301  gives  the  number  of  mgrms.  of  KOH,  which  is  calculated  for  1  grm. 
of  the  fat. 

Non-saponifiable  substances  (mineral  oils,  &c.)  added  to  fats  as  adulterants  can  be  detected  by  the  following 
qualitative  test  devised  by  Holde  :  two  drops  of  the  oil  are  boiled  for  one  minute  with  a  solution  of  a  piece  of 
caustic  potash  the  size  of  a  pea  in  5  c.c.  of  boiling  absolute  alcohol,  3  to  4  c.c.  of  water  being  afterwards  added 
to  the  liquid  ;  in  presence  of  as  little  as  1  per  cent,  of  non-saponiflable  compounds,  a  turbidity  is  produced.  Also 
a  benzene  solution  of  picric  acid  gives  a  red  coloration  with  fat  containing  1  per  cent,  of  mineral  oil. 

For  detecting  traces  of  neutral  fats  (non-saponifled)  in  pure  fatty  acids  of  commerce,  Geitel's  test  is  employed  : 
15  c.c.  of  ammonia  solution  are  added  to  a  solution  of  2  grms.  of  the  fatty  acids  in  15  c.c.  of  hot  alcohol.  Tur- 
bidity of  the  liquid  indicates  the  presence  of  much  neutral  fat.  If,  however,  the  liquid  remains  clear,  cold  methyl 
alcohol  is  poured  carefully  on  to  its  surface  ;  a  turbid  ring  is  formed  between  the  two  layers  of  liquid  in  presence 
even  of  traces  of  neutral  fats  (this  test  does  not  answer  with  palm  oil). 

The  addition  of  resin  to  fat  is  discovered  by  the  Liebermann-Storch-Morawski  test  applied  to  the  fatty  acids 
obtained  in  determining  the  Hehner  number  (see  p.  373) :  a  few  drops  of  cold  sulphuric  acid  of  50°  B4.  are  added 
to  a  well-cooled  solution  of  1  to  2  grms.  of  the  fatty  acids  (which  contain  the  resins)  in  1  c.c.  of  acetic  acid.  If 
traces  of  resin  (pine  or  colophony)  are  present,  an  intense  red  or  violet  coloration  forms  immediately  and  rapidly 
gives  way  to  a  brown  fluorescence  (presence  of  cholesterol  or  wool  fat  produces  a  reddish  brown  coloration, 
which  changes  to  blue  and  then  to  green). 


380 


ORGANIC    CHEMISTRY 


pressed  either  hot  or  cold,  although  sometimes  they  are  extracted  with  solvents. 
Vegetable  oils  are  extracted  from  the  disintegrated  seeds  by  pressing  them 
hot  or  by  treatment  with  suitable  solvents.  In  both  cases  they  are  refined 
by  a  series  of  mechanical  and  chemical  operations  which  will  be  described 
more  particularly  in  dealing  with  tallow,  butter,  and  olive  oil. 

The  statistics  are  given  later  for  each  separate  oil,  so  that  here  only  a  few 
general  data  are  needed  :  of  different  fats  (with  the  exception  of  lard),  Italy 
imported  254,000  quintals  in  1906  ;  197,000  in  1907  ;  279,000  in  1909  ;  and 
232,000  quintals  (of  the  value  of  £700,000)  in  1910,  in  addition  to  5900  quintals 
of  fatty  acids  (of  the  value  of  £16,600).  In  1910,  England  imported  123,150 
tons  of  tallow  and  stearin  of  the  value  of  £4,194,484. 

TALLOW  (ox  fat,  sheep  fat,  &c.,  but  not  hog's  fat)  melts  at  35°  to  37°,  contains 
75  per  cent,  of  stearin  and  palmitin  (in  equal  parts)  and  25  per  cent,  of  olein.  In  the 
crude  state,  as  it  comes  from  the  slaughterhouse,  it  is  incorporated  in  a  cellular  tissue 
and  contains  various  impurities,  such  as  blood,  skin,  &c.,  which  gradually  putrefy,  giving 
a  bad  odour  to  the  tallow.  To  prepare  the  real  fat  from  the  crude  tallow,  the  latter  is 
cut  up  in  suitable  machines  fitted  with. knives  and  is  then  melted  in  open  iron  or  copper 
boilers  provided  with  stirrers  and  heated  either  wholly  by  direct-fire  heat  or  partly  in 


FIG.  252. 


FIG.  253. 


this  way  (Fig.  252)  and  partly  by  injecting  direct  steam,  superheated  to  180°  to  200° 
through  the  tube,  D.  The  strongly  smelling  gases  evolved  arc  led  by  the  pipe,  a,  under 
the  hearth  and  there  burned.  The  clear,  molten  fat,  after  a  long  rest,  is  discharged  through 
the  tap,  E,  and  filtered  through  a  bag,  the  solid  fragments  of  cellular  membranes  and 
other  impurities  being  retained  by  a  perforated  double  bottom.  These  impurities,  while 
still  hot,  are  squeezed  in  a  press  such  as  that  made  by  C.  E.  Ro.st,  of  Dresden  (Fig.  253), 
being  placed  inside  the  perforated  cylinder,  a,  which  is  surrounded  by  the  jacket,  h,  and 
closed  by  the  cover,  6,  fixed  by  the  screws,  d  ;  the  pressure  is  exerted  underneath  on  a 
plate  raised  by  means  of  the  lever,  e.  The  pressed  residue  is  then  either  treated  with 
carbon  disulphide  to  recover  the  small  amount  of  fat  still  retained,  or  used  directly  as 
cattle-food.  A  powerful  press,  which  is  largely  used,  is  shown  in  Fig.  254. 

Fusion  of  Tallow  with  Acid  (d'Arcet  method).  This  method  increases  the  yield  and 
improves  the  flavour  of  the  tallow,  the  unpleasant  flavour  being  diminished.  It  is  carried 
out  in  the  Fouche  apparatus  (Fig.  255),  consisting  of  a  closed  boiler,  which  can  be  heated 
both  by  indirect  steam  circulating  through  a  coil  on  the  bottom  and  by  direct  steam 
issuing  from  a  perforated  pipe  passing  also  to  the  bottom.  100  kilos  of  tallow  are  mixed 
with  50  kilos  of  water  containing  1  kilo  of  sulphuric  -acid  of  66°  Be.,  the  whole  being 
heated  for  two  hours  at  105°  to  110°.  The  clear,  fused  fat  floats  on  the  surface  of  the 
acid  solution,  which  is  replaced  by  pure  water,  the  tallow  being  heated  and  mixed  with  the 
latter  by  means  of  direct  steam  ;  after  some  time,  the  washed  tallow  is  discharged  from 
a  lateral  tube — which,  inside  the  vessel,  is  free  and  floats — through  a  cloth  bag.  When 
this  acid  process  is  used,  the  solid  fragments  separated  cannot  be  used  for  feeding  cattle. 


REFINING    OF   TALLOW 


381 


Fusion  with  Alkali.  Evrard  heats  the  tallow  with  a  very  dilute  solution  of  sodium 
carbonate,  while  Rorard  treats  1000  kilos  of  the  tallow  with  200  of  water  containing  a 
kilo  of  caustic  soda,  the  mixture  being  then  melted  at  100°  in  the  Fouche  apparatus. 
The  alkaline  process  gives  a  diminished  yield  and  does  not  diminish  the  amount  of  pungent 
gases  evolved. 

Refining.  If  the  fusion,  especially  when  acid  is  used,  has  been  successfully  carried 
out,  refining  is  usually  unnecessary.  It  is,  however,  required  when  the  tallow  is  to  be 
used  for  food  or  for  fine  soaps  ;  that  employed  for  candles  is  sometimes  bleached.  In 
general,  it  is  heated  and  stirred  with  water  for  a  long  time  in  suitable  vats.  It  is  then 
left  at  rest  until  it  separates  from  the  water  and  is  filtered  through  a  cloth  bag  and  collected 
in  a  tank,  heated  outside  in  order  to  retard  solidification  and  give  time  for  any  further 
impurities  present  to  deposit. 

If  the  fused  tallow  is  allowed  to  cool  slowly  at  a  temperature  above  28°,  it  sets  to  a 
granular  mass,  as  crystals  of  stearin  and  palmitin  first  separate  ;  from  this  mass  the 
olein  is  more  easily  removed  by  subsequent  compression. 

Many  different  processes  have  been  suggested  for  the  bleaching  of  tallow,  but  the 
only  ones  deserving  of  mention  here  are  those  consisting  in  heating  with  animal  charcoal, 
bone-black,  and  fuller's-earth  (magnesium  hydrosilicate,  see  p.  77  and  vol.  i,  p.  529), 


Eiu.  254. 


FIG.  255. 


and  then  filtering,  and  those  in  which,  say,  1000  kilos  of  tallow  are  heating  with  a  solution 
containing  20  kilos  of  water,  10  of  concentrated  sulphuric  acid,  and  5  of  potassium 
dichromate  (or  60  kilos  of  concentrated  hydrochloric  acid  and  15  of  permanganate  at 
40°)  ;  after  stirring,  the  mixture  is  left  for  a  time  and  then  washed  several  times  with 
hot  water.  In  some  cases,  the  tallow  is  stirred  and  heated  to  40°  with  25  kilos  of  an 
aqueous  solution  containing  250  grms.  of  potassium  permanganate  and  250  grms.  of 
concentrated  sulphuric  acid,  and  well  washed  with  hot  water,  a  little  sodium  bisulphite 
being  finally  added.  Chlorine,  which  is  sometimes  used  for  vegetable  oils,  is  harmful 
to  animal  fats.  Excellent  results  have  been  obtained  recently  by  bleaching  with  sodium 
hydrosulphite  (vol.  i,  p.  465).  Certain  fats  can  be  well  bleached  at  80°  to  100°  with  1  to 
2  per  cent,  of  barium  peroxide,  which  is  added  gradually  and  with  continual  stirring.  Fats 
and  fatty  acids  are  sometimes  deodorised  by  treating  with  20  per  cent,  of  concentrated 
sulphuric  acid  at  30°  to  40°,  and  then  distilling  the  fatty  acids  under  reduced  pressure. 

The  purity  of  tallow  is  determined  by  the  analytical  methods  already  given  (see  also 
Table  on  p.  378)  and  for  industrial  purposes  the  solidification  temperature  of  the  fatty 
acids  obtained  by  the  Hehner  method  (see  p.  373)  is  measured  by  introducing  them  in 
the  fused  state  into  a  double-walled  test-tube  (best,  that  of  the  Tortelli  thermo-oleometer, 
p.  376)  and  stirring  with  a  thermometer  until  they  begin  to  turn  turbid.  The  tempera- 
ture then  ceases  to  fall  and  at  a  certain  moment  rises  (the  heat  of  solidification  being 
developed)  and  remains  constant  until  the  whole  mass  has  solidified  j  this  constant 
temperature  is  that  of  solidification  and,  for  good  tallow,  should  be  at  least  43°.  Adul- 
teration with  cotton-seed  oil  is  detected  by  Halphen's  reaction:  a  mixture  of  20  c.c.  of 


882  ORGANIC    CHEMISTRY 

the  fat,  20  c.c.  of  amyl  alcohol,  and  2  c.c.  of  a  1  per  cent,  solution  of  sulphur  in  carbon 
disulphide  is  boiled  in  a  test-tube  ;  after  about  ten  minutes  heating,  a  dark  orange  or 
red  coloration  will  appear  if  even  as  little  as  5  per  cent,  of  cotton-seed  oil  be  present. 
If  no  coloration  is  evident  after  the  lapse  of  ten  minutes,  a  little  more  carbon  disulphide 
may  be  added  and  the  heating  continued  ten  minutes  longer.  If  the  suspected  tallow, 
or  the  cotton-seed  oil  before  addition  to  the  tallow,  were  heated  to  200°  to  250°,  Halphen's 
reaction  would  not  be  given. 

The  greater  part  of  the  tallow  made  is  used  in  the  manufacture  of  soap  and  candles, 
but  an  appreciable  proportion  is  employed  in  margarine  factories  (see  below).  A  well- 
fattened  ox  may  give  as  much  as  100  kilos  of  crude  tallow. 

Continental  Europe  imports  large  quantities  of  tallow  from  America,  Australia,  and 
England.  The  price  varies  somewhat,  and,  while  in  1870  it  was  £4  to  £5  12s.  per  quintal, 
in  1884  it  was  67*.,  in  1885  56s.,  in  1886  44*.,  in  1888  53*.  Qd.,  in  1892  49*.,  and  in  1893 
54*.  ;  in  1906  the  price  on  the  Italian  markets  varied  from  56*.  to  61*.  Qd.,  in  1907  from 
65*.  to  72*.,  and  in  1908  from  60*.  to  65*.  6d. 

Germany  imported  6226  tons  of  tallow  in  1888  and  almost  11,000  tons  in  1891  (see 
later,  Importance  of  Melted  Tallow  for  Oleomargarine). 

In  1909  England  imported  110,000 -tons  of  tallow  and  stearin,  and  in  1910  123,150 
tons  (£4,194,484),  while  the  United  States  exported  8500  tons  in  1910  and  22,000  tons 
(£562,200)  in  1911. 

OLEOMARGARINE  and  MARGARINE  (Artificial  Butter).  The  oleomargarine 
obtained  from  tallow  serves  to  prepare  margarine  or  artificial  butter  by  churning  it  up 
with  milk.  It  is  also  used  to  some  extent  for  making  the  so-called  margarine-cheese  from 
separated  milk,  the  butter  being  replaced  by  oleomargarine,  which  is  incorporated  by 
means  of  emulsors. 

It  was  Napoleon  III  who,  on  account  of  the  rise  in  price  of  provisions  and  more 
especially  of  butter,  offered  in  1870  a  prize  for  the  discovery  of  a  cheap  fat  to  replace 
butter,  and  placed  at  the  disposal  of  the  inventor  a  large  works  'at  Poissy,  near  Paris, 
adapted  to  the  development  of  the  industry.  The  prize  was  awarded  in  1871  to  the 
Mege  Mouries  process  for  the  manufacture  of  oleomargarine  from  tallow  by  a  method 
which  is  almost  identical  with  that  used  at  the  present  day  (the  addition  of  sheep's 
stomach  to  render  soluble  the  cellular  membranes  enveloping  the  fat  has  now,  however, 
been  abandoned). 

As  a  rule,  oleomargarine  factories  are  situated  close  to  the  slaughterhouses,  so  that 
the  tallow  may  be  obtained  fresh  from  the  animals.  The  tallow  is  cooled  immediately 
by  washing  it  in  a  current  of  cold  water,  which  removes  the  blood  and  other  impurities, 
and  if  it  cinnot  bs  worksd  at  once  is  hung  in  separate  pieces  in  a  cold  chamber. 

The  tallow  is  then  cut  up  and  introduced,  with  one-fourth  of  its  weight  of  water  at 
55°,  into  a  vat  similar  to  that  used  for  the  melting  of  tallow  (see  p.  380),  but  nowadays 
the  heating  and  melting  are  effected  by  the  circulation  of  hot  water  at  60°  to  70°  instead 
of  steam,  so  as  to  avoid  scalding  the  mass.  The  latter  is  kept  slowly  stirred  and  a  couple 
of  hours  is  sufficient  time  to  melt  2000  kilos  of  tallow,  which  floats  on  the  water,  whilst 
the  bits  and  membranes  are  deposited  on  the  bottom  ;  this  separation  is  facilitated  by 
the  addition  of  2  per  cent,  of  salt,  previously  dissolved  in  water. 

After  the  mass  has  remained  at  rest  for  some  time,  all  the  impurities  settle  and  the 
molten  fat  is  removed  by  a  tap  connecting  inside  the  vat  with  a  free,  floating  tube 
which  gradually  falls  as  the  layer  of  fat  diminishes  ;  the  latter  is  collected  in  tinned, 
double-walled  tanks  surrounded  by  hot  water,  so  that  further  clarification  may  result 
on  long  standing.  The  fat  then  bears  the  name  premier-jus  and  is  mixed  in  small 
proportion  into  margarine,  while  the  remainder  is  poured  into  flat,  tinned  moulds 
holding  about  20  kilos  and  allowed  to  solidify  in  a  chamber  kept  at  a  temperature  of 
about  30°. 

The  semi-solid  mass  thus  formed  is  placed  in  cloths  and  squeezed — not  too  strongly — 
in  hydraulic  presses  (similar  to  those  used  in  making  stearic  acid  for  candles,  see  later) 
in  a  room  at  about  25°.  This  procedure  yields  about  45  per  cent,  of  a  solid  residue  of 
steirin  (for  candles)  mixed  with  a  little  olein,  and  a  liquid  product  (55  to  60  per  cent.) 
composed  of  55  per  cent,  of  triolein,  35  per  cent,  of  tripalmitin,  and  10  to  15  per  cent, 
of  tristearin  ;  this  is  oleomargarine,  which  assumes  an  almost  pasty  consistency  at  ordinary 
temperatures  and  has  a  yellow  colour  and  a  pleasant  odour  similar  to  that  of  butter. 


MARGARINE 


383 


: 


FIG.  256. 


It  is  used  in  some  cases  as  fat  for  cooking,  but  usually  it  is  converted  into  artificial 

butter. 

Oleomargarine  has  the  sp.  gr.  0-859  to  0-860  at  100°,  melts  at  33-7°,  has  the  Hehner 

number  (see  p.  373)  95-5,  the  Reichert-Meissl-Wollny  number  (see  p.  373)  0-4  to  0-9,  and 

the  iodine  number  (see  p.  375)  44  to  55. 

MARGARINE  (or  Artificial  Butter)  is  prepared  from  oleomargarine,  from  one-tenth 

to  one-fifth  of  sesame  or  arachis  or  even  cotton-seed  oil  being  added  for  the  lower  qualities 

(in  America  maize  oil  is  used).  In  some  countries  no 
milk  is  now  used,  attempts  being  made  to  flavour  the 
oleomargarine  directly  with  certain  strongly  flavoured 
cheeses  prepared  for  this  express  purpose,  or  with 
butyric  acid  or  its  homologues,  or  with  a  special 
flavouring  placed  on  the  market  under  the  name  of 
margol. 

It  is  necessary  that  artificial  butter,  when  fried, 
should  give  the  same  smell  as  natural  butter,  and 
this  result  is  attained  partly  by  adding  a  little  choles- 
terol (Ger.  Pat.  127,376)  to  the  milk  used  to  render 
the  oleomargarine  pasty.  Margarine  is  also  required 
to  brown  and  froth  like  natural  butter  when  fried, 
and  this  is  attained  by  adding  about  2  per  cent,  of  egg 
yolk  (Ger.  Pat.  97,057)  or  0-2  per  cent,  of  lecithin  (a 
constituent  of  yolk  of  egg  ;  Ger.  Pat.  142,397)  and  a 
small  quantity  of  glucose,  while  it  has  also  been  pro- 
posed to  add  a  little  powdered  casein,  egg-yolk  and 

pasteurised  milk-cream  (Ger.  Pat.  170,163). 

The  yellow  colour  of  commercial,  natural  butter  is  imitated  by  the  addition  of  a  little 

butyroflavine  (dimethylaminoazobenzene)  dissolved  in  sesame  or  cotton-seed  oil   (placed 

on  the  market  by  the  Chemical  Factory  of  Thann  and  Miilhausen). 

In  the  manufacture  of  first-quality  margarine,  the  fats  to  be  mixed  (e.g.  for  summer 

margarine,  600  kilos  of  oleomargarine,  SO  kilos,  of  premier-jus  (see  above),  and  60  kilos 

of  sesame  oil  ;    for  winter  margarine,  the  premier-jus  is  replaced  by  a  similar  quantity 

of  sesame  oil)  are  first  melted  separately  at  40°  to  45°.     For  inferior  margarines,  less 

oleomargarine,  more  premier -jus,  and  a  certain  amount  of  cotton-seed  oil  are  used.     Half 

of  the  molten,  homogeneous  fat  is  introduced  into 

a  churn  (that  of  H.  Grasso,  of  Hertogenbosch, 

Holland,  Fig.  256,  gives  good  results)  contain- 
ing  300   litres  of  milk1  previously  churned  to 

the  clotting -point  and  mixed  with  50  grms.  of 

colouring  solution.       The  churn  has  a  closely 

fitting  lid   and  is  jacketed   so  that  it  can   be 

surrounded  with  water  at  35°  to  45°  ;  it  is  fitted 

with  stirrers   (120   revs,   per   minute)  and    the 

inner    surface    is     thickly    tinned.      After     10 

to    15    minutes    churning,    the    remaining   half 

of  the  milk  and  molten  fat  is  introduced,  the 

churning  feeing  continued  for  a  further  period 

of  20  to  25  minutes.     When  the  mass  has  reached  a  temperature  of  30°  to  45°  (better 

quality  but  diminished  yield  is  obtained  at  30°),  it  is  allowed  to  flow  into  a  shallow 

double-walled  vessel  cooled  by  the  circulation  of  water  at  0°  to  2°,  and,  as  it  flows,  it  is 

washed  with  a  powerful  jet  of  water  at  2°  and  is  constantly  mixed  with  wooden  blades. 

The  wash-water  is  then  run  off  and  the  hardened,  disintegrated  mass  left  overnight  so 

that  the  wash-water  may  separate  better.     A  homogenising  machine  of  the  Schroeder 

1  For  the  finer  margarines,  cream  is  used,  but  for  ordinary  varieties  skim-milk  from  the  separators  is  employed. 
In  all  cases,  in  order  to  obtain  a  margarine  which  will  keep,  even  in  summer,  the  milk  is  pasteurised  at  55°  to 
60°  and  then  subjected  to  slight  acid  fermentation  with  pure  cultures  of  bacteria,  which  are  sold  by  butter  manu- 
facturers. 

The  cooled  milk  is  kept  in  clean,  closed  vessels  in  a  cool  place  and  is  consumed  as  soon  as  possible  so  as  to 
avoid  contamination.  It  may  be  centrifuged  after  pasteurising  and  cooling.  If  it  is  not  rendered  acid,  the 
milk,  and  also  the  butter  obtained  therefrom,  keep  badly  and  do  not  incorporate  well  with  the  other  fats. 


FIG.  257. 


384 


ORGANIC    CHEMISTRY 


type  has  been  introduced  recently,  and  this  allows  of  continuous  working  and  effects 
a  far  more  perfect  mixing  of  the  fats  and  milk,  while  it  yields  a  more  aromatic  and  stable 
product. 

To  complete  the  separation  of  the  whey  and  washing-water,  and  to  obtain  a  homo- 
geneous pasty  mass,  the  cold  mixture  is  introduced  gradually  into  an  ordinary  butter 
kneader  (Fig.  257)  with  rotating  base,  this  being  situate  in  a  cold  chamber.  After  passing 
under  the  grooved  cone  eight  or  ten  times,  the  mass  is  collected  in  blocks,  which  are  left 
for  24  hours.  If  it  is  desired  to  mix  a  little  cream  or  the  allowed  quantity  of  water 
(10  to  12  per  cent.)  into  the  mass,  the  latter  is  introduced  into  the  Werner-Pfleiderer 
kneader  (similar  to  that  used  for  kneading  bread),  which  can  easily  be  reversed  so  as  to 
expel  the  excess  of  liquid  and  finally  the  paste  itself  (Fig.  258). 

The  margarine  thus  obtained  is  made  up  into  cakes  by  means  of  suitable  moulds 
bearing  the  trade  mark  and  is  then  wrapped  in  parchment-paper  previously  disinfected 
in  brine.  In  some  countries  this  paper  is  marked  with  coloured  stripes  to  allow  the  public 
readily  to  distinguish  margarine  from  butter  ;  and  in  all  countries  it  is  obligatory  to 
exhibit  margarine  for  sale  in  shops  with  a  placard  which  distinguishes  it  from  butter. 
In  Germany  and  Austria  the  law  requires  margarine  to  be  prepared  with  at  least  10  per 

cent,  of  sesam£  oil  and  not  more  than  10  per 
cent,  of  butter  ;  by  this  means,  the  detection 
of  butter  adulterated  with  margarine  is  facili- 
tated, as,  owing  to  the  sesame  oil  present,  it 
gives  the  Baudouin  reaction  for  furfural.1  If 
more  than  10  per  cent,  of  butter  is  added  to 
margarine  the  Reichert-Meissl-Wollny  number 
(see  p.  373)  exceeds  2-5. 

Normal  margarine  contains  8  to  9  per  cent, 
of  water  and  1  to  2  per  cent.  NaCl,  and  has  the 
saponification  number  193  to  203  (coco-nut  fat 
raises  this  number  to  220  and  the  Wollny  nuni  ber 
to  5)  and  the  iodine  number  52  to  60. 

The  experiments  of  Liihrig  (1900)  have 
shown  with  certainty  that  margarine  is  digested 
by  man  as  well  as  butter. 

The  consumption  of  margarine,  which  costs 
little  more  than  half  as  much  as  butter,  is  con- 
tinually increasing  in  all  countries.  Germany 
possessed  55  factories  in  1886  and  83,  employ- 
ing 1555  workmen,  in  1895;  and  in  1899  pro- 
duced 91,000  tons  (worth  more  than  £3,800,000)  of  first- and  second-quality  margarines, 
55,000  tons  of  animal  fats,  23,000  of  vegetable  fats  and  oils,  53,000  of  skim-milk,  and  4800 
of  salt  being  employed.  Germany  imported  28,500  tons  of  oleomargarine  in  1906  and  about 
23,000  tons  in  1909,  and  exported  297  tons  of  artificial  butter  in  1906  and  525  in  1909. 
In  North  Germany,  margarine  of  first  quality  is  used,  but  in  the  South  margarine  without 
butter  and  without  milk. 

In  1907  there  were  31  margarine  factories  in  Norway.  Thirty-seven  factories  existed 
in  the  United  States  in  1886,  and  the  output,  which  was  less  than  6000  tons  in  1902,  rose 
to  45,000  tons  in  1908  and  70,000  in  1910  (almost  all  not  coloured),  the  exports  being 
1550  tons  in  1910  (almost  all  coloured).  In  1910-1911  the  output  in  the  United  States 
fell  to  about  65,000  tons.  In  Denmark  22  factories  produced  30,000  tons  in  1909  and 
34,300  tons  in  1910,  when  the  exports  amounted  to  1100  tons.  England  imported  1650 
tons  of  oleomargarine  in  1909  and  4050  tons  in  1910  and  exported  3295  tons  in  1909  and 
8138  tons  (£206,360)  in  1910.  The  principal  exportation  from  the  United  States  consists 
of  the  prime  material,  oleo  oil,  which  is  largely  used  in  other  countries  for  preparing  the 
different  margarines  or  artificial  butters  ;  in  1910,  50,000  tons  of  this  oil  (of  the  value  of 

1  10  c.c.  of  margarine,  filtered  into  a  separating  funnel,  are  shaken  for  half  a  minute  with  10  c.c.  of  HC1  (sp.  gr. 
1-125).  If  the  acid  is  coloured  red,  it  is  decanted  off  and  the  residue  shaken  with  a  fresh  quantity  of  the  acid. 
After  removal  of  the  acid,  5  c.c.  of  the  fat  are  poured  into  a  graduated  cylinder  with  a  ground  stopper,  where 
they  are  shaken  with  10  c.c.  of  HC1  (sp.  gr.  1-19)  and  0-1  c.c.  of  1  per  cent,  solution  of  furfural  in  alcohol  (absolute) 
for  half  a  minute.  If,  after  standing,  the  layer  of  acid  shows  an  intense  red  coloration,  the  margarine  contained 
the  required  quantity  of  sesame  oiL  This  reaction  has,  however,  been  criticised  as  being  in  some  cases  indecisive. 


Flo/  258. 


BUTTER  385 

£2,360,000)  were  exported,  and  in  1911,  77,000  tons  (of  the  value  of  £3,132,600).  In  1907, 
Sweden  produced  15  millions  of  kilos,  and  in  Holland  there  are  over  100  factories.  The 
total  output  of  Holland  and  Belgium  in  1910  was  65,000  tons  (of  the  value  of  £3,600,000), 
about  48,000  tons  being  exported.  In  Paris,  more  than  30  tons  of  margarine  were  manu- 
factured per  day  as  early  as  1875.  In  Italy,  the  first  factory,  that  of  Regondi  and 
Chierichetti,  was  erected  in  1874  at  Milan,  with  branches  in  Rome  and  Tuscany  ;  even 
in  1888  this  firm  produced  almost  400,000  kilos  of  margarine,  and  at  the  present  time, 
as  a  company  (Chierichetti  and  Torriani),  it  still  occupies  the  premier  position.  A 
considerable  amount  of  suspicion  was  removed  from  the  industry  in  Italy  as  the  result 
of  a  valuable  report  prepared  for  the  Royal  Italian  Society  of  Hygiene  by  Korner  and 
Gabba  in  1888,  and  in  1911  the  consumption  (largely  for  adding  to  butter)  reached  about 
8000  tons  ;  the  importation  of  artificial  butter  was  121  tons  in  1908  and  64  tons  in  1910, 
while  the  amount  exported  rose  to  216  tons  in  1908  and  258  tons  in  1910. 

Owing  to  the  high  price  of  tallow  in  recent  years,  attempts  have  been  made  to  prepare 
margarine  by  the  addition  of  cocoa-butter  in  the  kneader,  after  complete  expulsion  of 
the  water  (so  as  to  prevent  rancidity).  There  is  now  on  the  market  margarine  which 
bears  the  name  of  cunerol  (or  kunerol),  and  is  made  exclusively  from  cocoa-butter,  kneaded 
and  treated  with  a  saline  solution  of  yolk  of  egg  (instead  of  milk).  Under  the  name 
buttirol,  L.  Annoni  prepared,  in  1909,  an  artificial  butter  by  emulsifying  oleomargarine 
or  other  fat  with  milk  and  separating  the  artificial  butter  by  centrifugation  after  slight 
fermentation. 

BUTTER  is  the  fat  obtained  from  milk,1  in  which  it  occurs  emulsified  in  small  drops, 
which  separate  at  the  surface  on  standing,  or,  better,  on  centrifugation  in  a  separator 
of  the  de  Laval  type  (Fig  260). 

1  Milk  is  a  liquid  secreted  by  female  mammals  after  parturition,  and  serves  as  the  first  nutriment  of  the 
offspring.  But  that  of  certain  animals  (cows,  goats,  &c.)  has  been  largely  used,  from  the  earliest  times,  for 
feeding  infants  and  adults,  and  for  the  preparation  of  cheese,  casein,  milk-sugar,  &c.  The  mean  daily  consump- 
tion of  cows'  milk  per  head  is  about  300  grms.  in  England,  450  in  Canada,  600  in  Holland,  260  in  Paris,  600  in 
Munich,  and  150  in  London.  The  supply  of  milk  to  large  towns  constitutes  a  serious  problem,  since,  for  example, 
Genoa  consumes  400  hectols.  per  day,  Turin  600,  Milan  1000,  Berlin  7400,  Paris  8300,  and  New  York  15,000. 
In  1908  the  United  States  exported  £3,200,000  worth  of  condensed  milk  to  China,  Japan,  the  Philippines,  Corea, 
Kussia,  Africa,  and  Mexico.  The  number  of  cows  in  France  in  1909  was  7,336,000,  and  the  yield  of 
milk  132,000,000  hectols.  Hungary  in  1909  produced  26,000,000  hectols.  of  milk.  In  1903  Australia  obtained 
from  1,300,000  cows  about  16,000,000  hectols.  of  milk,  500,000  quintals  of  butter  (one-third  being  exported), 
and  60,000  quintals  of  cheese  (barely  one-fifth  exported).  In  the  United  Kingdom  4,000,000  cows  produced 
in  1909  about  72,000,000  hectols.  of  milk.  In  1910  Norway  produced  10,000,000  hectols.  of  milk. 

The  mean  composition  of  the  milk  obtained  by  complete  milking  is  found  from  some  thousands  of  different 
analyses  to  be  as  follows  :  water,  87-22  per  cent. ;  fat,  3-62  per  cent.  ;  nitrogenous  substances  (casein  and  a  little 
albumin),  3-66  per  cent. ;  milk  sugar,  4-82  per  cent. ;  and  mineral  matter,  0-68  per  cent.  The  casein  forms  a 
kind  of  colloidal  solution,  which  holds,  In  an  emulsified  and  suspended  condition,  fat-drops  of  varying  magnitude 
(diameter,  0-01  to  0-0016  mm.).  Casein  in  milk  occurs,  indeed,  in  the  form  of  a  non-reversible  hydrosol  (gee 
vol.  i,  p.  105)  and  its  coagulation  by  acids  or  heat  can  be  retarded  or  prevented  by  the  presence  of  a  reversible 
colloid  (protecting  colloid,  like  gelatine  or  gum).  In  cows'  milk  the  relation  between  casein  (non-reversible)  and 
albumin  (reversible)  is  3-02  :  0-53,  whilst  in  human  milk  this  relation  is  0-75  : 1-00  ;  in  human  milk,  then,  there 
is  abundance  of  albumin  (reversible)  and  the  coagulability  is  eight  times  less  than  with  cows'  milk.  These 
relations  explain  the  different  nutritive  effects  of  the  two  milks  on  infants. 

Boiled  milk  can  be  distinguished  from  raw  milk  as  it  no  longer  contains  reductase  or  catalase  (see  p.  112) ; 
also  oxidation  of  the  whey  with  a  little  hydrogen  peroxide  and  treatment  with  pyramidone  at  60°  yields,  with 
raw  milk,  a  violet  coloration,  while  that  of  boiled  milk  gives  no  coloration.  The  sugar  and,  partly,  the  salts 
are  found  in  the  aqueous  solution  composing  the  whey.  Milk  has  an  acid  and  an  alkaline  reaction  (amphotf.ric 
reaction)  at  the  same  time,  owing  to  the  presence  of  primary  (acid)  and  secondary  (alkaline)  phosphates.  The 
natural  acidity  of  milk  is  due,  not  to  lactic  acid,  but  to  phosphates,  carbon  dioxide,  citric  acid,  Ac. 

From  milk  defatted  by  centrifugation  (skim-milk,  containing  less  than  0-3  per  cent,  of  fat),  casein  for  making 
dierse  and  for  industrial  purposes  is  separated  by  addition  of  rennet  (from  the  mucous  membrane  of  the 
fourth  stomach  of  young  calves),  which  induces  clotting  owing  to  the  enzyme  it  contains.  Coagulation,  with 
formation  of  lactic  acid  (increase  from  3°  to  15°  of  acidity),  is  also  caused  spontaneously  in  24  to  48  hours 
by  adding  a  dilute  acid  and  keeping  at  55°  to  60°  ;  the  casein  probably  exists  as  calcium  salt  (1-55  per  cent.  CaO), 
which  is  decomposed  by  acids,  the  increase  in  the  amount  of  soluble  calcium  salts  favouring  the  separation  of 
the  casein.  This  casein,  separated  in  the  hot  and  pressed,  gradually  undergoes  fermentation  and  conversion 
into  Cheese.  The  latter  may  be  either  whole-milk  cheese  or  filled  cheese,  prepared  from  milk  the  fat  of  which 
has  been  partially  or  completely  removed  and  replaced  by  margarine  or  lard.  Copper  vessels  turn  the  cheese 
green  on  exposure  to  the  air,  and  to  avoid  this,  all  the  operations  are  carried  out  in  vessels  of  wood,  zinc,  tinplate, 
or  tinned  copper  (Besana),  although,  according  to  Fascetti,  traces  of  dissolved  copper  are  advantageous  in  cheese 
since  they  retard  lactic  fermentation ;  the  latter  author  suggests,  however,  the  addition  of  hydrogen  peroxide, 
which  has  the  advantages  of  the"  copper  without  its  disadvantages.  To  avoid  secondary  fermentations  during 
maturation  and  prevent  the  swelling  and  spoiling  of  the  cheese — which  otherwise  frequently  occur — certain 
selected  ferments  are  initially  added  under  favourable  conditions  (Gorini,  1905),  or  attention  is  paid  (Soncin!, 
1910)  to  the  chemical  surroundings  in  which  maturation  takes  place  (see  p.  126). 

In  1906  there  were  in  Italy  3835  dairies  employing  15,000  workpeople,  and  the  exports  amounted  to :  butter 

to  the  value  of  £440,000  and  180,000  quintals  of  cheese  ;  in  1909,  186,500  quintals  of  cheese  were  exported,  53,500 

being  prepared  from  ewes'  milk.    The  exportation  of  gorgonzola,  &c.,  was  72,000  quintals  in  1907 ;   66,500  in 

1908  ;  5?,900in  1909  ;  and  78,860  quintals  (of  the  value  of  £600,000)  In  1910.     Italy  also  imported  the  following 

II  25 


386 

After  filtration  through  cotton-wool  or,  better,  after  a  brief  centrifugation  to  remove 
suspended  impurities,  the  milk  passes,  while  still  tepid,  to  the  chamber  of  the  centrifuge, 
A,  mounted  on  the  axle,  S,  actuated  by  a  pulley  which  is  not  shown  in  the  figure  (260) 

quantities  of  hard  cheese  :  from  Switzerland,  47,400  quintals  (and  28,000  from  other  countries)  in  1908  ;  48,370 
(28,700  from  other  countries)  in  1909  ;  and  39,700  quintals  (of  the  value  of  £320,000)  in  1910  ;  in  addition  to 
25,400  quintals  (costing  about  £240,000)  from  other  countries,  especially  European  Turkey. 

In  1910  England  imported  cheese  to  the  value  of  £6,000,000  (£5,000,000  from  Canada  alone),  and  butter  to  the 
value  of  £8,000,000,  that  from  Russia  amounting  to  £3,200,000  and  that  from  Australia  to  £4,800,000. 

Holland  produced  790,000  quintals  of  cheese  in  1906,  while  Hungary  imported  about  13,000  quintals  in  1909 . 
After  the  cheese  has  been  separated  from  the  skim-milk,  further  boiling  and  coagulation  of  the  latter  yield 
the  dissolved  albumin  (ricotta),  the  whey  finally  remaining  being  used  either  as  food  for  calves  or  pigs  or  for  the 
manufacture  of  milk-sugar  (see  later,  Lactose).  Skim-milk  is  used  in  some  countries  for  the  preparation  of  cheap 
and  highly  nutritious  bread  or  of  kephir  (see  p.  160),  while  in  recent  years  it  has  been  utilised  for  miking  milk- 
powder  by  evaporating  it  rapidly  on  a  large  rotating  cylinder  of  metal  heated  by  steam  and  in  some  cases  enclosed 
in  an  evacuated  chamber.  A  knife  is  arranged  to  detach  the  dry  powder,  which  falls  into  a  box.  The  milk  may 
also  be  concentrated  to  some  extent  in  vacuo  and  then  pulverised  with  hot  air ;  in  some  cases  the  water  is  removed 
from  the  milk  by  freezing  and  continual  stirring,  the  residue  being  subsequently  dried.  Being  deprived  of  fat, 
this  powder  does  not  become  rancid,  and  if  a  little  calcium  saccharate  is  added,  it  dissolves  and  gives  skim-milk 
on  dilution  with  water.  Milk-powder  is  also  used  by  pastrycooks.  \Vhen  casein  is  to  be  separated  for  industrial 
purposes,  it  is  obtained  pure  by  treating  the  skim-milk  at  50°  to  60°  with  a  current  of  sulphur  dioxide  (Soncini 
and  Todtenhaupt,  Ger.  Pat.  184,300) ;  it  is  dried  in  a  stream  of  hot  air  or,  to  obtain  it  in  a  more  soluble  state, 
in  a  vacuum,  while,  if  a  highly  pure  product  is  required,  it  is  dissolved  in  alkali  and  reprecipitated  with  nitric- 
acid  (it  then  has  the  percentage  composition  :  C,  52-96  ;  H,  7-30 ;  N,  15-60  ;  O,  22-54  ;  S,  0-76  ;  P,  0-84). 
Besides  being  soluble  in  alkalis  and  borax,  casein  dissolves  in  solutions  of  potassium  iodide,  sodium  thiocyanatc, 
sodium  phosphate,  &c.  When  dry  and  powdered,  it  can  be  used  for  certain  concentrated  food  products  (plasmon, 
nutrose,  tropon,  &c.),  for  dressing  tissues,  for  greased  paper  (rendered  soluble  with  sodium  carbonate  or  boratc) 
and  for  making  material  similar  to  bone  or  celluloid  by  compressing  it  when  hot  and  hardening  it  with  form- 
aldehyde. Oallatite  and  lactite  are  prepared  in  a  similar  way. 

In  1907  Italy  imported  1305  quintals,  and  in   1910,  1536  quintals  (worth  £5840),  the  exportation  in  this 

year  being  1937  quintals  (of  the  value  of  £9440).    In  1909  Germany 
imported  28,400  and  exported  3950  quintals  of  casein. 

ANALYSIS  OF  MILK.  Milk  being  a  valuable  nutrient  for 
man,  and  being  also  easy  to  adulterate,  it  is  usually  analysed 
chemically  to  test  its  genuineness.  Milk  from  cows  of  different 
breeds  and  districts  varies  within  relatively  narrow  limits,  but,  in 
doubtful  cases  of  adulteration,  a  mixture  of  the  total  milk  of  all 
the  cows  of  the  herd  from  which  the  suspected  sample  is  furnished 
is  also  analysed.  The  specific  gravity  is  measured  with  a  hydro- 
meter or  a  Westphal  balance  at  15°  (see  vol.  i,  p.  73  el  seq.) ;  for 
natural  milk  it  varies  between  1-0295  and  1-0335,  and  for  separated 
milk  from  1-033  to  1-036,  while  if  much  water  has  been  added  it  is 
below  1-0295.  The  value  of  the  specific  gravity  is  not  sufficient  to 
prove  watering,  as  this  value  is  sometimes  maintained  unchanged 
by  simultaneous  removal  of  cream  and  addition  of  water.  In  such 
a  case,  use  may  be  made  of  the  specified  gravity  of  the  whey,  which  is 
never  less  than  1-027  with  pure  milk.  Watering,  even  to  the 
FlG.  259.  extent  of  only  5  per  cent.,  is  also  readily  detectable  by  the  cryo- 

scopic  method  examined  in  1898  by  G.  Cornalba  (for  fresh,  non-acid 

milks  free  from  antiseptics,  the  cryoscopic  point  varies  from  0-54  to  0-56)  or  by  observing  the  whey  in  theZeiss  butyro- 
refractometer  (see  p.  375).  The  latter  method  was  proposed  recently  by  Ackermann,  who  prepares  the  whey 
rapidly  by  clotting  30  c.c.  of  milk  with  0-25  c.c.  of  a  calcium  chloride  solution  of  sp.  gr.  1-1375,  heated  for  fifteen 
minutes  on  the  water-bath,  cooled  to  17-5°,  and  the  serum  separated  by  decantation  ;  the  reading  on  the  Zeiss 
scale  is  38-8  to  40  for  pure  milk,  37-7  for  milk  +  5  per  cent,  of  water,  36-7  with  10  per  cent.,  34-8  with  20  per 
cent.,  33-3  with  30  per  cent.,  32  with  40  per  cent.,  &c.  G.  Cornalba  (1908)  holds  that  genuine  milk  contains  at 
least  6  per  cent,  of  soluble  substances  (i.e.  dry  residue  less  fat  and  casein),  every  0-2  per  cent,  less  than  this  amount 
indicating  5  per  cent,  of  added  water.  Since  natural  milk  does  not  contain  nitrates,  which  are,  however,  present 
in  nearly  all  waters,  watering  can  also  be  detected  by  testing  the  milk  for  nitrates  in  the  same  way  as  wine  is 
tested  (see  p.  157).  Watered  milk  appears  slightly  blue  when  compared  with  genuine  milk. 

The  total  residue  and  ash  are  determined  by  evaporating  5  grms.  of  milk  with  a  drop  of  acetic  acid  in  a  platinum 
dish,  drying  in  an  oven  at  105°,  and  weighing  ;  the  dry  residue  thus  obtained  is  then  heated  to  redness  until  com- 
pletely incinerated  and  weighed  ;  the  ash  is  used  for  the  detection  of  borax  or  sodium  bicarbonate. 

Genuine  milk  has  not  less  than  12  per  cent,  of  dry  residue,  or,  subtracting  the  amount  of  fat,  not  less  than 
9  per  cent.  The  dry  residue  (r)  may  also  be  calculated  from  the  specific  gravity  (s)  and  the  percentage  of  fat  (y) 

by  Fleischmann's  formula  :  T  =  l-Zg  +  2-665  100a~100. 

s 

Determination  of  Fat.  This  is  usually  made  with  the  Gerber  butyrometer  (Fig.  259).  Into  a  special  wide- 
mouthed  flask  with  a  long,  narrow,  graduated  neck  are  pipetted  10  c.c.  of  concentrated  sulphuric  acid  (sp.  gr. 
1-825),  1  c.c.  of  amyl  alcohol,  and  11  c.c.  of  milk,  which  are  allowed  to  flow  gently  down  the  side.  The  flask  is 
then  tightly  closed  with  a  rubber  stopper,  wrapped  in  a  cloth  and  shaken  rapidly  and  vigorously  ;  the  flask  with 
the  pink  or  red  liquid  is  immersed  for  six  or  seven  minutes  on  a  water-bath  at  65°  to  70°  and  then  centrifuged 
on  a  flat  plate,  being  arranged  radially  in  clips  with  the  mouth  towards  the  circumference.  After  a  few  minutes 
centrifugation,  the  fat  is  separated  from  the  acid  casein  solution  and  the  percentage  of  fat  *by  weight  is  read  off 
on  the  graduated  neck  of  the  flask  after  the  latter  has  been  left  for  a  few  minutes  on  the  water-bath. 

The  official  method — which  is  used  rarely  and  only  in  cases  of  dispute — of  estimating  fat  is  that  of  Soxhlet,  and  is 
based  on  the  density  of  the  ethereal  solution  of  the  fat  extracted  from  the  milk  after  rendering  alkaline.  In  nearly  all 
countries  it  has  been  established  that  a  natural  milk,  obtained  by  milking  completely  a  number  of  cows,  contains 
as  a  rule  not  less  than  3  per  cent,  of  fat,  in  very  rare  cases  2-9  per  cent.,  and  more  frequently  3-5  per  cent. 

If  the  specific  gravity  (»)  and  the  dry  residue  (r)  of  a  milk  are  known,  the  fat  (y)  that  it  should  contain  is 

deduced  from  Fleischmann's  formula  :  g  =  0-833  r  —  2'22  ^10°  *  ~  100). 


COMPOSITION    OF    BUTTER 


387 


and  which  rotates  several  thousands  (6  to  7)  of  times  per  minute.  In  this  manner  the 
skim-milk  is  expelled  to  the  periphery  and  carried  off  by  the  tube,  b,  into  the  collecting 
plate,  Be,  whilst  the  lighter  cream  rises  and  is  discharged  by  the  channel,  e,  into  the 
collector,  Cf.  These  separators  easily  treat  10  hectols.  of  milk  per  hour.  The  cream 
that  separates  is  agglomerated  into  small  lumps  of  butter  by  churning  (see,  for  instance, 
Fig.  256,  on  p.  383),  kneading,  and  so  on,  just  as  with  margarine.  To  obtain  a  butter 
that  will  keep,  however,  the  cream  is  subjected  to  pasteurisation  and  acidification  (see 
Note  on  p.  383),  the  butter  being  worked  with  water  that  has  been  sterilised,  for  instance, 
by  ozone  or  ultra-violet  rays.  The  flavour  of  butter,  which  was  formerly  regarded  as 
due  to  the  esterification  of  the  fatty  acids,  seems  to  result  from  the  fermentation  of  lactose 
and  the  formation  of  aldehydes. 

The  proportions  of  the  various  fatty  acids  entering  into  the  composition  of  the  glycerides 
of  butter  are  as  follow :  stearic,  7  to  11  per  cent.  ;  palmitic,  14  to  18  per  cent.  ;  myristic, 
11  per  cent,  or  more  ;  lauric,  14  to  16  per  cent.  ;  oleic,  25  to  30  per  cent.  ;  higher  un- 
saturated  acids,  4  to  5-7  per  cent.  ;  also  the  volatile  acids,  butyric,  caproic,  caprylic,  and 
capric  ;  further,  small  proportions  of  acetic,  arachic,  and  hydroxy-acids,  cholesterol, 
phytosterol,  lecithin,  and  a  yellow  colouring-matter  ;  winter  butter  is  less  yellow  than 
that  of  summer  (green  feeding  of  the  cows-).  Unlike  other  fats,  butter  contains  a  mixed 
palmito-oleo -butyric  glyceride,  CgH^QeHg^aXCVsHgaOaXC.^.^). 

Also,  in  comparison  with  all  other  fats,  butter  contains  a  large  quantity  of  volatile 
acids  soluble  in  water. 

Commercial  butter  should  contain  not  more  than  18  per 
cent,  of  water  (or  16  per  cent.  +  2  per  cent,  of  salt)  and  at 
least  80  per  cent,  of  pure  fat. 

In  judging  of  the  purity  of  butter,  reference  should  fee 
made  to  the  constants  given  in  the  Table  on  p.  378  and 
to  what  has  been  said  on  pp.  373  and  375  with  respect  to 
the  soluble  volatile  acids  and  to  the  bu tyro -refractome trie 
reading,  which  should  have  the  following  values  at  different 
temperatures  :  41-5  at  45°,  43-6  at  43°,  43-7  at  41°,  44-7 
at  39°,  45-9  at  37°,  47  at  35°,  48-1  at  33°,  49-2  at  31°,  50-3 
at  29°,  51-4  at  27°,  and  52-5  at  25°. 

The  most  certain  method  of  detecting  adulteration  of 
butter  with  coco-nut  oil  is  by  determining  the  volatile 
fatty  acids  insoluble  in  water  (Polenske  number).1 

Adulteration  with  margarine  is  readily  detected  by  the  content  of  aggregated  crystals 
which  are  observed  under  the  microscope  in  polarised  light  or,  better,  in  light  which  has 
previously  passed  through  a  selenite  plate.  Fresh,  non-melted  butter  does  not,  indeed, 
yield  crystals,  but  old  and  rancid  or  melted  butter  does  give  them,  so  that,  in  this  case, 
the  test  is  invalid. 

The  determination  of  water,  fat,  solids  not  fat  (casein,  lactose,  and  mineral  salts)  can 
be  simply  carried  out,  according  to  Fahrion  (1906),  as  follows  :  in  a  platinum  crucible, 
tared  together  with  a  glass  rod,  are  weighed  2-5  to  3  grms.  of  butter,  which  is  then  heated 
over  a  small  flame  and  stirred  until  it  is  melted  and  clear  ;  reweighing  gives  the  proportion 

1  Polenske  (1904)  showed  that  coco-nut  oil  contains  a  high  and  constant  proportion  of  volatile  fatty  acid 
insoluble  in  water,  whilst  butter  contains  very  little  of  these.  If  the  Polenske  number  (or  new  butter-value)  is 
expressed  in  c.c.  of  decinonnal  KOH  necessary  to  neutralise  the  insoluble  volatile  acids  contained  in  5  gnus, 
of  the  fat,  its  value  is  16-8  to  17-8  for  coco-nut  oil  and  1-5  to  3  for  pure  butter.  The  Reichert-Meissl-Wollny 
number  and  the  Polenske  number  may  be  determined  by  a  single  operation,  the  butter  being  saponified  in  the 
following  manner  (Leffmann  and  Beam) :  5  grms.  of  the  filtered  butter,  together  with  20  grms.  of  glycerine  and 
2  c.c.  of  caustic  soda  solution  (100  NaOH  to  100  H2O),  are  placed  in  a  flask  of  about  300  c.c.  capacity,  thia 
being  heated  with  a  naked  flame.  After  5  to  8  minutes  boiling,  the  water  evaporates,  frothing  ceases,  and  the 
mixture  becomes  clear,  the  heating  being  then  continued  for  a  few  minutes  longer.  When  the  liquid  has  cooled 
to  80°  to  90°,  90  c.c.  of  water  at  80°  are  added,  a  clear  and  almost  colourless  solution  of  the  soap  formed  being 
thus  obtained.  To  this  solution,  heated  nearly  to  boiling,  are  added  50  c.c.  of  dilute  sulphuric  acid  (25  c.c.  of 
the  concentrated  acid  in  a  litre)  and  J  grm.  of  powdered  pumice,  the  volatile  acids  being  then  distilled  so  that 
110  c.c.  are  collected  in  19  to  21  minutes  in  an  apparatus  corresponding  exactly  with  that  shown  in  Fig.  248 
on  p.  373. 

The  110  c.c.  flask  is  cooled  in  water  at  15°  and  inverted  several  times  to  cause  the  drops  of  insoluble  fatty 
acids  to  collect.  The  liquid  is  filtered,  titration  of  100  c.e.  of  the  filtrate  with  decinormal  KOH  giving  the  Reichert- 
Meissl-Wollny  number.  The  tube  of  the  condenser  and  the  110  c.c.  flask  are  then  washed  with  three  separate 
amounts  of  15  c.c.  of  water,  which  is  passed  through  the  filter,  the  flask  being  subsequently  washed  with  three 
quantities,  each  of  15  c.c.,  of  neutralised  90  per  cent,  alcohol.  Titration  of  the  whole  of  the  alcoholic  filtrate 
with  decinormal  KOH  gives  the  Polenske  number,  which  allows  of  the  detection  of  10  per  cent,  of  coco-nut  oil 
in  butter.  The  result  has  been  stated  to  be  inconclusive  if  the  cows  have  been  fed  with  coco-nut  cake. 


FIG.  260. 


388  ORGANIC    CHEMISTRY 

of  water.  The  residue  is  then  dissolved  in  light  petroleum  and  the  solution  filtered 
through  a  tared  filter,  which  is  well  washed  with  solvent.  The  filtrate  is  distilled  in  a 
tared  flask  and  the  remaining  fat  dried  for  an  hour  in  an  oven  at  100°  to  102°  and  weighed. 
After  drying  at  100°  the  weight  of  the  filter  less  the  tare  gives  the  non-fat.  By  burning 
the  filter  in  the  crucible,  incinerating  and  weighing,  the  salts  (NaCl)  or  mineral  substances 
are  obtained. 

The  degree  of  rancidity  is  determined  as  described  on  pp.  374  and  375. 

In  order  to  avoid  rancidity,  butter  must  be  kept  or  despatched  in  ice  or  in 
cold  chambers.  Butter  may  be  coloured  yellow  by  saffron,  tumeric  or,  more  commonly, 
annatto,  which  is  an  extract  of  the  fruit  of  Bixa  orellana  made  into  a  paste  with  an  oil  ; 
the  use  of  coal-tar  dyes  is  prohibited. 

No  addition  of  antiseptic,  for  the  keeping  of  butter,  is  allowed  ;  boric  and  salicylic 
acids  can  be  detected  as  in  beer  (see  p.  179).  The  presence  of  formaldehyde  may  be 
ascertained  by  distilling  25  c.c.  of  water  in  a  current  of  steam  from  a  flask  containing 
50  grins,  of  butter  and  50  c.c.  of  boiling  water  ;  the  distillate  is  tested  by  means  of  Rimini's 
reaction  (see  p.  109). 

Addition  of  artificial  yellow  colouring -matter  is  shown  by  the  intense  coloration 
assumed  by  absolute  alcohol  when  shaken  with  the  fused  butter. 

The  price  of  butter  varies  with  the  year  and  season  from  about  2s.  to  2s.  Qd.  per  kilo. 

Italy  produced  more  than  220,000  quintals  of  butter  in  1906  and  has  always  been  a 
large  exporter,  but  the  competition  of  other  countries  (Russia,  Denmark,  &c.)  and  the 
severity  with  which  England,  in  particular,  penalises  sophisticated  butter  have  diminished 
the  exports  from  60,000  quintals  in  1905  to  50,000  in  1906,  35,000  in  1907,  31,840  in  1908, 
and  34,000  in  1910.  While  at  one  time  the  amount  exported  annually  to  England  was 
as  much  as  30,000  quintals,  it  was  only  5000  in  1907,  6800  in  1908,  and  8500  in  1910. 

In  1906  Russia  exported  432,323  quintals  of  butter  and  in  1907  547,000  quintals. 
260,000  of  this  quantity  being  from  Siberia  alone.  England  imported  butter  to  the 
value  of  £21,000,000  in  1904.  In  1902  the  United  States  produced  6,000,000  Ib.  of 
renovated  butter,1  in'  addition  to  margarine  and  ordinary  butter.  In  1909  Germany 
imported  104,000  quintals  of  butter  from  Russia  and  168,000  quintals  from  Holland. 
Hungary  produced  200,000  quintals  in  1909  and  Holland  600,000  in  1906. 

BONE  FAT  is  obtained  mainly  from  glue  factories,  and  is  extracted  from  the  crashed 
bones  either  by  boiling  with  water  (see  vol.  i,  p.  508)  and  skimming  the  fat  which  collects 
at  the  surface,  or  by  treatment  with  benzine  or  carbon  disulphide  in  an  extraction  appara- 
tus (see  later).  The  first  method  yields  3  to  4  per  cent,  of  fat,  and  the  second  7  to  9  per 
cent.  The  latter  has,  however,  an  unpleasant  smell  and  is  dark  and  of  inferior  quality  ; 
it  can  be  refined  by  means  of  dilute  sulphuric  acid  or  sulphuric  acid  and  dichromate  or 
barium  peroxide  (see  Tallow).  Its  constants  are  given  in  the  Table  on  p.  378. 

It  is  used  in  making  soap,  especially  resin-soap. 

HOG'S  FAT  (Lard)  is  obtained  by  melting  the  fatty  parts  of  the  pig,  as  in  the  case 
of  tallow  (Refining,  see  p.  381).  In  Germany  large  quantities  of  it  are  consumed  for 
culinary  purposes,  and  in  Italy  almost  the  whole  of  this  product  is  used  by  the  lower 
classes  as  a  substitute  for  butter  and  oil.  Considerable  amounts  are  employed  in  making 
soap  and  candles.  In  1891  Germany  imported  750,000  quintals  from  the  United  Slates  ; 
but  since  this  was  prepared  with  all  the  refuse  of  oxen  and  pigs,  and  also  with  the  residues 
of  diseased  animals,  while  addition  of  appreciable  quantities  of  cotton -seed  oil  and  bleaching 
by  the  addition  of  lardstearine  were  also  resorted  to,  the  food-value  was  greatly  lowered. 
In  1906  Germany  imported  a  total  of  1,251,152  quintals  of  lard,  of  the  value  of  £4,600,000. 
The  Table  on  p.  378  gives  its  constants.  The  presence  of  cotton -seed  oil  is  detected  by 
Halphen's  test  (see  p.  381). 

In  the  United  States  the  production  of  lard  is  continually  increasing,  21  millions  of 
pigs  being  killed  in  1902  and  25 £  millions  in  1905,  the  exports  amounted  to  170,000  tons 
(£9,187,200)  in  1910  and  270,000  tons  (£10,901,000)  in  1911.  Italy  imported  9934  quintals 
of  lard  in  1906,  17,520  in  1907,  21,700  in  1908,  23,849  in  1909,  and  10,564  quintals  (worth 
£63,400)  in  1910. 

Renovated  butter  is  prepared  in  America  from  rancid  butter,  which  is  kneaded  with  a  solution  of  sodium 
bicarbonate  (e.g.  in  the  Werner  and  Pfleiderer  kneading  machine,  Fig.  258,  p.  384),  and  is  then  washed  with  just 
tepid  water  in  the  rotating-plate  kneader  (Pig.  257,  p.  383)  until  it  no  longer  gives  an  alkaline  reaction.  It  is 
then  kneaded  again  in  the  former  machine  with  milk,  cooled  with  a  jet  of  very  cold  water  and  treated  like  ordinary 
butter  a  second  time  in  the  latter  kneader.  Natural  butter  can  be  distinguished  from  renovated  butter  since 
when  melted  at  a  moderate  temperature,  the  former  gives  a  limpid  and  the  latter  a  turbid  mass. 


FISH    OILS  389 

FISH  OILS  :  WHALE  OIL  and  COD-LIVER  OIL.  The  fat  of  the  whale,  seal,  and 
dolphin  is  extracted  from  a  species  of  lard  contained  in  the  membranes  of  the  brain  and 
back  ;  it  is,  however,  worked  in  a  primitive  manner,  being  left  to  melt  and  putrefy  in 
barrels  exposed  to  the  sun.  The  oil  being  thus  separated,  the  residue  is  boiled  with  water 
to  extract  the  tallow.  When  heated  with  Water,  the  oil  loses  its  unpleasant  odour  to 
some  extent. 

The  head  and  other  parts  of  the  body  of  certain  whales,  especially  Physeter  macro- 
cephalus  (Cachelot  whale),  contain  an  oil  already  separated  and  different  from  that  of 
the  lard  ;  it  solidifies  at  the  ordinary  temperature,  giving  the  so-called  SPERMACETI 
(or  Sperm  Oil),  which,  after  filtration,  pressure  (to  separate  the  stearin  or  solid  wax),  boiling 
with  water  and  a  little  caustic  soda  and  repeated  washing  with  water,  forms  a  fat  or  oil 
of  great  value  in  the  manufacture  of  pharmaceutical  products,  perfumes,  and  high-class 
candles. 

Cod -liver  Oil  (from  the  fresh  liver  of  Gadus  morrhua,  caught  in  large  numbers  in  Norway 
and  elsewhere)  is  used  in  considerable  quantities  as  a  recuperative  medicine  in  virtue  of 
the  small  proportion  of  chemically  combined  iodine  and  of  the  large  amounts  of  readily 
emulsifiable  fatty  acids  it  contains.  It  is  now  obtained  with  a  less  unpleasant  taste  and 
smell,  as  it  is  being  prepared  in  a  more  rational  way  by  melting  it  in  closed  vessels  with  hot 
water  or  direct  steam,  the  best  results  being  obtained  in  absence  of  air — in  an  atmosphere 
of  hydrogen  or  carbon  dioxide  or  in  a  vacuum  (Eng.  Pat.  25,683,  1906)  ;  it  is  then  freed 
from  the  stearin  by  thorough  cooling  and  filtration. 

Natural  cod-liver  oil,  prepared  by  the  old  process,  has  a  considerably  higher  acidity 
(acid  number,  8  to  25)  than  that  separated  by  the  more  modern  methods  (acid  number, 
0-7  to  1-4). 

The  production  of  cod-liver  oil  in  Norway  shows  a  continual  increase,  although  it 
varies  in  different  years,  according  to  the  abundance  or  scarcity  of  the  fish,  from  20,000 
to  100,000  tons  per  annum,  about  one-half  of  this  amount  being  obtained  by  the  newer 
methods  of  extraction.  Italy  imported  31,170  quintals  of  fish  oil  in  1906,  55,036  in  1907, 
and  61,323  quintals  (of  the  value  of  £122,686)  in  1910.  Germany  imported  213,400  quintals 
in  1909. 

Adulteration  of  the  oil  is  detected  by  analysis,  taking  account  of  the  constants  given 
in  the  Table  on  p.  378.  • 

Fish-oil  Waste  is  used  in  dressing  leather,  in  the  manufacture  of  DEGRAS,1  ako  em- 
ployed for  treating  skins,  and  in  the  preparation  of  fatty  acids  for  soap-making  ;  these 
fatty  acids  are  deodorised  by  heating  with  15  to  20  per  cent,  of  concentrated  sulphuric 
acid  at  30°  to  40°,  washing  and  distilling  with  superheated  steam. 

WOOL  FAT.  Pliny  mentions  the  use  of  this  fat  in  medicine  and  its  employment  for  this 
purpose  extended  to  the  seventeenth  century.  In  1856  Chevreul  classified  it  with  the  waxes 

DEGRAS  is  obtained  in  the  chamoising  process  (separation  of  the  fat  from  the  skins  after  it  has  served 
to  oil  them  during  tanning)  and  is  used  for  tanning  other  skins.  It  consists  essentially  of  water  (30  to  40  per 
cent.),  rancid  flsh  oil,  resinous  substances  (di'gragvne  or  d*:gras-former,  14  to  20  per  cent.)  from  the  oxidation  of 
the  oil,  mineral  substances  (about  2  per  cent,  consisting  of  lime,  soda,  and  sulphates)  and  residues  of  skin,  mem- 
branes, hair,  &c.  (about  5  per  cent.).  It  has  an  acidity  number  of  25  to  35,  an  iodine  number  of  34  to  36,  a  saponi- 
flcation  number  of  144  to  155,  an  acetyl  number  of  32  to  44,  and  1  to  3  per  cent,  of  non-saponiflable  substances. 
It  is  yellowish  brown,  has  an  odour  of  flsh  oil  and  readily  forms  a  very  persistent  emulsion  with  water.  Dvgra- 
gene  is  the  characteristic  constituent  and,  unlike  other  resins,  is  insoluble  in  light  petroleum. 

Its  value  in  dressing  skins  lies  in  its  property  of  penetrating  readily,  and  in  large  quantities,  the  semi-moist 
skins,  in  the  pores  of  which  it  becomes  uniformly  distributed,  imparting  very  desirable  softness  and  fullness,  as 
well  as  keeping  qualities. 

This  use  of  degras  has  been  known  for  many  years  and  has  increased  so  rapidly  that  the  supply  is  no  longer 
sufficient,  factories  for  artificial  di'gras  having  been  established.  This  is  prepared  by  kneading  refuse  and  clippings 
of  skins  with  flsh  oil,  exposing  the  mass  to  the  air  to  oxidise  and  pressing  out  the  artificial  d6gras  or  moillon  ; 
the  residue  is  then  treated  with  a  fresh  quantity  of  flsh  oil,  this  operation  being  repeated  until  practically  no 
residue  remains.  Attempts  have  also  been  made  to  obtain  moellon  by  pulverising  flsh  oil  in  the  air  at  120°  and 
emulsifying  with  water.  At  the  present  time,  the  term  d<;gras  is  applied  to  a  complex  substance  for  dressing 
skins  and  consisting  of  a  mixture  of  moi:llon  with  wool  fat,  tallow,  and  other  solid  fats,  whilst  by  moi:llon  is 
indicated  the  aqueous  emulsion  of  oxidised  flsh  oil.  Artificial  dfigras  is  now  preferred  to  the  natural  product, 
since  different  types  can  be  prepared  for  different  purposes,  such  types  being  of  more  constant  composition,  and 
hence  more  certain  in  their  effects.  A  good  artificial  d6gras  usually  contains  15  per  cent,  or  more  of  degragi-ne 
and  less  than  20  per  cent,  of  water.  When  such  degras  contains  more  than  1  to  2  per  cent,  of  non-saponiflable 
substances,  these  are  derived,  not  from  the  flsh  oil  but  rather  from  the  wool  fat,  resin  oil,  mineral  oil,  Ac.  French 
degras  sometimes  contains  1  to  2  per  cent,  of  soap  and  as  much  as  5  to  6  per  cent,  of  skin  fibres  :  in  general,  it 
should  contain  less  than  0-05  per  cent,  of  iron  and,  when  spread  in  a  thin  layer  on  glass  and  kept  for  ten  hours 
in  an  oven  at  100°,  it  should  not  form  a  varnish  but  should  assume  only  a  horny  consistency.  When  smeared 
on  moist  and  well-pressed  paper,  it  should  be  absorbed  within  an  hour,  leaving  only  a  minimal  residue. 

Natural  degras  costs  about  56s.  per  quintal,  the  artificial  product  of  the  first  quality  about  40s.,  and  the  French 
(moe'llon)  about  68s. 


390  ORGANIC    CHEMISTRY 

owing  to  its  richness  in  cholesterol,  and  in  1867  Vohl  proposed  its  preparation  from  the 
wash-waters  of  wool.  When  washed  with  tepid  water,  soap,  and  a  little  potassium  or 
ammonium  carbonate,  certain  greasy  wools  (from  Australia)  lose  as  much  as  40  to  50  per 
cent,  of  their  weight  as  soil,  fatty  acids,  potash  soapy  substances  and  fat,  secreted  by 
the  superficial  layers  of  the  skin.  The  wool  from  certain  races  of  sheep  may  contain 
from  7  to  35  per  cent,  of  true  fat  (if  the  sheep  are  not  washed  before  shearing). 

In  some  factories  the  wool  fat  is  extracted  from  the  dried  wool  by  means  of  carbon 
disulphide  or,  better,  of  benzine  (at  Verviers,  in  Belgium,  the  Wool  from  all  the  establish- 
ments in  the  city  has  for  several  years  been  washed  with  benzine  in  a  large  works),  subse- 
quent washing  with  water  and  a  little  soap  being  then  more  easy  and  economical.  The 
crude  fat  obtained  in  this  way  after  distillation  of  the  solvent  is  slightly  coloured  and 
almost  free  from  water,  and  is  ready  for  the  market.  Usually,  however,  the  dirty  wool 
is  washed  in  the  Leviathan  machine,  the  soapy,  greasy  wash-waters  being  first  allowed 
to  stand  to  deposit  earthy  matters  and  then  treated  with  dilute  milk  of  lime  or,  better, 
with  calcium  chloride  solution  slightly  acidified  with  hydrochloric  acid.  The  soaps  and 
fatty  acids  (palmitic,  cerotic,  a  little  caproic  and  oleic  and  traces  of  stearic,  isovaleric, 
butyric,  myristic,  carnaubic,  and  lanoceric)  are  precipitated  as  calcium  salts  and  carry 
down  the  wool  fat,  which  is  only  slightly  saponifiable  owing  to  its  large  content  (55  to 
60  per  cent.)  of  cholesterol,  isocholesterol,  ceryl  alcohol,  lanolyl  alcohol  (C^H^O)  and 
carnaubyl  alcohol  (C24H6()O),  which  do  not  contain  glycerides.  After  this  treatment  the 
wash -waters  are  either  left  to  stand  or  coarsely  filtered  to  separate  the  pasty  mass  ;  in 
some  cases  the  water  is  removed  from  the  calcium  soap  and  fat  by  centrifuging  in  a 
separator  similar  to  that  used  for  milk  (Fig.  260,  p.  387).  The  paste  thus  obtained  is 
dried  in  the  sun  or  in  an  oven  and  then  made  into  cakes  with  sawdust,  &c.,  the  rather 
dark  crude  wool  fat  being  extracted  from  these  by  means  of  carbon  disulphide  or, 
better,  benzine.  The  residue  from  the  cakes,  when  treated  with  dilute  sulphuric  acid, 
yields  fatty  acids  and  the  resultant  aqueous  emulsion,  coarsely  filtered  to  remove  solid 
substances,  deposits  the  fatty  acids  on  heating. 

Thus  obtained,  wool  fat  is  dirty  yellow,  transparent,  and  very  viscous  (it  can  be 
obtained  pale  yellow  by  special  refining  processes)  ;  it  melts  at  35°  to  40°,  and  has  a 
saponification  number  of  85  to  105,  an  iodine  number  of  13  to  17,  an  acid  number  of 
0-5  to  1-3,  a  Hehner  number  of  85  to  95,  a  Reichert-Meissl  number  of  6  to  7,  and  0-5  to 
1  per  cent,  of  water,  while  its  rotatory  power  in  saccharimetric  degrees  is  +10-2  to 
+  11-2.  Commercial  lanoline  does  not  contain  more  than  30  per  cent,  of  water. 

Wool  fat  is  better  suited  than  any  other  fat  or  even  vaseline  as  a  basis  for  salves 
and  ointments,  and  has  also  considerable  power  to  penetrate  the  skin.  It  mixes  readily 
with  large  proportions  (up  to  105  per  cent.)  of  water  (which  separates  in  the  hot)  and, 
if  mixed  with  20  per  cent,  of  olive  oil,  it  can  absorb  320  per  cent,  of  water. 

In  some  cases  the  crude  wool  fat  is  distilled  with  superheated  steam,  this  procedure 
giving  a  wool  oil  or  ivool  oleine  containing  40  to  50  per  cent,  of  fatty  acids,  35  to  45  per 
cent,  of  hydrocarbons,  and  5  to  10  per  cent,  of  alcohols,  while  the  distillate  deposits  a 
wool  stearine,  which  melts  at  42°  to  55°,  has  an  iodine  number  of  37,  and  a  saponification 
number  of  170,  and  contains  cholesterol  and,  altogether,  73  to  88  per  cent,  of  free,  solid 
fatty  acids. 

In  1905  Germany  exported  1340  quintals  (1300  in  1903)  of  lanoline,  of  the  value 
of  £10,000. 

VEGETABLE  OILS 

In  plants  oils  accumulate  especially  in  the  seeds  and  the  fleshy  parts  of 
the  fruit,  rarely  in  the  roots.  The  composition  of  these  oily  parts  varies 
somewhat  with  the  locality  and  with  the  character  of  the  season.1 

In  1881  Italy  imported  201,000  quintals  of  vegetable  oils  for  industrial 
purposes  ;  in  1891  about  542,000  quintals,  andsin  1903  almost  707,000  (20,000 
of  palm  and  coco-nut  and  43,000  of  cotton-seed  oil ;  in  1905  the  amount 
rose  to  120,000  quintals).  In  1905  Italy  also  imported  650,000  quintals  of 
oily  seeds  (104,000  of  castor  oil,  180,000  of  sesame  and  arachis,  and  360,000 

1  For  the  Mean  Composition  of  Oily  Seeds  and  Fruits  (the  maxima  and  minima  are  10  to  IB  per  cent, 
above  and  below  the  mean  values),  Bee  Table  at  foot  of  next  page. 


VEGETABLE    OILS 


391 


of  linseed,  rapeseed,  and  ravison).  In  1910  Italy  imported  58,456  quintals 
of  olive  oil,  3825  of  linseed  oil,  35,800  of  cotton-seed  oil  (in  1909,  306,000  and  in 
1908,  108,000  quintals,  of  the  value  of  £320,000),  20,000  of  coco-nut  oil,  81,900 
of  palm  oil,  177  of  castor  oil,  and  50,800  (only  4700  in  1908)  of  arachis  oil ; 
in  the  same  year  were  imported  also  129,570  quintals  of  castor  oil  seeds, 
367,660  of  linseed  (463,000  in  1909),  22,800  of  rape  and  ravison  seeds,  385,880 
of  sesame  and  arachis  seeds,  and  130,000  quintals  of  various  other  oily  seeds. 
In  1908  France  imported  7,830,400  quintals  of  oily  seeds  (4,650,000  for 
Marseilles),  and  324,000  quintals  of  olive  oil.  The  imports  at  Marseilles  alone 
were,  in  1910,  6,656,790  quintals  of  oily  seeds,  348,000  quintals  being  arachis, 
171,423  tons  copra,  91,000  tons  sesame,  and  11,655  tons  cotton-seed. 

The  oil  is  extracted  by  two  processes  :  by  pressure  and  by  means  of  solvents. 
Edible  oils  are  always  obtained  by  the  former  method,  as  also  are  most  of  the 
others,  solvents  being  used  to  extract  the  remaining  oil  from  the  pressed 
residues  (oil-cake),  when  these  are  not  to  be  used  for  cattle-food. 

According  to  the  power  and  degree  of  perfection  of  the  pressing  appliances, 
from  one-fourth  to  one-seventh  of  the  total  oil  is  left  in  the  cake.  Extraction 
of  the  powdered  cake  with  solvents  removes  all  but  the  fiftieth  part  of  the 
total  amount  of  oil  (1  to  2  per  cent,  instead  of  10  to  12  per  cent.). 

The  seeds  are  not  worked  up  immediately  after  gathering,  but  are  first 
matured,  dried,  and  turned  in  bins  or  silos.  They  are  then  cleaned  with 
sieves  and  fans,  crushed  in  a  kind  of  roller  press  (similar  to  that  shown  in 
Fig.  212,  p.  251)  and  powdered  (sometimes  this  is  done  directly)  in  vertical 
cast-iron  or  stone  mills  like  that  illustrated  in  Fig.  210  on  p.  251.  A  mill 
with  a  diameter  of  1-7  metre  converts  about  35  litres  of  linseed  into  flour 
in  twenty-five  minutes. 

To  obtain  the  edible  and  so-called  virgin  oil,  the  flour  is  pressed  cold, 
although  more  commonly  the  pressing  is  carried  out  in  the  hot,  this  increasing 
the  yield  but  injuring  the -quality  and  colour. 


Organic 
matter 

Proteins 
in  100 

Cakes  after 
pressing 

Water 

Ash 

Oil 

parts  of 

oil 

organic 
matter 

Fat 

Protein 

per  cent. 

per  cent. 

Olive  :  pulp     .... 

24-22 

2-68 

56-40 

16-70 

1-10 

\ 

kernel  (shell) 

4-20 

4-16 

5-75 

85-89 

2-50 

f    5-15 

4-8 

seed     .... 

6-20 

2-16 

12-26 

79-38 

2-16 

J 

Linseed  :  winter 

8-65 

3-15 

35-20 

53 

22-10 

f     6-8 

30-38 

summer  . 

7-80 

3-20  ' 

31-60 

57-40 

24 

Ricinus  (seeds)  :  Italian  .         .                   8 
Indian   .         .                   7-26 

2-93 
3-40 

52-62 
55-23 

36-45 
34-11 

25-50 
24-26 

}    7-10 

28-31 

Sesam6  (seeds)  :   brown  Levant                    5-90 
yellow  Indian                     7-06 

7-52 
6-85 

55-63 
50-84 

30-95 
35-25 

21-42 
22-30 

j-  10-15 

35-40 

Cotton-seed  :   Egyptian    .         .                   7-54 
American   .         .                  8-12 

8-60 
9-44 

23-95 
20-58 

59-91 
61-86 

27-20 
28-12 

}  12-16 

36-48 

Colza  or  rape  (seeds) 

6 

4-30 

38 

51-70 

20 

8-10 

29-32 

Ravison  (seeds)  :  fresh 

9-10 

4-80 

36-80 

49-30 

2-50 

f     7-10 

29-32 

two  years  old                    5-25 

4-36 

39-25 

51-14 

4-20 

Arachis  (shelled  nuts)  :  fresh    .                   7-37 
old       .                   2-75 

2-43 
2-50 

37-84 
41-63 

52-36 
53-12 

27-25 
27-85 

}    6-9 

44-50 

Hempseed       .                   .          .                   8-65 

3-45 

33-60 

54-30 

15-95 

8-12 

28-33 

Mustard  :  black                 .         .             1       6-78 

4-21 

22-20 

66-81 

20-52 

— 

— 

white 

7 

4-45 

29-30 

59-25 

28-20 

— 

— 

Poppy  :   white 
black 

8-85 
9-50 

3-42 

4 

55-62 
51-36 

32-11 
35-14 

16-89 
17-50 

}  9-11 

33-37 

Sweet  almonds 

9-53 

2-86 

51-42 

38-19 

22-50 

— 

— 

Maize  :  whole  grain 

— 

— 

6-10 

— 

— 

— 

— 

germ 

— 

— 

44-46 

— 

—  • 

6-10 

14-18 

Palm  fruit      .... 

— 

—  . 

65-72 

— 

—  . 

— 

— 

Palm  kernel 

— 

— 

45-50 

— 

— 

7-9 

14-17 

Coco-nut   '     .                  .         . 

— 

45-63 

~ 

10-14 

18-22 

392 


ORGANIC    CHEMISTRY 


Nowadays  the  pressing  is  effected  almost  everywhere  with  hydraulic  presses  of  various 
forms,1  and  only  in  small  works  are  wooden  or  metal  screw-presses  still  employed. 

A  hydraulic  press  which  is  widely  used  is  the  ring-press  of  Brink  and  Hiibner,  of 
Mannheim,  shown  in  Fig.  261.     The  powdered  seeds  are  placed  on  the  rings,  a,  the  base 

of  which  consists  of  a  movable,  perforated  steel  plate 
covered  with  a  disc  of  woollen  or  horsehair  material.  The 
flour  is  well  pressed  by  hand  or  by  a  suitable  machine, 
covered  with  a  second  woollen  or  horsehair  disc,  and  passed 
along  the  guides,  b,  being  thus  brought  between  two  plates, 
e,  which  are  smooth  underneath  and  grooved  on  the  top 
and  fit  exactly  into  the  two  rings  containing  the  flour,  one 
above  and  the  other  below.  The  grooved  side  of  the  plate 
has  also  a  circular,  peripheral  channel  which  collects  the 
oil  issuing  from  the  perforated  base  of  each  of  the  rings 
when  the  press  is  working. 

The  automatic  changing  of  the  rings  requires  1  to  2 
minutes,  about  the  same  length  of  time  being  occupied 
in  discharging  them,  while,  under  a  pressure  of  200  to 
300  atmos.,  the  pressing  is  complete  in  8  to  10  minutes. 
Especially  with  palm  oil  and  coco -nut  oil,  the  pressing  may 
be  carried  out  in  the  hot,  the  plates  being  arranged  so  that 
they  can  be  heated  ;  this  procedure  shortens  the  time  of 
pressing  and  increases  the  yield  of  oil.  In  some  cases  the 
pressing  is  carried  out  first  at  a  low  pressure,  which  gives 
an  oil  of  improved  quality,  the  cake  thus  obtained  being 
ground  (e.g.  by  an  Excelsior  mill,  p.  168)  and  squeezed 
under  a  high  pressure  for  the  extraction  of  a  further 
quantity  of  oil  of  lower  grade. 

Extraction  of  the  oil  by  means  of  solvents  (first  attempted 
in  England  in  1856),  from    the  crushed   seeds   or  broken 
JIIG    261  cake,  is  effected  with  carbon  disulphide  (see  vol.  i,  p.  396) 

— which  has  considerable  solvent  action  on  fats,  even  in 

the  cold,  but  also  removes  a  certain  amount  of  chlorophyll — or  with  light  petroleum 
(benzine),  which  exerts  its  maximum  solvent  effect  in  the  hot.  The  use  of  carbon  tetra- 

^~  *  The  HYDRAULIC  PRESS  is  based  on  Pascal's  principle,  according  to  which  a  pressure  exerted  on  any 
point  of  a  liquid  mass  is  transmitted  with  the  same  intensity  ir>  all  directions.  So  that,  if  a  pressure  of  1  kilo, 
is  exerted,  by  means  of  a  piston  1  sq.  cm.  in  area,  on  a  liquid  in  one  arm  of  a  U-tube,  the  other  branch  of  which 
is  closed  by  a  piston  16  sq.  cm.  in  area,  this  would  require  a  pressure  of  16  kilos  to  balance  the  first  piston  (Fig. 
262),  the  pressure  transmitted  by  the  pressing  surface  being  proportional  to  the  area  receiving  the  pressure. 


16  K 


FIG.  262. 


FIG.  263. 


The  hydraulic  press  consists  of  a  suction  pump,  P  (Fig.  263),  which  draws  water  from  the  reservoir,  A,  and 
forces  it  through  the  strong  copper  tube,  t,  into  the  thick-walled  chamber,  B,  hermetically  sealed  at  the  upper 
part  by  a  large  piston,  6,  carrying  a  wide  plate,  c,  on  which  is  placed  the  material  to  be  compressed.  The  com- 
pressing surface  is  that  of  the  base  of  the  small  pump-piston  and  the  surface  receiving  the  pressure  is  given  by 
the  base  of  the  piston,  b,  the  pressure  received  being  dependent  on  the  ratio  of  the  sections  of  the  pistons  and 
on  the  ratio  between  the  arms,  OP  and  PR,  of  the  pump-lever.  If  PR  is  ten  times  as  long  as  PO  and  the  force 
exerted  at  R  is  30  kilos,  the  piston  of  the  pump  receives  a  pressure  of  300  kilos  (30  x  10)  ;  if,  on  the  other  hand, 
the  section  of  the  large  piston,  b,  is  15  times  as  great  as  that  of  the  small  piston,  the  pressure  exerted  on  the 
latter  will  be  4500  kilos  (300  X  15). 

When  the  piston,  b,  rises,  the  plate  presses  the  substance  against  a  strong  cover,  d,  fixed  by  three  or  four 


EXTRACTION    OF    OILS 


393 


chloride  has  also  been  suggested  recently  (see  vol.  i,  p.  378),  since  it  is  not  inflammable 
like  the  other  two  solvents  and,  further,  allows  of  the  extraction  of  the  oil  from  moist 
substances. 

The  extraction  can  be  carried  out  by  direct  exhaustion  or  by  systematic  exhaustion. 
In  the  former  case,  the  substance  is  treated  with  pure  solvent,  so  that  large  quantities 

of  dilute  solutions  which  must  be 
concentrated  are  obtained  ,•  in  the 
other  process,  a  number  of  appa- 
ratus are  arranged  in  a  series  so 
that  the  solvent  passes  from  one  to 
the  other  and  leaves  the  last  com- 
pletely saturated,  while  the  first 
apparatus,  as  it  becomes  exhausted, 
is  charged  with  fresh  material  and 
placed  last  in  the  series  (see  vol.  i, 
p.  470,  and  exhaustion  of  beet  in  the 
diffusers,  under  the  heading  Sugar, 
later).  From  the  saturated  solution 
of  the  oil,  the  solvent  is  distilled 
by  means  of  direct  or  indirect  steam 
and  is  thus  completely  recovered, 
while  the  crude  fat  remaining  is 
refined. 

There  are  various  forms  of  appa- 
ratus corresponding  with   the   first 
method  of  extraction,  such  as  the 
FIG.  264.  Merz   universal   extractor,    that    of 

Pallenberg,    and    the  Wegelin    and 

Hubner  (Fig.  264)  form,  which  is  fairly  widely  used.  In  the  last  of  these  the  fatty  material 
is  placed  in  the  vessel,  A,  into  which  solvent  is  introduced  from  D  by  means  of  the  tube, 
r  q.  The  solvent  saturated  with  fat  is  discharged  into  the  still,  C,  where,  by  means  of 
indirect  steam  passing  through  the  coil,  y,  the  solvent  is  distilled,  its  vapour  ascending 
the  tube,  i,  and  condensing  in  B,  and  the  liquid  collecting  in  D.  The  fat  remaining  in 

columns,  e.    When  the  pressure  is  to  be  released,  the  water  is  discharged  from  the  chamber,  B,  and  the  piston 

descends.    The  pump  is  provided  with  a  safety-valve  which  regulates  the  maximum  pressure  desired.    The 

large  piston  is  made  tight  by  encircling  it  at  b  with  a 

leather  ring  (devised  by  the  Englishman  Bramah)  with  an 

Inverted  U-section  ;  the  water,  in  its  attempts  to  escape 

along  the  sides  of  the  piston,  enters  the  ring  and  forces 

its  edges  against  the  piston  with  a  pressure  increasing  with 

the  pressure  of  the  water,  and  thus  forms  a  true  hermetic 

seal. 

Nowadays  horizontal  hydraulic  presses,  which  discharge 
the  oil  and  cake  more  easily,  are  also  used,  but  these  occupy 
more  space,  while  at  the  same  time  the  piston  does  not 
recede  of  itself  at  the  end  of  the  operation. 

In  practice,  when  a  substance  is  to  be  compressed  with  a 
hydraulic  press,  two  or  more  pumps  are  used.  The  first, 
which  has  a  long  stroke,  raises  the  piston  and  plate  rapidly, 
since  at  first  the  resistance  is  small ;  when  the  pressure 
increases,  the  compression  is  continued  more  slowly  by 
means  of  a  small  pump. 

To  avoid  attention  to  a  number  of  pumps  and  loss  of 
energy,  works  employing  many  hydraulic  presses  make  use 
of  the  so-called  hydraulic  accumulators  (Armstrong,  1843), 
which  provide  a  store  of  water  under  high  pressure  for  the 
feeding  of  several  presses  at  once  (Figs.  265  and  266).  A 
piston,  L,  moving  in  a  cylinder,  B,  just  as  in  an  ordinary 
hydraulic  press,  receives  pressure  from  below  by  means  of 
compressed  water  from  a  pump,  passing  through  p  and  Vi ; 
the  upper  part  of  the  piston  is  fixed  to  the  centre  of  a 
plate,  C,  which,  by  means  of  three  columns,  S,  supports 
the  plate,  E,  carrying  the  heavy  iron  discs,  D.  When  the  piston  is  raised  by  the  compressed  water  entering 
A,  the  whole  accumulator,  E,  C,  and  the  discs,  D,  are  raised.  When  Vi  is  closed,  A  contains  a  store  of 
water  under  great  pressure  which  transmits  pressure  to  a  number  of  hydraulic  presses  simultaneously  when 
the  cock,  D2,  communicating  with  these  presses  is  opened.  In  order  to  prevent  the  piston,  L,  from  being 
raised  too  much  and  so  forced  out  of  the  cylinder,  B,  the  lower  part  of  the  piston  is  provided  with  a  small  vertical 
channel  with  a  lateral  exit ;  when  the  latter  is  forced  from  the  top  of  the  cylinder,  B,  the  water  escapes,  the 
pressure  is  lowered  and  the  piston  falls.  Large  works  are  supplied  with  two  or  more  accumulators,  so  that  when 


FIG.   265. 


FIG.  266. 


394  ORGANIC    CHEMISTRY 

C  can  then  be  drawn  off  through  the  tap,  x,  but  if  it  retains  solvent  tenaciously,  it  is 
first  heated  by  a  current  of  direct  steam,  solvent  and  water  then  condensing  together 
in  the  condenser,  B  ;  owing  to  their  mutual  insolubility,  these  two  liquids  can  be  separated 
by  means  of  a  suitable  separator  situated  at  w  between  B  and  D,  the  water  being  thrown 
out.  If  the  solvent  saturated  with  fat,  instead  of  being  drawn  off  by  the  tube,  u,  is 
caused  to  rise  to  the  top  to  the  tube,  I,  whence  it  falls  into  the  tube,  v,  the  extraction  is 
effected  with  continuous  circulation  of  the  solvent  until  the  substance  is  exhausted.  To 
expel  and  recover  the  solvent  retained  by  the  substance  remaining  in  A,  a  current  of 
direct  steam  is  passed  into  the  latter  ;  this  carries  off  the  vaporised  solvent  along  the 
tube,  k,  through  the  valve,  n,  to  the  cooling  coil,  B,  the  condensed  water  and  oil  being 
passed  through  the  separator,  w,  before  the  latter  liquid  is  collected  in  D. 

Large  works,  however,  always  use  batteries  of  extraction  apparatus  arranged  in 
series. 

In  a  good  extracting  plant,  the  loss  of  solvent  does  not  usually  exceed  0-5  per  cent, 
of  the  weight  of  oil  extracted  and  is  always  less  than  1  per  cent. 

REFINING  of  oils,  to  separate  as  far  as  possible  the  tannin,  protein,  and  colouring- 
matters  extracted  from  the  oily  seeds  and  fruits,  is  generally  effected  by  means 
of  dehydrating  or  oxidising  agents  .(the  latter  attack  the  colouring -matters  more 
especially). 

In  order  that  sulphuric  acid  may  not  act  on  the  glycerides  (forming  ethers)  and  heat 
and  partially  carbonise  the  oil,  it  must  be  used  at  a  concentration  of  about  60°  Be.  and 
in  small  quantity  (1  to  2  per  cent.)  with  oil  heated  to  50°  to  60°,  or  with  the  cold  oil  ;  under 
these  conditions  the  few  impurities  are  first  carbonised  and  the  oil  becomes  coloured, 
but  after  filtration  it  is  obtained  paler,  purer,  and  clear. 

Zinc  chloride  often  gives  almost  the  same  results  as  sulphuric  acid,  and  is  added  in 
concentrated  solution  (sp.  gr.  1-85)  and  in  amounts  up  to  1-5  per  cent,  of  the  oil  ;  the 
black  flocculent  matter  formed  separates  on  standing  or  filtration. 

In  some  cases  it  is  sufficient  to  leave  the  oil  in  large  closed  tanks  of  tinned  iron  with 
conical  bases  fitted  with  taps  so  that  the  impurities  which  gradually  settle  may  be  removed. 
Fragments  of  coal,  peat,  willow,  &c.,  may  be  added,  these  carrying  down  the  impurities 
as  they  settle.  In  order  to  avoid  prolonged  contact  of  the  oil  with  the  air,  pressure  filters 
(described  in  the  section  on  Sugar)  are  preferred  ;  either  the  oil  is  placed  at  a  higher 
altitude  than  the  filter,  or  the  pressure  is  applied  by  means  of  pumps,  it  being  possible 
in  this  way  to  filter  1000  to  2000  kilos  of  oil  in  24  hours.  To  purify  with  sulphuric  acid 
(see  later,  Twitchell  process),  the  latter  is  poured  in  a  thin  stream  into  the  oil  contained 
in  a  lead-lined  vat  and  kept  well  stirred.  After  7  to  8  hours,  by  which  time  small 
black  clots  of  carbonised  impurities  have  deposited,  the  oil  is  decanted  into  a  second 
vat,  washed  two  or  three  times  with  water  at  40°  to  60°  (in  some  cases  a  small  quantity 
of  sodium  carbonate  is  added  to  the  second  water),  being  stirred  meanwhile  or  emul- 
sified by  air  from  a  Korting  injector  ;  after  being  left  to  stand,  it  is  either  decanted  or 
filtered. 

The  water  is  sometimes  intimately  mixed  with  the  oil  to  be  washed  by  means  of  the 
so-called  emulsor-centrifuge,  (Fig.  267),  consisting  of  two  superposed  metal  plates  with 
the  concave  parts  inside  and  mounted  on  a  hollow  axle  rotatable  at  8000  to  10,000  revs, 
per  minute,  while  through  a  central  aperture  commanded  by  two  taps — exactly  adjust- 
able— the  oil  and  water  are  introduced  in  the  desired  proportions.  The  distance  between 
the  two  plates  can  be  altered  so  as  to  give  a  slit  between  their  edges  from  0-02  to  2  mm. 
.in  width,  the  more  or  less  completely  emulsified  mass  being  forced  out  through  the  slit 
by  the  plates  themselves.  If  the  oil  does  not  separate  from  the  water  on  standing,  the 
emulsion  may  be  destroyed  by  added  powdered  and  calcined  sodium  sulphate  or  carbonate 
(which  act  as  dehydrating  agents)  or  by  agitating  the  emulsion  with  animal  black  or 

one  is  raised  and  the  other  at  its  low  position,  excess  of  compressed  water  supplied  by  the  pumps  at  any  moment 
is  directed  to  the  latter  accumulator,  which  is  hence  raised.  ID  this  way,  also,  the  final  pressure  of  the  hydraulic 
press  can  be  utilised  before  discharging  it,  energy  being  thus  saved  that  would  otherwise  be  lost. 

By  these  means,  a  uniform  and  persistent  pressure  may  be  exerfed  on  several  presses,  but  it  is  exerted,  not 
gradually,  but  instantaneously,  which  may  be  disadvantageous  in  certain  cases,  unless  indeed  various  accumu- 
lators at  different  pressures  are  employed.  Accumulators  with  small  pistons  may  be  used  for  pressures  up  to 
400  atmos.  The  circular  iron  rings  composing  the  accumulator  may  be  replaced  by  a  single  large  cylinder  filled 
with  scrap  iron  or  stones. 

The  pressure  of  a  hydraulic  accumulator  may  be  exerted  in  some  degree  gradually  by  connecting  it  with  a 
compressed-air  chamber  (aromatic  accumulator).  As  liquid  for  use  in  the  accumulators,  water,  glycerine,  or 
oil  may  be  employed. 


OLIVE    OIL 


395 


magnesium  silicate  (which  separates  the  components)  ;  but  the  best  results  are  obtained 
with  centrifugal  separators,  like  that  used  for  milk  (see  p.  387),  the  water  and  impurities 
being  forced  to  the  periphery,  where  they  adhere,  while  the  oil  is  discharged  by  the  central 
tube.  The  acid  may  also  be  mixed  in  the  same  way  and  continuous  working  may  be 
attained  by  means  of  a  battery  of  emulsors  and  another  of  centrifugal  separators  ;  the 
latter  serve  well  to  purify  the  dregs  of  the  oil  and,  in  general,  colloidal  and  soapy  products 
of  oils.  When  the  emulsified  or  colloidal  condition  is  due  to  the  presence  of  gum  or  wax, 
it  is  preferable  to  initiate  freezing  of  the  glycerides,  this  breaking  down  the  emulsion  so 
that  it  can  be  filtered.  When  stable  emulsions  of  oil  and  water  are  required,  as  is  some- 
times the  case,  they  can  be  obtained  by  pouring  the  oil  into  a  mixture  of  water  and  the 
amide  of  a  higher  fatty  acid  or  an  acidyl  derivative  of  an  aromatic  base,  or  both  of  these, 
together  with  the  salt  of  a  higher  fatty  acid  (Kosters,  1906). 

To  deodorise  oils,  they  are  passed  through  bone-black  or,  sometimes,  elm-bark.  Tn 
some  cases,  and  more  especially  when  very  rancid,  oils  are  purified  by  deacidifying  them 
with  a  concentrated  solution  (8°  to  10°  Be.  for  cotton-seed  oil  and  36°  to  38°  Be.  for  olive 
oil)  of  caustic  soda  in  amount  slightly  exceeding 
that  calculated  from  the  acid  number  ;  this 
treatment,  however,  readily  leads  to  the  forma- 
tion of  persistent  emulsions  and  to  loss  of 
glycerides  and  also  of  fatty  acids.  These  emul- 
sions, which  are  due  to  the  presence  of  soaps, 
are  broken  down  in  the  manner  already  de- 
scribed, first  being  heated  to  50°  to  60°.  If 
the  acidity  exceeds  30  per  cent.,  the  losses 
would  be  so  high  that  deacidification  is  not 
advisable  ;  such  oils  (e.g.  highly  acid  olive  oil 
after  refining  with  sulphuric  acid)  cannot  be 
used  as  lubricants  or  for  softening  wool,  but  are 
used  solely  for  soap,  unless  indeed  the  fatty 
acids  are  transformed  into  glycerides  by  treat- 
ment with  glycerine  as  described  on  p.  373. 

Bleaching  with  hydrogen  peroxide,  dichromate 
or  permanganate  is  carried  out  as  with  tallow 
(see  p.  381),  but  if  the  oil  is  first  deacidified, 
100  grms.  (instead  of  1500  grms.)  of  dichromate 
per  quintal  are  sufficient.  If  it  is  required  to 
eliminate  every  trace  of  soap,  the  oil  is  heated 
with  a  boiling  solution  of  5  per  cent,  sulphuric 
acid.  Vegetable  oils  are  frequently  decolorised 
nowadays  with  fuller's-earth  (see  p.  77).1 

OLIVE  OIL  is  obtained  by  pressing  the  fresh  olives  of  Olea  europcea  in  the  period 
from  October  to  December  (in  Morocco,  in  August  and  September).  The  olive  grows  in 
abundance  in  Central  and  Southern  Italy,  on  the  shores  of  Lake  Garda,  on  the  Genoese 
Riviera,  and  in  Southern  France,  Spain,  Portugal,  Dalmatia,  Istria,  Greece,  Morocco, 
California,  and  Southern  India. 

The  composition  of  the  fruit  is  given  in  the  Table  on  p.  391. 

It  is  not  advisable  to  extract  the  oil  from  stored  or  fermented  olives,  these  giving  the 
so-called  huile  tournante,  which  is  rich  in  fatty  acids  and  yields  a  persistent  emulsion 
when  shaken  with  soda  solution,  and  a  Turkey-red  oil — similar  to  the  sulphoricinate 
(see  p.  327) — when  treated  with  concentrated  sulphuric  acid. 

If  the  olives  cannot  be  worked  at  once,  fermentation  is  prevented  by  storing  them  in 
a  cold,  dry,  and  well-ventilated  place.  The  fermentation  (according  to  Tolomei)  is  due 
to  an  enzyme  (olease)  occurring  with  the  oil,  which,  in  the  presence  of  air  and  light,  it 

1  Fuller's-earth  has  been  long  used  in  Northern  Africa  for  clarifying  olive  oil;  in  Chicago  it  was  thus 
employed  as  early  as  1878,  but  its  use  was  considerably  extended  subsequently  to  1890.  It  consists  of  aluminium 
and  magnesium  hydrosilicates,  and  is  found  in  granular  or  powdery  deposits  in  Florida  and  also  at  Fraustadt, 
in  Silesia.  The  decolorising  action  of  this  earth  depends  on  its  state  of  hydration,  the  maximum  effect  being 
obtained  if  it  is  first  lightly  roasted  (at  about  200°),  while  if  the  roasting  is  carried  too  far  so  that  all  the  water 
of  hydration  is  lost,  the  decolorising  power  is  entirely  destroyed.  The  oil  is  shaken  with  1  to  3  per  cent,  of  the 
earth,  and  the  mass  heated  for  a  short  time  at  a  temperature  (60°  to  100°)  varying  with  the  nature  of  the  oil 
and  then  passed  to  the  filter-press,  the  first  turbid  portions  of  the  filtrate  being  reflltered. 


FIG.  267. 


396  ORGANIC    CHEMISTRY 

decolorises  ;    if  the  olease  is  removed  by  washing   the  oil  with  water,  the  oil  is  not 
decolorised  under  the  influence  of  light. 

The  extraction  of  olive  oil  is  not  always  effected  by  rational  processes  and  plant,  but 
usually  the  olives  are  first  crushed  by  means  of  the  ordinary  edge-runners  (see  Fig.  210, 
p.  251). 

The  pulp  is  next  placed  in  suitable  bags  of  tenacious  vegetable  fibre  or  wool  surrounded 
by  horsehair  and  then  pressed,  the  type  of  press  employed  varying  widely  with  the  locality. 
The  ring  hydraulic  press  (see  Fig.  261,  p.  392)  and  other  forms,  still  further  improved, 
give  excellent  results.  In  some  cases  a  moderate  pressure  is  first  employed,  the  result  being 
oil  of  superfine  quality  (virgin  oil).  The  residues  are  steeped  in  hot  water  and  subjected 
to  increased  pressure.  Repetition  of  this  procedure,  employing  a  still  higher  pres&ure, 
gives  an  industrial  oil.  The  cake  from  the  second  pressing  may,  however,  be  agitated 
in  a  vat  through  which  water  flows  ;  part  of  the  remaining  oil  is  thus  removed,  this  being 
collected  in  a  second  vat,  where  it  undergoes  protracted  washing  with  water,  yielding 
so-called  washed  oil. 

The  Kuess-Funaro  process  (1902),  which  results  in  an  improved  yield  and  a  readier 
extraction,  consists  in  emulsifying  each  time  with  feebly  alkaline  aqueous  solutions.1 

The  residual  cakes  (known  in  Italy  as  same),  after  being  dried,  still  contain  7  to  11 
per  cent,  of  oil,  which  is  nowadays  extracted  in  large  works  by  means  of  carbon  dkulphide, 
which  gives  the  very  green,  so-called  sulphocarbon  oil,  almost  all  of  this  being  used  in  the 
manufacture  of  green  soap  for  the  textile  industries.2 

Pure  olive  oil  is  yellowish  or,  in  some  cases,  almost  colourless  or  slightly  green.  The 
finer  qualities  taste  but  little  ;  freshly  pressed  Puglia  oil  has  a  rather  bitter  and  unpleasant 
taste  (due  to  camphene,  eugenol,  and  other  substances  investigated  by  Canzoneri),  which 
it  gradually  loses. 

The  composition  of  olive  oil  varies  with  the  district  of  origin  and  with  the  conditions 
of  extraction,  the  solid  glycerides  fluctuating  from  10  to  28  per  cent,  (more  especially 
palmitin).  The  liquid  glycerides,  which  occur  to  the  extent  of  70  to  SO  per  cent.,  were 
formerly  thought  to  consist  of  triolein  alone,  but  the  presence  of  linoleic  acid  (as  much  as 
6  per  cent.,  this  explaining  the  high  iodine  number  of  the  oil)  has  now  been  proved,  and 
there  appears  also  to  be  about  1-5  per  cent,  of  a  mixed  glyceride  and  0-2  to  1-5  per  cent, 
of  volatile  acids,  besides  0-7  to  1-6  per  cent,  of  non-saponifiable  substances  (phytosterol 
and,  according  to  Sani,  an  oil  not  yet  defined).  It  contains  a  variable  quantity  of  free 
fatty  acids,  and  when  impure  readily  becomes  rancid.  If  the  acid  number  excetels  16 
(i.e.  8-1  per  cent,  of  acids  calculated  as  oleic  acid),  it  cannot  be  used  as  machine  oil  as  it 
attacks  metals. 

1  A  new  process  of  extracting  olive  oil  proposed  by  Acapulco  (1910-1911)  and  tested  with  favourable  results 
in  the  experimental  oil  plant  of  the  Portici  Higher  Agricultural  School,  is  based  on  the  different  surface  tensions 
of  the  two  liquids  (oil  and  water)  which  are  present  in  the  pulp  of  the  olive  and  have  to  be  separated,  and  hence 
on  their  different  capillary  behaviour  towards  the  vegetable  tissues  constituting  the  pulp.  The  surface  tension 
of  the  oil^is  about  one-half  of  that  of  the  water,  so  that  separation  of  the  two  liquids  is  easily  attained  by  even 
slight  diminution  of  the  pressure  below  that  of  the  atmosphere.  The  separation  is  also  facilitated  by  rise  of 
temperature  and  by  the  fact  that  the  water  present  has  a  capillary  constant  higher  than  that  of  the  oil,  so  that 
it  remains  more  strongly  adherent  to  the  vegetable  tissues.  The  essential  part  of  the  machinery  of  this  process 
— after  the  stones  have  been  separated  from  the  pulp — consists  of  the  so-called  filtering  extractors,  formed  of 
superposed  metallic  cylinders,  inside  which  is  a  metal  filtering  cloth,  an  annular  space  communicating  with  the 
vacuum  pump  being  left  between  the  walls  and  the  cloth.  A  starrer  fitted  with  vanes  continually  moves  the  mass 
of  pulp  contained  in  the  extractor  and  spreads  it  in  thin  layers  on  the  filtering  cloth  so  that  the  liquid  portion 
is  separated  from  the  pulp.  By  steam-heating  the  extraction  can  be  carried  out  at  any  temperature.  But 
even  in  the  cold  the  exhaustion  of  the  pulp  is  more  complete  than  that  obtained  by  the  older  systems,  while  in 
the  hot  it  surpasses  that  reached  by  pressing  the  "  sanse  "  in  the  most  powerful  hydraulic  presses.  It  is  said 
that  the  Acapulco  process  is  more  economical  than  those  previously  used  and  that  it  lends  itself  to  the  production 
on  a  large  scale  of  pure,  slightly  coloured  oils  of  constant  type.  But,  as  yet,  this  process  has  not  been  subjected 
to  decisive  commercial  tests. 

*  To  distinguish  sulphocarbon  oil,  which  has  a  lower  iodine  number  (77  to  80),  from  that  obtained  by  pressure, 
Halphen's  test  (1905)  may  be  employed.  To  50  c.c.  of  the  oil  heated  to  100°  are  added  12  c.c.  of'alcoholic  caustic 
potash  diluted  with  an  equal  volume  of  water,  the  mixture  being  heated  for  ten  minutes  at  110°  and  cooled  to 
100°  ;  200  c.c.  of  hot  water  are  then  added  and  the  liquid,  after  cooling,  shaken  with  200  c.c.  of  saturated  sodium 
sulphate  solution  ;  20  c.c.  of  30  per  cent,  copper  sulphate  are  then  added,  and  the  liquid  filtered.  If  the  filtrate 
is  not  green,  a  little  more  of  the  copper  sulphate  solution  is  added  and  the  liquid  filtered  again  if  necessary. 
5  c.c.  of  silver  nitrate  solution  (containing  1  vol.  of  1  per  cent,  aqueous  silver  nitrate  solution  and  5  vols.  of  glacial 
acetic  acid)  are  then  added  to  the  liquid,  which  is  boiled,  allowed  to  cool,  supersaturated  with  ammonia  and  filtered, 
the  filter  being  washed  with  dilute  ammonia.  If  black  silver  sulphide  remains  on  the  filter,  the  presence  of  sulpho- 
carbon oil  (or  impure  cruciferous  oils — colza,  mustard,  &c. — which  cannot  be  detected  otherwise)  is  certain.  Cusson 
(1909)  has  devised  a  simpler  test :  200  grins,  of  the  oil  are  vigorously  shaken  with  50  grms.  of  90  per  cent,  alcohol 
and  then  distilled  on  a  water-bath,  the  distillate  being  collected  in  a  well-cooled  flask  containing  a  little  alcoholic 
potash.  Even  traces  of  carbon  disulphide  thus  yield  potassium  xanthate,  which  gives  a  yellow  coloration  or 
precipitate  on  addition  of  alcoholic  cupric  acetate  solution. 


TESTING    OF    OLIVE    OIL  397 

Pure  olive  oil  is  used  as  a  comestible  and  the  very  pure  and  more  liquid  qualities  for 
oiling  clocks,  while  the  other  qualities  are  employed  in  large  quantities  in  the  manufacture 
of  soap,  lubricants,  burning  oil,  and  Turkey-red  oil. 

The  purity  of  the  oil  is  controlled  by  various  tests  referring  to  the  constants  given  in 
•  the  Table  on  p.  378,  and  by  certain  special  tests.  Olive  oils  of  certain  origins  give  abnormal 
constants,  e.g.  Algerian  and  Moroccan  oils  have  an  iodine  number  of  96  and  are  reddened 
by  nitric  acid  ;  pure  Tunisian  olive  oil  gives  the  reaction  for  sesame  oil  (Villavecchia  and 
Fabris'  test)  but  not  the  Belliez  reaction  (test  for  sesame  oil  with  a  saturated  solution  of 
resorcinol  in  benzene  and  nitric  acid)  ;  the  extraneous  substances  of  Tunisian  oil  which 
give  the  Villavecchia  and  Fabris  test  can  be  removed  by  shaking  the  oil  with  hot  water. 
Detection  of  added  sesame  oil  is  effected  by  Tortelli  and  Ruggeri's  modification  of  Bau- 
douin's  test  on  the  fatty  acids  (see  p.  384),  or  more  rapidly  on  the  oil  itself  by  means  of 
Villavecchia  and  Fabris'  test,  taking  care  to  dilute  5  c.c.  of  the  resulting  red  acid  liquid 
with  four  times  its  volume  of  distilled  water  and  to  shake  the  mixture  in  a  cylinder,  and 
observing  the  lapse  of  time  required  for  the  disappearance  of  the  red  coloration.  With  any 
pure  olive  oil,  if  there  is  a  coloration,  this  disappears  within  5  minutes  or,  in  exceptional 
cases,  in  8  minutes,  whilst  if  sesame  oil  (even  only  3  per  cent.)  is  present  the  colour  will 
persist  for  30  minutes  (Zega  and  Todorovic,  1909).  The  presence  of  cotton-seed  oil  is  indi- 
cated by  the  Halphen  reaction  (see  p.  381)  or  by  Tortelli  and  Ruggeri's  modification  of 
Becchi's  reaction,  which  is  carried  out  on  the  liquid  fatty  acids  in  the  following  manner  : 
20  c.c.  of  the  suspected  oil  are  hydrolysed  with  alcoholic  potash  in  the  ordinary  way  (see 
p.  379),  the  aqueous  solution  of  the  soap  being  neutralised  with  acetic  acid  and  precipitated 
with  lead  acetate  ;  the  lead  salt,  separated  by  filtration,  is  shaken  with  ether  and  the 
filtered  ethereal  solution  decomposed  in  a  separating  funnel  by  dilute  hydrochloric  acid. 
The  ethereal  layer  is  filtered  and  the  ether  evaporated,  and  to  5  c.c.  of  the  residue  (liquid 
fatty  acids)  *  are  added  10  c.c.  of  90  per  cent,  alcohol  and  1  c.c.  of  5  per  cent,  aqueous 
silver  nitrate  solution  ;  if  a  black  precipitate  is  then  formed  on  heating  for  some  time  on 
a  water-bath  at  60°  to  70°,  the  presence  of  cotton -seed  oil  is  proved.  In  certain  special 
cases  the  Becchi  reaction  alone  is  insufficient  to  indicate  with  certainty  the  presence  of 
cotton -seed  oil.  Traces  of  mineral  oils  in  vegetable  oils  are  detected  by  the  formation 
of  a  yellowish  red  solution  on  addition  of  a  benzene  solution  of  commercial  picric  acid 
(F.  Schulz,  1908 ;  see  Note,  p.  379).  To  detect  fish  oil  in  vegetable  oil,  100  drops  of  the 
latter  are  treated  with  a  mixture  of  3  c.c.  of  chloroform  and  3  c.c.  of  acetic  acid,  sufficient 
bromine  being  then  added  to  produce  a  persistent  brown  coloration  ;  after  ten  minutes 
rest  the  vessel  is  introduced  into  boiling  water,  when  the  liquid  will  remain  liquid  if  the 
vegetable  oil  is  pure,  whilst  insoluble  bromo -compounds  will  separate  if  fish  oil  is 
present.  With  boiled  oil,  the  metals  are  first  eliminated.  Where  the  oil  has  been  coloured 
yellow  with  auramine,  this  is  detected  by  boiling  1  c.c.  of  the  oil  with  20  c.c.  of  8  per  cent, 
alcoholic  potash  and  a  little  zinc  powder  in  a  reflux  apparatus,  20  c.c.  of  pure  benzene  and 
50  c.c.  of  water  being  added  after  cooling  ;  the  benzene  solution  is  evaporated  and  the 
residue  taken  up  in  glacial  acetic  acid,  a  blue  coloration,  becoming  darker  on  heating,  being 
formed  if  auramine  is  present.  Sanse  oil  or  sulphocarbon  oil,  extracted  from  the  cake  or 
marc  by  means  of  carbon  disulphide,  has  a  dark  green  colour,  and  the  corresponding  fatty 
acids  have  a  rather  low  iodine  number  (as  low  as  75)  and  a  somewhat  higher  melting-point 
than  usual. 

The  presence  of  arachis  oil  in  olive  oil  is  shown  by  the  Tortelli  and  Ruggeri  test,  which 
has  been  modified  by  Fachini  and  Dorta  (1910)  as  follows :  20  grms.  of  the  oil  are  saponified 
with  alcoholic  potash,  the  alcohol  being  then  expelled,  the  soap  dissolved  in  water,  the  fatty 
acids  liberated  by  hot  dilute  sulphuric  acid,  and  the  clear  fused  acids  collected  on  a  moist 
filter  ;  they  are  then  washed  with  hot  water  and  dissolved  in  150  c.c.  of  pure,  tepid  acetone, 
water  being  subsequently  added,  drop  by  drop,  until  a  turbidity  is  formed  ;  the  liquid  is 
finally  rendered  clear  by  the  addition  of  a  few  drops  of  acetone  at  40°  to  45°  and  then  left 
to  crystallise.  In  presence  of  arachis  oil,  characteristic  shining  crystals  separate  at  15°  ; 
after  an  hour  these  are  collected  on  a  filter,  washed  with  10  c.c.  of  dilute  acetone  (32  vols. 
water  +  68  vols.  acetone)  and  examined  for  arachic  and  lignoceric  acids  by  the  Tortelli 

1  The  liquid  fatty  acids  can  be  separated,  to  a  considerable  extent  if  not  quantitatively,  from  the  solid  oner 
by  dissolving  the  mixtures  in  light  petroleum  or,  better,  in  acetone  and  crystallising  out  almost  all  the  solid  fatty 
acids  by  cooling  (to  -  20°)  (Fachini  and  Dorta,  1910).  According  to  Twitchell  (U.S.  Pat.  918,612, 1909)  the  liquid 
fatty  acids  are  separated  from  the  solid  ones  by  fusion  with  1  per  cent,  of  aliphatic  sulpho-acids,  which  render 
the  liquid  acids  soluble  even  in  water 


398  ORGANIC    CHEMISTRY 

and  Ruggeri  test :  one-half  is  dissolved  in  100  c.c.  of  70  per  cent,  alcohol,  warmed  slightly 
and  allowed  to  cool,  separation  of  crystals  indicating  arachi die  acid  (m.pt.  75°  to  76°)  with 
certainty. 

STATISTICS. — The  cultivation  of  the  olive  is  widespread  in  Italy,  where  it  extends  to 
over  a  million  hectares.  The  production  and  price  vary  considerably  from  year  to  year, 
sometimes  causing  serious  agricultural  crises.  The  production  of  the  oil  varies  from  2  to 
4  millions  of  hectolitres  (250,000  to  350,000  being  sulphocarbon  oil).  The  mean  annual 
production  per  hectare  was  3-66  hectols.  in  1879  (total,  3,400,000  hectols.)  and  2-5  hectols. 
in  1899,  the  total  being  2,515,000  hectols.  The  total  production  in  Italy  was  3,086,000 
hectols.  (3-04  per  hectare)  in  1890  ;  2,337,000  (2-16)  in  1901  ;  1,846,000  (1-7)  in  1902  ; 
3,256,000  (2-99)  in  1903  •;  3,412,300  in  1906;  2,559,000  (corresponding  with  15,000,000 
quintals  of  olives)  in  1909  ;  1,384,580  (9,366,000  quintals  of  olives)  in  1910, 

The  exportation  from  Italy  was  412,000  hectols.  in  1898  ;  506,000  in  1899  ;  290,000 
in  1900  ;  424,350  in  1901—120,000-140,000  to  France,  100,000  to  Russia,  50,000  to  North 
and  55,000-80,000  to  South  America,  60,000-80,000  to  England,  and  42,000-52,000 
to  Austria -Hungary.  In  1908  the  exports  were  368,000  quintals  (91,800  to  the  United 
States  and  127,000  to  the  Argentine) ;  in  1909, 184,500  ;  and  in  1910,  285,150  (96,000  to  the 
United  States,  73,500  to  the  Argentine,  and  40,000  to  France).  The  price  varies  according 
to  the  harvest  in  the  different  districts  and  to  the  requirements  abroad  ;  in  some  years 
the  producers  sell  at  £4  per  hectolitre  and  in  others  at  48s.  to  56s.  In  1908-1909,  owing 
to  the  small  crop  in  Puglio,  caused  largely  by  the  drought,  prices  exceeded  £7  10s.  per 
quintal.  In  1907  the  products  of  the  olive  industry  of  Italy  alone  were  valued  at  more  than 
£8,000,000  (oil  and  residues)  ;  the  number  of  presses  was  52,000,  these  being  distributed 
in  18,000  works,  of  which  only  2400  employed  steam.  During  the  two  or  three  months  of 
the  olive  campaign,  about  70,000  operatives  are  employed.  Extraction  of  the  oil  by  means 
of  carbon  disulphide  is  carried  out  in  60  works,  consuming  780  h.p.  (almost  all  steam- 
power)  and  employing  1230  workmen.  The  exportation  of  sulphocarbon  and  washed  oil 
was  about  60,000  quintals  in  1900,  100,000  in  1904,  55,660  in  1909,  and  131,400  in  1910. 
Italy  imports  olive  oil  every  year,  especially  from  Spain  and  Greece,  the  total  amount  being 
39,000  quintals  in  1908,  52,330  in  1909,  and  58,450  in  1910.  Portugal  produces  250,000 
to  350,000  hectols.  per  annum,  and  Spain  (especially  in  Andalusia)  about  2  or  3 
millions  of  hectols.,  of  lower  quality  than  the  Italian.  In  1905  the  Spanish  production 
was  1,492,490  quintals,  and  in  1906,  1,336,650;  the  amount  exported  being  340,000 
quintals  in  1905,  190,000  in  1906,  and  about  150,000  in  1907. 

France,  with  about  150,000  hectares  under  olives,  produces  annually  about  1,500,000 
hectols.  of  oil.  Greece  produces  550,000  hectols.  (in  1907)  ;  Asiatic  Turkey  (with  Crete), 
2,000,000  hectols.,  importing  also  350,000-500,000  hectols.,  especially  from  Spain,  Italy, 
Tunis,  and  Algeria,  and  exporting  200,000-250,000  hectols.  of  the  finest  quality.  In  1906 
Tunis  produced  243,000  hectols.,  and  in  1907  almost  400,000. 

The  world's  production  is  about  10,000,000  hectols.  of  the  oil.  Germany  imports 
10,000-13,000  tons,  seven-tenths  of  it  for  industrial  purposes.  Austria  imports  about 
6000  tons.  England  imported  crude  olive  oil  to  the  value  of  £300,000  and  purified  oil  to 
the  value  of  £386,190  in  1910.  The  imports  into  the  United  States  were  valued  at  £1 ,162,400 
in  1910  and  at  £1,149,800  in  1911. 

CASTOR  OIL  is  extracted  from  the  seeds  of  Ricinus  communes,  a  plant  cultivated  in 
India,  Italy,  Messina,  California,  Egypt,  and  Greece.  The  oval  seeds  are  10  to  15  mm. 
long,  about  6  mm.  broad,  and  rather  flat,  and  are  covered  with  a  brownish  or  marbled, 
shining,  brittle  skin  ;  when  peeled  they  contain  45  to  55  per  cent,  of  oil. 

The  oil  was  at  one  time  extracted  by  pressing  the  ground  seeds  twice  in  the  dry  state 
and  then  pressing  the  residue  after  steeping  in  hot  water.  Nowadays,  however,  three 
consecutive  pressings  of  the  hot  crushed  seeds  with  increasing  pressures  are  employed, 
modern  hydraulic  presses  being  used.  This  procedure  yields  first  a  fairly  pure  pale  oil, 
then  one  less  pure,  and  finally  a  more  highly  coloured  oil  for  secondary  industrial 
purposes.  One  hundred  kilos  of  the  seeds  yield  9  kilos  of^husks,  43  of  residual  cake,  20  of 
oil  of  the  first,  10  of  the  second,  and  8  of  the  third  pressing.  The  oil  is  purified  by  heating 
with  an  equal  volume  of  boiling  water,  which  precipitates  many  protein  and  gummy 
substances  ;  it  is  decolorised  by  means  of  bone-black  or  by  the  ordinary  processes  given  for 
tallow. 

The  refined  oil  is  almost  colourless  or  faintly  yellow,  and  has  a  high  specific  gravity, 


LINSEED    OIL  399 

considerable  viscosity,  and  a  peculiar,  unpleasant  taste  and  smell.  It  forms  an  excellent 
purgative,  the  less  pure  qualities  being  used  in  the  manufacture  of  sulphoricinate  (see 
p.  327)  and  of  transparent  soaps  capable  of  retaining  considerable  quantities  of  water.  Its 
soap  differs  from  others  in  not  rendering  water  opalescent.  The  residual  cake,  whether 
extracted  with  carbon  disulphide  or  not,  is  injurious  and  cannot  be  used  as  cattle-food, 
but  it  is  of  value  as  manure,  since  it  contains  4  to  5  per  cent,  of  combined  nitrogen  and  is 
sold  at  8s.  to  105.  per  quintal. 

Castor  oil  contains  various  glycerides  but  is  free  from  tripalmitin.  Triricinolein  is  solid, 
and  there  appear  to  be  glycerides  of  a  ricinoleic  acid  and  of  a  ricinisoleic  acid,  also  of  a 
hydroxystearic  acid  (melting  at  141°  to  143°)  and  a  dihydroxystearic  acid  (which  explains 
the  characteristic  high  acetyl  number  of  castor  oil). 

The  oil  yields,  besides  ricinoleic  acid,  more  or  less  highly  polymerised  compounds  with 
less  and  less  marked  acid  characters  (e.g.  ricinisoleic  acid),  these  increasing  in  amount 
with  the  age  of  the  oil. 

Castor  oil  is  strongly  dextro-rotatory  (40-7°  in  a  20  mm.  tube).  Unlike  other  oils,  it  is 
soluble  in  all  proportions  in  absolute  alcohol  and  in  glacial  acetic  acid  ;  at  15°  it  dissolves 
in  2  parts  of  90  per  cent,  alcohol  or  4  parts  of  84  per  cent,  alcohol,  but  is  insoluble  in  light 
petroleum  or  paraffin  oil  (both  of  which  dissolve  all  other  oils  and  fats).  Hence,  if  a  castor 
oil  is  insoluble  in  light  petroleum  and  gives  a  clear  solution  with  5  vols.  of  90  per  cent, 
alcohol,  it  may  be  regarded  as  pure.  The  solubility  relations  are  completely  inverted  if 
it  is  heated  to  300°  and  10  to  12  per  cent,  of  it  distilled  ;  there  then  remains  a  product 
termed  floricin,  which  solidifies  at  -20°,  is  insoluble  in  alcohol,  dissolves  in  all  proportions 
in  mineral  oil,  and  forms  a  stable  emulsion  with  5  parts  of  water.  A  similar  product  is 
also  obtained  by  heating  castor  oil  to  200°  in  presence  of  1  per  cent,  of  formaldehyde  ;  if 
heated  with  zinc  chloride  solution,  it  becomes  dense.  The  potassium  salt  of  the  condensed 
product,  with  water  and  formaldehyde,  gives  a  disinfectant  solution  producing  the  same 
effects  as  lysoform  or  ozoform. 

The  constants  of  castor  oil  are  given  in  the  Table  on  p.  378. 

Italy  produces  a  certain  quantity  of  castor  oil  seeds,  but  the  greater  part  is  imported, 
this  amounting  to  about  55,000  quintals  in  1 892  and  80,000  (equal  to  about  27,000  quintals 
of  oil)  in  1904.  In  1901  Italy  exported  5420  quintals  of  castor  oil  ;  in  1908,  3454  ;  in 
1909,  2292  ;  and  in  1910,  4766  quintals  of  the  value  of  £18,110.  In  1908  Germany  imported 
62,400  quintals  of  castor  oil,  and  in  1909,  85,000. 

LINSEED  OIL  is  a  drying  oil,  as  it  contains  much  linoleic  and  linolenic  acids  (see 
pp.  303  and  304),  and  when  spread  out  in  a  thin  layer  on  a  sheet  of  glass  slowly  forms  a 
solid  skin  (varnish),  this  forming  more  rapidly  with  the  boiled  oil. 

Linseed  oil  is  extracted  from  the  seeds  (containing  35  per  cent,  of  oil)  of  Linum  usitatis- 
simum,  which  are  converted  into  flour  by  the  ordinary  edge-runner  mills  and  pressed 
hot  in  hydraulic  presses. 

Linseed  is  cultivated  especially  in  the  Baltic  provinces  of  Russia,  and  also  in  Southern 
Russia,  Eastern  India,  the  United  States,  and  the  Argentine,  and  to  a  less  extent  in  Egypt, 
Belgium,  and  Italy.  Linseed  oil  extracted  by  means  of  solvents  contains  more  unsaturated 
fatty  acids  and  less  volatile  acids  than  the  expressed  oil. 

According  to  Fahrion  (1903  and  1910),  the  fatty  acids  separated  from  linseed  oil  contain 
17-5  per  cent,  of  oleic  acid,  30  per  cent,  of  linolic  acid,  38  per  cent,  of  linolenic  and  iso- 
linolenic  acids,  8  per  cent,  of  palmitic  and  stearic  acids,  all  combined  with  4-2  per  cent, 
of  glycerine  and  0-6  per  cent,  of  non-saponifiable  substances. 

The  purity  of  the  oil  is  indicated  by  means  of  the  constants  given  in  the  Table  on  p.  378, 
especially  by  the  iodine  number  and  the  refractive  index,  which,  in  the  different  qualities, 
varies  from  1-484  to  1-488  at  15°  (or  from  81  to  85  Zeiss  at  25°  or  87  to  91  Zeiss  at  15°), 
whilst  cotton-seed  oil  gives  no  more  than  1-477  and  maize  oil  no  more  than  1-4765  at  15°, 

A  good  proportion  of  the  oil  is  used  in  practice  in  the  form  of  boiled  linseed  oil  (see 
Note  on  next  page),  since  on  boiling  it  acquires  drying  properties  especially  necessary  to 
the  varnishes  prepared  with  the  oil. 

The  drying  power  can  be  determined  by  Livache's  method.  On  a  watch-glass  is  spread 
1  grm.  of  lead-powder  (obtained  by  immersing  a  strip  of  zinc  in  the  solution  of  a  lead 
salt  and  washing  the  precipitate  with  water,  alcohol  and  ether,  and  drying),  on  which 
0-6  to  0-7  grm.  of  oil  is  allowed  to  fall  slowly  in  drops,  the  whole  being  then  weighed  exactly 
and  left  at  a  moderate  temperature  in  a  well -lighted  situation.  After  18  hours  the  weight 


400  ORGANIC    CHEMISTRY 

begins  to  increase,  the  maximum  increase  (12  to  15  per  cent.)  being  obtained  within  2  or 
at  most  3  days  (it  then  diminishes  slightly).  Other  drying  oils  give  the  following  increases  : 
ivalnut  oil,  7-9  per  cent.  ;  poppy-seed  oil,  6-8  per  cent.  ;  cotton-seed  oil,  5-9  per  cent.  ;  cod- 
liver  oil,  7-4  per  cent.  ;  the  remaining  oils  increase  in  weight  only  after  the  fourth  or  fifth 
day  to  a  maximum  of  2-9  per  cent,  after  seven  days.  The  drying  properties  are  determined 
best  and  most  rapidly  by  spreading  a  given  weight  of  the  boiled  linseed  oil  on  a  definite 
area  of  glass  (1  mgrm.  per  sq.  cm.)  and  leaving  the  latter  in  a  horizontal  position  until 
the  oil  is  no  longer  adhesive  when  pressed  lightly  with  the  finger  (the  temperature  should 
always  be  noted).  The  drying  power  of  an  oil  can  be  determined  also  from  the  ozone 
number  (Molinari  and  Scansetti,  1910). 

In  a  20  mm.  tube,  pure  linseed  oil  gives  a  rotation  of  -0-3°  in  the  Laurent  saccharimeter 
at  15°,  whilst  other  resin  oils  and  sesame  oil  are  dextro-rotatory. 

Linseed  oil  is  used  mostly  in  the  manufacture  of  lacs  and  varnishes,1  mastics  and  lino- 
leum. The  latter  is  obtained  by  oxidising  (blowing)  hot  linseed  oil,  after  addition  of  the 
dryer  (see  Note),  for  18  to  20  hours  with  hot  air  until  it  thickens  to  linoxyn  ;  about  30 
per  cent,  of  colophony  are  then  added,  the  whole  being  converted  into  a  paste  with  cork- 
dust  at  a  temperature  exceeding  100°.  The  mass  swells  and  is  compressed  hot  (140°)  on 
a  strong  textile  previously  varnished  to  protect  it  from  moisture,  the  whole  being  repeatedly 
pressed  between  hot  rollers.  It  is  finally  dried  in  suitable  hot  chambers,  where  it  loses  its 
smell  and  acquires  elasticity  and  weight.  It  is  coloured  in  the  pasty  condition  with  mineral 
colouring  -  matters . 

Linseed  oil  is  used  also  for  making  soft,  transparent  soaps  (see  later). 

STATISTICS.  Almost  the  whole  of  the  linseed  oil  produced  comes  from  India,  Russia 
(about  one-fourth),  North  America,  and  the  Argentine.  From  1895  to  1900  it  amounted 
to  about  1,500,000  tons,  while  in  1903  it  exceeded  2,500,000  tons,  the  price  varying  from 
£10  to  £12  per  ton.  North  America  produces  about  200,000  tons  of  the  oil  ;  the  exports 
include  very  little  oil  but  comprise  500,000  tons  of  cake  out  of  a  total  of  700,000  produced. 
The  imports  of  linseed  oil  to  the  United  States  were  valued  at  £72,600  in  1911  and  the 

1  Oil  Varnishes  and  Lacs  arc  liquids  which,  when  spread  out  in  a  thin  layer  on  an  object,  leave  on  drying 
a  solid ,  shining  skin  insoluble  in  ether  and  water  and  almost  impermeable.  Varnishes  and  lacs  have  linseed  oil 
as  a  basis,  and  are  often  mixed  with  mineral  or  organic  colouring-matters.  Oil  varnishes  are  formed  from  linseed 
oil  rendered  drying  by  dissolving  small  quantities  of  certain  minerals  in  the  hot.  Oil  lacs  are  obtained  by  adding 
to  the  almost  boiling  oil  varnish  (free  from  gummy  matter)  the  fused  copal  or  other  resin,  and  diluting  with  oil 
of  turpentine  at  the  moment  of  using  :  all  these  new  components  contribute  to  increase  the  fixation  of  oxygen. 
Crude  linseed  oil  requires  four  to  five  days  to  dry  in  a  thin  layer,  but  the  fixing  of  oxygen,  that  is,  the  drying, 
may  be  markedly  accelerated  by  the  presence  of  small  quantities  of  dissolved  metals  which  act  as  catalysts. 

At  one  time  oil  varnish  (boileft  linseed  oil)  was  prepared  by  heating  the  oil  to  220°  to  300°  for  2  to  3 
hours  in  presence  of  minium,  litharge,  or  manganese  dioxide  (dryers).  This  procedure  yielded  dark  varnishes 
(boiled  varnishes),  and  was  accompanied  by  danger  from  flre,  the  heating  being  carried  out  in  open  iron  vessels 
furnished  with  stirrers  and  heated  directly  over  the  fire.  Nowadays  the  dryer  (0-1  to  0-25  per  cent.  Mn  or  0-5 
per  cent.  Pb  +  0-1  per  cent.  Mn  is  sufficient)  is  dissolved  by  heating  at  a  far  lower  temperature  (100°  to  120° 
and  best  in  a  vacuum)  for  4  or  5  hours  (by  indirect  steam  at  135°  to  150°),  it  being  added  (when  the  oil 
ceases  frothing)  as  manganese  borate  or,  better,  manganese  linoleate  or  resinate,  and  the  mass  stirred  with  com- 
pressed air ;  in  this  way,  the  so-called  cold  varnishes  are  obtained.  These  are  paler  varnishes  which  dry  in  6 
to  8  hours,  whilst  the  others  require  as  long  as  24  hours.  It  has  been  proposed  to  decolorise  boiled  linseed  oil 
with  ultra-violet  rays.  The  drying  is  far  more  rapid  in  the  hot  than  in  the  cold.  Prolonged  boiling  of  linseed 
oil  without  dryers  increases  not  so  much  the  drying  properties  as  the  consistency,  certain  components  of  the  oil 
being  polymerised  and  the  iodine  number  consequently  diminished ;  these  oils,  thickened  at  295°  to  340",  bear 
the  names  Dickiil,  Standiil,  and  lithographers'  varnish.  The  action  of  oxygen  during  the  drying  of  varnishes 
seems  to  lead  to  the  decomposition  of  the  glycerides  of  the  saturated  acids  and  of  oleic  acid  with  subsequent 
complete  oxidation  of  the  glycerine  and  acids,  the  glyceride  of  hydroxylinolic  acid  (hydroxylinolein),  insoluble 
in  ether,  being  also  formed  as  well  as  anhydrides  and  polymerised  substances. 

In  the  manufacture  of  lacs,  a  difficult  and  important  operation  is  the  fusion  of  the  copal- — previously  prepared 
in  lumps — in  cylindrical  or  slightly  conical,  enamelled  iron  or  aluminium  vessels ;  these  are  protected  at  the 
bottom  by  an  iron  or  copper  casing  when  heated  by  direct-fire  heat  and  are  provided  with  a  cover  and  chimney 
to  carry  off  the  noxious  vapours,  which  are  carefully  condensed  or  burnt.  The  temperature  is  closely  watched 
by  means  of  a  thermometer  immersed  in  the  fused  copal  (300°  to  360°).  It  is  nowadays  regarded  as  preferable 
to  heat  with  hot  water  under  pressure  (up  to  300°)  circulating  in  coils  situate  in  the  lower  part  of  the  boiler. 
Complete,  uniform  fusion  occupies  3  to  4  hours  (with  a  loss  in  weight  of  15  to  30  per  cent.),  the  linseed  oil 
containing  the  dryer  and  heated  to  about  100°  being  then  mixed  in  ;  if  any  turbidity  appears,  the  mass  is  heated 
to  300°.  It  is  then  allowed  to  cool  to  150°  to  200°,  the  addition  of  the  oil  of  turpentine — which  dissolves  the 
lac — and,  if  necessary,  of  the  dryer,  being  then  begun.  The  diluted  lac  is  filtered  under  pressure  and  discharged 
into  smaller  vessels,  in  which  it  is  allowed  to  cool  completely.  The  addition  of  calcium  salts  of  colophony  renders 
the  lac  harder  but  more  brittle. 

The  copal  is  sometimes  replaced  by  colophony  and  other  resins,  which  are,  however,  readily  saponifiable ;  a 
mixture  of  Japanese  wood  oil  with  resin  and  a  little  lime  gives  a  good  lac.  Lacs  are  improved  by  prolonged 
storage  (at  least  a  year).  Linseed  oil  for  making  lacs  should  be  free  from  gummy  matters,  which  may  be  removed 
by  filtration  through  magnesium  aluminium  hydrosilicate  (see  p.  395).  The  softer  lacs  contain  more  than  50  per 
cent,  and  the  harder  ones  less  than  50  per  cent,  of  linseed  oil. 

The  United  States  imported  12,000  tons  (£488,000)  of  copal  (kauri  and  dammar)  in  1910  and  11,000  tons 
(£410,000)  in  1911. 


PALM    OIL  401 

exports  at  £37,200  ;  walnut  oil  to  the  value  of  £239,200  was  also  imported  in  1911.  Germany 
treated  142,000  tons  of  linseed  in  1891,  about  250,000  in  1900,  and  more  than-331,000  in 
1903  ;  consequently  the  importation  of  linseed  oil,  which  amounted  to  35,700  tons  in 
1890,  fell  to  3350  tons  in  1905  and  to  2059  in  1909.  The  importation  of  oil-cake  (mostly 
linseed)  into  Germany  is,  roughly,  about  500,000  tons  (exports,  180,000  tons).  France 
imports  about  150,000  tons  of  linseed  (1905-1906).  Holland  imports  more  than  200,000 
tons  of  linseed  and  exports  82,000  ;  it  imports  also  about  200,000  tons  of  linseed  cake  and 
exports  about  25,000  tons  of  oil.  England  imported  about  310,000  tons  of  linseed  in  1900 
and  almost  506,000  tons  in  1904  ;  the  imports  of  pure  linseed  oil  amounted  to  19,936  tons 
in  1909  and  to  37,242  tons  (£1,252,140)  in  1910  ;  30,000  tons  of  the  oil  were  exported  in 
1905,  while  in  1911  the  exports  were  valued  at  £837,712.  In  1905  Italy  imported  1800 
quintals  of  boiled  linseed  oil,  and  3011  quintals  (worth  £9030)  in  1910,  besides  438,600 
quintals  of  linseed  in  1908  and  367,660  (worth  £544,000)  in  1910  ;  the  import  duty  is  the 
same  as  for  other  vegetable  oils,  namely,  20s.  10^.  (26  lire)  per  quintal  for  the  boiled  oil 
and  19s.  2d.  (24  lire)  for  the  crude.  Italy  also  imported  26,432  quintals  of  varnish  free 
from  spirit,  worth  £150,920,  in  1910. 

PALM  OIL  is  extracted  from  the  fruit  of  certain  varieties  of  palm  (Elais  guineensis 
and  Elais  melanococca,  which  grow  in  Western  and  Central  Africa  and  in  America,  and 
Astrocaryum  acuale  and  Astrocaryum  vulgare,  growing  in  Guiana).  The  orange-brown 
fruit,  of  the  size  of  walnuts,  hangs  in  bunches.  The  pulp  constitutes,  according  to  the 
variety,  25  to  75  per  cent,  of  the  fruit,  which  contains  a  nut  also  yielding  an  oil 
(palm-nut  or  palm-kernel  oil). 

The  extraction  of  the  oil  in  the  districts  where  the  palm  is  grown  is  carried  out  in  an 
irrational  manner,  the  fruit  being  sometimes  heaped  up  until  it  putrefies  and  the  oil  then 
pressed  out.  In  other  cases  the  fruit  is  stored  and  compressed  in  excavations  in  clay  soil, 
being  left  to  putrefy  until  the  oil  separates  at  the  surface.  In  other  places  the  fruit  is 
fermented  for  a  month  and  then  heated  with  water,  so  that  the  pulp  becomes  detached 
from  the  stone  and  can  then  be  heated  and  pressed  again  with  water  until  the  fused  oil 
comes  to  the  top  and  can  be  decanted  off.  In  these  ways  more  than  one-half  of  the  oil  is 
lost,  and  machinery  is  now  being  introduced  for  detaching  and  disintegrating  the  pulp 
and  for  the  rational  pressing  of  the  latter. 

When  freshly  expressed  it  has  a  buttery  consistency,  an  intense  orange-yellow  colour 
and  a  faint  smell  of  violets  ;  the  colour  and  odour  persist  in  the  soap  prepared  from  it. 
It  can  be  decolorised  by  heating  it  when  exposed  to  the  air  and  light,  but  this  is  effected 
best  and  most  rapidly  by  fusing  and  heating  it  until  it  loses  the  water  remaining  from 
any  preliminary  heating  with  water  for  the  removal  of  impurities  ;  this  separates  from 
the  fused  mass  in  24  hours.  After  this  it  is  introduced  into  a  metal  vat  or  cylinder  provided 
with  a  cover  and  tube  for  carrying  the  gases  to  the  chimney  ;  the  fat  is  heated  to  100°  by 
means  of  an  indirect  steam  coil  and  a  vigorous  and  finely  divided  stream  of  air  passed 
through  the  oil  from  a  perforated  tube.  In  a  couple  of  hours'  time  decolorisation  is  com- 
plete ;  at  the  same  time  the  pleasant  odour  of  the  fat  remains,  although  it  is  destroyed  if 
the  fat  is  decolorised  by  simple  heating  to  220°. 

Chemical  decolorisation  is  often  employed,  the  oil  (1000  kilos),  already  purified  by 
treatment  with  water  and  by  fusion,  being  heated  in  a  boiler  to  50°,  at  which  temperature 
30  to  50  kilos  of  commercial  hydrochloric  acid  and  8  to  10  kilos  of  potassium  dichromate 
dissolved  in  18  to  20  litres  of  boiling  water  are  stirred  in.  After  15  to  20  minutes,  1  to  2 
kilos  of  sulphuric  acid  are  sometimes  added,  the  stirring  being  continued  until  the  oil 
becomes  limpid  ;  stirring  is  then  stopped  and  70  to  80  kilos  of  boiling  water  sprayed  on 
the  oil  to  wash  it.  After  standing  overnight,  the  water  is  decanted  off,  the  acid  separated 
from  below,  and  the  oil  washed  once  or  twice  by  boiling  with  water. 

Even  when  fresh  it  contains  12  per  cent,  of  free  fatty  acids,  and  as  it  becomes  older 
it  decomposes  spontaneously  with  increasing  ease,  separation  of  fatty  acids  (up  to  55  per 
cent.)  and  glycerine — which  can  be  extracted  with  water — taking  place.  Besides  free 
palmitic  acid,  the  principal  components  are  the  glycerides  of  oleic  and  palmitic  acids,  up 
to  1  per  cent,  of  stearic  acid,  a  little  linolic  acid,  and  about  1  per  cent,  of  heptadecylic  acid, 

Cl7H3402. 

The  colouring-matter  of  palm  oil  admits  of  various  characteristic  colour  reactions  : 
with  sulphuric  acid,  a  bluish  green  coloration  is  obtained,  whilst  mercurous  nitrate  colours 
it  first  canary -yellow,  then  pale  green,  and  finally  straw-yellow. 

II  26 


402 

Palm  oil  is  used  in  large  quantities  in  the  manufacture  of  soap  and  candles,  its  value 
being  related  to  the  melting-point  of  its  fatty  acids.  It  is  calculated  that  the  palm  oil 
placed  on  the  market  (that  is,  exclusive  of  the  large  amounts  consumed  where  produced) 
amounts  to  70,000  to  80,000  tons  per  annum.  Germany  imports  about  14,000  tons  of 
palm  oil  and  exports  14,000  to  18,000  tons  of  palm-nut  oil  and  coco-nut  oil.  Marseilles 
imports  18,000  to  20,000  tons  of  palm  oil  and  Austria-Hungary  3000  to  5000.  England 
imported  176,264  tons  of  crude  palm  oil  in  1909  and  199,438  tons  (£3,056,600)  in  1910, 
while  the  United  States  imported  42,000  tons  in  1910  and  21,000  tons  (£645,000)  in  1911, 
in  addition  to  5000  tons  of  palm-kernel  oil.  The  price  varies  with  the  year  from  40*.  to  52s. 
per  quintal.  The  best  qualities  of  palm  oil  are  from  Lagos  ;  then  come  those  of  Old 
Calabar,  Benin,  and  Acora  ;  while  among  the  more  impure  varieties  are  those  from  Gabun, 
Liberia,  and  the  Cameroons. 

PALM-NUT  OIL  (or  Palm-kernel  Oil)  is  obtained  by  crushing  and  then  either  pressing 
in  hydraulic  presses  or  extracting  with  solvents  the  stones  contained  in  palm  fruit  ;  freed 
from  shell,  the  seed  forms  9  to  25  per  cent,  of  the  weight  of  the  fruit  and  contains  43  to  55 
per  cent,  of  fat,  which  is  white  or  straw-coloured  and  free  from  fatty  acids  when  fresh, 
although  it  turns  rancid  fairly  easily  in  the  air  ;  it  melts  at  26°  to  30°. 

It  consists  of  about  1 5  to  25  per  cent",  of  triolein,  33  per  cent,  of  trigly  cerides  of  stearic, 
palmitic,  and  myristic  acids,  and  about  45  to  55  per  cent,  of  triglycerides  of  lauric  (in 
preponderance),  capric,  caprylic,  and  caproic  acids. 

It  bears  a  great  resemblance  to  coco-nut  oil,  even  in  the  property  of  its  soaps  of  taking 
up  large  proportions  of  water — as  much  as  600  per  cent,  (coco -nut  soap  up  to  1200  per 
cent.) — and  of  being  somewhat  soluble  in  solutions  of  salt.  The  total  quantity  of  palm 
nuts  placed  on  the  market  is  about  1,125,000  tons.  Germany  now  imports  about  200,000 
tons  of  palm  nuts  and  copra  (see  Coco-nut),  and  152,350  quintals  of  palm  oil  (in  1909)  ; 
Austria,  30,000  tons  ;  France,  about  7000  ;  and  England  about  60,000  ;  while  Italy  im- 
ported 81,920  quintals  of  palm  oil  of  the  value  of  £216,270  in  1910  (78,460  quintals  in 
1908). 

COCO-NUT  OIL  (or  Coco-nut  Butter)  is  obtained  from  the  coco-nuts  yielded  twice  a 
year  by  the  palms  Cocos  nucifera  and  Cocos  butyracea,  which  grow  abundantly  in  Africa, 
Ceylon,  Cochin  China,  and  the  Indies. 

The  coco-nut  is  oval  and  about  20  to  25  cm.  long  and  12  to  16  cm.  broad  ;  it  is  covered 
with  a  fibrous  mass,  used  for  making  matting,  cord,  and  baskets,  and  with  a  hard,  woody 
shell,  8  to  12  mm.  thick,  which  some  time  before  maturation  contains  a  sweetish,  watery 
liquid  (coco-nut  milk),  this  subsequently  disappearing  and  giving  place  to  a  soft  edible 
pulp.  The  latter  hardens  in  the  air  and  is  sold  under  the  name  of  copra  (60  to  70  per  cent, 
of  oil)  for  the  extraction  of  oil.  At  the  place  of  production  this  is  carried  out  in  a  very 
primitive  manner,  but  in  European  factories  the  dry  pulp  is  ground,  steeped  in  boiling 
water  and  pressed,  first  cold  and  then  hot. 

The  oil  is  nowadays  decolorised  with  bone-black  or  absorbent  earths  (magnesium  hydro- 
silicates),  and  in  the  white  form  thus  obtained  is  used  as  a  comestible  (coco-nut  butter  ; 
see  Margarine),  after  the  free  acids  have  been  removed  with  highly  concentrated  solutions 
of  caustic  soda  and  after  the  odorous  constituents  have  been  expelled  by  means  of  super- 
heated steam.  The  best  form  for  use  as  food  is  the  softer,  almost  liquid  butter  obtained  by 
the  first  pressing  in  the  cold.  Its  digestibility  is  equal  to  that  of  margarine  and  butter. 
If  it  contains  more  than  2  per  cent,  of  free  fatty  acids  (expressed  as  oleic  acid),  it  cannot 
be  used  for  food  and  then  goes  to  the  soap  factory  as  industrial  coco-nut  oil. 

Its  composition  is  variable,  and  of  the  unsaturated  acids  it  contains  only  oleic  acid 
(about  10  per  cent.),  while  glycerides  of  myristic  and  lauric  acids  are  present  in  large  quan- 
tities and  those  of  caproic,  caprylic,  and  capric  acids  to  the  extent  of  2  to  3  per  cent. 

The  pure  fat  contains  no  free  fatty  acids,  or  at  most  traces.  It  has  already  been  men- 
tioned that  it  gives  a  soap  separable  from  solution  only  by  very  large  quantities  of  salt  ; 
it  is,  however,  capable  of  absorbing  as  much  as  10  to  12  times  its  own  weight  of  water, 
and  is  hence  highly  valued  by  soap  manufacturers.  It  is  used  alone  for  culinary  purposes 
and  for  mixing  with  margarine  and  adulterating  cacao  butter. 

In.  its  analysis,  attention  is  paid  to  the  physical  and  chemical  constants  given  in  the 
Table  on  p  378. 

A  large  area  of  the  earth's  surface  (about  1,400,000  hectares)  is  under  coco-nut  palms, 
which  in  a  good  year  would  yield  960,000  tons  of  coco-nut  oil.  In  1905  about  300,000  tons 


COTTON-SEED    OIL,    MAIZE    OIL  403 

of  copra  were  placed  on  the  market,  and  in  1906  only  200,000  tons,  the  average  price 
being  £19  per  ton. 

England  imports,  on  an  average,  34,000  tons  of  copra  ;  France,  100,000  tons,  of  the 
value  of  £1,400,000  (the  exports  are  10, 700  tons)  ;  the  figures  for  Germany  are  given  above 
(see  Palm-nut  Oil).  England  imported  50,240  tons  of  crude  coco-nut  oil  and  17,708  tons 
of  the  purified  oil  in  1909,  and  53,968  tons  of  the  crude  and  50,021  tons  (£1,136,736)  of 
purified  oil  in  1910.  The  United  States  imported  25,000  tons  of  the  crude  oil  in  1910  and 
43,000  tons  (£785,000)  in  1911.  Italy  imported  344  quintals  of  coco-nuts  in  1910  and  also 
20,225  quintals  of  coco-nut  oil  of  the  value  of  £66,340  (in  1908,  13,840  quintals).  The 
Philippines  exported  115,130  tons  of  copra  in  1910,  two-thirds  of  it  to  France. 

VEGETABLE  TALLOW  (Chinese  Tallow)  is  obtained  by  pressing  the  fruit  (separated 
more  or  less  from  the  seeds)  of  Stillingia  sebifera  (tallow-tree),  which  grows  in  China,  Indo- 
China,  &c.  Pressing  of  the  seeds  (3  per  fruit)  yields  stillingia  oil,  which  is  to  some  extent 
drying  (iodine  number  more  than  135).  The  tallow,  however,  serves  well  for  making 
soap  and  has  an  iodine  number  of  about  30,  but  this  varies  somewhat  owing  to  variation 
of  the  amount  of  stillingia  oil  present.  The  tallow  melts  at  35°  to  44°,  and  is  sold  in  40- 
to  50-kilo  cakes  wrapped  in  straw. 

COTTON-SEED  OIL  is  obtained  by  pressing  the  shelled,  washed  seeds  of  the  cotton 
plant  (Gossypium  herbaceum  and  barbadeuse,  cultivated  in  North  America,  and  G.  religiosum, 
hirsutum,  and  arboreum,  cultivated  in  Egypt,  India,  China,  Siam,  &c.).  The  crude  oil  is 
reddish  brown  (sulphuric  acid  produces  a  red  coloration)  and  is  decolorised  by  stirring 
with  6  to  10  per  cent,  of  a  caustic  soda  solution  of  10°  to  15°  Be.  and  passing  through  it  a 
vigorous  current  of  air,  first  in  the  cold  (40  to  50  minutes)  and  then  when  heated  to  50° 
to  55°  by  indirect  steam.  It  is  then  allowed  to  deposit,  and  is  afterwards  washed  with 

10  per  cent,  of  salt  water  (at  10°  Be.)  to  remove  the  last  traces  of  soap,  decanted" off,  and 
passed  through  filter-presses  to  obtain  it  clear  and  of  a  fine  straw-yellow  colour.     The 
fatty  acids  separated  from  the  glycerides  of  cotton-seed  cil  contain  about  26  per  cent,  of 
oleic  acid,  47  per  cent,  of  linolic  acid  (the  oil  is  hence  partly  drying),  and  about  24  per  cent, 
of  saturated  fatty  acids  (palmitic  and  up  to  3  per  cent,  of  a  hydroxy-acid),  besides  a  small 
proportion  of  an  aldehydic  substance  (to  which  Becchi's  reaction  is  due).     It  contains  also 
1-5  per  cent,  of  a  non-saponifiable  sulphur  compound  and  apparently  a  chloro-compound. 

Tests  for  the  detection  of  cotton-seed  oil  in  other  oils  have  already  been  described 
(p.  397),  and  the  analysis  of  the  oil  is  carried  out  with  reference  to  the  constants  given 
on  p.  378. 

About  two-thirds  of  all  the  cotton-seed  oil  is  used  directly  or  indirectly  (as  adulterant) 
as  food  ;  the  remainder  (second  and  third  qualities)  serves,  with  palm  oil  and  coco-nut 
oil,  for  making  white  soaps,  although  in  some  cases  it  gives  rise,  after  some  time,  to 
yellowish  spots. 

The  world's  production  of  cotton  being  about  3,300,000  tons,  that  of  cotton-seed  should 
be  6,600,000  tons,  but  in  reality  is  only  5,000,000  tons  (three-fifths  in  the  United  States), 
and  the  United  States  produce  about  500,000  tons  of  cotton-seed  oil  (2,725,000  barrels  in 
1909  and  3,000,000  in  1910,  one-fourth  of  this  being  exported)  and  1,100,000  tons  of  cotton- 
seed cake. 

England  produces  about  70,000  tons  of  cotton-seed  oil,  imports  18,000  tons  (1905)  and 
exports  about  18,000  tons.  England  imported  17,560  tons  of  cotton-seed  oil  in  1909  and 
15,950  tons  (£562,672)  in  1910,  and  also  690,000  tons  (£4,866,000)  of  cotton-seed  in  the 
latter  year.  In  1906,  France  imported  more  than  220,000  tons  of  the  seed  and  46,000  to 
50,000  tons  of  the  oil.  The  United  States  exported  85,000  tons  (£2,638,200)  of  cotton-seed 

011  in  1910  and  155,000  tons  (£4,367,800)  in  1911.   Germany  imported  about  17,000  tons  of 
the  seed  and  about  55,000  tons  of  the  oil  in  1904.     In  1906  Austria  imported  20,500  tons  of 
cotton-seed  oil.     Italy  imported  31,328  quintals  of  the  oil  in  1907,  108,117  quintals  in 
1908,  306,250  quintals  in  1909,  and  35,801  quintals— of  the  value  of  £117,430— in  1910. 

MAIZE  OIL  (in  America,  Corn  Oil)  is  now  prepared  in  large  quantities  in  America  and 
Italy  from  maize  germs,  which  are  separated  during  grinding.  These  germs  contain  40  to 
50  per  cent,  of  oil,  and  after  being  pressed  hot  leave  an  excellent  cake  for  cattle-food 
(10s.  to  12*.  per  quintal).  The  dense  oil  has  a  fine  golden  yellow  colour  and  a  faint  odour 
of  maize,  and  serves  well  for  soap-making  and  for  adulterating  edible  oils  and  linseed  oil. 
That  obtained  by  extracting  the  dried  grains  from  spirit  manufacture  (see  p.  153)  is  reddish 
brown,  and  is  used  for  burning  and  as  a  lubricant  when  mixed  with  olive  and  mineral 


404  ORGANIC    CHEMISTRY 

oils,  but  is  not  used  alone  as  it  tends  to  resinify.  As  a  drying  oil  it  has  no  great 
value. 

The  fatty  acids  of  the  glycerides  of  maize  oil  are  :  stearic  and  palmitic  (4  to  25  per 
cent.),  oleic  (about  40  per  cent.),  linolic  and  linolenic  (about  45  per  cent.,  so  that  the  oil 
is  partly  a  drying  one),  and  small  proportions  of  arachic,  hypogaeic,  caproic,  caprylic, 
and  capric  acids  ;  the  oil  contains  also  about  1-2  per  cent,  of  lecithin  and  1-4  per  cent,  of 
non-saponifiable  substances,  mostly  cholesterol  or,  more  precisely,  sitosterol,  identical  with 
that  obtained  from  wheat  and  rye. 

If  in  North  America  (Illinois)  alone  the  oil  were  extracted  from  the  germs  of  all  the 
maize  produced  (about  6,000,000  tons — the  world's  total  production  being  over  7,500,000 
tons,  900,000  of  this  in  Italy),  more  than  250,000  tons  of  the  oil  should  be  obtained.  But 
only  about  40,000  tons  of  maize  oil  are  produced  at  the  present  time,  about  one-half  of  it 
being  exported. 

SESAME  OIL  (Gingelly  Oil,  Teel  Oil)  is  obtained  from  the  seeds  of  Sesamum  indicum 
(brown,  oval,  flat  seeds,  4  mm.  long,  2  mm.  broad,  and  1  mm.  thick)  and  of  Sesamum 
orientale  (violet-brown  or  black),  the  latter  giving  as  much  as  50  per  cent,  of  oil  when 
pressed  once  in  the  cold  and  twice  hot.  The  first  oil  expressed  serves  as  a  food  for  250 
millions  of  the  inhabitants  of  India,  where  the  area  under  sesame  exceeds  ten  millions 
of  acres  (i.e.  40,000,000  hectares).  The  exportation  of  sesame  seeds  from  India  amounts 
to  about  1,200,000  quintals  annually,  nearly  all  of  this  being  directed  to  the  Marseilles 
market,  whence  other  countries  are  supplied.  The  Levant  produces  about  one-tenth  as 
much  as  India,  and  a  little  is  produced  in  Africa,  China,  and  Japan.  In  France  the  sesame 
oil  industry  is  declining  owing  to  the  obstinate  empiricism  of  the  older  manufacturers 
and  to  the  almost  prohibitive  Customs  duties  of  various  countries,  but  more  than  1000 
truckloads  of  the  oil  are  still  exported  per  annum.  Germany  imported  in  1890  only 
140,000  quintals  of  the  seeds,  but  in  1903  615,000  quintals,  and  in  1905  nearly  465,000. 
Austria-Hungary  imports  on  an  average  150,000  quintals  yearly.  Italy  imported  174,722 
quintals  of  sesame  and  arachis  seeds  in  1908,  309,000  in  1909,  and  386,000,  worth  £617,400, 
in  1910. 

Sesame  cake  (dark  or  pale),  so  largely  used  as  cattle-food,  has  the  composition  :  water, 

10  to  12  per  cent.  ;  protein  substances,  37  to  39  per  cent.  ;  fat,  9  to  10-5  per  cent.  ;  and 
ash,  9-5  per  cent. 

Sesame  oil  has  a  golden -yellow  colour,  that  from  the  Levant  being  the  paler  ;  it  consists 
of  glycerides  of  stearic,  palmitic,  oleic,  and  linolic  acids,  78  per  cent,  of  the  fatty  acids 
being  liquid  with  an  iodine  number  of  140.  The  physical  and  chemical  constants  are  given 
in  the  Table  on  p.  378,  and  the  characteristic  reactions  for  detecting  it  when  mixed  with 
other  oils  on  p.  397.  It  is  dextro-rotatory  (  +  0-8°  to  +  2-4°). 

The  characteristic  reactions,  especially  the  colorimetric  ones,  are  due  to  special 
components,  such  as  sesamin ;  a  laevo -rotatory  alcohol,  sesamol,  C2GH440,  |HyO, 
which  gives  Baudouin's  reaction  (p.  384),  and  the  methylene  ether  of  hydroxyhydro- 
quinone,  C7H6O3. 

Sesame  oil  is  used  in  the  manufacture  of  oleomargarine  and  soap  and  as  burning  oil. 

ARACHIS  OIL  (Earthnut  Oil,  Peanut  Oil)  is  obtained  from  the  seeds  of  Arachis  hypo- 
gcea,  cultivated  in  Brazil,  the  Congo,  and  India,  and  to  some  extent  in  Spain,  France,  and 
Italy.  The  shelled  seeds  give  30  to  35  per  cent,  of  oil.  In  1908  Italy  imported  4735  quintals 
of  arachis  oil,  in  1909  46,833  quintals,  and  in  1910  50,820  quintals,  of  the  value  of  £182,960. 
The  oil  obtained  by  the  first  cold  pressing  is  almost  colourless,  has  a  slight  flavour  of  beans, 
and  is  largely  used  as  a  comestible  and  for  adulterating  olive  oil,  although  it  readily  turns 
rancid.  The  second  pressing  in  the  cold  gives  burning  oil,  and  the  third,  in  the  hot,  oil  for 
soap-making.  The  liquid  components  contain  triolein  and  trilinolin  ;  the  presence  of 
hypogseic  acid  is  uncertain  ;  the  solid  constituents  are  composed  of  triglycerides  of  ligno- 
ceric  acid,  and  to  a  less  extent  of  arachic  acid  (5  per  cent,  of  the  oil).  In  olive  oil  arachis 

011  is  detected  by  Renard's  test,  as  modified  by  Tortelli  and  Ruggeri  and  by  Fachini  and 
Dorta  (see  p.  397). 

SOJA  BEAN  OIL  (Chinese  Bean  Oil)  is  extracted  from  the  beans  of  Soj'a  liispida  (or 
ftoja  japonica  or  Phaseolus  hispidus),  which  are  cultivated  in  China  and  Japan  (Formosa). 
The  crushed  beans  are  heated  in  jute  bags  over  jets  of  steam  and  then  pressed.  A  large 
part  of  the  oil  is  used  for  soap-making.  After  purification  by  standing,  the  oil  has  a  sp.  gr. 
0-9255  at  15°  ;  acidity,  0  ;  saponification  number,  193-2  ;  iodine  number,  135  ;  Hehner 


GRAPE-    AND    TOMATO-SEED    OILS         405 

number,  95-95  ;  Reichert-Meissl  number,  0-45  ;  Maumene  number,  86  to  87  ;  index  of 
refraction,  1-4750  at  20°  ;  solidification  point,  —  8°  to  —  16°  ;  melting-point  of  the  fatty 
acids,  27°  ;  and  solidification-point  of  the  fatty  acids,  22°  (Oettinger  and  Buckta,  1911). 
The  exportation  of  the  oil  from  China  amounts  to  60,000  tons  per  annum. 

GRAPE-SEED  OIL.  The  seeds  of  the  grape  contain  10  to  20  per  cent,  of  oil  (more 
in  white  and  sweet  grapes).  They  are  separated  from  the  skins  by  drying  in  the  sun  or  in 
ovens  and  then  beating.  The  sieved  seeds  are  dried  completely,  ground,  steeped  in  10 
per  cent,  of  water,  heated,  and  pressed  ;  the  cake  is  broken  up,  treated  with  20  to  25  per 
cent,  of  water,  and  pressed  again,  this  treatment  being  repeated  go  that  all  the  oil  may 
be  extracted.  The  oil  can  also  be  extracted  by  means  of  solvents  (benzine  or  carbon 
disulphide).  When  dark-coloured  (extracted  with  solvents),  it  can  be  readily  decolorised 
with  animal-black.  It  has  not  a  very  pleasant  odour  and  is  rather  bitter  (if  expressed  in 
the  hot). 

.  This  oil  consists  of  glycerides  mainly  of  linolic  acid,  together  with  those  of  solid  fatty 
acids  (10  per  cent.),  and  a  little  erucic,  linolenic,  and  ricinoleic  acids.  It  has  the  sp.  gr. 
0-9202  to  0-9350. 

It  has  slight  drying  properties  and  solidifies  between  —10°  and  —15°;  itsgaponificalion 
number  is  178  to  180  ;  iodine  number,  94  to  96-5  ;  Wollny  number,  0-46  ;  Maumene 
number,  52  to  54  ;  and  butyro-refractometer  reading,  60  at  40°.  The  acetyl  number  of  the 
fatty  acids  varies  from  43  to  144,  according  to  the  extent  of  oxidation  ;  it  thus  resembles 
castor  oil  to  some  extent,  so  that  it  is  recommended  for  the  manufacture  of  sulphoiicinate 
(see  p.  327). 

The  pure  oil  expressed  in  the  cold  is  used  as  a  food,  and  the  other  varieties  for  soap- 
making.  But  if  purified  with  sulphuric  acid  it  serves  well  as  a  lighting  oil,  not  so  much 
on  account  of  its  luminosity,  which  is  rather  low,  but  more  especially  because  it  gives  a 
smokeless  flame. 

After  the  removal  of  the  fat,  the  cake  contains  10  to  15  per  cent,  of  water,  14  to  18 
per  cent,  of  protein  substances,  8  to  10  per  cent,  of  fat,  and  6-5  to  7  per  cent,  of  ash,  and  is 
used  as  cattle-food. 

In  Italy  the  extraction  of  grape-seed  oil  is  capable  of  considerable  development.  A 
few  factories  have  already  been  erected  in  Southern  Italy  and  in  the  North  ;  some  of 
the  works  treat  a  certain  amount  of  the  seed.  Seeds  obtained  from  distilled  vinasse  are 
somewhat  diminished  in  value. 

TOMATO-SEED  OIL.  In  Italy  393,000  tons  of  tomatoes  were  produced  in  1909  and 
335,000  tons  in  1910.  In  the  province  of  Parma  84,000  tons  are  treated  annually,  and  the 
residues  (seeds,  &c.)  now  yield  600  tons  of  oil  (drying  oil  of  the  cotton-seed  type).  The 
refuse  from  tomato-ketchup  factories  (about  5  per  cent,  of  the  weight  of  the  tomatoes) 
contains  about  70  per  cent,  of  aqueous  liquid,  6  to  8  per  cent,  of  dry  skins,  and  22  to  24 
per  cent,  of  dry  seeds. 

One  hundred  kilos  of  tomatoes  give  95  kilos  of  liquid  juice,  which  is  concentrated  for 
preserve,  and  1  per  cent,  of  dry  seeds  containing  2  3  per  cent,  of  oil,  18  per  cent.  (180  grms.) 
being  extractable  by  pressure  ;  the  remaining  820  grms.  consists  of  cake  (5-2  nitrogen, 
12  per  cent,  fat,  22-7  per  cent,  cellulose,  21  per  cent,  non-nitrogenous  extractives,  6-5 
per  cent,  ash,  0-22  per  cent,  of  dry  skins,  and  3-78  per  cent,  of  aqueous  liquid  adhering  to 
the  moist  residues). 

The  oil  expressed  in  the  cold  from  sound  seeds  is  straw-yellow,  and  with  20  per  cent, 
of  tallow  gives  a  good  washing  soap. 

Analysis  of  the  oil  gives  the  following  results  (Fachini) :  density  at  15°,  0-9215  ;  refrac- 
tive index,  1-4765  ;  acid  number,  0-46  ;  saponification  number,  191-6  ;  iodine  number, 
114  ;  iodine  number  of  the  fatty  acids,  122-7  ;  iodine  number  of  the  liquid  fatty  acids, 
142-2  j  Hehner  number,  93-8  ;  acetyl  number,  20-4. 

TREATMENT  OF  FATS  FOR  THE  MANUFACTURE  OF 
SOAP  AND  CANDLES 

Candles  are  mostly  made  from  solid  fatty  acids  (stearic  and  palmitic)  obtained  by 
decomposing  fats  and  oils  into  glycerine  and  fatty  acids  and  pressing  from  the  latter  the 
liquid  fatty  acids,  which  are  used,  either  alone  or  together  with  the  solid  acids,  for  soap- 
making.  Liquid  oils  and  soft  fats,  which  contain  little  stearic  and  palmitic  acids,  are 


406 


ORGANIC    CHEMISTRY 


hence  used  not  for  candles  but  only  for  soap,  but  the  stiffer  fats  are  often  treated  in  one 
and  the  same  works  for  making  candles  and  soap. 

The  resolution  of  fats  into  acids  and  glycerine  is  carried  out  in  very  varied  ways  :    by 
means  of  lime,  sulphuric  acid,  superheated  steam,  or  biological  or  catalytic  methods. 

(1)  Saponification  with  Lime  and  Separation  of  the  Solid  Fatty  Acids.  Theoretically 
100  kilos  of  fat  (see  p.  377)  require  9-5  kilos  of  lime  for  hydrolysis,  but  when  this  process 
was  first  used  industrially  by  Milly  in  1834  as  much  as  15  per  cent,  of 
lime  was  used,  so  that  a  very  large  amount  of  sulphuric  acid  was  con- 
sumed in  liberating  the  fatty  acids  from  the  calcium  f  oaps  formed, 
while  fatty  acids  were  carried  down  by  the  enormous  quantities  of 
calcium  sulphate  formed  and  hence  lost. 

On  this  account  the  process  was  not  used,  but  Milly  showed  later 
(1855)  that,  by  heating  in  an  autoclave  under  pressure  instead  of  in  open 
pans,  the  amount  of  lime  could  be  reduced  to  2  to  3  per  cent. — that  is, 
less  than  the  theoretical  quantity — and  yet  practically  complete  saponi- 
fication  effected  (see  p.  370).  Indeed,  after  1  hour  64  per  cent,  of  the 
fat  remained  unsaponified  ;  after  2  hours,  24  per  cent.  ;  after  4  hours, 
15  per  cent.  ;  after  6  hours,  9  per  cent.  ;  after  9  hours,  2  per  cent.  ; 
and  after  12  hours,  0-7  per  cent. 

The  saponification  is  now  carried  out  in  large  vertical  copper  auto- 
claves (Fig.  268)  (5  to  6  metres  high,  1  to  1-2  metre  in  diameter,  of 
sheet  copper  15  to  20  mm.  thick),  into  which  are  passed  several  quintals 
(up  to  20)  of  the  fused  fat  from  the  tank,  A  (Fig.  269),  and  then  about 
one-third  as  much  milk  of  lime,  containing  2  to  3  per  cent,  of  lime 
(calculated  on  the  fat),  from  the  vessel  B,  The  heating  is  continued  for 
6  to  8  hours  at  a  pressure  of  8  to  10  atmos.,  steam  free  from  air  being 
passed  in,  first  at  low  pressure  from  the  generator,  D,  and  then  at 
high  pressure  (10  to  12  atmos.)  by  the  tube,  e  (Fig.  270),  reaching  to  the 
bottom  of  the  autoclave  and  terminating  in  a  perforated  coil.  The  steam 
alone  keeps  the  mass  mixed  without  the  special  stirrers  formerly  used,  if  the  precaution 
is  taken  of  allowing  a  little  steam  to  escape  continually  from  a  tap  at  the  top.  At  the 
end  of  the  operation  the  steam  is  shut  off,  and  when  the  temperature  has  fallen  to  125° 
to  130°  (about  3-5  atmos.  pressure)  the  internal  pressure  is  utilised  to  discharge  first  of  all 
the  aqueous  glycerine  from  below  by  opening  the  valve,  c,  connected  with  a  tube  reaching 
to  the  bottom  of  the  autoclave.  In  a  similar  manner  the  fused  and  subdivided  calcium 


FIG.  268. 


FIG.  269. 


soap  mixed  with  free  fatty  acids  is  forced  into  the  tank,  E,  where  a  further  quantity  of 
aqueous  glycerine  separates,  or  the  calcium  soap  is  passed  directly  to  the  lead-lined  vessels, 
F,  where  it  is  decomposed  by  a  sufficient  quantity  of  sulphuric  acid  to  neutralise  all  the 
lime  added.1  After  shaking,  the  gypsum  is  deposited  and  can  be  separated,  and  the  fatty 

1  During  recent  years  several  factories  have  replaced  lime  by  magnesia  (calcined  natural  carbonate),  which 
possesses  various  advantages  :  when  it  is  used  in  the  proportion  of  1-5  to  2  per  cent.,  a  pressure  of  4  to  5  atmo- 
spheres is  sufficient  to  produce  complete  saponification,  since  the  magnesium  soap  formed  gradually  emulsifies 
and  almost  dissolves  in  the  remaining  fat,  which  is  thus  easily  resolved  by  the  water  and  magnesia.  Then,  too, 
decomposition  of  the  magnesium  soap  with  sulphuric  acid,  instead  of  giving  an  insoluble  and  useless  salt  (calcium 
sulphate,  which  always  retains  a  little  fat),  gives  magnesium  sulphate,  which  is  soluble  in  water,  readily  separable 


HYDROLYSIS    OF    FATS 


407 


acids,  which  float,  are  washed  several  times  with  hot  water  and  then,  if  the  fatty  acids 
are  distilled — as  is  done  in  certain  factories  where  dark  fats  are  treated — they  are  forced 
by  a  pump,  G,  to  the  tank,  H.  The  latter  feeds  a  cast-iron  or  copper  (this  is  considerably 
attacked)  boiler,  K,  which  is  heated  partly  by  almost  direct-fire  heat  and  partly  by  super- 
heated steam  (at  180°  to  230°)  passed  into  the  interior  from  the  superheater,  J.  The  steam 
carries  the  fatty  acids,  which  distil,  into  the  tinned  copper  condensing  coil,  L  ;  these  acids 
finally  collect  in  a  white  condition,  together  with  condensed  water, 
in  8,  while  the  non -condensed  gases  are  evolved  from  the  tube,  M 
(see  later  :  Decomposition  with  Sulphuric  Acid). 

Where  the  fatty  acids  are  not  distilled,  they  are  solidified  by 
passing  them  into  a  number  of  superposed  tin-plate  pans  (Fig.  271) 
fed  by  the  tubes,  D,  from  the  fused  fatty-acid  tank,  F.  When  all  the 
pans  are  full,  the  tubes,  D,  are  closed  with  wooden  plugs,  E,  and  in 
24  hours  many  of  the  pans  contain  solid  cakes,  consisting  of  a 
mixture  of  solid  stearic  and  palmitic  acids  and  liquid  oleic  acid.  In 
order  to  separate  the  latter,  the  cakes  are  wrapped  in  woollen  or 
camel's-hair  or  goat's-hair  cloths  and  are  then  placed  between  metal 
plates  and  pressed,  first  in  the  cold  with  a  pressure  gradually  in- 
creasing to  200  to  260  atmos.  A  second  pressing  at  40°,  either  in 
the  same  press  or  in  a  horizontal  press,  results  in  the  almost  com- 
plete separation  of  the  oleic  acid,  which,  however,  retains  in  solution 
a  little  palmitic  and  stearic  acids.  The  latter  acids  are  separated  by 
cooling  the  oleic  acid  and,  after  some  time,  filtering  or  decanting  off 
the  oleine  (p.  298),  which  is  then  put  on  the  market  or  used  for  soap- 
making. 

The  solid  white  cakes  of  stearic  and   palmitic  acids,  freed  from 
the  dark  edges,  bear  the  commercial  name  of  stearine  and  melt  at 
56°  to  56-5°.    These  are  often  melted  again,  washed  with  warm  water, 
poured  into  pans  to  solidify,  and  then  pressed  hot  in  hydraulic    presses  so  as  to  remove 
the  final  portions  of  oleic  acids  ;   this  product,  known  as  double  stearine,  melts  at  57-5° 
to  58°. 

The  solidification  of  the  crude  acids,  after  liberation  by  sulphuric  acid,  is  now  effected 
more  rapidly  and  more  perfectly  by  pass- 
ing the  fused  acids  at  g  (Figs.  272  and  273) 
into  a  casing  into  which  dips  a  large, 
rotating,  double-walled  cylinder.  Between 
the  walls  flows  a  non -congealing  solution 
like  that  from  an  ice  machine  (see  vol.  i, 
p.  231),  and  the  layer  of  fatty  acid  solidi- 
fying at  the  surface  is  detached  by  means 
of  a  scraper,  h,  and  falls  into  a  cooled 
box,  F,  connected  with  the  pump,  P,  and 
functioning  as  a  filter-press.  This  process 
of  the  firm  of  Petit  Fieres  has  now  been 

improved  by  replacing  the  cylinder  by  a       [ijft — ?  t — T$\ — i  \ — 7 
highly   cooled   toothed  wheel.     In    some 
cases,  also,  channelled  cylinders  are  used, 
whilst  in  others  the  liquid  fatty  acids  are  FIG.  271. 

withdrawn  from  the  cold  pasty  mass  con- 
taining the  mixture  of  liquid  oleine  and  the  stearine  in  small  crystals,  by  immersing  in  the 
mass  a  rotating  vertical  cylinder  formed  of  metallic  gauze  and  covered  with  a  well- 
stretched  cloth  ;  inside  the  cylinder  the  pressure  is  reduced  by  means  of  a  suction-pump, 
so  that  the  liquid  oleic  acid  is  sucked  in,  while  the  stearic  acid  is  gradually  scraped  from 
the  surface  of  the  cylinder  and  pressed  in  a  hydraulic  press. 

Messrs.  Lanza  Bros,  of  Turin,  instead  of  separating  the  liquid  from  the  solid  fatty 
acids  by  means  of  hydraulic  presses,  suggest  emulsifying  and  dissolving  the  liquid  acids 
with  solutions  of  sulpho -oleic  acid,  so  that  they  separate  at  the  surface,  while  crystals 

by  simple  decantation  arid  in  some  cases  utilisable.  For  similar  reasons,  zinc  oxide  is  now  used  in  some  of  the 
Italian  factories.  Bottaro  (1908)  has  suggested  the  use  of  sulphurous  anhydride  to  decompose  the  calcium  soap 
from  the  autoclave. 


ORGANIC    CHEMISTRY 

of  the  solid  fatty  acids  collect  underneath  (Ger.  Pat.  191,238).  The  sulpho-oleic  acid 
is  prepared  by  shaking  100  parts  of  oleic  acid  with  50  parts  of  sulphuric  acid  of  66°  Be. 
in  the  cold  and  then  diluting  with  4000  parts  of  water. 

The  decomposition  of  fats  by  lime  in  an  autoclave  at  not  too  high  a  pressure  has  the 
advantage  of  giving  the  fatty  acids  in  a  sufficiently  clear  condition  to  render  distillation 
useless  ;  the  resulting  glycerine  and  stearine  are  also  clear.1 

(2)  Decomposition  with  Sulphuric  Acid  (proposed  by  Achard  in  1777  and  then  by 
Fremy  in  1836).  This  method  is  now  used  more  especially  for  very  dark  fats,  which 
should,  however,  be  freed  from  impurities,  dried  by  fusion  at  120°,  and  decanted  after 
long  standing.  The  fused  fat  is  introduced  into  a  double-walled,  lead-lined,  copper  or 

iron  boiler  fitted  with  a  hood  for 
carrying  off  the  sulphur  dioxide 
which  is  always  evolved.  Accord- 
ing to  the  nature  of  the  fat,  it  is 
heated  with  5  to  10  per  cent,  of 
concentrated  sulphuric  acid  at 
120°  for  1  to  \\  hour,  steam  being 
passed  through  the  jacket  and 
the  mass  kept  mixed  by  a  current 
of  air  passing  through  it.  The 
operation  is  finished  when  a  test 
portion,  placed  on  a  dark  plate, 
crystallises  on  cooling  ;  the  mass 
is  then  passed  into  large  wooden 
vats  and  heated  with  water  until 
the  emulsion  first  formed  is  re- 
solved into  two  layers,  the  gly- 
cerine below  (this  is  separated 
FIG.  272.  FIG.  273.  and  freed  from  sulphuric  acid  by 

means   of   lime)  and  the    acids 

above.  The  latter  is  subsequently  boiled  several  times  with  water  until  the  excess  of 
sulphuric  acid  is  removed,  the  sulphuric  ethers  of  oleic  acid  being  decomposed  with 
formation  of  solid  hydroxystearic  acid.  The  resulting  fatty  acids  are  dark  in  colour, 
since  they  retain  in  solution  the  impurities  of  the  fat  partially  carbonised  by  the 
sulphuric  acid  ;  to  purify  and  whiten  them,  they  are  distilled  with  superheated  steam, 
as  described  above  (see  also  Fig.  269) ;  the  first  and  last  portions  which  distil  are  the 
more  coloured  and  these  are  redistilled.  Hirzel  (Ger.  Pat.  172,224,  1906)  has  devised  an 
arrangement  for  continuous  distillation,  all  that  is  required  being  a  boiler  of  moderate 
size  into  which  the  crude  fatty  acids  are  run  in  a  constant  stream  ;  the  pure  acids  distil 
over,  while  the  tar  remaining  at  the  bottom  of  the  boiler  is  discharged. 

Redistillation  of  this  tar  gives  a  final  residue  of  black  stearine  pitch,  amounting  to 
about  2  per  cent,  of  the  fatty  acids  distilled.  In  some  works  the  fatty  acids  are  distilled 
in  a  vacuum  at  a  temperature  not  exceeding  240°,  higher  temperatures  than  this  giving 
a  coloured  product ;  the  acrolein  and  hydrocarbons  given  off  are  condensed. 

The  fatty  acids  obtained  by  distillation  are  separated  into  liquid  and  solid  by  pressure 
in  hydraulic  presses,  liquid  distilled  oleine  and  white,  solid  distilled  stearine  being  thus 
obtained.  This  oleine  always  contains  a  little  acrolein  and  hydrocarbons,  as  the  crude 
fatty  acids  which  are  distilled  invariably  include  a  small  proportion  of  non-saponified 
neutral  fat.  On  the  other  hand,  distillation  results  in  the  formation  of  an  increased 
amount  of  solid  fatty  acids  (about  15  to  18  per  cent.),  since  sulphuric  acid  converts  oleic 

1  During  recent  years,  industrial  application  has  been  made  of  the  Krebitz  process  (Ger.  Pat.  155,108,  1902), 
which  is  a  simplification  of  the  lime  process  with  direct  production  of  soda  soap,  and  is  attended  by  considerable 
saving  in  fuel,  caustic  soda,  and  plant.  To  the  fused  fat  is  added  the  necessary  quantity  of  lime  (10  to  12  per 
cent.  CaO)  mixed  to  a  paste  with  three  to  four  times  its  weight  of  water,  the  mass  being  well  mixed,  boiled  for 
five  minutes,  covered,  and  allowed  to  stand  overnight.  By  this  means^saponification  is  complete  and  a  calcium 
soap  is  obtained  which  can  be  readily  ground  up  in  a  mill.  When  this  is  washed  in  a  vat  with  a  perforated  bottom, 
the  first  portion  of  hot  wash-water  removes  the  major  part  of  the  glycerine  as  a  solution  of  10  to  20  per  cent, 
concentration,  while  a  second  washing  gives  a  more  dilute  glycerine  solution  which  is  used  for  the  first  washing 
of  the  calcium  soap  of  a  subsequent  operation.  When  treated  in  the  hot  with  sodium  carbonate  solutions,  the 
calcium  soap  yields  soda  soap  and  calcium  carbonate,  which  require  skilled  manipulation  for  their  proper  separa- 
tion. In  this  case  also,  fusion  and  treatment  with  hot  water  is  employed  for  the  complete  removal  of  impurities. 
This  process  is  not  applicable  to  the  manufacture  of  soft  soaps. 


ENZYMIC    HYDROLYSIS  409 

acid  partly  into  the  corresponding  sulphuric  ether,  which  yields  solid  hydroxystearic 
acid  when  boiled  with  water  : 


C17H33'C02H  +  H2SO4 


.gQ  jj  +  H20  =  H2S04  +  Ci7H34<^Qj| 

During  the  distillation  with  superheated  steam,  the  hydroxystearic  acid  is  transformed 
almost  entirely  into  iso-oleic  acid  (see  p.  299).  It  must,  however,  be  borne  in  mind  that 
hydroxystearic  acid  is  not  Very  good  for  making  candles,  as  it  accumulates  in  a  fused 
state  in  the  cup  formed  by  the  burning  candle  round  the  wick  ;  further,  when  melted 
with  stearic  acid  it  tends  to  separate  in  layers  instead  of  giving  a  homogeneous  mass. 

In  order  to  obtain  a  greater  proportion  of  solid  fatty  acids,  some  works  combine  these 
two  systems  of  saponifying  by  means  of  lime  and  acid.  The  saponification  is  first  carried 
out  in  autoclaves  in  the  ordinary  way,  but  not  to  completion,  the  acids  and  the  remaining 
fat  (4  to  5  per  cent.)  being  then  separated  by  means  of  sulphuric  acid  ;  the  fatty  acids 
and  fat  are  dried  and  completely  saponified  with  2  to  2-5  per  cent,  of  concentrated  sulphuric 
acid  at  a  temperature  of  110°  to  120°  maintained  for  an  hour.  The  resulting  fatty  acids 
are  not  distilled  but  are  simply  washed  with  boiling  water,  being  thus  rendered  rich  in 
solid  hydroxystearic  acid  ;  this  process  also  yields  a  much  purer  glycerine. 

L.  Fournier  (Fr.  Pat.  262,263)  has  suggested  a  method  of  increasing  the  amount  of 
solid  fatty  acids  by  effecting  the  sulphonation  with  concentrated  sulphuric  acid  in  a  carbon 
disulphide  solution  of  the  fat,  the  reaction  then  proceeding  immediately  without  heating.1 

(3)  Hydrolysis  by  Hot  Water  under  Pressure  (proposed  by  Tilghmann  in   1854) 
is  but  little  used  owing  to  the  low  yields  obtained  and  the  very  high  pressures  required. 
The  fat,  emulsified  with  water,  is  circulated  in  coils  arranged  in  a  furnace  so  as  to  attain 
a  temperature  of  300°  to  350°. 

Direct  distillation  of  fats  with  superheated  steam  and  collection  of  the  glycerine  and 
fatty  acids  in  the  distillate  always  gives  low  yields. 

(4)  The  Biological  or  Enzymic  Process  has  been  applied  industrially  since  1902,  as  a 
result  of  the  work  of  W.  Connstein,  E.  Hoyer,  and  H.  Wartenberg,  and  is  based  on  the 
observations  of  Green  and  of  Sigmund  (1891)  according  to  which,  when   oily  seeds  are 
pounded  with  water,  fatty  acids  are  gradually  liberated  by  the  action  of  lipolytic  enzymes 
(see  p.  112).     It  is  found  that  the  most  active  enzymes  are  those  of  castor  oil  seeds  (in 
which  they  occur  to  the  extent  of  70  parts  per  1000  of  fat),  especially  after  removal  of 

1  Transformation  of  Oleic  Acid  into  Solid  Fatty  Acids.  For  some  years  (about  1877-1885),  oleic  acid 
was  converted  on  an  industrial  scale  in  France  and  England  (by  the  process  of  Olivier  and  Radisson)  into  solid 
palmitic  add  by  utilising  Varrentrapp's  reaction,  according  to  which  this  change  is  almost  quantitative  on 
fusion  with  solid  caustic  potash  (see  pp.  290  and  299)  :  C1SHS1O,  +  2KOH  =  H2  +  CH,-CO2K.  +  C,,H81OZK. 
But  the  greasiness  and  unpleasant  odour  of  the  candles  obtained  compared  with  those  made  from  stearine,  the 
necessity  of  distilling  the  resultant  dark  acid,  and  the  difficulty  of  eliminating  all  the  acetic  acid,  led  to  the 
abandonment  of  this  process.  Also  de  Wilde  and  Reychler's  process  for  transforming  oleine  into  stearine  by  heating 
in  an  autoclave  at  260°  to  280°  with  1  per  cent,  of  iodine  or  chlorine  or  bromine  seems  to  have  been  given  up  in 
practice  since  1890,  the  yield  being  less  than  75  per  cent,  (the  combined  chlorine  was  eliminated  by  heating  under 
8  to  10  atmos.  in  presence  of  zinc  dust  or  iron,  and  then  decomposing  the  metallic  soap). 

The  industrial  transformation  of  oleic  acid  into  solid  elaidic  add  by  treatment  with  a  little  nitrous  acid  (see 
p.  299)  does  not  give  satisfactory  practical  results,  first  because  elaidic  acid  is  not  a  very  good  material  for 
candle-making,  and  also  because  the  reaction  succeeds  well  only  with  fairly  pure  and  fresh  oleic  acid  and  not  with 
the  commercial  acid  (partly  polymerised).  Max  v.  Schmidt  treats  10  parts  of  oleic  acid  with  1  of  zinc  chloride 
at  180°,  then  decomposes  the  zinc  soap  by  boiling  first  with  dilute  HC1  and  afterwards  with  water  and  finally 
distils  the  fatty  acids,  which  can  be  separated  into  liquid  and  solid  by  means  of  hydraulic  presses.  By  this  process 
Beuedikt  (1890)  obtained  75-8  per  cent,  of  stearolactone,  C,8H34O2  (the  internal  anhydride  of  y  -hydroxystearic 
add),  15-7  per  cent,  of  iso-oleic  acid,  and  8-5  per  cent,  of  other  saturated  acids. 

K.  Hartl,  jun.  (Ger.  Pat.  148,062,  1903),  in  order  to  avoid  the  browning  produced  by  the  action  of  sulphuric 
acid  on  the  impurities  of  the  oleic  acid,  does  not  treat  the  oleine  directly  with  concentrated  sulphuric  acid  (as 
had  long  been  the  custom  ;  see  Shukoff,  Ger.  Pat.  150,798,  1902),  but  first  distils  the  oleic  acid  in  steam  and  after- 
wards treats  it  with  sulphuric  acid  of  58°  to  60°  Be.  (e.g.  at  a  temperature  of  60°  to  80°  and  using  1  mol.  of 
sulphuric  acid  per  1  mol.  of  oleic  acid)  ;  the  resulting  fatty  acids  are  then  washed  and  decolorised  by  heating 
in  open  pans  with  1  to  10  per  cent,  of  zinc  dust  at  100°,  the  zinc  soap  being  finally  decomposed  by  hot  dilute 
hydrochloric  acid.  W.  H.  Burton  (U.S.  Pat.  772,129,  1904)  uses  a  process  similar  to  that  of  Fournier  (see  above), 
benzine  or  naphtha  being  employed  as  solvent  and  the  sulphonic  ethers  being  decomposed  in  solution  by  the 
direct  action  of  steam. 

The  general  reaction  of  Sabatier  and  Senderens  (see  pp.  34  and  59)  has  also  been  applied  practically  (Ger.  Pat. 
141,029,  1902),  a  current  of  hydrogen  being  passed  into  the  hot  mixture  of  oleic  acid  and  catalytic  powdered 
nickel  (reduced  nickel)  (see  also  E.  Erdmann,  Ger.  Pat.  211,669,  1907)  ;  if  the  oleic  acid  is  pure,  it  is  transformed 
almost  completely  into  stearic  acid.  A  similar  reduction,  but  with  a  lower  yield,  is  obtained  with  the  electric 
discharge  (Ger.  Pat.  167,107,  1904).  A.  Knorre  (Ger.  Pat.  172,690,  1903)  treats  an  emulsion  of  oleie  acid  and 
formaldehyde  with  zinc  dust. 


410 

the  oil.  But  better  results  are  now  obtained  by  using  aqueous  emulsions  rich  in  enzymes 
(extract  of  castor  oil  seeds),  but  much  poorer  in  proteins  (which  are  harmful)  and  con- 
taining 60  per  cent,  of  water,  37  per  cent,  of  castor  oil,  and  3  per  cent,  of  proteins.  When 
the  seeds  are  used,  a  milky  emulsion  is  obtained  by  crushing  the  seeds  in  presence  of  the 
necessary  amount  of  water  (50  to  60  per  cent.)  and  is  decanted  off  roughly  from  the  skins 
and  treated  with  0-06  per  cent,  of  acetic  acid  (calculated  on  the  weight  of  fat  to  be  decom- 
posed subsequently).  Of  the  seeds  or  the  enriched  extract,  50  to  89  kilos  are  used  per 
1000  kilos  of  fat  (the  maximum  for  fats  with  the  higher  saponification  number  ;  although 
tallow  requires  the  maximum  amount  and  a  temperature  of  40°).  To  accelerate  the 
decomposition,  0-15  to  0-20  per  cent,  (on  the  weight  of  fat)  of  manganese  sulphate  (acti- 
vator) dissolved  in  a  little  hot  water  is  added,  and  if  the  fat  contains  much  protein  or 
gummy  matter,  it  is  well  to  clarify  it  by  heating  with  1  per  cent,  of  sulphuric  acid  diluted 
with  a  little  water  ;  the  last  traces  of  this  acid  are  then  removed  by  repeated  and  thorough 
washing  with  water,  as  they  would  be  deleterious  to  the  reaction.  With  liquid  fats,  the 
decomposition  is  carried  out  at  23°  and  with  solid  ones  at  1°  to  2°  above  the  melting- 
point,  provided  however  that  this  does  not  exceed  42°,  since  at  44°  the  enzymes  no  longer 
act  in  the  desired  direction  ;  if  necessary,  fats  with  high  melting-points  are  mixed  with 
liquid  oils. 

The  practical  working  of  the  process  is  as  follows  :  A  leaden  coil  for  indirect  steam 
and  a  tube  for  the  injection  of  air  reach  almost  to  the  bottom  of  a  lead-lined  iron  boiler 
with  a  conical  base  ;  discharge  cocks  are  fitted  to  the  boiler  at  the  bottom  and  at  various 
heights.  The  fat  and  about  35  per  cent,  of  water  are  heated  to  the  desired  temperature 
(see  above),  being  kept  stirred  by  means  of  a  current  of  air.  The  castor-seed  extract, 
mixed  with  0-2  per  cent,  of  manganese  sulphate  and  0-06  per  cent,  of  acetic  acid  (on  the 
weight  of  fat ;  the  reaction  starts  and  proceeds  well  if  the  mass  is  faintly  acid  at  first) 
is  then  added,  the  whole  being  mixed  for  about  15  minutes  so  as  to  give  a  homogeneous 
emulsion.  The  vessel  is  then  tightly  covered  so  that  the  temperature  may  be  maintained, 
the  mass  being  mixed  from  time  to  time  to  keep  it  emulsified.  After  24  to  36  hours, 
when  more  than  90  per  cent,  of  the  fat  is  decomposed,  the  mass  is  mixed  and  heated  to 
80°  to  85°,  0-2  to  0-3  per  cent,  (of  the  weight  of  fat)  of  concentrated  sulphuric  acid  (66°  Be.) 
diluted  with  one-half  its  weight  of  water  being  then  added.  The  whitish  emulsion  soon 
becomes  dark  owing  to  the  separation  of  the  fused  fatty  acids  and  when  this  occurs  the 
heating  and  stirring  are  suspended  and  the  mass  left  overnight.  The  various  taps  are 
then  set  in  operation  to  separate  the  bottom  layer  of  fairly  concentrated  glycerine,  the 
intermediate  emulsified  layer  (3  to  4  per  cent,  of  the  fatty  acids,  used  for  soap- making) 
and  the  clear  fused  fatty  acids  which  are  boiled  with  water  to  free  them  from  sulphuric 
acid.  Originally,  when  the  seeds  were  used  instead  of  the  extract,  the  resulting  glycerine 
was  very  dark,  and  it  was  necessary  to  decolorise  it  with  bone-black  (nowadays  it  is 
as  good  as  that  given  by  saponification  with  lime),  while  the  intermediate  emulsified  layer 
formed  as  much  as  22  per  cent,  of  the  total  fatty  acids  (now  only  2  to  4  per  cent.).  The 
aqueous  glycerine  (sweet  water)  of  the  enzymic  process  is  first  concentrated  to  10°  Be.  in 
open  pans,  the  sulphuric  acid  being  separated  by  means  of  barium  carbonate  in  the  hot. 
The  barium  sulphate  is  removed  by  filter-pressing  and  the  filtered  liquid  further  con- 
centrated in  a  multiple-effect  vacuum  apparatus  to  28°  Be.,  a  clear,  brownish  glycerine 
containing  only  0-2  to  0-4  per  cent,  of  ash  being  thus  obtained. 

The  biological  process  has  spread  rapidly  during  recent  years,  since  the  whole  of  the 
glycerine  is  readily  recovered,  while  the  fatty  acids  obtained  are  of  far  better  quality  than 
those  prepared  by  decomposing  the  fat  in  autoclaves  by  means  of  lime,  &c.  The  fatty 
acids  from  sulphocarbon  olive  oil  retain,  however,  their  characteristic  green  colour,  and 
those  from  palm  oil  their  orange  colour.  The  fatty  acids  yielded  by  this  process  contain 
neither  hydroxy-acids,  as  do  those  obtained  under  pressure,  nor  calcium  soaps,  and  are 
hence  more  suitable  for  the  manufacture  of  either  candles  or  soap  (see  later,  Soap). 

(5)  Twitchell's  Catalytic  Process.  The  decomposition  is  here  analogous  to  that  with 
sulphuric  acid  (which  also,  strictly  speaking,  is  catalytic),  but  with  TwitchelVs  reagent 
(benzenestearosulphonic  acid)  it  takes  place  far  more  readily  probably  because  this  reagent 
dissolves  in  the  fat  more  easily  than  does  sulphuric  acid.  The  fats  are  first  purified  by 
heating  to  90°  to  100°  in  a  lead-lined  covered  vat  (Fig.  274)  with  1-5  to  2  per  cent,  of 
sulphuric  acid  at  60°  Be.,  direct  steam  being  passed  in  so  that  when  the  acid  is  discharged 
after  standing  overnight  it  has  a  specific  gravity  of  8°  Be.  (for  cotton-seed  or  linseed  oil, 


TWIT  C  HELL'S    PROCESS 


411 


15°  Be.).  The  purified  fat  is  passed  into  another  wooden  vat,  B,  provided  with  a  wooden 
cover,  one  half  of  which  is  removable  ;  it  is  here  mixed  with  20  per  cent,  of  distilled  or 
condensed  water  (from  the  tank  G),  the  mixture  being  then  boiled  by  direct  steam  and 
0-5  to  0-15  per  cent,  of  the  Twitchell  reagent  added  (the  minimum  with  pure  fats  and 
the  maximum  with  highly  impure  third-grade  fats).  The  current  of  steam  is  continued 
so  that  a  homogeneous  emulsion  is  rapidly  obtained,  and  after  being  heated  in  this  way 
for  24  hours  about  90  per  cent,  of  the  fatty  acids  are  liberated  and  the  glycerine  separated. 
Xo  more  steam  is  then  passed  through  the  mass,  but  a  slow  jet  is  kept  flowing  into  the 
space  between  the  surface  of  the  liquid  and  the  cover  to  prevent  the  fatty  acids  from 
turning  brown  during  the  subsequent  operations  owing  to  contact  with  the  air.  In  about 
an  hour's  time,  the  emulsion  breaks  up  and  the  fatty  acids  float  on  the  aqueous  glycerine  ; 
if  the  emulsion  should  not  disappear,  it  is  mixed  gently  for  a  few  moments  with  0-1  to 
0-2  per  cent,  of  sulphuric  acid  of  60°  Be.  and  then  left.  The  sweet  water  usually  has  a 
specific  gravity  of  5°  Be.  (15  per  cent.)  and  forms  50  per  cent,  of  the  weight  of  the  fat, 
and  if  this  is  not  the  case,  the  quantity  of  distilled  water  added  initially  and  the 
dryness  of  the  steam  employed  are  varied  when  further  quantities  of  fat  are  treated. 
The  sweet  water  is  neutralised  with  lime  and  concentrated  (see  p.  185).  For  soap-making 
the  fatty  acids  may  be  used 
as  they  are,  but  as  a  rule 
the  saponification  is  com- 
pleted by  adding  10  percent, 
of  pure  water  and  heating  for 
12  to  24  hours  with  direct 
steam,  any  small  amount  of 
emulsion  formed  at  the 
surface  of  the  liquid  by 
the  steam  being  destroyed 
by  the  addition  of  a  little 
sulphuric  acid.  In  this  way, 
97  to  98  per  cent,  of  the 
theoretical  amount  of  fatty  acids  is  obtained.  Barium  carbonate  (1  part  per  10  parts  of 
Twitchell's  reagent  used,  or  more  if  sulphuric  acid  were  added  to  destroy  emulsion), 
mixed  with  a  little  water,  is  now  added,  and  the  whole  heated  for  15  to  20  minutes  ;  if 
the  lower  layer  of  water  now  has  an  acid  reaction  towards  methyl  orange,  more  barium  car- 
bonate must  be  added.  The  current  of  steam,  both  in  and  above  the  liquid,  is  now  stopped, 
since  after  this  the  fatty  acids  are  no  longer  turned  brown  by  the  air.  The  sweet  water 
drawn  off  after  clarification  is  very  dilute  and  is  used  in  place  of  water  in  the  treatment 
of  further  quantities  of  fat.  After  crystallising  and  pressing  to  separate  the  solid  from 
the  liquid  acids  (see  above),  the  fatty  acids  are  now  ready  for  converting  into  soap  and 
candles.  In  general  they  are  less  coloured  as  the  amount  of  Twitchell's  reagent  used  and 
the  duration  of  its  action  are  diminished.  Good  results  are  not  obtained  until  after  five 
or  six  operations,  by  which  time  the  surface  of  the  wooden  vessels  ceases  to  be  attacked. 

Just  as  with  the  preceding  process,  the  use  of  the  Twitchell  process  has  spread  con- 
siderably in  America  and  in  Europe.1  The  Twitchell  reagent  (which  costs  about  1*.  2d. 
per  kilo)  and  estimates  for  the  plant  may  be  obtained  directly  from  Messrs.  Joslin, 
Schmidt  &  Co.,  3223  Spring  Grove  Avenue,  Cincinnati,  Ohio,  or  from  their  representatives 
in  various  countries. 

1  The  plant  for  a  factory  using  the  biological  or  catalytic  process  is  considerably  less  expensive  than  for  one 
employing  autoclaves,  while  there  is  also  a  decided  economy  in  the  working  expenses,  as  is  shown  by  the  follo.wing 
approximate  figures,  which  show  that  these  processes  are  of  value,  at  any  rate  in  countries  where  coal  is  dear. 
These  data  are  from  a  large  factory  using  the  Twitchell  process  and  treating  about  70,000  kilos  of  fat  per  day — 
10.000  kilos  at  a  time  in  each  apparatus.  The  prices  given  are  those  current  in  Italy,  and  the  cost  is  calculated 
for  100  kilos  of  fat  treated  ;  the  figures  in  brackets  give  the  corresponding  cost  for  the  autoclave  method  :  coal 
at  40  lire  (32s.)  per  ton,  0-20  lira  (0-82  lira) ;  sulphuric  acid,  0-09  lira  (0-37) ;  baryta  or  lime,  0-06  lira  (0-11)  ; 
labour,  0-03  lira  (0-04) ;  depreciation  and  repairs,  0-02  lira  (0-26) ;  Twitchell  reagent,  0-80  lira.  Hence  the  total 
cost  of  treating  100  kilos  of  fat  will  be  at  most  1-20  lira  (lljrf.)  with  the  Twitchell  process  and  at  least  1-60  lira 
(15-4rf.)  with  the  ordinary  autoclave  process.  In  the  case  of  small  plants,  the  cost  of  working  increases  some- 
what with  the  Twitchell  process,  but  there  is  always  an  advantage  owing  to  the  less  initial  outlay  required. 


FIG.  274. 


412  ORGANIC    CHEMISTRY 

MANUFACTURE  OF  CANDLES  x 

The  prime  materials  for  the  manufacture  of  candles  are  the  combustible  fatty  matter 
and  the  wick. 

A  good  candle  should  give  a  white  light,  should  burn  slowly,  should  not  "gutter  " 
or  diffuse  an  unpleasant  smell,  should  not  be  greasy  to  the  touch,  should  be  white  and 
give  a  smokeless  flame,  and  should  not  splutter,  while  the  relation  between  the  size  of 
the  wick  and  that  of  the  candle  must  be  properly  chosen. 

The  object  of  the  wick  is  to  feed  the  flame  regularly  with  the  melted  material.  It  is 
usually  made  of  filaments  (15  to  20)  of  pure  cotton  or  linen  without  knots.  Animal  fibres 
should  be  rejected,  as  they  give  an  unpleasant  smell  and  a  fused  carbonaceous  mass  which 
diminishes  the  luminosity.  Wicks  formed  of  filaments  which  are  only  twisted  require 
frequent  snuffing,  since  they  do  not  bend  on  themselves  and  do  not  burn  completely, 
whilst,  if  they  are  plaited  or  woven  and  twisted,  as  Cambac^res  proposed,  this  incon- 
venience is  overcome.  For  stearine  candles  obtained  by  fusion,  the  wick  is  of  twisted 
cotton  braid,  while  for  more  readily  fusible  materials  (wax,  tallow,  &c.),  more  or  less 
twisted  wicks  are  used  according  as  the  candles  are  made  by  fusion  or  by  compression. 
Nowadays  wicks  are  made  with  suitable  machines  like  those  used  for  knitting,  the^e 
effecting  also  the  twisting  of  the  filaments. 

Wicks  which  have  not  been  pickled  do  not  act  well  for  candles,  as  they  leave  a 
carbonaceous  residue  which  diminishes  their  capillary  property. 

In  1830,  Milly  found  that  the  combustion  of  the  wick  is  facilitated  by  steeping  it  in 
a  solution  of  boric  or  phosphoric  acid,  such  treatment  being,  however,  only  of  advantage 
with  braided  wicks. 

Many  other  substances  have  since  been  proposed  for  this  purpose.  Thus,  in  France 
the  wicks  are  immersed  for  3  hours  in  a  solution  of  1  kilo  of  boric  acid  in  50  litres  of  water, 
and  are  then  pressed,  centrifuged,  and  dried  ;  in  some  cases  a  trace  of  sulphuric  acid  is 
added  to  the  bath.  In  Russia,  the  wick  is  left  in  a  solution  of  sulphuric  acid  (50  grms. 
per  litre),  squeezed,  dried  in  hot  air,  steeped  in  a  bath  containing  4-5  grms.  of  boric  acid 
and  18  grms.  of  ammonium  sulphate  per  litre  of  water,  and  then  dried.  Another  solution 
giving  good  results  is  composed  of  60  grms.  of  borax  +  30  grms.  KC1  +  30  grms.  KN03, 
+  30  grms.  NH3  +  3-5  litres  of  water.  The  borax  renders  the  flame  white. 

In  general  these  products  either  induce  a  more  ready  oxidation  (chlorates,  nitrates) 
or  melt  the  ash  of  the  wick,  which  thus  gradually  falls  by  its  own  weight.  In  some  cases 
the  penetration  of  the  solution  into  the  wick  is  hastened  by  the  addition  of  a  little 
alcohol. 

If  the  candle  is  too  large  in  comparison  with  the  wick,  the  excess  of  stearine  melts  and 
forms  a  kind  of  cup  with  tall  sides  full  of  the  fused  stearine,  which  cannot  be  completely 
absorbed  by  the  wick  and  so  makes  the  flame  smaller  ;  then,  when  the  edges  fall,  the 
stearine  overflows  and  produces  guttering.  If,  on  the  other  hand,  the  wick  is  too  large, 
an  insufficient  quantity  of  wax  is  melted  and  no  cup  is  formed  to  contain  it,  the  candle 
guttering  continually  from  the  sides  and  the  flame  being  less  luminous. 

1  The  ancient  Romans  used  for  illuminating  purposes  a  kind  of  torch  steeped  in  wax  or  bitumen.  Only  after 
the  second  century  of  the  Christian  era  was  a  distinction  drawn  between  wax  candles  and  those  of  tallow  ;  the 
use  of  the  latter  was  regarded  as  a  luxury,  while  wax  candles  were  employed  in  churches.  The  Catholic  religion 
used  them  exclusively  for  religious  functions,  and  thus  caused  a  great  increase  in  the  consumption,  which 
diminished  only  after  the  spread  of  the  Reformation.  Very  soon,  however,  the  consumption  of  wax  candles  again 
increased  very  considerably  owing  to  their  extended  use  at  the  courts  of  kings  and  princes.  Meanwhile  the 
employment  of  tallow  candles  for  domestic  purposes  was  continually  spreading,  and  in  the  eighteenth  century 
several  important  factories  were  working  in  England ;  but  the  candles  produced  were  high  in  price  and  burned 
very  quickly.  Only  after  ChevreuTs  work  on  the  nature  of  fats  in  the  early  part  of  last  century  (after  1815)  led 
to  improvements  in  the  saponiflcation  and  to  the  preparation  of  solid  fatty  acids  was  the  rational  manufacture 
of  candles  initiated.  Chevreul  himself,  together  with  Gay-Lussac,  patented  in  1825  a  process  for  preparing 
candles  from  stearic  acid ;  but  the  resulting  industrial  undertakings  were  soon  abandoned,  owing  to  the  diffi- 
culties encountered  in  the  saponiflcation  and  in  the  preparation  of  the  wick.  It  was  only  when  Cambaceres,  in 
1830,  devised  plaited  and  twisted  wicks,  and  when  Milly,  in  1834,  kitroduced  saponification  with  lime  and  the 
subsequent  decomposition  of  the  calcium  soap  with  sulphuric  acid,  that  the  manufacture  was  placed  on  a  stable 
and  remunerative  basis.  Milly's  first  factory  for  stearine  candles  was  erected  in  Austria  in  1837,  and  in  1840 
one  was  started  in  Berlin  and  another  in  Paris.  Important  improvements  were  made  in  1842  by  saponifying 
the  fats  with  sulphuric  acid,  and  in  1854  by  saponifying  the  fats  and  distilling  the  fatty  acids  with  superheated 
water  or  steam  (processes  of  Tilghmann,  Berthelot,  and  Melsen).  Almost  immediately  after  this,  however,  the 
manufacture  of  paraffin  candles  was  started,  paraffin  having  been  obtained  in  large  quantities  by  Young  (1850) 
by  the  dry  distillation  of  bituminous  coal  (boghead,  &c.),  peat,  shale,  lignite,  &c. ;  this  industry  underwent 
further  extension  after  paraffin  had  been  extracted  from  petroleum  and  ozokerite  (see  p.  80). 


MANUFACTURE    OF    CANDLES 


413 


In  1904  a  patent  was  filed  for  the  manufacture  of  artificial  silk  candle-wicks,  which 
seem  to  give  good  results. 

Formation  of  the  Candles.  The  white  blocks  of  stearic  and  palmitic  acids  from  the 
presses  are  scraped  at  the  surface  and  edges  to  remove  adherent  impurities.  The  purer 
residue  is  melted  and  shaken  in  a  leaden  vessel  with  sulphuric  acid  (3°  Be.)  to  dissolve 
and  separate  the  impurities  (iron,  hairs  from  the  press  bags,  &c.)  ;  the  sulphuric  acid  is 
then  decanted  off  and  the  stearine  washed  repeatedly  with  boiling  water  to  remove  all 
trace  of  the  mineral  acid.  In  some  cases  the  fused  fatty  acids  are  shaken  with  a  little 
albumin,  being  then  allowed  to  stand  so  that  the  coagulated  albumin  and  the  impurities 
may  settle.  In  cooling,  the  stearine  tends  to  crystallise,  the  resultant 
candles  being  then  less  homogenous  and  more  brittle,  At  first  arsenious  ami 

acid  was  used  to  prevent  crystallisation,  but,  now  that  this  is  prohibited,          mm 
the  stearine  is  kept  continually  shaken  until  it  almost  solidifies  when  it  is 
introduced  into  the  moulds,  and  the  candles  then  rapidly  solidified.     It  is 
often  more  convenient  to  add  a  little  white  wax  or  paraffin  (2  to  10  per 
cent.),  which  also  prevents  crystallisation  of  the  stearine. 

The  quality  and  purity  of  the  stearine  are  ascertained  by  the  usual  tests, 
the  neutral  fat  being  determined  by  Geitel's  test  (see  p.  379),  the  paraffin, 
cerasin,  cholesterol,  and  carnauba  wax  by  the  saponification  number  and 
by  the  non-saponifiable  matter  (see  p.  379),  and  the  amount  of  oleic  acid 
by  the  melting-point  (which  is  56°  to  56 -5°  for  pure  stearine  pressed  once 
and  57-5°  to  58°  for  doubly  pressed  stearine)  and  the  solidification  point, 
making  use  of  de  Schepper  and  Geitel's  Table1  obtained  by  mixing  saponi- 
fication stearine,  solidifying  at  48°,  with  oleine  having  a  solidifying  point 
of '5-4°. 

Candles  are  made  in  three  different  ways:    (1)  by  immersion;   (2)  by     pIG>  275. 
fusion  ;  and  (3)  by  pressure. 

The  first  of  these  methods  is  the  oldest  and  is  now  almost  entirely  abandoned.  It 
was  employed  originally  for  tallow  candles,  and  is  now  sometimes  used  to  mask  the  presence 
of  inferior  fat  or  stearine,  the  wicks  suspended  from  frames  being  first  immersed  in  the 
impure  fused  fat,  while  the  outer  layers  are  obtained  by  dipping  into  a  purer  fat  or  fatty 
acid. 

In  China  considerable  use  is  still  made  of  tallow  candles  of  peculiar  shape  with  a  hole 
in  the  middle. 

Certain  long  tapers  are  obtained  by  pressure,  the  semi-fused  wax  or  stearine  and  the 
wick  being  forced  through  a  tube. 

But  almost  all  candles  are  now  made  by  fusion  in  highly  perfected  machines,  which 
admit  of  a  maximum  output  being  rapidly  obtained  with  a  minimum  of  labour.  The 
moulds,  which  are  very  smooth  inside,  have  the  shape  of  the  candles — with  the  pointed 
end  below  and  the  enlarged  base  at  the  top  (Fig.  275) — and  are  imperceptibly  conical ; 
they  are  made  of  an  alloy  composed  of  3  parts  of  tin  and  1  part  of  lead.  For  the  fusion  of 
a  large  number  of  candles  at  a  time  (100  or  more)  a  machine  is  used  similar  to  that  shown 
in  Fig.  276.  The  moulds  of  all  the  candles  pass  through  the  closed  metallic  box,  E  D, 
to  the  bottom  and  cover  of  which  they  are  screwed.  Tepid  or  cold  water  can  be  passed 

1  De  Schepper  and  Geitel's  Table  of  the  solidifying  points  of  mixtures  of  fatty  acids  : 


Tempera- 

Per cent. 

Tempera- 

Per cent. 

Tempera- 

Per cent. 

Tempera- 

Per cent. 

ture  of 

of 

ture  of 

of 

ture  of 

of 

ture  of 

of 

solidification 

stearine 

solidification 

stearine 

solidification 

stearine 

solidification 

stearine 

5-4° 

0 

16° 

7-7 

27° 

21-7 

38° 

50-5 

6° 

0-3 

17° 

8-8 

28° 

23-3 

39° 

54-5 

7° 

0-8 

18° 

9-8 

29° 

25-2 

40° 

58-9 

8° 

1-2 

19° 

11-1 

30° 

27-2 

41° 

63-6 

9° 

1-7 

20° 

12-1 

31° 

29-2 

42° 

68-5 

10° 

2-5 

21° 

13-2 

32° 

31-5 

43° 

73-5 

11° 

3-2 

22° 

14-5 

33° 

33-8 

44° 

78-9 

12° 

3-8 

23° 

15-7 

34° 

36-6 

45° 

83-5 

13° 

4-7 

24° 

17 

35° 

39-5 

46° 

89-0 

14° 

5-6 

25° 

18-5 

36° 

43-0 

47° 

94-1 

15° 

6-6 

26° 

20-0 

37° 

46-9 

48° 

100-0 

414 


ORGANIC    CHEMISTRY 


at  will  through  the  box  at  /  or  H,  so  as  to  surround  the  moulds.  The  lower  part  of  each 
mould  contains  a  kind  of  small  piston  which  has  exactly  the  shape  of  the  point  of  the 
candle  and  can  be  made  to  traverse  the  whole  length  of  the  mould,  being  joined  to  an 

iron  tube,  B,  fixed  to  a 
frame  capable  of  being 
raised  and  lowered  by  the 
rack  and  pinion,  C.  All 
the  pistons  can  be  raised  at 
once  so  as  to  force  all  the 
solidified  candles  from  the 
moulds.  In  order  that  the 
wick  may  be  always  in 
the  middle  of  the  candle, 
it  is  wound  on  bobbins,  A, 
and  passes  through  the  iron 
tube  which  raises  the  piston 
to  the  upper  part  of  the 
mould.  The  semi -fused, 
opalescent  stearine,  which  is 
poured  into  the  moulds 
kept  by  means  of  warm 
water  (45°  to  60°)  at  a 
temperature  slightly  above 
the  melting-point,  is  then 
cooled  by  passing  cqld 
water  round  the  moulds. 
When  solidification  is  com- 
plete, the  enlarged  bases 
at  the  top  of  the  candles 
FIG.  276.  are  cut  off  by  a  knife  and 

the  candles  forced  out  and 

grasped  by  the  rods,  L.  In  rising,  the  candles  unwind  from  the  bobbins  new  wicks  which 
are  thus  brought  into  the  middle  of  the  moulds  ready  for  the  next  operation.  When  the 
second  batch  of  candles  is  solidified  in  the  moulds,  the  wicks  of  the  first  batch  are  cut 
so  as  to  make  way  for  the  others  to  be  removed  from  the  moulds.  When  shorter  candles 
are  required,  the  pistons 
are  raised  in  the  moulds 
to  the  desired  height 
and  the  stearine  then 
run  in.  The  candles  thus 
obtained  are  bleached 
by  arranging  them  ver- 
tically on  trucks  in 
metal  gauze  frames  and 
leaving  them  for  some 
days  in  the  open  air 
exposed  to  the  action 
of  the  air,  sunlight, 
and  dew. 

After  this,  the 
candles  are  washed, 
polished,  and  sawn  off 

to  a  uniform  length  in  a  machine  of  the  Binet  type  (Fig.  277).  The  candles  are  first 
dipped  in  a  bath,  V,  containing  soapy  water  or  a  dilute  solution  of  soda,  and  are  then 
placed  in  the  grooves  of  the  wheel,  M,  the  head  being  against  the  left-hand  edge,  while  the 
bases  are  cut  off  by  a  small  circular  saw,  TO  ;  the  fragments  drop  on  to  the  frame,  X,  and 
so  into  the  box  beneath.  The  candles  fall  into  the  grooves  of  the  travelling  endless  plane, 
TM',  and  are  rubbed  and  polished  by  a  brush,  B,  moved  excentrically  from  V  ;  when 
they  reach  M'  they  fall  into  the  trough,  E.  The  finished  candles  are  stamped  auto- 


FIG.  277. 


SOAP  415 

matically  with  the  trade  mark  and  are  then  tied  and  wrapped  up  in  packets  of  12  or  24 
(or  I  or  1  kilo)  and  placed  in  wooden  boxes  for  transport. 

Some  factories  make  lighter,  perforated  candles  and  some  coloured  candles  or  mixed 
candles  containing  wax  or  paraffin.  To  remove  the  semitransparency  of  paraffin  candles 
and  so  make  them  resemble  those  of  stearine,  about  5  per  cent,  of  stearine  and  5  per  cent, 
of  paraffin  oil  are  added.  The  same  effect  may  be  obtained  with  a  small  quantity  of 
/7-naphthol  (Ger.  Pat.  165,503)  or  any  other  substance  which  dissolves  the  paraffin  in  the 
hot  and  deposits  it  in  the  cold  in  a  finely  divided  state  (e.g.  solid  fatty  acids,  amides, 
phenols,  ketones,  &c.). 

STATISTICS.  The  value  of  the  stearine  candles  exported  from  England  was  £346,400 
in  1892,  £400,000  in  1900,  £495,860  in  1909,  and  £485,220  in  1910,  the  output  in  1907 
being  10,000  tons,  of  the  value  of  £1,640,000.  France  exported  25, 120  quintals  of  stearine 
candles,  worth  £196,000,  in  1890,  and  43,300  quintals,  of  the  value  of  £180,000,  in  1900.  In 
1909  Germany  imported  2200  quintals  of  candles  and  exported  7880.  The  United  States 
exported  1500  tons  (£58,200)  in  1910  and  1450  tons  (£55,600)  in  1911. 

In  1903  there  were  about  250  factories  in  Italy  for  candle-making  only,  the  total 
horse-power  of  the  engines  being  185  and  the  number  of  operatives  1430  ;  there  were, 
in  addition,  188  factories  for  both  candles  and  soap,  employing  2700  workpeople  and 
using  830  h.p.  In  1876  there  were  but  10  factories  with  550  operatives. 

In  1875-1879  Italy  imported  on  an  average  6350  quintals  of  candles  per  annum  and 
exported  650  quintals,  whilst  in  1900-1904  the  imports  averaged  551  and  the  exports 
1420  quintals  annually.  In  1905  the  imports  were  869  quintals,  worth  £4172,  and  the 
exports  614  quintals,  of  the  value  of  £2948  ;  in  1910  the  exports  fell  to  582  (£2920)  and 
the  imports  to  380  quintals  (£1900). 

MANUFACTURE  OF  SOAP1 

Theoretically  soaps  include  all  metallic  salts  of  the  higher  fatty  acids, 
but  practically  the  name  is  given  only  to  salts  of  oleic,  stearic,  and  palmitic 
acids,  and,  in  general,  of  the  fatty  acids  contained  in  natural  oils  and  fats. 
Importance  attaches  mainly  to  the  sodium  soaps  and,  to  a  less  extent,  to  those 
of  potassium  and  ammonium.  It  was  at  one  time  thought  that  soaps  were 
composed  largely  of  margaric  acid,  but  it  has  been  shown  that  this  acid  does 
not  occur  in  natural  fats,  the  confusion  arising  from  the  fact  that  a  mixture 
of  palmitic  and  stearic  acids  was  obtained  with  a  melting-point  identical 
with  that  of  synthetic  margaric  acid  (see  p.  290). 

Almost  in  its  entirety  soap  is  used  for  washing  and  for  cleansing    and  • 
removing  grease  from  textile  fibres,  sweaty  garments,  and  the  greasy,  dirty 

1  History  of  Soap.  Soap  was  not  known  to  the  ancient  Hebrews  and  Phoenicians  or  to  the  Greeks  of  the  time 
of  Homer,  who  washed  their  garments  with  the  ashes  of  plants  and  water,  and  by  mechanical  rubbing.  Some 
races  used  the  juices  of  certain  plants,  and  later  it  was  discovered  that  when  ashes  were  heated  with  lime  they 
gave  rise  to  natron,  which  was  much  more  effective  than  the  ashes  themselves.  Yet  the  writers  of  the  Bible, 
who  are  certainly  not  conscientious  and  exact  historians,  several  times  mention  soap  and  quote  the  following 
supposed  phrase  of  the  prophet  Jeremiah  (who  would  have  lived  several  centuries  before  the  Christian  era) : 
"  Though  thou  wash  thee  with  nitre  [natron]  and  take  thee  much  soap,  yet  thine  iniquity  is  marked  before  me." 
Seneca  and  Pliny  mention  soap  in  their  writings  and  attribute  its  discovery  to  the  Gauls,  who  prepared  it  from 
the  ashes  of  plants  and  goats'  fat  and  used  it  as  a  hair-wash  and  for  medicinal  purposes  (lead  plaster).  It  is  said 
that  Galen  (second  century  of  the  Christian  era)  proposed  the  use  of  soap  for  washing.  In  the  excavations  of 
Pompeii  has  been  found  a  complete  soap  factory  with  utensils  and  saponified  material.  Marseilles  did  a  large 
trade  in  soap  as  early  as  the  ninth  century,  but  in  the  eleventh  century  it  had  a  serious  rival  for  the  premier  position 
in  Savona.  In  the  fifteenth  century  the  industry  flourished  at  Venice,  and  in  the  seventeenth  at  Genoa,  which, 
together  with  Savona,  Marseilles,  and  Alicante,  enjoyed  a  monopoly  in  soap-making.  In  England  the  industry 
began  to  develop  after  1650,  and  in  Germany  it  assumed  considerable  importance  after  Chevreul's  investigations  on 
fats  (1810-1823).  With  the  development  of  the  soda  industry  and  increase  of  the  trade  in  palm  oil  and  coco-nut 
oil,  the  conditions  in  Germany  and,  to  some  extent,  in  other  countries  favoured  extension  of  soap-making.  At 
the  present  time  Marseilles,  although  partly  surpassed  by  the  large  English  factories,  still  preserves  its  early 
fame,  which,  however,  the  Italian  factories  have  lost.  But  several  times  in  the  past  the  renown  of  Marseilles 
has  been  dimmed  owing  to  the  custom,  even  in  the  early  days,  of  adulterating  soap  and  of  loading  certain  qualities 
of  white  soap  with  enormous  quantities  of  water.  This  explains  why.  for  several  generations,  the  public  preferred 
mottled  soaps,  which  could  not  then  be  adulterated.  It  explains  also  the  various  laws  promulgated  in  France 
against  dishonest  soap-makers,  who  in  1790  provoked  a  general  protest  of  all  the  population  and  a  petition  to 
the  deputies  of  the  States  General  from  all  the  laundresses  of  Marseilles  to  protest  "  against  the  adulteration  of 
white  soap  and  against  the,  malefactors  who  adulterate  it  to  increase  its  weight."  It  does  not  appear  that  things  have 
changed  greatly  after  the  lapse  of  120  years,  for,  since  the  introduction  of  palm  oil  and  coco-nut  oil  in  1850,  the 
consumer  has  always  paid  for  a  considerable  amount  of  water  in  place  of  soap. 


416  ORGANIC    CHEMISTRY 

epidermis  of  the  human  body,  but  it  is  sometimes  employed  as  a  subsidiary 
dressing  in  certain  industrial  operations,  e.g.  in  the  dyeing  of  silk  and 
cotton,  &c. 

The  theory  of  the  saponification  of  fats  has  already  been  discussed  on  p.  377,  and  we 
shall  here  consider  the  cleansing  action  of  soaps.  It  is  well  known  that  the  quantity  of 
fat  or  grease  that  a  soap  is  able  to  remove  from  a  dirty  garment  is  greater  by  far  than 
corresponds  with  the  amount  of  alkali  liberated  on  dissolving  the  soap  in  water. 

Being  formed  from  weak  acids,  soap  in  dilute  aqueous  solution  is  undoubtedly  partly 
dissociated  into  caustic  alkali  and  either  acid  soaps  in  the  cold  or  fatty  acids  in  the  hot. 
This  can  readily  be  shown  by  the  opalescence  of  the  dilute  aqueous  solutions  and  by  the 
violet  colour  imparted  to  phenolphthalein  by  a  perfectly  neutral  (i.e.  not  yet  dissociated) 
alcoholic  solution  or  highly  concentrated  aqueous  solution  of  soap,  after  pouring  into  a 
large  quantity  of  water.  If,  then,  part  of  the  grease  can  be  rendered  soluble  by  the 
saponifying  action  of  the  alkali  gradually  liberated  from  the  soap,  another  part  is  certainly 
carried  away  mechanically  by  the  emulsifying  action  of  the  soap  itself  and  of  its  fatty 
acids  ;  this  action  is  accompanied  by  the  abundant  production  of  lather,  which,  together 
with  the  water,  incorporates  and  removes  all  the  grease  with  which  it  comes  into  contact. 
It  is  for  this  purpose — the  formation  of  lather  and  emulsification  of  the  grease — that 
rubbing  is  necessary  in  the  washing  of  a  garment  with  soapy  water.  A  mere  solution  of 
caustic  soda,  even  in  excess,  does  not  produce  a  detergent  effect  equal  to  that  of  soap. 

As  regards  the  molecular  condition  of  soap  in  its  concentrated,  non -dissociated  solutions, 
it  appears  demonstrated  that  it  there  exists  in  a  colloidal  condition,  since  an  increase 
in  the  concentration  is  not  accompanied  by  rise  in  the  boiling-point,  which  approximates 
to  that  of  water,  while  the  electrical  conductivity  is  minimal.  But,  according  to  McBain 
and  Taylor  (1910),  in  highly  concentrated  solutions  soap  is  apparently  not  a  colloid,  as 
it  conducts  the  electric  current. 

The  solubility  in  water  of  almost  all  soaps  is  diminished  rapidly  to  the 
point  of  complete  separation  by  the  addition  of  soluble  salts  which  do  not 
decompose  the  soap,  e.g.  NaCl,  KC1,  Na2S04,  NH4C1,  Na2C03,  and  even 
NaOH,  &c.,  this  action  being  due  to  a  change  in  the  density  of  the  solution 
and  in  its  degree  of  dissociation.  This  phenomenon  is  the  basis  of  the  salting- 
out  or  graining  of  soap  during  its  manufacture,  but  it  must  be  noted  that  if 
the  fats  or  fatty  acids  used  in  the  making  of  the  soap  contain  hydroxy -acids, 
these  are  almost  entirely  lost,  as  they  are  not  separated  as  insoluble  soaps 
by  salting  out,  and  mostly  pass  into  the  spent  ley.  Hence  account  is  now 
taken  of  the  proportion  of  fatty  hydroxy -acids  (less  soluble  in  benzine  than 
ordinary  fats  or  fatty  acids)  present  in  fatty  materials. 

Sodium  soaps  are  more  stable  than  those  of  potassium  or  ammonium, 
since  sodium  salts  partly  displace  potassium  or  ammonium  from  their  soaps 
with  formation  of  sodium  soaps. 

Alkali  soaps  are  precipitated  by  the  soluble  salts  of  the  alkaline  earths 
and  heavy  metals  in  the  form  of  insoluble  metallic  soaps.  Strong  acids 
separate  the  weaker  fatty  acids  from  soaps. 

The  alkaline  soaps  are  usually  soluble  in  alcohol  and  insoluble  in  ether, 
benzine,  or  benzene.  Evaporation  of  the  alcoholic  solution  yields  a  trans- 
parent soap. 

Saponification  of  fats  is  accompanied  by  increase  in  weight,  each  molecule 
of  glyceride  that  decomposes  fixing  3  molecules  of  alkali  or  water.  A  fat 
containing  a  mixture  of  glycerides  with  a  mean  molecular  weight  of  880,  in 
reacting  with  120  of  NaOH  (3  mols.  or  about  13-6  NaOH  per  100  of  fat),  gives 
92  of  glycerine  and  908  of  water-free  soap.  So  that  theoretically  100  kilos 
of  fat  can  produce  about  10-5  kilos  of  glycerine  and  102  of  soap  ;  in  practice 
about  1-5  to  2  kilos  of  glycerine  are  lost,  while  140  to  160  kilos  of  soap, 
containing  a  considerable  amount  of  water,  are  obtained.  Potash  soaps 
are  softer  than  those  of  soda,  and  soaps  of  liquid  fatty  acids  softer  than 
those  of  solid  fatty  acids. 


STAGES    OF    SOAP- MAKING 

Soap  may  be  made  either  from  the  fatty  acids  obtained  from  fats  by  the  methods 
described  above,  or  from  the  fats  themselves.  In  the  former  case  the  saponification 
is  carried  out  mainly  by  sodium  carbonate,  and  is  completed  (since  with  the  carbonate 
it  proceeds  only  to  the  extent  of  about  90  per  cent.)  by  caustic  soda.  But  in  the  latter 
case  concentrated  solutions  of  caustic  soda  in  the  hot  are  employed  ;  the  carbonate  is, 
indeed,  unable  to  resolve  glycerides,  and  that  amount  of  it  which  always  occurs  in  the 
caustic  alkali  is  lost  during  the  subsequent  operations  of  salting-out,  &c. 

Mention  has  already  been  made  (see  p.  379)  of  the  process  of  decomposing  fats  in  an 
autoclave  by  means  of  ammonia  and  sodium  chloride,  which  was  studied  by  Leuchs  (1859), 
Witelw  (1876),  Buisine  (1883),  and  Polony  (1882)',  and  improved  by  Garelli,  Barbe,  and 
de  Paoli  (Ger.  Pat.  209,537,  1906).  This  process  leads  directly  to  the  sodium  soap  with 
formation  of  ammonium  chloride,  from  which  the  ammonia  may  be  recovered  in  the 
usual  way,  and,  according  to  the  above  patent,  gradual  decomposition  of  the  ammonia 
by  means  of  steam  results  in  a  considerable  separation  of  the  solid  fatty  acids  from  the 
liquid  ones,  the  ammonia  soaps  of  the  former  being  the  first  to  decompose.  Such  separa- 
tion can  be  effected  also  by  cold  water,  which  dissolves  the  ammonia  soaps  of  the  liquid 
fatty  acids  (oleates)  almost  exclusively. 

In  the  manufacture  of  soaps  from  fats  or  oils,  various  stages  are  to  be  distinguished  : 
(1)  mixing  or  pasting  of  the  fat  with  the  alkaline  lye  ;  (2)  mixing  in  the  hot  to  form  the 
soap  and  separate  it  partially  from  the  excess  of  water  ;  (3)  salting-out  (or  "  graining  " 
or  "  cutting  the  pan  '')  to  render  the  soap  insoluble  and  separate  it  from  the  lye,  which 
thus  collects  under  the  layer  of  soap  ;  (4)  boiling  to  saponify  the  last  traces  of  fat,  to 
eliminate  the  scum  and  the  excess  of  water  still  remaining  in  the  soap  and  to  collect  the 
latter  into  a  perfectly  homogeneous,  curdy  mass  ;  (5)  the  soap  is  often  subjected  to  a 
finishing  process,  that  is,  a  final  treatment  with  dilute  alkali  hydroxide  or  carbonate 
solution,  in  order  to  separate  the  more  thoroughly  the  residual  impurities  (aluminium  or 
iron  soaps)  and  so  avoid  a  partial  mottling,  and  to  give  to  the  soap,  first,  the  quantity 
of  water  necessary  to  the  particular  type,  and,  secondly,  a  still  more  homogeneous  appear- 


ance.1 

A  well-finished  soap  contains  35  to  40  per  cent,  of  water  and  only  0-20  to  0-36  per 
cent,  of  salt  and  free  alkali  together.  When  excess  of  free  caustic  soda  remains  in  the 
soap,  considerable  efflorescence,  due  to  formation  of  sodium  carbonate  by  the  carbon 
dioxide  in  the  air,  occurs  at  the  surface  during  the  subsequent  drying.  In  order  to  avoid 
such  a  serious  inconvenience,  it  is  necessary  to  treat  repeatedly  with  sodium  carbonate 
solutions,  because,  even  if  a  little  of  the  latter  is  left  in  the  soap,  only  a  slight  powder 
forms  at  the  surface  on  drying  and  this  can  be  readily  eliminated.  In  some  cases,  a  small 
proportion  of  a  non-saponifiable  fat  (e.g.  \vool  fat)  or  even  of  a  dense  mineral  oil  is  added 
to  the  soap,  the  caustic  soda  being  thereby  preserved  from  direct  contact  with  the  air. 

At  one  time  the  coppers  used  for  soap -making  were  largely  made  of  masonry,  but 
nowadays  they  are  almost  universally  of  iron  and  are  heated  either  by  fire  or  by  direct 
or  indirect  steam,  as  is  shown  in  Figs.  278,  278A,  279,  279A.  Small  coppers  hold  10  to 
50  hectols.  and  large  ones  100  to  400. 

For  every  100  kilos  of  fat  to  be  saponified,  a  copper-volume  of  500  litres  is  taken. 

In  most  soap-works  the  mixing  is  done  by  wooden  blades  worked  by  hand,  although 
coppers  are  made  fitted  with  stirrers  of  various  forms. 

The  saponification  of  100  kilos  of  fat  or  oil  requires  theoretically  about  136  kilos  of 
NaOH,  but  practically  rather  more  than  this  amount  is  used.  Tallow  soap  is  made  in  the 

1  Finishing  is  best  effected  when  the  soap  contains  a  certain  proportion  of  water,  namely,  10  mols.  of  water 
(40'5  per  cent.)  per  1  mol.  of  sodium  oleate,  or  16  mols.  (48-5  per  cent.)  per  mol.  of  sodium  stearatc.  If  the  soap 
is  more  concentrated  than  this,  it  remains  too  viscous  and  opposes  too  great  a  resistance  to  the  precipitation  of 
the  impurities  and  of  the  drops  of  saline  and  caustic  solutions  ;  but  if,  in  the  finishing,  the  necessary  quantity 
of  water  is  restored  (by  adjusting  the  concentration  of  the  lye),  a  small  part  of  the  soap  dissolves,  the  mass  becomes 
more  liquid  and,  on  standing,  the  impurities  are  able  to  fall  to  the  bottom  the  more  readily.  Soaps  which  are 
too  insoluble  in  the  salt  solution  or  caustic  lye  (colza,  sesame1,  linseed,  poppy -seed,  &c.)  can  be  finished  only  when 
mixed  with  readily  soluble  soaps  (coco-nut,  castor,  &c.).  On  the  other  hand,  it  is  necessary  to  prevent  the  soap 
taking  up  too  much  water,  for,  if  this  happens,  it  pastes  together  and  adheres  to  the  sides  of  the  boiler,  does  not 
transmit  heat  readily  to  the  interior  and  hence  boils  with  difficulty,  is  not  easily  finished  and  becomes  uneven. 
Agitation  of  the  mass  and  the  consequent  inclusion  of  a  considerable  amount  of  air  are  to  be  avoided,  the  finishing 
being  thereby  retarded.  When  the  finishing  is  complete  and  the  mass  has  been  allowed  to  stand,  a  slight  frothy 
layer  is  observed  at  the  surface  and  then  comes  the  thick  layer  of  pure,  homogeneous  soap,  well  separated  from 
the  lye  ;  but  above  this  is  a  small,  irregular,  and  gelatinous  layer  composed  of  more  soluble  soaps  (of  hydroxy- 
acids)  of  calcium,  magnesium,  and  iron,  and  of  certain  other  impurities  insoluble  in  the  lye  (colouring-matters, 
coagulated  proteins,  &c.),  and  it  is  this  aiasu  which  forms  the  refuse. 

11  27 


418 


ORGANIC    CHEMISTRY 


following  manner  :  The  tallow  is  mixed  and  gently  heated  in  the  copper  with  about  one- 
fourth  of  the  necessary  amount  of  caustic  soda  in  the  form  of  a  solution  of  10°  Be.  First 
of  all  an  emulsion  is  formed  and  then  saponification  gradually  proceeds,  the  mass  beginning 
to  become  homogeneous  and  the  volume  increasing  slightly.  When  a  little  is  removed 
on  the  blade,  it  forms  a  jelly  which  does  not  separate  the  lye,  and  the  soap-boiler  judges 


FIG.  278. 


FIG.  278A. 


of  the  fixation  of  the  alkali  by  observing  when  the  caustic  taste  of  the  alkali  disappears. 
Much  of  the  fat  remains  unsaponified,  so  that  a  hot  caustic  soda  solution  of  12°  to  14°  Be. 
is  gradually  added  until  the  stirred,  boiling  mass  thickens,  becomes  clear  and  homogeneous, 
and  falls  from  the  spatula  in  transparent  ribbons.  At  this  stage,  in  order  to  judge  if  the 
alkali  has  been  added  in  the  proper  proportion,  a  little  of  the  soap  is  poured  on  to  a  glass 
plate  ;  if  a  solid  white  edge  first  forms  round  the  drop  of  soap,  while  the  interior  of  the 


FIG.  279. 


FIG.  279A. 


mass  remains  transparent  until  solidification  is  complete,  the  whole  of  the  fat  is  saponified 
and  there  is  no  excess  of  alkali.  But  if  the  edge  immediately  turns  greyish  and  the  mass 
turbid,  non -saponified  fat  is  present  and  alkali  lacking ;  whereas,  if  the  whole  mass  becomes 
covered  with  a  whitish  pellicle  without  previous  formation  of  a  solid  edge,  excess  of  alkali 
is  present,  this  being  corrected  by  adding  a  little  fused  tallow  to  the  mass  in  the  copper. 
Thus  treated,  the  gluey  paste,  which  has  a  slightly  caustic  taste,  is  boiled  more  strong] v 
until  it  loses  sufficient  water  to  form  a  homogeneous  ropy  paste  on  the  mixing -blade, 


"  OLE  INE"    SOAPS  419 

At  this  stage  the  separation  of  the  soap  from  the  liquid  is  induced  by  the  gradual 
addition  of  salt  either  in  the  solid  state  (4  to  8  per  cent,  of  the  weight  of  fat)  or  in  con- 
centrated solution  (20°  to  22°  Be.).  The  first  addition  of  salt  renders  the  mass  more 
fluid,  while  successive  additions  cause  separation  of  the  soap,  which  finally  floats  on  the 
lye,  the  latter  being  drawn  off  after  some  hours  by  means  of  either  a  tap  or  siphon.  When 
hard  water  is  used,  a  little  sodium  carbonate  is  always  added  to  the  salt. 

The  residual  lye  should  have,  not  a  caustic  but  a  brackish  and  somewhat  sweet  taste 
owing  to  the  glycerine  present,  and  its  density  should  be  at  least  7°  to  8°  Be.  (for  soaps 
from  coco-nut,  palm-kernel,  oxidised  oils,  &c.,  16°  to  24°  Be.).  If  too  little  salt  has  been 
added,  the  lye  will  retain  dissolved  soap,  and  the  separation  of  the  latter  will  not  be  sharp, 
since  between  it  and  the  lye  will  be  formed  a  third  layer  consisting  of  an  irregular,  gela- 
tinous mass  which  increases  the  waste  and  diminishes  the  yield.  With  too  much  salt, 
the  soapy  mass  separates  rapidly  and  in  large  clots  which  retain  the  lye.  But  if  the 
operation  has  been  properly  carried  out,  the  soap  adheres  to  the  mixer  in  soft  flocculent 
masses  which,  when  squeezed  between  the  fingers,  are  moderately  stiff,  do  not  exude 
liquid  and  give  a  hard  and  dry,  not  a  sticky,  flake. 

When  treated  repeatedly  with  salt  solution,  some  soaps  lose  part  of  their  combined 
alkali  owing  to  the  readiness  with  which  they  dissociate  ;  in  such  cases  a  little  caustic 
soda  is  added  to  the  salt. 

The  soap  is  then  subjected  to  the  boiling  process  (in  some  cases  this  is  preceded  by  a 
further  heating  with  weak  alkali  of  4°  to  6°  Be.  and  a  little  salt,  the  subnatant  lye  being 
decanted  after  a  time).  This  consists  in  covering  the  copper,  boiling  vigorously,  and,  if 
necessary,  stirring  to  prevent  the  frothing  mass  from  overflowing.  By  this  means  the 
small  quantity  of  residual  lye  is  concentrated  and  hence  separates  more  easily,  while  the 
soap  gradually  becomes  denser  owing  to  the  loss  of  nearly  the  whole  of  the  water  (only 
15  to  35  per  cent,  being  left).  The  bubbles  at  the  surface  gradually  increase  in  size  and 
then  disappear  completely,  while  large  bubbles  of  steam  form  at  the  bottom  of  the  copper, 
force  their  way  noisily  through  the  mass  and  produce  large  puffs  at  the  surface.  The 
heat  (fire  or  steam)  is  then  very  soon  stopped.  A  little  of  the  soap  pressed  between  the 
thumb  and  the  palm  of  the  hand  then  forms  a  dry,  soft,  waxy  paste,  but  does  not  stick. 

The  soap  could  next  be  moulded,  but  it  is  often  subjected  to  a  finishing  process  (see 
above),  dilute  caustic  soda  (3°  to  6°  Be.,  or  hot  water  alone  if  the  soap  has  been  treated 
originally  with  excess  of  alkali,  or  very  dilute  sodium  carbonate)  being  gradually  added 
to  the  soap  in  the  boiler,  the  mass  being  heated  and  gently  stirred  until  it  becomes  more 
liquid,  less  granular  and  perfectly  uniform.  The  copper  is  next  covered  and  left  for  a 
day,  the  soap  being  then  transferred  to  the  moulds  or  cooling  frames.  To  obtain  white 
soap,  an  addition  of  0-1  to  0-3  per  cent,  of  sodium  hydrosulphite  is  sometimes  made  to  the 
mass  before  discharging. 

As  a  rule,  soaps  are  made  not  from  pure  tallow,  but  from  mixtures  of  various  fats  and 
oils,  e.g.  palm  oil,  olive  oil,  oleine,  &c.  ;  in  such  cases  the  concentration  of  the  caustic 
soda  must  be  varied,  olive  oil  soap,  for  example,  requiring  lye  of  25°  to  28°  Be.,  which 
sometimes  escapes  salting-out. 

At  one  time  Marseilles  soaps  were  prepared  from  olive  oil  alone,  very  dilute  lye  being 
first  used  and  then  more  and  more  concentrated  ones.  But  nowadays  cotton-seed,  arachis, 
coco-nut,  palm-kernel  oils,  &c.,  are  generally  added,  the  processes  employed,  whether 
for  white  or  for  Marseilles  mottled  soap,  being  those  used  for  other  soaps. 

SOAPS  FROM  FATTY  ACIDS  or  OLEINE.  Oleine,  elaine,  or  commercial  oleic 
acid  forms  a  more  or  less  dense  liquid  with  a  colour  varying  from  pale  yellow  to  dark 
brown.  Less  highly  coloured  is  the  oleine  obtained  by  saponification  of  pure  fats  in 
autoclaves  and  separation  from  the  stearine  by  pressing  (oleine  of  saponification)  or  by 
enzymic  or  catalytic  decomposition  (catalytic  oleine),  whilst  that  obtained  from  impure 
fats  (bone  fat,  &c.)  or  by  means  of  sulphuric  acid  is  generally  darker  and  is  separated 
after  distillation  of  the  fatty  acids  (distillation  oleine).  If  an  oleine  contains  more  than 
3  per  cent,  of  non-saponifiable  substances,  it  is  certainly  distillation  oleine  (1  to  9  per 
cent.),  but  a  less  content  than  this  does  not  necessarily  indicate  oleine  of  saponificaticn 
since  the  modern  methods  of  exact  distillation  yield  oleines  almost  free  from  non-saponi- 
fiable matter. 

Oleine  always  contains  small  quantities  of  neutral  fats  and,  more  especially,  of  solid 
fatty  acids  (5  to  20  per  cent,  palmitic,  stearic,  &c.),  but  its  iodine  number  should  bs  between 


420  ORGANIC    CHEMISTRY 

75  and  85,  and  its  acid  number  at  least  179  (about  90  per  cent,  of  fatty  acids?,  expressed 
as  oleic  acid). 

Oleine  of  saponification  is  now  sold  at  a  rather  lower  price  than  tallow,  and  distillation 
oleine  at  a  still  lower  price  (48-s.  to  56s.  per  quintal).  Besides  for  eoap-making  it  is  Used 
for  treating  wool  which  is  to  be  carded  or  combed. 

Pure  oleic  acid  and  its  properties  have  already  been  considered  on  p.  298. 

The  manufacture  of  soap  from  fatty  acids  (see  p.  406  et  seq.),  although  it  gives  no 
glycerine,  is  economical  in  various  ways  ;  thus,  it  allows  of  a  more  rapid  saponification 
with  a  diminished  consumption  of  fuel  and  renders  possible  the  use  of  sodium  carbonate, 
which  is  cheaper  than  caustic  soda. 

100  kilos  of  oleine  would  require  about  19  kilos  of  sodium  carbonate  (instead  of  13-5 
of  caustic  soda),  but  in  practice  only  about  90  per  cent,  of  this  amount  is  used,  the  saponi- 
fication being  completed  with  caustic  soda  in  order  to  transform  the  small  amount  of 
neutral  fat  present  in  the  commercial  oleine.  A  hot  solution  (about  30  per  cent.)  of  the 
whole  of  the  sodium  carbonate  is  prepared  in  a  wide,  shallow  copper,  the  oleine  being 
then  added  gradually  in  a  thin  stream,  the  mass  being  mixed  and  heated  by  a  jet  of  direct 
steam  so  as  to  liberate  the  carbon  dioxide  and  prevent  the  froth  from  overflowing  ;  the 
latter  end  is  best  attained  by  adding  a  "little  salt  to  the  soda  solution  at  the  beginning 
or  by  the  passage  of  a  current  of  air.  The  caustic  soda  solution  (15°  to  18°  Be.)  is  then 
introduced  and  the  whole  heated,  salted-out  and  boiled,  as  already  described  for  tallow 
soap.  Pure  oleine  soap  is  at  first  rather  soft,  but  it  gradually  dries,  hardens,  and  becomes 
of  a  paler  yellowish  brown  colour  than  the  fresh  soap. 

When  soap  is  made  from  oleine  and  fats  together,  the  latter  are  first  saponified  and 
the  oleine  added  subsequently. 

RESIN  SOAPS  are  now  made  in  large  quantities  and  by  almost  all  soap  manu- 
facturers. Colophony  (see  Part  III)  contains  acids  which  behave  like  the  fatty  acids 
and  yield  similar  soaps,  which  lather  well  with  water  and,  when  mixed  with  ordinary 
fat  soaps,  diminish  the  price  considerably,  as  colophony  costs  only  14*.  to  28s.  per 
quintal. 

The  saponification  of  the  resin  is  effected  with  a  rather  strong  lye  (to  avoid  excessive 
frothing).  It  is  necessary  to  employ  pure  fats  and  pure  resin  (with  the  saponification 
number  160  to  180),  and  when  saponification  is  complete,  the  soap  must  be  well  "  finished  " 
in  order  to  avoid  excess  of  alkali,  which  would  cause  efflorescence  (also  avoidable  by  the 
addition  of  a  little  sodium  silicate  at  the  end  of  the  manufacture). 

The  resin  may  be  introduced  as  a  powder  directly  into  the  fused  fat,  but  it  is  more 
generally  added  after  the  fats  have  been  saponified  and  the  soap  salted  out  and  separated 
from  the  lye.  The  concentrated  caustic  soda  (100  kilos  at  20°  Be.  or  90  kilos  at  25°  Be. 
per  100  kilos  of  resin)  is  then  added  and  the  resin  gradually  disintegrated  by  heating  and 
stirring.  Boiling  is  continued  until  the  froth  almost  disappears  and  the  soapy  mass 
separates  well  from  the  lye  below  and  exhibits  the  proper  consistency  when  pressed  between 
the  lingers.  After  the  lye  has  been  removed,  the  soap  is  finished  with  a  little  boiling 
water,  then  left  for  12  to  24  hours,  and  finally  solidified  in  the  ordinary  frames  or  moulds. 

Good  resin  soaps  should  not  contain  more  than  40  per  cent,  of  resin,  but  in  some  cases 
they  show  as  much  as  100  per  cent,  (compared  with  the  fat),  and  it  is  a  question  whether 
resin  soaps  should  be  regarded  as  adulterated  ;  to  this  view  the  manufacturers  object, 
for  obvious  reasons.  Although  attempts  have  been  made  at  various  congresses  to  fix 
limits  (10,  20,  or  30  per  cent.)  to  the  proportion  of  resin  allowable,  none  of  these  are 
regarded.  The  case  would  be  met  by  stamping  the  resin -content  on  every  cake  of  soap, 
as  there  could  then  be  no  question  of  adulteration  or  fraud. 

Some  soaps  are  not  separated  from  the  lye,  or  grained  or  finished,  but  are  left  mixed 
with  the  lye  and  the  glycerine  ;  the  fats  employed  must  here  be  pure,  since  otherwise 
the  impurities  would  colour  the  soap.  Coco-nut  oil  and  palm-kernel  oil  are  more  especially 
used,  as  they  have  the  property  of  becoming  incorporated  or  remaining  dissolved  in  a 
large  excess  of  alkali  or  salt  and  of  forming  hard  soaps  with  even  large  proportions  of 
water  (200  to  300  per  cent.).  They  are  made  by  either  the  hot  or  the  cold  process,  and 
are  generally  cheap  soaps,  as  they  can  be  resined  and  charged,  not  only  with  large  quantities 
of  water,  but  also  with  salt,  silicate,  talc,  flour,  &c.  Solutions  of  salt  or  caustic  soda 
('20°  Be.),  even  in  excess,  facilitate  hardening,  whilst  potassium  carbonate  produces  a 
certain  softness  and  lustre.  The  silicate  and  salt  are  mixed  with  hot  caustic  soda  and  are 


MOTTLED    SOAPS 


421 


added  finally  to  the  soap  at  90°  to  95°.  The  method  of  procedure  is  that  generally 
employed  :  the  fat  is  added  to  part  of  the  caustic  or  carbonate  solution  wilh  which  it  is 
stirred  and  heated  to  boiling  ;  the  rest  of  the  alkali  is  then  introduced  and  finally  the  salt 
or  silicate  solution  in  small  portions  ;  the  mass  is  mixed,  left  in  the  covered  copper  over- 
night, when  it  falls  to  a  temperature  of  75°,  then  skimmed  and  cooled  in  the  frames.1 

When  these  soaps  are  prepared  in  the  cold,  the  palm-kernel  or  coco-nut  oil  is  mixed 
with  the  theoretical  quantity  of  concentrated  caustic  lye  (for  coco-nut  oil,  50  per  cent, 
of  lye  at  38°  Be.),  which  saponifies  these  and  other  fats  (tallow,  lard,  cotton-seed  oil,  arachis 
oil,  resin,  &c.),  even  in  the  cold,  with  spontaneous  rise  of  temperature  ;  they  are  commonly 
loaded  with  silicate,  talc,  salt,  &c. 

MOTTLED  SOAPS.  Until  30  to  40  years  ago,  mottled  soap  of  the  Marseilles  type 
was  made  with  olive  oil,  the  mottling  being  produced  by  adding  to  the  soap,  either  before 
or  after  graining,  ferrous  sulphate,  ferric  oxide,  ultramarine,  &c.  (0-2  to  0-6  per  cent,  of 
the  weight  of  fat),  discharging  into  the  cooling  frames  at  a  temperature  of  75°  to  80° 
and  allowing  to  cool  slowly  (4  to  6  days). 

Mottling  is  satisfactory  only  when  the  soap  does  not  contain  more  than  32  '5  to  34  per 
cent,  of  water,  and  hence  constitutes  a  safeguard  to  the  consumer  showing  that  he  is  not 
being  cheated  with  soap  overcharged  with  water.  Olive  oil  soap  can  be  well  mottled  if 
it  does  not  contain  more  than  the  above  quantities  of  water  and  colouring-matter,  and 
not  more  than  2  per  cent,  of  salt,  since  it  is  only  under  these  conditions  that  it  acquires 
just  that  fluidity  which,  at  the  solidifying  temperature,  offers  a  resistance  to  the  minute 
coloured  particles  (iron,  aluminium,  and  manganese  soaps,  and  metallic  hydroxides)  ; 
the  latter  gradually  group  themselves  into  veins,  whilst  the  drops  of  lye  and  soluble  salts 
fall  to  the  bottom.  If  the  quantity  of  water  is  raised,  the  equilibrium  is  displaced  and 
the  fluidity  increased,  so  that  the  colouring-matters  are  deposited.  But  if  other  folid 
fats  are  used  in  conjunction  with  the  olive  oil,  the  required  consistency  can  be  obtained 
with  as  much  as  50  per  cent,  of  water.  With  coco-nut,  palm-kernel,  and  palm  oils,  mottled 
soaps  can  be  prepared  containing  70  per  cent,  or  even  more  of  water,  in  addition  to  an 
increased  amount  of  alkali.  These  soaps,  however,  should  not  contain  more  than  2  per 
cent,  of  sodium  carbonate  and  less  than  10  per  cent,  of  dissolved  salts  ;  otherwise  the 
soap  will  effloresce  on  drying,  provided  that  it  is  sufficiently  stiff  to  permit  of  mottling. 

A  type  of  mottled  soap  which  is  often  prepared  with  a  yield  of  180  to  200  per  cent. 
is  that  from  almost  equal  quantities  of  sulphocarbon  olive  oil  and  coco-nut  or  palm  oil. 
In  this  case  the  manufacture  of  the  olive  oil  soap  is  carried  out  separately  as  far  as  the 
stage  where  it  is  separated  from  the  lye,  so  as  to  remove  the  impurities  ;  it  is  then  intro- 
duced into  the  pan  where  the  coco-nut  oil  has  been  saponified  in  the  hot  with  caustic 
soda  of  about  20°  Be.,  together  with  some  13  per  cent,  of  sodium  carbonate  dissolved 
in  water.  Unger  (1869)  found  that,  in  order  to  prevent  coco-nut  or  palm  oil  soap  from 
efflorescing  on  drying,  it  should  not  contain  more  than  43  per  cent,  of  sodium  carbonate, 
calculated  on  the  weight  of  coco-nut  oil  (i.e.  1  mol.  of  sodium  carbonate  per  4  mols.  of 
pure  coco -nut  soap).  After  mixing,  the  two  soaps  are  boiled  and  4  to  5  per  cent,  (on 
the  total  fat)  of  sodium  chloride  solution  of  24°  Be.  gradually  added  ;  the  heating  is 
continued  until  the  paste  boils  readily  without  adhering  to  the  sides  of  the  copper,  and 
the  steam  evolved  produces,  at  the  surface  of  the  soap,  veinings  and  crevices  in  the  form 

1  High  yields  are  given  by  the  following  mixtures 


Ss 

It 

Coco- 

Crude 

Palm 

Caustic 

Potassium 

9-2 

Yield 

nut 

oil 

palm- 
kernel 
oil 

oil 

Tallow 

Resin 

soda 
(26°  B6.) 

carbonate 
25°-30°  Be. 

20°-22° 
Be. 

SMC- 

o  ~ 

kilos 

kilos 

About  250  % 

90 

[or    90] 

— 

10 

— 

60 

65 

40 



— 

300  % 

— 

100 

— 

— 

— 

60 

100 

65 



— 

300  % 

50 

40 

20 

— 

15 

60 

65 

65 



— 

(resined) 

400  % 

100 

[or  100] 

— 

— 

— 

60 

100 

100 

50 

30 

800  % 

100 

[or  100] 

— 

— 

— 

80 

260  (20°  Be.) 

300 

60 

— 

1000  % 

100 

— 

— 

~ 

150-160  (22°  B6.) 

800 

422 

of  rosettes.  The  soap  will  then  emit  a  hollow  sound  and  will  not  form  bubbles  when 
struck  with  the  stirrer,  from  which  it  falls  in  broad  folds  which  become  covered  with  a 
dry  skin  ;  when  placed  on  glass,  it  is  quickly  coated  with  a  solid  layer  beneath  which  it 
remains  fused,  while  between  the  fingers  it  does  not  pull  out,  but  tends  to  solidify.  It 
is  important  that  it  should  not  contain  an  excess  of  caustic  soda  (not  more  than  0-2  to 
0-3  per  cent.  ;  it  is  best  neutral)  as  with  finished  soaps  ;  any  excess  may  be  eliminated 
by  adding  the  calculated  quantity  of  coco-nut  oil  or  of  hydrochloric  acid,  determined 
by  titration.  At  this  point  the  colouring-matter  is  well  mixed  in,  the  soap  being  then 
cooled  to  about  75°  and  poured  into  large  solidifying  frames  (holding  at  least  10  quintals) 
so  as  to  cause  slow  cooling  (in  winter  these  are  wrapped  round  with  cloths),  and  hence 
satisfactory  mottling.  These  mottled  soaps  of  high  yield  (up  to  400  per  cent.)  bear  the 
name  of  blue  mottled  or  Eschweg  soaps,  and  were  largely  used  some  years  ago.  Even 
now  their  consumption  is  considerable,  as  they  have  a  higher  detergent  power  than  finished 
soaps  owing  to  their  richness  in  alkali  carbonates  ;  they  dry  more  rapidly  than  resin 
soaps  and  owing  to  their  hardness  they  are  preferred  for  laundry  purposes,  there  being 
no  waste  even  when  the  clothes  are  vigorously  rubbed. 

The  formation  of  mottling  in  soaps  probably  obeys  the  laws  holding  in  the  solidifica- 
tion of  alloys  (solid  solutions)  and  the  figures  given  on  pp.  412  and  642,  and  in  Plate  III. 
of  vol.  i  of  this  work  ("Inorganic  Chemistry  ")  represent  well  the  impression  produced  by 
the  mottling  of  soap. 


FIG.  280. 


FIG.  281. 


When  almond-mottling  is  required,  an  iron  rod  12  to  15  mm.  in  diameter  is  drawn 
vertically  through  the  semi -solid  soap  in  the  solidifying  frame,  so  as  to  make  a  kind  of 
longitudinal  cut ;  similar  cuts,  parallel  to  the  first,  are  then  made  throughout  the  whole 
mass  at  distances  of  4  to  6  cm.,  and  afterwards  a  similar  series  perpendicular  to  the  others. 
When  solidification  is  complete,  the  whole  of  the  soap  is  traversed  by  dark  markings  in 
the  shape  of  almonds  arranged  like  the  leaves  on  acacia  twigs.  Other  mottlings  are  made 
either  by  machinery  or  by  hand. 

For  Eschweg  soaps  mixtures  of  various  fats  are  used,  e.g.  20  to  25  per  cent,  of  tallow, 
25  to  30  per  cent,  of  bone  fat,  10  to  15  per  cent,  of  cotton-seed  oil,  20  to  40  per  cent,  of 
palm-kernel  oil,  and  20  to  30  per  cent,  of  coco-nut  oil.  The  yield  is  usually  205  to  215 
per  cent.,  although  additions  of  silicate  (10  to  12  per  cent.)  are  sometimes  made. 

TRANSPARENT  SOAPS  were  at  one  time  obtained  by  dissolving  ordinary  soaps  in 
alcohol,  evaporating  the  latter  and  moulding  the  transparent  residue.  The  amount  of 
alcohol  used  was  subsequently  diminished  by  adding  glycerine,  and  at  the  present  time 
transparent  or  so-called  glycerine  soaps  are  made  from  mixtures  of  decolorised  tallow 
with  castor,  linseed,  and  coco-nut  oils,  with  addition  of  glycerine  and  also  of  20  to  30  per 
cent,  of  saccharose  or  glucose,  which  enhances  the  transparency.  To  this  mixture,  melted  . 
in  the  copper,  is  added  caustic  lye  at  30°  to  36°  Be\,  the  whole  being  mixed  until  a  homo- 
geneous emulsion  is  formed  ;  2  to  5  per  cent,  of  alcohol  is  then  introduced,  and  the 
mass  heated  to  75°,  cooled  to  50°,  and  poured  into  the  moulds.  For  some  of  thete 
soaps  as  much  as  40  per  cent,  of  pale  resin  is  employed. 

SOFT  SOAPS  are  usually  potash  soaps  of  linseed  oil  or  oleine,  while  in  summer  cotton- 
seed, colza,  sesame^  palm,  or  fish  oil  is  also  used. 

Some  of  these  soaps  are  transparent  (plain  or  variegated),  others  opaque  and  white 
or  yellowish.  For  every  100  kilos  of  fat,  about  160  kilos  of  caustic  potash  of  24°  Be. 
are  used,  the  yield  being  sometimes  as  much  as  235  per  cent.  ;  if  caustic  soda  is  partly 


COOLING,    BARRING,    ETC.,    OF    SOAP      423 

employed,  a  harder  soap  is  obtained,  but  the  yield  is  diminished.  Also  10  to  15  per  cent, 
of  resin  may  be  used  or  10  to  15  per  cent,  of  oil.  In  general  these  soaps  contain  carbonates. 
The  boiling  is  carried  out  in  the  usual  way,  and  is  continued  until  frothing  ceases, 
and  a  small  portion  placed  on  glass  remains  clear  for  some  time  without  forming  a  skin 
and,  on  cooling,  becomes  turbid  at  the  edges  and  exhibits  slight  veinings  of  lye.  If  this 
test  portion  remains  clear  but  presents  no  such  veinings,  lack  of  alkali  is  indicated. 


FIG.  282. 


FiQ.  283. 


Many  of  the  soft  soaps  now  used  contain  white  granules,  produced  by  the  addition 
of  tallow  or  stoarine,  which  crystallises  out  throughout  the  mass  of  poap  during  the  cooling, 
the  latter  occupying  4  to  8  weeks  ;  this  change  is  known  as  figging  and  the  yield  of  such 
soaps  is  often  as  high  as  240  per  cent. 

The  mamifacture  of  soda  soap  from  glycerides  by  means  of  lime  and  sodium  carbonate 
(Krebitz  process)  has  been  described  on  p.  408. 

Cooling  and  Solidification.     The  soap  from  the  copper  is  cooled  in  large  chests  or 
frames,  formerly  of  wood  but  now  of  iron,  as  was  suggested  by  Krull  in  1876  (Fig.  280). 
The  sides  of  these  are  fixed  by  means  of  bolts  and  nuts  and  hence  fit  perfectly  and  are 
readily    taken    apart.     In 
some  cases,  the  frames  are 
mounted  on  three  wheels 
so  as  to  be  transportable. 
To  prevent  any  impurities 
depositing   in    one     place 
and  so  producing  mottling, 
the  pasty  soap  in  the  frame 
is    stirred    with    wooden 
crutches  until  it  begins  to 
solidify ;     but,     if      slow 
solidification    is    required 
(for    mottled   soaps),    the 
sides   of    the   frame    are 
covered  with   straw  mat- 
tresses or  wool,  especially  FIG.  284. 
in  winter  (Fig.  281).     The 

frames  vary  in  capacity  from  100  to  6000  kilos  and,  according  to  the  amount  and  quality 
of  the  soap,  the  cooling  lasts  one  or  several  weeks.  The  walls  of  the  frame  are  then 
removed  and  the  large  block  cut  into  smaller  prismatic  blocks  by  means  of  thin  steel  wires 
worked  by  a  toothed -wheel  winch,  which  is  applied  to  various  points  of  the  block  (Fig.  282). 
The  small  blocks  are  discharged  on  to  a  truck  carrying  a  platform  which  can  be  raised 
(Fig.  283)  and  are  then  transferred  to  the  barring  machine  (Fig.  284),  where  each  block 
is  placed  between  A  and  B  and  forced  by  means  of  the  plate  A  and  the  toothed  wheel, 
R,  against  the  frame,  B,  fitted  with  adjustable  crossed  steel  wires.  The  long  bars  thus 


424  ORGANIC    CHEMISTRY 

obtained  between  B  and  C  are  then  pressed  against  the  vertical  wires  of  the  frame,  C, 
and  thus  cut  into  cakes  of  the  required  size.  There  are  many  such  machines  of  different 
types,  some  fitted  with  fixed  and  others  with  universal  frames. 

During  recent  years  a  method  has  been  devised  of  preparing  cakes  directly  from  the 
hot  soap  from  the  copper,  without  using  the  largo  cutting  machines  (slabbers)  ;  in  this 
way  much  time  is  saved,  waste  and  scraps  are  diminished  in  amount  and  the  subsequent 
seasoning  shortened.  The  hot  soap  is  rapidly  cooled  and  compressed  in  the  Klumpp 
apparatus  (Fig.  285),  being  first  transferred  to  the  jacketed  reservoir,  L,  where  it  is  kept 
liquid  by  means  of  hot  water  in  the  jacket.  The  plate,  c,  consisting  of  a  double -walled 
box  surrounded  by  cold  water,  has  a  movable  base,  h,  resting  on  the  piston  of  a  hydraulic 
pump,  K.  The  box,  c,  is  filled  with  liquid  soap  and  the  wheel,  V,  turned  so  as  to  press 
on  to  the  surface  of  the  soap  the  large  plate,  a,  which  is  kept  horizontal  by  the  four  rods, 
N,  of  the  press,  while  inside  it  cold  water  circulates. 

When  this  plate  is  firmly  fixed  and  the  soap  begins  to  solidify,  a  pressure  of  50  atmos. 
is  applied  by  means  of  the  press,  K,  this  pressure  being  increased  to  250  atmos.  when 
the  soap  is  quite  cold  and  solid.  The  ordinary  cutting  machines  are  then  used  to  cut 
these  slabs  into  marketable  pieces,  which  lose  little  water  even  in  the  air. 

Seasoning  or  drying  of  the  soap,  to 
bring  it  to  the  degree  of  moistness  required 
by  the  trade,  is  effected  by  keeping  the 
cakes  on  frames  in  well-ventilated  cham- 
bers for  several  weeks  or  even  months. 
This  slow  drying  is  now  generally  replaced 
by  drying  in  hot  air.  furnished  cheaply  by 
Perret  furnaces,  which  burn  waste  coal  or 
slack.  The  soap  is  spread  out  on  gratings 
superposed  on  trucks,  which  are  gradually 
introduced  into  a  brickwork  gallery  ;  hot 
air  traverses  the  gallery,  entering  at  the 
opposite  end  at  50°  to  60°  and  being  dis- 
charged at  35°  to  45°.  The  seasoning  is 
FIG.  285.  complete  in  3  to  6  days,  but  if  the  tem- 

perature is  too  high  at  first,  or  the  drying 

too  rapid,  the  soap  softens  and  becomes  deformed  and  crushed.  To  give  the  cakes  a 
smooth  surface,  and  so  render  efflorescence  and  cracking  more  difficult,  as  they  issue 
from  the  dryer  they  are  subjected  to  the  action  of  a  slight  steam-jet,  which  melts  them 
superficially. 

STATISTICS.  The  largest  and  most  up-to-date  soap-factories  of  the  present  day  are 
in  the  United  States  and  England,  next  in  importance  being  those  of  Germany  and  France. 
Italy  imports  more  than  220,000  quintals  of  fat  (1904)  for  soap  and  candle-making. 
In  1894  there  were  300  factories  and  an  appreciable  exportation  (33,000  quintals  of  common 
soap  and  1000  of  perfumed  soap)  which  in  1903  reached  40,680  quintals  of  common  soap, 
sent  to  England  and  the  United  States,  and  1230  of  perfumed  soap  to  India  and  Egypt. 
In  1909  the  exports  were  28,450  quintals  of  common  soap,  worth  £74,000,  and  2150  of 
perfumed  sorts,  worth  £19,340  ;  in  1910,  40,000  quintals  of  common  soaps,  valued  at 
£104,200,  and  1915  of  perfumed  (£17,240)  were  exported.  The  importation  amounted 
to  16,369  quintals  of  ordinary  and  964  of  perfumed  soap  in  1903  ;  to  19,000  quintals 
of  common  kinds  from  France  and  1100  of  perfumed  from  Germany,  France,  and  England 
in  1904  ;  to  23,230  quintals  of  common  soap,  valued  at  £48,400,  1120  of  perfumed 
(£15,680),  and  5300  quintals  of  cart-grease  and  stiff  fats,  consisting  largely  of  lime  soaps, 
resins,  and  mineral  oils  and  valued  at  £2544,  in  1905  ;  40,000  quintals  of  ordinary  soap, 
costing  £96,000,  1617  quintals  of  perfumed  soap  (£23,360),  and  2500  quintals  of  cart -and 
engine -grease  in  1910. 

The  total  production  of  soap  in  Italy  in  1905  was  estimated  at  about  1,500,000  quintals. 
France  was  at  one  time  the  greatest  exporter  of  soap,  160,000  quintals  of  non-perfumed 
kinds  being  exported  in  1890  and  268,000  (worth  £440,000)  in  1900  ;  but  at  the  present 
time  England  is  far  ahead.  In  1898  France  produced  about  3,000,000  quintals  of  soap 
(one-fourth  mottled),  one-half  of  this  in  the  Marseilles  district ;  the  total  value  was 
£5,600,000.  The  port  of  Marseilles  receives  annually  5,000,000  quintals  of  oily  fruits 


SOAP    STATISTICS  425 

and  seeds,  and  a  similar  quantity  of  crude  oils  and  fats  for  extraction  and  refining 
(including  mineral  oils),  the  total  yearly  production  of  the  Marseilles  oil,  soap,-  and 
.stearine  industries  being  nearly  £40,000,000. 

The  province  of  Marseilles  produced  500,000  quintals  of  mottled  and  50,000  quintals 
of  white  soap  in  1866  and  200,000  quintals  of  mottled  and  1,400,000  of  white  soap  in 
1808. 

In  1894  England  exported  290,000  quintals  of  soap  and  in  1897  about  370,000  ;  in 
1900  the  exports  of  soap  were  valued  at  £920,000,  and  those  of  stearine  candles  at  £400,000  ; 
in  1907  the  soap  exported  amounted  to  £1,480,000  ;  and  in  1909  to  650,000  quintals 
(112,000  being  imported  in  that  year).  The  English  Sunlight  Company  alone  has  a 
capital  of  £14,000,000. 

The  production  of  soap  in  England  in  1907  was  as  follows  :  soft  soap,  49,900  tons  ; 
toilet  soap,  70,400  tons  ;  ordinary  soap,  665,000  tons  ;  and  various  other  soaps,  24,200 
tons,  the  total  value  being  estimated  at  £7,055,000.  The  exportation  of  ordinary  soap 
alone  amounted  to  119,540  tons  in  1909  and  134,560  tons  (£1,357,776)  in  1910,  in  which 
year  the  imports  were  less  than  20,000  tons. 

The  total  production  of  soap  in  England  is  about  4,000,000  quintals  per  annum. 

The  United  States  produced  soap  to  the  value  of  £13,650,000  in  1904  and  of  £22,280,000 
in  1909  ;  the  exports  amounted  to  £789,000  in  1910  and  £800,000  in  1911,  and  the  imports 
to  £165,000  in  1910  and  £160,000  in  1911. 

In  1903  Germany  imported  7,740,000  quintals  of  oils  and  fats,  and  in  1905  about 
9,000,000  quintals,  of  the  value  of  £13,000,000,  the  exports  in  1905  being  2,432,000  quintals, 
worth  £2,920,000.  Also,  in  1905,  306,320  quintals  (145,000  in  1903)  of  oleine,  valued  at 
£300,000,  were  imported. 

In  1903  Germany  exported  84,160  quintals  of  soap  of  all  qualities,  and  in  1905  almost 
99,000  quintals,  worth  £440,000,  the  imports  in  that  year  being  14,500  quintals,  valued 
at  £48,000  ;  in  1905,  the  exports  of  soap  were  about  £640,000. 

In  1906  Japan  imported  soap  to  the  value  of  £36,000,  and  in  1907  £52,000,  half  of  the 
amount  coming  from  Germany. 

The  Argentine  Republic  possesses  200  soap  factories,  representing  a  total  capital  of 
about  £240,000,  and  giving  an  annual  production  valued  at  about  £640,000  ;  considerable 
quantities  of  perfumed  and  medicinal  soaps  are  imported. 

The  value  of  soap  l  varies  considerably  with  the  quality,  the  degree  of  fineness,  the 

1  Analysis  of  Soap.  As  a  rule,  the  commercial  value  of  a  soap  is  determined  from  tho  quantity  of  combined 
fatty  acids  which  it  contains,  and  as  the  percentage  of  these  varies  with  the  degree  of  moistness,  great  care  must 
be  taken  in  sampling  the  soap.  The  cake  is  first  weighed  and  the  sample  cut  in  such  a  way  that  the  inner  and 
outer  portions  are  taken  in  the  proper  proportions  ;  the  sample  is  then  cut  up  fine,  rapidly  mixed  and  immedi- 
ately enclosed  in  a  vessel  with  a  ground  stopper  so  that  water  may  not  be  lost. 

The  analysis  consists  of  some  or  all  of  the  following  determinations  : 

(1)  Water.    This  estimation  is  not  usually  made,  as  it  involves  a  long  operation,  while  it  is  possible  to  cal- 
culate the  proportion  of  water  indirectly  after  all  the  other  components  have  been  determined.    The  direct 
estimation  is  made  by  weighing  5  to  10  grms.  of  the  finely  divided  soap  rapidly  in  a  tared  dish  containing  a  small 
glass  rod  and  filled  to  the  extent  of  one-third  with  sand  which  has  been  previously  calcined.    The  dish  and  its 
contents  are  heated  first  in  an  oven  at  60°  to  70",  the  fused  soap  being  carefully  mixed  with  the  sand  until  a  skin 
of  soap  no  longer  forms  at  the  surface  ;  the  temperature  is  then  raised  to  105°  to  110°,  at  which  it  is  maintained 
until  constant  weight  is  reached.     The  total  loss  in  weight  represents  the  water. 

(2)  Unsaponified  Fat.    The  dry  residue  from  the  water  estimation  is  introduced  into  a  Soxhlet  extractor 
(see  p.  374)  and  extracted  for  a  couple  of  hours  on  the  water-bath  with  light  petroleum  in  a  tared  flask  ;  the  solvent 
is  subsequently  distilled  off  and  the  extracted  fat  dried  at  110°  until  of  constant  weight. 

(3)  Fatty  Acids,  Free  Alkali,  Glycerine,  and  Resin.     The  residual  matter  in  the  Soxhlet  apparatus  (or  the  dry 
soap  itself)  is  extracted  with  neutralised  absolute  alcohol,  which  dissolves  the  soap,  glycerine,  and  free  caustic 
alkali  ;    the  last  of  these  is  determined  immediately  by  titrating  the  alcoholic  solution  with  normal  sulphuric 
acid  in  presence  of  phenolphthalein.     The  liquid  is  afterwards  largely  diluted  with  water,  heated  for  a  long  time 
on  the  water-bath  to  remove  all  the  alcohol,  and  treated  with  a  measured  volume,  in  excess,  of  normal  sulphuric 
acid,  the  liquid  being  then  heated  in  a  beaker  on  a  water-bath  and  on  a  sand-bath  until  the  clear  fatty  acids  (and 
the  resin,  if  present)  separate  at  the  surface.     After  cooling,  the  solidified  layer  of  acids  is  pierced  with  a  rod  and 
the  liquid  poured  on  to  a  tared  filter  in  a  stemless  funnel,  the  fatty  acids  being  then  washed  with  hot  water,  and 
the  whole  brought  on  to  the  filter.     The  excess  of  free  sulphuric  acid  in  the  whole  of  the  wash-water  is  deter- 
mined by  titration  with  normal  caustic  potash.     This  then  gives  the  amount  of  sulphuric  acid  fixed  by  the  alkali 
of  the  soap  and  hence  also  the  combined  alkali  expressed  as  Na.jO.     Evaporation  of  the  liquid  to  dryness  and 
extraction  with  absolute  alcohol  removes  any  glycerine  present  in  the  soap,  this  being  weighed  after  evaporation 
of  the  alcohol.     The  fatty  acids  on  the  filter  are  treated  with  a  couple  of  c.c.  of  a'lcohol  to  remove  any  moisture 
and  then  with  sufficient  light  petroleum  to  dissolve  all  these  acids  ;   the  filtrate  is  evaporated  in  a  tared  dish, 
dried  at  105°  to  constant  weight  and  the  residual  fatty  acids  weighed.     To  determine  any  resin  which  may  be 
present  in  the  fatty  acids,  part  of  the  latter  is  weighed,  dissolved  in  20  c.c.  of  alcohol  and,  after  addition  of  phenol- 
phthalein, hydrolysed  in  the  hot  with  a  slight  excess  of  alkali ;   after  cooling,  the  liquid  is  made  up  to  110  c.c. 
with  ether,  treated  with  powdered  silver  nitrate  and  allowed  to  deposit  the  precipitated  silver  stearate,  palmitatc, 
and  oleate.    One-half  of  the  filtered  solution  (containing  soluble  silver  resinate)  is  treated  with  20  c.c.  of  dilute 


426  ORGANIC    CHEMISTRY 

content  of  fatty  acids,  and  the  degree  of  purity.  The  ordinary  soaps  used  in  laundries 
and  in  the  textile  industries,  which  are  made  from  sulphocarbon  olive  oil  and  contain 
60  to  65  per  cent,  of  fatty  acids,  cost  44s.  to  48s.  per  quintal,  according  to  the  conditions 
of  the  market  and  the  prices  of  prime  materials  (fats  and  oils).  Soaps  loaded  with  water 
and  other  substances  may  cost  much  less  ;  fine,  perfumed  soaps  cost  up  to  £4  to  £8  per 
quintal. 

GG.    POLYHYDRIC   ALDEHYDIC   OR   KETONIC 
ALCOHOLS 

CARBOHYDRATES 

(Sugars,  Starch,  Cellulose) 

This  group  of  substances  might  have  been  included  in  the  preceding 
chapter,  FF,  where,  in  paragraphs  D  and  E,  certain  very  simple  aldehydic 
and  ketonic  alcohols  have  been  considered.  But,  partly  owing  to  custom 
(since  it  has  been  the  rule  to  include  in  the  group  of  Carbohydrates  only  ketonic 
or  aldehydic  polyhydric  alcohols  with  six  [monosaccharides]  or  a  multiple 
of  six  carbon  atoms  [polysaccharides]  and  containing  hydrogen  and  oxygen 
in  the  proportion  of  2  :  1,  as  in  water),  and  partly  because  this  group  embraces 
all  the  sugars,  which  exhibit  special  characters  very  different  from  those 
of  glycollic  aldehyde  (which  should  be  the  first  member).  So  that  even  at 
the  present  time  the  carbohydrates  are  considered  separately,  although  the 
brilliant  researches  of  Emil  Fischer,  commenced  in  1887,  have  extended  this 
group  to  compounds  with  five,  four,  or  three  carbon  atoms,  on  the  one  hand, 
and  to  monosaccharides  with  six,  eight,  or  even  nine  carbon  atoms  on  the 
other. 

These  monosaccharides  bear  the  name  of  Monoses  (biases,  trioses,  tetroses, 
pentoses,  hexoses,  heptoses,  octoses,  nonoses,  &c.,  according  to  the  number  of 
carbon  atoms  they  contain),  while  the  polysaccharides  (formed  by  the  con- 
densation of  two  or  more  monose  molecules)  are  called  generally  polyoses 
and,  in  particular,  hexabioses,  hexatrioses,  &c.,  according  as  they  are  formed 
by  the  condensation  of  two,  three,  &c.,  hexose  molecules. 

A.  MONOSES 

All  the  monoses  are  aldehydic  or  ketonic  polyhydric  alcohols  containing 

H 

the  characteristic  grouping,  — C  —  C — ,  i.e.  a  hydroxyl  group  united  with  a 

OH  6 

carbon  atom  adjacent  to  a  carbonyl  (CO)  group.     When  the  carbonyl  exists 

H 

as  an   aldehydic  group,  — C  —  C-H,  these  monoses  are  called  Aldoses,  whilst 

OH  6 

hydrochloric  acid  (1 :  2)  and  filtered,  an  aliquot  part  of  the  filtrate  being  evaporated  in  a  tared  capsule,  dried 
at  100°  and  the  residual  resin  weighed ;  the  weight  of  the  resin  is  diminished  by  0-00235  grm.  for  every  10  c.c. 
of  ethereal  solution  of  silver  resinate,  this  being  the  amount  of  oleic  acid  removed  by  the  ether.  The  true  weight 
of  the  fatty  acids,  free  from  resin,  can  then  be  calculated. 

(4)  Soda,  Salt,  Sulphates,  Silicate,  &c.     The  residue  from  the  Soxhlet  apparatus,  after  separation  of  the  fat 
and  soap,  is  treated  two  or  three  times  with  50  to  60  c.c.  of  hot  water  and  the  solution  filtered,  made  up  to  a 
definite  volume  and  divided  into  four  parts :   one  of  these  is  titrated  with  normal  sulphuric  acid,  using  phenol- 
phthalein  as  indicator,  to  ascertain  the  sodium  carbonate  ;  in  a  second  portion,  the  sodium  chloride  is  determined 
by  titration  with  silver  nitrate ;   the  third  is  precipitated  with  barium  chloride  and  the  weight  of  the  barium 
sulphate  and  hence  that  of  the  sodium  sulphate  in  the  soap,  determined.    The  fourth  portion  is  treated  with 
hydrochloric  acid  and  the  silica,  thus  separated  from  the  silicate,  weighed. 

(5)  Ash  and  Mineral  "  Filling."     The  ash  obtained  by  burning  a  definite  weight  of  pure  soap  is  about  40  per 
cent,  greater  than  the  total  alkali  (expressed  as  NaaO).     If  the  proportion  is  much  higher  than  is  indicated  by 
this  relation,  the  excess  represents  mineral  filling. 


CARBOHYDRATES  427 

?  I 

when  it  exists  as  a  ketonic  group,  — C  —  C  —  C — ,  they  are  termed  ketoses,  so 

OH  6      J 
that  we  have  aldohexoses,  ketohexoses,  &C.1 

The  monoses  have  the  general  properties  of  the  aldehydes  or  ketones  and 
hence  form,  on  oxidation,  the  corresponding  monobasic  acids,  e.g.  pentonic, 
hexonic  acids,  &c.  Since  the  aldoses  contain  a  primary  alcoholic  group, 

X° 
OH-CH2-[CH-OH]n-Cf     , 

XH 

they  can  also  be  oxidised  to  dibasic  acids  containing  the  same  number  of 
carbon  atoms,  whilst  when  the  ketoses  are  oxidised,  the  carbon  atom  chain 
is  ruptured  and  acids  with  lower  numbers  of  carbon  atoms  formed. 

On  reduction,  both  the  aldoses  and  the  ketoses  take  up  two  atoms  of 
hydrogen,  forming  the  corresponding  alcohols  ;  the  hexoses  give  hexitols 
and  the  pentoses  pentitols. 

Like  all  aldehydes,  they  reduce  ammoniacal  silver  solutions  in  the  hot, 
giving  silver  mirrors. 

When  heated  with  alkali,  they  turn  brown  and  then  resinif y . 

They  reduce  alkaline  copper  solution  (Fehling's  solution)  in  the  hot. 

When  heated  with  excess  of  phenylhydrazine  dissolved  in  acetic  acid, 
they  yield  yellow,  crystalline  phenylosazones,  insoluble  in  water.2 

In  dealing  with  the  hexoses  later  on,  we  shall  see  how  the  constitutions 
of  the  monoses  in  general  are  determined. 

Of  the  various  monoses,  containing  from  2  to  9  carbon  atoms,  only  certain 
of  the  hexoses  are  fermentable,  that  is,  give  alcohol  and  carbon  dioxide  under 
the  action  of  ferments  or  enzymes  (see  pp.  112  and  122).  Of  the  hexoses, 
some  ferment  readily,  others  with  difficulty,  and  others  again  not  at  all,  in 
dependence  on  their  stereochemical  configurations  and  possibly  on  the  asym- 
metric constitution  of  the  enzymes.  d-Glucose,  d-mannose,  and  d -fructose 
ferment  easily,  and  d-galactose  with  difficulty,  whilst  1-glucose  and  1-mannose 
do  not  ferment. 

GENERAL  METHODS  OF  FORMATION  OF  THE  MONOSES : 

(a)  From  the  polyoses  by  hydrolysis  with  dilute  acids,  water  being  added  and  several 
molecules  of  hexose  obtained  : 

Cia^On  (saccharose)  +  H20  =  2C6H1206. 

(b)  By  oxidation  of  the  corresponding  alcohols  by  nitric  acid :  e.g.  Arabitol,  C6Hi205, 

1  The  two  classes  of  sugars,  aldoses  and  ketoses,  are  distinguished  by  means  of  Romijn's  reaction  with  a  solution 
of  iodine  and  borax,  which  oxidises  all  the  aldoses  (galactose,  glucose,  mannose,  arabinose,  xylose,  rhamnose 
maltose,  lactose),  while  it  either  does  not  oxidise  the  Jceloses  or  oxidises  them  but  slightly  (sorbose,  fructose ; 
saccharose  and  rafflnose  are  oxidised  to  a  small  extent). 

8  They  form  first  pJienylhydrazones  (see  p.  206) : 

H— C— OH  H— C— OH 

c  =  io  +  H,!N-NH-C,H,  =  H2o  +          c  =  N-NH-C.H,; 

I  I  • 

these  phenylhydrazones  then  react  with  two  other  molecules  of  phenylhydrazine,  giving  ammonia,  aniline,  and 
phenylosazone  : 


H— c— ;o 


— :H  NH,iNHC,H6  C=N-NHC,H, 

=  NH,  +  NHj-C.H,  +  HjO  +    | 
j  aniline  C=N-NHC,H, 


C  =  N-NH-C.H, 

I 

which  is  the  characteristic  group  of  the  phenylosazones.    The  latter  crystallise  readily  and  in  a  pure  state  from 
a  dilute  pyridine  solution.    Reduction  of  the  phenylosazones  yields  osamines,  e.g.  glucosamine,  C,HnO,-NH,. 


428  ORGANIC    CHEMISTRY 

gives  Arabinose,  C5H10O5  (pentose) ;  xylitol  (stereoisomeric  with  arabitol)  gives  xylose 
and  Mannitol,  C6Hj4O6,  mannose. 

(c)  Oxidation  of  glycerol  gives  dihydroxyaoetone,  OH-CH2-CO-CH2'OH,  which 
is  a  triose,  its  constitution  being  indicated  by  the  fact  that  it  forms  a  cyanohy- 
drin,  OH-CH2-C(OH)(CN)-CH2-OH,  the  latter  yielding  trihydroxyisolutyric,  acid, 
OH-CH2-C(OH)(COOH)-CH2-OH,  and  this,  on  reduction,  isobutyric  acid  having  a 
known  constitution. 

(d)  By  treating  the  bromo -derivatives  of  the  aldehydes  with  baryta  water.      Thus 
nionobromaldehyde  gives  Glycollic  Aldehyde, 

^°  //Q 

CH2Br-C<f      +  H2O  =  HBr  +  OH-CH2-<X      , 

XH  \H 

which  is  the  simplest  member  of  the  sugar  group  and   does  not  give  all  the  reactions 
of  the  sugars. 

(e)  With  lime-water,  formaldehyde  undergoes  aldol  condensation  (sec  p.  205),  giving 
Formose, 

,/°  ^ 

6H-Cf       -  OH-CHo-CH(OH)-CH(OH)-CH(OH)-CH(OH)-Cf     , 

XH  \H 

which  is  a  syrupy  mixture  of  compounds,  CfiH12Of). 

Under  the  influence  of  light  and  moisture,  plants  fix  C02  and  form  starch  (CGH10O5)n, 
which  is  a  polyhexose,  6C02  +  6H20  =  C6H]206  +  602,  the  hexose  then  giving  up  water 
and  yielding  starch.  According  to  Baeyer,  the  C02  gives  first  formaldehyde,  then  a  hexose 
(monose),  and  finally  starch  (polyose).1 

Also  2  mols.  of  glyceraldehyde  (derived,  e.g.  from  acrolein)  undergo  the  aldol  condensa- 
tion and  yield  a  hexose  (termed  acrose)  which  is  a  constituent  of  formose. 

(/)  It  is  possible  to  pass  from  one  aldose  to  a  higher  one  through  the  cyanohydrin, 
which  is  first  hydrolysed  to  an  acid  with  an  extra  carbon  atom.  Such  an  acid  readily 
forms  a  lactone  with  the  hydroxyl  in  the  y-position,  and  treatment  of  the  lactone  with 
sodium  amalgam  (addition  of  H2)  yields  the  higher  aldehyde  (aldose) : 

^ 
OH-  CH2  •  CH(OH)  •  CH(OH)  •  CH(OH)  •  CH(OH)  •  Cf 

\H 

12  3  4  5  67 

OH-CH2-CH(OH)-CH(OH)-CH(OH)-CH(OH)-CH(OH)-COOH 

y  |8  a 

OH-CH2-CH(OH)-CH(OH)-CH-CH(OH)-CH(OH)-CO  +  H4      — > 


O 

7° 
OH-  CH2  •  CH(OH)  •  CH(OH)  •  CH(OH)  •  CH(OH)  •  CH(OH)  •  cf     . 

Heptose 

By  the  same  ketonic  (lactonic)  synthesis,  the  keptose  can  be  converted  into  odose  and 
nonose. 

1  It  was  shown  by  Butlerow  that  formaldehyde — and  later  by  E.  Fischer  that  glyceraldehyde — can,  under 
certain  conditions  and  in  the  presence  of  bases  (baryta),  give  rise  to  sugar  (a-acrose).  In  1905  H.  and  A.  Euler 
found  that  under  no  conditions  do  other  alkali  hydroxides  give  an  appreciable  amount  of  sugar,  whilst  with  dilute 
solutions  of  sodium  carbonate  or,  better,  with  calcium  carbonate  or  lead  hydroxide  at  100°,  first  glycollic  aldehyde 
and  glyceric  aldehyde  are  formed  and  finally  a  Tceto-arabinose,  the  phenylosazone  of  which  melts  at  159°  to  161°. 
The  conditions  for  the  production  of  hexoses  from  formaldehyde  are  not  yet  defined,  but  O.  Loew  stated  that, 
with  milk  of  lime,  he  obtained  formose,  which  is  a  mixture  containing  i-fmctose  (a-acrose). 

D.  Berthelot  and  H.  Gaudechon  (1910)  found  that  the  action  of  ultra-violet  rays  on  10  per  cent,  solutions  of 
various  sugars  at  a  temperature  of  80°  to  90°  leads  to  the  rapid  formation  of  the  following  quantities  of  gas  : 

CO              CH4  H2  CO2 

Levulose  (ketose)           ....         83                 8  9  15 

Glucose  (aldose) 12                12  76  22 

Maltose  (gives  2  mols.  glucose)                           12                11  77  21 

Saccharose  (gives  glucose  and  levulose)  .45                  8  47  16 

They  found  also  that  prolonged  action  of  ultra-violet  rays  on  a  mixture  of  CO2  and  H,  yields  a  small  quantity 
of  CO  and  of  formaldehyde. 

These  facts  tend  to  confirm  J.  Stoklasa's  observations  (1906-1910)  on  the  formation  of  hydrogen  as  final 


T  ETHOSES    AND    PENTOSES  429 

TETROSES,  C4H8O4,  and  PENTOSES,  C6H10O5 

Just  as  the  hexoses  can  be  converted  into  pentoses,  the  latter  can  give 
rise  to  TETROSES.  For  instance,  d-,  1-,  and  i-erythrose  are  obtained  by 
oxidising  d-arabonic  acid,  d-arabinosoxime,  and  natural  i-erythritol  respec- 
tively with  hydrogen  peroxide  : 

OH-CH2-  [CH-OHVCOOH  +  0  =  H20  +  C02  +  OH-CH2-  [CH-OH]2-CHO 

Tetrose 

The  tetroses  are  also  obtained  by  oxidising  (with  H202)  the  calcium  salts 
of  pentonic  acids  in  presence  of  ferric  acetate,  which  acts  as  an  oxidising  catalyst. 

The  pentoses  (Arabinose,  Xylose,  &c.)  occur  abundantly  as  Pentapolyoses 
or  Pentosans  (Araban,  Xylan)  in  many  vegetable  organisms  (straw,  wood, 
maize  husks,  &c.),  from  which  they  are  obtained  by  simple  boiling  with  dilute 
acids.1  Pentoses  do  not  ferment. 

product  of  the  degradation  of  carbohydrates  by  the  action  of  glycolytic  enzymes,  which  have  an  important  function 
in  the  assimilation  of  carbon  dioxide  in  the  chlorophyll  cells,  and  also  to  render  valid  Stoklasa's  hypothesis  (1907) 
that  the  formaldehyde  necessary  to  the  formation  of  carbohydrates  by  the  simple  polymerisation  assumed  by 
I3acyer  can  result  from  the  reaction,  2CO2  +  2Ha  =  02  +  2H-CHO.  Stoklasa  and  Zdobnicky  (1910)  have 
obtained  inactive  sugars  and  aldehyde  by  the  action  of  ultra-violet  rays  on  carbon  dioxide  and  hydrogen  in  the 
nascent  state  in  presence  of  caustic  potash  (with  initial  formation  of  potassium  bicarbonate,  which,  in  the  nascent 
state  and  with  nascent  hydrogen,  generates  the  sugar)  and  have  disproved  the  view  held  by  Fischer  (1888-1889), 
Loew  (1888-1889),  Neuberg  (1902),  and  Euler  (1906)  that,  in  the  synthesis  of  sugars  from  formaldehyde,  pentoses 
are  formed  ;  the  sugars  they  obtained  are  not  asymmetric  and  are  hence  not  fermented  by  ordinary  alcoholic 
ferments.  According  to  Stoklasa,  the  function  of  the  chlorophyll  in  plants  is  to  absorb  the  ultra-violet  rays  of 
sunlight.  From  the  aqueous  distillate  of  the  leaves  of  various  plants,  F.  Hartwig  and  T.  Curtius  (1910)  have 


separated  (by  means  of  m-nitrobenzhydrazide,  a  :  p-hexylenealdehyde,  CH3-CH,-CH2-CH  :  CH-g(      ,  the  hydia- 

\H 
zone  of  which  melts  at  167°. 

1  By  the  term  Pentosans  are  meant  those  polysaccharides  which  are  related  to  the  pentoses  in  the  same  way 
as  are  starch,  inulin,  &c.,  to  the  hexoses,  and  which  give  pentoses  and  also  hexoses  on  hydrolysis.  From  starch 
they  arc  distinguished  by  their  Isevo-rotation.  From  plants  the  pentosans  are  extracted  by  means  of  dilute 
alkali  according  to  the  method  given  by  Tollens,  Stone,  and  Schulze  (1888-1901)  :  the  finely  divided  vegetable 
matter  is  treated  twice,  for  some  hours  at  the  ordinary  temperature,  with  seven  times  its  weight  of  2  per  cent. 
ammonia  solution  to  eliminate  in  the  soluble  state  part  of  the  proteins,  salts,  &c.,  and  to  remove  the  more  soluble 
part  of  the  hcmicellulose  (this  would  give  little  pentose  on  subsequent  hydrolysis).  After  the  dark  ammoniacal 
liquid  has  been  separated  by  filtration  through  cloth  and  by  squeezing  in  a  press,  the  solid  residue  is  extracted 
with  ten  times  its  weight  of  5  per  cent,  caustic  soda  solution,  with  which  it  is  first  macerated  in  the  cold  for  ten 
to  twelve  hours,  and  then  heated  in  a  reflux  apparatus  on  a  water-bath  for  six  hours.  The  mass  is  next  filtered 
through  cloth  and  the  residue  pressed  and  washed  several  times  with  water  until  the  total  volume  of  solution 
obtained  is  equal  to  that  of  the  caustic  soda  solution  used. 

This  brown  liquid  is  evaporated  to  some  extent  on  a  water-bath  and  is  then  treated  in  the  cold  with  an  equal 
volume  of  90  per  cent,  alcohol.  The  voluminous,  flocculent  precipitate  of  gum  (pentosans)  thus  obtained  is 
collected  on  cloth,  washed  and  purified  by  repeatedly  dissolving  in  dilute  acid  and  reprecipitating  with  alcohol, 
this  procedure  being  continued  until  the  gum  leaves  a  minimal  ash  on  incineration. 

To  pass  from  the  pentosans  to  the  pentoses,  the  moist  gum  is  hydrolysed  (Conneler  and  Tollens,  1892  and  1903) 
by  digestion  for  12  hours  with  25  parts  of  water  and  2-5  parts  of  hydrochloric  acid  of  sp.  gr.  1-19,  the  mixture 
being  finally  heated  on  a  water-bath  until  the  furfural  reaction  (red  coloration  with  aniline  acetate  paper)  begins 
to  make  its  appearance  (about  two  hours).  After  filtration  of  the  cold  liquid  and  neutralisation  with  lead  car- 
bonate (testing  with  Congo-red  paper),  a  few  drops  of  barium  hydroxide  are  added  and  the  liquid  filtered  to 
remove  precipitated  lead  chloride  and  barium  carbonate.  The  solution  is  concentrated  on  a  water-bath  und.er 
reduced  pressure,  mixed  with  a  little  alcohol,  filtered  and  concentrated  to  a  syrup.  This  is  taken  up  with  methyl 
alcohol  and  the  solution  filtered  to  remove  mineral  and  other  impurities.  The  alcohol  is  then  evaporated  and 
the  residue  seeded  with  a  few  crystals  of  xylose  or  arabinose  and  left  in  a  desiccator  until  the  whole  mass  crys- 
tallises (this  sometimes  requires  several  weeks). 

In  order  to  separate  the  arabinose  and  xylose,  which  often  occur  together,  Ruff  and  Ollendorff  (1899)  treat 
the  mixed  pentoses  with  eight  times  their  weight  of  75  per  cent,  alcohol  and  nearly  their  own  weight  of  bcnzyl- 
phcnylhydrazine  dissolved  in  a  little  absolute  alcohol.  After  several  weeks'  rest  with  frequent  shaking,  there 
separates  arabinose  benzylphenylhydrazone,  which,  in  the  pure  state  melts  at  174°  and,  when  treated  with  excess 
of  formaldehyde,  liberates  the  arabinose  ;  the  latter  is  soluble  in  water,  whilst  formaldehyde  benzylphenylhydra- 
zone remains  undissolved. 

The  aqueous  arabinose  solution,  after  separation  and  concentration  to  a  syrupy  consistency,  deposits  pure 
urabinose  in  crystals.  The  corresponding  hydrazone  of  xylose  is  soluble  in  75  per  cent,  alcohol,  and  yields  xylose 
when  decomposed  with  formaldehyde  in  the  manner  described  above.  The  xylose  can  also  be  separated,  according 
to  Bertrand  and  Tollens  (1900),  by  treating  the  mixture  of  pentoses  with  2  parts  of  water,  1  part  of  cadmium 
carbonate,  and  0-5  part  of  bromine.  The  mixture  is  heated  for  a  short  time  on  the  water-bath,  then  left  for 
twelve  hours,  evaporated,  taken  up  with  water,  filtered,  again  evaporated,  and  mixed  with  alcohol  ;  this  pro- 
cedure yields  crystals  of  cadmium  bromoxylonale,  C5H9O6BrCd.  But  before  carrying  out  this  separation,  it  is 
necessary  to  make  sure  that  the  mixture  contains  no  galactose  or  glucose.  These  sugars  can  be  detected  by 
oxidising  the  mixture  with  nitric  acid  (sp.  gr.  1-15)  on  the  water-bath  and  evaporating  the  liquid  to  two-thirds 
of  its  volume.  If  the  liquid  remains  turbid  in  the  cold,  the  presence  of  mucic  acid,  derived  from  galactose,  is 
indicated  ;  and  if,  after  neutralising  with  potassium  carbonate,  acidifying  with  acetic  acid  and  concentrating, 
potassium  hydrogen  saccharate  separates,  the  presence  of  ylucose  —  which  gives  saccharic  acid  on  oxidation  —  ig 
demonstrated. 


430  ORGANIC    CHEMISTRY 

Arabinose  and  xylose  are  aldoses,  OH-CH2-  [CH(OH)]3-CHO.  By 
bromine  water  these  two  pentoses  are  oxidised  with  formation  respectively  of 
arabonic  and  xylonic  acids,  OH-CH2- [CH-OH]3-C02H,  which  are  stereoiso- 
ineric  ;  with  more  energetic  oxidising  agents,  they  give  trihydroxyglutaric 
acid.  On  reduction  they  yield  the  corresponding  alcohols,  arabitol  and  xylitol 
(see  p.  189),  which  are  also  stereoisomerides.  By  way  of  the  corresponding 
cyanohydrins  they  can  be  converted  into  hexoses  (via  hexonic  acids).  All 
these  reactions  aid  in  establishing  the  constitution  of  these  pentoses. 

As  they  contain  asymmetric  carbon  atoms,  these  sugars  are  optically  active, 
and  they  exhibit  the  phenomenon  of  muta-rotation ;  thus,  for  freshly  prepared 
solutions  of  xylose,  the  value  of  the  specific  rotation  is  [a]D  =  75°  to  80°,  while 
five  minutes  after  the  sugar  is  dissolved  it  has  the  stable  rotation  +  19°. 

When  pentoses  are  boiled  with  dilute  sulphuric  acid  or  with  hydrochloric 
acid  of  sp.  gr.  1-06  (12  per  cent.),  they  yield  furfural,  C4H3O-CHO  (aldehyde), 
which  distils  over  and  gives  a  characteristic  and  intense  red  coloration  with 
aniline  and  hydrochloric  acid,  a  phenylhydrazone  with  pheiiylhydrazine, 
and  a  slightly  soluble  condensation  product  with  phloroglucinol.1 

Treatment  of  any  pentose  or  hexose  with  caustic  soda  in  presence  of  air  or  other  oxidi- 
sing agent  (e.g.  HgO)  yields  no  trace  of  saccharic  acid,  but  gives  formic  acid  and  monobasic 
hydroxy-acids  (e.g.  glycollic,  dl-glyceric,  trihydroxybutyric,  and  various  pentonic  and 
hexonic  acids)  ;  if  air  is  excluded,  aldotetroses,  formaldehyde,  a  little  2  :  3-dienols,  bioses, 
and  glyceraldehyde  are  mainly  formed. 

Recent  work  has  shown  that  the  furfural  obtained  on  distillation  of  vegetable  sub- 
stances with  12  per  cent,  hydrochloric  acid  is  derived  not  merely  from  true  pentosans, 
but  also  from  oxycellulose,  glycuronic  acid,  &c.  ;  niethylpentosans  give  methylfurfural. 
Hence  Cross  and  Bevan  suggest  the  name  furfuroids  for  substances  other  than  true  pen- 
tosans which  give  furfural.  On  the  other  hand,  it  has  been  proposed  by  Tollens  that  the 
term  pentosan  be  applied  to  the  whole  of  the  substances  (furfuroids  and  true  pentosans) 
which  give  furfural  when  distilled  with  12  per  cent,  hydrochloric  acid.  Hydroxymethyl- 
furfural  (see  below)  does  not  distil  in  presence  of  acids  but  undergoes  resinification,  and 
hence  escapes  the  Tollens  method  of  estimating  furfural. 

Until  comparatively  recent  times  it  was  assumed  that  the  pentosans  were  derived  from 
the  hexoses  and  poly  hexoses,  since  it  was  known  that  4:-hydroxymethylfurfuraldehyde, 

CHO-C  :  CH-CH  :  OCH2-OH 


is  obtained  on  heating  levulose,  d-mannose,  d-glucose,  d-galactose,  chitose,  &c.,  in  a  sealed 
tube  with  0-3  per  cent,  of  oxalic  acid,  while  4,-bromomethylfurfural, 

CHO •  C  :  CH- CH  :  O  CH2Br, 


1  Quantitative  Determination  of  Pentoses  and  Pentosans.  Mint  and  Tollens  (1902)  distil  in  a  flask  similar  to 
that  shown  in  Fig.  17  (p.  11),  about  5  gnns.  of  the  substance  with  100  c.c.  of  12  per  cent,  hydrochloric  acid,  the 
heating  being  carried  out  in  an  oil-bath  at  160°.  Thirty  c.c.  of  liquid  are  distilled  over  every  twelve  to  fifteen 
minutes,  in  which  time  30  c.c.  of  fresh  acid  are  added  by  means  of  a  tapped  funnel,  this  procedure  being  continued 
as  long  as  the  distillate  reddens  a  strip  of  filter-paper  moistened  with  an  acetic  acid  solution  of  aniline.  To  the 
distillate  is  added  an  excess  (double  the  amount  of  furfural  expected)  of  pure  phloroglucinol  dissolved  in  12  per 
cent,  hydrochloric  acid.  The  volume  of  the  liquid  is  made  up  to  400  c.c.  with  the  same  acid  in  a  graduated  flask, 
which  is  well  shaken  and  left  for  12  hours,  at  the  end  of  which  time  the  precipitate  is  collected  on  a  tared  filter, 
washed  with  150  c.c.  of  water,  dried  for  four  hours  in  an  oven  and  weighed.  The  weight  of  furfural  is  obtained 
by  dividing  this  weight  by  a  variable  factor,  which  has  the  following  values  for  different  amounts  (in  grms.)  of 
the  phloroglucinol  compound  :  0-20  (1-820)  ;  0-22  (1-839) ;  0-24  (1-856) ;  0-26  (1-871) ;  0-28  (1-884) ;  0-30  (1-895) ; 
0-32  (1-904) ;  0-34  (1-911) ;  0-36  (1-916) ;  0-38  (1-919) ;  0-40  (l-92ft) ;  0-45  (1-927) ;  0-50  (1-930)  ;  0-60  or  more 
(1-931).  The  xylan  is  calculated  by  multiplying  the  quantity  of  furfural  by  1-64,  the  araban,  by  2-02,  while  for 
mixed  pentosans,  the  factor  1-84  is  employed. 

Another  method  of  procedure  consists  in  precipitating  the  furfural  with  phenylhydrazine  and  estimating 
the  nitrogen  in  the  precipitate. 

Jolles  (1906),  however,  neutralises  almost  completely  (to  methyl  orange)  the  distillate  containing  the  furfur- 
aldehyde,  then  adds  10  c.c.  (moir,  if  necessary)  of  a  decinormal  sodium  bisulphite  solution,  and  after  two  hours 
titrates  the  excess  of  bisulphite  with  a  deciuoimal  iodine  solution  (1  c.c.  of  which  corresponds  with  0-0075  grui. 


HEXOSES  481 

is  obtained  by  heating  levulose  (or  filter-paper,  cotton,  cellulose,  straw,  starch,  dextrose, 
lactose,  glycogen,  &c.)  under  pressure  with  chloroform  saturated  at  0°  with  hydrogen 
bromide.  Further,  when  the  oxime  of  levulose  is  heated  with  concentrated  caustic  potash 
solution,  the  uitrile  is  first  formed  and  then  hydrocyanic  acid  and  d-arabinose  : 

OH-CH2-[CH-OH]4-CH:NOH  — >  H20  +  OH-CH2-  [CH-OH]4-CN 
— >  HCN  +  OH-CH2-[CH-OH]3-CHO. 

Oxidation  of  d-gluconic  acid  with  peroxides  also  gives  d-arabinose. 

Ketohexoses  in  general,  when  heated  with  dilute  acids  (e.g.  with  0-3  per  cent,  of  oxalic 
acid  under  a  pressure  of  3  atmos.),  are  largely  transformed  into  hydro xymethylfurfural, 
whilst  the  aldohexosea  undergo  this  change  only  to  a  very  slight  extent ;  if  mineral  acids 
are  used,  or  oxalic  acid  in  larger  quantity,  levulinic  acid  is  obtained  instead  of  hydroxy- 
methylfurfural. 

U.  Nef 's  recent  work  (1910)  tends  to  show  that,  in  plants,  pentosans  cannot  be  derived 
from  the  hexoses,  but  that  they  are  formed  rather  from  either  aldotetroses  and  formalde- 
hyde or  2-carbon-atom  sugars  and  glyceraldehyde.  The  hescoses,  in  their  turn,  would 
be  formed,  not  from  pentoses  and  formaldehyde,  but  rather  from  2  mols.  of  glyceraldehyde 
or  3  mols.  of  a  2-carbon-atom  sugar,  or  even  from  1  mol.  of  a  2-carbon-atom  sugar  and 
1  of  an  aldotetrose. 

XYLOSE  is  readily  obtained  by  boiling  with  dilute  sulphuric  acid  plants  containing 
it,  especially  jute,  bran,  straw,  or,  better  still,  apricot  stones  or  maize  hueks.  It  bears  ako 
the  name  of  wood-sugar,  and  is  yielded  by  the  decomposition  of  gluconic  acid. 

When  pure,  it  crystallises  and  forms  a  phenylosazone  melting  at  160°. 

rf-ARABINOSE  is  lee vo -rotatory,  but  is  obtained  from  calcium  d-gluconate  and 
hydrogen  peroxide  and  from  d-glucose.  In  the  pure  state  it  forms  prismatic  crystals. 

i-ARABINOSE  is  the  optically  inactive  racemic  isomeride,  and  is  found  in  the  urine 
of  persons  suffering  from  pentosuria. 

Z-ARABINOSE  is  obtained  by  boiling  vegetable  gum  with  dilute  sulphuric  acid.  It  is 
dextro-rotatory,  but  is  designated  a  laevo -compound  because  it  is  related  chemically  to 
1-glucose.  It  forms  sweet-tasting  crystals  melting  at  160°,  and  its  phenylosazone  melts  at 
157°. 

Two  other  pentoses  are  ;  RIBOSE,  which,  with  nascent  hydrogen,  gives  adonitol 
(a  pentahydric  alcohol,  OH'CH2- [CH'OH]3'CH2'OH,  and  the  only  sugar -alcohol  yet 
discovered  in  plants,  the  leaves  of  which  are  able  to  transform  it  into  starch  ;  the  sap 
of  Adonis  vernalis  contains  as  much  as  4  per  cent,  of  adonitol) ;  and  d-lyxose,  which  is 
obtained  from  galactonic  acid  and  melts  at  101°. 

Higher  homologues  are  the  Methylpentoses  :  FUCOSE,  contained  in  algse  ;  CHINO- 
VOSE,  ISORHAMNOSE,  and  RHAMNOSE  (or  Isodulcite),  C5H?06-CH3,  which  is 
obtained  by  boiling  quercetin  and  other  glucosides  with  dilute  sulphuric  acid. 

According  to  Rosenthaler  (1909),  Methylpentose  in  presence  of  pentoses  can  be  recog- 
nised by  heating  the  solution  for  a  few  minutes  on  a  boiling  water-bath  with  HC1  of  sp.  gr. 
1-19  and  observing  the  yellow  liquid  thus  obtained  in  the  spectroscope:  methylfurfural, 
from  methylpentose  (even  as  little  as  0-0005  grm.)  gives  absorption  bands  between  the 
blue  and  green.  The  reaction  is  still  more  sensitive  if  a  little  acetone  is  added  before 
heating,  the  liquid  then  being  coloured  red  (by  the  methylfurfural)  and  giving  a  sharp 
absorption  band  in  the  yellow  (D  line)  ;  pentoses  do  not  give  this  reaction  if  the  liquid  is 
heated.  Other  sensitive  reactions  are  obtained  with  phloroglucinol,  orcinol,  resorcinol, 
pyrogallol,  aniline  acetate,  &c. 

HEXOSES,  C6H1206 

'  These  are  of  frequent  natural  occurrence  and  exist  in  various  optically  active 
stereoisomerides,  since  they  contain  four  asymmetric  carbon  atoms,  while  they 
also  form  inactive  racemic  compounds.  They  are  substances  of  sweet  taste, 
and  are  extremely  soluble  in  water,  but  in  alcohol  they  dissolve  but  slightly 
and  in  ether  not  at  all ;  they  crystallise  with  great  difficulty  and  decompose 
when  distilled.  Their  phenylhydrazones  are  soluble,  and  their  phenylosa- 
zones  insoluble  in  water.  When  boiled  with  hydrochloric  acid  they  all  give 


432  ORGANIC    CHEMISTRY 

(1)  Levulinic  Acid  (CH3-CO-CH2-CH2-C02H),  the  silver  salt  of  which  forms 
characteristic  crystals,  and  (2)  a  brown  amorphous  mass  of  so-called  humic 
substances.  With  methyl  alcoholic  ammonia,  the  hexoses  form  Osamines 
e.g.  Glucosamine,  C6Hn05-NH2. 

They  reduce  Fehling's  solution  or  ammoniacal  silver  solution  in  the  hot, 
and  with  oxidising  agents  they  yield  hexonic  acids  and  then  lower  acids  down 
to  oxalic. 

With  lime  they  form  additive  compounds  decomposable  by  carbonic  acid  ; 
with  boiling  milk  of  lime  they  turn  brown  and  give  Hexosaccharine  (lactone 
of  saccharic  acid),  C6H1005.  By  the  combined  action  of  concentrated  sul- 
phuric and  nitric  acids,  they  are  converted  into  pentanitrates,  while  with  alcohols 
and  gaseous  hydrogen  chloride  they  form  ethers  (glucosides) .  The  aldohexoses 
give  the  fuchsine-sulphurous  acid  reaction  (see  p.  206),  which  is,  however, 
not  shown  by  the  ketohexoses.  The  mode  of  formation  of  the  phenylosazones 
is  described  on  p.  427. 

With  hydroxylamine  they  forjn  oximes,  e.g.  d-Glucosoxime,  which  can 
be  converted  into  the  corresponding  nitrile  and  then,  by  elimination  of  HCN, 
into  the  aldopentose  (d-arabinose). 

The  hexoses  are  formed  in  various  organisms  and  can  also  be  obtained 
by  hydrolysing  polyhexoses  with  dilute  acids  or  enzymes. 

The  optical  activity  of  the  hexoses  indicated  by  the  prefixes  d-,  1-,  and  i- 
indicates  the  sign  of  that  of  the  substances  with  which  they  are  connected 
genetically,  but  the  fact  that  the  actual  direction  of  the  rotation  does  not 
always  correspond  with  this  prefix  is  a  source  of  some  confusion.  It  must 
also  be  noted  that  the  rotatory  powers  of  the  hexoses  and  pentoses  are 
lowered  when  the  sugars  are  dissolved  in  a  centinormal  alkali  solution 
at  37°. 

Synthetically  the  hexoses  can  be  obtained  from  formaldehyde  (see  Note, 
p.  428),  as  well  as  from  the  hexahydric  alcohols  by  gentle  oxidation  and  from 
the  hexonic  acids  by  reduction.  E.  Fischer  has  synthesised  d-glucose  com- 
pletely from  glycerine,  by  way  of  (1)  glyceraldehyde,  (2)  inactive  fructose, 
which,  with  hydrogen,  yields  (3)  inactive  mannitol,  oxidation  of  this  giving 
(4)  mannose  and  (5)  racemic  mannonic  acid,  the  latter  being  resolved  into 
its  (6)  active  components  by  means  of  strychnine  ;  d-mamionic  acid,  in 
presence  of  pyridine  and  water  in  the  hot,  produces  (7)  d-gluconic  acid  and 
this,  on  reduction,  d-glucose. 

The  relations  between  hexoses  and  pentoses  were  indicated  in  the  last  Note 
(see  p.  429). 

As  was  mentioned  above,  fermentation  with  yeast  occurs  only  with 
d-glucose,  d-fructose,  d-galactose,  d-mannose,  and  glycerose,  no  fermentation 
taking  place  with  sorbose,  the  pentoses,  1-glucose,  1-fructose,  1-mannose,  or 
d-mannoheptose.  So  that  only  the  stereoisomerides  of  a  certain  group  are 
fermentable. 

The  structures  of  the  hexoses  are  deduced  partly  from  their  general  reactions 
and  partly  from  the  following  facts  : 

The  chain  of  six  carbon  atoms  in  the  hexoses  is  normal,  since  reduction 
with  hydrogen  yields  a  hexahydric  alcohol,  which  is  further  reduced  by  heating 
with  hydriodic  acid  to  normal  sec.  hexyl  iodide,  CH3-  CH2-  CH2-  CH2-  CHI-  CH3  ; 
the  constitution  of  the  latter  is  shown  by  the  fact  that  the  corresponding 
secondary  alcohol  is  oxidised  to  n-propylacetone,X)H3-  CH2-CH2-  CH2-  CO  CH3, 
this,  on  oxidation,  giving  finally  butyric  and  acetic  acids  of  known  constitu- 
tion. 

The  hexoses  contain  five  hydroxyl  groups,  as  they  yield  pentacetyl-deriva- 
tives  when  boiled  with  acetic  anhydride  and  sodium  :.acetate  or  zinc  chloride. 
Their  constitutional  formula  hence  cannot  be  other  than  : 


GLUCOSE 

H     H     H     H 

I        I       I        I          /H 
H2C  —  C  —  C  —  C  —  C  —  C/ 

1      1      J        I       I  ° 

OH  OH  OH  OH  OH 

since,  if  two  hydrox^yl  groups  were  at  any  moment  united  with  one  carbon  atom, 
a  molecule  of  water  would  be  eliminated  immediately.  Further,  with  hydrogen 
the  hexoses  form  hexitols,  which  are  not  aldehydic  but  only  alcoholic  in 
character  and  do  not  give  up  H2O  under  any  conditions,  so  that  two  hydroxyl 
groups  are  not  combined  with  one  carbon  atom.  Neither  can  it  be  supposed 
that  three  hydroxyl  groups  are  united  with  the  terminal  carbon,  thus  : 

/OH 
— C^-OH,  because  if  this  were  so  water  would  be  readily  separated  and  an 

XOH 

acid  formed,  in  which  case  the  aqueous  solution  should  conduct  the  electric 
current  and  have  a  dissociation  constant  much  greater  than  that  of  acetic 
acid  ;  but  this  is  not  found  to  be  the  case. 

Combination  with  bases  does  occur  (with  the  hexabioses),  but  the  com- 
pounds formed  are  additive  compounds. 

Since  then  there  are  a  number  of  different  hexoses,  all  showing  the  same 
general  behaviour,  they  must  have  the  same  constitution,  the  differences 
being  due  to  differences  in  the  spatial  structure. 

Theoretically,  16  active  stereoisomeric  aldo-hexoses  are  possible,  and 
14  of  them  have  been  already  prepared.  The  rotatory  powers  of  the  phenylosa- 
zones  and  phenylhydrazones  may  be  of  opposite  signs  to  those  of  the  corre- 
sponding hexoses. 

d-GLUCOSE  (Grape  Sugar,  Dextrose,  Starch  Sugar),  C6H12O6,  is  an  aldose  found  in 
abundance  in  grapes  and  many  other  sweet  fruits  in  company  with  d-fructose  ;  it  also  occurs 
in  the  urine  of  diabetic  patients.  It  crystallises  from  water  with  1H20,  which  it  loses  at 
120°,  and  from  alcohol  in  the  anhydrous  form,  melting  at  146°.  In  aqueous  solution  it  has 
the  specific  rotation  +  53°  at  a  temperature  of  20°,  but  it  exhibits  muta-rotation,  the 
rotatory  power  being  about  double  the  above  value  in  freshly  prepared  solutions  which 
have  not  been  boiled.  Owing  to  its  rotatory  power,  glucose  can  be  estimated  polarimetri- 
cally  (see  later,  Sugar). 

When  saccharose  (a  dextro-rotatory  hexabiose)  is  heated  with  dilute  acid,  it  is  con- 
verted into  a  Isevo -rotatory  mixture  of  equal  proportions  of  glucose  ( +  )  and  fructose  or 
levulose  (  — ),  which  bears  the  name  Invert  Sugar,  the  change  being  known  as  inversion, 
since  it  is  accompanied  by  alteration  of  the  sign  of  the  optical  rotation. 

On  oxidation,  d-glucose  gives  d-Gluconic  Acid,  OH-CH2-  [CH-OH]4-COOH,  and  then 
the  dibasic  Saccharic  Acid,  CO2H- [CH-OH]4-CO2H,  which,  like  tartaric  acid,  gives  a 
slightly  soluble  acid  potassium  salt ;  the  latter  serves  to  characterise  d-glucose,  it  being 
sufficient  to  oxidise  with  nitric  acid  and  then  precipitate  the  saccharic  acid  with  saturated 
potassum  acetate  solution.  When  reduced,  d-glucose  yields  d-sorbitol  (hexahydric  alcohol). 

The  sugar  forms  a  phenylosazone,  melting  at  204°  to  205°,  and  two  phenylhydrazones, 
melting  respectively  at  115°  and  144°. 

When  heated  above  140°,  glucose  is  converted  into  caramel. 

In  dilute  solution  it  reduces  Fehling's  solution  in  the  hot,  and  on  this  reaction  is  based 
the  estimation  of  glucose.1 

1  Estimation  of  Glucose.  In  the  chemical  way  the  estimation  is  effected  by  means  of  Fehling's  solution 
by  the  method  described  later  in  the  section  on  Saccharose,  about  10  grms.  of  solid  glucose  or  15  to  20  grms. 
of  the  syrupy  product  being  dissolved  in  water,  made  up  to  100  c.c.  in  a  graduated  flask  and  filtered  through  a 
dry,  covered  filter.  Polarimetric  estimation  is  not  usually  applicable  owing  to  the  presence  of  dextrin,  some- 
times to  the  extent  of  40  per  cent.,  this  increasing  the  rotation.  The  dextrin  is  determined  by  dissolving  5  grms. 
of  the  glucose  in  400  c.c.  of  water,  adding  40  c.c.  of  HC1  of  sp.  gr.  1-125,  heating  for  two  hours  on  a  boiling 
water-bath,  cooling,  neutralising  exactly  with  NaOH  and  making  up  to  500  c.c.  The  total  dextrose  (including 
that  formed  by  hydrolysis  of  the  dextrin)  in  this  solution  is  now  determined  by  means  of  Fehling's  solution. 
The  difference  between  the  amounts  of  glucose  found  before  and  after  the'action  of  acid,  multiplied  by  0-9,  gives 
II  28 


434 


ORGANIC    CHEMISTRY 


Barfoed  has  proposed  the  following  reaction  for  detecting  the  presence  of  minimal 
quantities  of  glucose,  (0-2  mgrm.)  mixed  with  lactose,  maltose,  dextrin,  and  saccharose  : 
to  5  c.c.  of  Barfoed's  reagent  (an  acetic  acid  solution  of  normal  cupric  acetate)  in  a  test- 
tube  is  added  the  dilute  aqueous  sugar  solution  (about  1  per  cent.),  the  mixture  being 
heated  on  a  boiling  water-bath  for  3J  minutes,  allowed  to  cool  for  10  minutes,  and  filtered. 
If  the  filter  retains  red  cuprous  oxide,  the  presence  of  dextrose  is  demonstrated. 

MANUFACTURE  OF  GLUCOSE.  One  hundred  kilos  of  starch  are  mixed  with  500 
litres  of  water  containing  5  kilos  of  concentrated  sulphuric  acid,  and  the  mass  heated  to 
40°  to  50°  and  then  introduced  into  a  suitable  autoclave  or  converter  (conical  or  cylindrical, 
capable  of  withstanding  6  atmos.),  coated  internally  with  lead  and  externally  with  insu- 
lating material.  A  current  of  steam  is  then  passed  in  and  the  temperature  raised  to  160°. 
By  allowing  the  steam  to  escape  after  this  temperature  has  been  reached,  the  empyreumatic 
oils  (which  are  of  disagreeable  odour)  are  carried  away  ;  the  steam  is  condensed  in  cooled 
coils  (the  heat  being  used  to  heat  water).  The  temperature  of  the  mass  is  then  maintained 
at  80°  until  a  test  portion  gives  no  blue  colour  with  iodine  and  no  precipitate  with  lead 
acetate  (or  potassium  silicate),  these  being  indications  of  the  saccharification  of  the  dextrin 
and  gummy  matters  ;  a  further  sign  of  this  is  the  non-formation  of  a  precipitate  with 
alcohol.  The  duration  of  the  heating  is  S  to  4  hours. 

The  mass  is  then  decanted  into  the  neutralisation  vats,  which  are  furnished  with 
stirrers,  and  finely  divided  calcium  carbonate,  suspended  in  a  large  quantity  of  water, 
gradually  added  in  order  to  neutralise  and  precipitate  the  sulphuric  acid.  After  thorough 
mixing  of  the  mass,  it  is  allowed  to  settle  and  the  liquid  then  decanted  into  another  vessel, 
where  the  calcium  sulphate  remaining  in  solution  is  precipitated  by  the  addition  of  a  little 
ammonium  oxalate. 

The  liquid  is  next  filter-pressed,  evaporated  in  a  vacuum  to  28°  to  30°  Be.,  decolorised 
in  the  hot  by  means  of  dry  blood  mixed  with  powdered  wood  charcoal  or  by  passing  through 
vertical  filters  filled  with  the  charcoal  similar  to  those  used  in  sugar  refineries.  It  is  then 
concentrated  in  a  vacuum  (see  Sugar  Industry)  either  to  41°  to  42°  Be.,  to  give  solid  compact 
glucose  separating  in  the  cooling  vats  (fitted  with  stirrers),  or  to  about  65°  Be.,  when 
ready  formed  crystals  of  glucose  are  added.  The  temperature  is  lowered  to  18°  to  20°,  and 
after  3  or  4  days  the  separated  crystals  centrifuged  and  so  freed  from  the  syrupy  portion, 
which  retains  the  dissolved  dextrin  and  other  impurities.  To  obtain  granulated  glucose 
the  solution  is  concentrated  only  to  30°  to  32°  Be.  ;  after  8  to  10  days  in  the  cold,  a  granular 
hydrated  glucose  separates. 

When  a  very  dense  liquid  glucose  (so  dense  that  its  specific  gravity  cannot  be  deter- 
mined with  the  ordinary  hydrometers)  is  required,  a  little  dextrin  is  left  in  the  sugar  so  as 
to  prevent  crystallisation. 

The  theoretical  yield  of  pure  glucose  from  100  kilos  of  dry  starch  is  110  kilos. 

In  some  factories  the  starch  is  saccharified  with  a  little  nitric  acid,  which  gives  a  less 
highly  coloured  syrup  and  is  more  rapid  in  its  action.  The  nitric  acid  is  then  eliminated 
by  means  of  sulphurous  acid,  which  is  oxidised  at  the  expense  of  the  nitric  acid  to  sulphuric 
acid,  this  being  readily  precipitable  with  lime. 

The  advantages  of  transforming  starch  into  glucose  by  means  of  hydrofluoric  acid 
consist  in  a  rapid  and  complete  hydrolysis,  ready  separation  of  the  whole  of  the  acid  as 
barium  fluoride,  and  the  production  of  a  glucose  with  a  pure  flavour. 

In  1901  Calmette  found  that,  after  heating  crushed  cereals  with  double  the  amount  of 

the  quantity  of  dextrin.     The  acidity  should  not  exceed  2  c.c.  of  normal  caustic  soda  per  100  grms.  of  syrup. 
The  proportion  of  ash  varies  from  0-2  to  0-7  per  cent. 

Solid  commercial  glucose  contains  65  to  75  per  cent,  of  glucose  and  the  liquid  35  to  45  per  cent.  In  pure 
solution,  glucose  can  be  estimated  by  means  of  the  specific  gravity  : 


Density 

Degrees 

Per  cent,  of  pure 

Density 

Degrees 

Per  cent,  of  pure 

at  17-5° 

Be. 

glucose 

at  17-5° 

\ 

B6. 

glucose 

1-0192 

2-7 

5 

1-1310 

16-4 

35 

1-0381 

5-3 

10 

1-1494 

18-8 

40 

1-0571 

7-5 

15 

1-1680 

20-6 

45 

1-0761 

10-1 

20 

1-1863 

22-7 

50 

1-0946 

12-4 

25 

1-2040 

24-4 

55 

1-1130 

14-6 

30 

1-2218 

26-1 

60 

FRUCTOSE 


435 


1  per  cent,  hydrochloric  acid  for  1  hour  at  100°,  1  hour  at  110°,  and  a  third  hour  at  120°, 
and  then  cooling,  the  mass  may  be  converted  completely  into  glucose  by  the  action  of 
Mucedince. 

USES.  Large  quantities  of  glucose  are  consumed  for  making  sweet  syrups,  caramel,1  fer- 
mented liquors,  sweets  and  wine,  preserving  fruit,  adulterating  honey,  dressing  textiles,  &c. 

In  1909-1910  Italy  possessed  15  glucose  factories,  producing  676  quintals  of  the  solid 
and  65,000  of  the  liquid  sugar  ;  the  total  revenue  from  the  tax  of  manufacture  amounted 
to  £51,000,  solid  glucose  paying  32s.  and  the  liquid  16s.  per  quintal.  The  Customs  duty 
is  40,?.  for  liquid  and  64s.  for  solid  glucose  per  quintal.  Importation  is  very  f  mall  in  amount 
and  the  exports  only  300  quintals  of  liquid  glucose.  In  the  United  States,  where  glucose 
is  made  from  maize,  the  amount  produced  reached  800,000  quintals  in  1907. 

In  France  the  16  factories  working  in  1908  to  1909  produced  200,000  quintals  of  glucose, 
about  48,000  being  used  in  breweries  while  72,000  were  exported. 

England  imported  46,500  tons  (£462,940)  of  glucose  in  1909  and  62,500  tons  (£595,808) 
in  1910.  The  United  States  exported  90,000  tons,  valued  at  £1,196,200,  in  1911. 

The  output  in  Germany,  with  about  26  factories,  was  as  follows  (quintals) : 


Solid  Glucose 

Glucose  Syrup 

Caramel 

Produced 

Exported 

Produced 

Exported 

Produced 

1897-1898 

72,000 

348,000 

1901-1902 

99,400 

28,874 

492,700 

76,800 

48,000 

1902-1903 

96,170 

12,026 

545,300 

30,620 

— 

1903-1904 

75,050 

6,113 

469,461  . 

1  3,000 

35,630 

1904-1905 

53,000 

2,890 

324,340 

10,432 

34,690 

1905-1906 

91,900 

— 

582,750 

— 

43,000 

1906-1907 

88,300 

— 

477,506 

— 

.  44,244 

1907-1908 

81,836 

— 

466,340 

— 

48,461 

1908-1909 

87,623 

506,600 

— 

44,180 

The  diminished  production  in  1904-1905  was  due  to  a  poor  potato  crop  and  an  over- 
production of  beet-sugar,  the  less  an.cunt  exported  being  caused  partly  by  enhanced  prices 
and  partly  by  increased  production  in  other  countries. 

Glucose  syrup  with  a  specific  gravity  of  42°  Be.  is  sold  in  Italy  at  48s.  to  52s.  per  quintal, 
whilst  in  Germany,  where  there  is  no  manufacturing  tax,  it  costs  about  28s.  ;  the  crystalline 
sugar  costs  rather  more. 

d-FRUCTOSE  (Levulose,  Fruit-Sugar)  occurs  abundantly,  together  with  glucose,  in 
sweet  fruits,  and  is  also  found  in  large  quantities  in  honey  (which  contains  natural  invert 
sugar).  The  hydrolysis  of  inulin  (a  polyhexose  found  in  dahlia  tubers)  yields  d-fructose 
alone.  The  sugar  is  Icevo-rotatory  and  fermentable.  It  has  the  constitution  of  a  ketose, 
OH  •  CH2  •  [CH  •  OH]3  •  CO  •  CH2  •  OH,  hydrolysis  of  its  cyanohydrin  giving  the  heptonic  acid, 

OH-CH2-[CH-OH]3-C(OH)-CH2-OH. 

COOH 

The  phenylosazone  of  d-fructose  is  identical  with  that  of  d-glucose. 

Methylphenylhydrazine  forms  osazones  only  with  ketoses  and  not  with  aldoses,  with 
which,  however,  it  forms  colourless  hydrazones,  these  being  usually  soluble  and  hence 
readily  separable  from  the  slightly  soluble,  intensely  yellow  osazones  (see  pp.  333  and  427). 

1  Caramel  (or  sugar  colouring)  is  prepared  by  fusing  and  heating  glucose  or  saccharose  at  a  temperature  of 
160°  to  200°  (not  beyond  this)  in  an  iron  vessel  fitted  with  a  stirrer.  To  glucose  1  to  3  per  cent,  of  soda  is  also 
added  to  accelerate  the  operation  and  to  neutralise  the  acid  formed  (saccharose  also  yields  acid,  being  first  partly 
inverted  by  the  heating),  and  after  the  change  is  complete,  50  per  cent,  of  hot  water  is  added  and  the  mass  well 
mixed  and  filtered  through  charcoal.  A  brown,  syrupy  mass  is  thus  obtained  which  is  soluble  in  water  or  alcohol, 
giving  a  brown  or  yellow  solution  according  to  the  dilution. 

That  obtained  from  saccharose,  which  does  not  contain  dextrin  and  dissolves  completely  in  80  per  cent, 
alcohol,  is  used  for  colouring  spirits,  whilst  that  from  glucose,  which  contains  dextrin  and  is  entirely  soluble  in 
75  per  cent,  alcohol,  is  used  to  darken  beer  and  vinegar.  The  presence  of  more  than  5  per  cent,  of  ash  indicates 
that  a  caramel  has  been  prepared  from  molasses  ;  good  qualities  contain  only  1  per  cent,  of  ash. 

In  Germany  caramel  is  exempt  from  taxation  and  costs  about  32*.  per  quintal  (for  the  production,  see  above). 


436  ORGANIC    CHEMISTRY 

When  phenylosazones  are  heated  gently  with  hydrochloric  acid,  they  lose  2  mols.  of 
phenylhydrazine  with  formation  of  osones  which  contain  two  carbonyl  groups.  Thus 
phenylglucosazone  yields  Glucosone,  OH-CH2-  [CH-OH]3-CO-CHO,  and  this  when 
treated  with  nascent  hydrogen  (from  zinc  and  acetic  acid)  takes  up  2H  at  the  terminal 
carbon  atom,  fructose  being  thus  obtained  from  glucose.  On  the  other  hand,  reduction  of 
a  ketose  gives  the  corresponding  hexahydric  alcohol,  which,  on  oxidation,  yields  the  mono- 
basic hexonic  acid  ;  the  latter  loses  water,  giving  rise  to  the  laetone,  and  this  gives  the 
a  Idose  on  reduction.  d-Fructose  is  lawo-rotatory  ;  [o]D  =  —92°  at  a  temperature  of  20°. 

This  sugar  has  been  suggested  for  the  use  of  diabetic  and  tuberculous  patients  and  as 
a  substitute  for  cane-sugar,  since  it  is  sweeter,  and  in  syrups  and  honey  it  hinders  the 
crystallisation  of  the  other  sugars. 

In  view  of  these  uses,  attempts  have  been  made  to  prepare  fructose  industrially.  Honig 
in  1895  and  Steiner  in  1908  proposed  its  extraction  from  endive  roots  and  dahlia  tubers 
(these  contain  from  8  per  cent,  to  17  per  cent,  of  inulin).  The  crushed  tubers  are  treated 
in  the  hot  (below  65°)  with  a  little  milk  of  lime  and  with  steam,  and  are  then  pressed.  The 
juice,  after  defecation  with  clay,  is  allowed  to  crystallise  in  a  rotating  cooler,  the  mass  of 
inulin  crystals  being  centrifuged,  redissolved  in  hot  water,  and  converted  into  fructose  by 
means  of  dilute  acid  (see  Glucose)  ;  the  'fructose  solution  is  concentrated  in  a  vacuum. 
Steiner  calculates  that  the  sugar  can  be  made  by  this  process  at  a  cost  of  1  s:  per  kilo. 

A  characteristic  reaction  for  the  detection  of  fructose  in  presence  of  other  reducing 
sugars  is  obtained  with  the  following  solution:  to  a  solution  of  12  grms.  of  glycocoll  in 
hot  water  are  slowly  added  6  grms.  of  pure  cupric  hydrate,  the  liquid  being  heated  on  a 
water-bath  for  about  15  minutes  until  complete  solution  takes  place  and  then  cooled  to 
60°;  after  50  grms.  of  potassium  carbonate  have  been  added,  the  volume  is  made  up  to 
1  litre  and  the  whole  filtered.  This  reagent  is  reduced  in  the  cold  only  by  levulose  (1  to  5 
per  cent,  solution),  the  time  required  varying  from  4  to  9  hours  ;  other  sugars,  including 
the  pentoses,  reduce  it  only  at  temperatures  above  40°. 

d-MANNOSE,  C6H1206,  is  an  aldose  stereoisomeric  with  glucose,  and  is  fermentable  ; 
it  is  obtained  from  mannitol,  the  corresponding  alcohol,  by  oxidation.  It  melts  at  195° 
to  200°,  and  differs  from  other  monoses  in  forming  a  phenylhydra/one  only  slightly  soluble 
in  water.  With  oxidising  agents  it  forms  first  monobasic  d-mannonic  acid  and  then  dibasic 
d-mannosaccharic  acid,  COOH-[CH-OH]4-COOH. 

A  general  method  for  converting  one  hexose  into  a  stereoisomeric  one,  e.g.  d-mannose 
into  d-glucose,  is  as  follows  :  the  d-mannose  is  oxidised  to  d-mannonic  acid  and  the  latter 
dissolved  in  quinoline  and  the  solution  boiled  ;  in  this  way  the  acid  undergoes  partial 
transformation  into  the  stereoisomeric  d-gluconic  acid,  reduction  of  the  lactone  of  which 
yields  d-glucose.  The  reverse  change  of  d-gluconic  into  d-mannonic  acid  is  also  produced 
to  some  extent  by  boiling  with  quinoline,  so  that  d-glucose  can  be  converted  into  d-mannose. 
These  sugars  (and  acids)  differ  only  in  the  space  arrangement  of  the  groups  united  with 
the  asymmetric  carbon  atom  in  the  a-position,  OH'CH2-[CH'OH]3'CH(OH)'CHO,  since 
the  phenylosazone  of  d-mannose  is  identical  with  that  of  d-glucose, 


OH-CH2-  [CH-OH]3-C  -G 

II 
N-NHC6H5 

It  is  this  a-carbon  atom,  adjacent  to  the  aldehyde  group,  which  is  influenced  when  a 
hexonic  acid  is  boiled  with  quinoline  or  pyridine. 

When  glucose,  fructose,  or  mannoseis  treated  with  a  very  dilute  alkali  solution,  a  mixture 
of  all  three  sugars  results.  The  fructose  seems  to  be  an  intermediate  product,  since  the 
dextro-rotation  of  mannose  gradually  changes  to  a  laevo-rotation,  owing  to  formation  of 
fructose,  the  amount  of  the  Isevo-rotation  subsequently  diminishing  as  the  fructose  becomes 
converted  into  glucose. 

Z-MANNOSE  and  Z-GLUCOSE,  C6H12O6  (Aldoses),  are  obtained  together  from  1-arabi- 
nose  by  the  cyanohydrin  synthesis  and  reduction  of  the  lactones  of  the  resulting  acids. 
Application  of  this  synthesis  to  an  aldehyde  yields,  in  general,  two  optically  active  stereo- 
isomerides,  since  a  new  asymmetric  carbon  atom  is  created  and  the  chances  of  formation 
of  the  two  isomerides  are  equal.  But  the  final  mixture  will  be  inactive  only  when  the 
initial  molecule  is  inactive,  while,  when  this  is  optically  active  (as  with  arabinose),  the 
mixture  will  be  active,  as  the  components  will  not  have  equal  and  opposite  activities  ; 


GLUCOSIDES  437 

one  of  these  will  have  a  rotation  greater  than  that  of  the  original  molecule  by  a  certain 
amount  and  the  other  a  rotation  less  by  the  same  amount. 

d-GALACTOSE,  C6H12O6  (Aldose),  is  obtained  by  oxidising  dulcitol,  C6H8(OH)6,  or  by 
hydrolysing  milk-sugar,  in  which  case  it  is  formed  together  with  glucose.  It  melts  at  168°, 
is  fermentable,  and  exhibits  muta-rotation.  It  is  an  aldose,  giving  on  oxidation  first  mono- 
basic d-galactonic  acid  and  then  dibasic  mucic  acid,  COOH-  [CH-OH]4-COOH,  which  is 
inactive. 

HEPTOSES,  OCTOSES,  and  NONOSES  have  not  been  found  in  nature,  but  are 
prepared  synthetically  from  mannose  by  means  of  the  cyanohydrin  synthesis. 

GLUCOSIDES 

These  are  of  frequent  occurrence  in  the  vegetable  kingdom  and,  when 
heated  with  acid  or  alkali  or  subjected  to  the  action  of  certain  enzymes, 
decompose  into  a  glucose  and  an  alcohol  (or  phenol,  aldehyde,  or  nitrogen 
compound)  ;  they  are  hence  ethereal  derivatives  of  the  monoses  (e.g. 
Amygdalin,  Salicin,  Populin,  Coniferin,  &c.). 

Artificial  glucosides  have  been  prepared  by  E.  Fischer  by  the  interaction 
of  an  alcohol  and  a  monose  in  presence  of  hydrochloric  acid  (which  withdraws 
water).  The  glucosides  are  analogous  in  structure  to  the  acetals 


R-  C\      +  2CH3-  OH  =  H20  +  R-  COCHg  (acetal), 
^O  XOCH3 

but  only  1  molecule  of  alcohol  takes  part  in  the  reaction  : 

OH-CH2'CH(OH)-CH(OH)-CH(OH)-CH(OH)-CHO  +  CH3-OH  = 

y  |3  <x 

OH-CH2-CH(OH)-CH-CH(OH)-CH(OH)-CH(OCH3)  +  H20. 


O 


Glucoside 

The  glucosides  are  readily  resolved  into  their  components,  so  that  union  of 
these  directly  through  carbon  atoms  is  excluded.  The  combination  with  the 
oxygen  of  the  hydroxyl  in  the  y-position  is  deduced  from  analogous  reactions, 
such  as  formation  of  lactones.  The  constitution  of  bioses  is  explained 
similarly  (see  later). 

According  to  Auld  (1908)  the  constitution  of  Amygdalin  is  as  follows  : 

— 0— 


OH    H 


OH  H  HOH    H   H 


HC— C— C— 0— C— CH,— 0— C— C— C— C— C— CH,  •  OH. 


HOH  H    H 


0 


OH 


NOCH-C6H5 

Ciamician  and  Ravenna  (1908)  showed  that,  when  glucosides  are  introduced 
into  plants  (maize  and  beans),  they  are  absorbed  and  transformed  without 
producing  any  effect,  whilst  the  decomposition  products  of  the  glucosides 
(benzaldehyde,  salicylic  alcohol,  hydroquinone,  &c.)  act  as  poisons.  Hence 
the  formation  of  glucosides  in  plants  seems  to  have  the  effect  of  paralysing 
the  poisonous  action  of  certain  substances.  The  same  authors  (1909)  found 
that,  when  maize  is  made  to  absorb  saligcniu,  this  is  partly  transformed  into 
its  glucoside,  salicin ;  in  a  similar  manner  they  obtained  benzylglucosidf 
(1911). 


438  ORGANIC    CHEMISTRY 

B.  HEXABIOSES 

Almost  all  of  the  bioses  at  present  known  decompose  into  hexoses  (either 
two  different  monoses  or  2  mols.  of  one  and  the  same  monose).  No  biose  gives 
a  hexose  and  a  pentose. 

This  decomposition  of  bioses,  which  is  known  as  hydrolysis, 

U  12^22^11  +  H20  =  2C6H12O6, 

can  be  effected  by  boiling  with  dilute  acid  or  by  the  action  of  enzymes  ;  and 
since  it  takes  place  with  great  readiness,  it  is  assumed  that  the  constituent 
monoses  of  the  bioses  are  united,  not  between  carbon  atoms,  but  more  probably 
between  oxygen  atoms.  It  would  appear,  however,  that  the  hydrolysis  is  not 
a  unimolecular  reaction  (see  vol.  i,  p.  66). 

Synthetic  bioses  are  obtained  by  treating,  for  instance,  a  hexose  with  acetyl 
chloride,  the  resulting  acetochlorhexose,  in  presence  of  sodium  alkoxide  and  a 
hexose,  giving  the  acetyl  derivative  of  a  biose  ;  elimination  of  the  acetyl  group 
by  means  of  soda  then  yields  the  biose  itself. 

Bioses  may  also  be  obtained  by  the  action  of  certain  enzymes  on  monoses  ; 
thus,  with  maltase,  glucose  gives  isomaltose  (not,  as  was  formerly  thought, 
maltose  ;  see  p.  113).  The  lactase  of  kephir  acts  on  a  mixture  of  glucose  and 
galactose,  giving  isolactose  :  with  glucose  alone  it  yields  a  different  biose. 
Glucose  and  galactose  may  also  be  condensed  by  the  action  of  emulsin  (set 
p.  113). 

Of  the  hexabioses,  maltose,  lactose,  and  saccharose  will  be  considered  (for 
melibiose,  see  later,  under  Raffinose). 

MALTOSE  forms  crystals  of  the  formula  C12H22On  +  H20  and  is  strongly  dextro- 
rotatory. As  was  seen  in  considering  the  manufacture  of  alcohol  and  of  beer,  it  is  prepared 
industrially  from  starch  by  the  action  of  diastase  (see  pp.  Ill,  112). 

Hydrolysis  of  maltose  by  dilute  acid  yields  only  d-glucose.  It  gives  reactions  similar 
to  those  of  the  monoses.  Thus,  it  reduces  Fehlmg's  solution,  and  with  phenylhydrazine 
forms  phenylmaltosazone,  C^HgaOgN^  On  oxidation  it  yields  monobasic  Maltobionic 
Acid,  C12H22O12,  which  gives  d-Gluconic  Acid,  OH-CH2-  [CH  •  OH  ]4-COOH,  on  hydrolysis. 
Hence  maltose  contains  only  one  carbonyl  group  and  not  the  two  corresponding  with  the 
2  constituent  glucose  molecules,  the  phenylosazone  being  formed  with  2,  and  not  4,  mols.  of 
phenylhydrazine,  while  oxidation  of  the  sugar  yields  a  monobasic  and  not  a  dibasic  acid. 
Hence  the  2  mols.  of  glucose  in  the  maltose  molecule  are  joined  in  such  a  way  that  only 
one  carbonyl  group  remains  free  to  exert  its  characteristic  reactions,  the  other  serving  to 
link  up  the  2  glucose  molecules.  It  is  usual  to  include  between  brackets  the  monose  residue 
which  has  no  free  carbonyl  owing  to  the  oxygen  atom  of  this  group  being  joined  to 
the  other  monose  residue,  and  to  place  outside  the  brackets  those  monose  residues 
which  retain  free  carbonyl.  Maltose  would  then  be  represented  by  the  formula 
(C6HnO5'0)  C6HUO5.  Maltose  is  not  fermentable  directly,  the  maltase  of  yeast  first 

d-glucose         d-glucose 
converting  it  into  fermentable  glucose  (see  p.  112). 

Isomaltose  is  not  fermentable. 

LACTOSE  (or  Milk-Sugar),  C12H220U  +  H20,  is  contained  in  milk  (up  to  5  per  cent.) 
and  is  less  sweet  than  cane-sugar.  Its  reactions  are  similar  to  those  of  the  monoses  (reduces 
Fehling's  solution,  &c.),  and  it  yields  d-glucose  and  d-galactosc  on  hydrolysis.  It  does  not 
ferment  with  beer-yeast,  which  contains  no  enzyme  capable  of  hydrolysing  it.  The  glucose 
residue  has  its  carbonyl  free,  whilst  the  carbonyl  of  the  galactose  takes  part  in  the  union 
of  the  2  nionos  emolecules,  so  that  it  will  be  represented  thus  :  (C6H1105'0)  C6HUO5. 

d-galactose        d-glucose 

In  fact,  oxidation  of  lactose  by  means  of  bromine  water  results  in  the  formation  of 
monobasic  lactobionic  acid,  which,  on  hydrolysis,  gives  d-galactose  and  d-gluconic  acid. 

Industrial  Preparation.  Unless  a  dairy  has  an  average  production  of  at  least  60  to  80 
hectols.  of  whey  per  day,  it  is  not  expedient  to  extract  the  milk-sugar.  The  preparation  is 
now  carried  out  as  follows  :  The  whey  is  treated  immediately  after  the  first  coagulation  of 


MANUFACTURE  OF  MILK-SUGAR     439 

the  cheese.1  The  concentration  is  carried  out  in  single  or  double-effect  vacuum  pane, 
similar  to  those  used  in  sugar  factories.  Whey  is  passed  continuously  into  the  concentrator 
until  the  liquid  attains  a  density  of  30°  Be.  in  the  hot  (about  60  per  cent,  of  the  sugar). 
It  is  then  collected  in  iron  vessels  holding  about  700  litres,  in  which  it  is  cooled  by  water 
circulating  through  a  surrounding  jacket.  In  the  course  of  24  hours,  during  which  the 
mass  is  well  stirred  three  or  four  times,  the  temperature  is  lowered  to  20°.  A  pasty  mass 
6f  fine  crystals  then  separates,  with  an  oily  layer  at  its  surface. 

The  crystals  are  separated  by  diluting  the  mass  with  a  little  cold  water  (f )  and  centri- 
fuging,  the  crystals  being  retained  in  the  drum  of  the  centrifuge  by  means  of  a  cloth. 
When  a  sufficient  quantity  of  crystals  has  been  thus  collected  in  the  basket  of  the  centri- 
fuge, the  mass  is  washed  with  a  gentle  spray  of  cold  water,  the  crude,  slightly  yellow  sugar 
thus  obtained  representing  3-6  to  4-3  per  cent,  of  the  whey  taken. 

This  crude  milk-sugar  contains  88  per  cent,  of  sugar  and  12  per  cent,  of  water  and 
various  impurities  (proteins,  &c.).  The  liquid  from  the  centrifuge  still  contains  about 
30  per  cent,  of  the  total  sugar  (not  crystallised  but  forming  a  syrup).  This  liquid,  which 
usually  has  a  density  of  about  15°  Be.,  is  heated  to  boiling  by  direct  steam  in  a  vessel 
with  a  flat,  perforated  false  bottom,  the  albumin  being  thus  coagulated.  After  half  an 
hour's  rest,  the  albumin  collects  as  a  compact  layer  at  the  surface,  the  liquid  being  then 
drawn  off  from  below  so  as  to  leave  the  cake  of  albumin  on  the  false  bottom  ;  this  is 
removed,  pressed  in  bags,  and  given  to  pigs  or  mixed  with  white  flour  to  make  bread.  The 
albumin-free  liquid  is  concentrated  in  vacuum  pans  to  35°  Be.  (measured  in  the  hot)  and 
allowed  to  cool  for  several  days,  with  occasional  stirring,  in  iron  vessels.  This  procedure 
yields  a  dark  pasty  mass  of  the  crystalline  sugar,  which  is  collected  by  diluting  with  a 
large  quantity  of  cold  water  and  centrifuging  as  before  ;  this  sugar  amounts  to  0-3  to  0-7 
per  cent,  of  the  original  quantity  of  whey. 

The  mean  yield  of  crude  milk-sugar  is  4-3  per  cent,  of  the  whey  (the  maximum  of  4-8 
per  cent,  being  obtained  in  winter  and  the  minimum  of  3-9  per  cent,  in  summer). 

The  liquid  from  the  second  crystallisation  and  centrifugation  is  not  treated  further, 
unless  by  osmosis  ;  it  is  preferably  utilised  as  cattle-food,  as  it  is  rich  in  potassium  salts, 
nitrogen,  and  phosphoric  acid. 

The  crude  sugar  is  either  dried  and  placed  on  the  market  or  subjected  to  a  refining 
process.  If  left  in  heaps,  it  deteriorates  to  some  extent. 

The  refining  is  carried  out  as  follows :  The  sugar  is  dissolved,  in  an  open  boiler  with  a 
double  bottom  (heated  by  indirect-fire  heat),  in  water  at  50°,  the  liquid  being  well  stirred 
so  as  to  obtain  a  solution  of  13°  to  15°  Be.  (24  to  27  per  cent,  of  sugar).  A  little  bone-black 
and  about  0-2  per  cent,  (on  the  weight  of  sugar)  of  acetic  acid  are  then  added,  and  the 
heating  continued  until  the  boiling-point  is  approached,  when  magnesium  sulphate  (about 
0\2  per  cent.)  is  added  and  the  liquid  subsequently  kept  boiling  for  a  few  minutes.  The 
mass  suddenly  froths  very  considerably  (if  necessary,  the  steam-cock  is  closed  ;  the  boiler 
should  not  be  too  full  initially)  and  the  temperature  rises  to  105°.  The  charcoal  decolorises 
the  liquid  and  absorbs  unpleasant  flavouring  substances,  while  the  albumin  is  coagulated 
in  large  flocculent  masses  (by  the  acetic  acid)  and  the  phosphoric  acid  is  precipitated  by 
the  magnesium.  The  hot  liquid  is  filter-pressed,  and  the  solid  residue,  after  being  washed 
with  water  and  treated  with  a  suitable  amount  of  sulphuric  acid,  constitutes  an  excellent 
nitrogenous  superphosphate.  The  clear  liquid  from  the  filter -press  is  concentrated  as 
usual  in  vacua  to  35°  Be.  in  the  hot  (65  per  cent,  of  sugar),  the  formation  of  froth  being 
prevented.  It  is  then  crystallised,  and  when  the  maximum  quantity  of  crystals  has  sepa- 
rated, these  are  separated  by  centrifuging,  giving  first  product.  After  subsequent  concen- 
trations of  the  mother-liquor,  second  and  third  products  are  obtained.  These  three  products 
together  amount  to  about  3  to  3-5  per  cent,  of  the  original  quantity  of  whey  ;  they  may 
be  kept  separate  or  mixed  and  then  recrystallised. 

To  obtain  the  sugar  in  the  very  white  powdery  form  in  which  it  is  now  fold,  the  refined 
product  (first,  second,  or  third)  is  dissolved  in  hot  water  to  give  a  solution  of  15°  Be.,  which 
is  boiled  and,  after  a  little  aluminium  sulphate  (0-1  per  cent.)  has  been  added,  filter-pressed, 
the  clear  watery  filtrate  being  concentrated  to  32°  Be.  It  is  then  crystallised  in  copper 
vessels,  centrifuged,  and  dried  in  revolving  inclined  drums  round  which  hot  water  passes. 

It  is  dry  when  it  no  longer  adheres  on  compressing  between  the  hands.   The  cold  sugar 

1    Dairies  not  producing  sufficient  whey  simply  purify  it  by  boiling  with  acid  whey  to  coagulate  the  albumin 
and  filtering.    It  is  then  despatched  to  works  which  treat  it  further. 


440  ORGAN  1C    CHEMISTRY 

is  ground  and  sieved  to  an  impalpable  powder.  The  average  yield  over  the  whole  year 
is  2-5  kilos  of  the  powdered  sugar  per  100  litres  of  whey.  This  powder  should  be  left  in 
open  vessels  for  some  days,  as,  if  packed  immediately,  it  develops  an  unpleasant  smell 
(which,  however,  it  loses  if  spread  out  in  the  air). 

To  obtain  the  sugar  in  masses  of  aggregated  crystals,  solutions  of  the  gravity  21°  to  24° 
Be.  are  crystallised  in  wooden  vessels  containing  numbers  of  small  wcoden  rods  ;  the 
crystallisation  sometimes  occupies  as  much  as  a  fortnight,  and  a  liquid  of  13°  Be.  remains 
which  can  be  concentrated  anew. 

The  albumin  separated  when  whey  is  boiled  contains,  after  pressing,  about  60  per  cent, 
of  water  and  40  per  cent,  of  dry  matter  composed  of  17  per  cent,  of  protein  substances, 
11  per  cent,  of  milk-sugar,  2-3  per  cent,  of  fat,  5  per  cent,  of  ash  (one-half  of  which  is 
insoluble  in  water),  and  1-7  per  cent,  of  lactic  acid. 

The  final  mother -liquor,  or  lactose  molasses,  is  brownish  black,  and  contains  about 
73  per  cent,  of  water,  6  per  cent,  of  ash  (two-thirds  soluble  in  water),  0-10  per  cent,  of  fat, 
0-6  per  cent,  of  nitrogen,  1-5  per  cent,  of  acid  (calculated  as  lactic  acid),  and  22-5  per  cent, 
of  substances  which  reduce  Fehling's  solution  (calculated  as  milk-sugar). 

The  milk-sugar  industry  has  undergone  considerable  development  in  Italy  during 
recent  years,  the  exports  increasing  from  446  quintals  (£1516)  in  1903  to  3087  quintals 
(£11,113)  in  1905,  and  then  falling  to  137  quintals  in  1910. 

In  1905  Germany  imported  2800  quintals  (£13,300)  and  exported  5485  quintals 
(£28,800),  while  in  1909  the  imports  were  only  135  and  the  exports  1650  quintals. 

The  price  varies  from  68*.  to  96s.  per  quintal. 

Tests  for  Milk-Sugar.  Adulteration  with  mineral  substances  is  recognised  by  the  ash 
exceeding  1  per  cent,  in  amount.  When  dextrin  is  present,  this  does  not  dissolve  in  alcohol, 
while  the  presence  of  glucose  or  saccharose  (even  as  little  as  2  per  cent.)  is  indicated  by 
evolution  of  carbon  dioxide  from  a  10  per  cent,  solution  of  the  sugar  mixed  with  a  little 
fresh  beer-yeast  and  kept  at  20°  to  30°  for  2  days  ;  the  invertase  present  in  the  yeast 
inverts  the  saccharose,  which  then  ferments,  but  it  does  not  break  down  the  lactose,  which 
consequently  does  not  ferment.  It  is  also  found  that  when  the  Bulgarian  ferment  (Bac- 
terium bulgaricum)  acts  on  a  mixture  of  saccharose  and  lactose,  the  latter  alone  is  destroyed. 

SACCHAROSE  (Sucrose,  Cane-sugar),  C12H220U 

Saccharose  may  be  regarded  chemically  as  the  condensation  product  of 
two  hexamonoses,  glucose  and  fructose,  which  are  generated  by  hydrolysis 
with  dilute  acid.  The  characteristic  reactions  of  the  monoses  are  lacking  in 
saccharose,  which  does  not  reduce  Fehling's  solution,  form  osazones,  or  turn 
brown  when  treated  with  caustic  soda  solutions.  It  must  therefore  be  assumed 
that  the  saccharose  molecule  contains  no  free  carbonyl  group  (aldehydic  or 
ketonic),  the  two  such  groups  in  the  two  monoses  being  annulled  in  the  con- 
densation. This  is  seen  clearly  from  the  following  equation,  in  which  a  con- 
stitutional formula  with  the  lactonic  groupings  so  common  to  these  substances 
(see  p.  428)  is  attributed  to  saccharose  : 


-o- 


OH'CH2-CH(OH)-CH-CH(OH)-CH(OH)-CH 

O  4-  H-OH  = 

I-C-G] 


OH-CH2-CH-CH(OH)-CH(OH)-C-CH2-OH 


Saccharose 


OH-CH2-[CH-OH]4-C<^   +  OH-CH2-[CH-OH]3-CO-CH2  OH. 

Glucose  H  Fructose 


SACCHAROSE  441 

The  rational  formula  (see  Maltose)  of  saccharose  will  hence  be  : 

(C6HU06-O.C6HU06). 

Saccharose  and  the  bioses  generally  are  not  changed  by  the  direct  action 
of  alcoholic  ferments  or  of  the  majority  of  enzymes,  so  that  they  cannot  be 
converted  immediately  into  alcohol  and  carbon  dioxide,  as  is  the  case  with  the 
hexoses.  In  order  that  alcoholic  fermentation  of  cane-sugar  may  take  place, 
it  is  necessary  that  the  sugar  should  be  first  inverted  by  the  invertase — almost 
always  present  in  yeasts — into  fermentable  glucose  and  fructose.  Hence, 
yeasts  which  contain  no  invertase.  cannot  ferment  saccharose.  Saccharomyces 
octosporus,  for  instance,  leaves  this  sugar  unchanged,  although  it  ferments 
maltose,  owing  to  the  presence  of  maltase,  which,  hydrolyses  the  maltose  to 
glucose. 

It  has  already  been  mentioned  that  saccharose  is  readily  hydrolysed  by 
heating  with  a  minimal  quantity  of  a  dilute  mineral  acid,  and  that  this  hydro- 
lysis is  known  as  inversion  (see  p.  433)  because  the  dextro-rotatory  saccharose 
([a]D  =  -f  66-5°)  is  changed  into  a  Isevo -rotatory  mixture  of  equal  proportions 
of  glucose  and  fructose  (invert  sugar}.  The  velocity  of  inversion,  s,  is  proportional 
to  the  amount  of  cane-sugar  present  in  the  solution  at  any  moment,  and  is 
hence  expressed  by  s  =  k  (p  —  x),  where  p  is  the  quantity  of  the  original  sugar 
and  x  that  which  has  already  undergone  inversion.  The  inversion  constant,  k, 
varies  with  the  nature  of  the  acid  employed  and  is  proportional  to  the  degree 
of  electrolytic  dissociation  of  the  acid,  the  rate  of  inversion  increasing  with 
the  number  of  free  hydrogen  ions.  It  is,  indeed,  possible  to  determine  the 
ionic  concentration  of  an  acid  solution  by  means  of  the  velocity  of  inversion, 
or  the  amount  of  reducing  sugar  formed  in  unit  time,  in  a  saccharose  solution 
of  definite  concentration.  In  the  cold,  sulphurous  and  carbonic  acids  have 
scarcely  any  inverting  power. 

Saccharose  melts  at  160°  and,  on  solidification,  forms  an  opaque,  amor- 
phous, glassy  mass,  which  then  crystallises  in  inclined  monoclinic  or  rhombic 
prisms  with  blunted  angles  ;  at  a  higher  temperature  it  caramelises  to  a 
brown  mass  with  evolution  of  gas  (see  p.  435).  It  has  the  sp.  gr.  1-5813. 

One  part  of  water  dissolves  2-5  parts  of  saccharose  at  0°  and  4-5  parts  at 
100°.  It  is  almost  insoluble  in  absolute  alcohol  or  ether,  but  dissolves  slightly 
in  methyl  alcohol.  It  readily  forms  supersaturated  aqueous  solutions,  which 
then  rapidly  deposit  anhydrous  crystals  ;  this  phenomenon  is  utilised  in  its 
industrial  preparation. 

Cane-sugar  forms  compounds  (sucrates)  with  inorganic  bases  ;  thus,  with 
lime  it  forms  (1)  Monocalcium  Sucrate,  C12H220n,  CaO,  2H20,  soluble  in 
water,  (2)  Dicalcium  Sucrate,  C12H22OU,  2CaO,  also  moderately  soluble 
in  water,  and,  on  heating  a  solution  of  either  of  these  compounds, 
(3)  Tricalcium  Sucrate,  C12H220U,  3CaO,  3H20,  insoluble  in  water. 

The  manufacture  of  cane-sugar  is  described  later. 

A  sensitive  reaction  for  the  detection  of  small  quantities  of  sugar  is  indi- 
cated on  p.  447. 

Pozzi-Escot  (1909)  has  devised  a  still  more  sensitive  reaction  for  the  sugars  :  into 
a  test-tube  are  introduced  2  c.c.  of  the  aqueous  solution,  1  c.c.  of  5  per  cent,  ammonium 
molybdate  solution  and,  after  mixing,  10  to  12  c.c.  of  concentrated  sulphuric  acid,  which 
is  poured  carefully  down  the  side  of  the  tube.  The  formation  of  a  blue  ring  within  20 
minutes  indicates  the  presence  of  more  than  0-0005  per  cent,  of  sugar  ;  and  if  the  blue  ring 
appears  within  30  minutes  when  the  upper  part  of  the  liquid  is  heated  to  boiling,  the 
solution  contains  at  least  0-00002  per  cent,  of  sugar. 


442  ORGANIC    CHEMISTRY 

C.  TRIOSES 

RAFFINOSE,  C18H32O16  +  5H20,  forms  pointed  crystals  and  has  a  very 
high  rotatory  power  ([a]^0  =  +  104-5°),  and  since  also  saccharose  containing 
raffinose  exhibits  pointed  crystals  and  an  increased  rotation,  raffinose  is  known 
in  Germany  as  Spitzenzucker  or  Pluszucker.  It  is  a  hexatriose,  and  when  hydro- 
lysed  takes  up  2H20,  giving  equal  proportions  of  d-glucose,  d-fructose,  and 
d-galactose.  By  restricting  the  hydrolysis,  most  suitably  by  effecting  it  with 
enzymes,  an  intermediate  stage  may  be  realised,  consisting  of  d-fructose  and 
melibiose  (isomeric  with  lactose),  which  is  subsequently  resolved  into  d-glucose 
and  d-galactose.  Raffinose  is  found  together  with  cane-sugar  in  the  sugar-beet, 
its  amount  varying  with  the  season.  In  the  manufacture  of  saccharose,  it 
accumulates  in  the  molasses  and  often  occurs  abundantly  in  the  sugar  extracted 
from  beet -molasses  by  the  strontia  process  ;  in  the  final  syrup  from  this  treat- 
ment it  occurs  sometimes  to  the  extent  of  20  per  cent.  Raffinose  does  not  give 
the  reactions  of  the  monoses  (reduction  of  Fehling's  solution,  &c.),  and  hence 
contains  no  carbonyl  group,  its  rational  formula  being 

(C6Hn05-  0)-  (C6H1004-  0-  C6Hn05)- 

•Galactose  Glucose  Fructose 

Melibiose,  which,  like  lactose,  exhibits  the  reactions  of  the  monoses  and  contains 
a  carbonyl  group,  is  represented  thus  :  (C6HU05'  0)  •  C6HU05.  So  that  raffinose 

Galactose  Glucose 

usually  decomposes  first  at  the  point  where  a  carbonyl  group  occurs  (between 
glucose  and  fructose)  ;  otherwise  it  would  yield  a  biose  without  a  free  car- 
bonyl group.  Recently,  indeed,  Neuberg  (1907)  has  shown  that  the  action  of 
emulsin  on  raffinose  gives  galactose  and  cane-sugar  (which  does  not  give  the 
monose  reactions),  this  decomposition  thus  occurring  at  the  opposite  end  of 
the  molecule.  This  observation  supports  Herzf eld's  hypothesis  that  in  the 
beet  raffinose  is  formed  from  saccharose  and  galactose,  the  latter  originating 
in  the  decomposition  of  pectic  substances,  possibly  by  the  action  of  an  anti- 
emulsin. 

In  presence  of  saccharose  and  invert  sugar,  raffinose  may  be  determined  quantitatively 
by  the  optical  method  described  later  (Saccharimetry),  or  by  the  method  devised  by  Ofner 
(1907),  who  extracts  the  whole  of  the  raffinose  with  pure  methyl  alcohol,  evaporates  the 
alcohol,  hydrolyses  the  remaining  syrup  for  3  hours  on  the  water-bath  with  3  per  cent, 
sulphuric  acid,  and  then  precipitates  the  galactose  as  metliylphenylhydrazone,  which  is 
quite  insoluble  and  can  be  easily  weighed  ;  the  corresponding  weight  of  raffinose  can  then 
be  calculated.  An  exact  determination  of  raffinose  in  sugar,  which  almost  always  contains 
less  than  0-5  per  cent,  of  it,  is  very  difficult.  The  presence  of  raffinose  in  small  propor- 
tion in  saccharose  is  regarded  as  probable  if  the  ratio  between  non-sugar  and  ash  is  less 
than  1-5. 

INDUSTRIAL  PREPARATION  OF  SACCHAROSE1 

Saccharose  is  contained  in  varying  quantity  (5  to  20  per  cent.)  in  different 
vegetable  organisms.  For  instance,  the  sugar-cane  (Saccharum  officinarum) 
gives  15  to  20  per  cent. ;  the  beetroot  (Beta  vulgaris),  7  to  17  per  cent.  ;  Sorghum 

1  History  of  Beet-sugar.  The  first  saccharine  material  worked  and  utilised  by  man  as  food  was  probably 
honey.  The  sugar-cane  was  known  to  the  ancient  Chinese,  the  Indians,  and  also  the  Persians  and  Arabs  two 
hundred  years  before  Christ  and  only  later  was  it  introduced  into  Egypt,  Greece,  and  Sicily ;  the  medicine-men 
of  this  epoch  employed  cane-juice  and  honey  as  medicine.  In  the  seventh  century  sugar  in  the  solid  form  was  an 
article  of  commerce,  and  in  the  eighth  century  the  Persians  extracted  it  from  the  sugar-cane  and  prepared  it  in 
cakes  ;  after  the  ninth  century,  the  cultivation  of  the  cane  was  extended  by  the  Arabs  to  Egypt,  Syria,  Crete. 
Sicily,  and  Spain.  In  the  fifteenth  century,  the  Portuguese  introduced  the  culture  into  Madeira  and  Brazil,  while 
the  Spaniards  carried  it  to  the  East  Indies  and  the  Canary  Islands,  and  the  Dutch  to  Java  and  Guiana.  At  the 
present  time  the  sugar-cane  is  largely  cultivated  in  Cuba,  Java,  Manila,  Martinique,  Jamaica,  Louisiana,- Brazil, 
Peru,  China,  Japan,  India,  Egypt,  and  part'of  Australasia.  In  Europe  it  is  grown  to  a  small  extent  only  in  Spain. 

In  1806,  when  France  and  the  allied  nations  established  the  Continental  blockade  against  England  (lasting 


SOURCES    OF    CANE-SUGAR  443 

saccharatum,  7  to  12  per  cent.  ;    the  pineapple,  11  per  cent.  ;    strawberries, 

5  to  6  per  cent.  ;  maize  stems,  sugar  maple,  &c.,  also  contain  small  proportions 
of  saccharose.    Most  sweet  vegetable  juices,  however,  contain  glucose  (grape- 
sugar)  and  levulose.    The  plants  employed  industrially  for  the  extraction  of 
sugar  are  the  maple,  sugar-cane,  and  beetroot.     Unsuccessful  attempts  have 
been  made  with  maize  stems,  which  contain  as  much  as  14  per  cent,  of  sugar 
when  the  unripe  heads  are  cut  ;    but  the  sugar  extracted  sometimes  contains 
12  per  cent,  of  invert  sugar  and  other  impurities. 

I.  ACER  SACCHARINUM  NIGRUM  (Sugar  Maple),  which  is  largely  cultivated  in 
North  America,  is  a  tree  requiring  about  20  years  to  attain  its  maximum  height  of  more 
than  9  metres  and  diameter  of  bole  of  80  cm.     In  February,  March,  and  April,  three  holes  are 
made  at  different  points  (east,  south,  and  west)  with  an  iron  borer ;  these  holes  penetrate 
to  a  depth  of  1  cm.,  so  as  to  pierce  the  bark,  and  are  about  40  cm.  from  the  ground.     Into 
each  hole  is  placed  a  hollow  elder  stem,  which  discharges  the  juice  during  a  period  of  5  to 

6  weeks.     The  following  year  the  holes  are  made  on  the  other  side  of  the  trunk.     In  this 
way  a  maple  yields  120  to  130  litres  of  juice  containing  about  3  kilos  of  sugar.     The  juice 
must  be  worked  up  each  day,  as  it  soon  undergoes  alteration  ;   the  method  of  treatment 
is  similar  to  that  used  with  beet-juice. 

In  1880  North  America  produced  54,000  quintals  of  maple-sugar,  while  in  1904  the 
output  amounted  to  120,000  quintals. 

II.  THE  SUGAR-CANE  is  the  principal  source  of  Colonial  sugar. 

It  is  a  plant  (Saccharum  officinarum,  Fig.  286)  which  has  been  cultivated  from  the 
most  remote  times  in  India,  Persia,  and  Arabia,  whence  it  passed  into  Egypt  and  Greece, 
At  the  time  of  the  Normans  it  was  cultivated  in  Sicily,  and  from  there  it  was  introduced 
in  1420  into  Portugal  and  Spain,  and  thence  into  the  West.  Indies  ;  the  Dutch  carried  it 
to  the  East  Indies,  where  its  development  was  very  rapid.  At  the  present  time  it  is  culti- 
vated most  widely  in  Cuba,  Porto  Rico,  San  Domingo,  Havana,  Brazil,  and  the  East 
Indies  (Bengal,  Java,  and  the  Philippines).  In  Mexico  450  quintals  of  cane  per  hectare  are 
obtained,  but  the  culture  is  primitive  and  the  industry  rudimentary.  In  Java  a  hectare 
of  land  yielded  680  quintals  of  cane  in  1893  and  an  average  of  more  than  1020  quintals  in 
1910.  At  Hawaii  the  yield  was  600  quintals  in  1895  and  835  in  1910.  At  Cuba  as  much 
as  1250  quintals  per  hectare  are  obtained,  but  even  this  amount,  and  also  the  10  per  cent, 
yield  of  sugar,  might  be  still  further  increased. 

The  plantations  are  made  with  shoots  from  the  living  plant  (obtained  from  seed), 
these  being  placed  about  1  metre  apart  and  weeded  after  4  to  5  months.  The  cane  begins 

Until  1814)  and  the  supply  of  colonial  sugar  furnished  by  England  to  the  whole  of  Europe  hence  failed,  attempts 
were  made  to  discover  a  substitute  for  cane-sugar. 

As  early  as  1705  the  French  agriculturist,  Olivier  de  Scrres,  had  observed  that  the  beet  contained  a  consider- 
able proportion  of  sugar,  and  in  1747  the  Berlin  pharmacist,  Sigismund  Marggraf,  attempted  the  extraction  of 
the  sugar,  obtaining  a  yield  of  6  per  cent. ;  but  at  that  time  it  could  not  compete  with  the  much  cheaper  colonial 
sugar.  Carl  Achard,  a  pupil  of  Marggraf,  after  twenty  years  of  experimental  work  ou  the  selection  of  the  best 
qualities  of  beet,  Ac.,  erected  a  factory  for  the  manufacture  of  beet-sugar  at  Kunern,  in  Silesia  (1801).  But  it 
was  not  found  possible  to  extract  more  than  3  per  cent,  of  crystalline  sugar,  which  did  not  cover  the  expenses, 
so  that  the  factory  was  closed.  Achard,  however,  continued  to  perfect  his  process,  and  when  the  Continental 
blockade  produced  in  1811  a  tenfold  increase  in  the  price  of  sugar,  several  beet-sugar  factories  were  started  in 
Germany  ;  but  these  were  still  so  imperfect  that  they  were  obliged  to  suspend  operations  when  the  blockade 
ceased.  At  this  same  time  Napoleon  I  induced  the  most  eminent  scientific  and  technical  men  in  France  to  apply 
themselves  to  this  problem,  and  the  extraction  processes  were  rapidly  improved,  machines  being  devised  for 
rasping  and  pressing  the  beets.  With  the  introduction  of  the  use  of  steam  for  concentrating  the  juices  and 
of  granulated  bone-black  for  decoloration,  beet-sugar  began  to  compete  seriously  with  colonial  sugar,  even 
after  the  raising  of  the  blockade.  In  1828  there  were  indeed  58  large  and  flourishing  factories  in  France, 
producing  annually  300,000  quintals  of  sugar.  Napoleon  I  had  distributed  in  prizes  to  encourage  this  industry 
the  sum  of  £40,000  and  had  himself  erected  four  factories  and  brought  32,000  hectares  of  land  under  beet 
cultivation. 

In  Germany  the  sugar  industry  was  started  again  in  about  1836,  especially  in  the  neighbourhood  of  Mag- 
deburg, where  a  fortunate  choice  was  made  in  the  quality  of  beet  employed,  the  lot  of  the  agriculturist — at  that 
tiirfe  depressed  owing  to  poor  grain  crops — being  thus  greatly  ameliorated.  The  further  development  of  this 
industry  was  favoured  by  protective  duties  imposed  by  the  Government,  in  France — until  a  few  years  ago — 
and  in  Germany  and  Austria,  where  the  prosperity  of  the  sugar  factories  is  continually  increasing.  The  industry 
then  developed  in  Belgium  and  Russia,  while  in  Italy  it  was  initiated  only  towards  the  end  of  the  last  century. 
In  England  the  cultivation  of  the  sugar-beet  has  been  attempted,  apparently  with  success,  on  a  small  scale  only 
during  recent  years. 

In  1855  the  world's  production  of  beet-sugar  already  amounted  to  1,500,000  tons,  and  in  1900  Central  Europe 
alone  produced  8,500,000  tons.  During  the  same  lapse  of  time  the  output  of  cane-sugar  increased  only  from 
1J  to  2J  millions  of  tons. 


444 


ORGANIC    CHEMISTRY 


to  sprout  in  12  months  and  requires  a  further  6  months  to  mature,  when  it  has  a  yellowish 
colour  and  is  3  to  6  metres  high  and  4  to  6  cm.  in  diameter  ;  it  sometimes  reaches  a  weight 
of  9  kilos. 

The  stem  and  roots  of  each  plant  will  yield  cane  for  twenty  consecutive  years  without 
renewal.  The  negro  labourers  remove  the  head  (used  for  cattle-food)  from  the  cane  with 
a  blow  from  a  scythe,  and  with  another  sever  the  cane  at  the  base  ;  the  leaves  (used  for 
thatching)  are  then  removed  and  the  cane  worked  up  each  day,  as  it  rapidly  ferments  if 
left  in  heaps.  The  omnivorous  ant  is  the  enemy  most  feared  by  the  planter.  At  one  time 
the  bundles  of  cane  were  crushed  in  a  primitive  mill  formed  of  three  vertical  cylindrical 

tree-trunks,  shod  with  iron  and 
worked  by  water-wheels  or  horses. 
But  nowadays  use  is  made  of  three 
horizontal  cylinders,  the  distances 
between  which  can  be  regulated  so 
as  to  vary  the  pressure  (Fig.  287). 

The  liquid  thus  expressed  is 
termed  raw  juice,  and  the  woody 
residue  bagasse  or  megass.  After 
the  cane  has  been  pressed,  it  is 
moistened  with  water  and  again 
pressed  (it  contains  then  4  per 
cent,  of  sugar  and  45  per  cent,  of 
water),  and  then  dried  and  burnt 
as  fuel.  In  Mexico  bagasse  and 
the  leaves  of  Henequen  plants  are 
now  used  for  the  manufacture  of 
spirit.  The  total  juice,  including 
that  from  the  second  pressing, 
forms  about  90  per  cent,  of  the 
weight  of  the  cane  and  contains 
15  to  19  per  cent,  of  sugar.  In 
the  East  Indies,  owing  to  irrational 
methods  of  working,  more  than 
one-half  of  the  sugar  is  lost,  whilst 
in  Brazil,  where  improved  pro- 
cesses are  in  use,  more  than  60  per 
cent,  of  pure  sugar  is  obtained.1 
In  North  America  the  diffusion 
process  has  been  introduced,  and 
the  loss  of  sugar  reduced  to  less 
than  20  per  cent.  ;  diffusion  has 
FIG.  286.  also  been  tried  in  Brazil,  but  was 

abandoned  owing  to   its  expense, 

especially  as  regards  fuel.  Treatment  of  the  fresh  juice  with  a  considerable  amount  of 
sulphur  dioxide  is  often  employed  to  prevent  the  ready  fermentation  which  otheiwke 
occurs.  Attempts  have  also  been  made  to  decolorise  with  sodium  hydrobulphite. 

1  The  following  information  has  been  furnished  by  Alberto  Bianchi,  who  has  visited  various  cane-sugar  factories 
in  South  America.  The  most  important  centres  in  South  America  for  the  production  of  the  sugar-cane  are :  in 
Brazil,  the  States  of  Pernambuco,  Bahia,  Rio  de  Janeiro,  and  San  Paulo,  and,  in  a  less  degree,  Maceio  and 
Maranhao  ;  in  Argentine,  much  cane-sugar  is  produced  in  the  northern  provinces,  especially  in  Tucuman.  The 
varieties  of  cane  most  widely  grown  in  Brazil  are  cana  manteiga  and  cana  pretu,  which  have  been  imported 
from  Java  and  Haiti  and  yield  from  10  to  17  per  cent,  of  crystallisable  sugar.  The  works  arc  erected  in  (ho 
plantations,  and  the  more  primitive  ones,  in  which  the  juice  is  still  concentrated  under  the  ordinary  pressure, 
arc  called  Engenhos,  whilst  those  furnished  with  modern  machinery  and  multiple-effect  vacuum  plant  are  termed 
L 'sinus. 

In  the  Engexhos,  the  broken  cane  is  crushed  between  wooden  roHers  worked  by  oxen  or  horses.  When  the 
juice  is  not  defecated,  it  is  concentrated  in  large  copper  pans  heated  by  direct  fire,  and  is  then  left  to  crystallise 
in  wooden  vessels,  the  molasses  being  subsequently  decanted  off  and  the  crystalline  mass  placed  to  drain  in  barrels 
with  perforated  bottoms.  When  defecation  is  employed,  the  juice  is  boiled  with  lime  and  skimmed  several  times, 
the  defecated  juice  then  passing  into  a  series  of  two  or  three  pans,  each  lower  than  the  preceding  one  ;  in  the 
lust  of  these  the  desired  concentration  is  attained.  The  sugar  thus  obtained  is  always  moist,  owing  to  the  residual 
molasses,  and  varies  in  colour  from  yellow  to  brownish  black  ;  the  yield  is  less  than  6  per  cent. 

In  the  I' sinus,  whore  the  yield  may  amount  to  10  to  11  per  cent,  (by  the  wet  process,  or  7  to  9  per  cent,  by 
the  dry  process,  or  6  per  cent,  when  the  cane  is  pressed  in  a  single  pair  of  rolls),  the  canes  are  pressed  between 


BEETROOT 


445 


Even  recently  cane-sugar  constituted  about  one-half  of  the  total  sugar  produced,  but 
it  is  nearly  all  consumed  where  grown  in  a  more  or  less  refined  condition,  whilst  a  very 
large  trade  is  done  in  beet-sugar  in  a  highly  refined  form,  and  in  some  cases  this  sugar 
competes  with  cane-sugar  in  districts  where  the  latter  is  produced.  The  output  of  cane- 
sugar  in  Cuba  alone  was  700,000  tons  in  1898  and  1,050,000  in  1904.  In  order  to  encourage 
the  cultivation  of  the  sugar-cane,  the  United  States  Government  have  instituted  a  system 
of  bounties  (as  much  as  ILs.  per  quintal),  and  in  1910  paid  £13,800,000  in  this  way  ;  in 
addition  to  this  there  is  a  protective  duty  of  24s.  per  quintal  on  the  sugar,  this  being  paid 
by  the  consumer.  In  the  East  Indies  the  production  increased  to  2,16(5,000  tons  in  1904. 
(The  European  output  of  beet-sugar  is  about  8,000,000  tons  per  annum.) 

Cane-sugar  molasses  is  of  value  owing  to  its  agreeable  flavour  and  smell,  and  it  is 
therefore  converted,  by  fermentation  and  distillation,  into  rum,  that  of  Jamaica  being 
especially  renowned. 

III.  The  BEETROOT  was  formerly  an  annual,  but  became  changed  by  selection  into 
a  biennial,  giving  flowers  and  fruit  (or  seeds)  only  in  the  second  year.  Different  varieties  of 
Beta  vulgaris  or  Beta  maritima 
(Linnaeus)  are  now  grown.  The 
original  wild  varieties  contained  only 
5  to  6  per  cent,  of  sugar,  but  after 
careful  and  repeated  selection  during 
a  period  of  25  years,  varieties  have 
been  obtained  which,  under  the  most 
favourable  conditions,  contain  as 
much  as  1 8  per  cent,  of  sugar.1 

Nearly  all  of  the  best  varieties 
now  cultivated  are  derived  from  the 
Klein-Wanzleben.  The  shape  of  the 
root  is  of  considerable  importance. 
Thus,  the  rounder  beets  are  generally 
rich  in  sugar  but  give  a  small  crop  ; 
roots  of  oblong  and  swollen  form 
crop  well  but  are  poor  in  sugar  ; 
whilst  fusiform  roots  which  are  not  J?IG.  287. 

too  smooth  and  have  little  top  and 

three  pairs  of  double  rollers  by  hydraulic  pressure,  poorer  juice  (wet  process)  being  gradually  sprayed  on  to  the 
partially  pressed  cane ;  the  pressed  cane  is  used  as  fuel.  The  juice,  with  a  density  of  5°  to  10°  B6.,  is  pumped 
to  the  sulphitation  tanks  (sulphur  dioxide  or  calcium  bisulphite  is  used  ;  but  this  is  not  done  in  all  factories)  and 
thence  passes  to  copper  vessels  with  spherical  bottoms  and  holding  2000  to  4000  litres.  In  these  it  is  defecated 
with  milk  of  lime,  being  heated  by  steam  coils  and  skimmed  once  or  twice.  After  carbonation,  the  juice  is  trans- 
ferred to  other  vessels  of  about  the  same  size  as  the  former  ones  and  placed  at  a  lower  level ;  in  these  it  is  again 
boiled  and  skimmed.  It  is  next  removed  to  the  depositing  tanks  and,  after  some  hours,  is  pumped  to  the  triple 
effect  vacuum  concentrators,  from  which  it  passes  at  23°  to  26°  B6.  to  copper  boilers'of  2000  to  4000  litres  capacity 
(clariflers),  where  it  is  boiled  by  means  of  steam  coils  for  about  half  an  hour — until  it  ceases  to  form  scum  (which 
is  removed).  The  juice  is  next  boiled  in  a  vacuum  apparatus,  In  which  crystallisation  commences  ;  the  subse- 
quent treatment  and  refining  of  the  sugar  are  carried  out  as  in  beet-sugar  factories  (see  later). 

In  many  factories,  the  yield  of  white,  first-jet  sugar  is  increased  by  decolorising  the  juice,  not  by  sulphitation, 
but  by  the  addition  of  blankite  (sodium  hydrosulphite)  in  the  proportion  of  300  to  500  grins,  per  ton  of  sugar ; 
this  is  added  partly  to  the  clarifler  and  partly  to  the  concentration  vessel. 

It  is  calculated  that  the  cost  price  of  cane-sugar  in  the  factory,  without  reckoning  interest  on  capital,,  is  15«. 
per  quintal  in  Java,  18s.  in  Cuba,  and  25«.  in  Hawaii. 

1  Achard  himself  recognised  varieties  of  the  beet  best  adapted  for  the  manufacture  of  sugar,  but  it  was  Vilmorin, 
in  France,  who  in  1856  rationally  selected  the  first  variety  rich  in  sugar  (VUmorin's  white)  by  repeated  repro- 
duction of  the  roots  with  the  highest  saccharine  content ;  this  he  arrived  at  by  immersing  the  roots  in  saline 
solutions  of  different  concentrations  so  as  to  determine  their  specific  gravities,  from  which  he  deduced  the  content 
of  sugar.  Later,  however,  Scheibler  showed  that  there  is  not  always  proportionality  between  the  specific  gravity 
and  saccharine  value. 

In  Germany,  more  rigorous  methods  of  selection  were  introduced  by  Rabbethge  and  Oiesecke  (1862),  who 
analysed  selected  beets  cut  into  portions  and  determined,  not  only  the  richness  in  sugar,  but  also  the  purity  of 
the  juice  polarimetrically.  Kuhn  then  improved  the  selection  still  further  by  microscopic  examination  of  the  seeds. 

Choice  of  seed  is  of  great  importance  and  seed  should  be  obtained  only  from  reliable  firms  ;  a  saving  of  a  few 
shillings  in  buying  seed  sometimes  involves  serious  losses. 

Special  preparation  of  the  seed  (shelling,  impregnation,  &c.)  does  not  appear  to  have  any  practical  value, 
but,  on  the  other  hand,  Briem  (1910)  states  that  repeated  selection  and  adaptation  to  the  new  intensive  culture 
methods  is  able  to  produce  in  20  years  an  increase  in  the  mean  saccharine  content  from  14  to  19  per  cent.,  besides 
an  increase  in  the  weight  of  the  beets  owing  to  the  roots  becoming  accustomed  to  more  energetic  fertilisers. 

There  are  now  numerous  varieties  of  beetroot  known  by  the  names  of  their  producers  or  of  the  places  where 
they  wore  first  selected.  Among  such  varieties  the  best  are  the  Klein-Wanzleben,  Dippe,  Kuhn,  Braune,  Vil- 
morin, Arc. ;  these  can  be  distinguished,  although  not  always  readily,  by  the  shape  of  the  roots  arid  leaves  and 
by  the  saccharine  content. 


446 

tail  (waste  products  of   the  sugar  factory)  are  the  ones  preferred  by  the  agriculturists 
and  manufacturers  (see  Fig.  288). 

Value  attaches,  besides  to  the  shape,  also  to  the  specific  gravity,  and  still  more  to  the 
sugar-content.  Fig.  289  shows  the  saccharine  content  of  the  various  zones  composing  the 
beetroot.  It  will  be  seen  that  the  richness  in  sugar  diminishes  from  the  centre  to  the  peri- 
phery, and  especially  to  the  top  and  tail,  which  also  give  the  more  impure  juices. 

Beetroots  for  fodder  or  for  domestic  purposes  are  yellow  or  red,  but  those  selected  for 
sugar  are  white,  and  any  variegation  or  colouring  with  the  original  tint  indicates  faulty 

selection  and  degeneration  or  reversion* 
to  the  primitive  type.  Roots  with  few 
leaves  or  with  long  stems  are  poor  in 
sugar,  and  denote  that  the  soil  is  of  a 
character  not  adapted  to  their  cultiva- 
tion.1 


FIG.  288. 


FIG.  289. 


The  proportions  of  the  principal  components  of  the  beetroot  vary  between  the  following 
limits  (percentages) :  water,  75  to  86  ;  sugar,  9  to  18  ;  cellulose  and  lignin,  0-8  to  2-5  ; 
nitrogenous  (protein  and  amino-)  substances,  0-8  to  3  ;  fat,  0-2  to  0-5  ;  mineral  matter 
(potassium  and  other  salts),  0-2  to  2.  Other  and  less  important  components  of  the  beet 

1  Beet  Cultivation.  Sandy  or  very  compact  (clayey)  soils  arc  not  suited  to  the  growing  of  boot.  The  most 
suitable  are  medium  soils  which  can  be  worked  to  a  considerable  depth  (35  cm.)  in  the  summer  months.  In 
Italy,  where  the  rain  is  not  so  well  distributed  as  in  Central  Europe,  it  is  necessary  to  sow  early  in  order  to  avoid 
the  excessively  dry  season. 

Fertilisation  should  be  abundant,  since  from  a  hectare  of  soil  beets  remove  annually  as  much  as  120  kilos  of 
potash  (K2O)  and  52  of  phosphoric  anhydride.  Stable  manure  serves  well  as  the  fundamental  fertiliser,  but 
the  sugar  manufacturers  require  the  farmers  to  apply  it  in  the  summer,  during  tilling,  and 
not  in  the  spring;  any  large  use  of  nitrogenous  manures  is  inadvisable.  According  to 
Stoklasa  (1910),  the  most  suitable  manuring  for  beet  is  obtained  by  a  rational  application  of 
nitragin  (see  vol.  i,  p.  302).  As  supplementary  fertilisers,  superphosphate  (about  4  quintals 
per  hectare)  and  sodium  nitrate  (1  to  1-5  quintal  per  hectare)  are  largely  used.  To  ascertain 
if  a  soil  requires  also  potash  (kainit,  carnallite,  chloride,  &c.),  the  presence  or  absence  of  potas- 
sium salts  in  the  drainage  water  is  determined  by  analysis.  In  general,  however,  1-5  to  2 
quintals  of  potash  fertiliser  are  employed  per  hectare,  since  beet  takes  about  160  kilos  of 
potash  from  the  soil  every  year.  But  in  all  eases  these  chemical  fertilisers  should  be  adminis- 
tered at  intervals  prior  to  May,  as  otherwise  the  sugar  manufacturer  may  refuse  the  roots 
owing  to  the  excessive  amount  of  salts  in  the  juice ;  not  only  is  the  latter  rendered  more 
impure  but  the  salts,  especially  chlorides,  prevent  the  crystallisation  of  part  of  the  sugar. 
Irrigation  is  inadvisable  and,  in  some  cases,  is  prohibited.  A  large  area  of  soil  in  the  pro- 
vince of  Magdeburg  became  infertile  owing  to  the  repeated  cultivation  of  beet,  but  it 
recovered  its  original  fertility  after  the  discovery  of  the  deposits  of  potassium  salts  at  Stassfurt. 
In  sowing  (which  is  carried  out  between  the  beginning  of  March  and  the  middle  of  April, 
with  a  drilling  machine  giving  rows  35  to  40  cm.  apart),  excess  of  seed  is  always  used,  so  that 
after  the  plants  have  begun  to  grow,  15  to  16  per -eq.  metre  may  remain.  The  roots  then 
attain  an  average  weight  of  500  to  600  grms.  (isolated  beets  sometimes  weigh  4  to  5  kilos) 
and,  under  favourable  conditions,  a  hectare  yields  300  to  400  quintals  of  beet  (in  Ferrarese  as 
much  as  600  quintals  are  obtained,  while  in  the  other  Italian  provinces  the  average  is  about 
300).  If  sowing  is  delayed  too  long,  the  roots  do  not  mature  well  but  remain  acid  and  give 
very  impure  juice. 

Growth  begins  5  or  6  days  after  sowing,  and  when  the  seedlings  are  a  few  centimetres  high 
women  and  children  proceed  to  thin  them  out  with  ordinary  hoes,  just  as  is  done  with  maize.  Later  on,  the 
ground  is  hoed  several  times  to  remove  weeds  and  to  keep  the  soil  sweeter  in  the  warm  weather. 


FIG.  290. 


EVALUATION  OF  SUGAR  BEETS 


447 


are :  glucose,  raffinose,  organic  acids  (oxalic,  malic,  tartaric,  citric,  malonic,  succinic, 
glutaric,  gluconic,  tricarballylic),  amido-  and  amino-compounds  (leucine,  asparagine, 
betaine,  tyrosine),  gums,  pectic  matters,  coniferin,  &c. 

The  value  of  the  beets  was  formerly  arrived  at  by  measuring  the  density  of  the  juice 
with  the  Brix  densimeter,  but  the  results  varied  considerably  with  different  varieties  of 
beet  and  also  from  other  causes.  It  is  usual  nowadays  to  determine  the  quantity  of  the 
sugar  in  the  juice  by  means  of  the  polarimeter  (e.g.  the  Soleil-Ventzke-Scheibler  or,  better, 
the  three-field  instrument  of  Schmidt  and  Haensch  ;  see  later). 

A  sample  of  the  beets  arriving  at  the  factory  is  obtained  by  allowing  fifty  to  fall  into 
a  basket  while  the  waggon  is  being  unloaded,  placing  the  fifty  in  a  row  and  taking  the 
alternate  ones,  repeating  this  operation  on  the  25,  and  of  the  12  thus  obtained  choosing 
one  small,  one  medium,  and  one  large.  From  each  of  these  three,  a  longitudinal  portion 
is  removed  by  means  of  the  Pellet  rasp,  which  gives  directly  a  homogeneous  paste,  the 
juice  being  expressed  from  this 
by  a  hand-press  (Fig.  291).  Of 
the  well-mixed  juice,  26-048  grms. 
(the  normal  weight  of  the  polari- 
meter ;  see  later)  are  introduced 
into  a  graduated  100  c.c.  flask, 
which  is  filled  to  the  extent  of 
about  two -thirds  with  water  and 
5  c.c.  of  basic  lead  acetate  solu- 
tion ;  after  the  flask  has  been 
well  shaken,  one  or  two  drops  of 
ether  are  added  to  remove  the 
froth,  and  the  solution  made  up 
to  volume  with  water,  filtered 
through  a  dry  filter,  and  read  in 
the  polarimeter  in  a  20  cm.  tube 
(see  later). 

At  the  same  time  the  Brix 
densimeter  is  used  to  determine 
the  density,  so  that  the  quantity 
of  non-saccharine  substance  (non- 
sugar)  and  the  purity  may  be 
estimated.  The  quotient  of  fio.  291. 

purity  is  obtained  by  multiply- 
ing by  100  the  ratio  between  the  true  sugar-content  and  that  (greater)  indicated  by  the 
densimeter. 

The  sugar  may  also  be  determined  by  direct  extraction  for  2  hours  in  a  Soxhlet  appa- 
ratus (see  p.  374)  of  26-048  grms.  of  the  beet  pulp,  mixed  with  3  c.c.  of  basic  lead  acetate 
solution,  with  75  c.c.  of  90  per  cent,  alcohol.  The  alcoholic  sugar  solution  is  cooled,  made 
up  to  100  c.c.  with  water,  filtered  through  a  dry  filter,  and  polarised  in  a  20-cm.  tube. 
A  very  sensitive  test  for  indicating  if  all  the  sugar  has  been  extracted  from  the  pulp  in 

If  the  season  is  a  wet  one,  the  roots  are  late  in  maturing  (end  of  September  or,  in  Germany,  end  of  October) 
and  are  poor  in  sugar,  and  have  soft  tissues  which  readily  give  up  their  juice.  In  Italy,  harvesting  takes  place 
normally  in  August,  or,  in  some  cases,  earlier  than  this. 

When  the  beets  are  ripe  the  leaves  dry  somewhat  and,  if  the  roots  are  not  dug  immediately,  in  warm  climates 
new  leaves  may  be  formed  to  the  detriment  of  the  sugar-content.  On  this  account  the  factories  are  arranged 
so  that  they  can  deal  in  a  short  time  with  the  whole  of  the  crop.  The  harvesting  is  carried  out  in  several  portions, 
since  the  manufacturer  requires  roots  not  more  than  3  to  4  days  old,  alteration  occurring  on  storing. 

Beets  which  have  flowered  prematurely  (in  a  cold  spring  or  a  very  dry  season)  are  hard  and  difficult  to  exhaust 
and  the  manufacturer  demands  that  such  plants  should  be  pulled  up  or,  at  least,  that  the  flowering  shoots  should 
be  suppressed.  Putrefaction  of  the  roots,  besides  injuring  the  quality  and  quantity  of  the  crop,  sometimes  damages 
a  large  part  of  the  beet.  Among  the  various  insects  injurious  to  the  beet  is  one  which  destroys  the  feeble  plants. 

In  soil  which  is  worked  insufficiently  and  not  deep  enough,  or  is  treated  too  late  with  stable  manure,  the  beets 
tend  to  form  bifurcated  roots  and  so  give  an  increased  amount  of  waste,  which  is  not  paid  for  by  the  manufacturer. 

In  Italy,  contracts  are  made  on  the  basis  of  Is.  7rf.  to  2s.  per  quintal  for  beets  without  roots  and  tops  (Fig. 
290),  Is.  9d.  being  paid  if  they  are  delivered  in  the  first  half  of  August  and  sometimes  only  Is.  4d.  if  in  October. 
Some  Italian  sugar  factories  have  succeeded  in  making  contracts  on  the  basis  of  the  percentage  of  sugar  present, 
as  is  often  done  in  other  countries. 

The  manufacturer  usually  deducts  5  per  cent,  or,  in  exceptional  cases,  more,  on  account  of  admixed  stones, 
soil,  &c.  As  a  rule,  roots  containing  less  than  9  per  cent,  of  sugar  are  not  accepted. 

A  few  years  ago  the  proposal  was  made  that  the  dried  leaves  of  the  beet  should  be  utilised  as  fodder,  of  which 
Germany  alone  could  produce  £8,000,000  worth  annually. 


448  ORGANIC    CHEMISTRY 

the  two  hours  consists  in  adding  to  a  couple  of  drops  of  the  last  drainings  from  the  Soxhlet 
apparatus  2  c.c.  of  water  and  5  drops  of  a  fresh  20  per  cent,  alcoholic  a-naphthol  solution, 
and  then  pouring  10  c.c.  of  concentrated  sulphuric  acid  (free  from  nitric  acid)  carefully 
down  the  side  of  the  test-tube  ;  in  presence  of  sugar,  a  violet  ring  (not  green,  yellow,  or 
reddish)  forms  at  the  surface  of  separation  of  the  two  liquids  (see  also  p.  441 ). 

EXTRACTION  OF  THE  SUGAR  FROM  THE  BEET.  After  many  and  varied  tech- 
nical  and  economic  difficulties  had  been  overcome,  the  beet-sugar  industry  became  firmly 
established  and  has  during  the  past  quarter  of  a  century  assumed  great  importance,  not 
only  on  account  of  its  magnitude,  but  also  owing  to  its  technical  perfection,  which  makes  it 
a  model  of  what  a  great  modern  chemical  industry  should  be.1 

We  shall  now  follow  shortly  the  whole  of  the  wording  of  a  rational  sugar  factory  as  far 
as  the  refining  of  the  crude  sugar  and  the  utilisation  of  the  molasses. 

(1 )  Storing  and  Washing  of  the  Beets.  When  the  beets  are  topped  and  freed  from  soil 
and  stones  they  are  weighed  (1  cu.  metre  weighs  500  to  600  kilos)  and  then  discharged 
under  long  sheds  (Fig.  292)  with  pavements  sloping  to  a  longitudinal  channel,  A,  which 
is  covered  with  movable  boards  or  gratings  and  has  water  flowing  through  it  (Fig.  293). 
The  beets  should  not  be  kept  long  in  these  silos,  as  after  a  few  days  loss  of  sugar  occurs. 
The  sugar-works  are,  however,  designed  to  deal  with  a  large  quantity  of  beets  every  day 
(4000  to  8000  quintals),  so  that  the  whole  of  the  year's  crop  may  be  worked  up  in  50  to 

1  History  of  the  Technical  Development  of  the  Beet-sugar  Industry.  In  his  earliest  industrial 
trials,  Achard  (1786)  extracted  the  sugar  by  boiling  the  beets  in  water,  expressing  the  juice,  concentrating  this 
to  a  syrupy  consistency,  and  allowing  to  crystallise  in  the  cold.  In  France,  to  facilitate  the  separation  of  the 
juice,  the  beets  were  disintegrated  by  means  of  rasps  which  converted  them  into  a  fine  paste,  this  being  squeezed 
in  screw  presses  and  later  in  far  more  powerful  hydraulic  presses.  The  juice  was  then  defecated  with  lime  and, 
after  neutralisation  with  sulphuric  acid,  concentrated  in  copper  pans.  On  cooling,  crude  crystalline  sugar  was 
obtained. 

In  Germany,  however,  the  juice  was  first  treated  with  sulphuric  acid  and,  after  a  short  rest,  neutralised  with 
chalk,  heated  with  lime  and  filtered.  The  saccharine  solution  was  concentrated  by  direct-fire  heat  and  decolorised 
with  animal  charcoal,  albumin,  or  even  blood.  The  crystallisation  was  carried  out  in  wide,  shallow  pans. 

In  some  places  use  was  made  of  the  old  Colonial  process  of  concentrating  the  juice  until,  on  cooling,  it  gave 
a  dense  mass  of  crystals  which  was  introduced  into  inverted  conical  moulds.  The  point  of  the  cone  was  closed 
by  a  plug,  which  was  then  removed  to  allow  the  liquid  to  flow  away,  the  sugar-loaf  being  subsequently  removed. 

Only  later,  after  a  proposal  made  by  Weinrich,  was  the  lime  used  for  defecating  the  juice  neutralised  by  carbon 
dioxide  instead" of  by  sulphuric  acid,  inversion  of  the  sugar  being  avoided  and  improved  defecation  obtained. 
At  the  outset,  the  carbon  dioxide  was  prepared  by  the  costly  method  of  treating  calcium  carbonate  with  hydro- 
chloric acid,  but  later  it  was  obtained  from  the  combustion  of  coal,  and  finally  by  heating  chalk  in  suitable  retorts 
or  furnaces,  the  residual  lime  being  also  utilisable. 

Further  improvements  were  made  also  in  the  rasps,  as  the  living  cells  of  the  beet,  being  coated  inside  with 
protoplasm  impermeable  to  the  cold  saccharine  liquid,  do  not  allow  the  sugar  to  exude  ;  it  is  hence  necessary 
to  rupture  the  cells  as  completely  as  possible. 

A  considerable  advance  was  made  in  1836  by  Pelleton,  who  introduced  cold  maceration  of  the  rasped  beet 
with  a  counter-current  of  water.  This  systematic  exhaustion  was  improved  by  Schutfenbach,  who  arranged  the 
vessels  of  beet-pulp  in  steps,  the  water  entering  the  top  vessel  and  being  collected  after  it  leaves  the  lowest  one  and 
then  pumped  to  the  top,  and  so  on ;  the  pulp  was  exhausted  with  fresh  water  and  the  exhausted  pulp  replaced  by  a 
fresh  supply.  It  was  necessary  to  attend  to  the  cleanliness  of  the  plant  in  order  to  avoid  the  development  of 
micro-organisms  capable  of  inverting  the  sugar.  In  1837  Schiitzenbach  suggested  the  preliminary  drying  of 
the  pulp  and  its  extraction  with  water  at  90°,  which  renders  permeable  those  cells  not  broken  by  the  rasp.  Fesca 
and  Schrottler,  on  the  other  hand,  centrifuged  the  fresh  pulp  directly — just  as  is  now  done  with  the  crystallised 
sugar  (see  later) — and  subsequently  sparged  the  pulp  with  cold  water  in  the  centrifuge  itself  so  as  to  obtain  more 
perfect  exhaustion.  But  all  these  processes  were  too  expensive  and  did  not  give  complete  extraction  of  the 
sugar,  much  of  which  was  still  lost. 

It  was  only  after  1864,  when  the  diffusion  process  was  devised,  that  complete  extraction  of  the  sugar 
became  possible  (see  above  and  later). 

Defecation  was  also  facilitated  by  separating  the  organic  impurities  precipitated  by  the  lime,  not  with  slow  and 
cumbrous  bag-filters,  but  by  the  filter-press  invented  by  Needham  in  1828,  improved  by  Kite  and  employed  in 
defecating  by  Danek  in  1862.  By  this  means,  working  was  hastened  and  cheapened,  and  further  improvement 
was  made  when  the  filter-press  was  so  modified  as  to  permit  of  the  washing  and  exhaustion  of  the  calcium  car- 
bonate with  hot  water  in  the  press  itself. 

The  application  of  animal  charcoal  (bone-black)  filters,  which  had  been  proposed  for  other  industries  by  Figuier 
in  1811,  proved  of  considerable  advantage  in  the  clarification  and  decolorisation.  The  bone-black  readily  fixes 
the  colouring-matters  and  the  chalk,  but  does  not  retain  the  sugar.  As  it  becomes  enriched  in  calcium  carbonate, 
however,  it  loses  its  decolorising  property  and  hence  required  frequent  renewal  at  great  expense.  Subsequently 
the  activity  of  the  charcoal  was  restored  by  treatment  with  dilute  hydrochloric  acid  to  eliminate  the  carbonates 
and  then  fermenting  at  a  suitable  temperature  and  with  a  suitable  proportion  of  moisture,  in  order  to  destroy 
much  of  the  organic  matter ;  the  charcoal  was  then  washed  thoroughly  with  water  and  dried  in  long  iron  tubes 
heated  to  low  redness  in  a  furnace  (see  p.  471).  A  factory  with  a  capacity  of  4000  quintals  of  beet  per  day  should 
have  at  its  disposal  6000  quintals  of  animal  black  throughout  the  whole  season.  The  cost  of  this  is  consider- 
able, and  during  recent  years  these  filters  are  being  dispensed  with  in  the  sugar  factory,  methods  of  defecation 
being  improved  and  the  filters  used  only  in  the  refinery. 

The  sugar  solutions  were,  at  one  time,  evaporated  by  direct-fire  heat,  a  total  of  40  kilos  of  coal  being  consumed 
per  quintal  of  beets.  In  1828,  Moulfarine  and  Decquer  in  France  introduced  the  use  of  steam-coils,  and  in  1840 
the  employment  of  the  Hovard  vacuum  evaporator  reduced  the  consumption  of  coal  to  25  kilos.  Since  1852, 
simple  or  multiple-effect  vacuum  evaporators  (Eillieux)  have  come  into  use  and  these,  after  many  improvements, 
have  still  further  diminished  the  amount  of  coal  required  until  nowadays  it  is  only  7  to  8  kilos. 


SLICING    OF    THE    BEETS 


449 


60  days.  In  order  to  transport  the  beets  to  the  place  where  they  are  first  required,  the 
covering  of  the  water-channel  is  gradually  removed  so  that  the  roots  fall  into  the  water, 
which  carries  them  half  floating  to  the  principal  elevator,  B,  this  separating  the  mud 
and  water  and  delivering  the  beets  to  the  washer,  C. 

The  elevator  may  consist  of  a  large  wheel  fitted  with  a  number  of  perforated  plates 
(Fig.  294)  or  of  an  inclined  screw  having  a  perforated  sieve-plate  at  G  (Fig.  295). 


FIG.  292. 

Nowadays,  however,  the  beets  are  conveniently  raised  by  applying  the  principle  of  the 
Mammoth  pump  (see  vol.  i,  p.  265),  which  also  admits  of  a  more  complete  washing. 

The  washing  is  carried  out  in  iron  or  concrete  vessels,  4  to  6  metres  long  and  1-5  to  2 
metres  wide,  furnished  with  a  longitudinal  bladed  spindle  by  which  the  roots  are  beaten 
in  the  water  and  transferred  to  the  other  end  of  the  washer  ;  on  the  bottom  are 
indentations  or  an  inclined  plane  on  which  any  stones  collect,  to  be  discharged  from  the 
orifices,  D  and  E  (Fig.  295). 

In  24  hours  such  a  washer  can  treat  as  many  as  5000  quintals 
of  beet,  about  the  same  number  of  hectolitres  of  water  being 
consumed. 

From  the  washer  the  beets  fall  into  basins,  whence  they  are 
raised  by  a  large  vertical  elevator  to  a  higher  part  of  the  factory 
and  dropped  into  a  double  automatic  weighing  machine,  which 
discharges  50  to  100  kilos  or  more  at  a  time  into  the  cutter  or  slicer  ; 
in  the  latter  they  are  reduced  to  thin  slices  suitable  for  extraction  by  the  diffusion  process. 
The  slicing  machine  is  formed  of  a  vertical  chamber,  A  (Fig.  296),  which  receives  the  roots, 


FIG.  293. 


FIG.  294. 

and  the  base  of  which  consists  of  a  circular  cast-iron  plate,  C,  rotated  by  means  of  a  vertical 
shaft  and  furnished  with  10  to  15  rectangular  apertures,  a  a  (see  plan  and  section,  Fig.  297). 
In  these  apertures  fit  cast-iron  frames  carrying  a  series  of  undulating  cutting  blades  which 
form  knives  of  various  shapes  (Fig.  298).  The  beets  at  the  bottom  of  the  chamber  are 
forced  by  those  above  against  the  rotating  knives  and  so  sliced.  The  form  of  these  slicers 
varies  somewhat  in  different  factories,  and  in  some  cases  the  revolving  plate  has  a  diameter 
II  29 


450 


ORGANIC    CHEMISTRY 


FIG.  295. 


of  1-2  to  1-5  metre  and  a  velocity  of  100  to  140  turns  per  minute.     The  beet -chamber  is 

about  1-5  metre  high. 

At  one  time  use  was  made  of  knives  with  several  superposed  blades  at  various  distances 

apart,  but  these  give  smooth 
slices  or  prisms  (if  cut  longi- 
tudinally) which  readily  ad- 
hered one  to  the  other  and 
hence  presented  a  diminished 
surface  in  the  subsequent 
diffusion  operations.  Good 
results  are,  however,  obtained 
with  those  having  a  zig-zag 
section  (Fig.  299)  and  giving 
slices  having  the  form  of  tri- 
angular channels  ;  sometimes 
a  blade  is  placed  at  the  apex 
of  each  angle,  so  as  to  prevent 
the  formation  of  wide  slices. 
The  side  of  the  triangle  in  the 
blades  is  6  to  7  mm.,  and  the 
thickness  of  the  slices  is 

regulated  by  the  height  of  the  knives  above  the  plate,  a  (Fig.  298). 

Centrifugal  slicing  machines  are  also  used,  these  having  knives  fixed  to  the  inner  peri- 
phery of  the  vertical  drum,  which  receives  the  roots  and  projects  them  against  the  blades. 

These  machines  give  a  greater  output  and  uniform  working,  the  knives  being  replaceable 

when  in  action.    The  knives  usually  wear  rapidly, 

especially   if  stones  occur  in   the  interior  or   in 

indentations   of    the   roots,   and   they  should   be 

changed  frequently,  as  otherwise  they  do  not  cut 

clearly  but  tear,  this  resulting  in  slow  extraction 

of   the   sugar  in   the  diffusors.      The  knives  are 

sharpened  with  triangular    files  or  with  suitable 

milling  -cutter  s . 

EXTRACTION  OF  SUGAR  BY  THE  DIF- 
FUSION PROCESS.  In  the  note  on  p.  448  men- 
tion has  already  been  made  of  the  various  steps 

made  in  the  extraction  of  sugar  from  beets  and  of 

the  diffusion  process,  which  is  now  used  and  which 

presents  marked  advantages  over  earlier  methods. 

The  diffusion  process  is  based  on  the  general  laws 

of  osmosis  (see  vol.  i,  p.  77).     If  a  solution  of  sugar 

(or  salt  or,  in  general,  any  crystalloid)  is  enclosed 

in  a   porous   membrane   immersed  in  water,   the 

sugar  molecules  pass  slowly  through  the  membrane 

to  the  outside  (exosmosis),  while  water  passes  from 

the    outside    to    the   inside    (endosmosis).      This 

process  continues  until  the  specific  gravities  of  the 

sugar   solutions   inside   and  outside  are  identical 

(equal    numbers    of    sugar    molecules    then    pass 

through  the  membrane  outwards  and  inwards)  ; 

or,  if  it  is  required  to  remove  all  the  sugar  from 

the   inside,  the  water  outside   is  continually  re- 
newed.    The  same  phenomenon  is  shown  by  the 

sugar -containing  vegetable  cells  of  the  beet.    The 

envelope  of  the  cell  functions  as  an  osmotic  mem- 
brane, although  the  sugar  inside  the  cell  and  the 

walls  of  the  latter  also  are  coated  with  protoplasm  which,  at  the  ordinary  temperature, 

prevents  or  greatly  retards  the  osmotic  flow. 

But  at  a  temperature  of  70°  osmosis  takes  place  more  readily  through  the  saccharine 

cells  of  the  beet,  the  protoplasm  then  coagulating  and  the  walls  becoming  permeable  to 


FIG.  296. 


EXTRACTION    BY   DIFFUSION 


451 


the  osmotic  currents.     Under  these  conditions  the  complete  extraction  of  the  sugar  is 
possible  (not  more  than  0-3  to  0-4  per  cent,  is  left). 

The  first  industrial  application  of  this  method  was  attempted  in  1864  by  Robert  in 
the  celebrated  factory  at  Seelowitz  (Moravia),  and  the  results  were  EO  favourable  that  by 
1867  about  thirty  factories  had  adopted  it.  It  was  then  that  the  idea  was  evolved  of 
cutting  the  beets  into  slices  to  facilitate  the  osmotic  phenomena,  the  extraction  being 
effected  by  systematic  and  continuous  exhaustion  in  a  series  of  cylindrical  vessels  contain- 
ing the  slices.  Water  at  70°  enters  the 
first  cylinder,  carries  away  part  of  the 
sugar,  and  then  passes  to  the  other  cylinders 
in  succession,  until  it  reaches  in  the  last  the 
same  density  (about  10  to  12  per  cent,  of 
sugar)  as  the  saccharine  juice  of  the  cells 
of  the  fresh  beet.  When  the  first  cylinder 
is  exhausted  it  is  recharged  with  fresh 
slices  and  placed  at  the  other  end  of  the 
series.  What  was  previously  the  second 
cylinder  now  receives  the  pure  water  and 
is  hence  exhausted,  after  which  it  is  filled 
with  fresh  slices  and  made  the  last  of  the 
battery,  and  so  on.  In  such  manner  the 
process  becomes  systematic  and  continuous,  FIG.  297. 

being  carried  on  day  and  night  during  the 

whole  of  the  campaign.     The  circulating  water  is  brought  to  a  temperature  of  70°  while 
passing  from  each  cylinder  to  the  next. 

Diffusor  Batteries.  The  diffusors  are  vertical  iron  cylinders  with  a  capacity  of  15  to  50 
hectols.  and  a  height  double  the  diameter.  They  are  furnished  with  an  upper  aperture 
for  charging  with  the  slices  and  one  at  the  bottom  or  side  for  the  discharge  of  the  exhausted 
pulp. 

They  are  arranged  in  batteries  of  12  to  24  diffusors  connected  by  pipes  and  valves, 
heating  tubes  being  placed  between.  For  a  factory  treating  P  quintals  of  beet  per  24  hours, 

p 
diffusors  having  capacities  of hectols.  each  are  now  used. 

The  diffusors  are  often  arranged  in  two  parallel  rows  (Figs.  300,  301,  302),  und  if  they 
are  then  discharged  laterally  the  exhausted  slices  can  be  collected  by  means  of  a  single 


FIG.  298. 


FIG.  299. 


screw  or  travelling  band,  h,  which  carries  them  to  the  elevators,  m  ;  where  they  are 
discharged  through  an  aperture  in  ihe  base  (Fig.  303),  two  channels  with  screws  are  used. 

Sometimes  the  diffusors  are  placed  in  a  ring,  as  is  shown  in  section  in  Fig.  304  and  in 
plan  in  Fig.  305.  The  diffusors  are  charged  by  means  of  suspended  tubs  coming  from  the 
slicing  machine,  or  of  an  endless  belt  moving  above  them  on  rollers  and  flanked  with  a 
fixed  plate  forming  an  edge  fitted  with  doors  corresponding  with  the  various  diffusors. 
By  opening  a  door  and  placing  a  plate  diagonally  on  the  belt,  the  slices  are  forced  off  the 
latter  into  a  sloping  channel  and  so  into  the  diffusor  ;  this  operation  is  repeated  until  all 
the  diffusors  are  full. 

When  the  diffusors  are  arranged  in  a  circular  battery,  the  slicing  machine  (D,  Fig.  304) 
is  placed  so  that  it  commands  the  diffusors,  which  are  charged  by  means  of  a  shoot,  E. 

A  perforated  false  bottom  and  an  upper  perforated  disc  in  each  diffusor  prevent  the 
penetration  of  the  beet  slices  into  the  tubes  that  supply  water  or  carry  off  the  juice.  To 
avoid  accidents  when  operations  are  started,  the  tubes  are  provided  with  safety-valves 


452 


ORGANIC    CHEMISTRY 


Air-cocks  on  the  covers  allow  of  the  escape  of  the  air  displaced  by  the  water  entering 
the  diflfusors.  Thermometers  are  inserted  in  the  tubes  to  indicate  the  temperature 
of  the  water  and  of  the  circulating  juice.  There  are  tubes  for  cold  water,  transference  of 
the  juice,  washing  water,  discharge  of  the  water,  steam  for  the  heaters,  and  discharge 
of  the  juice. 


FIG.  300. 

The  heaters  used  to  regulate  the  temperature  of  the  circulating  juices  consist  of  a  series 
of  steam-pipes  (see  6,  Fig.  301)  round  which  the  juice  passes.  A  less  rational  method  of 
raising  the  temperature  consists  in  blowing  steam  into  the  juice  ;  this  not  only  dilutes 
the  juice  but  may  cause  caramelisation. 

Water  is  supplied  to  the  diffusor  battery  through  two  pipes  which  join  just  before 

the  diffusor  is  reached  ;  one  of  these 
comes  from  a  cold-water  cistern  8  to 
10  metres  above  the  level  of  the 
diffusors  and  the  other  from  the 
boiler.  Mixture  of  the  hot  and  cold 
water  in  the  proper  proportions  gives 
the  temperature  required  for  diffusion, 
this  being  at  first  about  35°  and  later 
70°  to  75°,  to  which  it  is  brought  by 
the  heaters.1 

1  Method  of  Starting  a  Battery  of  Dif- 
fusors. In  the  various  tubes  common  to  all  the 
diffusors  are  inserted  valves  which  admit  of  the 
communication  of  the  tubes  with  each  diffusor 
and  also  of  the  isolation  of  any  diffusor  from  its 
two  neighbours.  The  juice  discharge  pipe  is  fur- 
nished with  a  valve  placed  to  the  left  hand  of  the 
upper  pipe  (see  Diagram,  Fig.  304)  leading  to  the 
juice  measurer  and  then  to  the  collecting  vessel. 

Assuming  the  battery  to  consist  of  12  diffusors  (in  two  parallel  rows  or  in  a  ring),  the  first  three  are  closed 
above  and  below,  while  the  remaining  ones  are  closed  only  at  the  bottom.  Into  the  empty  diffusor,  I,  water  at 
35°  is  passed  through  c,  the  air-cock,  a,  in  the  lid  being  left  open  ;  when  I  is  full,  the  air-cock  is  closed  and  the 
juice-valve,  c2,  the  steam-valve  of  heater  1  (not  shown  in  the  figure)  and  the  air-cock  of  diffusor  II  opened,  II 
thus  being  filled  with  water  at  50°  (shown  by  the  thermometers  in  the  pipe  by  which  the  juice  leaves  the  heater). 
When  II  is  also  full  of  water,  the  air-cock  is  closed  and  III  then  filled  in  a  similar  manner  with  water  at  70°. 
While  these  operations  are  proceeding  with  the  first  three  diffusors  (containing  no  slices),  the  slicing  machine 
is  started  and  diffusor  IV  and  the  rest  filled  with  slices.  But  as  soon  as  IV  is  full,  the  slices  are  covered  with  the 
perforated  disc  and  the  lid  closed,  the  air-cock,  «4,  being  left  open.  Then,  on  opening  the  taps,  d,  and  dt,  of  the 
j  uice-pipe,  IV  becomes  filled  from  the  bottom  upwards  with  water  at  75°,  which  first  passes  downwards  through 
the  heater  4.  It  is  an  advantage  to  introduce  the  liquid  at  the  bottom  of  the  diffusor,  as  the  slices  are  thereby  lifted 
and  the  air  completely  expelled.  In  diffusor  IV  the  water  begins  to  extract  the  sugar  from  the  slices,  and  when 
the  liquid  has  risen  to  the  air-cock,  a«,  this  and  also  ds  are  closed,  while  the  valves  ct,  df,  and  a6  are  opened.  By 
this  means,  since  c  is  kept  in  communication  with  the  water  cistern  at  a  head  of  about  10  metres,  the  water  forces 
the  liquid  from  I  into  II,  and  so  into  IU,  IV,  and  V,  the  course  taken  being  I,  1,  ca,  II,  2,  <•„  III,  3,  ct,  IV,  4,  dt, 


FIG.  301. 


PULP    PRESSING    AND    DRYING 


453 


The  amount  of  juice  extracted  normally  by  every  diffusor  is  about  48  to  55  litres  per 
hectolitre  capacity  of  the  diffusor  (i.e,  100  to  110  per  cent,  of  the  weight  of  the  beets,  since 


FIG.  302. 

each  hectolitre  holds  50  to  55  kilos  of  slices).  The  amount  of  water  neceeeary  for  complete 
diffusion  (including  washing  water)  is  1-2  to  1-5  times  the  weight  x>f  the  beet  (hence  the 
water-tank  should  have  a  capacity  at  least  as  great  as  3  or  4  of 
the  diffusors). 

Pressing  and  Drying  the  Pulp.  The  pulp  (exhausted  slices 
containing  less  than  0-5  per  cent,  of  sugar)  discharged  from 
the  diffusors  is  transported  by  a  screw  or  endless  band  to  an 
elevator  which  discharges  it  into  the  pulp-press  (M,  Fig.  305), 
where  the  water  it  contains  (95  per  cent.)  is  removed  as 
completely  as  possible.  Presses  of  various  forms  are  used  for 
this  purpose. 

ds,  V.    When  the  juice  reaches  as,  the  same  operation  is  repeated,  that  is,  a,  (-, 
and  dt  are  closed  and  cs,  dt,  and  a,  opened,  so  that  the  juice  is  forced  from  \ 
the  preceding  cylinders  into  VI  through  5,  dt,  d,,  and  6,  the  temperature 
being  kept  at  70°  to  75°. 

The  juice  from  VI  is  not  passed  into  VII,  but  part  of  it  is  first  discharged 
(see  later)  into  the  juice  measurer  (and  thence  into  a  reservoir)  by  opening  the 
main  valve,  M ,  and  keeping  d7  shut ;  when  the  amount  in  the  measurer  reaches 
a  certain  value,  M  is  closed,  A^  opened  and  diffusor  VII  filled  from  below  in  the 
usual  manner.  In  all  these  cases  the  pressure  is  supplied  by  the  water  in 
the  raised  cistern.  When  VII  is  full,  before  the  juice  is  passed  into  VIII, 
part  of  it  is  discharged  into  the  measurer  through  the  valve,  M ,  as  before  ;  _,  ft 

these  operations  are  repeated   until   the  last  diffusor  is  reached.      When, 
however,  IX  is  filled,  it  is  advisable  to  discharge  the  water  from  diffusors 

I,  II,  and  III,  and  to  fill  these  with  slices,  so  that,  when  the  juice  arrives  at  III,  it  is  certain  that  the  slices  in 
IV  (the  first  to  be  extracted)  are  exhausted ;     IV  is  then  emptied  and  recharged  immediately  with  fresh  slices. 


IV  4  V  5          VI  6          VII 


Fro.  304. 

The  juice  is  then  passed  from  III  to  IV,  while  V  is  discharged  and  recharged,  and  so  on.  The  working  thus 
assumes  its  normal  course.  In  case  of  accident,  the  workman  regulating  the  taps  immediately  shuts  off  t  he 
steam  and  water,  so  as  to  prevent  caramelisation  of  the  juice  and  loss  of  sugar. 

The  temperature  is  35°  in  the  diffusor  following  that  which  receives  the  fresh  water,  then  rises  to  60°,  and 
in  the  last  diffusor  (preceding  that  into  which  the  water  first  passes)  is  70"  to  75°. 


454 


ORGANIC    CHEMISTRY 


That  of  the  Kluscmann  type  consists  of  a  vertical,  revolving  cone  of  perforated  sheet' 
metal,  C  (Figs.  307,  308),  fitted  with  oblique  vanes  and  enclosed  in  a  stationary  cylinder, 
also  perforated.  The  vanes,  which  are  arranged  helically  alone  the  cone,  compress  the 


FIG.  305 


FIG.  306. 

mass  of  pulp  against  the  perforated  cylinder  and  gradually  move  it  downwards  where  the 
space  becomes  narrower,  so  that  a  considerable  part  of  the  water  is  squeezed  out  through 
the  cone  and  cylinder,  which  are  enclosed  in  a  jacket,  E ;  all  the  water  is  carried  off  by 
the  tubes  F,  G,  and  H,  while  the  pressed  pulp  is  discharged  through  the  annular  orifice,  7. 
An  arrangement  similar  to  this  has  also  been  combined  with  the  pulp-elevator,  which 
consists  of  an  inclined  screw,  the  pulp  being  thus  raised  and  pressed  at  the  same  time. 


KLUSEMAKN    PRESS 


455 


The  Klusemaim  press  has  been  improved  by  Bergreen  and  others  in  order  to  diminish 
the  amount  of  water  left  in  the  pulp.  Each  quintal  of  beet  yields  about  80  kilos  of  pressed 
pulp  containing,  on  an  average,  72  per  cent,  of  water,  3  per  cent,  of  ash,  1-8  per  cent,  of 
protein,  0-27  per  cent,  of  fat,  6  per  cent,  of  cellulose,  and  17  per  cent,  of  non -nitrogenous 
extractive  matter. 


FIG.  309. 

The  pressed  pulp  is  loaded  directly  on  the  farmers'  waggons  to  be  used  as  fodder,  about 
Wd.  per  quintal  being  paid  for  it  ;  but  part  of  it  (30  per  cent,  of  the  amount  of  beets  they 
supply  to  the  factory)  is  given  to  them  free  of  cost.  If  the  pulp  cannot  be  sold  immediately, 
it  is  stored  in  silos  until  sold.  But  if  this  is  done,  it  readily  undergoes  putrefactive  fermenta- 
tion, the  gasogenic  bacteria  of  which  contaminate  milk  and  cause  inflation  of  cheese,  so 
that  in  some  countries,  where  fuel  is  not  expensive,  it  is  preferred  to  dry  the  pulp  at  once. 
It  is  known,  too,  that  fresh  pulp  in  silos  loses  as  much  as  40  per  cent,  of  its  solid  matter, 
which  is  rendered  soluble  and  volatile  by  bacteria,  the  sugar  being  converted  almost 
completely  into  lactic  acid. 

Of  the  various  types  of  apparatus  for  drying  the  pulp,  that  of  Biittner  and  Meyer 
(s$e  Fig.  309),  which  was  devised  in  1887-1888  and  rapidly  came  into  use  in  Germany, 


456 


ORGANIC    CHEMISTRY 


France,  Belgium,  and  Austria,  gives  good  results.  In  1898  sixty  German  factories  were 
employing  pulp-driers  on  this  plan.  The  moist  pulp  is  raised  by  means  of  an  elevator,  p, 
and  dropped  at  /  into  an  upper  chamber,  B,  composed  of  four  semi-cylindrical  channels 
containing  mixers  revolving  in  opposite  senses,  which  stir  and  lift  the  pulp  and  at  the 
same  time  transport  it  to  the  mixers  of  the  similar  chamber  below  ;  thence  it  passes  to  a 
third  chamber.  A  current  of  air  at  400°  from  a  furnace  enters  A  at  /  and  is  moved  in  the 
same  direction  as  the  pulp  by  the  aspirator,  C,  which  then  forces  it  into  the  dust  chamber, 
D,  and  thence  to  the  shaft.  The  pulp  should  issue  at  a  temperature  of  1 10°  so  that  moisture 
may  not  condense  on  it,  and  the  supply  of  pulp  is  regulated  so  that  the  final  proportion  of 
water  present  is  12  to  14  per  cent. 

The  composition  of  the  dry  pulp  is  as  follows :  12  per  cent,  of  water,  6-5  per  cent,  of 
ash,  8  per  cent,  of  protein,  1-2  per  cent,  of  fat,  18  per  cent,  of  cellulose,  and  55  per  cent, 
of  non-nitrogenous  extractive  substances  (5  to  7  per  cent,  being  sugar)  ;  it  is  sold  in  Italy 
at  6s.  6d.  to  8s.  per  quintal.  Recent  tests  made  by  Gorini  (1911)  show  that  the  dry  pulp 

is  not  sterile,  and  may  hence 
be  dangerous  to  milk  during 
milking  operations. 

THE  STEFFEN  PRO- 
CESS. Some  years  ago  Carl 
Steffen  patented  (Ger.  Pat. 
149,593)  a  process  of  ex- 
tracting sugar  from  the  beet 
without  the  use  of  diffusion, 
a  process  resembling  that 
used  by  Achard  125  years 
ago  (see  Note  on  p.  448). 
The .  beet  slices  (containing 
75  to  80  per  cent,  of  water) 
are  pressed,  giving  a  juice 
of  20°  to  25°  Brix.  The 
remaining  pulp  is  then 
heated  to  85°  with  more 
dilute  juice  (15°  to  17°  Brix), 
which  is  thus  enriched  with 
sugar  extracted  from  the  pulp.  The  latter  is  compressed  in  a  powerful  press  in  the  hot, 
the  residual  pulp  being  rich  in  sugar  and  hence  of  greater  value  for  cattle-food.  This 
process  yields  less  molasses  and  more  first-jet  sugar,  while  it  requires  less  expenditure  of 
water,  coal,  and  labour,  and  a  less  expensive  plant,  than  when  diffusers  are  used.  For 
each  quintal  of  beet  there  are  45  litres  of  water  less  to  evaporate.  The  Steffen  apparatus 
is  shown  diagramniatically  in  Fig.  310.  The  beets  pass  into  an  ordinary  slicer,  H,  and  the 
slices  fall  into  G  and  then  into  a  horizontal  cylinder,  M,  containing  the  juice  heated  to 
95°  to  98°  (600  litres  of  this  juice  and  100  kilos  of  cold  slices  give  a  mixture  at  85°).  A 
horizontal  screw,  Z,  transports  the  slices  to  T,  where  they  meet  a  double- jacketed  (the 
inner  casing  perforated)  worm-conveyor,  F,  which  raises  them  and  presses  them  to  some 
extent,  so  that  the  juice  runs  back  into  M .  At  the  top  of  this  conveyor  they  are  discharged 
into  a  press  of  the  type  described  on  p.  455  (Figs.  307,  308).  The  expressed  juice  returns 
through  the  tube,  V,  to  M,  while  the  pulp  falls  into  Y  and  is  conveyed  to  the  drying 
apparatus.  In  order  to  maintain  the  juice  at  a  temperature  of  85°,  part  of  it  is  continually 
forced  by  the  pump,  P,  through  the  tube,  X2,  to  the  sieve,  K2,  then  to  the  heater,  C^, 
and  through  X3  to  the  cylinder,  M  ;  if  necessary,  steam  is  injected  by  means  of  the  injector, 
C2.  In  order  to  dilute  the  juice  in  M  so  as  to  keep  it  always  at  15°  to  16°  Brix,  dilute 
sugar  solution  from  the  washing  of  the  defecation  mass  in  the  filter-presses  (see  later)  is 
introduced  both  directly  into  the  cylinder,  M,  at  R2  and  into  the  inclined  conveyor  at  J?a. 
The  excess  of  juice  flows  continuously  through  the  funnel,  A,  to  the  sieve,  Kl,  which  retains 
finely  divided  pulp,  and  then  through  the  tube,  Xj_,  to  the1  defecation  apparatus. 

This  process  admits  of  the  rapid  treatment  of  large  masses  of  material,  which  is  heated 
to  85°  in  2  to  3  minutes  and  yields  70  to  80  per  cent,  of  juice  purer  than  diffusion  juice  and 
about  30  per  cent,  of  pulp  (containing  70  per  cent,  of  water  and  10  per  cent,  of  sugar), 
which,  after  drying,  contains  10  per  cent,  of  water,  7-6  per  cent,  of  proteins,  0-4  per  cent. 


FIG.  310. 


DEFECATION    OF    THE    JUICE  457 

of  fat,  10  per  cent,  of  cellulose,  36  per  cent,  of  non-nitrogenous  extractive  matters,  52 
per  cent,  of  sugar,  and  4  per  cent,  of  ash  ;  the  expense  of  drying  in  Germany  is  about 
Q-5d.  per  100  kilos  of  the  dry  pulp. 

The  diminution  of  2  to  2-5  per  cent,  in  the  yield  of  commercial  sugar  is  compensated 
in  various  ways  ;  the  dry  pulp  is  worth  about  three  times  as  much  as  diffusion  pulp  and  is 
sold  in  Germany  at  lls.  per  quintal,  in  addition  to  which  the  diffusion  process  leads  to 
various  small  absolute  losses. 

It  must  be  admitted  that,  after  many  trials  and  much  discussion,  during  recent  years, 
the  most  competent  technical  opinion  varies  with  regard  to  the  advantages  claimed  by  the 
Steffen  process.  It  can,  however,  be  stated  that  only  the  most  efficient  diffusion  plant 
can  compete  with  the  Steffen  process,  which  up  to  the  present  has  been  found  most  advan- 
tageous in  districts  and  in  seasons  in  which  prices  for  the  dried  saccharine  pulp  are  more 
favourable  than  those  of  raw  sugar. 

In  1910  a  dozen  factories  in  Germany  alone  produced  1,300,000  quintals  of  sugar 
by  the  Steffen  process. 

In  a  new  process  devised  by  Claassen,  all  the  water  from  the  diffusion  of  the  molasses 
and  that  resulting  from  the  pressing  of  the  exhausted  pulp  are  used  directly  for  the  extrac- 
tion of  the  sliced  beets  in  the  diffusors.  In  this  manner  all  the  soluble  substances  of  the 
beet  are  returned  and  utilised,  so  that  an  increased  yield  of  sugar  is  obtained  with  a 
diminished  consumption  of  water.  This  process  requires,  however,  much  supervision 
and  care. 

The  new  process  devised  by  Hyros  and  Rak  employs  more  perfect  machinery  than  the 
Steffen  process,  yet  is  identical  with  the  latter  in  many  points  ;  but  the  heating  to  85°  is 
carried  out  in  three  stages  and  the  final  pulp  is  not  dried.  This  process  has  been  little  used; 
but,  according  to  Herzfeld,  could  be  combined  advantageously  with  the  Steffen  process. 

Other  processes,  such  as  those  of  Bosse,  Naudet,  Garez,  &c.,  are  concerned  mainly  with 
the  rapid  heating  of  the  slices  below  the  slicing  machine,  pressure  or  diffusion  then  being 
employed. 

Juice  Measurers.  These  are  special  automatic  apparatus  used  to  measure  the  juice 
extracted  at  intervals  from  the  diffusors,  each  such  quantity  of  juice  being  registered 
automatically  on  a  strip  of  paper  together  with  the  time  elapsing  between  one  discharge 
and  the  next.  This  paper  serves  to  control  the  working,  while  it  also  indicates  any 
stoppages  taking  place.  The  underlying  principle  of  such  apparatus  is  the  same  as  that 
on  which  alcohol  meters  (see  p.  146)  are  based. 

The  juice  is  then  discharged  through  coarse  filters  to  remove  vegetable  fibres,  which 
are  eventually  rejected.  This  dilute  juice  (10  to  12  per  cent,  of  sugar)  has  a  reddish  brown 
colour  and  is  further  subjected  to  a  series  of  operations,  to  be  described  below. 

Defecation  with  Lime.  In  addition  to  sugar,  the  juice  extracted  from  the  beet  contains 
proteins,  pectic  substances  (colloidal  substances  of  the  carbohydrate  group),  and  mineral 
salts.  The  pectic  matters  readily  ferment,  giving  two  gummy  acids  (Pectic  Acid, 
CsoHnOso,  and  Pectosinic  Acid,  C32H46O31),  which  convert  the  juice  almost  into  a 
gelatinous  mass  and  partially  invert  the  sugar. 

When  the  fresh  juice  is  treated  with  lime,  if  the  latter  is  not  in  excess, "insoluble  calcium 
pectates  separate  ;  whilst  if  excess  of  lime  is  present,  the  juice  is  liable  to  lactic  and  butyric 
fermentation  of  the  proteins  with  development  of  unpleasant  odours.  If  the  lime  is  added 
to  the  hot  juice,  no  fermentation  occurs  and  the  whole  of  the  organic  impurities  are  preci- 
pitated ;  but  it  is  not  possible  to  avoid  a  slight  excess  of  lime,  which  forms  insoluble 
tricalcium  sucrate,  so  that  the  mass  cannot  be  filtered  immediately.  Loss  of  sugar  in  this 
way  is  obviated  by  passing  carbon  dioxide  through  the  turbid  liquid,  this  readily  decom- 
posing the  sucrate  with  formation  of  calcium  carbonate  and  liberation  of  the  sugar.  Excess 
of  carbon  dioxide  must,  however,  be  employed,  since  otherwise  an  insoluble  double  com- 
pound of  sugar  with  calcium  carbonate  is  formed. 

The  operation  of  saturation  with  carbon  dioxide  must  be  controlled  rigorously  and 
continuously  in  the  laboratory,  since  it  is  the  principal  source  of  loss. 

The  treatment  of  the  juice  with  lime  is  carried  out  at  85°  in  suitable  vessels  provided 
with  stirrers.  The  lime  is  added  in  the  quantity  previously  determined  in  the  laboratory 
(2-5  to  3-5  per  cent.),  and  may  be  as  powder  or  in  the  form  of  milk  of  lime,  the  concen- 
tration of  the  latter  being  measured  by  means  of  automatic  floating  densimeters.  Kowalski 
and  Kosakowski  have  recently  shown  that  if,  as  was  long  ago  recommended,  the  juice  is 


458 


ORGANIC    CHEMISTRY 


FIG.  311. 


well  agitated  during  defecation  and  heating,  the  total  quantity  of  lime  required  may  be 

reduced  to  as  little  as  1  -5  per  cent.   In  France  and  Germany  saturation  with  carbon  dioxide 

is  carried  out  in  two  phases,  and  in  Austria  in  three  phases.1     The  lime  in  the  juice  is 

estimated  by  means  of  soap  solution  (Pellet's  method)  in  a  way  similar  to  that  used  to 

determine  the  hardness  of  water  (vol.  i,  p.  215). 

In  order  to  avoid  the  risk  of  redissolving  the  calcium  carbonate  (as  bicarbonate),  the 

saturation  is  first  carried  on  for  20  to  40  minutes 
at  a  temperature  of  nearly  90°  until  a  certain 
degree  of  alkalinity  remains  (0-11  to  0-13  percent.) ; 
the  juice  is  then  filtered,  heated,  saturated  again 
for  about  15  minutes  until  the  alkalinity  falls  to 
0-02  to  0-04,  and  finally  filtered  a  second  time. 
In  Austria  and  Bohemia,  however,  a  little  lime 
(0-5  to  1  per  cent,  leaving  an  alkalinity  of  0-05  to 
|oi  0-07)  is  added  before  the  second  saturation  in  the 
hot  (95°).  The  juice  is  then  filtered  and  the  third 
saturation  carried  out  at  100°  (10  minutes),  the 
alkalinity  being  reduced  to  ,0-01  to  0-03.  After  a 
fresh  filtration,  the  juice  is  thoroughly  heated  for 
a  long  time  in  another  boiler,  again  filtered  and 
despatched  to  the  concentrators.  In  some  fac- 
tories the  third  saturation  is  now  made  with 
sulphur  dioxide,  which  has  a  greater  purifying 
action  than  carbon  dioxide  and  at  the  same  time 
decolorises  the  solution.  Liquid  sulphur  dioxide 

may  be  employed,  but  it  is  cheaper  to  produce  the  gas  in  furnaces  (see  vol.  i,  p.  244).     In 

some  works  continuous  saturation  is  practised,  but  the  Austrian  system  seems  to  be  the 

best,  even  though  it  leaves  0-06  per  cent,  of  alkalinity. 

The  iron  saturation  vessels  (Figs.  311,  312)  are  pro- 
vided at  the  top  with  a  large  tube  for  the  escape  of 

the  excess  of  gas.     That  used  for  the  first  saturation  is 

often  7  metres  high,  but  is  filled  with  juice  only  to  the 

height  of  2  metres  (30  to  50  hectols.),  the  remainder  of 

the  space  gradually  being  filled  with   a   dense  froth  ; 

that  for  the   second  saturation  is  3  metres  high,  less 

foam   being  formed  in  this   case  (a  large    saturation 

chamber  is  shown  in  Fig.  313).     If   too  much  froth 

forms,  it   can  be   reduced  by  the  addition  of  a  little 

coco-nut  oil. 

The  juice  is  heated  for  the  first  saturation  by  means 

of  a  steam-coil,  and  the  carbon  dioxide  is  introduced 

at  the   bottom  by  a  perforated   tube,  6.      A  glass  is 

inserted  to  permit  of  the  operation  being  viewed,  and  a 

closed  orifice,  E,  serves  for  the  inspection  and  cleaning 

of  the  interior. 

The  completion  of  saturation  is  shown  by  phenol - 

phthalein  paper,  which  ceases  to  turn  violet.     Trained 

workmen  also  carry  out  titrations. 

A  plant  for  saturation  with  sulphur  dioxide  is  shown 

in  Fig.  314.    The  air-pump,  A,  feeds  the  sulphur  furnace, 

B,  and  the  mixture  of  air  and  sulphurous   acid  then 

passes  through  the  tube,  C,  into  the  saturator,  D,  the  excess  issuing  by  the  tubes,  E. 

1  Thelime  and  carbon  dioxide  used  in  sugar-works  are  generally  prepared  in  a  vertical  lime-furnace  (see  also 
vol.  i,  p.  489),  the  upper  outlet  of  which  communicates  with  one  or  two  water-cisterns,  into  which  the  gas  is  drawn 
by  an  aspirator  to  be- washed  and  cooled  before  being  conveyed  to  the  saturators.  Chalk  of  good  quality  (free 
from  iron  and  containing  little  sulphate  or  silica)  is  used  and  is  mixed  with  9  to  10  per  cent,  of  coke  (anthracite 
should  be  avoided,  in  order  to  prevent  the  presence  of  odorous  and  tarry  impurities  in  the  gas).  The  gases 
contain  about  30  per  cent,  of  CO.2,  and  the  size  of  the  suction-pump  is  calculated  on  the  basis  that  every  quintal 
of  lime  produced  corresponds  with  at  least  300  cu.  metres  of  gas.  The  treatment  of  5000  quintals  of  beet  per 
24  hours  requires  about  300  quintals  of  chalk  (occupying,  in  lumps,  about  15  cu.  metres),  which  give  170  quintals 
of  quicklime  with  a  consumption  of  about  85  quintals  of  coke  (9-3  cu.  metres  in  lumps). 


FIG.  312. 


FILTRATION    OF    THE    JUICE 


459 


Continuous  saturation  processes  with   a  counter- current  of  juice    and  carbon  dioxide 

(Horsin-Deon,  Raboux)  are  also  used,  but  they  do  not  seem  to  have  any  great  advantage. 

Behm,  Dammeyer,  and  Schalmeyer  propose  to  purify  the  juice  at  75°  with  a  current 

of  40  to  50  amperes  at  6  to  8  volts  for  8  to  10  minutes,  using  zinc  electrodes.     This 


FIG.  313. 

treatment  seems  to  result  in  the  deposition  of  various  organic  impurities,  but,  although 
promising  well,  the  process  has  not  been  adopted. 

Filtration  of  the  Defecated,  Saturated  Juice.     The  precipitated  calcium  carbonate  is 
separated  by  passing  the  juice  through  filter-presses?-  which  allow  the  clear  sugar-juice 


FIG.  314. 

to  pass  through  and  retain  the  suspended  impurities  and  the  calcium  carbonate  in  the 
form  of  cakes,  which,  after  being  washed,  are  readily  extracted  by  unscrewing  the  press 

1  Filter-presses  are  formed  of  a  number  of  iron  frames,  alternately  empty  and  fllled  in  and  supported  on 
two  horizontal,  parallel  rods.  An  empty  frame  is  shown  at  A  (Figs.  315,  316)  and  a  fllled-in  one  at  B  (Fig.  317). 
The  latter  is  fllled  in  with  sheet-iron  grooved  on  both  sides,  the  grooves  ending  below  in  two  horizontal  channels 


460 


ORGANIC    CHEMISTRY 


and  removing  the  frames  ;  they  fall  into  conveyors  or  trucks  underneath,  and  are  often 
used  as  lime  fertilisers.  The  first  wash-water  is  added  to  the  filtered  juice,  while  the  last 
is  used  to  slake  the  lime  for  defecation.  The  pressed  cake  should  contain  less  than  0-6 
per  cent,  of  sugar. 

The  filtering  surface  of  the  filter-presses  necessary  after  the  first  saturation  is  calcu- 
lated at  0-5  sq.  metre  per  ton  of  beet  worked  in  24  hours  ;  after  the  second  saturation 

communicating  with  a  single  tap,  r  (Fig.  317) ;  the  grooves  of  the  two  sides  are  covered  with  a  perforated  plate. 
On  the  empty  frames  are  stretched  cotton  or  linen  cloths,  which  form  two  filtering  surfaces  of  the  same  area  as 
the  frame. j[  The  frames  arc  squeezed  together  and  against  the  strengthened  block,  P,  by  the  screw,  V,  so  that 


FIG.  316. 


rani 


FIG.  315. 


FIG.  317. 


246 


hermetic  joints  arc  formed  at  the  edges  of  all  the  frames.  Each  frame  is  provided  with  bored  projections,  a  and 
b,  at  the  top  and  bottom.  When  the  frames  are  joined  up,  the  holes  in  the  projections  form  two  continuous 
channels.  The  turbid  juice  enters  at  a  and  thence  passes  through  nf  into  all  the  empty  frames,  the  air  being 
forced  out  from  these  through  the  valve,  d.  When  d  is  closed,  the  juice  passes  under  pressure  through  the  cloths 

on  the  two  sides  and  the  clear  liquid  flows 
down  the  grooves  and  is  discharged  at  r  into 
the  tank,  S.  When  the  frames,  A,  are  filled 
with  calcium  carbonate,  the  latter  is  washed 
with  water  to  remove  the  sugar  it  retains. 
Since  only  the  alternate  grooved  plates 
communicate  with  the  tube,  b,  water  intro- 
duced under  pressure  at  b  will  pass  through 
the  cakes  of  calcium  carbonate  in  the  direc- 
tion of  their  thickness  and  into  the  grooved 
plates  (not  communicating  with  b)  to  be 
discharged  at  the  taps  r.  In  this  way,  each 
cake  is  brought  into  thorough  contact  with 
the  washing  water,  which  can  be  measured 
inS. 

In  other  filter-presses  there  are  no  empty 
plates  (Figs.  318,  319),  but  each  of  these  has 
\a  central  aperture  over  which  the  filter- 
cloth,  with  a  hole  exactly  in  the  middle,  is 
screwed  with  a  ring  from  botli  sides.     The 

juice  is  introduced  into  the  chambers  between  adjacent  plates,  and  the  wash-water  passes  under  pressure  into 
alternate  (odd)  plates  from  the  tube,  m,  traversing  the  cakes,  and  collects  in  the  other  alternate  (even)  plates 
which  communicate  not  with  m  but  with  k,  the  wash-water  being  thus  discharged  ;  the  air  is  initially  discharged 
from  the  odd  frames  through  i.  Each  press  contains  20  to  50  plates,  each  3  to  5  cm.  thick,  and  with  a  length  of 
side  60  to  100  cm.  The  juice  to  be  filtered  is  pumped  in  under  a  pressure  of  3  to  4  atmos. 


FlG.  319. 


CONCENTRATION    OF    THE    JUICE 


461 


0-25  sq.  metre  suffices.  The  pressed  cakes  of  chalk  form  12  to  14  per  cent,  of  the  weight 
of  the  beets  (i.e.  four  times  the  weight  of  quicklime  used).  The  washing  of  these  cakes 
requires  1  litre  of  water  per  kilo. 

After  the  second  and  third  defecations,  use  is  often  made,  not  of  niter-presses  but  of 
mechanical  filters,  which  also  serve  for  removing  suspended  matter  and  residues  of  the 
slices  from  the  diffusor -juice. 

During  the  whole  of  its  course  from  the  diffusors  and  saturators,  the  juice  is  under 
pressure  and  should  rise  in  temperature  from  70°  to  100°  ;  but  since  heat  is  lost  in  all  the 
pipes,  in  order  that  monocalcium  sucrate  may  not  be  deposited  or  the  liquor  become 
turbid,  the  use  of  heaters  is  necessary  for  the  first  and  second  saturation  juices,  &c. 

These  heaters  consist  of  a  species  of  tubular  boiler  divided  into  three  parts  by  two 
plates,  p  (Fig.  320)  ;  each  of  the  two  end  parts  is  divided  into  10  chambers  communicating 
in  pairs  at  the  two  ends  alternately.  Opposite  chambers  are  connected  by  groups  of  long 
tubes,  4  to  5  cm.  in  diameter,  through  which  the  juice  circulates  ;  steam  enters  at  C, 
follows  a  sinuous  path  round  the  partition?,  V,  and  finally  issues  at  D.  The  juice  enters, 
at  A,  chamber  1  of  compartment  I,  and  passes  through  the  tubes  to  chamber  1  of  compart - 


FIG.  320. 

ment  II,  then  to  chamber  2  of  compartment  II,  through  the  tubes  to  chamber  2  of  com- 
partment I,  and  so  on,  until  it  reaches  chamber  10  of  compartment  I  and  hence  leaves 
the  heater  at  B. 

After  the  third  saturation  the  juice  passes  into  a  final  heater  or  boiler,  where  it  is 
thoroughly  boiled  but  not  under  pressure.  The  juice  is  moved  by  means  of  pumps,  a 
separate  one  being  used  after  each  operation  (for  raw  juice,  first  saturation  juice,  second 
saturation  juice,  &c.) ;  double-action  piston  pumps  or  Girard  pumps,  with  an  efficiency  of 
80  to  85  per  cent.,  are  employed. 

IjWhen  the  tax  is  based  on  the  volume  and  density  of  the  defecated  juice,  before  the 
latter  goes  to  the  evaporators  it  passes  into  tanks  under  the  supervision  of  the  Inland 
Revenue  authorities,  who  measure  the  density  at  85°  to  90°  and  then  reduce  it  to  the 
normal  temperature  by  means  of  tables.  Thus,  in  Italy,  up  to  1903,  tax  was  paid  on  2000 
grms.  (before  1900,  only  on  1500  grms.)  of  sugar  for  every  hectolitre  of  juice  and  every 
one-hundredth  of  a  degree  of  density  above  1. 

[CONCENTRATION  OF  THE  JUICE.  The  defecated,  saturated,  and  filtered  juice  is 
pale  yellow  and  perfectly  clear  ;  it  contains  88  to  90  per  cent,  of  water,  10  to  1 1  per  cent, 
of  sugar,  and  0-8  to  1  per  cent,  of  salts.  The  formation  of  crystallised  sugar  requires  first 
considerable  evaporation  or  concentration  and  then  boiling. 

The  suggestion  was  made  in  1907  to  concentrate  juice  by  freezing  and  removing  the  ice 
(E.  Monti,  Ger.  Pat.  194,235),  but  so  far  as  is  known  this  process  has  yielded  no  practical 
results. 

Evaporation  is  nowadays  carried  out  excusively  with  indirect  steam  and  in  multiple- 
effect  vacuum  plant.  The  vacuum  is  obtained  by  means  of  pumps,  combined  with  a  baro- 
metric water -column,  this  method  being  introduced  into  the  sugar  industry  by  Rillieux 
(see  modern  triple-  and  sextuple-effect  apparatus,  vol.  i,  p.  442  et  seq.)  ;  it  admits  of 


FIG.  321. 


ORGANIC    CHEMISTRY 

considerable  saving  in  fuel  and  avoids  blackening  or  caramelisation  of  the  juice,  the 
boiling-point  being  lowered  as  the  vacuum  is  increased.1  The  steam  from  the  first  body 
is  not  all  utilised  for  the  second  body,  part  of  it,  and  also  part  of  that  from  the  second 
body,  serving  to  heat  other  plant  (boilers,  heaters,  &c.). 

The  first  body  is  usually  heated  by  the  exhaust  steam  from  the  engines,  which  it  leaves 
at  a  pressure  of  1-5  to  2  atmos.     The  evaporation  bodies  are  simply  large  wrought  or  cast 

iron  (formerly  copper)  boilers 
surrounded  by  an  insulating 
earth.  These  bodies  are  of 
various  shapes  and  are  placed 
sometimes  vertically  and  some- 
times horizontally.  They  are 
usually  divided  into  three  com- 
partments by  means  of  two 
partitions,  held  rigid  by  a 
number  of  brass  tubes,  2  to  2-5 
cm.  in  diameter,  connecting  the 
first  and  third  compartments. 
In  boilers  with  horizontal  tubes 
(Figs.  321,  322,  323)  the  steam 
circulates  in  the  tubes  in  a 
similar  manner  to  the  juice  in 
the  heater  described  above 
(Fig.  320),  while  the  juice 
surrounds  all  the  tubes.  In 
vertical  bodies  (Fig.  324)  the 
steam,  entering  at  A  and 
issuing  at  B,  circulates  in  the 

chamber  between  the  two  partitions  and  heats  the  numerous  connecting  tubes.  The 
saccharine  solution  is  thus  brought  into  a  condition  of  vigorous  ebullition  and  circulates 
rapidly  between  the  lower  and  upper  chambers,  as  indicated  by  the  arrows  in  the  figure. 
The  level  of  the  liquid,  which  can  always  be  controlled  by  the^external  glass  tube,  a,  is 
kept  just  above  jthe  tubes  ;  in  this  way,  less  scum  is  formed,  the  free  vapour  space  is 
increased,  and  danger  of  caramelisation  is  avoided.  The  boiling  may  be  observed  through 
the^window,  r.  In  order  to  separate  the  drops  of  liquid  carried  away  in  the  steam,'  about 
two -thirds  of  the  way  up  the 

JIG  &£ 


boiler  is  placed  a  plate,  P, 
with  a  large  central  aperture, 
G,  above  which  is  arranged  a 
kind  of  metal  umbrella,  p, 
at  a  height  adjustable  by  the 
levers,  e,  w,  and  h.  This  height 
is  chosen  so  that  the  liquid 
condensing  above  P  contains 
no  sugar. 

But  with  horizontal  evapo- 
rators the  spray  separators 
consist  of  large  cylinders 
placed  above  the  boiler  (F, 
Fig.  321).  The  steam  issuing 
from  the  boiler  by  the  tubes,  E,  before  passing  to  the  exit  pipe,  H,  traverses  the  finely 
perforated  vertical  plates,  8,  which  retain  the  drops  of  solution  carried  over  by  the 
steam,  this  effect  being  facilitated  by  the  expansion  and  consequent  slackening  of  the 
steam  in  F.  The  condensed  liquid  is  returned  to  the  bottom  of  the  boiler  by  the  tube,  G. 

1  The  boiling-point  of  water  for  different  degrees  of  vacuum  is  as  follows  (Regnault-Claassen) :  with  a  vacuum 
of  50  mm.,  98-1°  ;  100  mm.,  96-1°  ;  150  mm.,  94°  ;  200  mm.,  91-7°  ;  300  mm.,  86-5°  ;  400  mm.,  80-4°  ;  500  mm., 
72-5° ;  600  mm.,  61-6°  ;  650  mm.,  53-6°  ;  700  mm.,  41-7°  ;  720  mm.,  34-2° ;  740  mm.,  22-4° ;  750  mm.,  11-8°. 
It  must,  however,  be  remembered  that  saccharine  solutions  boil  at  higher  temperatures  than  water.  Thus,  under 
the  ordinary  pressure,  a  solution  containing  30  per  cent,  of  sugar  boils  at  100-6° ;  60  per  cent.,  103-1°  ;  80  per 
cent.,  110-3°  ;  85  per  cent.,  115°. 


FIG.  322. 


EVAPORATORS 


463 


In  exceptional  cases,  where  a  large  amount  of  spray  is  persistently  formed,  this  may  be 
diminished  by  the  addition  to  the  boiler  of  a  small  quantity  of  coco -nut  oil. 

Fig.  325  shows  a  triple-effect  horizontal  evaporator  of  the  Wellner-Jelinek  type,  Fig. 
326  a  vertical  triple  effect,  and  Figs.  327  and  328  a  vertical  quadruple  effect  evaporator, 


, ,    ,.    .'  .. 

' 


Fiu.  323. 


Fiu.  324. 


in  elevation  and  plan.  In  the  last  of  these,  the  steam  passes  from  the  body  I  through 
the  tubes,  a  and  a',  to  heat  body  II,  the  steam  from  which  heats  body  III,  and  so 
on  ;  the  steam  from  the  last  body,  IV,  proceeds  through  the  tube,  N,  to  the  vacuum  pump 
and  the  barometric  water-column. 


FIG.  325. 

The  evaporation  in  the  separate  bodies  takes  place  under  reduced  pressure  in  the 
following  manner.  In  a  quadruple  effect,  steam  at  a  temperature  of  110°  to  120°  (from  a 
boiler  or  from  the  exhaust  of  an  engine)  enters  the  tubes  of  body  I,  which  contains  a  juice 
already  concentrated  to  a  considerable  extent  in  the  other  evaporation  bodies.  Since  the 
steam  generated  in  body  I  proceeds  to  the  heating  tubes  of  II,  where  it  condenses,  a  partial 
vacuum  (e.g.  of  150  mm.)  is  established  in  body  I,  in  which  boiling  will  hence  take  place 
at  a  temperature,  say  94°,  below  100°,  and  this  will  be  the  temperature  of  the  steam  which 


464 


ORGANIC    CHEMISTRY 


heats  the  second  body.  But  the  steam  given  off  by  the  rather  more  dilute  solution  of 
body  II  is  larger  in  amount,  so  that  a  more  marked  vacuum  (up  to  350  mm.)  is  produced 
by  the  vigorous  condensation  of  this  steam-  in  the  heating  tubes  of  body  III  ;  the  sugar 
solution  of  body  II  will  hence  boil  at  about  84°,  and  steam  at  this  temperature  is  able  to 
boil  the  more  dilute  liquid  of  body  III,  where  the  vacuum  may  be  as  high  as  380  mm., 


PIG.  326, 


FIG.  327. 


PIG.  328. 


corresponding  with  a  boiling-point  of  74°.  The  steam  here  produced  goes  to  boil  the  defe- 
cated diffusion  juice,  which  is  introduced  into  body  IV  ;  the  latter  is  connected  with  the 
vacuum  pump  and  with  the  barometric  column,  which  produce  a  vacuum  of  about  630 
to  640  mm.,  corresponding  with  a  boiling-point  of  about  56°. 

When  the  solution  in  body  I  has  attained  the  desired  concentration,  it  is  discharged 
and  replaced  by  that  from  body  II,  which  in  its  turn  is  filled  by  that  from  III.    The  latter 


WATER-COOLERS 


463 


is  then  charged  with  fresh  juice  by  means  of  the  tube,  0  (Fig.  32ft),  which  also  serves  for 
the  passage  of  the  juice  from  one  vessel  to  the  other.  The  steam  is  circulated  between  the 
various  bodies  by  the  tubes  G  and  H,  and  every  battery  of  heating  tubes  is  connected  with 
a  condenser  and  separator,  I. 

Fig.  329  shows  the  arrangement  of  the  three  barometric  columns,  M,  P,  and  R,  which 
produce  the  vacuum  directly  in  the  third  body  of  a  triple -effect  evaporator  (for  small 
single-  or  double-effect  plant  one  barometric  column  suffices).  The  pipe,  K,  conveys  the 
steam  from  body  3  to  the  chamber,  L,  furnished  with  an  iron  barometer  tube,  M,  at 
least  12  metres  long,  which  dips  into  a  well  or  water -tank,  T.  The  condensation  water 
collects  in  the  tube,  M,  to  a  height  corresponding  with  the  vacuum  formed  in  L,  and 
hence  in  the  body  3.  But  the  majority  of  the  steam  condenses  in  the  chamber,  N,  into 
the  top  of  which  the  tube,  O,  introduces  a  fine  cold-water  spray  which  produces  an 
abundant  and  rapid  con- 
densation of  steam  and  a 
considerable  lowering  of 

pressure,    so    that   a    large 

quantity  of  hot  water  passes 

into  the  vessel,  U,  from  the 

barometer  tube,  P.    A  little 

steam     condenses     in     the 

chamber,  Q,  communicating 

by  the  tube,   8,   with    the 

suction  pump  which  main- 
tains    the    vacuum.      The 

vacuum   pump  can  also  be 

connected,     by    means     of 

three    narrow   tubes,   with 

the    three    evaporation 

bodies,  in  which  the  vacuum 

can  be  regulated  as  desired. 

It  is   evident   that   in  the 

three     evaporation    bodies, 

especially  in  P,  the  water 

must  not  be  kept  at  too 
high  a  temperature,  so  that 
it  may  not  evaporate  in  its 
turn  and  may  help  the  con- 
densation of  the  steam. 

Certain  sugar -works  have 
recently     made     successful 


FIG.  329. 


use  of  the  Kestner  concentration  system  (see  vol.  i,  p.  443),  which  gives  an  evaporative 
efficiency  superior  to  that  of  the  ordinary  multiple -effect  apparatus.  Indeed,  when  there 
is  a  difference  of,  say,  7°  between  the  temperature  of  the  steam  in  the  boiler  (e.g.  135°) 
and  that  of  the  heated  juice  (e.g.  128°),  an  evaporation  of  80  kilos  of  water  per  square 
metre  of  heating  surface  (i.e.  11-4  kilos  per  degree  of  temperature  difference),  is  obtained 
with  a  reduction  of  the  coal  consumption  to  5  kilos  per  100  kilos  of  beet. 

In  factories  where  there  is  not  an  abundance  of  water  (that  required  by  vacuum  plant 
is  ten  to  twelve  times  the  quantity  of  juice  to  be  concentrated),  it  is  convenient  to  utilise 
the  hot  condensed  water  from  the  steam-engines  (an  engine  of  350  to  400  h.p.  requires 
about  1  cu.  metre  of  water  per  minute  for  condensation)  and  that  from  the  vacuum  concen- 
tration batteries.  This  water  is  cooled  in  suitable  atmospheric  coolers,  T  (Fig.  330),  so 
that  it  can  be  used  in  the  barometric  tubes  and  also  for  the  washing  and  hydraulic  trans- 
port of  the  beets.  The  tank,  K,  corresponds  with  that  marked  U  in  the  preceding  figure, 
A  pump,  A,  forces  this  water  to  the  top  of  the  pile,  T  (see  also  vol.  i,  p.  454),  whence  it 
flows  down  over  the  faggots  built  up  under  a  kind  of  hood,  which  produces  a  strongupwar 
draught  of  air  and  so  evaporates  and  cools  the  water  (e.g.  from  50°  to  60°  down  to  25°  to  30°). 
The  latter  collects  underneath  in  the  tank,  r,  and  is  then  transferred  by  the  pump,  M, 
to  the  chamber,  F,  where  the  dissolved  air  is  separated  and  passes  out  through  the  pipe,  g 
(higher  than  O).  The  water  rises  in  the  tube,  O,  to  the  top  of  the  barometric  condenser,  C, 
II  30 


466 

which  is  evacuated  by  the  pump,  B,  and  the  tube,  n  ;  the  pipe,  F  or  S,  corresponds  with 

the  tube,  K,  of  the  preceding  figure  and  communicates  with  the  third  evaporation  body. 

Other  more  efficient  arrangements  are  also  used  for  the  cooling  of  the  hot  water.    Fig. 

331  shows  a  system  consisting  of  numbers  of  vertical  rods  arranged  in  layers  crossing  one 
another  in  a  manner  similar  to  those  of  the  apparatus  depicted  in  Fig.  244  (p.  283).      The 
hot  water,  entering  by  the  pipe,  A,  is  distributed  homogeneously  by  means  of  the  tooth- 
edged  channel,  C,  and  collects  in  the  vessel,  B,  underneath  ;    the  air   drawn   upwards 
between  the  rods  carries  with  it  a  cloud  of  steam.    Another  arrangement  is  shown  in  Fig. 

332  ;  here  a  wooden  cap  or  cover  fits  over  walls  composed  of  sticks  arranged  in  the  form 
of  Venetian  blinds,  while  at  the  bottom  a  Korting  injector  produces  a  powerful  jet  of 
pulverised  water  in  the  shape  of  an  inverted  cone.     The  upward  air-current  evaporates 
the  water  while  the  latter  ascends  or  while  it  flows  down  in  a  thin  film  on  the  boards  (in 
this  manner  only  4  per  cent,  of  the  water  is  lost).    Equally  ingenious  and  simple  is  the 


cooling  effected  by  forcing  the  hot  water  under  pressure  into  a  circular  pipe  fitted  with 
a  number  of  Korting  pulverisers,  catching  the  water  in  a  large  tank  and,  if  necessary, 
passing  it  again  through  the  pulverisers  (Fig.  333)  ;  but  by  this  procedure  more  than 
10  per  cent,  of  the  water  is  lost. 

In  those  seasons  of  the  year  and  on  those  days  when  the  air  is  warm  and  dry,  the 
temperature  of  the  water  can  generally  be  reduced  to  that  of  the  air  ;  but  if  the  air  is 
cold  and  not  very  dry,  the  temperature  of  the  water  remains  6°  to  7°  above  that  of  the 
atmosphere. 

BOILING  OF  THE  CONCENTRATED  JUICE.  The  juice  from  the  evaporators  has 
a  density  of  28°  to  30°  Be.  (  =  50°  to  55°  Brix)  and  an  intense  brown  colour,  and  in  order 
to  induce  crystallisation  of  the  sugar  it  is  necessary  to  concentrate  it  until  not  more  than 
15  per  cent,  of  water  remains  (85°  Brix).  This  concentration  or  boiling  is  carried  out  in 
simple  vacuum  boilers  or  vacuum  pans,  the  juice  being  first  filtered  through  mechanical 
filters,  collected  in  tanks  and  drawn  into  the  pans  which  are  already  evacuated. 

These  pans  resemble  ordinary  evaporators  and  are  made  of  sheet-iron  ;  they  may  be 
either  horizontal  (like  that  shown  in  Figs.  311  and  312)  or  vertical.  In  the  lower  part  of 
the  pan  is  a  dense  coil  of  copper  or  brass  pipes  arranged  either  in  a  zigzag  manner  or  in 
concentric  circles,  and  through  these  passes  the  steam  (Fig.  334)  ;  in  some  cases,  however, 
the  bottom  of  the  pan  is  steam -jacketed  (Fig.  335).  The  concentration  or  boiling  is  carried 


BOILING    OF   THE   JUICE 


467 


out  at  as  low  a  temperature  as  possible  and  the  pan  is  fitted  with  a  froth-separator  (see 
Fig.  311),  a  tap  for  the  removal  of  test-samples  of  the  mass  towards  the  end  of  the  opera- 
tion, and  a  wide  discharge  pipe,  K. 

The  first  thing  to  be  done  is  to  evacuate  the  pan  by  connecting  it  with  the  condenser 
and  with  the  vacuum  pump.  Next  the  cock  of  the  tube  dipping  into  the  concentrated  juice 
tank  is  opened,  the  required  quantity  of  juice  being  allowed  to  enter.  Steam  is  then  passed 


FIG.  331. 


FIG.  332. 


through  the  heating  tubes.  During  the  boiling,  the  level  of  the  juice  is  not  allowed  to  fall 
beneath  the  top  of  the  heating  tubes,  since  otherwise  sugar  would  dry  on  these  tubes  and 
be  decomposed  ;  so  that  fresh  concentrated  juice  is  introduced  from  time  to  time.  At  a 
certain  stage  of  the  concentration  small  crystals  begin  to  form  and  gradually  increase  in 
size.  The  operator  extracts  samples  and  spreads  them  out  on  glass  in  order  to, ascertain 
the  size  of  the  crystals  and  the  density  of  the  mass,  and  when  he  considers  that  sufficient 
of  this  massecuite — consisting  mainly  of  crystals  with  a  certain  amount  of  dark  molasses — 


FIG.  333. 

has  been  deposited  on  the  tubes,  the  heating  is  stopped  and  the  ordinary  pressure  estab- 
lished in  the  pan.  The  whole  mass  is  then  discharged  from  the  outlet,  K,  into  a  large  vessel 
furnished  with  stirrers,  where  it  is  gradually  cooled  and  the  crystallisation  completed. 
The  boiling  and  discharging  of  the  massecuite  occupy  altogether  about  10  hours.  Fig.  336 
shows  a  battery  of  Bock  cylindrical  crystallisers  fitted  with  stirrers. 

Larger  crystals  are  obtained  by  adding  to  the  crystallising  vessels  a  little  unboiled  juice, 
which  lowers  the  sugar-content  somewhat  and  retards  the  crystallisation.  When  no  further 
crystallisation  takes  place,  the  mass  is  discharged,  by  means  of  a  parachute  at  the  bottom 
of  the  crystalliser,  into  the  centrifuges,  which  readily  separate  the  liquid  molasses  from 
the  solid  sugar. 


468 


ORGANIC    CHEMISTRY 


This  process  of  boiling  is  termed  boiling  to  grain  to  distinguish  it  from  the  boiling  to 
thread,  now  used  only  in  refining.  In  the  latter  case  the  boiling  is  not  continued  until 
crystals  form,  the  proper  density  of  the  boiled  juice  being  ascertained  by  squeezing  a  drop 
between  the  finger  and  thumb  and  then  sharply  withdrawing  the  finger  ;  if  a  filament  is 


Fret.  334. 


Fia.  335. 


thus  formed,  the  boiling  is  not  finished,  but  the  breaking  of  the  thread  with  formation  of 
two  projections  indicates  the  end  of  the  boiling.  The  syrup  is  then  poured  into  moulds, 
which  are  kept  lukewarm  until  the  whole  mass  sets  to  an  almost  solid  block  composed  of 
finer  crystals  than  in  the  preceding  case. 


FIG.  336. 

CENTRIFUGATION  OF  THE  FIRST  MASSECUITE.  The  centrifuges  for  the 
massecuite  have  drums  of  perforated  steel  with  an  inner  coating  of  fine -meshed  gauze. 
The  diameter  of  the  drum  is  about  80  to  100  cm.,  the  height  40  to  45  cm., [and  the  speed 
of  rotation  800  to  1000  per  minute.  The  motive  force  is  applied  underneath,  and  the 


CENTRIFUGATION    OF    MASSECUITE      469 


centrifuged  sugar  remaining  in  the  drum  is  discharged  either  above  (Fig.  337)  or  through 

a  door  which  can  be  opened  in  the  base  of  the  drum  (Fig.  338).    The  massecuite  is  passed 

directly  from   the  crystallisers 

to     the     centrifuges,    and,    in 

order  to  effect  more  complete 

separation     of     the     molasses 

adhering  to  the  surface  of  the 

crystals,  especially  in  the  layer 

adjacent  to  the  gauze,  so-called 

covering  or  clearing  is  resorted 

to  ;    while    the    centrifuge    is 

still   in    motion,   the    sugar   is 

sprayed    with     finely    divided 

cold  or  tepid  water  (Fig.  339), 

or  even   with  a  jet  of  steam 

applied  inside  or,  better,  to  the 

outside     of    the     basket,    the 

molasses  being  thereby  ren- 
dered more  liquid.  This  pro- 
cedure naturally  gives  a  whiter 

raw  sugar  (first  product)  but 

in   diminished    yield,    a   small 

part  of  the  sugar  being  carried  FIG.  337. 

away  with  the  molasses  by  the 

water.    This  loss  is  diminished  by  using,  in  place  of  water  or  steam,  sugar  juices  (syrups) 

gradually  increasing  in  purity,  so  that  the  molasses  and  less  pure  syrups  are  removed 

and  the  sugar  left  covered  with  a  solu- 
tion of  pure  sugar.  In  this  way  minute, 
moderately  white  crystals  of  sugar  are 
obtained,  and  these  are  sometimes  placed 
on  the  market  without  refining.  But  the 
public  suspects  them  of  being  adul- 
terated and  prefers  quite  white  crystals 
or  cubes. 

The  molasses  from  the  centrifugation 
of  the  first  massecuite,  after  separation 
of  the  first-product  sugar  (first  runnings), 
is  further  concentrated  and  boiled  in 
syrup  pans,  which  are  similar  to  vertical 
evaporators  and  are  worked  under  a 


vacuum,  but  are  usually  of  single  effect. 
FIG/  338.  The  boiling  is  continued  until  the  syrup 

gives  a  long  thread  (see  above),  the 
impurities  present  preventing  boiling  to  grain. 
This  second  massecuite  is  then  placed  in 
large  tanks  in  the  molasses  room,  where  it  is 
kept  for  25  to  30  days  at  a  temperature  of  35° 
to  40°.  The  blocks  of  crystals  which  separate 
are  broken  up  with  suitable  bladed  machines, 
and  are  then  delivered  to  the  centrifuges  by 
means  of  screws  or  piston  pumps.  The  result- 
ing second-product  sugar  is  rather  yellow.  The 
molasses  which  then  separates  is  further 
concentrated  and  the  third  massecuite  sent 
to  the  molasses  room,  but  no  more  sugar 
separates,  since  the  various  potassium  and 
other  salts  present  prevent  about  five  times 

their  own  weight  of  sugar  from  crystallising.      This   molasses    is   hence    fold  as    it  is 
for  the  preparation  of  cattle-foods  or  for  the  manufacture  of  spirit  (see  p.  140).     In  some 


470 


ORGANIC    CHEMISTRY 


countries,  however,  it  is  treated  by  special  processes  for  the  extraction  of  the  sugar 
still  present.1     Every  100  kilos  of  beet  treated  yield  1  to  3  kilos  of  molasses. 

The  first-  and  second-product  sugars  from  the  centrifuges  are  sent  to  the  stores,  where 
they  are  sieved  to  break  up  the  crusts,  which  retain,  molasses.  The  two  products  are  often 
mixed,  put  up  in  bags  holding  100  kilos,  and  despatched  to  the  refinery. 

SUGAR-REFINING.  The  raw  sugar  (first  and  second  products,  with  a  purity  of  88 
to  96  per  cent.)  is  not  usually  placed  on  the  market,  but  is  purified  in  refineries,  where  it 
is  dissolved  in  hot  water,  the  purer  and  less  coloured  qualities  of  high  rendcmcnt z  being 
kept  separate  from  the  more  impure  grades  of  low  rendement. 

The  solution,  with  a  density  of  37°  to  39°  Be.,  is  treated  with  a  little  lime,  with  3  to  4 
per  cent,  of  animal  charcoal  and  often  with  2  per  cent,  of  ox-blood,  after  which  it  is  boiled, 
the  frothy  crust  forming  at  the  surface  being  continually  broken.  The  suspended 

matter  is  then-  removed  by  rapid  me- 
chanical filters  or  by  filter-presses.  The 
residue  (refinery  black)  is  utilised  as  a 
manure,  while  the  hot  and  still  coloured 
solution  is  passed  through  a  battery  of 
f  >ur  or  six  tower  filters,  8  to  9  metres 
i  i  height  and  60  to  80  cm.  in  diameter, 
fi  led  with  animal  charcoal  (Fig.  340  : 
A,  tube  for  dense  juice,  B  for  dilute 
juice,  C  for  water,  D  for  steam)  and 
previously  heated  with  steam  (D)  to 
prevent  the  sugar  separating  and  to 
obtain  the  maximum  decolorising  action 
of  the  charcoal,  this  being  exerted  in 
the  hot. 

The  animal  charcoal  or  bone-blaek 
has  a  considerable  affinity  for  colouring- 
matter  and  for  lime,  but  only  a  slight 
one  for  sugar.  But  in  course  of  time  the 
pores  of  the  charcoal  become  obstructed 
and  its  decolorising  power  diminished, 
so  that  after  a  few  weeks  it  becomes 
necessary  to  revivify  the  charcoal.3 

The  solution  is  passed  through  the 
filters  in  succession  and,  if  necessary, 
this  procedure  is  repeated.  When  the 
syrupy  liquid  is  decolorised,  it  is  con- 
centrated and  boiled  in  ordinary  single - 
eTect  vacuum  pans  (of  copper)  until  it 
shows  the  grain  or  short-thread  test 
(see  above). 

When  the  massecuite  reaches  this  degree  of  concentration,  it  is  poured  into  a  jacketed 
copper  vessel,  in  which  it  is  kept  at  85°  to  90°  to  initiate  the  formation  of  large  crystals. 

1  In  some  works  the  second  product  is  obtained  much  more  rapidly  by  the  Bock  or  the  GrosSc  process.  In 
'the  first  of  these,  the  molasses  is  not  left  for  25  to  30  days  in  the  molasses  room  but  is  crystallised  in  4  to  5  days 
by  continually  shaking  in  large,  jacketed  drums  heated  to  90°  to  95°  and  adding  a  considerable  quantity  (25  to 
30  per  cent.)  of  crystallised  sugar.  It  is  then  allowed  to  cool  slowly,  but  at  certain  times  it  is  heated  one  or  two 
degrees  above  the  temperatures  it  shows  at  those  times,  so  that  the  smaller  crystals  formed,  and  these  only, 
are  redissolved.  When  the  mass  has  been  cooled  to  35°,  the  crystalline  blocks  are  crushed  and  centrifugcd, 
the  amount  required  (25  to  30  per  cent.)  to  induce  the  molasses  (see  above)  to  crystallise  being  previously  removed. 

In  the  Grosse  process,  the  mass  is  kept  in  motion  by  a  vertical  Archimedean  screw  rotating  in  the  vacuum 
pan.  With  this  procedure,  crystallisation  takes  place  in  48  hours  and,  after  cooling  to  40°,  the  crystalline  mass 
is  disintegrated  and  centrifuged. 

Loblich,  Zschene,  Stenzel,  and  others  have  tried  mixing  the  molas«es  with  fresh  juice  and  defecating  the 
mixture  in  the  ordinary  way,  but  this  process  does  not  seem  to  offer  any  great  advantage. 

1  The  rendement  expresses  the,  percentage  of  refined  sugar  obtainable  from  the  raw  sugar  and  is  determined 
indirectly  on  the  assumption  that  every  1  part  of  ash  diminishes  the  refined  sugar  by  5  parts  ;  thus  a  raw  sugar 
containing  96  per  cent,  of  pure  sugar  and  0-4  per  cent,  of  ash  would  give  a  rendement  of  96— (0-4  x  5)  =  94  per 
cent.  The  rendement1  is  regarded  as  low  if  it  is  less  than  94  per  cent. 

s  Revivification  of  Animal  Charcoal.  The  charcoal  is  first  treated  with  hydrochloric  acid  to  remove  the 
calcium  carbonate,  and  if  more  than  1-5  per  cent,  of  calcium  sulphate  then  remains,  this  is  eliminated  by  means 
of  hot  soda  solution.  After  washing,  the  wet  charcoal  is  allowed  to  ferment  (first  alcoholic  fermentation  sets  in 


FIG.  340. 


SUGAR-REFINING 


471 


It  is  then  allowed  to  flow  into  conical  copper  moulds  with  their  apices,  closed  by  plugs, 
underneath.  The  mass,  which  has  just  begun  to  crystallise,  is  well  stirred,  and  when  it  has 
assumed  a  certain  consistency  it  is  left  at  rest  at  a  temperature  of  35°,  so  that  all  the 
molasses  collects  at  the  bottom  and  can  be  discharged  by  removing  the  plug.  In  order  to 
remove  the  molasses  completely,  the  sugar-loaves  with  their  casings  are  introduced  into 
the  moulds  of  a  Fesca  centrifuge  (Fig.  341),  which  holds  sixteen  of  them,  arranged  alter- 
nately in  two  superposed  series  of  eight. 
The  point  of  the  sugar-cone  communicates 
with  the  aperture,  b',  of  the  drum  of  the 
centrifuge,  and  when  the  latter  is  charged 
it  is  fitted  in  the  middle  with  a  cylinder, 
hh'  k,  which  rotates  with  the  drum  and  is 
provided  with  channels,  8,  communicating 
with  all  the  cones,  so  that  the  covering 
solutions  (see  above)  may  be  run  in  from  the 
tank,  r.  These  solutions  consist  of  three  or 
four  pale  syrups  and  three  or  four  concen- 
trated solutions  of  pure  sugar.  In  order  to 
remove  the  last  traces  of  yellow  colour  from 


the  sugar  and  to  blue  it  slightly,  as  is 
sometimes  required,  the  final  covering  syrup 
is  mixed  with  a  minimal  amount  of  ultra- 
marine (5  grins,  per  100  quintals  of  sugar) 
or  methyl  or  ethyl  violet  or,  better  still, 
according  to  a  recent  suggestion,  indan- 
FIG.  341.  threne.  The  white  loaves  thus  obtained  are 

then    dried     in    suitable    chambers    or    in 

revolving  apparatus,  at  a  temperature  of  55°. 

To  obtain  white  sugar  directly,  the  final  massecuite  is  sometimes  decolorised  with  30  to 

50  grins,  of  blankite  per  hectolitre  (see  Note,  p.  444  ;  blankite  is  pure,  crystallised  sodium 

hydrosulphite,  the  use  of  which  is  rapidly  extending  in  sugar-works  ;  see  vol.  i,  p.  465). 
The  beet-sugar  of  commerce  should  always  have  a  very  faint  alkaline  reaction  (towards 

phenolphthalein),  since  otherwise  it  undergoes  partial 

inversion.     Cane-sugar,  however,  has  usually  a  slight 

acid  reaction. 

Cube  sugar  was  formerly  obtained  by  sawing  the 

large  blocks,  this  entailing  considerable  loss.     But  at 

the   present  time  suitable  centrifuges  (Adant  type, 

Figs.  342  and  343)  yield  directly  long  rods  of  sugar 

of   the  requisite  thickness,  these    being  then   sawn 

with  a  minimum  of  loss.    A  platform,  F,  carries  eight 

vertical  prisms,  o,  furnished  with  screws  by  which 

they  are  fixed  to  an  upper  annular  disc.    The  latttr 

is    slotted  (c)  to   allow  of    massecuite  being  intro- 
duced into   the   chambers  (a  a)  remaining   between 

each  prism  and  the  next,  and  divided  into  a  number  FIG.  342. 

of    tall    narrow    chambers    by   plates    fixed   in   the 

grooves,   6.     The  platform  is    introduced  into  the  cylinder,   H,  which  fits  tightly  the 

periphery  of   the  moulds,  these    being  closed  inside  by  a  second  cylinder.       All  the 

then  acid  fermentation  and  finally  putrefaction),  and  is  afterwards  washed  thoroughly  with  water,  treated  with 
steam,  dried  and  gently  ignited  in  long  cast-iron  tubes,  C  (Fig.  344),  which  are  heated  to  about  400°  by  the  gases 
from  the  furnace,  A,  access  of  air  to  the  retorts  being  excluded.  The  cooled,  free  portions  are  then  gradually 
discharged  from  the  lower  parts  of  the  retorts  (E)  into  covered  metal  waggons,  so  that  the  charcoal,  which  is  still 
not  quite  cold,  may  not  take  fire  in  the  air.  The  discharge  of  the  putrid  washing  water  from  the  fermented  char- 
coal into  rivers  causes  serious  inconvenience,  and  nowadays  this  water  is  either  passed  on  to  the  soil  or  subjected 
to  biological  purification  (see  vol.  i,  p.  222). 

The  plant  for  decolorising  with  animal  charcoal  and  the  revivifying  furnaces  are  very  costly,  a  large  amount 
of  the  charcoal  at  20s.  to  24s.  per  quintal  being  required.  In  1908,  Germany  imported  51,666  quintals  of  animal 
charcoal  and  exported  35,019,  while  in  1900  the  imports  and  exports  were  39,839  and  32,018  quintals  respectively. 

Italy  imported  4756  quintals  in  1908  ;   6789  in  1909  ;  and  9863,  costing  £15,780,  in  1910. 

Soxhlet  avoids  the  carbon  decolorising  plant  by  using  filter-presses  the  chambers  of  which  are  filled  with  a 
cake  composed  of  wood-meal  mixed  with  various  indifferent  materials  (ground  coke  or  pumice,  &c.).  By  this 
means  sugar  solutions  can  be  decolorised  moderately  well  even  in  the  cold. 


472 


ORGANIC    CHEMISTRY 


chambers  are  filled  with  massecuite  introduced  through  the  slots,  c,  the  whole  being 
allowed  to  cool  for  12  to  14  hours  with  occasional  shaking.  After  complete  crystallisa- 
tion, the  whole  platform  is  withdrawn  by  the  crane/Cr,  and  placed  in  the  centrifuge,  D, 


FIG.  343. 

which  makes  about  700  revolutions  per  minute.  The  covering  is  effected  at  a  reduced 
velocity  with  sugar  solutions  entering  by  the  tube,  C,  from  a  reservoir  at  a  height  of  5 
metres.  After  the  sticks  of  sugar  have  been  removed,  the  platform  and  moulds  are  washed 
with  water  and  are  then  ready  to  receive  a  fresh  quantity  of  massecuite. 


FIG.  344.  N 

Pile  or  crushed  sugar  is  obtained  in  a  more  simple  manner  by  covering  the  crystalline 
sugar  (from  massecuite)  in  the  centrifuge  itself  by  means  of  water,  steam,  or  pure  Migar 
solution.  Slight  prolongation  of  the  centrifugation  yields  a  hard,  compact  mass,  which 
is  removed  in  large  blocks  and  broken  into  small  irregular  pieces  (pile  sugar)  by  a  special 
crusher  having  an  indented  drum  (Fig.  345). 


UTILISATION    OF    MOLASSES 


473 


FIG.  345. 


Powdered  sugar  or  farin  is  obtained  by  grinding  lump  sugar  and  any  scraps  between 
two  smooth,  horizontal  rollers  (d  and  d',  Fig.  346)  which  are  brought  near  to  one  another 
by  springs  and  are  furnished  with  scrapers,  /,  to  detach  the  powdered  sugar  ;  the  latter  is 
subsequently  sieved.  Powdered  sugar  can  also  be  obtained  by  means  of  the  Excelsior  mill 
(see  Fig.  162,  p.  168),  which  yields  as  much'as  2000  kilos  per  hour  of  a  sugar  not  too  finely 
powdered. 

UTILISATION  OF  MOLASSES.  The  processes  employed  for  the  extraction  of  beet- 
sugar  yield  about  3  per  cent,  (of  the  weight  of  beets)  of  molasses,  i.e.  of  dense,  dark-coloured 

syrups,  containing  40  to  50  per  cent,  of  sugar. 
This  does  not  crystallise  owing  to  the  presence 
in  the  molasses  of  8  to  10  per  cent,  of  mineral 
salts,  which  prevent  about  five  times  their 
weight  of  sugar  from  crystallising.  So  that,  in 
general,  it  is  difficult  or  almost  impossible  to 
extract  sugar  by  direct  crystallisation  from 
syrups  with  a  degree  of  purity  less  than  60  to 
65  per  cent.  The  percentage  composition  of 
molasses  varies  between  the  following  limits  : 
water,  19  to  28  (mean,  23)  ;  sugar,  45  to  54 
(mean,  48) ;  solids  not  sugar,  26  to  29  (mean, 
28)  ;  ash,  6  to  8  (mean,  7 ;  largely  potassium 
salts) ;  invert  sugar,  1-25  to  1-85  (mean,  1-65). 
The  degree  of  purity  ranges  from  62  to  67 
per  cent,  (mean,  64  per  cent.).  The  com- 
positions of  various  Italian  molasses  have  been  given  in  the  Note  on  p.  140. 

The  recovery  of  the  sugar  from  molasses  involves  indirect  processes  which  are  not 
always  convenient  in  practice,  and  when  this  is  the  case  the  molasees  is  employed  for  the 
manufacture  of  cattle-food  or  spirit  (see  p.  140).  In  spirit  factories  the  molasses  is  diluted 
to  12°  to  14°  Be.  (about  15  per  cent,  of  sugar),  when  it  can  be  fermented  (see  p.  140). 
100  quintals  of  molasses  yield  23  to  25  hectols.  of  alcohol  (calculated  as  anhydrous  spirit) 
and  1800  kilos  of  C02.  The  potassium  salts  are  extracted  from  the  residual  vinasse  by  the 
process  described  in  vol.  i,  p.  435. 
100  kilos  of  molasses  give  35  kilos 
of  concentrated  vinasse  (40°  Be.), 
and  by  calcining  this  10  kilos  of 
vinasse  charcoal  are  obtained.  In 
some  factories  the  vinasse  is  now 
treated  for  the  recovery  of  the 
ammonia  and  fatty  acids  by  the 
Effront  process  described  on  p.  155, 
without,  however,  losing  the  potas- 
sium salts.1 

In  Italy,  before  the  modification 
of  the  fiscal  regulations  which 
taxed  the  defecated  saccharine 

1  The  molasses  vinasse  remaining  after 
the  distillation  of  the  alcohol  has  a  density  of 
about  4°  B6.  and  contains  6  to  7  per  cent,  of 
solids.  When  utilised,  it  is  first  concentrated 
to  40°  Be1.  (100  kilos  of  molasses  give  35  kilos 

of  this  concentrated  vinasse),  when  it  contains  75  per  cent,  of  solids  with  about  4  per  cent,  of  nitrogen.  About 
one-half  of  the  solid  substances  are  nitrogenous  compounds.  The  solids  contain  10  to  12  per  cent,  of  betaine, 
5  to  7  per  cent,  of  glutamic  acid,  and  1  to  2  per  cent,  of  leucine  and  isoleucine,  besides  varying  quantities  of  amino- 
acids  and  nuclein  bases  ;  the  non-nitrogenous  constituents  consist  of  about  15  per  cent,  of  fatty  acids  (formic, 
acetic,  lactic,  butyric,  and  homologous  acids),  and  15  to  20  per  cent,  of  other  organic  compounds  not  com- 
pletely investigated.  Effront  thinks  it  possible,  from  100  quintals  of  molasses,  to  obtain  75  kilos  of  ammonium 
sulphate  and  95  to  120  kilos  of  fatty  acidS,  by  the  action  of  yeasts  which  decompose  the  amino-acids  into  ammonia 
and  fatty  acids,  separable  by  distillation.  But,  according  to  P.  Ehrlich,  yeasts  transform  amino-acids  into  alcohol 
and,succinic  acid,  the  formation  of  ammonia  and  fatty  acids  being  clue  not  to  yeasts  but  to  butyric  and  other 
bacteria  which  always  occur  with  yeasts,  and  decompose  the  amino-acids  into  ammonia,  fatty  acids,  and  various 
amines  just  as  in  ordinary  putrefaction.  Hence  the  effect  of  the  Effront  process  could  also  be  obtained  by  adding 
to  the  aqueous  vinasse  a  little  putrefied  meat  and  allowing  putrefaction  to  proceed.  The  manipulation  of  large 
masses  of  putrefied  liquid  would  not,  however,  be  very  agreeable  or  hygienic. 


FIG.  346. 


474 


ORGANIC    CHEMISTRY 


juices  directly  and  left  untaxed  the  sugar  in  the  molasses,  various  factories  applied  certain 
of  the  chemical  and  physical  methods  used  in  other  countries  for  the  extraction  of 
the  sugar  from  molasses — by  means  of  osmosis,  lime,  strontia,  baryta  (formerly  by  means 
of  alcohol),  &c.  When  these  methods  (see  later)  are  used,  it  is  calculated  that  the  final 
molasses  does  not  exceed  0-5  to  1  per  cent,  of  the  weight  of  the  original  beets. 

In  Italy  the  amount  of  molasses  produced  annually,  including  that  from  refineries,  is 
300,000  to  350,000  quintals,  which  is  utilised  almost  entirely  in  spirit  factories,  60  kilos 
of  anhydrous  alcohol  being  obtained  from  100  kilos  of  sugar.  Germany  produces  about 
4,000,000  quintals,  2,200,000  being  desaccharified  by  means  of  strontium,  1,250,000  uped 
as  fodder,  and  350,000  utilised  by  spirit  factories.  In  1908  England  imported  84,128  tons 
for  making  spirit  and  cattle-food.  In  France,  346,000  quintals  of  molasses  were  returned 
to  the  agriculturist  in  1907. 

(1)  Osmosis  Process.  This  was  first  proposed  by  Dubrunfaut  in  1863,  and  is  based  on 
the  osmotic  properties  of  crystalloids,  which  pass  through  a  membrane  immersed  in  water 
(see  vol.  i,  p.  102).  But  different  crystalloids  traverse  the  membrane  at  varying  speeds, 
the  sugar,  for  instance,  far  more  slowly  than  salts.  Hence,  if  the  molasses  is  placed  in  a 
dialyser  and  surrounded  with  water,  after  a  time  the  water  will  contain  more  salts  than 


FIG.  347. 


sugar,  while  the  molasses  will  be  diluted  with  water  but  will  contain  relatively  more  sugar 
and  less  salts  than  at  first. 

The  apparatus  now  used  for  osmosis  (Fig.  347)  consists  of  a  series  of  wooden  frames 
4  cm.  in  thickness  and  of  the  size  of  those  used  in  filter-presses  ;  these  are  separated  by 
sheets  of  parchment  paper,  the  whole  being  pressed  tightly  together.  The  compartments 
thus  formed  are  filled  alternately  with  water  and  molasses.  The  upper  part  of  the  whole 
of  the  osmogen  constitutes  an  open  reservoir  formed  by  the  upper  vertical  projections  of 
the  frames.  The  molasses  for  feeding  the  alternate  chambers  is  placed  in  this  reservoir 
and  is  kept  circulating  in  various  ways.  The  water  chambers  are  fed  from  the  lower  part 
and  are  discharged  through  a  common  upper  tube  as  they  become  enriched  with  salts. 

The  osmotic  effects  occur  best  in  the  hot,  so  that  the  molasses  is  introduced  at  80°  and 
the  water  at  90°. 

The  taps  through  which  the  liquids  enter  and  leave  the  osmogen  are  regulated  by 
automatic  floats,  which  close  or  open  the  taps  more  or  less  so  as  to  maintain  a  constant 
relation  between  the  density  of  the  exosmosed  aqueous  solution  and  that  of  the  osmosed 
molasses.  This  relation  is  determined  beforehand  in  the  laboratory,  and  corresponds  with 
the  conditions  least  favourable  to  the  loss  of  sugar  with  the  osmosis  water  and  most  favour- 
able to  the  purity  of  the  residual  molasses. 

The  exosmosed  water  generally  has  a  density  of  3°  Brix  (3  per  cent,  of  sugar  and  salt 
together),  and  the  osmosed  molasses  35°  to  40°  Brix  (measured  at  75°  C.)  ;  the  latter  is 
concentrated  and  boiled  in  ordinary  syrup  pans  until  it  shows  the  string  test.  Crystallisa- 
tion is  carried  out  in  the  molasses  room  at  40°  to  45°  or  in  the  Grosse  apparatus.  The 
crystallised  sugar  is  separated  by  centrifugation  and  the  new  molasses  obtained  again 
subjected  to  osmosis.  This  operation  is  repeated  once  or  twice  more — in  fact,  until  the 


SUGAR    FROM    MOLASSES 


475 


quantity  of  sugar  extracted  would  be  insufficient  to  pay  the  cost.  In  some  cases  the 
osmosis  waters  are  concentrated  and  reosmosed. 

The  final  molasses  and  the  final  osmosis  waters — rich  in  salts  and  also  in  sugar — serve 
for  making  spirit,  shoe -polish,  or  potassium  salts  (see  p.  155).  They  are  also  given  to  cattle, 
but  must  then  be  diluted  with  solid  vegetable  products  as  an  excess  of  salts  may  exert 
harmful  effects. 

(2)  Lime  Process.  Steffen  found  that  the  addition  of  finely  powdered,  sieved  quicklime 
in  small  portions  to  a  solution  of  molasses  of  a  suitable  concentration  (about  12°  Brix, 
i.e.  1  per  cent,  of  sugar,  obtained  from  1  quintal  of  molasses  +  7  hectols.  of  water),  and 
kept  at  a  temperature  below  15°,  results  in  the  separation  of  insohible  sucrate  containing 
rather  more  lime  than  tricalcium  sucrate,  whilst  the  impurities  remain  dissolved  in  the 
aqueous  molasses. 


FiG.  348. 


FIG.  349. 


The  operation  is  carried  out  in  a  vessel  (Figs.  348,  349)  similar  to  the  Grosse  apparatus, 
the  steam-pipes  being  used,  however,  for  the  circulation  of  cold  water  at  about  12°,  so 
that  after  each  addition  of  lime,  when  the  temperature  rises  7°  to  8°,  it  can  be  brought 
rapidly  down  below  15°.  The  addition  of  lime  is  continued  until  all  the  sugar  is  precipi- 
tated (about  100  kilos  of  lime  per  100  kilos  of  sugar),  this  being  ascertained  by  reading 
the  clear  liquid  in  the  saccharometer. 

The  resultant  sludgy  mass  is  filter-pressed  at  a  pressure  not  exceedingly  atmosphere, 
the  filtrate  still  containing  about  0-5  per  cent,  of  sugar,  which  can  be  separated  as 
tricalcium  sucrate  by  heating  the  liquid  to  90°  and  filtering. 

The  cakes  of  sucrate  are  washed  several  times  in  the  filter-press  and  the  fairly  pure 
residue  used  to  defecate  fresh  diffusion  juice  before  saturation  with  carbon  dioxide  ;  or 
the  sucrate  can  be  treated  with  any  cold  saccharine  solution  so  as  to  form  the  soluble 
monosucrate,  the  precipitated  excess  of  lime  being  removed  by  filtration_and  the  filtrate 
then  saturated  with  carbon  dioxide  in  the  ordinary  manner. 

(3)  Strontia  Process.  When  an  excess  of  crystallised  strontium  hydroxide  is  added 
to  a  dilute  sugar  solution  at  a  temperature  of  about  100°  and  the  liquid  boiled,  a  granular, 


476 


ORGANIC    CHEMISTRY 


sandy  precipitate  of  strontium  disucrate  is  obtained,  which  is  stable  in  the  hot  whilst  in 
the  cold  it  decomposes  into  sugar  and  strontium  hydroxide. 

In  a  suitable  boiler  provided  with  steam-coils  and  stirrers,  a  10  per  cent,  solution  of 
strontium  hydroxide  is  boiled,  further  quantities  of  the  hydroxide  being  added  until  a 
20  to  25  per  cent,  solution  is  obtained.  The  molasses  is  now  added  in  amount  equal  to 
about  one-third  of  that  of  the  strontium  solution,  which  is  stirred  rapidly  and  heated 
meanwhile.  Strontium  hydroxide  is  subsequently  introduced  in  such  amount  that  the 
mass  has  12  to  13  per  cent,  of  excess  alkalinity.  The  total  strontium  hydroxide  is  related 
to  the  sugar  in  the  molasses  in  about  the  proportion  2-5  :  1. 

The  precipitated  disucrate  is  filtered  rapidly  in  the  hot  through  bag-filters  and  washed 
with  boiling  10  per  cent,  strontium  hydroxide,  the  latter  being  jrecovered  from  the  filtrate. 
The  disucrate  is  then  dissolved  in  a  cold  strontium  hydroxide  solution  and  the  solution 
introduced  into  metallic  vessels  situate  in  an  apartment  kept  below  10°.  In  the  course 
of  three  days  one-half  of  the  hydrate  separates  in  a  crystalline  form,  the  saccharine  solu- 
tion being  then  decanted  and  the  residue  centrifuged.  The  sugar  solution  is  then  saturated 
with  carbon  dioxide  until  it  shows  an  alkalinity  of  0-05,  all  the  strontium  being  thus 
separated  as  carbonate.  The  very  pure  sugar  solution  obtained  after  filtration  is  concen- 
trated and  boiled  as  usual,  the  crystallised  sugar  obtained  being  placed  directly  on  the 
market  without  being  refined. 

A  somewhat  different  mode  of  procedure  is  that  based  on  the  formation  of  strontium 
monosucrate,  but  this  does  not  yield  the  whole  of  the  sugar  as  the  above  process  does. 
In  Germany  the  desaccharification  of  molasses  is  effected  almost  exclusively  with  strontia 
in  large  works  specialising  in  such  work. 

(4)  Baryta  Process.  When  solutions  of  molasses  and  of  barium  hydroxide  are  mixed 
in  the  hot  in  the  proportion  of  1  mol.  of  sugar  to  1  mol.  of  the  hydroxide,  a  heavy,  sandy 
precipitate  of  barium  monosucrate  is  formed  which  is  stable  to  either  hot  or  cold  water  ; 
this  is  collected  as  usual  on  filters  and  freed  from  impurities  by  washing  with  cold  water. 
It  is  then  saturated  with  carbon  dioxide  in  order  to  liberate  the  sugar  and,  after  dilution 
with  other  sugar  juices,  is  filtered,  concentrated,  and  crystallised.1 

YIELD  AND  COST  OF  PRODUCTION.  Formerly  a  hectare  of  land  yielded  with 
difficulty  200  quintals  of  beet,  but  as  the  result  of  long-continued  improvement  of  the 
methods  of  cultivation,  manuring,  selection  of  seed,  &c.,  as  much  as  300  to  400  quintals 
are  now  obtained,  and  in  certain  special  regions  (e.g.  Ferrarese)  as  much  as  600  to  650. 

Italy  contains  20,000,000  hectares  of  cultivated  land  (excluding  forests),  5,000,000  being 
under  corn,  1,600,000  under  maize,  and  only  50,000  under  beet,  the  yields  being  as  follows  : 


Hectares  under 
beet 

Mean  production 
per  hectare 

Mean  price  per 
quintal 

Mean   quantity  of 
sugar  per  100  kilos 
of  beet 

1905-1906 

37,500 

Quintals 

253 

Shillings 
2-01 

Kilos 
12-24 

1906-1907 

37,954 

271 

2-02 

13-56 

1907-1908 

41,000 

307 

2-15 

13-98 

1908-1909 

51,000 

280 

— 

13 

1909-1910 

36,000 

— 

— 

— 

1910-1911 

50,000 

— 

—  • 

— 

For  every  quintal  of  beet  worked,  the  loss  is  calculated  to  be  1-6  kilo  of  sugar  in  Italy 

1  The  barium  carbonate  filtered  off  is  converted  into  the  oxide  and  then  into  the  hydroxide  by  heating  in 
suitable  high-temperature  furnaces  (see  vol.  i,  p.  502). 

This  barium  process  was  used  for  some  time  in  Italy,  after  it  had  been  shown  that  no  danger  to  health  was 
to  be  feared  from  the  use  of  a  barium  compound,  since  this  is  eliminated  completely  by  carbon  dioxide  and  the 
final  traces  by  calcium  sulphate.  The  barium  hydroxide  required  is  imported  principally  from  America  and 
Germany  ;  but  by  1903,  four  factories  had  been  erected  in  Italy  for  supplying  all  the  baryta  necessary  to  the 
sugar  factories.  One  of  these  factories,  at  Calolzio,  starts  from  barium  sulphate  ;  another,  at  Milan,  heats  the 
barium  carbonate  from  the  sugar-works  ;  while  the  remaining  two,  at  Foligno  and  Pont  St.  Martin  respectively, 
treat  barium  carbonate  in  electric  furnaces,  making  first  barium  carbide,  which  with  water  gives  acetylene  and 
barium  hydroxide  (Garelli's  process). 

Such  treatment  of  molasses  in  Italy  was  found  feasible  as  long  as  the  sugar  extracted  in  this  way  remained 
free  from  taxation,  that  is,  while  the  tax  was  levied  solely  on  the  defecated  diffusion  juice.  But  since  1904,  the 
total  quantity  of  sugar  produced,  including  that  extracted  from  molasses,  has  been  liable  to  duty,  and  the  molasses 
is  consequently  utilised  in  the  distillery  and  in  the  manufacture  of  cattle-food.  But  recently  some  sugar  factories 
have  resorted  to  treatment  of  the  molasses  with  barium  sulphide,  which  is  much  cheaper  than  the  hydroxide 
and  is  obtained  directly  from  the  sulphate  in  the  electric  furnace. 


SUGAR    STATISTICS  477 

and  only  1  kilo  in  Germany.  The  cost  of  cultivating  1  hectare  of  beet,  including  manure, 
transport,  &c.,  amounts  to  £12. 

Italian  manufacturers  calculate  that  in  bad  seasons  the  production  of  100  kilos  of  refined 
sugar  requires  10  quintals  of  beet,  the  cost  of  working  these  being  Is.  to  Ss.  (including  3s. 
for  coal).  Refining  costs  about  5s.  6d.  (100  kilos  of  raw  sugar  give  about  90  of  refined). 

In  Germany  100  kilos  of  beet  gave  not  more  than  8-4  of  sugar  in  1870,  about  12-5  in 
1890,  and  15-8  (including  that  from  the  molasses)  in  1909-1910.  The  mean  production 
per  hectare  was  246  quintals  of  beet  in  1871  and  300  in  1910. 

The  consumption  of  coal  in  working  100  kilos  of  beet  in  Germany  was  35  kilos  in  1867, 
24  kilos  in  1877,  10  kilos  in  1890,  and  7  kilos  (8  in  Italy)  in  1900.  By  the  use  of  Kestner 
concentrators  (see  above)  a  further  saving  in  coal  has  recently  been  effected. 

Every  100  kilos  of  beet  treated  yield  3  kilos  of  molasses  (including  0-5  kilo  from  the 
refining  process)  containing  45  to  50  per  cent,  of  sugar. 

Each  quintal  of  beet  gives  80  kilos  of  exhausted  and  pressed  pulp  or  slices  containing 
70  per  cent,  of  water. 

The  cost  of  manufacturing  100  kilos  of  cane-sugar  in  Java  varies  from  12s.  to  16s., 
and  transport  to  England  or  the  United  States  amounts  to  2s.  per  quintal. 

STATISTICS.1  The  history  of  the  development  of  the  sugar  industry  in  Europe  and 
the  importance  this  industry  has  assumed  during  the  past  quarter  of  a  century  have  already 
been  discussed  on  p.  448.  Reference  has  also  been  made  to  the  production  of  cane-sugar 
compared  with  that  of  beet-sugar.  While  in  1854  beet-sugar  formed  only  14  per  cent,  of 
the  world's  total  production  (1,423,000  tons),  in  1866  the  proportion  was  30  per  cent,  (on 

1  The  Commercial,  Customs,  and  Fiscal  Conditions  of  the  sugar  industry  in  Italy  and  other  countries. 
In  some  countries  this  great  industry  has  been  extended  artificially  owing  to  the  direct  and  indirect  help  afforded 
by  the  State,  and  to  the  speculations  of  financiers.  \Vith  the  excuse  of  protecting  national  industries,  Govern- 
ments have  levied  heavy  Customs  duties,  with  the  result  that  the  public  has  paid  dearly  for  its  sugar,  while  manu- 
facturers have  accumulated  enormous  profits  and  have  been  enabled  to  export  sugar  at  less  than  cost  price  to 
other  countries.  At  first  the  protective  duty  was  from  24s.  to  32s.  per  quintal,  while  in  France  it  was  raised 
to  64s.  The  form  taken  by  the  protection  was  then  changed  by  the  institution  of  export  bounties,  which  allowed 
the  sugar  to  be  sold  abroad  at  a  low  price,  while  large  profits  were  made  owing  to  the  high  prices  at  home  and 
to  the  bounties.  First  Belgium  and  then  France  established  a  bounty  of  8s.  to  10s.  for  every  quintal  of  sugar 
exported,  France  being  thus  subjected  to  an  enormous  burden  amounting  to  over  £2,000,000,  without  counting 
the  rebate  on  the  freight  from  the  factory  to  the  frontier.  This  enormous  sum  has  been  paid  by  the  mass  of  the 
population,  to  the  exclusive  advantage  of  a  few  manufacturers  (rule  of  the  Meline  Ministry). 

In  Germany  and  Austria,  where  the  export  bounties  were  relatively  low,  the  manufacturers  formed  sale 
syndicates  (cartels),  which  operated  in  the  following  manner :  the  manufacturers  pledged  themselves  to  supply 
all  the  raw  sugar  to  the  refiners,  who  granted  a  bounty  of  24s.  per  quintal  to  the  manufacturer  and  sold  the  sugar 
to  the  home  consumer  at  a  very  high  price,  there  being  no  fear  of  competition,  as  they  enjoyed  a  monopoly.  The 
sufferers,  as  always,  were  the  consumers.  The  home  profits  were  so  enormous  that  sugar  could  be  sold  abroad 
at  less  than  cost  price  and  competition  thus  vanquished.  On  the  other  hand,  England,  the  greatest  consumer 
of  sugar,  found  its  markets  deluged  with  cheap  Continental  sugar,  which  competed  seriously  with  that  from  its 
Colonies,  which  had  also  become  considerable  exporters. 

Under  these  conditions  a  more  rational  solution  was  found  for  the  problem  of  sugar  with  reference  to  inter- 
national commerce.  The  initiation  of  such  an  undertaking  could  come  only  from  England,  who  was  able  finally 
to  impose  her  conditions  on  all  countries  sending  sugar  to  her  markets.  The  Brussels  Convention,  convoked 
on  September  1,  1902,  was  subscribed  to  by  England,  Germany,  Austria,  France,  Belgium,  Holland,  and  Italy. 
The  result  was  the  abolition  of  export  premiums  and  the  reduction  of  the  boundary  duty  to  5s.  per  quintal  above 
the  manufacturing  tax,  from  September  1,  1903,  onwards.  Such  duty  was  to  be  enjoyed  only  by  those  countries 
conforming  to  the  Brussels  Convention. 

Italy  did  thus  conform  in  a  modified  way  :  the  boundary  duty  remained  as  before,  namely,  23s.  for  first  quality 
and  16s.  6d.  for  second  quality,  while  a  pledge  was  given  not  to  export  sugar  to  other  countries  and  to  impose 
an  exceptionally  heavy  Customs  duty  on  countries  not  adhering  to  the  Brussels  Convention  (especially  on  Russia 
and  the  Argentine  Republic ;  but  Russia  entered  the  Convention  in  January  1908,  and  pledged  herself  to  export 
for  six  years  not  more  than  200,000  tons  per  annum  of  bounty-fed  sugar.  After  1908  England  held  herself  free 
to  import  premiumed  sugar  without  imposing  supertaxation).  Spain  and  Sweden  were  treated  like  Italy  by 
the  Brussels  Convention,  to  which  then  Luxemburg,  Peru,  and  Switzerland  conformed.  In  Spain  there  is  now 
an  overproduction  crisis. 

This  is  the  regime  now  in  force  in  Europe.  But  in  Italy  the  price  of  sugar  fell,  owing  to  overproduction  and 
frenzied  competition,  to  92s.  per  quintal,  so  that  in  1901-1903  almost  all  the  sugar  factories  showed  either  minimal 
profits  or  considerable  losses.  Indeed,  deducting  the  tax  of  56s.,  there  remains  36s.  as  the  price  of  the  sugar. 
And,  according  to  the  manufacturers,  10  quintals  of  beet,  giving  1  of  sugar,  cost  16s.,  while  the  cost  of  production 
of  crude  sugar  is  8s.  (including  4s.  for  coal),  that  of  refining  about  6s.  4d.  and  that  of  transport  Is.  8d :  total, 
32s.  Thus  only  4s.  remains  to  provide  interest  on  capital  as  well  as  depreciation.  Hence,  in  1904,  all  the  sugar- 
makers  combined  to  fpym  a  syndicate  and  raise  prices,  and  early  in  1905  an  increase  of  16s.  (to  108s.)  per  quintal 
was  enforced ;  with  a  production  of  1,000,000  quintals,  this  amounted  to  an  annual  burden  on  the  consumer  of 
£800,000.  Adding  to  this  the  protective  duty  of  £1,200,000,  it  will  be  seen  that,  for  the  luxury  of  a  native  sugar 
industry,  the  Italians  pay  an  annual  tax  of  £1,200,000  to  £2,000,000,  the  sole  gainers  being  some  30  factories  with  a 
capital  of  about  £3,200,000  ;  this  in  spite  of  the  fact  that  Germany  and  Austria  would  supply  sugar  at  24s.  to  26s. 
per  quintal,  so  that,  leaving  aside  the  taxation  of  £2,800,000,  sugar  could  be  sold  at  IQd.  instead  of  15d.  per  kilo. 

The  sugar  manufacturers  state  that,  owing  to  various  causes,  their  capital  yields  on  an  average  only  6  per 
cent.  But  it  can  only  be  regarded  as  a  mistake  to  keep  an  industry  alive  under  such  artificial  conditions,  when 
the  consumer  evidently  suffers  considerable  injury  and  the  advantage  to  the  agriculturist  and  the  operative  is 
doubtful  and  in  any  case  mipinia.!. 

Attempts  recently  made  to  remedy  this  state  of  affairs  have  been  unsuccessful. 


ORGANIC    CHEMISTRY 

a  total  of  2,000,000  tons) ;  in  1878,  44  per  cent,  (on  3,000,000  tons) ;  in  1887,  47  per  cent, 
(on  more  than  5,000,000  tons)  ;  in  1893,  55  per  cent,  (on  about  6,000,000  tons)  ;  in  1899, 
64*per  cent,  (on  7,500,000  tons)  ;  in  1901,  67  per  cent,  on  almost  9,000,000  tons.  In  1C09- 
1910  cane-sugar  again  assumed  first  place,  constituting  53-5  per  cent,  of  the  total  world's 
production  of  nearly  15,000,000  tons.  In  Europe  the  total  area  under  beet  is  about  2,000,000 
"hectares,  about  43,000  hectares  being  in  Italy. 


Country  and  year 

No.  of 

factories 

Production  of 
beets  (b)  or 
sugar-cane  (c) 

Output  of 
raw  sugar 

Remarks 

Europe 

Tons 

Tons 

Germany  .          .   1903 

384 

12,171,000      b 

2,293,000 

In  1907,  417  factories  and  refineries 

worked  14,187,000  tons  of  beet, 

obtaining  1,950,000  tons  of  raw 

sugar.     In   1905-1906  the  pro- 

duction was  2,400,000  tons,  and 

in  1909-1910,  2,037,400  tons 

Austria-Hungary  1903 

215 

7,542.600      ft 

1,290,000 

355,000    tons    in    1886  ;    665,000 

. 

8,507,000  in  1908 

in    1894  ;     865,000    in    1900  ; 

1,334,000    in    1906;     1,259,000 

tons  in  1909-1910 

France      .         .  1903 

296 

6,315,300       6 

1,080,000 

Equal  to  694,000  tons  of  refined  ; 

807,500  in  1909 

in  1904,  540,000  tons 

Russia       .         .  1903 

275 

7,604,000       6 

1,000,000 

425,000  in  1887  ;  578,  JOO  in  1894  ; 

8,800,000  in  1908 

1,300,000   in    1906;    1,144,000 

tons  in  1909-1910 

Belgium    .          .   1903 

100 

1,645,000       b 

325,000 

241,000  in  1909-1910 

Holland    .         .  1903 

29 

1,023,000       b 

204,000 

175,000  in  1909-1910 

Italy         .          .  1909 

31 

1,050,000       b 

165,000 

Or  150,000  refined 

Spain        .         .1904 

32 

580,000       6 

64,300 

69,000  in   1905;    103,340  (in   49 

factories)  in    1903  ;    86,000  in 

1910 

.   1904 

27 

250,000       c 

24,500 

After  1906  there  was  overproduc- 

tion.    Cultivated  between  Gib- 

raltar   and    Almeria  :      28,820 

tons  in  1905  ;   140,600  in  1908  ; 

22,000  in  1910 

Denmark  .         .  1903 

7 

415,000       b 

65,000 

58,500  in  1909 

Roumania          .   1904 

5 

182,700       b 

23,500 

Sweden     .          .   1909 

21 

864,400       b 

122,0(10 

Only  4000  in  1886 

America 

United  States    .   1903 

70 

1,500,000       6 

300,000 

12,000  in  1893  ;   327,000  in  1904  ; 

433,000   in    1907  ;     450,000   in 

1909-1910 

»          >»               » 

c 

170,000 

,,          „               ,, 

maple 

12,000 

5400  in  1880  ;   10,000  in  1907 

Cuba          .          .   1904 

c 

1,050,600 

1,140,000     (home      consumption, 

26,000)  in  1905-1906  ;  1,450,000 

in  1907  ;  970,000  in  1907-1908  ; 

1,520,000       in       1908  -  1909  ; 

1,459,000  in  1910-1911 

Trinidad  .         .   1906 

c 

54,000 

45,600  in  1907  ;  41,600  in  1908 

Other  Antilles,  Central 

America          .   1906 

c 

410,000 

South  America  (Dem- 

Argentine  in  1909  produced  115,000 

erara,  Peru,  Argen- 

and consumed  150,000  tons 

tine,  Brazil)   .  1902 

c 

440,000 

Mexico      .         .  1909 

c 

160,000 

143,000  (and  70,000  molasses)  in 

1908  ;      exports     £400,000     to 

£600,000 

Asia 

Java          .          .1909 

c 

1,312,466 

1,285,000  in  1907 

Philippines         .    1909 

c 

94,000  exported 

Production,  122,000  tons  in  1907 

and  138,000  in  1908 

East  Indies        .   1904 

c 

1,300,000 

Australia    .   1902 

470,000 

Africa         .   1902 

(Egypt,  Reunion,  and 

.Mauritius) 

c 

280,000 

f  45.000(1904) 

Formosa  (for  Japan) 

17 

c 

<    71,000(1906) 

1910 

1206,000(1910) 

SUGAR    STATISTICS 


479 


The  world's  production  of  sugar  and  that  of  the  various  countries  is  shown  in  the 
Table  on  the  opposite  page,  which  also  gives  the  number  of  sugar  factories.^ 

The  total  world's  production  of  sugar  is  given  by  about  1400  factories  and  300  refineries, 
and  in  1904-1905  amounted  to  11,684,000  tons  of  raw  sugar,  in  1905-1906  to  13,762,000 
tons,  in  1906-1907  to  14,420,000,  in  1907-1908  to  about  13,500,000,  and  in  1909-1910  to 
16,200,000  tons,  nine  million  tons  of  this  being  cane-sugar. 

In  Japan  a  single  refinery  at  Moji  produces  2500  quintals  of  refined  cane-sugar  daily, 
and  it  is  proposed  to  double  the  output.  Two  other  refineries  are  found  at  Osaka  and 
Tokyo  respectively.  These  work  mostly  raw  sugar  from  Java  and  export  a  considerable 
quantity  of  refined  sugar  to  China  and  Corea.  Formosa  produced  in  1907  about  70,000, 
in  1908  about  100,000,  and  in  1910  more  than  200,000  tons  of  cane-sugar. 

In  1910  the  areas  under  beet  in  the  various  countries  of  Europe  were  as  follow 
(hectares) :  Eussia,  675,000  ;  Germany,  470,000  ;  Austria-Hungary,  365,000  ;  France, 
235,000  ;  Belgium,  67,500  ;  Holland,  55,000  ;  Italy,  32,000  in  1903,  38,000  in  1906,  51,000 
in  1908,  36,000  in  1909,  50,000  in  1910  ;  Sweden,  35,000  ;  Denmark,  22,500  ;  Spain,  18,000  ; 
Roumania,  13,000  ;  Servia,  3300  ;  Bulgaria,  1700  ;  Switzerland,  950. 

To  give  an  idea  of  the  progress  made  by  the  beet-sugar  industry  during  the  last  50 
years,  the  production  of  raw  sugar  in  the  two  countries  where  this  industry  has  developed 
most  is  given  in  the  following  table  : 


In  France 

In  Germany 

Germany 

Yield  of  sugar  per 
100  kilos  beet 

Annual  consump- 
tion per  head 

Tons 

Tons 

1840      . 

22,784 

14,200 

5-9  kilos 

2-5  kilos 

1850      . 

62,165 

53,300 

7-3     „ 

3-1      „ 

1860      . 

126,480 

126,520 

8-6     „ 

4-3     „ 

1870      .      .    . 

282,136 

186,000 

8-6     „ 

4-7      „ 

1890      . 

750,000 

1,336,000 

12-5     „ 

8-5     „ 

1903      . 

1,080,000 

1,921,000 

14-4     „ 

13        „ 

1905      . 

— 

1,605,000 

14-9     „ 

14-9     „ 

1906      . 

730,000 

2,400,000 

14-7     „ 

17-0     „ 

1909      .      '  . 

807,500 

2,037,400 

16-3     „ 

19-5     „ 

The  production  in  France  varies,  since  the  agriculturists  require  as  much  as  3*.  per 
100  kilos  of  beet.  While  the  consumption  was  40,000  tons  in  1887  and  527,000  in  1902,  it 
rose  to  600,000  tons  in  1908,  owing  to  the  modification  of  the  fiscal  conditions  of  1903- 
1904.  The  number  of  workpeople  occupied  for  about  two  months  was  38,000  in  1908,  with 
an  average  wage  of  3s.  per  day.  The  area  under  beet  in  France  in  1907  was  210,000  hectares. 

Some  of  the  large  factories  in  France  and  Belgium  have  diffusion  plants  in  the  middle 
of  the  beet-growing  districts,  the  sugar  juices  after  treatment  with  lime  being  forced 
through  pipes,  often  several  kilometres  long,  to  the  factories,  where  they  are  further 
worked  up. 

In  1906  England  imported  1,583,000  tons  of  sugar,  and  in  1909  about  940,000  tons  of 
refined  and  815,000  tons  of  raw  sugar.  In  1910  the  imports  were  98,000  tons  of  raw  sugar 
and  84,400  tons  of  refined  sugar,  the  total  value  being  £24,554,000  ;  the  exports  were 
31,000  tons.  The  United  States  imported  2,095,000  tons  of  raw  sugar  and  76,000  tons 
of  refined  sugar  in  1910,  and  2,049,000  tons  (£19,873,600)  of  raw  and  160,000  tons  of  refined 
sugar  in  1911. 

In  Germany  the  beet-sugar  industry  has  reached  its  greatest  perfection  and  magnitude, 
and  from  1880  to  1902  Germany  was  the  largest  exporter  (as  much  as  two-thirds  of  its  own 
output).  In  1909-1910,  in  spite  of  the  diminution  of  exports  resulting  from  the  Brussels 
Convention,1  Germany  exported  423,000  tons  of  refined  sugar  and  310,000  tons  of  the 

1  The  Fiscal  System  in  Germany  from  1841  to  1866  was  based  on  the  quantity  of  beets,  the  object  being 
to  bring  about  improvements  in  the  cultivation  of  the  beet  and  hence  increase  in  the  sugar-content ;  the  tax 
corresponded  with  about  18s.  per  quintal,  and  was  refunded  to  the  manufacturer  for  all  exported  sugar.  From 
1870  to  1886  the  tax  was  1».  "id.  per  quintal  of  beet,  it  being  assumed  that  12-5  kilos  of  beet  were  required  to  give 


480 


ORGANIC    CHEMISTRY 


raw  product,  the  home  consumption 'being  1,260,000  tons.  The  exports  were  740,000  tons 
in  1890,  883,000  in  1904,  and  1,145,000  in  1906.  In  1908-1909,  358  factories  and  39  re- 
fineries were  working  in  Germany.  Certain  German  factories,  employing  46  workmen,  treat 
4000  to  5000  quintals  of  beet,  but  in  Italy  many  more  employees  are  required.  In  1909- 
1910  Germany  produced  10,600,000  tons  of  beet,  but  in  1910-1911  only  5,200,000  tons. 

In  Austria  large  batteries  of  diffusors  are  used  and  a  more  complete  exhaustion  is 
obtained  even  at  a  lower  temperature  ;  in  general,  indeed,  the  modern  plants  are  more 
perfect  than  those  in  Germany.  In  1908  Austria -Hungary  exported  610,000  tons  of  refined 
and  195,000  of  raw  sugar. 

The  following  Table  shows,  for  different  countries  :  I,  manufacturing  tax  in  pence  per 
kilo  ;  II,  retail  price  in  pence  per  kilo  ;  III,  mean  annual  consumption  in  kilos  per  head 
in  1899  and  1909  ;  IV,  mean  quintals  of  beet  produced  per  hectare  in  1908-1910  ;  V, 
kilos  of  refined  sugar  obtained  from  100  kilos  of  beet  ;  and  VI,  kilos  of  refined  sugar  from 
1  hectare. 


I 

II 

III 

IV 

V 

VI 

1899             1909 

England     .          . 

0-96 

5-3 

40           41-1 

— 

— 

— 

United  States     . 

0-96 

4-8 

28-4        37-2 

220 

12-44 

2706 

Switzerland 

0-67 

4-8 

25-7        30-2 

— 

— 

— 

Denmark 

0-575 

6-7 

21-6        35-5 

287 

13-82 

3950 

Sweden  and  Norway   . 

2-88 

7-7 

/24-5\ 
15'7      J17-8J 

266 

14-26 

3803 

Germany  . 

1-92 

6-2 

13-7         19-7 

284 

16-35 

4809 

Holland 

5-47 

9-6 

13           19-8 

257 

14-80 

3803 

France       .          . 

2-6 

7-2 

12-8        16-9 

265 

13-03 

3445 

Belgium 

1-92 

6-7 

10-5        15-1 

281 

14-37 

4032 

Austria-Hungary         . 

3-45 

8-15 

8-3        11-2 

249 

15-74 

3909 

Russia        .          .          .  ' 

2-7 

8-25 

6             9-1 

136 

16-37 

2230 

Spain         .          .         .-»••', 

0-77 

8-15 

.  4-5          5-4 

289 

11-88 

3439 

Portugal    . 

— 

— 

6             6-2 

— 

— 

— 

Greece        .          .         . 

2-4 

8-15 

3             3-8 

— 

— 

— 

Roumania  .          .          . 

— 

r- 

3-5          4-1 

165 

14-53 

2392 

Turkey      .          .          . 

5-47 

9-6 

3-5          5-7 

— 

— 

— 

Italy          .          .        ,.    - 

6-7 

14-4 

2-8          3-9 

299 

11-27 

3378 

Servia      f..         .         ...    . 

3-17 

7-7 

3             3-5 

— 

— 

— 

The  influence  of  the  price  of  sugar  on  the  consumption  is  shown  not  only  by  the  above 
Table  but  also  by  the  following  significant  facts  :  when  the  manufacturing  tax  was  reduced 
by  40  per  cent,  in  France  in  1903-1904,  the  consumption  increased  by  61  per  cent.  ;  in 
Germany  a  33  per  cent,  reduction  in  the  taxation  produced  an  increase  of  about  60  per 
cent,  in  the  consumption,  and  in  Belgium  55  per  cent,  more  sugar  was  consumed  as  a 
result  of  the  lowering  of  the  tax  by  29  per  cent. 

In  Italy  the  sugar  industry  has  developed  only  within  the  last  fifteen  years  (see  p.  477), 
as  is  shown  by  the  Table  on  p.  481  (in  1906  the  39,500  hectares  under  beet  gave  a  mean 
yield  of  270  quintals  of  beet  per  hectare,  the  limits  being  328  and  177). 

1  kilo  of  sugar ;  but  even  in  1870  1  kilo  of  sugar  could  be  obtained  from  11-9  kilos  of  beet,  and  in  1887  from 
8-1  kilos.  But  since  the  exports  increased  enormously  and  the  taxes  refunded  remained  the  same,  the  manu- 
facturers enjoyed  indirectly  a  considerable  export  bounty,  which  diminished  the  Exchequer  receipts  from  £3,000,000 
to  less  than  £760,000  (1888).  A  modification  was  hence  made  in  the  system  of  taxation,  sugar  produced  and 
consumed  at  home  paying  a  tax  of  £1  per  quintal,  while  that  exported  was  freed  from  tax  and  received  a  bounty 
of  2s.  Gd.  (raw)  or  3s.  6<2.  (refined)  per  100  kilos  (1896-1903).  Further,  the  import  duty  was  left  at  £2  per  quintal, 
so  that  German  producers  were  allowed  to  sell  their  sugar  at  high  prices  at  home  (even  during  the  abundance 
of  1900-1901)  and  to  employ  part  of  their  profits  to  lower  the  price  of  sugar  sold  abroad  in  competition  with  other 
countries.  After  the  Brussels  Convention,  however,  export  bounties  ceased  and  the  import  duty  was  reduced, 
to  5s.  +  16s.  (manufacturing  tax  in  Germany).  Under  these  new  conditions,  the  exports  diminished  somewhat, 
but  the  home  consumption  increased  owing  to  the  lowered  prices.  The  wholesale  price  in  1910  was  £2  per  quintal 
(that  of  sugar  for  export,  without  tax,  being  19s.) ;  the  retail  price  was  14d.  per  kilo  in  1875,  Id.  in  1902,  and  &d. 
in  1910.  The  German  Government  received  £5.750,000  in  sugar  taxes  in  1900-1901  and  almost  £8,000,000  in 
1909-1910. 


ESTIMATION    OF    SUGAR 


481 


Year 

Output 
of  raw 
sugar 

Imported 
raw 
sugar 

Total  consump- 
tion of 
refined  sugar 

Remarks 

Tons 

Tons 

Tons 

1887   .      '   . 

184 

140,000 

125,500 

100  tons  of  raw  sugar  taken  as 

1889   . 

632 

78,000 

71,000 

90  tons  of  refined 

1894  . 

2,090 

75,000 

70,000 

1897   . 

3,336 

75,500 

71,000 

1901    . 

73,800 

37,100 

99,880 

1902   . 

95,166 

20,000 

100,000 

1903   . 

128,000 

5,200 

120,000 

Overproduction  of  25,000  tons 

1904  .      '  , 

79,000 

2,100 

73,000 

1905  . 

112,000 

5,100 

112,000 

1906  . 

136,000 

1  5,000  (?) 

138,245 

Mean  yield  of  refined  sugar  from 

the   beets,    11-86   per   cent., 

the  mean  content  being  13-56 

per  cent.  ;    loss  in  working, 

1-70  per  cent. 

1906-1907   . 

106,400 

23,738  (?) 

— 

1907-1908   . 

136,000 

4,903 

145,000 

The  Italian  Government  received  £60,000  in  manufacturing  tax  and  £2,680,000  in 
import  duty  in  1897,  about  £2,560,000  in  tax  and  £320,000  in  Customs  duty  in  1903, 
£3,920,000  in  tax  and  £66,060  in  Customs  duty  in  1909-1910.  The  production  of  beets  in 
Italy  was  1,256,660  tons  in  1909  and  1,679,070  tons  in  1910,  the  output  of  sugar  being 
161,600  tons  in  1908-1909,  107,200  tons— from  9,670,700  quintals  of  beet— in  1909-1910, 
and  170,000  tons  in  1910-1911.  In  1910  Italy  imported  5800  tons  of  first-grade  and  655 
tons  of  second-grade  sugar. 

DETERMINATION  OF  SUGAR -CONTENT.  Sugar  is  estimated  in  various  ways. 
With  an  aqueous  sugar  solution,  the  content  of  saccharose  can  be  determined  by  means 
of  the  specific  gravity  at  17-5°,  compared  with  water  at  17-5°,  this  being  measured  by 
hydrometers,  pyknometers,  &c.  (see  vol.  i,  p.  72).  In  the  factory,  use  is  generally  made  of 
a  hydrometer  (saccharometer),  which,  at  17-5°,  gives  directly  the  percentage  of  saccharose 
present. 

These  saccharometers  were  first  proposed  by  Balling  and  were  subsequently  corrected 
by  Brix,  degrees  Brix  expressing  the  percentage  of  sugar.  In  France  and  Belgium,  and 
sometimes  also  in  Germany,  saccharometers  gauged  at  15°  and  referred  to  water  at  15° 
are  used,  and  the  Berlin  Royal  Commission  for  the  control  of  standards  prescribed  the 
use  of  saccharometers  giving  the  density  of  solutions  at  20°  referred  to  that  of  water  at  4°. 

The  following  Table  gives  the  densities  and  degrees  Brix  (grammes  of  sugar  per  100  grms. 
of  solution)  for  the  temperature  17-5°,  and  also,  for  each  10°,  the  values  from  the  other 
two  Tables,  so  that  the  intermediate  values  in  these  two  Tables  can  be  calculated  roughly. 
The  saccharometer  is  read  with  the  precautions  and  in  the  manner  indicated  on  p.  74 
of  vol.  i  and  on  p.  147  of  this  volume.  The  Table  gives  densities  above  66°  Brix,  which 
cannot  be  determined  by  hydrometers,  but  which  serve  to  calculate  the  degree  of  purity 
of  impure  saccharine  solutions  (molasses,  &c.  ;  see  later). 


It 


482 


MATEGCZEK  AND  SCHEIBLER'S  TABLE,  GIVING  THE  SPECIFIC  GRAVITIES  AND 
DEGREES  BRIX  OF  SACCHARINE  SOLUTIONS 


Sp.  gr. 
.  ]7-5° 
at17^ 

OJ  ±t 

"•c 

g?H 

n 

Sp.  gr. 
.  17-5° 
ati7-5°- 

i* 

Ml  ,v! 

P" 

Sp.  gr. 
,  17-5° 
at  lT.5° 

1  * 

11 

P 

Sp.  gr. 
.  17-5° 

^TTM 

l<-5 

1  * 

&s 

P 

Sp.  gr. 
17-5° 

*wv 

8  x 

Is 

1-00388 

i 

1-08778 

21 

1-18460 

41 

1-29531 

61 

1-42258 

81 

1-00779 

2 

1-09257 

22 

1-18981 

42 

1-30177 

62 

1-42934 

82 

1-01173 

3 

1-09686 

23 

1-19505 

43 

1-30777 

63 

1-43614 

83 

1-01570 

4 

1-10145 

24 

1-20033 

44 

1-31381 

64 

1-44298 

84 

1-01970 

5 

1-10607 

25 

1-20565 

45 

1-31989 

65 

1-44986 

85 

1-02373 

6 

1-11072 

26 

1-21100 

46 

1-32601 

66 

1-45678 

86 

1-02779 

7 

1-11541 

27 

1-21639 

47 

1-33217 

67 

1-46374 

87 

1-03187 

8 

1-12013 

28 

1-22182 

48 

1-33836 

68 

1-47074 

88 

1-03599 

9 

1-12488 

29 

1-22728 

49 

1-34460 

69 

1-47778 

89 

1-04014 

10 

1-12967 

30 

1-23278 

50 

1-35088 

70 

1-48406 

90 

1-04027  r^  1 
Llo  -I 

10 

1-12999  g] 

30 

rl5°n 
1-23330  —  -0 
L15  J 

50 

[15°T 
—  -s\ 
15  J 

70 

1-48716  rj£l 
Llo  1 

90 

[20°i 
—  J 

10 

r20°T 
1-126984[—  0-J 

30 

l-229567[^-J 

50 

1-347174[?J 

70 

l-479976f^-l 
L  4  J 

90 

1-04431 

11 

1-13449 

31 

1-23832 

51 

1-35720 

71 

1-49199 

91 

1-04852 

12 

1-13934 

32 

1-24390 

52 

1-36355 

72 

1-49915 

92 

1-05276 

13 

1-14423 

33 

1-24951 

53 

1-36995 

73 

1-50635 

93 

1-05703 

14 

1-14915 

34 

1-25517 

54 

1-37639 

74 

1-51359 

94 

1-06133 

15 

1-15411 

35 

1-26086 

55 

1-38287 

75 

1-52087 

95 

1-06566 

16 

1-15917 

36 

1-26658 

56 

1-38939 

76 

1-52810 

96 

1-07002 

17 

1-16413 

37 

1-27235 

57 

1-39595 

77 

1-53550 

97 

1-07441 

18 

1-16920 

38 

1-27816 

58 

1-40254 

78 

1-54290 

98 

1-07884 

19 

1-17430 

39 

1-28400 

59 

1-40918 

79 

1-55040 

99 

1-08329 

20 

1-17943 

40 

1-28989 

60 

1-41586 

80 

1-55785 

100 

1-08354  [g] 

20 

rl5°-i 
M7985  [^J 

40 

rl5°i 
1-29056  - 
Llo  J 

60 

rl5*i 
1-41628  [_] 

80 

1-56165  [If] 

100 

1-080959[  ---] 

20 

r20°n 
M76447[—  J 

40 

l-28S456r^-l 
L  4  - 

60 

r20*i 
1-411715[—  J 

80 

r20"~j 
1551800[—  J 

100 

If  the  degrees  Brix  are  read  with  solutions  at  temperatures  other  than  the  normal, 
corrections  must  be  made  by  means  of  the  following  Tables  : 


STAMMER'S  TABLE  FOR  REDUCING  TO  17-5°  DEGREES  BRIX  READ  AT  DIFFERENT 

TEMPERATURES 


DEGREES  BRIX  OF  THE  SOLUTIONS 

Temperature 

5 

10 

15 

20 

25 

30 

35 

40 

50 

60 

70 

75 

13=      } 

[These 

0-18 

0-19 

0-21 

0-22 

0-24 

0-26 

0-27 

0-28 

0-29 

0-33 

0-35 

0-39 

corrections 

15° 

to  be  subtracted  "I 

0-11 

0-12 

0-14 

0-14 

0-15 

0-16 

0-17 

0-17 

0-17 

0-19 

0-21 

0-25 

from  the  observed  1 

ir      J 

Brix  degrees      \ 

0-02 

0-03 

0-03 

0-03 

0-04 

0-04 

0-04 

0-04 

0-04 

0-05 

0-05 

0-06 

18"      \ 

0-03 

0-03 

0-03 

0-.03 

0-03 

0-03 

0-03 

0-03 

0-03 

0-03 

0-03 

0-02 

19° 

These 

0-08 

0-08 

0-09 

0-09 

0-10 

0-10 

0-10 

0-10 

0-10 

0-10 

0-08 

0-06 

corrections 

21° 

to  be  added      •> 

0-20 

0-22 

0-24 

0-24 

0-25 

0-25 

0-25 

0-26 

0-26 

0-25 

0-22 

0-18 

to  the  observed 

23° 

Brix  degrees 

0-32 

0-35 

0-37 

0-38 

0-39 

0-39 

sO-39 

0-40 

0-42 

0-39 

0-36 

0-33 

25* 

0-44 

0-47 

0-49 

0-51 

0-53 

0-54 

0-55 

0-55 

0-58 

0-54 

0-51 

0-48 

Example. — If  a  sugar  solution  shows  40°  Brix  (i.e.  40  per  cent,  of  sugar)  at  a  tempera- 
ture of  23°,  0-4  must  be  added  to  reduce  the  reading  to  the  true  Brix  degrees  at  17°  ;  so 
that  40  +  0-4  =  40-4  degrees  Brix  at  17°. 


POLARIMETERS 


483 


SCHEIBLER'S  TABLE  SHOWING  DEGREES  BRIX  AT  15°  AND  THE  CORRESPONDING 
DEGREES  AT  OTHER  TEMPERATURES  (FROM  10°  TO  25°) 


Teinperaturc 

DEGREES  BRIX  OR  PERCENTAGE  OF  SUGAR 

10° 

5-15 

10-19 

15-22 

20-24 

25-27 

30-29 

35-30 

40-31 

50-33 

60-35 

70-36 

75-36 

12°       . 

5-10 

10-12 

15-14 

20-15 

25-17 

30-18 

35-18 

40-19 

50-20 

60-21 

70-21 

75-21 

14° 

5-04 

10-04 

15-05 

20-05 

25-06 

30-06 

35-06 

40-07 

50-07 

60-07 

70-07 

75-07 

15° 

5-00 

10-00 

15-00 

20-00 

25-00 

30-00 

35-00 

40-00 

50-00 

60-00 

70-00 

75-00 

ir 

4-92 

9-91 

14-90 

l?-89 

24-88 

29-87 

34-37 

39-87 

49-86 

59-86 

69-86 

74-86 

19°       . 

4-83 

9-80 

14-78 

19-77 

24-75 

29-74 

34-73 

39-73 

49-72 

59-71 

69-71 

74-71 

21°       . 

4-72 

9-69 

14-66 

19-64 

24-62 

29-60 

34-59 

39-59 

49-57 

59-57 

69-57 

74-57 

23° 

4-61 

9-57 

14-53 

19-50 

24-48 

29-46 

34-45 

39-44 

49-42 

59-42 

69-42 

74-42 

25°       . 

4-49 

9-44 

14-40 

19-36 

24-34 

29-32 

34-30 

39-29 

49-27 

59-27 

69-27 

74-28 

Example. — If  a  solution  reads  19-36°  Brix  at  a  temperature  of  25°,  this  would  corre- 
spond with  20°  Brix  at  the  normal  temperature  of  15°.  For  intermediate  values,  either  of 
temperature  or  of  concentration,  the  corresponding  results  are  easily  obtained  by  inter- 
polation. Thus,  18°  Brix  at  temperature  15°  would  give,  at  other  temperatures,  values 
higher  than  those  corresponding  with  15°  Brix  by  three-fifths  of  the  difference  between 
the  values  in  the  15°  Brix  and  20°  Brix  columns.  So  that  a  solution  showing  18°  Brix  at 
the  temperature  15°  would  show,  at  the  temperature  17°,  14-90  +  §  (19-89  —  14-90)  = 
14-90  +  2-99  =  17-89°  Brix. 

In  the  quantitative  determination  of  sugar,  use  is  commonly  made  of  its  action  on 
polarised  light  (see  pp.  26  and  330),  this  being  measured  in  the  polarimeter.  The  rotatory 
power  of  a  sugar  solution  is  proportional  to  the  concentration  and  almost  independent  of 
the  temperature.  In  these  determinations  it  is  necessary  to  use  pure  sugar  solutions, 
decolorised  by  means  of  a  little  basic  lead  acetate,  which  precipitates  the  albuminoids, 
colouring-matters,  and  other  impurities  ;  the  filtered  solution  is  examined  in  the  polari- 
meter. If  the  saccharose  is  accompanied  by  another  optically  active  sugar — for  instance, 
glucose  (dextro-rotatory) — allowance  must  be  made  for  the  rotation  of  the  latter.  In  such 
a  case  the  diminution  in  rotation  produced  by  inversion  of  the  saccharose  with  dilute  acid 
would  give  the  amount  of  this  sugar. 

POLARIMETERS  AND  SACCHARIMETERS.1  One  of  the  best-known  polarimeters 
is  the  Laurent  shadow  instrument  (Fig.  351 ),  which  contains,  in  place  of  the  compensator 

1  It  has  been  mentioned  already  (see  p.  26)  that  crystals  of  Iceland  spar  and  quartz  have  the  property  of 
decomposing  a  ray  of  light  into  two  polarised  rays,  the  ordinary  and  the  extraordinary.  If  a  prism  of  Iceland 
spar  with  length  greater  than  the  breadth,  with  its  acute  angle 
of  68°,  is  cut  diagonally  and  lengthwise  so  as  to  divide  it  into 
two  rectangular  triangular  prisms  (Fig.  350),  and  these  be 
cemented  together  again  with  Canada  balsam,  the  result  is 
a  Nicol  prism.  When  a  ray  of  light,  Im,  enters  the  nicol,  of 
the  two  refracted  rays  (mo,  mp),  the  ordinary  one,  nw,  is 
totally  reflected  by  the  layer  of  Canada  balsam  and  is  thrown 
out  of  the  crystal  (or),  whilst  the  extraordinary  ray,  mp, 
passes  through  the  prism  (pqs)  and  emerges  polarised.  This 
ray  is  able  subsequently  to  traverse  a  second  nicol  only  when 
the  principal  section  of  this  analysing  nicol  is  parallel  to  that 
of  the  first  polarising  nicol.  If,  on  the  other  hand,  the  two 
principal  sections  are  perpendicular,  the  ray  undergoes  total 
reflection  and  will  not  pass  through  the  second  nicol ;  in 
intermediate  positions,  varying  quantities  of  light  are  allowed 
to  pass.  If  a  layer  of  water  is  placed  between  the  perpen- 
dicular nicols,  still  no  light  will  pass  through  the  analyser. 
But  if  a  sugar  solution  is  interposed,  the  light  passes  with  a 
greater  or  less  intensity  through  the  analyser,  which  must 

be  rotated  through  a  certain  angle  (proportional  to  the  quantity  of  sugar)  to  produce  total  disappearance 
of  the  light.  In  order  to  determine  exactly  when  the  luminous  ray  is  extinguished  (even  in  this  case 
a  kind  of  half-shadow  is  always  observed),  Solcil  attempted  to  divide  the  luminous  field  into  two  halves 
with  complementary  colours.  Indeed,  if  a  ray  of  polarised  light  is  passed  through  a  quarts  plate  placed 


FIG.  350. 


484 


ORGANIC    CHEMISTRY 


and  double -polarisation  quartz  plate,  a  special  semicircular  quartz  plate,  D,  half  a  wave- 
length in  thickness  and  occupying  one-half  of  the  field.  The  polariser,  B,  is  rotated  by 
means  of  the  rod,  X,  and  the  rotation  which  restores  the  two  halves  of  the  field  to  the 
same  luminosity  is  indicated  on  a  graduated  circle,  C,  provided  with  a  vernier,  read  by 
means  of  the  lens,  N,  and  illuminated  by  the  mirror,  M. 

The  source  of  monochromatic  light  is  a  double  Bunsen  flame  coloured  with  sodium 
chloride,  the  light  being  collected  by  the  lens,  B,  and  the  observation  made  through  the 
eye-piece,  0.  The  scale  of  the  apparatus  is  regulated  by  the  screw,  Z,  so  that  it  reads 
zero  when  the  two  halves  of  the 
field  are  equally  illuminated. 
If  a  tube  containing  a  liquid, 
interposed  between  the  two 
nicols,  causes  the  right-hand 
half  of  the  field  to  darken,  the 
liquid  is  dextro-rotatory,  while 
darkening  of  the  left-hand  half 
indicates  a  laevo -rotatory  com- 
pound. From  the  rotation  read 
on  the  scale,  the  specific  rota- 
tion can  be  calculated  by  the 
formulae  given  on  p.  27. 

The  practical    examination  FIG.  351. 

of  sugars  is  made  with  polari- 

meters  furnished  with  special  scales  and  known  as  saccharimeters;  the  Laurent  polari- 
meter  has  a  saccharimetric  graduation  as  well  as  that  showing  circular  degrees. 

In  the  French  saccharimeters  (Soleil  and  Laurent)  the  100  division  corresponds  with 
a  normal  aqueous  solution  of  pure  saccharose  (obtained  by  precipitation  of  a  very  concen- 
trated aqueous  solution  with  alcohol  and  drying  at  60°  to  70°)  containing  16-350  grms.  in 
100  c.c.  at  17-5°,  the  reading  being  made  in  a  tube  20  cm.  long  (the  same  reading  is  given 
by  a  quartz  plate  1  mm.  in  thickness).  In  the  German  instruments  (Ventzke-Scheibler, 
Schmidt  and  Haensch)  the  100  reading  is  obtained  with  a  length  of  20  cm.  of  a  saccharose 
solution  of  sp.  gr.  1-1,  which  contains  26-048  grms.  per  100  c.c.  at  a  temperature  of 

between  the  two  nicols,  one  half  of  this  plate  being  dextro-  and  the  other  Isevo-rotatory,  and  the  junction 
of  the  two  lying  exactly  on  the  axis  of  the  light,  the  two  halves  of  the  field  will  appear  illuminated  with  com- 
plementary colours.  If  the  plate  is  3-75  mm.  in  thickness  and  the  analyser  is  rotated  through  24-5°,  the  two 
halves  of  the  field  are  almost  completely  extinguished  and  assume  a  pale  red  coloration,  similar  in  the  two  halves. 
But  if  a  sugar  solution  is  interposed,  the  two  halves  assume  different  colours,  extinction  being  restored  by  rotation 
of  the  analysing  nicol.  Later  Soleil  suggested  compensating  the  rotation  of  the  sugar  solution  by  introducing, 


123 


FIG.  352. 

to  a  greater  or  less  extent,  between  the  nicols,  a  conical  quartz  plate  w  compensator,  moved  by  a  rack  indicating 
on  a  scale  the  thickness  of  the  plate  and  hence  the  equivalent  rotation.  The  more  modern  saccharimeters  of  the 
Soleil-Ventzke  type  have  two  compensators,  each  formed  of  two  quartz  wedges  (MN  and  HK,  Fig.  352)  of  opposite 
rotations,  and  are  fitted  also  with  the  Lippich  polariser  formed  of  three  nicols  (P),  which  give  a  field  divided  into 
three  zones ;  when  these  zones  are  not  equally  illuminated,  the  two  lateral  ones  show  a  colour  different  from 
that  of  the  middle  one.  The  analyser  is  enclosed  in  a  metal  box  to  protect  it  from  dust.  The  two  compensators 
with  their  scales  are  regulated  by  two  screws,  V  and  V.  When  the  two  scales  indicate  zero,  the  three  zones 
should  be  equally  illuminated. 


POLARIMETRY  485 

17-50.1     So  that  a  reading  of  one  division  corresponds  with.  0-26048  grm.  of  saccharose  per 
100  c.c.,  or  1  grm.  of  sugar  per  100  c.c.  gives  a  reading  of  3-839  divisions. 

The  source  of  light  for  modern  saccharimeters  is  an  incandescent  gas-burner  enclosed 
in  a  blackened  metal  chimney  fitted  with  a  ground-glass  window,  or  an  incandescent 
electric  lamp  of  at  least  32  candle-power  with  a  ground-glass  globe  and  also  enclosed  in  a 
black  case.  In  order  that  the  apparatus  may  not  become  heated,  the  lamp  should  be  placed 
at  a  distance  of  about  15  cm.,  and  to  render  the  luminous  fields  more  distinct  the  light  is 
passed  first  through  a  glass  cell  with  parallel  walls  filled  with  6  per  cent,  bichromate  solu- 
tion in  a  layer  15  mm.  thick  ;  in  this  way  the  more  refractive  rays  are  absorbed  and  a 
uniform  yellow  light  obtained.  The  normal  tube  of  the  saccharimeter  contains  a  layer  of 
liquid  exactly  20  cm.  long,  but  for  very  dilute  and  slightly  rotating  solutions  tubes  of  30, 40, 
and  50  cm.  are  used,  whilst  for  solutions  which  are  not  quite  colourless  tubes  of  10  or 
5  cm.  may  be  employed  ;  in  all  cases  the  readings  are  referred  to  the  normal  length  of 
20  cm.  Some  tubes  are  provided  with  an  aperture  for  the  introduction  of  a  thermometer, 
so  that  the  temperature  of  the  solution  may  be  read  in  the  instrument. 

The  saccharimeter  scale  extends  from  0  to  100  divisions  on  the  positive  side  and  to 
—  30  on  the  negative  side.  The  integral  divisions 
are  given  by  the  zero  of  the  vernier,  N  (Fig.  353),  and 
the  decimal  parts  by  that  division  of  the  vernier 
scale  which  coincides  exactly  with  a  division  on  the 
scale  ;  in  Fig.  353  the  reading  is  +  2-6  divisions.2 

The  specific  rotatory  power  of  saccharose 
varies  little  with  the  concentration  (up  to  30  per 
cent.)  and  with  the  temperature  (between  15° 
and  25°),  but  it  is  best  to  work  near  to  20°,  FIG.  353. 

when  [a]2D°  =  +  65-50.3 

1  That  is,  in  100  Mohr  c.c.,  1  Mohr  c.c.  being  the  volume  of  1  grm.  of  water  at  17-5°  weighed  in  air  with  brass 
weights.     The  true  c.c.  is  the  volume  of  1  grm.  of  water  at  4°  weighed  in  vacua  ;   calculation  on  the  basis  of  the 
coefficient  of  expansion  of  water  shows  that  100  Mohr  c.c.  are  equal  to  100-234  true  c.c.,  so  that  100  true  c.c.  of 
the  normal  saccharose  solution  at  17-5°  would  cojtain  25-987  grms.  of  saccharose.     The  International  Commission 
for  uniform  methods  of  sugar  analysis  proposed  in  1900  the  fixing  of  the  100  point  of  the  saccharimeter  by  a 
length  of  20  cm.  of  a  solution  obtained  by  dissolving  26  grms.  of  pure  saccharose  in  water  to  a  volume  of  100 
true  c.c.  at  20°  and  polarising  at  20°  (100  true  c.c.  of  water  at  20°  weigh  99-7174  grms.  in  air  and  99-8294  grms. 
in  vacua). 

2  With  double  compensation  saccharimeters  (furnished  with  two  scales,  a  working  scale  and  a  control,  V  and 
V,  Fig.  352)  the  procedure  is  as  follows  :  When  the  tube  with  the  sugar  solution  is  introduced  between  the  nicols 
the  control  scale  is  placed  at  zero,  the  working  scale  being  then  moved  by  the  screw  until  the  field  is  uniformly 
illuminated  and  its  position  read.     The  sugar  solution  is  next  removed  and  the  control  scale  moved  until  the 
field  is  again  uniform,  the  reading  of  this  scale  being  nearly  equal  to  the  first  reading  of  the  working  scale.     The 
tube  of  solution  is  now  again  introduced  and  the  position  of  the  working  scale,  near  to  the  zero-point,  read  after 
its  adjustment  to  give  uniform  luminosity.    Finally  the  tube  is  again  removed  and  the  control  scale  moved 
until  the  field  is  uniform  and  its  position  read.     The   final  result  is  obtained  by  subtracting  the  mean  of  the 
second  pair  of  readings  from  the  mean   of  the   first  pair.     Thus,  if  the  readings  were  +  78-6,  +  78-4,  +  0-2, 
and  -  0-3,  the  result  would  be  78-5  —  0-05  =  +  78-45. 

3  Invert  sugar,  on  the  contrary,  has  a  rotatory  power  varying  markedly  with  the  concentration  and  tempera- 
ture.   A  solution  of  saccharose  containing  the  normal  weight  (26-048  grms.)  contains,  after  inversion,  27-419 
grms.  of  invert  sugar,  and  if  this  is  contained  in  100  c.c.  it  gives  a  deviation  of  —  32-66  in  a  20  cm.  tube  at  20°. 
The  variation  per  degree  of  temperature  is  0-5,  so  that  at  0°  this  reading  would  be  —  42-66  and,  in  general,  at 
any  temperature,  t,  it  would  be  —  42-66  +  0-5  t.     If  no  account  is  taken  of  variations  due  to  the  concentration, 
1  division  Ventzke  corresponds  with  0-8395  grm.  of  invert  sugar  in  100  c.c.  (Mohr),  the  solution  being  read  in  a 
20  cm.  tube  at  20"  ;   or  1  grm.  of  invert  sugar  dissolved  in  100  Mohr  c.c.  gives  a  reading  of  —  1-191  division. 
The  specific  rotatory  power  of  invert  sugar  for  different  concentrations  (from  1  to  35  per  cent.)  is  given  by  the 
formula  :    [a] 20  =  _  19-657  —  0-03611c,  c  indicating  the  weight  of  invert  sugar  in  100  c.c.      For  concentrations 
near  15  per  cent,  the  value  —  20-2  may  be  taken  for  the  specific  rotation  of  invert  sugar,  1  circular  degree  then 
corresponding  with  2-475  grm.  of  invert  sugar  in  100  true  c.c.  and  1  grm.  of  invert  sugar  in  100  true  c.c.  giving 
a  rotation  in  circular  degrees  of  —  0-404. 

Glucose  has  a  specific  rotation,  [a]2D°  —  +  52-8",  which  is  constant  after  muta-rotation  has  ceased  (see  p.  27), 
i.e.  if  the  observation  is  made  after  the  solution  has  been  either  left  for  24  hours  or  boiled  for  15  minutes.  The 
concentration  and  the  temperature  have  virtually  no  influence  on  the  rotatory  power  and,  with  a  20  cm.  tube, 
1"  corresponds  with  0-947  grm.  in  100  true  c.c.  and  hence  1  grm.  of  glucose  in  100  true  c.c.  will  give  a  rotation 
of  1-056°.  One  division  on  the  Ventzke  saccharimeter  corresponds  with  0-3448°  (corrected  for  the  dispersion), 
and  the  normal  weight  is  32-71  grms.  of  glucose  in  100  Mohr  c.c. ;  thus  1  Ventzke  division,  with  a  20  cm.  tube 
and  a  temperature  of  20°  corresponds  with  0-3271  grm.  of  glucose  per  100  Mohr  c.c.,  or  1  grm.  of  glucose  per 
100  Mohr  c.c.  gives  a  rotation  of  3-057  Ventzke  divisions. 

For  fructose  (levulose)  the  data  are  uncertain  owing  to  the  difficulty  of  obtaining  pure  crystals,  and  the  rotatory 
power  varies  with  the  concentration  (for  solutions  of  about  10  per  cent,  strength,  [a]2^  =  —  93°)  and  with  the 
temperature  (an  increase  of  1°  of  temperature  diminishes  the  specific  rotatory  power  by  0-67°).  One  division 
on  the  Ventzke  saccharimeter  corresponds  with  0-1838  grm.  of  levulose  in  100  Mohr  c.c.,  or  1  grm.  of  levulose 
gives  a  rotation  of  —  5-439  Ventzke  divisions  in  a  20  cm.  tube  at  the  temperature  20°. 

For  C,?H8?OU  +  H,O,  after  the  disappearance  of  the  muta-rotation,  the  specific  rotation,  which  is 


486  ORGANIC    CHEMISTRY 

CHEMICAL  DETERMINATION  OF  SUGARS.  With  the  exception  of  saccharose 
and  raffinose,  the  sugars  (glucose,  levulose,  &c.)  reduce  Fehling's  solution  (an  alkaline 
solution  of  copper  sulphate  containing  salts  of  organic  hydroxy-acids  ;  see  pp.  212  and 
335)  in  the  hot,  with  separation  of  a  corresponding  amount  of  cuprous  oxide.  Fehling's 
solution  is  obtained  by  mixing,  just  before  using,  equal  volumes  of  the  two  following 
solutions  :  (a)  69-278  grms.  of  pure  crystallised  copper  sulphate  (CuS04  +  5H£O),  air- 
dried  until  constant  in  weight,  dissolved  in  water  to  1  litre  ;  (b)  346  gims.  of  Rcchelle  tali 
(sodium  potassium  tartrate)  and  100  grms.  of  pure  solid  sodium  hydroxide  dissolved  in 
water  to  1  litre.  Since  saccharose  does  not  reduce  Fehling's  solution,  it  must  be  first 
inverted.  For  this  purpose,  9-5  grms.  of  the  sugar  are  dissolved  in  700  c.c.  of  N/5-hydro- 
chloric  acid  and  the  solution  heated  for  30  minutes  in  a  water-bath  at  75°,  neutralised  with 
caustic  soda,  and  made  up  to  1  litre.  This  solution,  which  contains  10  grms.  of  invert 
sugar,  is  then  ready  for  testing. 

The  Fehling  test  may  be  either  volumetric  or  gravimetric,  the  concentration  of  the 
sugar  being  reduced  to  about  1  per  cent,  (by  a  preliminary  trial)  and  the  details  of  the 
procedure  being  followed  exactly.  Volumetric  method :  40  c.c.  of  water  and  10  c.c.  of 
Fehling's  solution  (5  c.c.  of  each  of  the  component  solutions)  are  brought  to  boiling  in  an 
Erlenmeyer  flask,  a  measured  quantity  (4  to  5  c.c.)  of  the  sugar  solution  run  in  from  a 
burette,  and  the  liquid  again  heated  and  kept  boiling  for  a  definite  time  (2  minutes  for 
glucose  or  invert  sugar,  4  minutes  for  maltose,  and  6  for  lactose) ;  the  flame  is  then  removed, 
a  few  drops  of  the  liquid  filtered,  and  the  filtrate  acidified  with  a  little  acetic  acid  and 
tested  with  a  drop  of  potassium  ferrocyanide  solution.  If  a  red  coloration  is  produced, 
the  test  is  repeated  with  a  larger  quantity  of  sugar  solution,  whilst  if  no  red  coloration 
appears,  a  less  quantity  of  the  sugar  is  tried.  This  procedure  is  continued  until  in  the 
last  two  tests,  representing  excess  and  deficiency  of  the  sugar  solution,  the  difference 
between  the  two  volumes  is  not  more  than  0-1  c.c.  ;  the  mean  of  these  two  volumes 
is  employed  in  calculating  the  sugar-content  of  the  solution.  100  c.c.  of  undiluted 
Fehling's  solution,  under  the  above  conditions,  correspond  with  0-4945  grm.  of 
glucose,  0-533  of  levulose,  0-515  of  invert  sugar,  0-740  of  maltose,  and  0-676  of  lactose 
(hydrated). 

The  gravimetric  estimation  is  carried  out  as  follows  (Allihn's  method) :  To  60  c.c.  of 
Fehling's  solution,  diluted  with  60  c.c.  of  boiled  distilled  water  and  heated  to  boiling,  are 
added  25  c.c.  of  the  sugar  solution  of  about  1  per  cent,  concentration,  the  liquid  being 
thsn  again  heated  and  kept  boiling  for  a  definite  time  (2  minutes  for  glucose,  levulose,  and 
invert  sugar,  4  for  maltose,  and  6  for  lactose).  The  solution  is  then  filtered  at  once,  with 
the  aid  of  a  filter-pump,  through  a  dried  and  weighed  Soxhlet  tube  containing  a  layer  of 
asbestos,  the  cuprous  oxide  being  repeatedly  washed  with  a  total  quantity  of  300  to  400  c.c. 
of  boiling  water,  then  with  two  or  three  portions  of  alcohol,  and  finally  with  ether. 
The  tube  is  then  dried  in  an  oven,  and  the  cuprous  oxide  subsequently  reduced  to 
metallic  copper  by  passing  a  current  of  dry  hydrogen  through  the  tube  and  gently 
heating  the  oxide  with  a  small  flame  ;  the  hydrogen  is  kept  passing  until  the  tube  is 
quite  cold,  when  the  weight  is  taken.  From  the  weight  of  copper  thus  obtained,  the 

but  slightly  influenced  by  the  concentration,  is  [a]2D°=  +  52-53°;  this  diminishes  by  0-075°  for  every  degree 
rise  in  temperature.  One  degree  of  rotation  corresponds  with  0-9519  grm.  of  lactose  in  100  true  c.c.,  so  that 
1  grm.  of  lactose  gives  a  rotation  of  1-051°.  For  the  Ventzke  saccharimeter,  the  normal  weight  is  32-95  grms. 
per  100  Mohr  c.c.  (32-83  grms.  in  100  true  c.c.),  so  that  1  Ventzke  division  in  a  20  cm.  tube  corresponds  with 
0-3295  grm.  of  lactose  in  100  Mohr  c.c.  and  1  grm.  of  lactose  in  100  Mohr  c.c.  gives  a  rotation  of  3-035  Ventzke 
divisions. 

Maltose  has  a  specific  rotation  (after  muta-rotation  has  been  destroyed  ;  see  Glucose)  varying  with  the  tem- 
perature and  concentration  according  to  the  equation  :  [a]'  =  140-375  —  0-01837  c  —  0-095  t,  where  t  indicates 
the  temperature  and  c  the  percentage  by  weight  of  anhydrous  maltose.  For  medium  concentrations,  W^0  = 
+  138-2°  and  1°  corresponds  with  0-3618  grm.  of  maltose  per  100  true  c.c.  with  a  20  cm.  tube  and  1  grm.  of  maltose 
in  100  c.c.  gives  a  rotation  of  2-764°.  For  the  Ventzke  saccharimeter,  the  normal  weight  is  12-55  grms.  of  maltose 
in  100  true  c.c.  or  12-58  grms.  in  100  Mohr  c.c.,  and  for  a  20  cm.  tube  at  the  temperature  20°,  1  Ventzke  division 
corresponds  with  0-1255  grm.  of  maltose  in  100  true  c.c.,  while  1  grm.  of  maltose  in  100  true  (Mohr)  c.c.  gives 
a  rotation  of  7-968  (7-949)  Ventzke  divisions.  N 

Raffinose,  C^HajO,,  +  5H2O,  has  the  specific  rotation,  [a]2^  =  +  104-5°,  which  is  almost  independent  of 
the  temperature  and  concentration  ;  for  anhydrous  raffinose  the  value  is  +  123-15°.  One  degree  of  rotation 
corresponds  with  0-4785  grm.  of  hydrated  raffinose  in  100  true  c.c.  with  a  20  cm.  tube  and  1  grm.  of  raffinose 
in  100  true  c.c.  gives  a  rotation  of  2-09°.  For  the  Ventzke  saccharimeter  the  normal  weight  is  16-576  grms.  per 
100  Mohr  c.c.  or  16-537  grm.  per  100  true  c.c.,  so  that  1  Ventzke  division  corresponds  with  0-16576  grm.  of  raffinose 
in  100  Mohr  c.c.  and  1  grm.  of  raffinose  in  100  Mobr  c.c.  gives  a  rotation  of  6-033  Ventzke  divisions  in  a  20  cm. 
tube, 


QUOTIENT    OF    PURITY,    ETC. 


487 


corresponding  weight  of  sugar  is  read  off  from  the  following  Table,  all  the  numbers 
representing  milligrams : 


hi 

ft 
ft 

8 

Glucose 

fa 

>•  CUD 

H"  I     tf> 

Maltose 

Lactose 

n 

1 
s 

Glucose 

Oi     OJ 

|| 

Maltose 

Lactose 

S 
Pi 

ft 

6 

Glucose 

la 

£  a 

Maltose 

Lactose 

30 

16 

_ 

25-3 



155 

79-1 

81-6 

135-9 

112-6 

280 

145-5 

151-9 

247-8 

208-3 

35 

18-5 

— 

29-6 

— 

160 

81-7 

84-3 

140-4 

116-4 

285 

148-3 

154-9 

252-2 

212-3 

40 

20-9 

— 

33-9 

— 

165 

84-3 

87-0 

144-9 

120-2 

290 

151-0 

157-8 

256-5 

216-3 

45 

23-4 

— 

33-3 

— 

170 

86-9 

89-7 

149-4 

123-9 

295 

153-8 

160-8 

261-1 

220-3 

50 

25-9 

— 

42-6 

•  — 

175 

89-5 

92-4 

153-8 

127-8 

300 

156-5 

163-8 

265-5 

224-4 

55 

28-4 

— 

47-0 

— 

180 

92-1 

95-2 

153-3 

131-6 

305 

159-3 

166-8 

269-9 

228-3 

60 

30-8 

— 

51-3 

— 

185 

94-7 

97-8 

162-7 

135-4 

310 

162-0 

169-7 

— 

232-2 

65 

33-3 

— 

55-7 

— 

190 

97-3 

100-6 

167-2 

139-3 

315 

164-3 

172-7 

— 

236-1 

70 

35-3 

— 

60-1 

— 

195 

100-0 

103-4 

171-6 

143-1 

320 

167-5 

175-6 

— 

240-0 

75 

38-3 

— 

64-5 

— 

200 

102-6 

106-3 

176-1 

146-9 

325 

170-3 

178-6 

— 

243-9 

80 

40-8 

— 

68-9 

— 

205 

105-3 

109-1 

180-5 

150-7 

330 

173-1 

181-6 

— 

247-7 

85 

43-4 

— 

73-2 

— 

210 

107-9 

111-9 

185-0 

154-5 

335 

175-9 

184-7 

— 

251-6 

90 

45-9 

46-9 

77-7 

— 

215 

110-6 

114-7 

189-5 

158-2  ; 

340 

178-7 

187-8 

— 

255-7 

95 

48-4 

49-5 

82-1 

— 

220 

113-2 

117-5 

193-9 

161-9 

345 

181-5 

190-8 

— 

259-8 

100 

50-9 

52-1 

86-6 

71-6 

225 

115-9 

120-4 

198-4 

165-7 

350 

184-3 

193-8 

— 

263-9 

105 

53-5 

54-8 

91-0 

75-3 

230 

118-5 

123-2 

202-9 

169-4 

355 

187-2 

196-8 

— 

268-0 

110 

56-0 

57-5 

95-5 

79-0 

235 

121-2 

126-0 

207-4 

173-1 

360 

190-0 

199-8 

— 

272-1 

115 

58-6 

60-1 

99-9 

82-7 

240 

123-9 

128-9 

211-8 

176-9 

365 

192-9 

203-0 

— 

276-2 

120 

61-1 

62-8 

104-4 

86-4 

245 

126-6 

131-8 

216-3 

180-8 

370 

195-7 

206-1 

— 

280-5 

125 

63-7 

65-5 

108-9 

90-1 

250 

129-2 

134-6 

220-8 

184-8  ; 

375 

198-6 

209-2 

— 

284-8 

130 

66-2 

68-1 

113-4 

93-8 

255 

131-9 

137-5 

225-3 

188-7 

380 

201-4 

212-4 

— 

289-1 

135 

63-8 

70-8 

17-9 

96-6 

260 

134-6 

140-4 

229-8 

192-5 

385 

204-3 

215-5 

— 

293-4 

140 

71-3 

73-5 

22-4 

101-3 

265 

137-3 

143-2 

234-3 

196-4 

390 

207-1 

218-7 

— 

297-7 

145 

73-9 

76-1 

26-9 

105-1 

270 

140-0 

146-1 

238-8 

200-3 

395 

210-0 

221-8 

— 

302-0 

150 

76-5 

73-9 

31-4 

108-8 

275 

142-8 

149-0 

243-3 

204-3 

400 

212-9 

224-9 

— 

306-3 

NON-SUGAR,  APPARENT  DENSITY,  TRUE  DENSITY,  AND  QUOTIENT  OF 
PURITY.  Sugars  and  their  solutions  are  distinguished,  commercially  and  industrially, 
by  their  content  of  saccharose,  water,  and  solids  not  sugar  (e.g.  salts  and  various  organic 
substances). 

The  Brix  saccharometer  is  graduated  with  pure  sugar  solutions,  and  hence  gives  results 
which  are  increasingly  inaccurate  as  the  degree  of  impurity  of  the  sugar  solutions  increases. 
Apparent  density  is  that  shown  by  the  Brix  hydrometer,  while  the  real  density  corresponds 
with  the  true  content  of  sugar  determined  by  direct  analysis  (by  the  polarimeter  or,  after 
inversion,  by  Fehling's  solution).  The  difference  between  the  real  and  apparent  densities, 
expressed  in  degrees  Brix,  indicates  the  non-sugar  in  Brix  degrees,  while  the  ratio  between 
the  real  and  apparent  densities,  in  degrees  Brix,  is  termed  the  quotient  of  purity  and, 
when  multiplied  by  100,  shows  the  percentage  of  sugar  present  independently  of  the 
water. 

In  the  analysis  of  a  mixture  of  various  sugars  a  number  of  optical  and  chemical  tests 
must  be  made  in  order  to  deduce,  directly  or  indirectly,  the  quantities  of  the  separate 
components  (see  Villa  vecchia,  Chim.  Anal.  Tecnol.,  vol.  ii,  pp.  223  et  seq.).1 

1  If  only  saccharose  and  another  sugar  are  present,  p  grms.  of  the  mixture  are  dissolved  in  water  to  100  c.c. 
and  the  polarisation,  P,  read  ;  if  at  is  the  rotation  of  1  grm.  of  saccharose  per  100  c.c.  and  a2  that  of  1  grm.  of 
the  other  sugar,  the  quantities  x  and  y  of  saccharose  and  the  other  sugar  respectively  are  given  by  the  formulae 


(I)  x  = 


~  atP 


(II)     y  =  °'P~     »  since  x  +  y  =  p  (III)  and  ap  +  a^y  =  P  (IV).     The  values  of  alt  a2,  and 
— 


P  must  be  given  their  proper  algebraic  signs  (+  or  —  ). 

A.  In  the  special  case  of  a  mixture  of  saccharose  and  glucose,  the  components  x  and  y  may  be  determined  in 
various  ways  : 

(1)  The  glucose  (y)  may  be  estimated  by  means  of  Fehling's  solution  ;   formula  IV  then  gives  x  =  —    —  (V). 

»  ai 

Since  saccharose  reduces  Fehling's  solution  to  a  very  slight  extent,  small  proportions  of  glucose  are  best  deter- 

mined by  means  of  Soldaini's  reagent,  which  consists  of  150  grms.  of  potassium  bicarbonate,  104-4  grms.  of  normal 
potassium  carbonate,  and  100  c.c.  of  tho  copper  sulphate  solution  used  for  Fehling's  solution,  made  up  to  a  litre 
with  water. 

(2)  The  solution  of  the  mixture  is  polarised  (P),  the  saccharose  being  inverted  and  the  polarisation  again 
read  (P,).     If  a3  is  the  ro  tation  of  1  grm.  of  invert  sugar  (=  —  1-191),  then,  since  1  grm.  of  saccharose  gives 

P  —  P, 
1-053   grm.   of  invert  sugar,   we  have  1-053   a,x  +  a$  —  PI   (VI)  and  hence  x  =  -  (VII)  and 


g.P.  -  1-053«3P 


a2(a!  —  l-053a3) 

3-839P,  +  1-254P 

5-093  X  3-057 


—  (VIII)      at  having  the  value  3-839  and  o»,  3-057,  it  follows  that  x  = 


al  —  l-053a3 
P  _  p 


'  (IX)  and 


(X),   which  are  the  quantities  of  the  two  sugars  in   p   grms.   of   the   mixture.     The 


488  ORGANICCHEMISTRY 

The  total  ash  of  a  sugar  is  determined  by  weighing  3  grms.  into  a  tared  platinum  dish, 
moistening  it  with  a  few  drops  of  concentrated  sulphuric  acid,  carbonising  over  a  Bunsen 
flame  and  incinerating  in  a  muffle  at  a  low  red  heat  (about  700°)  so  that  the  ash  does  not 
fuse.  From  the  sulphated  ash,  one-tenth  of  its  weight  is  deducted  in  order  to  correct  for 
the  increase  due  to  the  formation  of  sulphates.  By  means  of  tables  the  quantity  of  soluble 
ash  can  also  be  deduced. 

The  water  is  determined  by  heating  5  to  10  grms.  of  the  sugar  in  a  flat  glass  dish  covered 
with  a  clock-glass  at  105°  to  110°  first  for  2  hours  and  subsequently  to  constant  weight. 
Subtraction  from  100  of  the  water  and  the  sugar  gives  the  percentage  of  total  non-sugar, 
while  further  subtraction  of  the  ash  gives  the  organic  non-sugar.  The  alkalinity  of  the 
sugar  is  determined  by  titrating  an  aqueous  solution  of  20  grms.  of  the  product  with 
decinormal  sulphuric  acid  in  presence  of  phenolphthalein  ;  the  result  is  calculated  as 
grammes  of  CaO  per  100  grms.  of  sugar. 

lOOz          WOy 
Percentages  will  therefore  be  -  and  -  respectively.    For  a  mixture  of  saccharose  and  levulose,  a2  =  —  5-439, 

—  3-839P,  —  1-254P 

so  that  y  =  -  JvT^TTi  -  >    f°r  saccharose  and  invert  sugar,  «2  =  —  1-191  and  the  denominator  becomes 
* 


3-839P,  -f  1-254P 
6-066  instead  of  27-701  ;    for  mixtures  of  saccharose  and  maltose,  a,  =  7-949  and  y  =  -  7~alq  —  >    for 

saccharose  and  lactose  hydrate,  a2  =  3-035. 

(3)  The  glucose  is  first  determined  by  means  of  Fehling's  solution  ;  in  another  portion  of  the  solution  the 
.saccharose  is  inverted  and  the  reducing  sugars  again  estimated  with  Fehling's  solution  ;  the  difference  between 
these  two  estimations  gives  the  invert  sugar  and  this,  multiplied  by  0-95,  the  saccharose. 

B.  With  a  mixture  of  saccharose  and  rafflnose,  the  polarisation  is  determined  before  (P)  and  after  (PJ  inversion  ; 

«!  and  a2  being  the  known  rotations  of  1  grm.  of  each  of  the  two  sugars  and  a3  and  a4  those  of  1  grm.  of  the 

respective  inverted  products,  it  follows  that  :    a&  +  a^j  =  Pt  (XIII)  and  1-053  aax  +  1-036  a^y  =  P!  (XIV)  ; 

substitution  in  these  of  the  values  c^  =  3-839,  at  =  7-11,   1-053  at  =  --  1-254  and  1-036  a4  =  3-643    gives 

0-5124P  —  P,  1-254P  +  3-839Pt 

and  y  —  -  ^—:  -  .    For  the  determination  of  the  rafflnose  by  means  of  methyl- 

"' 


phenylhydrazine,  in  presence  of  saccharose  and  invert  sugar,  see  Rafflnose,  p.  442. 

C.  When  two  reducing  sugars,  but  neither  saccharose  nor  rafflnose  is  present,  it  is  sufficient  to  measure  the 
polarisation  and  apply  formulae  I  to  IV.  But  if  a  non-saccharine  substance  is  also  present,  it  is  necessary  to 
determine  also  the  number  (F)  of  c.c.  of  Fehling's  solution  reduced  by  a  weight,  p,  of  the  substance  ;  if  6j  and 
6a  are  the  volumes  (c.c.)  of  Fehling's  solution  reduced  by  1  grm.  of  each  of  the  two  sugars  dissolved  in  100  c.c., 

then  :   atx  +  a&  =  P  (XV)  and  bjX  +  b2y  =  F  (XVI)  and  hence  x  =    '     ~  "l    and  y  =  a'  '  ~    ',  .     With  a 

— 


mixture  of  glucose  and  levulose,  «j  =  3-057,  a.,  =  —  5-439,  6j  ••=  202-4,  and  6,  =  186,  so  that  x  —  -  -  —  - 

1669 

3-057.F  -  202-4P 
and  y  =  -  i-^r  -  .     For  mixtures  of  glucose  and  maltose,  a2  has  the  value  7-940  and  62  135  ;   these  last 

lOO9 

two  numbers  hold  also  for  mixtures  of  invert  sugar  and  maltose,  but  then  at  —  —  1-191  and  6t  =  194  ;  for  mixtures 
of  glucose  and  lactose,  a^  —  3-057,  a2  =  3-035,  b^  =  202-4,  and  62  =  148,  while  for  invert  sugar  and  lactose,  a.2  and 
&2  have  the  values  just  given,  but  at  =  —  1-191  and  bi  =  194. 

D.  With  a  mixture  of  saccharose  (x),  glucose  (y),  and  levulose  (z),  if  a  weight,  p,  is  dissolved  to  100  c.c.,  and 
«!,  a2,  a3,  at  represent  the  respective  rotations  of  1  grm.  of  each  of  these  sugars  and  of  invert  sugar  in  100  c.c., 
62  and  63  the  number  of  c.c.  of  Fehling's  solution  reduced  by  1  grm.  of  each  of  the  reducing  sugars,  P  and  P,, 
the  polarisations  before  and  after  inversion,  and  F  the  number  of  c.c.  of  Fehling's  solution  reduced  by  weight 
p  of  the  substance,  then  (XVII)  P  =  OjX  +  asy  +  a3z  ;  Pt  =  1-053  atx  +  <z2.y  +  a3z  ;  F  =  b2y  +  63z.  The 

p  _  p 
first  two  of  these  give  x  =  -  rrr^  —  .  which  corresponds  with  formula  VII.    Then  (XVIII)  a2y  +  a,z  =  P—  a^x 

Cti  —   .I*v0tm4 

and  622/  +  b3z  =  F,  which  are  analogous  to  formula  XV,  allow  of  the  determination  of  the  values  of  y  and  z. 

p  _  p 
Thus  x  =  1  and  for  y  and  z  we  have,  in  analogy  to  formula  XVI  (diminishing  the  polarisation,  P,  by  the 

' 


233P  +  714P,  +  27-7F  15-57F  -  254P  -  777P, 

rotation  of  the  saccharose,  3-839z),  y  =  -  r^r  -   and  z  =  -  —  —  -  •.      With  a 

8500  8500 

mixture  of  saccharose  (x),  invert  sugar  (y)  unri  lactose  (z),  the  saccharose  is  arrived  at  as  above,  and  then  : 

15-46P  -  185-6P  —  568Pi  6-066.F  +  243P  +  745P, 

*=  3896  and      Z=  3896  ~  ' 

Practical  Examples.  26-048  grms.  of  the  sugar  or  mixed  sugars  are  dissolved  in  a  100  c.e.  flask  and,  if  the  solu- 
tion is  coloured,  basic  lead  acetate  solution  (10  to  30  drops)  is  added  drop  by  drop  until  it  forms  no  further  tur- 
bidity ;  the  solution  is  made  up  to  100  c.c.  with  water,  filtered  through  a  dry  filter  and  polarised  in  a  20  cm.  tube. 
a  drop  of  acetic  acid  being  previously  added,  if  necessary,  to  make  the  liquid  clearer. 

If  it  is  thought  desirable  to  eliminate  the  excess  of  lead  acetate,  the  liquid  is  made  up  to  volume  with  saturated 
sodium  sulphate  solution  instead  of  with  water. 

In  the  case  of  a  mixture  of  invert  sugar  and  saccharose,  if  the  normal  weight  solution  gives  a  rotation  of 
+  24-0  before  and  —  27-0  after  inversion,  the  quantity  of  saccharose  in  100  c.c.  of  the  solution  will  be 
24  +  27  3-839  X  27  -  1-254  X  24 

10-01,  and  that  of  invert  sugar  -  r^r^s  -  =  12-12  grms. 

' 


D'0o6 

If  other  sugars  are  also  present,  the  invert  sugar  is  first  determined  with  Fehling's  solution,  such  quantity  of 
the  sugar  solution  being  taken  (after  a  preliminary  trial)  as  contains  about  0-2  grm.  of  invert  sugar  and  the  deter- 
mination being  made  with  50  c  c.  of  Fehling's  solution  by  the  gravimetric  method.  The  result  is  subject  to  a 
slight  correction,  according  to  a  Table  by  Meissl  and  Hiller,  for  the  influence  of  the  saccharose  on  the  Fehling's 
solution  ;  but  this  only  in  cases  where  the  invert  sugar  is  present  in  relatively  small  proportion  compared  witji 
the  saccharose,  as,  for  instance,  when  samples  of  saccharose  are  being  analysed. 


STARCH  489 

PURIFICATION  OF  WASTE -WATERS  FROM  SUGAR- WORKS.  The  waters 
requiring  purification,  since  they  are  highly  contaminated  and  readily  ferment,  are  those 
used  in  emptying  and  washing  the  diffusors,  those  from  the  pulp-presses  and,  partly,  those 
in  which  the  beets  have  been  washed.  The  first  contain  up  to  0-5  per  cent,  of  suspended 
matter  and  0-6  to  0-8  per  cent,  of  dissolved  organic  matter,  with  about  0-3  per  cent,  of 
sugar  ;  they  have  a  bad  smell,  and  it  is  usually  prohibited  to  introduce  them  as  they  stand 
into  streams. 

Chemical  purification  (with  lime  or  iron  oxide  or  sulphate)  is  costly  and  insufficient, 
while  the  mechanical  method  of  filtration  to  remove  the  suspended  matter  does  something 
but  only  partially  solves  the  problem.  Biological  purification  (see  vol.  i,  p.  223),  preceded 
by  filtration  or  by  aeration  (omitting  the  septic  tank)  gives  better  results  than  the  older 
processes,  but  is  not  entirely  satisfactory  (it  eliminates  40  to  70  per  cent,  of  the  organic 
matter).  The  principal  bacteria  which  destroy  saccharose  are  Leuconostoc  and  Clostridium. 
The  problem  of  the  complete  purification  of  these  waste-waters  still  remains  unsolved. 

D.  TETROSES 

MANNOTETROSE,  C24H42021,  is  found  in  manna,  and  yields  2  mols. 
galactose,  1  of  fructose,  and  1  of  glucose  on  hydrolysis. 

E.  HIGHER  POLYOSES 

These  are  not,  or  but  slightly,  sweet,  and  are  amorphous  and,  in  some 
cases,  insoluble  in  water.  On  hydrolysis  they  usually  give  either  pentoses  alone 
or  hexoses  alone,  pentoses  and  hexoses  being  formed  together  only  in  rare 
instances.  Their  molecular  weights  are  unknown,  but  their  molecules  are  very 
large  and  are  represented  by  the  general  formula,  n  (C6H1206)  —  (n  —  1)  H20  ; 
where  n  is  very  large,  this  approximates  to  (C6H1005)n,  which  represents  the 
results  of  analysis. 

F.  HIGHER  POLYOSES 

Starch,  Dextrin,  Gum,  Glycogen,  Cellulose 

STARCH,  (C6H10O5)*.  It  has  already  been  pointed  out  (pp.  Ill  and  429 
how  starch  originates  in  vegetable  organisms  and  how  it  passes  from  the 
leaves,  where  it  is  formed  under  the  influence  of  chlorophyll  and  of  light,  to 
the  reserve  stores  of  the  plants  (tubers,  seeds,  &c.  ;  in  cryptogams,  which 
have  no  chlorophyll,  starch  is  not  formed).  It  is  a  carbohydrate,  and  occurs  in 
white  granules  insoluble  in  both  cold  and  hot  water,  although  with  the  latter 
it  swells  up,  forming  starch  paste,  which  is  coloured  a  characteristic  deep  blue 
by  dilute  iodine  solution.  Starch  paste  is  dissolved  by  acids,  forming  glucose 
(see  p.  434),  and  by  diastase  (see  pp.  Ill,  116,  and  168),  forming  intermediate 
polyoses  with  less  complex  molecules  (dextrins)  and  then  maltose  and  iso- 
maltose.  Starch  does  not  give  the  reactions  of  the  monoses  (i.e.  with  Fehling's 
solution,  phenylhydrazine,  &c.),  and  hence  contains  no  free  carbonyl  groups, 
so  that  its  rational  formula  (see  pp.  438,  441,  and  442)  will  be  :  (C6H1005*0) 
.  .  .  (C6H1004-OC6H1004)  .  .  .  (0-C6H1005),  where  there  is  only  one  dicar- 
bonyl  linking,  possibly  in  the  middle  ;  two  such  linkings  are  inadmissible, 
since  otherwise  decomposition  should  give,  together  with  d-glucose,  another 
substance  with  two  carbonyl  groups.  Such  a  substance  has,  however,  never 
been  obtained. 

The  molecular  weight  has  not  been  established,  but  it  must  be  very  high, 
and,  according  to  Syniewski,  the  formula  is  C216H3600180,  the  molecule  con- 
sisting of  twelve  C18  nuclei. 

The  shape  of  the  starch  granules  varies  with  the  plant  from  which  they 
are  obtained,  so  that  it  is  possible  to  ascertain  the  origin  of  starch  by  observing 
it  under  the  microscope  (with  a  magnification  of  200  diameters  ;  see  Figs.  354 


490 


ORGANIC    CHEMISTRY 


to  361 J.1  When  examined  in  polarised  light,  between  crossed  nicols,  potato- 
starch  granules,  having  a  stratified  structure  and  an  eccentric  nucleus,  show  a 
black  cross  like  the  multiplication  sign  ( X  )  (Fig.  362),  while  other  stratified 
starch  granules  with  a  central  nucleus  also  behave  like  doubly  refracting 
crystals  but  show  a  black  cross  more  like  the  sign  of  addition  (  +  )  ;  this  is 
seen  well  with  wheat  starch  (Fig.  363).  Starch  granules  show  their  stratification 
better  under  the  microscope  if  they  are  treated  with  a  dilute  solution  of  chromic 
acid  containing  a  little  sulphuric  acid,  and  in  some  cases  dark  radial  stria3  also 
appear. 

Commercially  the  name  flour  is  given  to  starches  from  cereals,  legu- 
minosese,  acorns,  chestnuts,  &c.,  and  that  of  starch  to  those  from  potatoes, 
manihot  root,  arrowroot,  palm  stems,  sago,  &c.,  but  chemically  there  is 
no  difference.  The  flour  of  these  plants  contains  more  or  less  gluten  (wheat, 
12  per  cent.  ;  rice,  3  to  5  per  cent.),  and  wheat  yields  55  to  65  per  cent,  of 
starch  ;  maize,  60  to  65  per  cent.  ;  rice,  70  to  73  per  cent.  ;  rye,  45  per 
cent.  ;  oats,  32  per  cent.  ;  barley,  38  per  cent.  ;  beans,  peas,  and  lentils,  38 
per  cent.2  '  . 

The  specific  gravity  of  potato  starch,  when  air-dried,  is  1-5029,  and  when 
dried  at  100°,  1-6330. 

When  heated  above  160°  it  is  transformed  into  dextrin. 

Manufacture.  In  Italy  starch  is  extracted  principally  from  rice,  maize,  &c.,  but  in 
Germany  almost  exclusively  from  potatoes.  A  starch  factory  should  always  have  a  supply 
of  pure  cold  water,  not  very  hard  and  free  from  iron. 

Fresh  mature  potatoes  contain  about  20  per  cent,  of  starch  (minimum  18  per  cent., 
maximum  21  per  cent.),  the  proportion  being  determined  sufficiently  exactly  by  a  very 
rapid  physical  process,  proposed  in  1837  by  Berg,  applied  in  1845  by  Balling,  and  improved 
in  1880  by  Behrend,  Marcker,  and  Morgen.  An  exact  relation  exists  between  the  specific 
gravity  of  potatoes  and  their  starch -content,  and  it  has  been  found  that  the  difference 
between  the  total  dry  substance  (8)  and  the  starch-content  (F)  is  constant  (the  proportion 
of  non-starch,  N,  is  on  the  average  5-752  per  cent.).  So  that  a  determination  of  the  dry 
matter  gives  the  proportion  of  starch,  since  F  =  S  —  N.  Further,  if  the  relation  between 
F  and  the  specific  gravity  is  determined  once  for  all,  a  Table  3  can  be  prepared  showing 
the  proportion  of  dry  matter  or  of  starch  from  the  specific  gravity,  which  can  be  determined 
from  the  loss  in  weight  of  a  given  weight  of  potatoes  in  air  (5  kilos)  when  weighed  immerted 
in  water  ;  if,  for  instance,  this  weight  is  400  grms.,  the  loss  of  weight  will  be  46CO  gims. 
and  the  specific  gravity  5000  :  4600  =  1-087,  which  the  Table  shows  to  correspond  with 

1  Different  kinds  of  starch  may  possess  granules  of  similar  form,  but  can  be  distinguished  by  the  varying 
mean  magnitudes  of  the  granules,  although  in  most  kinds  there  are  a  greater  or  less  number  of  granules  much 
smaller  than  the  average,  these  being  sometimes  grouped  together  in  ovoidal  or  bunch-like  masses  (e.g.  rice,  oat, 
starch,  &c.).  The  average  sizes  of  the  granules  of  the  different  starches,  in  mieromiilimctres  (M),  are  generally 
as  follow : 

(1 )  Wheat :  large  granules,  26-29^,  more  common  ;  small  granules,   7jx 

(2)  Barley :       „          ,,  20/u,       ,,          ,,  ,,          ,,          4-5u. 


(3)  Rye : 

(4)  Potato  : 

(5)  Rice  •  bunches, 

(6)  Oats- 


60-80/u,       ,,          „  ,,          „        20/* 

20/u,  of  several  granules  ;  separate  granules,  5ju 
3<V,  „  „  „  ,,        8,u 

(7)  Maize  :  large  granules,    18-2CV,  more  common  ;  small  granules,   5^. 

(8)  Buckwheat :   „      „  9/u  (polyhedra)  „          „          5^ 


The  mean  percentage  compositions  of  potatoes,  wheat,  and  rice  are  as  follow  : 


Non- 

Water 

Starch 

nitrogenous 

Cellulose 

Fat 

Proteins 

Ash 

extractives 

Potatoes 

76 

18-7 

1 

0-S 

0-2 

2-1 

1-2 

Wheat.   .... 

13-5 

64 

3-8 

2-5 

2-0 

12-5 

1-7 

Rice       .... 

13-1 

76-8 

0-6 

0-6 

7-8 

1-0 

See  p.  492. 


VARIOUS    STARCHES 


491 


FIG.  354.— Rice  starch. 


FIG.  355. — Maize  starch, 
(a)  Free  granules ;  (6)  horny  part. 


FIG.  356.— Buckwheat. 


FIG.  357. — Oat  starch, 
(a)  Cellular  tissue ;  (6)  free  granules. 


FIG.  358.— Rye  starch.  FIG.  359.— Wheat  starch. 


FIG.  360.— Barley  starch. 


FIG.  361. — Potato  starch. 


FIG.  362. — Potato  starch  in  polarised  light. 


FIG.  363.— Wheat  starch  in 
polarised  light. 


492 


ORGANIC    CHEMISTRY 


21-2  per  cent,  of  dry  matter  and  154  per  cent,  of  starch.  By  means  of  the  balance  shown 
in  Figs.  364  and  365  or  of  the  Reimann  or  Schwarzer  basket  steelyard  the  potatoes  can 
be  rapidly  weighed  in  air  and  in  water  at  17-5°.  To  calculate  the  practical  yield  the  value 
given  in  the  Table  should  be  diminished  by  1  -5  per  cent.,  since  part  of  the  starch  is  converted 
during  extraction  into  soluble  sugar,  which  may  also  exist  to  a  small  extent  in  potatoes 
which  are  either  not  too  ripe  or  too  old.  The  washing  of  potatoes  in  starch  factories  is 
most  important,  and  is  carried  out  in  machines  of  various  types.  The  first  washing,  to 


FIG.  364. 


FIG.  3G5. 


remove  the  soil  and  stones,  which  are  present  to  the  extent  of  about  8  per  cent.,  can  be 
done  in  the  machine  shown  in  Pig.  103  (p.  118)  or  in  transporter  channels  like  those  used 
for  sugar-beets  (see  Fig.  293  p.  449).  The  potatoes  arc  then  raised  by  an  inclined  Archi- 
medean screw  in  a  perforated  channel  (see  Fig.  295,  p.  450),  the  washing  being  repeated 
with  copious  jets  of  water  in  a  long  vessel  having  a  concave  perforated  bottom  and  fitted 
with  vaned  stirrers,  which  are  sometimes  furnished  with  brushes  (Siemen's  washer,  Fig. 
366).  The  potatoes  pass  along  the  vessel  in  the  opposite  direction  to  that  taken  by  the 
water,  which  is  introduced  clean  at  the  extremity  where  the  washed  potatoes  emerge.  The 
washing  of  400  quintals  of  potatoes  per  24  hours  requires,  on  an  average,  20  cu.  metres 
of  water  per  hour. 

The  rasps  used  to  convert  the  potatoes  into  pulp,  by  rupturing  all  the  starch-containing 
cells,  consist  of  a  number  of  saw-edged  steel  plates  fixed  radially  round  a  drum  which  has 


Weight  in 
water  of 
5  kilos  of 
potatoes, 
grms. 

2  x 

ft  g 
•f~    -1. 

Dry  matter,  1 
per  cent. 

t-r     o 

-2     K 

s& 

Weight  in 
water  of 
5  kilos  of 
potatoes, 
grms. 

<C  & 
°0  '£ 

ft  8 

CO    tC 

!! 

g& 

Starch, 
per  cent. 

Weight  in 
water  of 
5  kilos  of 
potatoes, 
grms. 

CC    -J-* 

11 

GO    ttl 

Dry  matter,  1 
per  cent. 

Starch, 
per  cent. 

375 

I  -080 

19-7 

13-9 

480 

1-106 

25-2 

19-4 

585 

1-132 

30-8 

25-0 

380 

1-081 

19-9 

14-1 

485 

1-107 

25-5 

19-7 

590 

1-134 

31-3 

25-5 

385 

1-083 

20-3 

14-5 

490 

1  109 

25-9 

20-1 

595 

1-135 

31-5 

25-7 

390 

1-084 

20-5 

14-7 

495 

1-110 

26-1 

20-3 

600 

1-136 

31-7 

25-9 

395 

1-036 

20-9 

15-1 

500 

1-111 

26-3 

20-5 

•   605 

1-133 

32-1 

26-3 

400 

1-087 

21-2 

15-4 

505 

1-112 

26-5 

20-7 

610 

1-139 

32-3 

26-5 

405 

1-088 

21-4 

15-6 

510 

1-113 

26-7 

20-9 

615 

1-140 

32-5 

26-7 

410 

1-089 

21-6 

15-8 

515 

1-114 

26-9 

21-1 

620 

1-142 

33-0 

27-2 

415 

1-091 

22-0 

16-2 

520 

1-115 

27-2 

21-4 

625 

1-143 

33-2 

27-4 

420 

1-092 

22-2 

16-4 

525 

1-117 

27-6 

21-8 

630 

1-144 

33-4 

27-6 

425 

1-093 

22-4 

16-6 

530 

1-119 

28-0 

22-2 

635 

1-146 

33-8 

28-0 

430 

1-094 

22-7 

16-9 

535 

1-120 

28-3 

22-5 

640 

1-147 

34-1 

28-3 

435 

1-095 

«22-9 

17-1 

540 

1-121 

28-5 

22-7 

645 

1-148 

34-3 

28-5 

440 

1-097 

23-3 

17-5 

545 

1-123 

28-9 

23-1 

650 

1-149 

34-5 

28-7 

445 

1-098 

23-5 

17-7 

550 

1-124 

29-1 

s23-3 

655 

1-151 

34-9 

29-1 

450 

1-099 

23-7 

17-9 

555 

1-125 

29-3 

23-5 

660 

1-152 

35-1 

29-3 

455 

1-100 

24-0 

18-2 

560 

1-126 

29-5 

23-7 

665 

1-153 

35-4 

29-6 

460 

1-101 

24-2 

18-4 

565 

1-127 

29-8 

24-0 

670 

1-155 

35-8 

30-0 

465 

1-102 

24-4 

18-6 

570 

1-129 

30-2 

24-4 

675 

1-156 

36-0 

30-2 

470 

1-104 

24-8 

19-0 

575 

1-130 

30-4 

24-6 

680 

1-157 

36-2 

30-4 

475 

1-105 

25-0 

19-2 

580 

1-131 

30-6 

24-8 

685 

1-159 

36-6 

30-8 

493 

a  diameter  of  50  to  60  cm.  (Figs.  367  and  368)  and  rotates  at  a  speed  of  800  to  1000  revo- 
lutions per  minute.  The  Angele  rasp  (Fig.  369)  consists  of  such  a  drum  working  in  a  cylin- 
drical casing,  which  in  some  forms  has  a  saw-toothed  inner  surface  (Schmidt  rasp,  Fig.  370), 
the  potatoes  from  the  feeder  being  forced  against  the  drum  by  means  of  an  adjustable 


FIGS.  367  AND  368. 


FIG.  369. 


wooden  compressor,  A,  and  the  resulting  pulp  drawn  between  the  two  indented  surfaces- 
A  powerful  water -jet  keeps  the  saw-edges  clean  and  washes  the  pulp  into  a  tank  under. 

neath.     The  pulp  from  which  the  starch  has  

been  removed  (100  quintals  of  potatoe :  give 

3  to  4  quintals  of  dried  residues)  still  contains 

unaltered  starchy  cells,  and  as  a  loss  of  2  to  3 

per  cent,  of  starch  would  thus  result,  the  pulp 

is  passed  into  ordinary  horizontal  stone  mills 

like  those  used  in  flour-mills,  the  stones  having 

a  diameter  of  about  a  metre  and  making  150 

turns   per  minute.      The    Champonnois  rasp, 

used  in  France,  is   composed  of  a  drum,   E 

(Figs.  371  and  372),  formed  of  a  number  of 

saw-blades  with   the   teeth  turned   inwards  ; 

the  washed  potatoes  enter  by  the  feeder,  /, 

and  are  forced  against  the  saw-edged  periphery 

by  the  blades,  F,  which  are  rapidly  rotated  by 

the  pulley,  H.     A  water -jet  supplied  at  K  washes  the  pulp  between  the  saw-blades  into 

the  vessel,  N,  below,  loss  by  spurting  being  prevented  by  the  casing,  M. 

For  large  factories,  however,  Uhland  has  suggested  the  replacement  of  the  mill  by  a 
special  machine  which  completely  disintegrates  the  remaining  starch-containing  cells 


FIG.  370. 


494 


ORGANIC   CHEMISTRY 


without  rupturing  the  fibres.  This  machine  consists  of  a  horizontal  cone  of  cast-iron, 
either  chinn-lled  or  edged  (Figs.  373  and  374)  and  enclosed  in  a  casing  of  similar  shape  '; 
by  means  of  a  screw  regulator,  V,  the  distance  between  the  cone  and  casing  can  be  varied! 


FIG.  374. 

The  coarse  paste  is  introduced  by  a  hopper  and  fed  on  to  the  cone,  C,  by  the  blades,  S, 
being  subsequently  discharged  through  the  channel,  R. 

In  order  to  separate  the  starch  granules  from  the  residual  pulp,  which  holds  in  solution 
the  vegetable  juice  and  in  suspension  the  cellular  residues  of  the  vegetable  tiesues,  epi- 
dermis, &c.,  the  pulp  is  passed  immediately  (to  avoid  fermentation)  on  to  copper  sieves 


495 


of  various  typas  (usually  semi-cylindrical  and  several  metres  in  length)  ;  these  retain  the 
residues,  while  a  water-spray,  helped  by  suitable  scrapers,  carries  the  starch  granules 
through  the  meshes  (see  transverse  section,  Fig.  375)  ;  these  same  scrapers,  which  are 
arranged  helically,  carry  the  exhausted  residues  to  the  far  end  of  the  sieve  and  keep  the 
latter  clean. 

When  these  operations  are  carried  out  properly  and  in  large  works,  the  total  loss  is 
not  more  than  0-3  kilo  of  dry  starch  on  100  kilos  of  washed  potatoes  ;  these  losses  are 
detected  by  estimating  chemically  the  starch  in  the  ultimate 
exhausted  residues. 

The  milky  liquid  collected  under  the  sieves  also  contains, 
in  addition  to  starch,  small  proportions  of  colouring  and 
gummy  matters,  proteins,  dextrin,  and  very  fine  particles  of 
epidermis,  sand,  &c.  In  order  to  separate  these  impurities,  the 
starch-milk  is  introduced  into  large  concrete  vessels,  where 


But  in  some  cases  the  starch  is  subjected  to  levigation  with  a 

gentle  current  of   water  in  a  number  of  vessels,  in  which  the  FIG.  375. 

starch  forms  successive  deposits.     The  water  and  the  dissolved 

impurities  are  readily  separated,  either  during  or  after  standing,  by  means  of  a  floating 

syphon  consisting  of  a  funnel  joined  to  an  india-rubber  tube  (Fig.  376).  The  volume  of 
the  deposit  tanks  is  taken  to  be  about  1  cu.  metre  per  quintal 
of  potatoes  treated. 

In  some  starch  factories  the  starch  is  still  separated  from  the 
milky  liquid  by  a  kind  of  levigation  on  inclined  planes,  the 
liquid  passing  slowly  along  large  wooden  or  cement  channels, 
30  metres  long,  1  to  3  metres  wide,  50  to  60  cm.  deep,  and  with 
a  slope  of  3  to  5  mm.  per  metre.  The  coarser  starch,  together 
with  a  little  sand,  is  deposited  in  the  first  parts  of  the  channel ; 
then  comes  the  best  starch,  while  the  smallest  granules,  mixed 
FIG.  376.  wit^  a  *ew  organic  impurities,  are  the  last  to  settle.  The  water 

which  emerges  from  the  end  of  the  channel  is  passed  through 

two  or  three  depositing  tanks  before  being  rejected.     In   order  that  the  working  may 

be  continuous,  two   channels  Nare   always  employed, 

one  being  in  use  while  the  starch  is  being  removed 

from   the   other.     The   channels   are  fed  from  large 

reservoirs  provided  with  stirrers  so  that  the  density 

of  the  starch  suspension  may  be  kept  constant  and 

uniform  (3°  Be.,  the  liquid  being  fed  at  the  rate  of  6 

litres  per  minute  per  2-5  sq.  metres  of  channel  surface). 

The  crude  starch  from  the  first  and  last  portions  of 

the  channel  may  be  purified  by  repeating  the  leviga- 
tion.    But  that  obtained  from  depositing  tanks  forms 

a  compact  mass  composed  of  a  lower  layer  of  coarse 

granules   mixed  with  a  little  sand,  an  intermediate 

purer  layer,  and  a  grey  uppermost  layer  mixed  with 

organic   detritus.     It  is  indispensable   to  wash  the 

starch  quickly,  as  in  time  the  impurities  impart  to 

it  a  pale  yellow  colour.     For  this  purpose  the  layer  of 

starch — the  so-called  green  starch  (i.e.  impure,  moist 

starch) — is  covered  with  double  its  depth  of  water,  a  suspended  stirrer  fitted  with  long 

blades  (Fig.  377)  being  then  lowered  to  the  surface  of  the  starch  ;  the  first  more  impure 

layer  is  thus  stirred  up  so  as  to  form  a  dense  milk  of  4°  to  5°  Be.,  this  being  deposited 

in  an  adjacent  wooden  vat  or  on  the  inclined  channel.     The  middle  purer  layer  is  then 

stirred  up  and  the  suspension  removed,  and  so  on. 

In  these  wooden  vats  (see  Fig.  377)  the  stirring  is  repeated,  this  operation  being  con- 
tinued until  a  perfectly  white  starch  is  obtained,  the  wash-waters  being  removed  after 

each  deposition. 


FIG.  377. 


496 


ORGANIC    CHEMISTRY 


When  the  starch  is  not  refined  in  this  way  and  dried,  the  growth  of  mould  is  prevented 
by  keeping  it  under  water  slightly  acidified  with  sulphuric  acid  until  it  is  to  be  sold.  This 
green  starch,  which  is  used,  for  example,  for  manufacturing  glucose,  contains  about  50  to 
55  per  cent,  of  water  ;  part  of  this  can  be  removed  in  centrifuges  similar  to  those  used 
for  sugar  (p.  469),  the  perforated  drum  being  coated  inside  with  a  fine  cloth  to  retain  the 
granules.  The  superficial  layer  of  the  cake  of  starch  is  scraped  off,  as  it  contains  impurities, 
and  the  remainder  (with  35  to  40  per  cent,  of  moisture)  then  discharged  below  ;  with  a 
drum  80  cm.  in  diameter  50  kilos  of  starch  are  obtained.  The  centrifuges  are  fed  with  a 

dense  suspension  of  the  starch  of 
20°  Be.  The  impure  grey  starch 
obtained  in  the  secondary  sedi- 
mentation vessels  is  mixed  to  a 
dense  milk  and  passed  through 
fine  silk  sieves,  which  retain  the 
detritus  and  solid  proteins,  &c., 
the  sieved  milk  being  conveyed  to 
other  finer  sieves  and  then  to  the 
FIG.  378.  .  inclined  channels  or  sedimenta- 

tion vats.     To  prevent  bacterial 

action  and  to  increase  the  whiteness  of  starch,  0-5  kilo  or  more  of  calcium  bisulphite  solu- 
tion (in  some  cases  sulphurous  acid  is  used)  is  sometimes  added  to  each  cubic  metre  of  the 
milk.  These  reagents,  as  well  as  sulphuric  acid  or  caustic  soda  in  small  proportions,  facili- 
tate the  deposition  of  the  starch  in  the  tanks,  but  they  impart  a  faint  reaction  to  the  final 
starch,  and  it  is  advisable  to  employ  them  only  in  the  treatment  of  frozen  or  bad  potatoes, 
where  the  product  readily  ferments  and  turns  yellow.  Bleaching  is  sometimes  effected  with 
dilute,  filtered  calcium  hypochlorite  solution  (1  :  300),  together  with  sulphuric  acid  ;  after 
a  few  minutes  contact,  the  starch  is  washed  in  an  abundant  supply  of  cold  water  until 
the  reaction  of  the  chlorine  disappears.  The  last  trace  of  yellow  in  the  starch  can  be 
corrected  by  slight  blueing  with  ultramarine,  indigo  carmine,  Prussian  blue,  &c. 

When  potato  or  cereal  starch  is  to  be  prepared  in  cubical  or  similar  cakes,  the  mass 
from  the  sedimentation  tanks  is  introduced  into  moulds  of  galvanised  or  tinned  iron  with 


perforated  bases  (the  cubes  are  16  cm.  in  each  direction)  ;  these  are  either  enclosed  in 
evacuated^cases  or,  as  Uhland  suggested,  subjected  to  considerable  air-pressure,  so  as 
to  remove~the  water  as  far  as  possible  (see  Fig.  378).  Fig.  379  shows  how  the  batteries 
of  moulds  are  arranged  in  large  factories  ;  the  dense  starch-cream  from  the  vat  fills  a 
hopper  travelling  on  a  suspended  iron  rail  and  stopping  above  each  mould  to  fill  it  ;  when 
all  the  moulds  are  full,  they  are  closed  hermetically  and  the  air-compressor  started.  With 
a  suitable  machine  the  smooth  cakes  are  removed  whqle  from  the  moulds,  and  as  they 
contain  very  little  water,  the  time  required  for  drying  is  considerably  shortened. 

Modern  plants  make  use  of  another  arrangement  devised  by  Uhland  (Fig.  380).  Here 
the  moulds  are  fitted  inside  with  a  rubber  bag  with  a  perforated  base  and  covered  with 
cloth  ;  this  fits  closely  to  the  walls  and  gives  a  purer  starch,  while  the  moulds  can  be 
thoroughly  cleaned  after  each  operation. 


WHEAT    STARCH  497 

The  drying  of  the  starch  is  carried  out  in  hot -air  desiccators,  which  readily  reduce  the 
moisture  to  20  per  cent.,  which  is  the  customary  proportion  ;  if  more  moisture  is  present 
an  allowance  is  made  to  the  purchaser,  but  if  there  is  less  than  20  per  cent,  the  seller  loses, 
as  no  allowance  is  then  made.  In  order  to  obtain  starch  of  good  appearance  the  tem- 
p3rature  of  drying  should  be  about  30°  to  35°  (at  50°  it  begins  to  swell  and  form  lumps) 
and  the  air  should  issue  from  the  desiccator  almost  saturated  with  moisture  after  traversing 
all  the  frames  or  gratings  on  which  the  moist  starch  is  spread  in  a  thir  layer  or  in  cakes. 
The  best  arrangement  consists  of  channels  or  galleries  10  to  12  metres  long,  1-2  metre 
wide,  and  2  metres  high,  through  which  trolleys  carrying  the  frames  pass  from  one  end 
to  the  other  ;  the  hot,  dry  air  is  injected  under  slight  pressure  in  the  opposite  direction  by 
a  large  helical  fan,  gentle  suction  being  applied  at  the  far  end  if  necessary.  Rapid  drying 
depends  not  so  much  on  the  temperature  as  on  the  supply  of  the  proper  amount  of  pure, 
dry  air.  The  doors  of  the  drying  tunnel  slide  up  and  are  opened  just  sufficiently  to  allow 
of  the  entry  and  exit  of  the  trolleys  from  time  to  time  (every  hour). 

It  has  recently  been  proposed  to  employ  mechanical  dryers  consisting  of  a  number 
of  stories  fitted  with  endless  bands,  or  of  long  revolving  cylinders,  while  in  some  cases 
drying  in  a  vacuum  has  been  practised  as  with  distillery  residues  (see  Fig.  149,  p.  154), 
time  and  space  being  thus  economised  and  the  output  consequently  greatly  increased. 

The  dried  starch  forms  friable 
lumps,  and  to  obtain  it  in  powder 
it  is  passed  first  into  grooved  cylin- 
ders and  then  into  sieves  similar  to 
those  employed  in  mills.  For  the 
use  of  ball-mills,  see  vol.  i,  pp.  512 
and  588.  Statistics,  see  later.  Micro- 
scopical examination,  see  p.  491. 

Yield  of  Starch  and  Treatment  of 
Residues.  Of  20  kilos  of  starch  pre- 
sent in  potatoes,  17  to  18  are  usually 
obtained  in  the  pure,  dry  state,  the  FIG.  380. 

rest  going  into  the  residues.     The 

moist  pulp,  freed  from  starch  (within  0-5  per  cent.),  contains  the  parenchyma  and  epidermis 
of  the  potatoes,  which  are  composed  largely  of  cellulose  saturated  with  aqueous  juices. 
The  pressed  pulp  (about  16  per  cent,  of  the  weight  of  the  potatoes),  which  is  sometimes 
dried  (it  then  constitutes  3  to  4  per  cent,  of  the  weight  of  the  potatoes  and  contains  50 
to  60  per  cent,  of  starch),  forms  a  good  cattle-food,  either  alone  or  mixed  with  bran,  chaff, 
&c.  It  is  dried  in  the  vacuum  apparatus  used  for  "  grains  "  (see  p.  154)  or  for  beet-pulp 
(see  Fig.  309,  p.  455).  The  waste  waters  contain  potash  salts  (0-06  per  cent.  K2O  +  0-017 
per  cent.  P205  +  0-1  per  cent,  ash  +  0-24  per  cent,  sugar  +  0-12  per  cent,  gum  +  0-17 
per  cent,  nitrogenous  substances)  and  may  be  used  for  irrigating  pasture  land  ;  if  it  is 
not  digested  quickly  it  undergoes  fermentation.  These  waters  are  readily  clarified  by 
colloidal  aluminium  hydroxide.  The  moist,  non-pressed  pulp  has  the  following  percentage 
composition:  water,  86;  protein,  0-7  to  0-9;  fat,  0-1  ;  starch  and  extractives,  11-2; 
cellulose,  1-5  ;  ash,  0-4. 

WHEAT  STARCH.  Since  wheat  also  contains,  in  addition  to  56  to  65  per  cent,  of 
starch,  12  to  16  per  cent,  of  gluten,  the  separation  of  the  latter  renders  the  preparation  of  the 
starch  more  difficult.  By  the  fermentation  process  (Halle)  the  gluten  is  rendered  soluble 
and  consequently  lost,  so  that  only  wheats  containing  little  gluten  are  treated  in  this 
manner.  The  non -fermentation  process,  in  which  the  gluten  is  recovered,  is  the  one  usually 
employed,  more  especially  because  no  large  amount  of  bad-smelling  liquor  is  formed,  as 
is  the  case  with  the  other  method. 

In  the  fermentation  process  the  wheat  is  cleared  and  steeped  in  water  in  apparatus 
similar  to  that  used  with  barley  to  be  malted  (see  Fig.  153,  p.  163).  When  sufficiently  soft 
to  be  squeezed  between  the  fingers,  the  wheat  is  passed  between  a  pair  of  smooth  rolls 
which  break  the  epidermis  without  crushing  it  too  much.  The  mass  is  placed  in  large 
tanks  and  covered  with  the  acid  liquid  from  a  previous  fermentation,  alcoholic  fermenta- 
tion starting  in  a  few  days  and  being  followed  by  acid  fermentations  (lactic,  butyric,  acetic, 
&c.)  with  evolution  of  gas  ;  the  fermentation  is  complete  in  10  or  12  days  in  summer  or 
20  days  in  winter,  the  liquid  being  then  clear,  yellow,  and  covered  with  mould,  but  not 
II  •  32 


498  ORGANIC    CHEMISTRY 

yet  smelling.  The  acid  liquid  is  decanted  off,  and  the  starch  separated  from  the  bran  in  a 
finely  perforated  drum  under  a  current  of  water.  The  solid  residue  serves  as  cattle-food, 
while  the  starch-milk  is  allowed  to  deposit  in  the  ordinary  vats,  where  it  is  washed  ;  it  is 
then  conveyed  to  the  fine  sieves  and  inclined  channels  (see  under  Potato  Starch).  The 
pure  starch  separated  in  this  way  should,  however,  contain  a  small  proportion  of  gluten, 
since,  during  the  drying,  this  facilitates  the  formation  of  so-called  crystals  desirable  in  the 
commercial  product. 

The  crude  starch-milk  can  be  purified  more  rapidly  in  the  Fesca-Decastro  centrifuge, 
which  has  a  non -perforated  drum.  The  purer  starch  is  deposited  first  in  a  compact  layer 
on  the  inner  surface  of  the  basket  and  the  less  pure  starch-milk  remaining  is  discharged 
automatically  before  it  deposits  its  impurities,  new  starch-milk  being  introduced  and 
treated  similarly  until  a  thick  layer  of  moderately  pure  starch  is  obtained.  The  centrifuge 
is  stopped,  the  water  discharged  from  the  middle,  and  the  yellowish,  superficial  portion 
of  the  starch,  which  contains  gluten,  &c.,  removed  with  a  sponge.  The  starch  is  then 
discharged,  mixed  with  water  in  a  vat  fitted  with  a  stirring  arrangement,  and  the  starch- 
cream,  sometimes  after  a  little  ultramarine  or  indigo  carmine  has  been  added,  introduced 
into  the  suction  moulds. 

The  drying  of  the  cakes  (see  Potato  Starch)  is  carried  out  immediately  (to  avoid  mould- 
growth),  and  in  winter-time  this  is  done  in  an  oven,  the  temperature  of  which  is  raised  from 
30°  to  75°  ;  in  the  summer  the  drying  is  begun  in  the  air.  When  a  certain  stage  is  reached 
in  the  drying  process,  the  cakes  shrivel  at  the  surface  ;  this  less  pure  portion  is  removed 
and  the  cakes  broken  into  smaller  blocks,  which  are  wrapped  in  paper  and  dried  further. 
Under  this  treatment  the  mass  gradually  assumes  the  radiating  structure.1 

In  the  non-fermentation  process  the  crushed  wheat  is  treated  with  a  stream  of  water, 
being  manipulated  meanwhile  in  the  form  of  a  paste,  which  is  placed  on  perforated  channels 
or  sieves  so  that  the  whole  of  the  starch  is  gradually  removed  and  the  pasty  gluten  left. 
The  starch  is  then  deposited  in  the  ordinary  manner,  while  the  gluten  is  transferred  to 
rotating  cylinders  with  their  inner  surfaces  covered  with  points,  which  retain  the  pure 
gluten  2  ;  the  bran  is  washed  away  with  water. 

According  to  a  suggestion  by  Fesca,  the  dry  ground  wheat  is  mixed  with  water  and 
the  paste  introduced  into  a  centrifuge  with  a  perforated  drum,  the  starch  being  separated 
by  a  continuous  current  of  water,  while  the  gluten  remains  in  the  centrifuge  ;  the  further 
operations  are  as  usual.  The  Fesca  process  is  very  simple  and  more  convenient  than  that 
described  above.  The  average  yields,  calculated  as  percentages  on  the  wheat,  are  as  follow  : 
first  quality  starch,  air-dried,  54  ;  gluten  flour,  12  ;  bran,  mixed  with  a  little  gluten  and 
starch,  19-5  ;  matters  dissolved  in  the  waste  water,  14. 

Statistics,  see  later.     Microscopical  examination,  see  p.  491. 

RICE  STARCH.  On  the  average,  rice  3  contains  77  per  cent,  of  starch  and  less  gluten 
(4  to  5  per  cent.)  than  wheat,  but  the  starch  is  more  difficult  to  separate  (for  1  part  of  gluten 

1  Wheat  flour  attains  its  maximum  whiteness  30  to  60  days  after  grinding  and  retains  it  until  about  the  sixth 
month,  after  which  it  slowly  darkens.     In  America  various  patents  have  been  filed,  during  the  last  few  years, 
for  obtaining  this  maximum  whiteness  more  rapidly  by  treating  the  flour  with  ozone,  chlorine,  bromine,  sulphur 
dioxide,  &c.,  but  better  results  are  obtained  with  nitrogen  peroxide  (NO.).    According  to  some  observers,  flours 
bleached  in  this  way  begin  to  darken  earlier,  irregular  staining  taking  place.    The  process  which  has  given  the 
most  favourable  results  and  has  been  largely  applied  in  America  and  recently  also  in  Italy,  is  that  of  Wesener 
(Ger.  Pats.  209,550  and  232,204),  according  to  which  flour  is  bleached  instantaneously  in  contact  with  a  current 
of  air  containing  mere  traces  of  nitrosyl  chloride  (see  vol.  1,  p.  335) ;   1  kilo  of  the  latter  is  sufficient  to  bleach 
1000  quintals  or  even  more  of  flour. 

2  In  presence  of  a  little  water  and  at  a  moderate  temperature,  the  gltUen  thus  obtained  undergoes  a  slight 
fermentation  and  becomes  liquid ;    when  dried  in  thin  layers  on  metal  plates,  this  is  obtained  in  transparent 
sheets,  which  are  used  as  a  glue  in  the  manufacture  of  boots.     Or  the  gluten  is  mixed  with  5  per  cent,  of  powdered 
salt  and  made  into  strings  in  presses  ;  the  strings  are  dried  in  an  oven  when  they  become  friable  and  readily  con- 
vertible into  flour,  which  is  used  in  the  preparation  of  dough  and  serves  as  a  foodstuff  when  mixed  with  other  products. 

3  The  mean  annual  production  of  rice  in  Italy  from  1870  to  1874  was  9,800,000  hectols. ;    in  1907  it  was 
10,450.000  ;  and  in  1908,  9,393,000  hectols..    The  exports  in  1905  were  11,450  tons  of  raw,  3414  of  semi-raw,  and 
44,178  of  prepared  rice  ;  the  respective  numbers  of  tons  were  7850,  6450,  and  40,120  in  1907,  and  7691,  1936,  and 
35,274  in  1909.     A  hectolitre  of  rice  weighs  50  to  60  kilos. 

Rice  (Oryza  saliva)  is  an  annual  plant  belonging  to  the  Graminese  indigenous  to  Eastern  India  and,  according 
to  some,  to  Ethiopia.  In  Europe  it  is  cultivated  principally  in  Italy  and  also  in  Spain  and  in  the  south  of  Russia, 
particularly  on  irrigable  lands.  In  Japan  and  Brazil  it  is  grown  in  the  moist  soil  of  warm,  rainy  regions,  while 
in  America  it  is  extensively  cultivated  in  Florida  and  Southern  Carolina.  In  rice-plantations  the  bottom  of  the 
plant  is  kept  under  almost  stagnant  water,  and,  on  account  of  the  miasmata,  which  cause  malaria,  the  fields 
should  be  at  some  distance  from  any  habitation  ;  the  ripening  of  the  head  is  brought  about  by  the  intense  heat 
of  summer.  After  the  harvest  the  rice  is  separated  from  the  ear  by  means  of  suitable  machines  (threshers),  but 
still  retains  the  glumes  or  husk,  being  known  as  paddy  rice.  This  is  separated  from  the  residues  by  means  of  con- 
centric toothed  cylinders  and  is  then  sieved  and  placed  between  two  light,  horizontal,  stone  discs  (or  brahmin). 


RICE    STARCH  499 

about  1  part  of  starch  is  lost).    Of  all  the  processes  which  have  been  suggested,  that  devised 
by  Orlando  Jones  in  1840  still  gives  the  best  results.    Uso  is  generally  made  of  waste  rice 
(broken  rice,  costing  14s.  to  24s.  per  quintal  according  to  the  season),  which  is  softened 
in  a  large  galvanised  iron  or  iron  steeping  cylinder  with  a  conical  base,  by  means  of  dilute 
solutions  of  caustic  soda  (0-3  per  cent,  in  winter,  0-5  per  cent,  in  summer).    Here  it  is  left 
for  5  to  15  hours,  being  mixed  every  3  to  5  hours  with  a  vigorous  air-jet  ;  in  winter  the 
alkali  solution  is  heated  to  20°.    The  duration  of  the  steeping  varies  with  the  quality  of 
the  rice  and  with  the  season  of  the  year  ;  Italian  rice  requires  5  to  6  hours  and  Rangoon 
rice  as  much  as  14  hours,  the  soda  solution  being  changed  in  the  latter  case  after  six  or 
eight    hours.    After  steeping,  the  rice  can  be  readily  crushed  between  the  fingers.    The 
dissolved  gluten  (20  to  30  grms.  per  litre)  is  separated  from  the  alkaline  liquid  simply  by 
acidification  with  sulphuric  acid  (in  order  to  bring  the  gluten  into  such  a  condition  that 
it  can  be  filtered  in  a  filter-press,  the  temperature  is  raised  to  80°  or  1  kilo  of  lime  is  added 
per  cubic  metre  of  the  alkaline  solution).     In  some  cases  the  gluten  is  extracted  with  an 
alkaline  liquid  in  an  apparatus  similar  to  beet-diffusors  (see  p.  451),  while  in  others  the 
extraction  is  carried  out  in  a  vacuum  with  agitation.    The  swollen  and  softened  rice,  con- 
taining a  little  of  the  alkaline  solution,  is  then  ground  between  horizontal  millstones,  a 
liquid  paste  with  22  to  26  per  cent,  of  starchy  matter  being  obtained  ;    this  is  pumped 
up  into  large  square  cement  tanks  provided  with  stirrers  (see  Fig.  377),  where  it  is  treated 
with  more  dilute  caustic  soda  solution  (0-2  per  cent.),  care  being  taken  in  summer  that 
the  temperature  does  not  rise  sufficiently  to  admit  of  fermentation.    In  these  tanks  the 
.separation  of  the  starch  from  the  liquid  occupies  about  1^  hours  after  the  stirring  is  stopped. 
The  liquid  is  decanted  and  the  residual  starch  mixed  with  a  fresh  quantity  of  0-2  per  cent. 
NaOH  solution  and  left  for  45  minutes  to  settle.    In  some  cases  this  washing  is  repeated 
a  third  and  fourth  time,  the  thin  surface  layer  of  yellow  starch  containing  gluten,  &c., 
being  scraped  off  each  time  before  adding  fresh  washing  water  ;   the  scrapings  from  the 
first  and  second  settlings  are  ground  again  in  the  stone  mill,  sieved,  and  mixed  with  the 
other  starch.   After  the  final  washing,  for  which  water  is  used,  the  starch-milk  is  conveyed 
to  other  cement  depositing  tanks,  being  previously  passed  through  oscillating,  inclined 
silk  sieves  or  through  revolving  perforated  cylinders  sprayed  outside  with  water  to  prevent 
obstruction  by  impurities  or  by  solid  gluten  (the  gluten  separates  best  with  rather  hard, 
chalky  water).     The  deposited  starch  is  mixed  with  water  and  centrifuged  in  a  non-per- 
forated drum  in  the  manner  employed  for  wheat  starch,  the  yellow  surface  layer  being 
removed  with  a  sponge.    Finally,  it  is  made  into  a  thick  paste  (24°  Be.  or  about  50  per 
cent,  of  water  ;  alkalinity  less  than  0-2  per  cent.)  with  water  and  moulded  under  an  air- 
pressure  of  two  atmospheres  or  with  a  suction-pump  giving  a  vacuum  of  600  mm.  (see 
Figs.  378,  379,  380)  ;    the  starch  has  not  a  very  bright  appearance  if  made  into  cakes 
immediately  it  leaves  the  centrifuge.    In  this  way  blocks  containing  40  to  50  per  cent,  of 
water  are  obtained,  and  these  are  subjected  to  a  preliminary  drying  in  an  oven  at  40°  to 
45°  ;  after  5  to  8  days  the  mass  contains  30  per  cent,  of  water  and  is  shrivelled  at  the 
surface,  owing  to  efflorescence  of  the  gluten,  &c.    This  impure,  yellow  portion,  which  may 
constitute  15  per  cent,  of  the  whole,  is  sawn  off,  washed,  centrifuged,  filter-pressed,  and 
then  either  treated  again  or  dried  and  sold  as  a  lower -grade  product.   The  remaining  blocks 
are  dried  further  in  the  air  or,  more  commonly,  after  wrapping  in  paper,  in  an  oven,  where 
the  temperature  is  raised  to  25°  in  two  days,  to  28°  on  the  third,  and  then  slowly  to  32° 
or  35°.    In  15  to  20  days  the  mass  contains  12  per  cent,  of  water  and  is  crystallised  com- 
pletely in  long,  fragile  needles  with  irregular  surfaces  ;  these  blocks  are  then  exposed  to 
the  air  (sheltered  from  dust),  the  normal  moisture-content  of  15  to  18  per  cent,  being  thus 

one  of  which  is  fixed  while  the  other  revolves  ;  in  this  way  the  husk  is  removed.  The  husk  was  formerly,  and  to 
some  extent  is  now,  separated  from  the  rice  by  means  of  vertical  pestles,  which  fall  automatically  but  without 
touching  the  bottom  of  the  mortar  filled  with  the  rice  ;  the  grains  of  rice  are  thus  rubbed,  one  against  the  other, 
and  the  husk  removed.  The  complete  removal  of  the  husk  and  dust  is  effected  by  means  of  a  simple  vertical 
mill  similar  to  the  double  one  used  for  black  powder  (Fig.  210)  and  making  30  to  40  turns  per  minute.  The  rice 
is  finally  polished  in  a  double  vertical  conical  apparatus,  the  inner  cone  of  which  is  provided  with  brushes  of 
vertical  metal  wires  and  revolves  at  the  rate  of  200  turns  per  minute,  and  rubs  the  rice  against  the  outer  perforated 
cone ;  the  polished  rice  is  discharged  at  the  bottom.  100  kilos  of  paddy  rice  give  77  kilos  of  dehusked  rice,  or 
67  of  commercial  rice,  or  63  of  unpolished  or  partially  polished  rice,  or  59  of  polished  rfce.  The  residues  consist 
of  about  1-5  per  cent,  waste,  20  per  cent,  of  husk,  2-5  per  cent,  of  risin,  and  8-5  per  cent,  of  meal,  which  is  used 
as  fodder,  and  contains,  on  an  average,  12-5  per  cent,  of  fat,  13  per  cent,  of  total  protein,  5  per  cent,  of  cellulose, 
45  per  cent,  of  extractives,  and  8  per  cent,  of  ash.  Italy  has  about  140,000  hectares  under  rice,  a  hectare  of  good 
rice  land  yielding  60  to  70  hectols.  of  rice.  The  following  prices  were  quoted  for  rice  in  October  1911  :  Paddy  rice; 
Ostiglia,  17s.  6d. ;  Japanese,  13*.  6d. ;  Burmese,  15s.  per  quintal ;  Ostiglia  rice,  first  quality,  36s.  10d.,  third  quality, 
848. ;  Burmese,  28s. ;  firstjiuality  Japanese,  26s.  6d. 


500  ORGANIC    CHEMISTRY 

acquired  (the  alkalinity  is  usually  below  0-15  per  cent.).  According  to  Ger.  Pat.  205,763, 
the  formation  of  needles  is  accelerated  by  drying  the  moist  starch  rapidly,  grinding  and 
compressing  in  the  moulds  ;  the  cakes  are  then  wrapped  in  paper  and  placed  in  the  ordi- 
nary channel  ovens,  through  which  warm,  moist  air  is  passed.  The  starch  may  be  bleached 
in  the  ordinary  way  with  sulphur  dioxide  and  blued  with  ultramarine  (about  150  to  200 
grms.  being  added  per  500  litres  of  dense  cream  before  introducing  it  into  the  moulds). 
Difficulties  are  often  encountered  in  the  manufacture  of  rice  starch,  owing  to  the  readiness 
with  which  fermentation  occurs,  this  leading  to  generation  of  gas  and  to  trouble  in  the 
settling  and  clearing  of  the  liquids  ;  the  remedy  lies  in  increasing  the  concentration  of 
the  alkali  employed  or  in  the  use  of  sulphur  dioxide. 

Rice  starch  is  employed  largely  for  making  face  powder  and  almost  exclusively  for 
the  starching  of  linen,  a  gloss  being  obtained  in  the  latter  case  by  the  addition  of  borax 
(6  to  8  per  cent.),  finely  powdered  stearic  acid  (2  to  3  per  cent.),  &C.1 
Statistics,  see  later.     Microscopical  examination,  see  p.  491. 

MAIZE  STARCH.  The  maize,  which  has  an  average  starch-content  of  62  to  65  per  cent., 
is  softened  in  tepid  water  for  three  or  four  days  and  ground  coarsely,  the  germ  and  bran 
being  then  separated  and  the  remaining  flour  treated  several  times  with  sulphurous  acid. 
It  is  then  sieved  and  the  resulting  starch-milk  treated  as  usual  in  sedimentation  tank?, 
the  last  portions  of  gluten  being  removed.  The  form  of  the  granules  is  shown  on  p.  491. 
SOLUBLE  STARCH.  This  is  used  in  large  quantities  as  a  dressing  for  textile  fibres 
and  as  an  adhesive.  It  is  prepared  by  the  action  on  starch  at  different  temperatures  of 
many  different  reagents,  such  as  alcohol  and  water,  caustic  soda,  sulphuric  acid,  calcium 
hypochlorite,  gaseous  chlorine,  ammonium  persulphate,  hydrogen  peroxide,  formic  acid, 
gaseous  hydrogen  chloride,  diamalt  (a  dense  diastase  syrup  or  malt  extract,  known  in 
Germany  as  diastofor),  hydrofluosilicic  acid  (at  80°),  &c. 

USES,  STATISTICS,  AND  PRICE  OF  STARCH.  Large  quantities  of  starch  are  used 
as  a  dressing  in  the  spinning  and  weaving  of  textile  fibres,  in  calico  printing  as  a  thickening 
material,  in  the  manufacture  of  paper,  in  the  preparation  of  adhesive  paste,  in  the  laundry 
and  kitchen,  as  well  as  for  making  dextrin  and  glucose. 

The  import  duty  of  starch  in  Italy  is  Is.  Id.  per  quintal  for  potato  starch,  &c.,  9s.  Qd. 
for  rice  starch,  and  Qs.  5d.  for  maize  and  wheat  starch,  &c.2 

Germany  grows  the  most  potatoes  and  produces  and  exports  (along  with  Holland)  the 
largest  quantities  of  starch.  In  1903  28,764,000  tons  of  potatoes  were  produced,  in  1904 
24,656,000,  in  1905  more  than  34,000,000,  in  1906  about  42,000,000,  and  in  1908  as  much 
as  46,000,000  tons,  the  average  of  the  three  years  1908-1910  being  45,500,000  tons, 
about  12,000,000  tons  being  utilised  for  the  manufacture  of  starch.  The  annual  output  of 
dry  potato  starch  is  about  800,000  quintals  and  that  of  green  starch  560,000  quintals, 
besides  121,000  quintals  of  wheat  starch,3  85,000  of  maize  starch,  and  250,000  of  rice  starch 

1  The  accounts  of  a  factory  dealing  with  25  quintals  of  broken  rice  per  day  are  approximately  as  follows  : 

Capital :  Land  and  buildings,  £3200  ;  machinery,  including  duty,  erecting,  transport,  &c.,  £2400  ;  circulating 
capital,  £2400  ;  total,  £8000. 

Balance  Sheet.  Outgoings:  7500  quintals  of  rice  at  16s.,  £6000  ;  various  chemicals,  £320  ;  repairs,  lubricants, 
lighting,  £200  ;  packing,  £600  ;  salaries  and  wages  (1  manager,  1  foreman,  1  stoker-mechanic,  7  male  and  8  female 
hands,  1  carman  and  horse),  £880  ;  coal  for  motive-power  and  heating,  5000  quintals  at  2s.  8{d.,  £680  ;  traveller 
and  similar  expenses,  £400  ;  accounting,  advertisements,  and  sundry  expenses,  £240  ;  workmen's  and  fire  insur- 
ance and  various  taxes,  £320  ;  unforeseen  expenses,  £200  ;  depreciation  of  factory  (3  per  cent.),  £96,  and  of  plant 
(10  per  cent.),  £240  ;  bad  debts,  discount,  damage  during  transit,  accidents,  £400  ;  5  per  cent,  interest  on  capital, 
£400  ;  outstanding  interest,  rebates,  &c.,  £80  ;  total  outgoings,  £11,076. 

Incomings :  Starch  (75  per  cent,  yield),  5600  quintals  at  41s.  6rf.  (average  market  price  in  bags  and  cases), 
£11,640  ;  residues,  1000  quintals  at  9s.  6rf.,  £480  ;  total  incomings.  £12,120. 

The  net  profit  is  hence  £1040,  which  would  yield  a  dividend  of  18  per  cent,  on  the  capital  outlay.  The  above 
figures  may,  however,  vary  somewhat.  Thus  the  price  of  the  broken  rice  is  sometimes  as  much  as  14s.  6d.  and, 
in  some  years,  even  20s.  per  quintal,  while  that  of  the  starch  may  fall  as  low  as  33s.  6<f. 

1  Analysis  of  Starch.  Different  starches  are  distinguished  by  their  microscopical  appearance  (see  p.  491). 
The  moisture  is  determined  by  heating  10  grms.  in  a  weighed  dish  for  1  hour  at  40°  to  50°  and  for  4  hours  at  120°  ; 
a  good  sample  should  contain  less  than  20  per  cent.  The  acidity  is  determined  on  25  grms.,  which  is  mixed  with 
30  c.c.  of  water  and  titrated  with  decinormal  NaOH  solution,  being  kept  shaken  meanwhile  ;  a  drop  of  the  liqiud 
is  removed  and  placed  on  litmus  paper  from  time  to  time.  If  100  grms.  of  the  starch  require  5  c.c.  of  the  alkali, 
it  is  termed  feebly  acid  ;  if  8  c.c.  are  required,  it  is  described  as  acid,  and  if  more  still,  as  very  acid. 

The  adhesive  power  of  starch  is  determined  by  heating  a  mixture  ot  4  grms.  with  50  c.c.  of  water  over  a  naked 
Bunsen  flame  and  boiling  for  a  minute  until  it  becomes  transparent  and  begins  to  form  froth,  the  flame  being 
then  removed ;  if,  after  shaking  and  allowing  to  cool,  the  paste  is  thick  and  cannot  be  poured  out,  the  adhesive 
properties  are  satisfactory.  The  ash  of  pure  starches  should  not  exceed  0-5  per  cent.,  and  in  the  best  qualities 
is  less  than  0-2  per  cent. 

3  In  1909  Germany  possessed  17  factories,  which  treated  altogether  511,497  quintals  .of  tvheaten  flour  (con- 
taining 12  to  14  per  cent,  of  moisture),  the  products  being  289,236  quintals  of  starch  meal  (£2  per  quintal),  61,777 
quintals  of  dry  starch  residues  (25s.  6rf.  per  quintal),  23,676  quintals  of  wet  residues  (40,  per  quintal),  and  54,069 


DEXTRIN  501 

(1909),  54,000  quintals  of  the  last  being  exported.  Germany  contains  500  starch  factories, 
450  of  which  are  connected  with  agricultural  concerns,  while  the  remaining  50  are  large 
industrial  undertakings.  The  exportation  of  starch  from  Germany  has  diminished  during 
recent  years,  while  it  varies  also  with  the  potato  crop.  In  1890  it  amounted  to  514,000 
quintals,  in  1896  to  340,000,  in  1897  to  141,500,  in  1898  to  173,300,  in  1899  to  339,200,  in 
1901  to  255,500,  in  1902  to  460,000,  in  1903  to  280,000,  in  1904  to  175,000,  in  1905  to 
133,000  (94,000  to  England,  13,000  to  the  United  States,  and  nearly  10,000  to  Italy),  in 

1906  to  229,000  (147,000  to  England,  24,000  to  Spain,  18,000  to  the  United  States),  in 

1907  to  215,622,  in  1908  to  66,000,  and  in  1909  to  129,000  quintals. 

The  price  in  Germany  in  1906  varied  from  8s.  ICd.  to  9*.  Id.  for  green  starch  (50  per 
Cent,  of  water)  and  from  17s.  8d.  to  19s.  2d.  per  quintal  for  dry  starch  of  the  first 
quality. 

The  exportation  of  rice  starch  from  Germany  is  ako  decreasing :  90,000  quintals  in 
1898,  65,000  in  1902,  61,500  in  1906,  and  nearly  60,000  in  1907. 

Trance  produces  about  600,000  quintals  of  potato  starch  per  annum.  In  1904  Holland 
exported  550,000  sacks  of  potato  starch.  England  imported  700,000  quintals  of  starch 
(and  dextrin)  in  1909.  In  the  United  States  185,000  hectols.  of  maize  per  annum  are 
treated  for  the  manufacture  of  starch. 

In  1910  Italy  imported  the  following  quantities  of  different  starches  :  potato  starch 
(25s.  per  quintal),  158,460  quintals  ;  sago,  arrowroot,  &c.  (48s.),  80,000  ;  ordinary  wheat 
starch  (36s.),  27,250  ;  and  fine  wheat  starch  in  cases  (56s.),  11,226  quintals.  In  1909  Italy 
produced  1,722,000  tons  of  potatoes,  and  in  1910  about  1,540,000,  only  a  small  proportion 
of  which  was  worked  industrially. 

DEXTRIN  is  found  ready  formed  in  various  vegetable  juices,  but  is  always 
mixed  with  starch  and  sugar,  while  that  prepared  artificially  from  starch  by 
the  action  of  heat,  acid,  or  diastase  consists  of  a  mixture  of  products  inter- 
mediate to  starch  and  sugar  (maltose  and  glucose).  Several  dextrins  of  various 
molecular  magnitudes  are  known  (achroodextrin,  amylodextrin,  erythrodex- 
trin,  &c.),  the  best  known  form  having  the  formula  C36H62031  or  (C12H2001)30, 
H2O. 

According  to  some  it  has  a  marked  aldehydic  character,  and  hence  gives 
all  the  reactions  of  the  monoses,  including  those  with  phenylhydrazine  and 
Fehling's  reagent,  while  others  hold  that  the  aldehydic  character  is  feeble,  and 
others,  again,  that  Fehling's  solution  is  not  reduced,  even  on  boiling.  This 
diversity  of  view  is  explained  by  the  great  difficulty  of  separating  chemical 
individuals  from  the  mixtures  containing  them  ;  in  any  case  all  the  dextrins 
prepared  commercially  reduce  Fehling's  solution  to  a  greater  or  less  extent. 
Dextrin  is  not  fermented  directly,  and  diastase  does  not  transform  it  entirely 
into  fermentable  sugar  (maltose),  15  per  cent,  remaining  unchanged,  although 
this  slowly  becomes  fermentable  under  the  prolonged  action  of  diastase  (see 
p.  116). 

Dextrin  is  known  also  by  various  commercial  names  (vegetable  gum,  starch 
gum,  artificial  gum,  gommeline,  British  gum,  &c.),  and  forms  a  light  powder 
having  a  slight  smell  of  new  bread  ;  it  is  white,  yellowish,  or  even  brownish, 
according  to  the  purity,  the  method  of  preparation,  and  the  purpose  for  which 
it  is  intended.  It  is  sometimes  sold  in  semi-transparent,  yellowish  lumps.  It 
dissolves  completely  in  water  when  pure  and  has  a  high  rotatory  power 
([a]D  =  about  194°) ;  it  is  insoluble  in  alcohol.  With  iodine  solution  it  gives  a 
reddish  coloration,  and  boiling  dilute  hydrochloric  or  sulphuric  acid  converts 
it  into  glucose,  while  malt  transforms  it  into  maltose  ;  with  concentrated  nitric 
acid  it  gives  oxalic  acid.  Commercial  dextrins  often  contain  a  little  starch 

O 

and  glucose,  so  that  they  then  give  a  violet  coloration  with  iodine  and  reduce 
Fehling's  solution  in  the  hot  ;  the  specific  rotation  varies  from  125°  to  225°. 

quintals  of  gluten  (72s.  per  quintal),  besides  a  certain  amount  of  liquid  waste  for  cattle-food  ;  the  total  yield  of 
starch  was  calculated  at  71-6  per  cent.  Germany  exported  54,740  quintals  of  rice  starch  in  1908  and  63,497  in 
1909. 


502 


ORGANIC    CHEMISTRY 


Manufacture.  According  to  the  ordinary  Heuse  process,  1000  kilos  of  starch  are  mois- 
tened with  2  kilos  of  nitric  acid  of  40°  Be.  diluted  with  300  litres  of  water,  the  paste  being 
made  into  loaves  which  are  dried  in  the  air,  ground  finely,  and  heated  for  about  2  hours  at 
100°  to  120°.  For  this  purpose  the  starch  is  either  spread  in  thin  layers  on  a  number  of  trays, 
which  are  arranged  in  a  suitable  oven,  or  placed  in  a  circular  Uhland  apparatus  (Fig.  381 ), 
the  base  of  which  is  heated  with  superheated  steam  while  the  mass  is  mixed  continually 
by  means  of  a  stirrer  fitted  with  a  number  of  pegs.  If  the  temperature  is  raised  to  130°  to 
140°,  the  duration  of  heating  is  shortened,  but  yellow  and  not  white  dextrin  is  obtained. 
Dextrinification  is  complete  when  the  product  is  entirely  soluble  in  water  and  gives 
no  longer  a  blue,  but  only  a  reddish  brown  colour  with  iodine  solution. 

The  preparation  of  dextrin  by  torrefying  starch  is,  however,  a  very  simple  process, 
which  can  also  be  carried  out  in  the  Uhland  apparatus,  the  starch  being  stirred  and  heated 
at  225°  to  250°  by  means  of  superheated  steam  until  it  assumes  a  brownish  yellow  colour 
and  gives  the  reactions  just  mentioned.  The  steam-pipes  are  utilised  for  the  circulation  of 
cold  water  immediately  dextrinification  is  complete. 

To  distinguish  commercial  dextrins  from  gum  arabic,  the  aqueous  solution  is  treated 

with  either  oxalic  acid  or  ferric 
chloride  in  the  cold  or  concentrated 
nitric  acid  in  the  hot :  dextrin  is 
not  altered  in  this  way  but  the  gum 
becomes  turbid  or  gelatinises.  Fur- 
ther, dextrins  are  strongly  dextro- 
rotatory, while  gums  arc  almost 
always  laevo-rotatory. 

Germany  produces  about  190,COO 
quintals  of  different  dextrins  per 
annum,  the  exports  being  as  follows  : 
111,525  quintals  in  1901,  140,478  in 
1902,  140,722  in  1903,  121,275  in 
1904,  93,781  in  1905,  88,000  in  19C6, 
93,000  in  1907,  39,000  in  1908,  61,000 
in  1909.  The  price  in  Germany  varies 
between  24s.  and  32s.  per  quintal. 
In  Italy,  where  this  industry  has 
FIG.  381.  developed  during  recent  years,  the 

import  duty  is  6s.  5d.  per  quintal. 

England  exported  3112  tons  of  British  gum  in  1909  and  2321  tons  (£67,998)  in  1910. 
GUMS.  These  are  also  polyoses  (C6H10O5)V,  which  are  frequently  formed  in  plants  and 
are  soluble  in  water  or  swell  up,  giving  viscous,  sticky  liquids  ;  they  are  insoluble  in  alcohol 
and  other  solvents  of  the  resins.  Gum  Arabic  is  excreted,  from  December  to  May,  as  an 
adhesive  juice  from  the  bark  or,  better,  from  the  roots  of  certain  African  acacias,  3  to  5 
metres  in  height  ;  after  drying,  it  has  the  sp.  gr.  1  -487,  and  the  various  components  yield 
d-glucose  and  arabinose  on  hydrolysis.  In  Egypt  these  acacias  occupy  entire  forests, 
especially  in  the  provinces  of  Kordofan  and  Gedda  (White  Nile).  The  natives  make  a 
number  of  incisions  in  the  roots,  and  the  liquid  which  issues  condenses  in  the  air  into 
nutlike  masses,  these  being  detached  before  the  commencement  of  the  rainy  season.  The 
grains  have  the  colour  of  amber  and  become  white  when  exposed  to  the  air,  ro  that  there 
are  two  qualities  of  the  gum.  It  is  used  in  large  quantities  by  pastrycooks  and  in  textile 
dyeing  and  printing,  and  generally  as  an  adhesive. 

A  similar  type  of  gum,  obtained  in  abundance  from  Senegal,  issues  from  certain  wounds 
of  cherry-  and  peach-trees,  while  Gum  Tragacanth  is  extracted  from  certain  varieties  of 
Astragalus  in  Servia,  Syria,  Persia,  &c.,  and,  after  being  rendered  mucilaginous  by  pro- 
longed contact  with  water,  is  used  as  a  thickening  material  in  calico  printing,  &c.  The 
exports  of  gum  tragacanth  from  Persia  were  27,561  quintals  in  1903,  30,413  in  1904, 
38,937  in  1906,  and  23,740  in  1908  ;  on  the  Italian  market  the  price  varies  from  £10  to 
£12  per  quintal. 

Germany  imported  58,000  and  exported  23,000  quintals  of  gum  arabic,  gum  tragacanth, 
and  Senegal  gum  in  1905.  Italy  imported  10,300  quintals  in  1901  and  24,070  (worth 
£139,000)  in  1910,  in  which  year  the  exports  were  2345  quintals. 


CELLULOSE  503 

England  imported  8300  tons  of  kauri  gum  in  1909,  and  7800  tons  (£637,600)  in  1910, 
besides  10,737  tons  (£176,066)  of  gum  arabic. 

The  value  of  a  gum  is  ascertained  by  determining  the  viscosity  of  its  solution  (see 
p.  79). 

The  price  of  gum  arabic  varies  from  £2  to  £6  per  quintal. 

GLYCOGEN  or  Animal  Starch  is  also  a  polyose  (C6H1005)n,  found  principally  in  the 
blood  and  liver  of  mammals.  It  is  a  white  amorphous  powder  insoluble  in  cold  water,  and 
is  coloured  reddish  violet  by  iodine  solution.  It  is  converted  into  maltose  by  an  enzyme, 
whilst  on  the  death  of  the  animal  containing  it  or  on  boiling  with  dilute  acids  it  is  trans- 
formed into  d-glucose. 

CELLULOSE,  (C6H10O5)n 

The  actual  molecular  magnitude  of  cellulose  has  not  yet  been  established 
but  is  certainly  very  great.1  Like  starch,  it  may  be  regarded  as  a  multiple  of 
C6H1005,  but,  while  starch  is  able  to  undergo  transformations  (into  dextrin, 
maltose,  &c.)  in  the  vegetable  organism,  cellulose  represents  a  stable  complex. 
Together  with  lignin,  cellulose  forms  the  principal  component  of  the  cell-walls 
of  plants.  It  occurs,  for  instance,  in  wood  and  cotton,  in  different  degrees  of 
purity,  while  in  different  vegetable  organisms  the  cells  assume  distinct  and 
characteristic  forms,  readily  recognisable  under  the  microscope  (see  Part  III, 
Textile  Fibres).  Cotton-wool  and  Swedish  filter-paper  consist  of  cellulose  in  an 
almost  chemically  pure  state.2 

Pure  cellulose  forms  a  white  amorphous  mass,  and  can  be  obtained  by 
treating  cotton  (flocks)  successively  with  hot  dilute  caustic  potash,  hot  dilute 
hydrochloric  acid,  alcohol  and  ether,  and  drying  at  125°  to  eliminate  the  water 
with  which  a  small  part  of  the  cellulose  is  hydrolysed. 

Cellulose  does  not  dissolve  in  ordinary  solvents,  but  is  completely  soluble 
in  concentrated  zinc  chloride  solution,  concentrated  sulphuric  acid,  hydro- 
fluoric acid,  phosphoric  acid,  xanthic  acid  (C2H5OCS-SH)  or,  best  of  all, 
in  an  ammoniacal  solution  of  copper  oxide  (Schweitzer's  reagent,  prepared  by 
dissolving  freshly  precipitated,  well-washed  copper  hydroxide  in  concentrated 
ammonia  solution  in  the  proportion  of  CuO  to  4NH3  +  4H20)  ;  from  this 
solution  it  is  reprecipitated  as  gelatinous  hydrocellulose  by  acids,  alkali  salts, 
or  sugar  solutions.  Hydrocellulose  dissolves  in  a  mixture  of  caustic  soda  and 
carbon  disulphide,  and  is  reprecipitated  in  a  gelatinous  state  by  salts,  &c. 
These  jellies  are  used  for  the  manufacture  of  artificial  silk. 

Dubosc  (1906)  found  that  solutions  of  thiocyanates  constitute  good  solvents 
for  cellulose  ;  ammonium  thiocyanate,  for  example,  gives  viscous  solutions 
from  which  water  separates  gelatinous  cellulose.  In  dissolving  in  any  solvent, 
however,  cellulose  generally  dissociates  into  simpler  molecular  complexes,  which 
cannot  be  converted  into  the  original  cellulose  but  give  hydro-  oroxy-cellulose. 

In  order  to  determine  at  least  minimum  values  for  the  molecular  magnitudes  of  the  polyoses,  Skraup  (1905) 
applied  to  these  compounds  a  reaction  given  by  the  bioses ;  when  the  latter  are  treated  with  acetic  anhydride 
and  dry  hydrogen  chloride  gas,  they  give  chloracetyl-derivatives  without  undergoing  hydrolysis,  and  the  chlorine- 
contents  of  these  derivatives  indicate  the  molecular  weights.  In  this  manner  the  molecular  weight  of  cellulose 
is  found  to  be  at  least  5508,  that  of  soluble  starch  7440,  and  that  of  glycogen  16,350. 

2  From  the  crude  cellulose  or  woody  parts  of  plants,  J.  Konig  (1906)  separated  four  components  giving  the 
following  reactions  :  (1)  hemicellulose,  which  is  hydrolysed  by  dilute  mineral  acids  ;  (2)  cutin  or  suberin,  which 
is  soluble  in  alkali  but  insoluble  in  ammoniacal  copper  oxide  solution  ;  (3)  lignin,  which  is  oxidisable  by  weak 
oxidising  agents ;  (4)  true  cellulose,  insoluble  in  dilute  acid  or  alkali,  soluble  in  ammoniacal  copper  oxide,  not 
oxidisable  by  hydrogen  peroxide. 

The  part  of  the  cellulose  which  enters  into  the  formation  of  the  cell,  but  gives  glucose  on  hydrolysis,  constitutes 
the  hemicellulose  group ;  the  hemicelluloses  of  lupins,  certain  lichens,  &c.,  give  gaiactose,  xylose,  mannose,  &c.,  on 
hydrolysis. 

Cross  and  Bevan  divide  celluloses  into  four  groups  :  (1)  celluloses  which  are  hydrolysed  with  difficulty  and 
contain  no  active  carbonyl  groups  (aldehydic  or  ketonic),  the  characteristic  type  of  this  group  being  the  cellulose 
of  cotton  ;  (2)  celluloses  which  contain  active  carbonyl  and,  sometimes,  methoxyl  groups,  and  give  furfural  when 
hydrolysed  with  hydrochloric  acid  ;  such  are  the  celluloses  of  wood  and  straw  ;  (3)  celluloses  (or  hemicelluloses) 
which  are  easily  hydrolysed  ;  (4)  complex  celluloses. 

The  furfural  and  methylfurfural  formed  by  the  celluloses  of  group  (2)  may  be  derived  from  the  pentoses  yielded 
by  the  pentosans  of  the  celluloses  or  from  the  furfuroids  which  occur  in  abundance  in  vegetable  organisms,  and 
although  they  contain  no  pentosans  yet  give  furfural  (see  pp.  429  and  430). 


504 

The  prolonged  action  at  moderate  temperatures  of  acids,  alkalis,  and 
enzymes  results  in  the  gradual  hydrolysis  of  cellulose,  so  that,  while  before 
hydrolysis  only  a  brown  colour  is  obtained  with  iodine  solution,  after  the 
action  of  concentrated  sulphuric  acid  a  blue  reaction  is  given  ;  in  this  reaction 
the  cellulose  swells  and  dissolves  into  a  kind  of  paste,  and  the  action  on  this  of 
water  separates  substances  similar  to  starch  (amyloids).  If  the  hydrolysis  is 
carried  further  the  reactions  of  the  dextrins  may  be  obtained,  dilution  with 
water  and  boiling  then  resulting  in  the  formation  of  monoses  (hexoses  and 
pentoses).1  Cellulose  may  hence  be  regarded  as  composed  of  complex  anhy- 
drides of  hexoses  and  pentoses,  and  recent  investigations  indicate  that  the 
behaviour  of  cellulose  is  best  explained  by  regarding  it  as  a  colloid  containing 
groups  with  acidic  hydrogen  ions,  others  with  basic  hydroxyl  ions  and  some 
non-dissociated  groups  ;  the  reactions  of  cellulose  with  both  basic  and  acidic 
substances  are  explainable  in  this  way. 

Cellulose  has  alcoholic  characters,  the  hydrogen  of  each  of  the  hydroxyl 
groups  being  replaceable  by  an  acetyl-  (see  p.  189)  or  nitro-group,  &c.  Not 
more  than  three  or  four  hydroxyl-  groups  correspond  with  each  six  carbon 
atoms  ;  with  nitric  acid  three  nitrate  groups  can  be  introduced,  while  with 
acetic  anhydride,  in  presence  of  sulphuric  acid,  esters  (cellulose  acetates) 
corresponding  with  four  hydroxyl  groups  per  C6  are  obtainable  (Cross  and 
Bevaii,  1905). 

According  to  H.  Oat  (1906)  the  ordinary  methods  of  acetylation  always  yield  triacetates 
of  cellulose,  but  hydrocellulose  is  first  formed  as  an  intermediate  product  (C6H10O5)6,  H2O, 
and  it  is  this  which  forms  the  plastic  triacetate,  [C6H7O6(COCH3)3]n,  H20,  used  as  arti- 
ficial silk,  &c.2  If  the  action  of  sulphuric  acid  and  acetic  anhydride  is  carried  too  far,  friable 
acetates  of  no  industrial  value  are  obtained,  the  ultimate  product  being  a  crystalline 
octoacetate  of  a  biose,  cellose  or  cellobiose  (C6H10O5)2,  H20,  which  can  be  liberated  from 
the  acetate  by  hydrolysing  with  alcoholic  potash  but  is  of  no  value  industrially.  The 
rotatory  power  of  cellobiose  is  33-7°,  the  solubility  of  its  phenylosazone  in  boiling 
water  1  :  135,  and  the  melting-point  of  its  phenylosazone  198°  ;  it  is  thus  quite  different 
from  maltose  (rotatory  power,  142-5°  ;  melting-point  of  phenylosazone,  206°  ;  solubility 
of  phenylosazone  in  boiling  water>  1  :  75).  The  origin  of  cellulose  in  plants  cannot  be 
regarded  as  a  condensation  of  starch  ;  the  latter  is  probably  converted  into  glucose,  which 
gives  cellulose  on  condensation.  The  preparation  of  nitrocellulose  (pyroxyline,  guncotton, 
collodion-cotton)  has  already  been  described  in  the  chapter  on  Explosives  (p.  232). 

Cellulose  Formate  (Blumer,  Ger.  Pat.  179,590)  has  also  been  prepared. 

At  210°  cotton  begins  to  decompose  with  evolution  of  carbon  monoxide  and  dioxide, 

1  Numerous  attempts  have  been  made  to  convert  wood  industrially  into  saccharine  substances  and  so  prepare 
alcohol  (see  p.  142),  but  it  is  only  recently  (1910  and  1911)  that  Flechsig,  Ost,  and  Wilkening  showed  that  cellulose 
can  be  transformed  completely  into  fermentable  glucose  by  dissolving  it  in  concentrated  sulphuric  acid,  diluting 
until  the  solution  contains  only  1  to  2  per  cent,  of  acid,  and  then  heating  at  110°  to  120°  (but  not  to  125°,  as 
was  done  by  Simonsen,  since  a  part  of  the  glucose  is  thereby  destroyed). 

2  Cellulose  Acetate    forms    a    horny,  amorphous  mass  soluble  in  chloroform,  tetrachloroethane,  aniline, 
pure  acetic  acid,  and  boiling  nitrobenzene.     The  less  highly  acetylated  products  are  soluble  in  alcohol,  giving 
a  solution  which,  together  with  camphor,  serves  for  the  preparation  of  cellite  films  for  cinematographs  ;   these 
films  are  considerably  less  inflammable  than  those  of  celluloid.     The  triacetyl-compound  is  used  for  making 
artificial  silk  (see  later),  and  is  prepared  by  treating  hydrocellulose  in  the  cold  with  acetic  anhydride,  a  few  drops 
of  concentrated  sulphuric  acid,  and  a  little  glacial  acetic  acid  or  phenolsulphonic  acid  (see  also  the  following  patents  : 
Gcr.  Pats.  118,358,  153,350,  159,524,  163,316,  175,379,  185,837,  203,178,  203,642,  206,950,  224,330  ;    Fr.  Pats. 
316,500,  319,848,  324,862,  345,764,  368,738,  368,766,  371,357,  371,447,  385,179,  385,180;    U.S.  Pats.  733,729, 
826,229,  838,350 ;   Eng.  Pat.  9998,  1905). 

More  or  less  successful  attempts  have  also  been  made  to  acetylate  cellulose  in  the  hot  with  acetyl  chloride 
and  metallic  acetates,  the  reaction  being  facilitated  by  the  addition  of  a  small  quantity  of  pyridine  or  quinoline 
and,  in  some  cases,  of  a  solvent  of  cellulose  acetate  (e.g.  acetone,  nitrobenzene,  naphthalene,  A-c.) ;  see  Ger.  Pats. 
85,329,  86,368,  105,347,  139,669,  and  U.S.  Pat.  709,922,  according  to  which  phenol-  or  naphthol-sulphonic  acids 
are  added.  ^ 

The  following  method  of  manufacture  (from  Fr.  Pat.  347,906)  admits  of  the  direct  acetylation  of  cotton 
textiles  and  may  be  taken  as  an  example  :  10  kilos  of  defatted  cotton,  containing  10  to  20  per  cent,  of  moisture, 
are  heated  with  40  kilos  of  acetic  anhydride  (containing  0-25  per  cent,  of  concentrated  sulphuric  acid)  and  150  kilos 
of  benzene,  at  70°  to  75°,  in  a  reflux  apparatus  until  a  small  portion  of  the  cotton  dissolves  completely  in  chloro- 
form ;  the  whole  mass  is  then  pressed  and  dried. 

Cross,  Bevan,  and  Briggs  (1907)  obtain  cellulose  acetates  easily  and  cheaply,  without  preparing  hydrocellulose  ; 
cellulose  is  treated  directly  with  a  mixture  of  100  parts  of  glacial  acetic  acid,  30  of  zinc  chloride,  and  100  of  acetic 
anhydride,  the  whole  being  heated  for  36  hours  at  45°. 


HYDROCELLULOSE,    MALTOL,    ETC.       505 

methyl  alcohol,  acetic  acid,  acetone,  hydrocarbons,  &c.  (see  Distillation  of  Wood,  p.  272). 
By  the  dry  distillation  of  pure  cellulose  (Swedish  filter-paper)  under  ordinary  pressure, 
E.  Erdmann  and  C.  Schaefer  (1910)  obtained  about  5  per  cent,  of  tar,  42  per  cent,  of  acid 
liquors,  and  a  residue  of  carbon,  together  with  gas  containing  66  per  cent.  CO,  19  per  cent. 
CH4,  11-5  per  cent.  H2,  &c.  ;  from  the  acid  liquors,  acetone,  formaldehyde,  furfural, 
methoxyfurfural,  maltol  (C6H603,  which,  according  to  Peratoner  and  Tamburello,  has 

CH-  0-  OCH3, 
the  constitution  ||  ),  and  y-valerolactone  were  separated.      With  lapse  of 

CH-CO-OOH  f 

time  or  under  the  action  of  bacteria,  &c.,  cellulose  undergoes  various  changes  (see  Peat, 
Lignite,  Coal,  vol.  i  ;  and  Methane,  p.  32  of  this  volume). 

The  action  of  sulphuric  acid  on  cellulose  varies  somewhat  with  the  concentration  of 
the  acid,  the  duration  of  the  reaction,  and  the  temperature.  The  concentrated  acid  has 
a  gelatinising  action  and  dissolves  part  of  the  cellulose,  which  is  reprecipitable  by  water 
or  ammonia.  If  the  action  is  protracted,  the  very  friable  Hydrocellulose,  C12H22Oii 
[(C6H1005)2,  H2O],  is  formed,  but,  in  general,  hydrocelluloses  of  diminishing  molecular 
weight  and  increasing  friability  (e.g.  cellobiose  ;  see  above)  are  successively  formed.  The 
hydrocellulose  formed  in  the  preparation  of  artificial  silk  is  only  slightly  friable,  and  has 
probably  the  formula  (C6H1005)6,  H20.  Since  also  these  hydrocelluloses  exhibit  rather 
different  behaviour  towards  dyes,  it  has  been  suggested  that  the  name  hydrocellulose  be 
given  to  that  resulting  from  advanced  hydrolysis  by  non-oxidising  acids  ;  the  increase 
of  weight  during  this  change,  owing  to  the  addition  of  hydrolytic  water,  is  3-5  to  5  per  cent., 
this  being  lost  at  above  125°,  whilst  the  hygroscopic  moisture  is  expelled  at  104°.  This 
hydrocellulose  reduces  Fehling's  solution  (Ost ;  Cross  and  Bevan,  1909).  On  the  other 
hand  the  name  cellulose  hydrate  or  hydracellulose  is  given  to  that  obtained  by  gentle  alka- 
line hydrolysis,  which  produces  an  augmentation  in  weight  of  8  to  10  per  cent.  ;  here,  too, 
this  hydrolytic  water  is  given  up  at  temperatures  above  125°.  Hydracelluloee  does  not 
reduce  Fehling's  solution.  Schwalbe  (1907)  measured  the  reducing  power  of  hydrocellulose 
towards  Fehling's  solution.1 

Cross  and  Bevan  proposed  for  cellulose  the  formula  : 

H         OH         H         OH 


o:c\ 

XC C'          XH 


H          Oil          H         OH 

some  polymeride  of  this,  such  as 

H         OH        H         OH  H         OH        H        OH 


H  OH 

c—         —a  c  ----  c,         H 


C  —  —  (T  C 


'  &c 


H         OH         H         OH  H         OH        H         OH 

On  the  basis  of  the  formation  of  the  trinitrate  and  triacetate,  Green  (1894)  suggested  for  cellulose  a  formula 

CH(OH)—  CH—  —  CH(OHK 
(or  some  multiple  of  it)  containing  3  OH,  namely  :     |  ^>^  /®'  an<*  *or  hydrocellulose  the 

CH(OH)—  CH  -  CH2  -  / 
CH(OH)—  CH  -  CH(OH)2 
formula    |  ^>O  ;  these  constitutions  explain  the  formation  of  furfural  by  the  decomposition 

CH(OH)—  CH  -  CH2-  OH 

of  cellulose  and  also  the  formation,  under  the  action  of  oxidising  and  bleaching  agents,  of  oxycellulose  containing 
ketonic  groups  which  react  with  phenylhydrazine,  reduce  Fehling's  solution,  and  admit  of  direct  dyeing  by  basic 
dyes  (e.g.  methylene  blue).  Two  oxycelluloses  are,  however,  distinguished  :  the  one  very  similar  to  hydrocellu- 
lose and  insoluble  in  boiling  dilute  alkali,  and  the  other  possessed  of  considerable  reducing  power  and  soluble  in 
alkali. 

The  hardening  of  cellulose  in  the  formation  of  wood  is  due  to  its  partial  transformation  into  LIGNIN,  which 
is  not  yet  well  defined  chemically  but  certainly  contains  methoxy-groi'ps,  which  explain  the  formation  of  methyl 
alcohol  and  acetic  acid  when  wood  is  distilled.  According  to  Green,  lignin  is  formed  by  dehydration  of  cellulose 

CH:C  -  CH-OH 

and  would  be  a  polymeride  of   |        ^>O  ~^>^>    •    -^u*  Klason  is  of  the  opinion  that  lignin  is  a  kind  of  glucoside 
CH:C  -  CH-OH 


506  ORGANIC    CHEMISTRY 

When  sheets  of  pure,  unsized  paper  are  immersed  for  a  few  minutes  in  sulphuric  acid 
of  50°  to  60°  Be.  and  then  washed  immediately  in  a  plentiful  supply  of  water,  they  are 
converted  into  parchment  paper  (artificial  parchment),  amyloids  being  formed  at  the  surface. 
These  artificial  parchments  are  distinguished  from  the  natural  ones  by  the  presence  of 
nitrogen  in  the  latter,  and  from  paraffined  paper  by  the  extraction  of  the  paraffin  from 
these  by  ether.  Parchment  paper  is  rendered  softer  and  more  transparent  by  immersion 
in  glycerine  or  glucose  solution.  If  cellulose  pulp  is  well  ground  and  beaten  in  the  Hollander 
until  it  forms  an  almost  gelatinous  pulp,  a  translucent  paper  can  be  obtained  which  is 
similar  to  artificial  parchment  and,  under  the  name  of  pergamin,  is  largely  used  as  a  wrap- 
ping for  foods  and  fatty  materials  ;  this  may  easily  be  distinguished  from  vegetable 
parchment,  which  is  composed  of  cellulose  hydrate  (amyloids)  and  is  hence  coloured  blue 
by  a  solution  of  iodine  in  potassium  iodide,  whilst  pergamin  gives  no  such  coloration. 

With  concentrated  zinc  chloride  solution,  cellulose  gives  compounds  similar  to  those 
it  forms  with  sulphuric  acid  :  papers  thus  prepared  and  then  superposed  and  compressed 
form  the  so-called  vulcanised  paper  ;  this  is  very  hard,  impermeable  to  water,  and  a  bad 
conductor  of  electricity,  and  is  used  for  making  plaques,  tubes,  and  noiseless  gearing. 

When  cellulose  is  treated  for  a  long  time  with  energetic  oxidising  agents,  it  is  converted 
into  oxycellulose  (C^gH^O] 6)v,  which  lowers  the  resistance  of  the  tissues  and,  unlike  cellu- 
lose, reduces  Fehling's  solution  and  fixes,  although  feebly,  basic  dyes  and  alizarine  without  a 
mordant.  Hydrocellulose  reduces  Fehling's  solution  slightly  and  is  not  coloured  by  basic 
dyes. 

When  cellulose  (spun  or  woven  cotton)  is  treated  in  the  cold  with  concentrated  caustic 
soda  solution  (25°  to  35°  Be.),  it  swells  and  becomes  semi-transparent  owing  to  the  forma- 
tion of  sodiocellulose,  and  treatment  of  this  with  a  large  amount  of  water  converts  it  into 
hydrocellulose  (see  above),  the  original  appearance  of  the  cellulose  being  retained.  But  in 
the  hot  sodiocellulose  cannot  be  obtained  (see  Part  III,  Textile  Fibres  and  Mercerised 
Cotton),  prolongation  of  the  action  then  resulting  in  decomposition  into  oxalic  acid. 
Hygroscopic  water  held  by  cellulose  is  eliminated  by  heating  at  100°  to  105°  ;  the  water 
of  hydration  in  hydrocellulose  is  determined  by  heating  in  toluene  or  petroleum  or  at 
130°.  The  hydration  occurring  during  mercerisation  increases  the  weight  of  the  cotton 
by  8  to  10  per  cent. 

Mercerised  Cotton  is  distinguished  from  ordinary  cotton  by  Knecht's  test :  the  material 
is  dyed  in  the  hot  with  5  c.c.  of  benzopurpurin  4B  solution  (0-1  grm.  in  100  c.c.  of  water), 
and  when  it  has  taken  the  colour  well,  about  2  c.c.  of  concentrated  hydrochloric  acid  are 
added  drop  by  drop  to  the  bath  ;  the  non -mercerised  cotton  then  turns  bluish  black, 
while  the  mercerised  remains  red.  If  oxycellulose  (which  is  formed  even  by  the  action  of 
calcium  hypochlorite)  is  present,  the  material  is  dyed  with  Congo  red  and  the  acid  then 
added,  the  ordinary  cotton  and  the  oxycellulose  assuming  the  bluish  black  colour,  while 
the  mercerised  cotton  remains  red  ;  but  if  the  material  is  thoroughly  washed,  the  pure 
cotton  becomes  red,  the  oxycellulose  retaining  its  bluish  black  and  the  mercerised  cotton 
its  red  colour. 

PAPER  INDUSTRY 

As  prime  material  in  the  paper  industry,  use  has  been  and  is  still  made  of  all  the  cellu- 
losic  fibres  obtained  from  most  widely  differing  plants,1  linen  and  cotton  rags,  straw, 
wood,  hemp,  &c. 

with  two  aromatic  nuclei  containing  mcthoxy-  and  hydroxy-groups,  also  lateral  groups,  -CH  :  CH  and  CH2-OH, 
besides  the  fundamental  cellulose  grouping  ;  it  is  probably  represented  by  the  formula  (C^H^Oj,));. 

Dry  wood  contains  26  to  30  per  cent,  of  lignin.  Schultze,  Tollens,  and  Konig  hold  the  view  that  the  hard 
part  of  wood  is  formed  of  cellulose,  together  with  small  proportions  of  pentosans  and  of  lignin.  The  formation 
of  wood  in  plants  has  been  recently  attributed  by  Wislicenus  to  the  'colloidal  character  of  the  plant  fluids  which, 
in  the  initial  phase,  transport  into  the  tissues  the  cellulosc-hydrogcl  as  a  superficial,  chemically  indifferent  sub- 
stance ;  in  a  second  phase,  the  latter  is  lignifled  by  absorption  and  surface  gelatinisation  of  the  colloidal  meta- 
bolic substances  contained  in  the  sap.  Lignocellulose  is  hydrolysed  and  dissolved  by  zinc  chloride  solution  and 
by  ammoniacal  copper  oxide  solution,  dilute  acids  and  alkalis  also  exerting  a  hydrolysing  action.  Lignin  gives 
a  number  of  colour  reactions,  e.g.  with  aniline  sulphate  (yellow),  with  phloroglucinol  and  hydrochloric  acid  (red) ; 
with  potassium  ferricyanide  it  forms  potassium  ferrocyanide,  and  with  fhchsine  decolorised  by  sulphur  dioxide 
it  gives  a  red  colour ;  it  fixes  various  aniline  dyes  (e.g.  methylene  blue,  eosin,  &c.)  directly.  Wood  is  regarded 
by  Cross  and  Bevan  as  an  ester  of  lignocellulose,  derived  from  cellulose  (polyhydric  alcohol)  and  lignic  acid  (lignin). 

When  pure  cellulose  is  subjected  to  dry  distillation,  it  does  not  yield  methyl  alcohol,  which  is,  however,  formed 
from  wood  ;  the  alcohol  must  hence  be  derived  from  the  lignin.  But  acetic  acid  is  formed  from  both  lignin  and 
cellulose. 

1  History  of  the  Paper  Industry.  The  origin  of  paper  dates  back  to  the  second  century  B.C.,  when  the 
first  traces  of  it  were  evident  in  China.  In  early  times  races  marked  their  records  and  writings  on  stone,  wood, 


PAPER  507 

It  is  not  possible  here  to  review  all  the  wonderful  mechanical  improvements  which 
rendered  paper-making  one  of  the  most  interesting  and  important  industries  of  the  nine- 
teenth century.  From  the  arrival  of  the  wood  in  the  factory  to  the  despatch  of  the  rolls 
or  reams  of  paper,  all  the  operations  are  carried  out  mechanically  by  means  of  perfected 
machinery,  which  is  not  only  more  rapid  in  its  action  but  more  accurate  than  hand  labour. 

A  description  cannot  be  given  here  of  all  the  varied  and  ingenious  dressings  employed  to 
obtain  different  kinds  of  paper,  or  of  the  mineral  loading  of  kaolin,  barium  sulphate,  gypsum, 
&c.,  with  which  some  papers  are  so  impregnated  that  the  mineral  substances  exceed  the 
vegetable  matter,  to  the  delight  of  the  tradesman  who  sells  gypsum  for  cheese  or  sausages. 

What  will  be  attempted  here  will  be  simply  a  brief  description  of  the  various  treatments 
to  which  the  raw  material  is  subjected  to  convert  it  into  paper. 

Paper  factories  require  a  plentiful  supply  of  pure  water,  which  must  not  contain  iron 
and  should  be  filtered  if  turbid. 

.The  rags,  gathered  in  places  of  all  sorts  and  in  all  conditions,  are  acquired  from  the  rag- 
merchants,  who  separate  those  of  wool  and  silk,  which  go  to  wool  factories,  &c.,  and  often 
sort  the  remaining  linen  and  cotton  rags  into  light  and  dark  sorts. 

It  is  calculated  that  Italy  produces  about  600,000  quintals  of  rags,  only  some  35,000 
of  which  are  made  into  paper,  while  in  1905  20,700  quintals  of  vegetable  rags  (at  9*.  6d. 
per  quintal)  were  imported,  together  with  30,000  quintals  of  animal  rags  (at  48s.)  and 

and  parchment.  In  the  seventh  and  eighth  centuries  the  Japanese  and  other  neighbouring  peoples  learnt  how  to 
prepare  paper  from  the  bark  of  various  trees,  this  industry  then  becoming  known  to  the  Arabs,  but  only  much 
later  in  Europe.  In  1190  paper  made  its  appearance  in  Germany,  in  1250  in  France,  in  1275  in  Italy,  and  in 
1430  in  Switzerland. 

In  the  East,  besides  bark,  cotton  and  linen  rags  were  also  employed  for  paper -making.  In  Italy  the  first 
important  factory  furnished  with  grinders  and  pistons  for  the  preparation  of  the  raw  material  was  erected  at 
Fabriano  in  1320.  With  the  subsequent  discovery  of  printing,  the  paper  industry  underwent  an  unforeseen  and 
marked  development,  and  grew  to  enormous  proportions  in  the  nineteenth  century. 

About  the  middle  of  the  eighteenth  century,  the  pistons  and  grindstones  in  use  up  to  that  time  for  treating  the 
raw  materials  were  gradually  replaced  by  the  so-called  Hollanders,  which  led  to  an  increase  in  the  output  and 
an  improvement  in  the  quality  of  the  product.  The  demand  for  paper  increased  largely  at  the  end  of  the  eighteenth 
century,  the  form  being  improved  and  the  price  lowered. 

Mechanics  and  chemistry  came  to  the  aid  of  the  paper  manufacturer,  and  as  early  as  the  beginning  of  the 
nineteenth  century  the  paste  of  cotton  or  linen  fibres,  mixed  in  large  tanks,  was  transformed  into  a  thin  sheet  of 
paper  by  means  of  a  revolving,  perforated  drum,  through  which  the  water  escaped.  It  was  about  1825  that 
rudimentary  continuous  machines  were  first  employed,  these  supplying  an  uninterrupted  strip  of  paper  a  metre 
in  width  at  a  rate  of  10  metres  per  minute.  The  imposing  and  complex,  but  very  accurate,  continuous  machines 
of  the  present  day  give  paper  as  much  as  4  metres  wide  at  150  metres  per  minute. 

Great  advances  were  also  made  in  the  chemical  treatment  of  the  raw  materials.  In  the  first  quarter  of  the 
nineteenth  century,  the  putrefaction  to  which  the  rags  were  subjected  so  that  they  might  be  more  easily  disintegrated 
was  replaced  by  heating  with  soda  and  lime  in  open  boilers  and,  later  on,  in  closed  boilers  under  steam  pressure. 
Then  came  bleaching  of  the  fibres  with  gaseous  chlorine  and  subsequently  with  chloride  of  lime.  The  yellow 
cellulose  obtained  from  straw  can  also  be  bleached  in  this  way,  and  since  1830  has  been  used  in  large  quantities 
for  the  commoner  papers  and  for  mixing  with  rags.  Sizing  of  paper  by  means  of  resin  soap,  although  suggested 
in  1800,  only  later  came  into  general  use. 

With  the  rapidly  increasing  consumption  of  paper,  there  came  a  time  of  dearth  of  raw  materials ;  cotton 
and  linen  rags  were  no  longer  obtainable  in  sufficient  quantities,  and  straw  could  not  be  used  alone.  It  hence 
became  necessary  to  look  for  other  sources  of  cellulose,  and  it  is  to  Keller  that  we  owe  the  happy  solution  of  this 
pressing  problem.  In  1843  he  succeeded  in  utilising  wood-cellulose  by  means  of  machines  which,  rotating  rapidly 
against  logs  of  wood  kept  wet,  gradually  converted  the  wood  into  an  aqueous  pulp  made  up  of  the  separate  fibres  ; 
these  machines  were  improved  later  by  Volter,  and  the  first  factories  of  mechanical  wood-pulp  were  erected.  Thig 
inexhaustible  material  can  be  purified  by  boiling  it  with  caustic  soda  in  digesters  under  pressure  and  bleaching 
the  resultant  brown  mass  with  chloride  of  lime ;  this  procedure  gives  chemical  ivood-pulp,  which  to-day  forms 
the  basis  of  almost  all  kinds  of  paper,  from  the  finest  to  the  commonest. 

In  1884  Dahl  effected  considerable  economy  in  the  manufacture  of  wood  pulp  by  replacing  the  expensive 
caustic  soda  to  a  large  extent  by  sodium  sulphate  ;  calcination  of  the  evaporated  residue  of  the  exhausted  lye 
yields  mainly  caustic  soda,  sodium  carbonate,  sulphide,  thiosulphate,  &c.,  and  a  solution  of  this  product  acts 
on  wood,  giving  a  whiter  and  more  resistant  product.  But  although  this  process  was  applicable  with  advantage 
to  straw  cellulose,  which  gives  good  results  only  when  treated  with  alkali  or  sulphate  (the  consumption  of  straw 
is  limited  nowadays  by  its  increasingly  high  price),  it  was  not  convenient  for  dealing  with  the  enormous  quantities 
of  wood  necessary  to  meet  the  growing  demands  for  paper.  As  early  as  1865,  Tilgman  in  America  had  attempted 
the  chemical  purification  of  mechanical  wood-pulp  by  digestion  with  acid  sulphites,  and  in  1874  Ekman's  large 
factory  at  Bergvik  was  working  regularly  with  magnesium  bisulphite.  Meanwhile,  Professor  Mitscherlich  of 
Monaco  (1872)  had  suggested  the  improvement  of  this  process  by  using  calcium  bisulphite  in  large  digesters  under 
pressure.  From  that  time  and  especially  after  the  improvements  introduced  by  Keller,  the  use  of  bisulphite 
spread  gradually  in  Germany  and  other  European  countries  and  received  a  fresh  impetus  on  the  lapse  of  Mit- 
scherlich's  patents.  At  the  present  time,  with  rare  exceptions — these  including  the  treatment  of  straw,  which 
contains  silicates  not  attacked  by  bisulphite — almost  all  wood-pulp  is  transformed  into  cellulose  by  the  bisulphite 
process.  This  process  not  only  effects  economy  in  the  digestion  of  the  wood-pulp,  but  results  in  an  increased 
yield  of  a  whiter  and  more  resistant  product. 

With  improvements  in  the  chemical  methods  and  especially  by  the  use  of  energetic  bleaching  processes  (chlorine, 
chloride  of  lime,  electrolytic  alkali,  hypochlorite,  &c.),  it  became  possible  to  utilise  the  wood  of  many  different 
trees — from  the  fir  to  the  poplar — so  that  there  is  now  no  danger  that  raw  material  for  paper-making  may  some 
day  fail.  In  Canada  alone  there  are  still  forests  large  enough  to  supply  the  whole  world  with  paper  for  800  years, 
even  with  a  much  larger  annual  consumption  than  at  present. 


508 


ORGANIC    CHEMISTRY 


11,200  of  mixed  rags  (at  8s.  lOd.)  ;  in  1910  the  corresponding  amounts  were  15,300,  21,000, 
and  21,400  quintals  respectively.  The  exports  in  1905  were  15,000  (at  28s.)  12,000,  and 
210  quintals  respectively  ;  in  1906  2631  quintals  were  exported,  in  1908  only  508,  and  in 
1910  less  than  200  quintals.  Also  65,000  quintals  of  macerated  paper  (recovered  waste 
paper)  are  utilised  every  year  in  Italy. 


FIG.  382. 


FIG.  383. 


In  1909  17,777  tons  of  linen  and  cotton  rags,  of  the  value  of  £180,000,  were  imported 
into  England. 

The  rags  arrive  at  the  paper  factory  in  large  bundles,  some  light  and  others  dark. 
Preference  is  given  to  linen  rags,  since  these  give  longer  and  tougher  fibres  and  are  used 
also  to  improve  those  of  cotton.  The  first  operation  to  which  the  rags  should  be  subjected 
is  disinfection,  either  by  heat  (great  care  being  then  taken  to  avoid  fires)  or  by  gaseous 
disinfectants  (e.g.  by  introducing  the  bales  into  large  iron  cylinders,  which  are  then  evacuated 
and  filled  with  formaldehyde  vapour).  In  many  factories,  however,  this  disinfection  is 

omitted,  the  health  of  the  sorters 
being  thus  jeopardised.  Sorting 
is  carried  out  by  workpeople  who 
spread  the  loose  rags  on  tables 
and  separate  carefully  those 
which  are  more  or  less  white  and 
those  which  are  coloured  to  vary- 
ing degrees  ;  the  larger  pieces  are 
then  cut  by  special  cutters  (Fig. 
382),  having  a  number  of  hori- 
zontal knives  fixed  to  the  peri- 
phery of  a  cylinder,  the  seams, 
buttons,  hooks,  &c.,  being  pre- 
viously removed.  The  different 
qualities  then  pass  to  suitable 
machines  to  be  cleaned  and 
brushed.  Fig.  383  shows  a 
simple  form  of  duster,  in  which 
the  rags  are  beaten  vigorously  by 
pegs  or  rapidly  revolving  hori- 
zontal wooden  cylinders  and 
carried  to  the  opposite  end  of 
^e  macmne>  while  the  dust  is 
removed  by  an  air-draught  to  be 
deposited  in  chambers  or  in  large  bag-filters  of  various  types  (Fichter,  Beeth,  &c.). 

After  this  the  rags  are  washed  a  little  with  water  in  vessels  similar  to  hollanders  (see 
p.  513)  without  knives  but  with  a  vaned  wheel  and  a  gauze  drum  for  renewing  the  water. 
They  are  next  removed  to  revolving  spherical  boilers,  where  the  residual  dirt  is  eliminated 
and  any  dye,  fat,  resin,  starch,  gum,  or  other  impurity  destroyed.  This  is  effected  by 
boiling,  sometimes  with  soda  or  caustic  soda,  but  more  commonly  with  lime  (2  to  5  per 
cent,  on  the  weight  of  the  rags)  and  water.  These  boilers  (Fig.  384)  hold  as  much  as  2000 


FIG   384 


MECHANICAL    PULP 


509 


kilos  of  rags  and  make  about  two  revolutions  per  minute,  while  steam  is  passed  in  through 
a  tube  traversing  the  axis  until  a  pressure  of  2  to  3  atmos.  is  reached.  The  boilers  are 
coated  with  insulating  material,  and  the  boiling  lasts  for  6  to  12  hours,  according  to  the 
nature  of  the  material.  When  the  boiling  is  finished,  the  steam  under  pressure  is  released 
into  the  adjacent  boiler,  in  which  the  operation  is  just  starting,  and  the  rags  removed, 
rinsed  well  in  water,  and  reduced  to  a  fine  pulp  in  machines  similar  to  hollanders  (see  later) 
with  cast-iron  or  reinforced  concrete  tanks,  the  knives  of  the  drum  not  being  set  too  close 
to  those  of  the  fixed  plate.  About  20  horse-power  is  required  by  the  hollanders  for  a  charge 
of  200  kilos  of  rags.  The  loss  in  weight  in  all  the  operations  up  to  the  present  stage  varies, 
according  to  the  quality  of  the  material,  from  12  per  cent,  to  40  per  cent.  In  hollanders  or 
similar  vessels  holding  up  to  800  kilos  of  rags,  the  bleaching  is  carried  out  with  a  clear  solution 
of  chloride  of  lime,  of  which  2  to  10  kilos  are  required  per  100  kilos  of  rags  ;  a  little  sulphuric 
acid  (100  to  200  grms.  per  10  kilos  of  chloride  of  lime)  is  finally  added  to  liberate  all  the 
chlorine  from  the  bleaching  agent.  In  some  factories  fresh  electrolytic  solutions  of  sodium 
hypochlorite  (see  vol.  i,  p.  457)  are  used.  The  bleaching  must  not  be  too  prolonged,  and 
the  pulp  is  afterwards  washed  in 
large  quantities  of  water  until  all 
smell  of  chlorine  has  disappeared 
and  potassium  iodide  starch  paper 
is  no  longer  turned  blue  or  blue 
litmus  paper  reddened  ;  as  a  pre- 
caution, 30  to  50  grms.  of  sodium 
thiosulphate  (antichlor)  and  soda 
are  added  to  each  vessel.  The 
bleached  mass  or  half-stuff,  as  it  is 
called,  is  freed  from  water  and 
allowed  to  drain  for  some  days  in 
brickwork  chambers  with  pave- 
ments of  absorbent  grooved  bricks. 
From  these  it  is  taken  in  the 
moist  state  as  required  for  mixing 
with  bleached  wood-pulp.  The 
mixture  is  beaten  in  true  hol- 
landers, the  knives  being  set  more 
or  less  close  according  as  more  or 
less  fine  refined  pulp  is  required. 

WOOD-PULP  (Mechanical 
Pulp).  The  treatment  to  which 
the  woody  parts  of  the  various 

plants  suitable  for  paper-making  [fir,  pine,  larch,  poplar  (Populus  nigra  or,  better, 
Populus  canadensis),  beech,  birch,  esparto  (of  which  Algeria  exports  half  a  million  quintals 
annually),  straw,  hemp,  broom,  &c.],  varies  somewhat,  as  the  cellulose  and  the  surrounding 
lignin  are  present  in  different  proportions  and  in  different  states  of  aggregation.1  Logs 
containing  few  knots  are  cut  into  the  required  lengths  (40  cm.),  which,  after  the  knots 
have  been  removed  by  a  boring  machine,  are  barked  in  another  machine.  The  logs  are  then 
defibred  by  being  pressed  against  a  stone  mill,  which  revolves  rapidly  and  removes  the 
fibres  tangentially.  This  mill  is  about  1 J  metre  in  diameter  and  35  to  40  cm.  thick,  and  it 
revolves  either  horizontally  or  vertically  (at  150  to  180  turns  per  minute).  To  the  latter 
type  belongs  the  vertical  grinder  devised  by  Vbith  and  subsequently  improved  in  various 
ways  (Fig.  385).  The  three  chambers  corresponding  with  the  three  toothed  rods,  B,  contain 

1  In  the  disintegrated  wood,  the  proportion  of  cellulose  is  determined  by  digesting  several  times  with  sodium 
bisulphite  solution  and  then  treating  repeatedly  with  chlorine  at  0°,  by  which  means  almost  all  the  constituents 
except  the  cellulose  are  dissolved.  For  the  determination  of  the  crude  cellulose  in  plants,  Weender's  older  method, 
modified  by  Uermeberg  and  Stohmann,  has  been  largely  replaced  by  that  of  Gabriel  (or  Lange  and  Konig) : 
2  grms.  of  the  finely  divided  substance  are  heated  in  a  beaker  with  60  c.c.  of  alkaline  glycerine  (33  grms.  of  caustic 
soda  dissolved  in  a  litre  of  glycerine)  at  180°,  the  mass  being  then  cooled  to  340°  and  poured  into  a  basin  con- 
taining 200  c.c  of  boiling  water,  with  which  it  is  mixed  and  allowed  to  settle.  The  supernatant  liquid  is  drawn 
off  thiough  a  siphon  covered  with  cloth  at  the  end  dipping  into  the  liquid,  and  the  deposit  boiled  with  200  c.c. 
of  water  which  is  siphoned  off  as  before.  The  boiling  is  repeated  with  200  c.c.  of  water  containing  5  c.c.  of  con- 
centrated hydrochloric  ^cid,  and  the  residue  finally  brought  on  to  a  tared  filter,  washed  with  water,  alcohol,  and 
ether  successively,  dried  and  weighed  as  crude  cellulose. 

To  determine  the  pure  cellulose,  almost  free  from  pentosans,  ash,  &c.,  KSnig's  method  is  used  :   3  grms.  of 


FIG.  385. 


510 


ORGANIC    CHEMISTRY 


the  logs  cut  to  the  proper  length,  and,  while  the  grinder  revolves,  these  are  pressed  against 
it  by  the  corresponding  covers  which  are  forced  down  by  the  toothed  rods  ;  the  latter 
connect  with  gearing  worked  by  a  chain,  D,  the  velocity  of  which  is  proportioned  to  that 
of  the  grinder.  The  pressure  is  nowadays  exerted  hydraulically  ;  Fig.  386  shows  a  series  of 
such  vertical  grinders  in  which  hydraulic  pressure  is  employed.  Horizontal  grinders  (Fig. 


FIG.  386. 

387,  vertical  section  ;  Fig.  388,  general  view)  with  hydraulic  pressure  are  now  widely  used, 
as  they  admit  of  a  larger  number  of  logs  being  ground  at  the  same  time.  While  in  opera- 
tion, the  grinder  is  continually  sprayed  with  water  to  prevent  heating  and  to  remove  the 
woody  fibres  as  they  are  liberated. 

According  to  the  pressure  of  the  logs  on  the  grinder  and  to  the  speed  of  the  latter 


FIG.  387. 


FIG.  388. 


a  more  or  less  fine  pulp  is  obtained  with  a  smaller  or  larger  content  of  splinters,  dust,  and 
other  irregular  and  unusable  portions  ;  these  are  removed  by  means  of  sloping  sieves, 

the  finely  divided,  air-dried  material  are  treated  with  200  c.c.  of  glycerine  (sp.  gr.  1-230)  containing  4  grms  of 
concentrated  sulphuric  acid  in  a  dish  which  is  heated  in  an  oven  at  137°  for  exactly  one  hour,  the  liquid  being  then 
allowed  to  cool  to  80°  to  100°,  mixed  with  200  to  250  c.c.  of  hot  water,  boMed  and  filtered  hot  through  an  asbestos 
filter  with  the  help  of  a  pump.  The  filter  is  then  washed  with  300  to  400  c.c.  of  hot  water,  then  with  boiling 
alcohol,  and  finally  with  a  hot  mixture  of  alcohol  and  ether.  The  filter  and  its  contents  are  next  introduced 
into  a  platinum  crucible,  which  is  dried  at  105°  to  110°  and  weighed.  The  crude  cellulose  is  then  ashed  by  heating 
to  redness,  the  loss  in  weight  thus  produced  representing  the  crude  cellulose  free  from  ash.  If,  in  a  second  estima- 
tion, the  cellulose  is  not  dried  and  ashed,  but  is  repeatedly  treated  for  several  hours  with  strong  hydrogen  per- 
oxide and  ammonia,  and  finally  washed,  dried,  weighed,  ashed,  and  again  weighed,  the  proportion  of  pure,  white 
cellulose  is  obtained.  The  difference  between  the  crude  and  the  pure  cellulose  represents  the  lignin. 


CHEMICAL    PULP 


511 


B  and  C  (Fig.  389),  on  to  which  the  channel,  A,  conveys  the  water  to  carry  away  the  crude 
wood-pulp,  while  powerful  water -jets  carry  the  splinters  (b),  the  good  fibre  (c),  and  the 
dust  (E)  to  various  collecting  channels.  Cylindrical  or  superposed  sieves  are  also  used. 

When  the  wood-pulp  is  to  be  used  immediately  for  making  paper,  it  is  mixed  with  the 

necessary  quantities  of  rag-pulp  and  dressing  and  worked  up  as  described  below.     But 

generally  the  wood-pulp  is 
placed  on  the  market,  in  which 
case  the  water  is  removed  and 
the  pulp  converted  into  sheets 
by  sucking  it  on  to  drums 
of  metal  gauze  or  travelling 
planes,  through  which  the 
water  is  drawn  by  suction  ; 
the  continuous  layer  of  pulp 
is  cut  into  lengths  and  is  best 
dispatched  in  the  wet  state 
(with  40  to  60  per  cent,  of 
water).  But  sometimes  the 
FIG.  389.  sheets  are  dried  on  hot  drums, 

although  this  renders  difficult 

the  subsequent  treatment  necessary  to  transform  them  into  pulp  in  the  hollanders. 

Wood-pulp  is  yellowish  or  rather  brown,  and  still  contains  all  the  encrusting  substance 

(lignin)  ;  it  cannot  be  used  as  it  is  for  paper,  the  action  of  light  altering  its  colour  imme- 
diately. It  cannot  be  bleached  with  chloride  of  lime  or  alkaline  reagents,  which  intensify 

its  yellow  colour  ;    but  good  results  are  obtained  with  sulphur  dioxide,  which  does  not, 

indeed,  remove  the  yellow  tint  but  prevents  the 

browning  or  reddening  which  gradually  sets  in. 
Barked  and  cleaned  logs  yield  about  one -half 

their  weight  of  dry  wood-pulp  (containing  12  to  15 

per  cent,  of  moisture). 

CHEMICAL  WOOD-PULP.     This  is  obtained 

by  removing  the  encrusting  matter  from  the  wood 

by  means  of  various  chemical  agents.      It  was 

Payen  who  first,  in  1840,  attempted  this  purifica- 
tion with  nitric  acid,  and  who   afterwards  tried 

caustic  alkalis,  sulphurous  acid,  &c.    The  prepara- 
tion of  the  cellulose  in  the  chemical  way  can  be 

effected  by  (a)  the  soda  process  or  (b)  the  bisulphite 

process. 

(a)  The  logs  freed  from   bark  and  knots  are 

converted   into    sticks    1    cm.   thick,   which    are 

heated  for  some  hours  with  caustic  soda  of  12°  Be. 

under  a  pressure  of  6  to  8  atmos.  (160°  to  170°)  in 

large  digesters,  100  to  200  cu.  metres  in  capacity. 

Various  types  of   digester   are  in  use,   Fig.    390 

showing  the   vertical   type    devised   by  Sinclair. 

This  consists  of  an  iron  cylinder,  A,  5  to  6  metres 

in  height,  with   conical   extremities,   a   charging 

orifice,  C,  a  wide  horizontal  discharge  tube,  Clt  a 

tube,  b,  by  which  the  caustic  soda  is  introduced, 

and  an  inner  perforated  jacket,  which  is  filled  to 

the   extent   of   four-fifths  with   the  sticks.     The 


FIG.  390. 


reservoir,  G,  contains  a  supply  of  caustic  soda  solution,  and  circulation  in  the  digester  can 
be  effected  with  the  help  of  a  Korting  injector,  the  cocks  of  the  tubes,  hlt  and  h,  being 
opened  ;  the  latter  conveys  the  alkali  on  to  the  sticks,  while  that  collected  between  the 
perforated  jacket  and  the  inner  wall  of  the  digester  ascends  through  hv  The  hot  gases  from 
the  hearth,  K,  heat  the  digester  and  pass  through  E  to  the  chimney.  At  the  end  of  the 
operation  the  highly  coloured  alkali  is  discharged  from  the  tap,  V,  and  can  be  used  for 
several  successive  treatments,  being  reinforced  each  time  with  a  little  sodium  carbonate 


512 


ORGANIC    CHEMISTRY 


FIG.  391. 


The  soda  is  eventually  recovered  from  this  liquor  by  evaporating  in  a  vacuum,  calcining 
the  residue,  extracting  the  sodium  carbonate  thus  formed  with  water,  boiling  with  milk 

of  lime,  and  decanting  the  resultant  caustic  soda  solution  (see  vol.  i,  p.  441).    But  for  this 

recovery  of  the  soda,  this  process  would  be  inapplicable.  A  method  which  is  more  econo- 
mical and  more  generally  used  consists  in  reinforcing 
the  alkali  liquor  first  used  with  sodium  sulphate,  instead 
of  the  carbonate,  for  subsequent  operations  ;  the  liquor 
is  then  ultimately  evaporated  in  a  vacuum  and  calcined, 
the  sodium  sulphate,  in  presence  of  carbonised  organic 
matter,  being  converted  partly  into  caustic  soda  and 
partly  into  sodium  sulphide  (which  exerts  on  wood  the 
same  action  as  caustic  soda),  just  as  in  the  preparation 
of  soda  by  the  Leblanc  process  (see  vol.  i,  p.  468). 
Extraction  of  the  calcined  mass  with  water  yields  a  liquor 
containing  sodium  sulphate,  sulphide,  and  carbonate,  and 
is  ready  to  act  on  fresh  quantities  of  wood  in  the  digester. 
Cellulose  thus  prepared  is  termed  sulphate  pulp.  The 
concentration  of  the  alkaline  liquor  is  accompanied  by 
the  production  of  pungent  and  disagreeable  odours,  which 
are  a  source  of  annoyance  to  the  neighbourhood,  so  that 
hi  certain  countries  (e.g.  Scandinavia)  such  concentration 
is  prohibited.  It  has  been  suggested  to  destroy  these 
odours  (due  to  mercaptan)  by  nitrous  vapours. 

Use  is  also  made  of  horizontal  autoclaves  arranged  in 
series  like  sugar  diffusors  (see  p.  451),  while  ordinary 
vertical  iron  digesters,  as  shown  in  Fig.  391,  are  largely 

employed.     The  digesters  can  be  heated  with  indirect  steam  for  24  to  48  hours,  or,  more 

economically  and  rapidly,  by  direct  steam  (10  to  15 

hours)  to  140°  to  150°  (12  to  15  atmos.),  but  the  yield 

is    then    rather  lower  and  the  mass  slightly  more 

attacked.     The  residual  cellulose  is  washed,  in  the 

^digesters  themselves  or  in  hollanders,  with  water  and 

steam  and  is  then  mixed  with  the  quantity  of  rag 

half -stuff  necessary  for  the  kind  of  paper  required, 

the  whole  being  then  worked  in  the'hollander  into 

the  refined  pulp  (see  later). 

(b)  Calcium    Bisulphite    (Mitscherlich)    or    Mag- 
nesium Bisulphite  (Ekman)  Process.     This  process  is 

the  one  most  largely  used  at  the  present  time,  as  it 

gives  a  cellulose  of  better  quality  than  the  preceding 

method.     The  wood  is  heated  under  pressure  (115° 

to   130°  or  2-5  to  4  atmos.)  in  large  autoclaves  lined 

inside  with  cement  or  brickwork  with  a  solution  of 

calcium  bisulphite,  Ca(S03H)2,  or  magnesium  bisul- 
phite, which  dissolves  the  encrusting  matter  but  does 

not  act  on  the  cellulose  1  ;   the  liquid  is  circulated 

inside  the  boiler  by  means  of  an  injector  or  by  leaving 

a   small  upper  tap  slightly  open.     The   bisulphite 

solution  of  4°  to  5°  Be.  (about  30  grms.  of  SO2  per 

litre,  approximately  one -third  being  combined  with 

lime)  is  prepared  in  very  tall  wooden  towers  (that  of 

Harpf  being  as  much  as  55  metres  high),  usually 

lined  with  lead  and  filled  with  limestone  or  dolomite 

(Fig.   392).     A  current  of   sulphur  dioxide    ascends 

from  the  bottom  to  the  top  of  the  tower,  while  the  trough,  6ls  supplied  by  the  reservoir,  S, 

at  the  top,  yields  a  fine  spray  of  water  ;  the  bisulphite  solution  is  collected  at  the  bottom. 

1  Lignin  is  dissolved  with  remarkable  ease  by  calcium  bisulphite,  giving  a  stable  soluble  compound,  the  sulphur 
dioxide  in  which  is  neither  detectable  by  iodine,  nor  capable  of  being  set  free  by  sulphuric  acid,  nor  able  to  exert 
reducing  action.  Sulphurous  acid  alone  does  not  act  so  well  as  the  bisulphite,  the  lime  being  necessary  for  the 
formation  of  these  sulphonic  salts  and  for  the  neutralisation  of  the  sulphuric  acid  always  formed. 


FIG.  392. 


Harpf 's  tower  has  ten  gratings  (I  to  X),  connected  by  steps  not  shown  in  the  figure  ;  each 
of  these  can  be  charged  and  attended  to  independently  of  the  others  by  means  of  the 
door,  k.  The  first  six  gratings  are  cleaned  every  four  weeks,  but  the  others  far  less  often. 

The  sulphur  dioxide  issues  from  pyrites  furnaces  into  the  iron  tube,  c,  and  passes  down 
the  earthenware  pipe  b,  B  B  being  for  convenience  of  cleaning.  The  calcium  or  magnesium 
bisulphite  solution  deposits  its  suspended  matter  in  L  and  is  then  discharged  into  storage 
tanks.  When  the  whole  of  the  tower  is  to  be  washed,  the  plug,  P,  of  the  cistern  is 
raised. 

To  ascertain  the  completion  of  the  action  of  the  bisulphite  on  the  wood  in  the  digesters, 
a  sample  of  the  liquid  is  removed  now  and  then  and  treated  in  a  graduated  tube  with 
ammonia  ;  when  the  calcium  sulphite  occupies  one-sixteenth  of  the  volume  of  the  sample 
the  heating  is  stopped,  and  when  this  fraction  is  reduced  to  one  thirty-second  the  operation 
is  finished  and  the  coloured  liquor  can  be  discharged.  The  wood  is  sometimes  treated 
with  steam  before  being  introduced  into  the  bisulphite  boiler.  The  whole  operation,  in- 
cluding charging  and  discharging,  preliminary  treatment  of  the  wood  and  action  of  the  bi- 
sulphite, lasts  50  to  60  hours.  The  spent  bisulphite  liquor  is  highly  coloured  and  charged 
with  salts,  gummy  matters,  tannin,  glucose,  pentoses,  acetic  acid,  nitrogenous  .compounds, 
&c.,  and  it  is  usually  forbidden  to  turn  it  into  watercourses  or  bottomless  wells  ;  so 
that  it  is  often  purified  by  precipitation  of  the  sulphite  with  lime,  the  calcium  sulphite 
being  then  reconverted  into  the  bisulphite  by  sulphur  dioxide.  Attempts  have  also  been 
made,  but  with  little  success,  to  evaporate  the  residual  liquor  and  so  obtain  adhesive 
gummy  substances  utilisable  in  the  preparation  of  coal  briquettes.  In  a  factory  with  two 
boilers,  each  of  120  cu.  metres  capacity  (12  to  15  metres  high,  3-5  to  4  metres  in  diameter, 
and  about  2  cm.  thick),  each  of  these  is  charged  with  about  200  quintals  of  wood  and 
85  cu.  metres  of  bisulphite  solution.  With  a  monthly  output  of  1000  quintals  of  cellulose, 
the  daily  production  of  spent  liqxior  is  30  cu.  metres,  the  organic  residue  amounting  to 
8  per  cent,  and  the  ash  to  2  per  cent.  The  rational  disposal  of  these  spent  liquors  is  always 
a  serious  problem,  which  still  awaits  solution  ;  the  attempts  made  to  prepare  alcohol  from 
them  are  mentioned  in  the  note  on  p.  142. 

The  gases  emitted  can  be  deodorised  by  means  of  nitrous  vapours,  which  attack  the 
mercaptans. 

The  yield  of  cellulose  varies  with  the  quality  of  the  wood,  but  is  about  50  to  55  per 
cent. 

(c)  Electric  Process.  This  was  proposed  by  Kellner,  and  consists  in  passing  through 
closed  receptacles  containing  the  wood  a  solution  of  sodium  chloride  at  126°,  through 
which  an  electric  current  passes  ;  the  chlorine,  hypochlorous  acid,  and  caustic  soda  act 
together  in  the  nascent  state,  dissolving  the  encrusting  substances  of  the  wood  and  libera- 
ting the  cellulose.  This  process  has  not  yet  been  much  used. 

MECHANICAL  REFINING  OF  THE  CELLULOSE  AND  MECHANICAL  WOOD- 
PULP.  The  mass  of  wood,  more  or  less  finely  divided,  extracted  from  the  digesters  is 
coarsely  defibred  in  suitable  disintegrating  machines,  and  the  cellulose  and  the  mechanical 
pulp,  either  together  or  separately,  according  to  the  kind  of  paper  required,  are  introduced 
into  the  so-called  Hollanders,  where  they  are  completely  defibred  and  converted  into  a 
very  fine  pulp  ;  bleaching  with  calcium  hypochlorite  and  the  subsequent  washing  are  also 
carried  out  in  the  hollanders,  as  is  the  addition  of  dressing,  colour,  size,  resin,  alum,  &c., 
necessary  for  the  desired  paper. 

The  hollander  beating  machine  consists  of  a  large,  oblong  wooden  or,  better,  cement 
vessel  (A,  Figs.  393  and  394),  in  the  middle  of  which  is  a  vertical,  longitudinal  partition,  B, 
which  does  not  extend  to  the  ends  of  the  vessel.  In  one  part  of  the  vessel  is  a  large  revolving 
drum,  D,  furnished  at  its  periphery  with  a  number  of  cutters  which  circulate  the  'water 
containing  the  cellulose  or  mechanical  pulp.  The  bottom  of  this  part  of  the  vessel  is  in 
the  form  of  a  ridge  (PR,  Fig.  394),  and  at  a  point,  F,  on  one  of  the  slopes  are  fitted  cutters  ; 
the  drum  can  be  moved  up  or  down  by  means  of  the  lever,  HG,  and  the  distance  between 
its  cutters  and  those  at  F  thus  adjusted  as  required.  The  movement  of  the  water  produced 
by  the  rotation  of  the  drum  causes  almost  the  whole  of  the  cellulose  and  pulp  to  pass 
between  the  fixed  and  revolving  cutters,  and  after  some  time  the  woody  fibres  swim  sepa- 
rately in  the  water.  As  the  process  goes  on,  the  knives  are  gradually  brought  closer  together 
until  the  desired  degree  of  fineness  is  attained.  The  mass  passes  up  the  plane,  P,  down 
the  plane,  R,  round  the  partition,  B,  again  up  the  plane,  P,  and  so  on. 

n  33 


514 


ORGANIC    CHEMISTRY 


The  washing  water  can  be  changed  by  immersing  in  the  free  half  of  the  vessel  a  fine 
gauze  drum  from  which  the  water  can  be  aspirated  by  means  of  a  pump.  This  drum  is 
then  raised  by  the  chain  and  pulley,  R  (Fig.  393),  and  fresh  water  introduced  into*the  vessel. 
To  avoid  spurting  from  the  drum,  D,  it  is  fitted  with  a  cover,  T.  In  the  base  of  the  vessel 
and  in  front  of  the  inclined  plane  is  a  recess  for  catching  pieces  of  iron  or  stone  accidentally 
present  in  the  wood-pulp,  the  cutters  thus  being  protected  from  damage.  Fig.  193  on 
p.  237  shows  a  battery  o^hollanders,  which  are  also  used  for  guncotton. 


)f  li 


FIG.  393. 

SIZING  AND  FORMATION  OF  THE  PAPER.  The  refined  pulp  in  the  hollander, 
containing  the  different  raw  materials  (rags,  wood-pulp,  cellulose,  &c.)  in  the  requisite 
proportions,  is  blued  and  sized  before  being  transferred  to  the  continuous  machines.  The 
blueing  is  effected  by  adding,  a  short  time  before  the  end  of  the  be'ating,  500  to  1000  grms. 
of  ultramarine,  Prussian  blue,  or  aniline  blue  ;  a  little  later  the  size  is  added,  which  renders 
the  paper  impervious  to  water  and  prevents  ink  from  running  on  it  ;  if  blotting-paper  or 
filter-paper  is  required,  the  sizing  is  omitted.  Sizing  can  be  carried  out  on  the  finished 


FIG.  394. 

paper,  but  it  is  usually  preferred  to  add  the  dressing  directly  to  the  finished  pulp  while 
this  is  still  suspended  in  water,  since  in  this  way  all  the  fibres  become  coated  with  the 
size  without  losing  the  power  of  adhering,  one  to  the  other,  to  form  a  homogeneous,  felted 
mass  of  paper.  Animal  size  was  at  one  time  used,  but,  owing  to  its  ready  putrefaction  or 
alteration  even  while  it  is  being  applied,  it  has  been  ..almost  entirely  replaced  by  resin 
(colophony)  previously  rendered  soluble  (resin  soap)  by  means  of  caustic  soda.  With 
water  this  soap  forms  very  fine,  homogeneous  and  persistent  emulsions,  the  efficacy  of 
which  may  be  increased  by  the  addition  of  starch  paste  (in  amount  sometimes  equal  to 
that  of  the  resin)  or  of  casein  dissolved  in  dilute  soda  solution.  The  total  dressing  added 
amounts  to  2  to  5  per  cent,  of  the  dry  paper. 


FORMATION    OF    THE    PAPER 


515 


In  order  to  precipitate  the  resin  in  a  fine  state  of  division  on  the  fibres,  a  solution  of 
aluminium  sulphate  (or  of  potash  alum)  is  added  to  the  homogeneous  mixture  of  pulp  and 
resin  soap  ;  as  was  shown  by  Wurster,  this  effects  the  precipitation  of  the  resin,  starch 
(or  casein),  and  a  very  small  amount  of  aluminium  resinate.  Nowadays  one-half  of  the 
aluminium  sulphate  is  sometimes  replaced  by  the  cheaper  magnesium  sulphate.  The 
so-called  loaded  papers  are  obtained  by  adding,  in  addition,  a  considerable  quantity  (some- 
times 50  per  cent.)  of  kaolin, 
barium  sulphate,  talc,  or  cal- 
cium sulphate. 

The  colouring-matters 
(mineral  dyes,  lakes,  or  sub- 
stantive aniline  dyes)  are  also 
added  directly  to  the  finished 
pulp,  organic  dyes  being  the 
more  commonly  used.  The 
lakes  are  produced  by  mixing 
basic  dyes  with  the  pulp  and 
then  precipitating  with  tannin 
solutions  ;  for  direct  dyeing, 
substantive  dyes  (see  later, 

""*?""  Colouring  -  Matters)    are     em- 

PIG.  395.  ployed.      Powdered  lakes   ob- 

tained by  precipitating  either 

acid  aniline  dyes  with  aluminium  hydroxide  or  basic  dyes  with  tannin  or  tartar  emetic 
may  also  be  used. 

After  all  these  additions  have  been  made,  separation  of  any  of  the  components  from 
the  homogeneous  pulp  is  prevented  by  conveying  the  latter  into  two  vats,  where  it  is  kept 
in  motion  by  stirrers,  the  resultant  milk  being  more  or  less  dense  according  to  the  thickness 
of  paper  required.  Before  going  to  the  continuous 
machine  to  be  converted  into  paper,  the  pulp  is 
passed  through  a  purifier  (Pig.  395)  which  removes 
any  clots  of  fibre  still  present.  This  purifier  consists 
of  two  or  three  slightly  inclined,  oscillating  plates, 
perforated  with  very  fine  slots  ;  when  the  pulp  is 
fed  regularly  on  to  these  plates,  the  fine  fibres  pass 
through  while  the  lumps  are  discharged  into  channels 
provided  for  the  purpose. 

The  homogeneous  pulp  collected  under  the 
vibrating  plates  is  conveyed  to  the  continuous 
machine  at  an  almost  absolutely  regular  speed,  and 
on  this  depends  the  uniformity  in  the  thickness  of 
the  resultant  paper  ;  the  pulp  regulator  or  feeder 
should  hence  be  constructed  with  great  care.  If 
this  homogeneous  pulp  is  placed  on  a  very  fine 
sieve,  the  water  passes  through,  leaving  a  thin  layer 
of  interlaced,  adhering  fibres  which  can  be  removed 
in  the  form  of  a  wet  sheet.  The  preparation  of  the  PIG.  396. 

paper  in  the  continuous  machine  takes  place  in  a 

similar  manner.  The  pulp  is  distributed  uniformly  on  a  very  fine  endless  copper 
gauze  after  a  good  proportion  of  its  water  has  been  removed  by  draining  and  suction. 
A  cloth  then  passes  the  wet  sheet  to  a  pair  of  rolls,  which  compress  it  and  give  it  more 
consistency  ;  other  rolls  heated  to  130°  gradually  dry  the  paper,  while  others,  again, 
press  it  and  give  it  a  little  polish.  When  it  leaves  the  endless  gauze,  the  paper  is  sufficiently 
consistent  to  be  conveyed  to  the  supercalendar  (Fig.  396),  where  it  is  pressed  and  polished 
between  several  pairs  of  rolls.  Other  machines  wind  it  into  rolls,  cut  it,  rule  it,  &c. 

A  large  modern  continuous  machine  may  cost  several  thousands  of  pounds.  A  general 
view  of  such  a  machine  is  shown  in  Fig.  397  ;  the  two  vats  of  pulp  are  seen  at  a,  while  b 
represents  the  circular  feeder  carrying  buckets,  c  the  drum  sieve  which  collects  the  pulp  and 
passes  it  as  a  wet  sheet  to  the  metal  gauze,  d,  this  transferring  it  to  the  cloth  at  /  and 


516 


ORGANIC    CHEMISTRY 


passing  back  round  the  rollers,  e,  underneath  to  take  up  fresh  pulp  ;  g  shows  the  drying 
rolls  and  h  where  the  cloth  returns,  the  continuous  length  of  paper  being  drawn  off  at  i 
to  the  winding  apparatus. 

It  is  not  possible  here  to  consider  the  different  kinds  of  paper  now  manufactured,  or 
the  different  pulps  required,  or  the  special  modern  machines  devised  to  meet  all  the  require- 
ments of  the  trade,  but  a  few  words  may  be  devoted  to  the  testing  of  paper,1  the  pulp 
used  being  recognisable  under  the  microscope  by  the  magnitude  and  form  of  the  fibres 
(see  Figs.  398  et  seq.).  As  will  be  shown  in  the  chapter  on  Textile  Fibres,  the  fibres  of  paper 
are  corroded  and  somewhat  distorted  and  resemble  the  original  fibres  only  in  certain 
characters. 

The  fibres  of  the  white  fir  are  shown  in  Fig.  398  at  A  and  in  transverse  section  at  B  ; 
they  are  brown  and  are  characterised  by  the  pores  arranged  in  concentric  circles.  Fig.  399 
shows  at  B  altered  cotton  fibres  and  at  L  those  of  linen.  Fig.  400  gives  an  idea  of  the 
microscopical  appearance  of  mechanical  wood-pulp  of  the  conifers  (fir,  pine,  &c.)  with 
medullary  rays,  while  Fig.  401  shows  chemical  pulp  from  the  conifers  ;  in  the  latter 
case,  the  concentric  circular  pores  are  less  marked  and  the  fibres  more  homogeneous. 
Fig.  402  shows  straw  cellulose  with  the  very  thin  parenchymatous  cells,  a,  rounded  at  the 
ends,  and  the  superficial  toothed  cells  of  the  epidermis,  o,  mixed  with  the  bulk  of  ordinary 
elongated  and  striated  fibres.  Esparto  fibres  resemble  those  of  straw  to  some  extent  but 


FIG.  397. 


are  lacking  in  thin  and  terminal  cells,  while  the  toothed  edges  are  different  in  nature  and 
are  found  in  smaller  cells  than  in  straw ;  esparto  contains  certain  isolated  fibres  having 

1  Testing  of  Paper.  The  presence  of  mineral  loading  is  detected  by  determining,  in  a  platinum  crucible, 
the  ash  of  1  to  2  grms.  of  the  paper,  cut  up  and  dried  at  100°  to  105° ;  non-loaded  paper  contains  0'4  to  2'5  per 
cent,  of  ash.  To  detect  the  presence  of  mechanical  wood-pulp,  the  paper  is  immersed  in  an  aqueous  solution 
of  aniline  sulphate,  which  imparts  a  golden-yellow  colour  to  the  crude  wood  fibre  ;  or  use  may  be  made  of  aqueous 
phloroglucinol  faintly  acidified  with  hydrochloric  acid,  this  dyeing  the  crude  wood  fibre  (mechanical  pulp)  red. 
The  impermeability  or  solidity  of  the  sizing  is  determined  by  Leonardi's  method  ;  on  to  the  paper,  stretched  and 
inclined  at  60°,  a  solution  containing  1  per  cent,  of  ferric  chloride,  1  per  cent,  of  gum  arabic,  and  0-2  per  cent, 
of  phenol  is  allowed  to  fall  drop  by  drop  so  as  to  form  a  number  of  moist  strips  which  are  then  allowed  to  dry ; 
similar  strips,  crossing  the  first  and  perpendicular  to  them,  are  next  made  with  a  solution  containing  1  per  cent. 
of  tannin  and  0-2  per  cent,  of  phenol ;  the  formation  of  a  black  stain  of  tannate  of  iron  at  the  point  of  intersection 
indicates  bad  sizing,  absence  of  stain  shows  perfect  sizing,  and  stains  more  or  less  grey  denote  more  or  less  good 
sizing. 

Resin  sizing  is  recognised  by  pouring  a  few  drops  of  ether  on  to  the  paper  and  allowing  them  to  evaporate ; 
the  formation  of  transparent  rings  indicates  the  probable  presence  of  resin.  Or  a  few  grms.  of  the  paper  may 
be  boiled  with  absolute  alcohol  containing  a  few  drops  of  pure  acetic  acid,  the  solution  being  afterwards  poured 
into  distilled  water ;  if  the  latter  becomes  turbid,  the  presence  of  resin  is  certain. 

To  detect  animal  sizing,  a  few  grms.  of  the  paper  are  boiled  with  a  very  small  quantity  of  distilled  water, 
the  liquid  being  filtered,  highly  concentrated  and  treated  with  a  solution  of  tannin  ;  if  size  is  present,  whitish 
grey  flocks  are  formed,  which,  when  observed  under  the  microscope  in  contact  with  a  dilute  solution  of  iodine 
in  potassium  iodide,  are  seen  to  be  coloured  brown,  while  if  starch  is  present  this  is  coloured  blue ;  the  test  for 
starch  may  be  made  directly  on  the  paper  itself. 

The  presence  of  free  mineral  acid  is  ascertained  by  boiling  the  paper  in  a  little  distilled  water  and  noting  if 
the  solution  turns  Congo-red  paper  blue  or  black. 

For  the  microscopical  examination  (see  Figs.  398-402),  the  fibres  are4iberated  as  follows :  3  to  5  sq.  cm.  of 
the  paper  are  boiled  and  vigorously  shaken  for  two  minutes  with  3  to  4  per  cent,  caustic  soda  solution,  the  pulp 
thus  formed  being  poured  on  to  a  very  fine  metal  sieve  and  washed  well  with  tepid  water.  The  fibres  are  then 
tested  microchemically  with  solutions  containing  (1)  6  parts  of  iodine,  potassium  iodide,  10  parts  of  glycerol,  and 
90  of  water,  and  (2)  100  part?  zinc  chloride,  10-5  of  potassium  iodide,  0-5  of  iodine,  and  75  of  water,  the  clear 
liquid  being,  in  this  case,  decanted  from  the  precipitate  formed  ;  linen,  hemp,  and  cotton  are  coloured  pale  to 
dark  brown  by  solution  (1),  the  thin  fibres  remaining  almost  colourless,  while  with  solution  (2)  a  more  or  less 
intense  wine-red  coloration  is  obtained. 

An  alcoholic  solution  of  phloroglucinol  containing  hydrochloric  acid  does  not  colour  pure  cellulose  but  reddena 


PAPER    STATISTICS 


517 


the  form  of  teeth  or  elongated  pears.  Spain  exported  more  than  90,000  tons  of  esparto  in 
1872  and  about  46,000  in  1900.  Algeria  now  exports' 80,000  tons,  Tunis  30,000,  Tripoli 
75,000,  and  Morocco  4000.  Algeria  contains  5,000,000  hectares  under  esparto.  England 
imports  about  200,000  tons  of  esparto  per  annum. 

STATISTICS.  Books  and  reviews  often  contain  contradictory  and  fantastic  statistics 
concerning  the  output  of  paper.  According  to  the  most  trustworthy  data,  the  world's 
production  of  paper  and  pasteboard  in  1906  amounted  to  about  8,000,000  tons,  and  that 
of  cellulose  in  1908  was  estimated  at  1,600,000  tons  of  the  value  of  £16,000,000. 

In  1904  the  United  States  produced  2,000,000  tons  of  mechanical  pulp  and  4,000,000 
tons  of  paper  and  pasteboard,  worth  £32,000,000  ;  in  1860  the  output  was  200,000  tons, 
of  the  value  of  £5,200,000.  The  wood  converted  into  mechanical  pulp  represented  a  value  of 


FIG.  401. 


£5,600,000  in  1908,  and  more  than  £6,800,000  (from  253  factories)  in  1909.  The  value  of 
the  exports  was  £1,480,000  in  1904  but  is  rapidly  increasing,  and  already  exceeds  £4,000,000 ; 
in  1904  there  were  1200  paper  and  mechanical  pulp  factories,  with  a  total  capital  of  about 
£40,000,000,  one-half  of  this  representing  machinery. 

In  1911  the  United  States  imported  263,000  tons  of  mechanical  wood-pulp,  213.000 
tons  of  cellulose  (£1,296,000),  and  86,000  tons  of  bleached  pulp  (£737,800). 

impure  cellulose,  the  presence  of  wood-pulp  (i.e.  impure  cellulose)  in  paper  being  hence  detectable  in  this  manner. 
Further,  aniline  sulphate  or  naphthylamine  hydrochloride  colours  impure  cellulose  yellow,  but  does  not  alter 
pure  cellulose. 

The  bursting  strain  of  paper,  called  also  the  degree  of  elasticity,  is  determined  in  the  directions  of  the  length 
and  breadth  by  means  of  suitable  dynamometric  apparatus,  the  elongation  which  occurs  before  rupture  being 
expressed  as  a  percentage  of  the  length  (this  varies  from  1-5  to  4  per  cent,  for  different  papers).  The  breaking 
length  expresses  the  length  of  a  uniform  strip  of  paper  which  would  tear  under  its  own  weight  if  suspended  from 
one  end  :  if  a  strip  10  cm.  wide  of  paper  of  which  1  sq.  metre  weighs  70  grms.  breaks  under  a  load  of  3500  grms. 

S500 
the  breaking  length  is  — —  X  1000  =  5000. 

The  resistance  to  folding  is  determined  roughly  by  crushing  and  rubbing  an  irregular  ball  of  the  paper  between 
the  hands  ;  when  different  papers  are  compared  in  this  way,  that  with  the  least  number  of  creases  is  the  best. 


518  ORGANIC    CHEMISTRY 

Germany  in  1899  contained  900  paper  and  pasteboard  factories,  72  wood-cellulose 
factories,  30  straw-cellulose  factories,  and  600  mechanical  wood-pulp  factories,  using  a 
total  of  125,000  hydraulic  horse-power  and  75,000  steam  horse-power,  employing  65,000 
operatives,  and  producing  270,000  tons  of  cellulose  (550,000  tons  in  1909),  300,000  tons  of 
mechanical  pulp,  and  800,000  ton  s  of  paper  and  pasteboard.  In  1 884  the  output  of  paper  and 
paste-board  was  200,000,  and  in  1904  more  than  1,200,000  tons  of  the  value  of  £12,600,000. 
The  imports  in  1904  were  24,000  tons  of  paper  and  pasteboard,  the  same  quantity  of 
mechanical  pulp,  and  about  47,000  tons  (32,550  tons  in  1909)  of  cellulose  ;  the  exports 
were  64,000  tons  of  cellulose  in  1904  (147,088  tons  in  1909),  6000  tons  of  mechanical  pulp, 
and  250,000  tons  of  paper  and  pasteboard.  In  1908  Germany  imported  833,480  tons  of 
wood  for  paper,  and  in  1909  about  1,653,000  tons,  exporting  about  40,000  tons. 

The  price  of  wood- cellulose  in  Germany  was  42s.  per  quintal  in  1852,  and  is  to-day  less 
than  16s. 

In  Norway  the  first  manufactory  of  mechanical  pulp  was  erected  in  1870  and  the  first 
of  cellulose  in  1880,  and  in  1905  the  paper  industry  occupied  8000  workpeople,  the  output 
being  100,000  tons  of  paper.  In  recent  years  this  industry  has  advanced  considerably, 

27  factories  now  possessing  a  total  of  60  continuous  machines  and  the  production  of 
paper  in  1910  being  150,000  tons  (of  the  .value  of  £1,520,000),  nine-tenths  of  this  being 
for  export. 

In  1891  Sweden  possessed  40  paper  factories,  occupying  3000  workpeople  and  producing 
36,000  tons  of  paper,  worth  £480,000.  In  1906  the  output  of  paper  was  209,000  tons 
(£2,400,000),  and  in  1907,  225,000  tons  (£2,560,000).  Sweden  produced  mechanical  wood- 
pulp  to  the  value  of  £3,080,000  in  1906  and  £3,760,000  in  1907,  part  of  it  being  exported. 

France  produced  about  75,000  tons  of  paper  in  1860,  about  60,000  operatives  being 
employed  in  the  industry  in  1901  ;  in  1904  the  output  was  almost  450,000  tons. 

In  Russia  the  consumption  of  paper  is  continually  increasing,  but  the  amount  produced 
is  almost  stationary  :  163,800  tons  in  1897,  177,000  in  1900,  and  205,000  (£7,600,000)  in 
1906  ;  so  that  Russia  imports  a  considerable  quantity  of  paper,  even  from  Japan  and  China, 
but  more  especially  from  Finland,  whose  exports  of  paper  to  Russia  have  increased  sixfold 
during  the  last  ten  years. 

Finland  exported  nearly  43,000  tons  of  mechanical  pulp  and  about  13,000  tons  of  cellu- 
lose in  1906,  largely  to  Russia. 

Austria  produced  about  350,000  tons  of  paper  in  1904. 

England  in  1860  produced  about  100,000  tons  of  paper  and  now  produces  rather  less 
than  Germany  ;  in  1909  the  imports  included,  besides  rags  (q.v.),  197,501  tons  of  esparto, 
&c.,  of  the  value  of  £720,000,  and  749,740  tons  of  mechanical  wood-pulp  and  cellulose,  worth 
£3,480,000. 

The  imports  of  raw  materials  for  paper-making  into  England  were  valued  at  £4,741,230 
and  the  exports  at  £820,730  in  1911  ;  the  imports  of  paper  of  different  kinds  amounted 
to  £6,574,500  and  the  exports  to  £3,311,867  in  1911. 

In  1906  Spain  produced  more  than  35,000  tons  of  paper. 

The  paper  industry  in  Italy  has  increased  very  considerably  in  recent  years,  the  produc- 
tion being  60,000  tons  in  1876  and  almost  70,000  in  1886,  the  importation  of  cellulose 
being  as  follows  :  1800  tons  in  1886  ;  13,600  in  1896  ;  24,300  in  1901  ;  42,000  in  1905  ; 
46,700  in  1907  ;  54,000  in  1908  ;  and  63,100  tons,  of  the  value  of  £706,400,  in  1910.  The 
production  of  cellulose  in  Italy  is  very  small,  there  being  but  three  factories.  In  1896 

28  mechanical  pulp  factories  produced  10,000  tons  of  the  pulp,  4200  tons  of  which  were 
imported  in  the  same  year  and  8741  tons  (£62,936)  in  1910.    The  total  production  of  paper 
and  cardboard  in  Italy  in  1907  was  about  200,000  tons  ;   30,000  tons  of  this  was  used  for 
daily  papers  weighing  45  grms.  per  sq.  metre  (24s.  to  28s.  par  quintal). 

The  Customs  duty  on  paper  in  Italy  varies  from  about  6s.  to  36s.  per  quintal  for  different 
qualities. 

The  following  numbers  represent  the  mean  annual  consumption  of  paper  in  kilos  per 
inhabitant  for  various  countries,  these  being  regarded  as  a-jough  indication  of  progress : x 

•  About  75,000  new  books  are  published  per  annum  in  the  whole  world,  these  requiring  25,000  tons  of  mechani- 
cal pulp  alone.  In  addition,  about  30,000  periodicals  are  published  with  a  total  circulation  of  nearly  11,000,000,000 
copies  and  for  these  1000  tons  of  mechanical  pulp  are  consumed  per  day. 

Of  the  total  output  of  paper,  32  per  cent,  is  for  ordinary  printing,  10  per  cent,  consists  of  fine  paper  and  writing 
paper,  10  per  cent,  of  brown  paper  and  cardboard,  6-3  per  cent,  of  fine  cellulose  and  rag  paper  for  fine  printing; 
5  per  cent,  of  straw  paper  and  card,  3  per  cent,  of  paper  for  placards,  &c.,  3  per  cent,  of  wall-paper,  0-6  per  cent. 


CONSUMPTIONOF    PAPER  519 

United  States,  19-3  ;  England,  17-2  ;  Germany,  14  ;  France,  11-5  ;  Austria,  9-5  ;  Italy, 
7-5  ;  Spain,  2-5  ;  Russia,  2-3  ;  Servia,  0-6  ;  China,  0-6  ;  India,  0-13. 

of  drawing  paper,  0-5  per  cent,  of  silk  paper,  cigarette  paper,  and  paper  for  making  flowers ;  0-4  per  cent,  of 
blotting-  and  filter-paper,  <$rc. 

Although  the  consumption  of  paper  has  increased  to  an  extent  that  would  have  been  incredible  a  few  years 
ago,  yet  the  day  is  far  distant  when  a  scarcity  of  raw  material  will  be  experienced.  Canada  alone,  with  its 
322,000,000  hectares  of  forest  land  can  supply  the  whole  world  for  several  centuries.  Of  other  reserves  of  forest 
the  most  important  are  those  of  the  United  States,  200,000,000  hectares ;  Russia,  184,000,000  ;  Queensland, 
86,000,000  ;  Siberia,  38,000,000  ;  British  India  and  Burmah,  26.000,000  ;  Finland,  Sweden,  and  Japan  (excluding 
Formosa  and  Hokkaido),  20,000,000  each  ;  Germany,  17,000,000  ;  Austria  and  France,  10,000,000  each  ;  Hungary, 
Croatia,  and  Slavonia,  9,000,000  ;  New  Zealand,  8,000,000  ;  Asiatic  Turkey,  7,000,000 ;  Norway,  6,000,000  ; 
Hokkaido  (Japan),  6,000,000 ;  Italy,  4,500,000,  &c.  In  Burmah  and  elsewhere  there  are  immense  tracts  of 
bamboo,  which  will  one  day  be  utilised  for  the  manufacture  of  paper. 

It  cannot,  however,  be  denied  that  an  immense  amount  of  wood  is  used  for  building  purposes,  and  in  Italy, 
for  instance,  many  of  the  forests  have  been  destroyed,  so  that  the  imports  of  wood,  which  in  that  country  amounted 
to  £840,000  in  1871,  increased  to  £2,000,000  in  1900,  to  £2,840,000  in  1905,  and  to  still  greater  extents  (mostly 
from  Austria-Hungary  and  America)  in  recent  years  (see  vol.  i,  p.  204). 


PART  III.   CYCLIC  COMPOUNDS 

THE  aliphatic  series  contains  various  groups  of  closed-chain  compounds 
(e.g.  lactones,  uric  acid  derivatives,  anhydrides  of  dibasic  acids),  which  are 
readily  opened  by  simple  reactions  giving  ordinary  open-chain  compounds  of 
the  fatty  series. 

Numerous  substances  are,  however,  known  containing  a  closed-chain 
nucleus  which  is  composed  of  3,  4,  5,  or  more  commonly  6,  carbon  atoms  united 
in  a  special  manner  and  is  resistant  to  the  most  energetic  reagents.  These 
compounds  form  the  important  group  of  aromatic  compounds. 

Other  groups  of  cyclic  substances  are  also  known  with  nuclei  composed, 
not  of  carbon  atoms  alone,  but  of  several  elements,  e.g.  pyridine,  C5H5N,  in 
which  the  nucleus  contains  5  carbon  atoms  and  1  nitrogen  atom  ;  pyrrole, 
C4H5N,  with  C4  and  N  in  the  nucleus  ;  furan,  C4H40,  with  a  C40  nucleus  ; 
thiophene,  C4H4S,  with  a  C4S  nucleus  ;  pyrazole,  C3H4N2,  with  the  nucleus 
C3N2,  &c.  These  compounds  are  called  heterocyclic. 

There  are  also  many  substances  derived  from  more  complex  nuclei  formed 
by  the  condensation  of  two  or  more  of  the  nuclei  mentioned  above,  e.g.  naph- 
thalene, C10H8,  in  which  are  condensed  two  benzene  nuclei  held  together  by 
two  carbon  atoms  common  to  the  two  nuclei,  and  quinoline,  with  a  nucleus 
analogous  to  that  of  naphthalene  but  composed  of  one  benzene  and  one 
pyridine  nucleus. 

AA.    ISOCYCLIC   COMPOUNDS 

These  contain  1  or  several  homogeneous  carbon  atom  rings,  and  can  be  sub- 
divided, according  to  the  type  of  linking,  into  (1)  Polymethylene  Compounds, 
which  contain  singly  linked  carbon  atoms  and  are  less  resistant  to  chemical 
reagents  than  (2)  Benzene  Derivatives,  where  the  carbon  atoms  are  linked  very 
differently  (see  later}.  Compounds  of  the  first  group  approach  those  of  the 
aliphatic  group  in  their  chemical  properties  and  are  hence  intermediate 
to  methane  and  benzene  derivatives. 

I.  CYCLOPARAFFINS  AND  CYCLO-OLEFINES  OR 
POLYMETHYLENE  COMPOUNDS 

xCH2 
TRIMETHYLENE  (Cyclopropane),  CH2\  |      ,  is  obtained  by  the  action  of  sodium 

^CU2 

on  ay-dibromopropane,  CH2Br  •  CH2  •  CH2Br,  the  bromine  being  eliminated  and  the  chain 
closed.  It  is  a  gas  which  liquefies  at  a  pressure  of  5  to  6  atmos.  and  combines  very  slowly 
with  bromine  or  hydriodic  acid  giving  open-chain  compounds,  so  that  it  is  easily  dis- 
tinguished from  propylene  CH2  :  CH>CH3.  Its  heat  of  combustion  is  much  greater  than 
that  of  propylene,  into  which  it  is  partially  converted  at  400°. 

Its  derivatives  are  obtained  from  ethylene  bromide  by  means  of  the  ethyl  malonate 
synthesis  (see  p.  308). 

CH2\         xCO2-H 
Trimethylenedicarboxylic  Acid,    |       /C\  »    was  obtained  by  Perkin  by   the 

CH/      XCO2H 

interaction  of  ethylene  bromide  and  ethyl  sodiomalonate. 

530 


•AROMATIC    COMPOUNDS  521 

TETRAMETHYLENE  (Cyclobutane)  is  not  known  in  the  free  state,  but  derivatives 
of  it  are  obtainable  by  syntheses  similar  to  those  used  for  trimethylene  compounds. 

vx.ri2  •  v*il2\ 
PENTAMETHYLENE  (Cydopentane),    \  */>CH2,   is  a  liquid  boiling  at  50°; 

vs.tl2  '  v'.rio 

its  derivatives  are  prepared  by  the  ethyl  malonate  synthesis. 

According  to  Baeyer's  tension  hypothesis  (see  p.  88  and  Fig.  247,  p.  306),  it  is  easy  to 
understand  why  pentamethylene  is  the  most  stable  of  the  preceding  compounds,  a  ring  of 
five  carbon  atoms  being  the  only  one  which  can  be  formed  without  tension  of  the  linkings. 
Indeed,  while  trimethylene  combines  with  Br  or  HI  with  rupture  of  the  ring,  penta- 
methylene does  not  unite  with  bromine  and  resists  the  action  of  nitric  or  sulphuric  acid 
like  a  saturated  hydrocarbon,  the  properties  of  saturated  open-  and  closed-chain  compounds 
hence  differing  but  little. 

KETOPENTAMETHYLENE  (Cyclopentanone),  C5H8O,  is  obtained  by  the  dry  distilla- 
tion of  calcium  adipate  : 

CH2.CH2.CO(\  CH2.CH2X 

\Ca  =  CaC03  +   |  )CO  ; 

CH2-CH2.CO(K  CH2.CH/ 

by  reduction  and  subsequent  treatment  with  HI  it  gives  pentamethylene,  whilst  oxidising 
agents  convert  it  into  glutaric  acid,  these  reactions  proving  its  constitution.  Ketohexa- 
methylene  is  obtained  similarly  by  distilling  Calcium  Pimelate,  C7H1004Ca,  and  higher 
homologues  by  distilling  the  corresponding  calcium  salts  of  higher  dibasic  acids  ;  Calcium 
Suberate,  CgH^O^Ca,  for  example,  yields  Ketoheptamethylene  (suberone).  The  yield 
diminishes  with  increase  of  the  number  of  carbon  atoms. 

CH : CH. 
CYCLOPENTADIENE,  |  yCH2,  is  a  liquid  boiling  at  41°,  and   is  found   in 

CH : CH/ 

the  first  distillate  of  crude  benzene  and  also  in  illuminating  gas  ;  it  combines  with  iodine 
and  with  hydrogen  sulphide.  The  presence  of  two  double  linkings  in  the  nucleus  is  deduced 
from  the  fixation  of  four  atoms  of  halogen.  The  two  hydrogen  atoms  of  the  CH2  readily 
react,  e.g.  with  acetone,  giving  intensely  red  hydrocarbons  : 

CH :  CH\  CHg\  CH :  CHx 

>CH2  +          )CO  =  H20  +|  / 

CH.-CH/  CH3<  CH:CHX  CH3 

this  compound  is  known  as  dimethylfulvene,  fulvene  being  an  isomeride  of  benzene  of  the 

CH :  CH^ 
structure    |  /C  :  CH2. 

CH :  CH/ 

II.  BENZENE  DERIVATIVES  OR  AROMATIC  COMPOUNDS 

It  was  observed  by  several  chemists  about  the  middle  of  last  century 
that  a  whole  series  of  compounds,  mostly  aromatic  in  nature,  besides  exhibiting 
certain  common  physical  and  chemical  characters,  showed  on  analysis  pro- 
portions of  hydrogen  very  low  in  comparison  with  those  of  carbon  and  also 
very  low  compared  with  those  of  hydrogen  in  saturated  or  unsaturated  com- 
pounds of  the  methane  series,  e.g.  CnH2n-j-2,  CnH2n,  C»H2W-2'  &c- 

In  general  the  hydrocarbons  of  these  substances  correspond  with  the  fundamental 
formula,  CnH2M_6,  and  the  various  transformations  of  the  aromatic  substances  often  yield 
Benzene,  C6H6,  from  which  they  can  again  be  prepared.  If  the  constitutional  formula  of 
benzene  were  an  open -chain  one,  it  would  be  necessary  to  assume  the  presence  of  double 
or  triple  linkings  between  carbon  and  carbon  which  would  lead  to  ready  addition  of  bromine 
and  to  ready  oxidation.  But  these  reactions  do  not  occur,  and  the  great  stability  of  the  com- 
pounds of  this  group,  and  of  benzene  in  particular,  can  be  explained  only  by  the  existence 
of  a  stable  nucleus  of  carbon  atoms,  probably  joined  in  the  form  of  a  closed  ring. 

It  was  found  later  that  benzene  forms  only  one  monosubstituted  product  (nitrobenzene, 
bromobenzene,  &c.),  and  that  all  the  hydrogen  atoms  of  benzene  exist  under  similar 


522 


ORGANIC    CHEMISTRY 


conditions ;  three  isomeric  disubstituted  products  (e.g.  dinitro-  or  dibromo -benzene) 
are,  however,  known. 

With  the  empirical  formula  C6H6  correspond  the  three  rational  formulae  :  (a)  C4(CH3)2, 
(/3)  C3(CH2)3,  and  (y)  (CH)6.  Formulae  (a)  and  (/3)  would  give  only  two  isomeric  disubsti- 
tuted products,  whilst  in  the  case  of  (y),  if  the  six  CH  groups  were  joined  in  the  form  not 
of  an  open  chain  but  of  a  closed  ring,  the  six  hydrogen  atoms  would  be  under  the  same 
conditions,  and  the  formation  of  a  single  monosubstituted  product  and  of  three  iscmeric 
disubstituted  products  would  be  explained. 

It  was  Kekule  who,  in  1865,  first  advanced  the  ingenious  hypothesis  that  the  funda- 
mental compound  of  aromatic  substances  is  benzene,  the  constitutional  formula  of  which 
must  be  represented  as  a  closed,  hexagonal  chain  of  carbon  atoms  united  alternately  by 
single  and  double  linkings,  the  fourth  valency  of  each  carbon  atom  being  united  to  a 
hydrogen  atom.  Such  an  arrangement  is  figured  in  the  scheme 

H 
C 

HC/iy= 


HC 


CH 


G 
H 


or,  if  the  six  carbon  atoms  are  represented  by  tetrahedra  (see  p.  18  et  seg.),  in  the  diagram 
shown  in  Fig.  403.  The  carbon  atoms  combined  with  the  substituents  in  the  three  disub- 
stituted derivatives  would  then  be  :  (a)  1  and  2  (ortho- 
derivatives),  (b)  1  and  3  (meto-derivatives),  and  (c)  1 
and  4  (para-derivatives)  ;  the  1  :  5-  and  1  :  6-  com- 
pounds would  be  identical  with  the  1  :  3-  and  1  :  2- 
compounds  respectively.  For  the  sake  of  shortness, 
the  terms  ortho-,  meta-,  and  para-  are  contracted  to 
o-,  m-  and  p-,  these  being  prefixed  to  the  names  of 
the  compounds. 


FIG.  403. 


The  constitutional  formula  given  for  ben- 
zene by  Kekule  and  also  those  of  Claus  (1867), 
Baeyer  (1868),  Korner  (1869),  and  Ladenburg 
(1870)  would  seem  to  indicate  the  possible 
existence  of  2  ortho-substituted  derivatives, 
since  the  1  and  2  carbon  atoms  are  joined  by 
a  double  linking  and  numbers  1  and  6  by  a 
single  linking.  Hence  Claus  and  Korner  pro- 
posed the  hexagonal  formula  with  the  fourth  valencies  of  the  carbon  atoms 
joined  diagonally  (para -linking)  (Fig.  404,  A),  while  Ladenburg  preferred  the 
prismatic  formula  (Fig.  404,  Bl}  B2,  and  B3),  and  Armstrong  and  Baeyer 
the  centric  formula,  with  the  fourth  valencies  in  a  latent  (or  potential)  state 
and  directed  towards  the  centre  (Fig.  404,  C)  ;  see  also  Fig.  405. 

In  order  to  obtain  a  better  interpretation  of  the  formation  of  the  disubstituted  iso- 
merides  of  benzene,  Kekule  (1872)  developed  his  theory  further  on  the  assumption  that 
the  linkings  between  the  carbon  atoms  are  to  be  regarded  as  vibrations,  so  that  carbon 
atoms  2  and  6  of  the  Kekule  formula  are  in  identical  conditions.  These  oscillations  would 
explain  why  benzene  does  not  unite  readily  with  halogens  or  ozone  (see  p.  88  ;  also 
Ann.  Soc.  Chim.,  Milan,  1907,  p.  116,  and  Berichte  der  dewt.  chem.  GeselL,  1908,  p.  2782)  or 
give  Baeyer's  permanganate  reaction  (see  p.  88),  thus  behaving  almost  like  a  saturated 
compound.  But  even  Kekule's  oscillatory  formula  does  not  explain  completely  the  optical 
and  thermal  behaviour  of  the  aromatic  compounds  or  the  interesting  results  obtained  by 
Baeyer  on  the  hydrogenated  derivatives  of  benzene  subsequently  to  1886.  Indeed,  when 
two  or  four  hydrogen  atoms  are  added  to  benzene  so  as  to  form  dihydro-  or  tetrahydro- 
benzene,  the  latter  are  found  to  be  quite  different  from  true  aromatic  compounds  and  to 


STRUCTURE    OF    BENZENE 


523 


resemble  olefine  compounds  ;  it  must,  then,  be  assumed  that  where  the  hydrogen  has  not 
been  added,  true  double  linkings  are  formed  capable  of  combining  with  halogens  or  ozone 
and  of  giving  Baeyer's  permanganate  reaction.  Baeyer's  centric  formula  would  harmonise 
with  this  behaviour,  since  each  of  the  valencies  directed  towards  the  centre  is  kept  in 
equilibrium  with  all  the  others,  stability  being  thus  conferred  on  the  molecule  ;  if,  then, 
two  or  four  of  the  central  valencies  are  used  in  the  addition  of  hydrogen  or  other  groups, 
the  remaining  central  valencies  become  true,  olefinic,  double  linkings. 

There  are,  however,  aromatic  compounds,  especially  those  with  several  condensed 
benzene  nuclei,  with  which  Baeyer's  centric  formula  alone  cannot  be  assumed.    In  1899 


FIG.  404. 

Thiele  attempted  to  harmonise  all  the  chemical  and  physical  phenomena  observed  with 
benzene  and  its  derivatives  on  the  assumption  that  when  two  carbon  atoms  are  united 
by  a  double  linking  the  two  affinities  are  not  completely  utilised,  parts  of  the  unsatisfied 
valencies  (partial  valencies)  remaining.  These  are  regarded  as  bringing  about  addi- 
tion processes,  and  are  represented  by  dotted  lines, 
e.g.  C  =  C,  C  =  C  —  C  =  C,  &c.  But  when,  as  in  the  ^ 

latter  formula,  a  conjugated  system  of  double  bonds  is 
present,  the  addition  of  hydrogen,  halogens,  &c.,  occurs 
only  at  the  two  extreme  carbon  atoms,  the  partial 
valencies  of  the  two  middle  atoms  forming  a  new  inactive 
double  bond,  C  =  C  —  C  =  C  ;  after  the  addition  at  the 

extreme   carbon   atoms,  the  central  inactive   bond  becomes 

C  -  C=  C  -  C 

active  again,  the  constitution  then  being,    • 

H  H 

In  Kekule's  benzene  formula,  we  may  assume  the  existence  of  three  conjugated  double 

H 

(?°\ 

HC          CH 

bonds  with  three  inactive  bonds,  thus,        ||  |)        ;  it  would  then  be  clear  why  ben- 

HC          CH 


FIG.  405. 


zene,,  being  without  partial  valencies,  would  not  readily  form  additive  products,  and  why, 
when  even  a  single  inactive  double  bond  is  broken  down,  true  active  olefinic  double 
linkings  would  appear  (see  Theory  of  Double  Linking,  Note  on  p.  88). 

A  plausible  explanation  of  the  constitution  of  benzene  is  also  arrived  at  by  means 
of  the  ideas  of  motochemistry,  according  to  which  double  or  single  linkings  are  represented 
by  double  or  single  vibrations  or  blows  per  unit  of  time  (E.  Molinari,  Gazzetta  Chimica 
Italiana,  1893,  vol.  ii,  p.  4.1,  and  Journal  fur  praktische  Chemie,  1893,  p.  113). 


ISOMERISM  IN  BENZENE  DERIVATIVES 

It  has  been  seen  already  that  when  one  of  the  hydrogen  atoms  of  benzene 
is  replaced  by  a  halogen  or  an  organic  residue,  the  same  monosubstituted 
compound  is  always  obtained,  no  matter  at  what  point  of  the  molecule  the 
substitution  occurs.  If  two  substituent  groups,  either  similar  or  different, 
are  introduced,  three  disubstituted  derivatives  are  obtainable.  If  the  benzene 


524  ORGANIC    CHEMISTRY 

molecule  is  represented  simply  by  a  hexagon,  each  angle  of  which  indicates 
a  carbon  atom  united  with  a  hydrogen  atom,  replacement  of  the  latter  by 
another  atom  or  group  (x,  y,  z,  &c.)  may  be  shown  by  placing  the  symbol 
of  the  substituent  at  the"  angle  of  the  hexagon.  With  disubstituted  com- 
pounds, if  one  group  is  assumed  to  occupy  the  position  1,  the  other  may  go 
to  either  2  or  6  (or  tho -position),  3  or  5  (meta),  or  4  (para). 


Benzene    Monosubstitutcd          Ortho-compounds  Meta-derivatives  Para-derivative 

benzene  1 :  2-  and  1:6-  1:3-  and  1  :  5- 

(identical)  (identical) 

With  the  trisubstituted  derivatives,  three  isomerides  are  possible  when  the 
three  substituents  are  similar  (1:2:3-  or  vicinal,  identical  with  1:6:5-; 
the  symmetrical,  1:3:5-,  identical  with  2:4:6-;  and  finally,  the  unsym- 
metrical,  1:2:4-,  identical  with  1:5:4-): 


Vicinal  (i>)  Symmetrical  (s-)          Unsymmetrical  (as-) 

When  one  of  the  three  substituents  is  different  from  the  remaining  two,  six 
isomerides  are  possible  : 


'A     /*• 


Vicinal  Unsymmetrical  Symmetrical 

With  four  similar  substituent  groups,  it  will  readily  be  seen  that  three 
isomerides  are  possible. 

The  number  of  isomerides  may  be  further  increased  in  cases  where  one  or 
more  of  the  substituents  form  lateral  chains  capable  of  isomerism,  e.g.  saturated 
hydrocarbon  or  unsaturated  alcohol  or  acid  groups  ;  in  these  compounds, 
further  replacement  of  hydrogen  may  occur  either  in  the  benzene  nucleus  or 
in  the  side-chain,  fresh  cases  of  isomerism  being  thus  possible. 

It  was  Korner  (1869-1874)  who  first  showed  how  it  is  possible  to  deter- 
mine experimentally  the  'positions  of  the  various  substituent  groups  in  the 
benzene  nucleus  ;  examples  will  be  given  later. 

GENERAL  CHARACTERS  OF  BENZENE  DERIVATIVES 

While  the  saturated  hydrocarbons  of  the  aliphatic  series  offer  considerable 
resistance  to  oxidising  agents  and  to  concentrated  sulphuric  or  nitric  acid, 
those  of  the  aromatic  series  readily  give  nitro -derivatives  with  nitric  acid, 
and  sulphonic  derivatives,  having  an  acid  character,  with  sulphuric  acid  : 
C6H6  +  HN03  =  H20  +  C6H5-N02  (nitrobenzene)  ;  C6H6  +  H2S04  = 
H20  +  C6H5-S03H  (benzenesulphonic  acid).  In  the  latter,  the  sulphur  is 
united  directly  to  a  carbon  atom  of  the  benzene  nucleus,  this  being  confirmed 
by  the  fact  that  benzenesulphonic  acid  is  also  obtained  by  the  action  of 
oxidising  agents  on  thiophenol,  C6H5-SH,  in  which  the  sulphur  is  known 
to  be  joined  to  carbon. 


PREPARATION  OF  BENZENE,  ETC.   525 

Oxidation  of  aromatic  hydrocarbons  containing  side-chains  leads  to  the 
replacement  of  the  latter  by  carboxyl  groups,  C02H,  the  benzene  nucleus 
remaining  unchanged  ;  in  this  way  the  various  aromatic  acids  are  obtained  : 


)CH3  +  30  =  H20  +  0  >C02H  ; 


Toluene  Benzoic  acid 

CH2'CH3  C02H 

+  90  =  3H20  + 
CH8 

Ethyltoluene  Isophthalic  acid 

The  halogen  substitution  derivatives,  which  are  readily  obtained  by  the 
direct  action  of  the  halogens,  have  less  reactive  properties  than  the  halogen 
compounds  of  the  aliphatic  series  and  are  more  resistant  to  substitution. 

The  hydroxyl-derivatives  (e.g.  phenol,  C6H5-OH)  are  more  decidedly  acid 
in  character  than  the  alcohols  of  the  fatty  series,  the  phenyl  group,  C6H5, 
for  example,  being  more  negative  than  the  ethyl  group  ;  their  resistance  to 
oxidising  agents  is  similar  to  that  of  the  tertiary  alcohols,  to  which  they  are 
analogous  in  constitution,  the  grouped-  OH  being  present  in  both  cases. 

The  amino-derivatives,  which  are  readily  obtainable  by  reducing  the  nitro- 
derivatives  (CgHg-NOa  +  6H  =  2H20  +  C6H5-NH2,  aniline)  with  inter- 
mediate formation  of  azo-compounds  (q.v.),  are  easily  converted  by  the  action 
of  nitrous  acid  into  diazo-compounds  ;  the  latter  are  formed  only  seldom 
and  with  difficulty  in  the  case  of  aliphatic  compounds. 

In  their  last  investigations  Korner  and  Contardi  (1908)  show  how,  with 
the  substitution  products  of  benzene,  the  formation  of  one  isomeride  rather 
than  another  sometimes  depends  on  minimal  differences  in  the  physical 
conditions  under  which  the  reactions  take  place.  Thus,  in  the  nitration  of 
aniline  or  of  halogenated  derivatives,  a  very  slight  difference  in  the  concen- 
tration (even  in  the  second  decimal  place  of  the  specific  gravity)  is  sufficient 
to  alter  the  yield  very  considerably  or  even  to  give  entirely  different  products. 

FORMATION  OF  BENZENE  AND  ITS  DERIVATIVES 

When  vapours  of  aliphatic  compounds  are  passed  through  red-hot  tubes, 
the  products  formed  contain  aromatic  compounds.  At  a  red  heat  acetylene 
gives  benzene  (the  reverse  reaction  is  also  possible)  :  3C2H2  =  C6H6. 

When  allylene,  C3H4,  is  distilled  with  dilute  sulphuric  acid,  mesitylene, 
C6H3(CH3)3  (1:3:  5),  is  obtained,  while  under  similar  conditions  crotonylene, 
C4H6,  forms  hexamethylbenzene,  C6(CH3)6. 

In  presence  of  concentrated  sulphuric  acid,  several  aliphatic  ketones 
undergo  condensation  to  aromatic  hydrocarbons  ;  thus,  acetone  forms  1:3:5- 
trimethylbenzene,  3C3H60  =  3H20  +  C6H3(CH3)3. 

Acetoacetaldehyde,  CH3-CO-CH2-CHO,  when  liberated  from  its  sodium 
derivative,  is  transformed  immediately  into  triacetylbenzene,  C6H3(COCH3)3. 

Various  aromatic  compounds  can  also  be  obtained  by  the  action  of  sodium 
on  ethyl  bromoacetoacetate  or  ethyl  succinate,  by  heating  ethyl  sodiomalonate 
and  by  certain  other  syntheses. 

From  the  tar  obtained  by  distilling  coal,  wood,  or  lignite,  many  aromatic 
compounds  can  be  separated  :  5  to  10  per  cent,  of  naphthalene,  1  to  1-5  per 
cent,  of  benzene  and  toluene,  besides  quinoline,  anthracene,  &c. 

Benzoic  and  salicylic  acids,  bitter  almond  oil,  &c.,  occur  naturally  in  the 
vegetable  kingdom. 


526  ORGANICCHEMISTRY 

A.  AROMATIC   HYDROCARBONS 

Those  with  saturated  side-chains  are  colourless,  .  refractive  liquids  of 
characteristic  odour,  insoluble  in  water,  but  extremely  soluble  in  ether  or 
absolute  alcohol ;  they  are  lighter  than  water  (0-830  to  0-806). 

General  Methods  of  Preparation.  (1)  Alkyl  chlorides  and  aromatic  hydro 
carbons  in  presence  of  aluminium  chloride  give  mono-  and  poly-sub- 
stituted hydrocarbons,  which  can  be  separated  by  fractional  distillation  : 
C6H6  +  CH3C1  -  HC1  +  C6H5-CH3  (Friedel  and  Craft's  synthesis)  ;  inter- 
mediate aluminium  compounds  are  first  formed.  Ferric  chloride,  zinc  chloride, 
or  zinc  turnings  act  in  the  same  way  as  aluminium  chloride.  The  latter  salt 
also  brings  about  the  decomposition  of  the  higher  hydrocarbons  into  more 
simple  ones. 

(2)  In  presence  of  sodium,  monobromo-substitution  derivatives  of  aromatic 
hydrocarbons  and  alkyl  bromide  or  iodide  give  higher  aromatic  hydrocarbons 
(Fittig's  synthesis,  analogous  to  that  of  Wurtz  for  the  aliphatic  series)  : 

C6H5Br  +  C2H5I  +  Na2  ==  NaBr  +  Nal  +  C6H5-  C2H5. 

(3)  Distillation  of  calcium  salts  with  soda  lime  (analogous  to  the  synthesis 
of  aliphatic  hydrocarbons)  : 

(C6H5C02)2Ca  +  Ca(OH)2  =  2CaC03  +  2C6H6. 

Calcium  benzoatc 

(4)  Aromatic     sulphonic     derivatives     give     the     hydrocarbons     when 
heatsd   with    sulphuric    or   hydrochloric   acid,    best   in   presence    of   steam  : 
C6H5-S03H  +  H20  =  H2S04  +  C6H6.     On  this  reaction  is  based  the  methcd 
used  for  separating  aromatic  hydrocarbons  from  those  of  the  aliphatic  series, 
the  former  with  concentrated  sulphuric  acid  giving  soluble  and  the  latter 
(paraffins)  insoluble  sulphonic  acids. 

(5)  When  an  aromatic  hydrocarbon  is  dissolved  in  an  alcohol  in  presence 
of  zinc  chloride  at  about  300°,  water  separates  and  a  higher  hvdrocarbon  is 
formed  :  C6H6  +  C5HnOH  =  H20  +  C6H5-C5Hn. 

DISTILLATION  OF  TAR 

The  cheapest  and  most  abundant  hydrocarbons  used  as  raw  material  for  the  prepara- 
tion of  large  numbers  of  important  aromatic  compounds  (from  artificial  perfumes  to 
aniline  dyes)  are  obtained  by  the  distillation  of  tar.  While  at  one  time  this  product  con- 
stituted an  unpleasant  and  inconvenient  residue  of  the  illuminating  gas  industry  (see 
pp.  36-38,  52,  and  81),  it  is  now  so  much  in  demand  by  large  manufacturers  of  chemical 
products  that  it  is  sometimes  very  scarce,  and  attention  has  been  turned  to  the  utilisation 
of  the  tar  produced  in  metallurgical  coke  factories,  this  having  been  formerly  discarded. 

Westphalian  coal  gives,  on  an  average,  2-5  per  cent,  of  tar,  that  of  Saahr  as  much  as 
4  per  cent.,  and  that  of  Silesia  even  more  than  4  per  cent. 

The  first  attempt  to  utilise  tar  dates  back  to  1834  when,  in  a  works  at  Manchester,  it 
was  distilled  out  of  contact  with  air  in  primitive  retorts,  the  liquid  products  being  collected 
and  the  residual  pitch  employed  for  making  black  varnish.  Bethell  subsequently  patented 
a  process  for  obtaining  from  tar  creosote  oil  for  the  impregnation  and  preservation  of 
wood. 

Still  later  the  more  volatile  products  of  the  distillation  of  tar  were  used  both  as  an 
illuminant  and  as  a  cleaning  liquid.  Nitrobenzene  was  then  prepared  from  it  to  replace 
essence  of  mirbane. 

But  it  became  possible  to  develop  an  industry  for  the  regular  utilisation  of  tar  only 
after  the  wonderful  discovery  by  Perkin  (1856),  who  prepared  synthetically  the  first  arti- 
ficial coal-tar  dye,  thus  laying  the  foundation  of  one  of  the  most  important  industries 
for  which  the  nineteenth  century  is  famous, 


AROMATIC    HYDROCARBONS  527 

COMMONEST  AROMATIC  HYDROCARBONS  WITH  A  SINGLE  BENZENE  NUCLEUS 


Name 

national  formula 

Position  of 
substituents 

Melting- 
point 

Boiling- 
point 

Specific 
gravity 

C6H, 

Benzene 

+  5-4° 

+80-4° 

0-874  (^) 

C,H8 

Toluene  or  methyl- 

benzene 

C.H6-CH3 

— 

liquid 

110° 

0-869  (16°) 

C8H10 

o-Xylenc=o-dimcthyl- 

benzane 

C6H4(CH3)2 

1:2     • 

-  28° 

142° 

0-893  (0°) 

m-Xylene  =  m-dimethyl- 

benzsne 

„ 

1:3 

-  53° 

139° 

0-881  (0°) 

p-Xylene  =  p-dimethyl- 

benzene 

M 

1:4 

+  13° 

138° 

0-880  (0°) 

Ethylbenzene 

C6TId-C2H5 

— 

liquid 

136° 

0-883  (0°) 

C9H12 

Hemiinellithcne  =  tri- 

methylbcnzene  (v) 

C6H3(CII3), 

1:2:3 

,, 

175° 

— 

Pseudocumene  =  tri- 

methylbenzsne  (ns) 

» 

1:2:4 

„ 

169-5° 

0-895  (0°) 

Mesitylene  =  trimethyl- 

benzene  (s) 

„ 

1:3:5 

tj 

165° 

0-865  (14°) 

n-Propylbenzene         '. 

C,H5-C3H7 

— 

,, 

159° 

0-867  (14°) 

Isopropylbenzene     = 

cuniene 

M 

— 

,, 

153° 

0-866  (16°) 

C10H14 

Prehnitene  =  tetra- 

methylbenzene 

C6H2(CH3)4 

1:2:3:4 

—  4° 

204° 

— 

Isodurene  =  tetra- 

methylbenzene  (as) 

M 

1:2:3:5 

liquid 

195° 

— 

Durene  =  tetramethyl- 

benzene  (s) 

- 

1:2:4:5 

+  80° 

192° 

— 

m-Cymene  —  methyl- 

isopropylbenzene     . 

C8H4-CH3(C3n,) 

1:3 

liquid 

175° 

0-862  (20°) 

Cymeue  =  methyliso- 

propylbenzcne 

,, 

1  :4 

175° 

0-856  (20°) 

n-Butylbenzene  . 

C6H6-C4H9 

— 

180° 

0-864  (15°) 

sec.  Butylbenzene 

Jy 

— 

175° 

0-867  (15°) 

Isobutylbenzene 

n 

— 

171° 

0-371  (15°) 

tert.  Butylbenzene 

.. 

— 

167° 

0-871  (15°) 

CnH18 

Pentamethylbenzene 

C8H(CH3)5 

1:2:3:4:5 

+  51-5° 

231° 

0-847  (104° 

n-Amylbenzene  . 

C9H6-C5Hu 

—  . 

liquid 

202° 

0-860  (22°) 

Isoamylbenzene  . 

,, 

— 

,, 

194° 

0-885  (18°) 

C12H18 

Hexamethylbenz.iue 

C6(CH3)8 

1:2:3:4:5:6 

+  166° 

265° 

— 

Ci3H20 

n-Heptylbenzene 

O  IT  •  P  IT 

— 

liquid 

109°  (10  mm.) 

—      • 

C14H22 

n-Octylbenzene  . 

C6H8-C8H17 

— 

-  7° 

263° 

0-852  (14°) 

Ci6H28 

Pentaethylbenzene 

C8H(C2H5)5 

1:2:3:4:5 

liquid 

277° 

0-896  (20°) 

C18H30 

Hexaethylbenzene 

C6(C8H6)8 

1:2:3:4:5:6 

+  129° 

298° 

0-830.  (130°) 

C22H38 

Cetylbenzene 

CeHj-CmH.,, 

— 

+  27° 

230°  (15  mm.) 

0-857  (27°) 

C24H42 

Octadecylbenzene 

C8HS-C18H37 

— 

+  36° 

249°  (15  mm.) 

— 

Hexapropylbenzene 

C6(C3H7)6 

1:2:3:4:5:6 

+  118° 



MM 

C25H44 

Trimethylcetylbenzene 

CflH2(CH3)3(C18H33) 

1:3:5:2 

+  40° 

258°  (15  mm.) 

0-845  (40°) 

Numerous  industries  then  arose  for  the  more  complete  and  more  rational  utilisation  of 
tar — for  employing  to  the  best  advantage  the  various  products  of  its  fractional  distillation. 
Since  that  time  a  continuous  series  of  mechanical  improvements  in  the  plant  and  chemical 
ones  in  the  processes  have  been  introduced.  Improvements  in  the  coke  furnaces  to  admit 
of  the  collection  of  the  whole  of  the  products  of  distillation  and  of  the  rational  recovery  of 
the  heat  have  been  dealt  with  in  vol.  i  (p.  366). 

After  separation  from  the  ammoniacal  liquors  of  gas  manufacture  (by  ceritrifugation), 
tar  forms  a  dense,  almost  viscous,  blackish  (since  it  contains  10  to  30  per  cent,  of  suspended 
carbon  particles)  liquid  of  sp.  gr.  1-1  to  1-3.  It  contains  many  varied  acid,  basic,  and 
indifferent  products  ;  the  first  can  be  extracted  by  agitating  with  aqueous  alkali  solution, 
the  second  with  acids,  while  the  neutral  compounds,  consisting  principally  of  aromatic 
hydrocarbons,  form  the  residue.  The  composition  of  tar  varies,  however,  with  the  nature 
of  the  coal,  the  type  of  furnace,  and  the  temperature  of  distillation. 

It  seems  that  tar  contains  at  least  300  different  substances,  of  which  150  have  been 
established  either  directly  or  indirectly  and  90  have  been  isolated  with  certainty  and 
studied,  although  only  four  have  wide  application  in  the  pure  state  :  benzene,  phenol, 
toluene,  and  naphthalene. 

Only  to  a  small  extent  is  tar  used  as  it  is  :  for  varnishes,  coal  briquettes,  bitmnenised 


528 


ORGANIC    CHEMISTRY 


paper,  lampblack,1  treating  roads  to  render  them  less  dusty,  &c.  But  for  such  purposes 
the  residue  from  the  distillation  of  tar  can  also  be  used. 

A  little  tar  is  used  in  preparing  the  basic  lining  of  Bessemer  converters  for  the  manufac- 
ture of  steel. 

Nowadays,  however,  tar  is  mostly  subjected  to  distillation  for  the  extraction  of  the 
following  products  :  (1)  Indifferent  substances,  in  which  benzene  hydrocarbons  predominate 
(benzene,  toluene,  xylene,  tri-  and  tetra -methyl benzene,  and,  to  a  still  greater  extent, 
naphthalene,  anthracene,  &c.),  those  of  the  methane  series  being  small  in  amount  (these 
occur  abundantly  in  the  distillation  products  of  lignite-tar,  see  pp.  81  and  82).  Small  quan- 
tities of  nitrogen  compounds  occur,  such  as  acetonitrile,  benzonitrile,  carbazole  and  pyrrole 
derivatives,  and  also  traces  of  carbon  disulphide,  thiophene,  cumarone,  &c. ;  (2)  Acid 
substances,  among  which  phenol  (carbolic  acid),  cresol,  xylenol,  and  the  naphthols  abound. 
(3)  Basic  substances,  which  are  found  in  small  amount  and  contain  small  proportions  of 
pyridine  and  quinoline  compounds  and  a  trace  of  aniline. 

Wood-tar  is  of  less  value  than  coal-tar  ;  its  most  important  constituents  are  those 
soluble  in  alkali,  these  consisting  of  methyl  ethers  of  polyhydric  phenols  (pyrocatechol, 
pyrogallol  and  homologues,  forming  creosote  oil),  which  are  used  for  making  guaiacol. 
Wood-tar  is  distilled  in  a  vacuum,  the  gases  which  do  not  condense  being  utilised  for  power 
or  heating  purposes,  as  they  have  a  calorific  value  of  6000  to  9000  cals.  per  cubic  metre. 

The  distillation  products  of  coal-tar  are  approximately  as  follows  :  benzene  and  its 
homologues,  1-5  to  2-5  per  cent.  ;  phenol  and  its  homologues,  0-5  to  2  ;  pyridine  and 
quinoline  bases,  0-2  to  0-3  ;  naphthalene,  4  to  6  ;  heavy  oils,  20  to  26  ;  anthracene  and 
phenanthrene,  0-5  to  2  ;  pitch,  55  to  62  (38  being  asphalte  soluble  in  benzene  and  24 
carbon  or  insoluble)  ;  ammoniacal  liquor,  4  ;  gas  and  loss,  1-25. 

Another  source  of  aromatic  products  is  the  distillation  and  heating  of  lignite-tar  and 

1  Lampblack  is  prepared  by  the  incomplete  combustion  of  tar,  colophony,  vegetable  oils,  the  pitch  or  heavy 
oils  from  tar,  &c.  The  liquid  or  fused  substance  of  the  receivers,  a,  is  passed  through  pipes  to  the  long  pans,  A 
(Fig.  406),  in  which  it  is  heated  while  a  carefully  regulated  minimal  air-current  is  passed  over  the  surface  of  the 


Section    A    JC-T*. 

m 


FIG.  406. 

liquid  so  as  to  burn  the  vapours  incompletely  and  separate  the  greater  part  of  the  carbon  in  a  free  and  finely 
divided  state.  This  is  carried  away  by  the  air  into  the  first  arched  chamber,  B,  where  it  is  partly  deposited, 
then  into  the  second  arched  chamber,  c,  and  finally  into  D  (before  the  chimney,  0),  in  which  the  final  traces  of 
lampblack  are  deposited  on  a  thin  cloth  in  front  of  the  mouth  of  the  shaft.  This  operation  is  continued  for  five 
days,  the  sixth  day  (Sunday)  being  occupied  in  cooling  down  and  the  seventh  in  restarting.  A  very  fine  lamp- 
black is  obtained  by  burning  paraffin  oil  in  a  kind  of  lamp  with  a  wide  thin  jet  and  allowing  the  flame  to  impinge 
on  an  iron  cylinder  inside  which  water  circulates  ;  the  cylinder  thus  cools  the  flame  and  the  lampblack  deposited 
on  it  is  removed  from  time  to  time  by  an  automatic  scraper.  With  more  or  less  intense  cooling  the  lampblack 
has  a  lower  or  higher  specific  gravity.  100  kilos  of  tar  yield  25  kilos  of  lampblack,  while  100  kilos  of  resin  residue 
give  20  kilos.  Lampblack  contains,  in  addition  to  free  carbon,  tarry  impurities  and  oily  distillation  products. 
Attempts  have  been  made,  apparently  without  success,  to  prepare  lampblack  by  exploding  acetylene  with  a 
measured  proportion  of  air  in  closed  vessels.  The  Frank  process  seems  to  be  more  advantageous  ;  in  this,  acetylene 
is  burned  with  a  certain  proportion  of  carbon  monoxide  or  dioxide  :  C2H2  +  CO  =  H20  +  30. 

Swedish  lampblack  costs  16s.  to  20s.  per  quintal,  that  from  resinous  wood  40s.  to  52s.,  and  that  from  lamps 
£8  to  £20.  It  is  used  for  making  black  varnishes,  printers'  ink,  boot  polish,  &c.  Boot  polish  is  made  by  mixing 
;ampblack  with  wax,  molasses,  turpentine,  and  sometimes  also  sulphuric  acid  or  a  little  chestnut  tannin  extract 
to  preserve  the  skin  or  leather.  Italy  imported  and  exported  the  following  quantities  (quintals) : 


1905 

1907 

1908    S 

1909 

1910 

Lampblack  .Imports  .  .  . 
t  exports 

1070 
50 

1986 
20 

1684 
56 

1910 
26 

2440  worth    £4617 
97       „           £186 

Boot  polish  {sports  .  .  . 
1  exports  .  .  . 

2335 
1786 

3500 
1960 

4140 
1420 

4240 
1540 

6900       „       £10980 
2518       „         £4028 

DISTILLATION    OF   TAR 


529 


FIG.  407. 


petroleum  residues  (see  Cracking  Process,  &c.,  p.  74).  By  dropping  the  tar  into  very  hot 
retorts  and  evacuating  the  latter,  oils  for  various  industrial  purposes  and  also  gas  are 
obtained. 

The  distillation  is  carried  out  in  large  wrought-iron  vessels  J  holding  several  hundred 
quintals  of  tar.  The  old  type  of  boiler  is  shown  in  Fig.  407,  but  preference  is  now  given 
to  horizontal  stills,  which  are  sometimes  multitubular,  like  locomotive  boilers,  in  order 

to  obtain  more  homogeneous  and  more  rapid  heat- 
ing. It  will  be  seen  in  the  figure  that  direct -fire 
heat  is  used  (at  b)  ;  the  mass  is  mixed  at  intervals 
by  means  of  a  stirrer  or  of  a  steam-jet  introduced  at 
x  and  subdivided  on  the  arched  base  of  the  still  by 
a  number  of  pipes,  z.  The  tar  enters  at  r,  and  at  the 
end  of  the  operation  the  pitch  is  discharged  through 
a  much  wider  orifice  than  that  marked  a.  A  ther- 
mometer or  pyrometer  is  inserted  at  v,  while  t  serves 
as  exit  for  the  vapours,  which  are  condensed  in  a  coil 
surrounded  by  cold  water  in  the  case  of  the  first  pro- 
ducts and  by  hot  water  in  that  of  the  last  products  ; 
these  are  collected  in  order  of  density  in  a  number  of 
small  receivers,  from  which  they  are  passed  to  large 

J 

store-tanks.  The  stills  are  arranged  in  batteries  under 
light  roofs  open  at  the  sides  so  that  the  damage 
in  case  of  fire  or  explosion  may  be  minimised,  the 
further  precaution  being  taken  of  placing  the  fire 
hearths  outside  in  the  open.  When  the  products 

formed  at  270°  are  distilled  over,  the  yield  is  increased  and  the  pitch  rendered  more  liquid, 
and  so  prevented  from  charring,  by  introducing  a  current  of  superheated  steam,  this  remov- 
ing various  substances  (anthracene  oil)  which  would  otherwise  remain  in  the  pitch.  The 
latter  is  then  discharged,  while  hot,  into  old,  disused  steam  boilers  so  as  to  avoid  contact 
with  the  air,  which  might  ignite  the  mass  ;  when 
almost  cold  but  still  fluid,  it  is  run  into  shallow 
vessels  or  pits  dug  in  the  earth  and  allowed  to 
solidify.  With  a  still  holding  300  to  400  quintals, 
each  distillation  (including  charging  and  discharg- 
ing) lasts  about  4  days.  Distillation  in  a  vacuum 
saves  time  (less  than  30  hours  being  required  for 
200  quintals)  and  lessens  repairs. 

In  order  to  avoid  decomposition  of  the  pro- 
ducts distilling  'at  high  temperatures  and  to 
make  the  distillation  continuous  and  thus  increase 
the  output  and  economise  fuel,  Wernecke  (Ger. 
Pat.  201,372,  1907)  has  proposed  the  use  of  a 
conical,  stepped  still.  A,  fitted  with  a  number  of 
superposed  peripheral  channels,  E,  inside  (Fig. 
408).  The  cover,  B,  is  fitted  with  a  vapour 
outlet,  b,  and  a  pipe,  a,  for  the  continuous  intro- 
duction of  the  tar  (which  first  passes  through 
a  heater,  where  the  water  and  light  oils  are 
distilled).  The  latter  enters  the  uppermost 
channel,  E,  and  overflows  into  the  lower 

channels,  gradually  diminishing  in  volume  owing  to  the  distillation  of  various  products  ;  the 
more  or  less  liquid  pitch  is  discharged  at  d.  The  vapours  of  the  medium  oils  pass  through  the 
upper  orifice,  b,  to  refrigerators,  but  those  of  the  heavy  oils  from  the  lower  channels  are 
collected  by  the  perforated  pipe,  DF,  which  is  provided  with  a  cap,  G,  and  is  surrounded 
by  metal  gauze,  and  carries  them  through  c  to  refrigerators.  The  still  is  heated  by  the 

1  The  rapid  wear  of  the  iron  vessels  and  coils  is  due  especially  to  HO,  NH3,  H2S,  HCN",  &c.,  formed  by  the 
dissociation  at  high  temperatures  of  chlorides  (e.g.  ammonium  chloride,  dissociating  at  360°),  sulphides,  cyanides 
&c.,  and  perhaps  also  by  certain  electrolytic  processes.  The  base  of  the  still  is  often  18  to  20  mm.  in  thickness. 
Cast-iron  coils  last  better  than  those  of  wrought-iron,  and  are  composed  of  superposed  straight  tubes  connected 
at  alternate  ends  by  semicircular  pipes  of  cast-iron. 

II  34 


FIG.  408. 


530  ORGANIC    CHEMISTRY 

gases  from  the  hearth,  r,  which  circulate  in  the  flues,  e.  The  distillation  is  only  interrupted 
once  in  4  to  8  weeks  to  allow  of  the  removal  of  the  coke  deposited  on  the  inner  surface  of 
the  still.  Although  the  total  capacity  of  the  channels  is  only  600  kilos  of  tar,  the  daily 
output  is  equal  to  that  of  a  still  of  the  old  type  holding  2500  to  3000  kilos.  Such  a  still 
also  serves  well  for  the  distillation  of  lubricating  oils  from  petroleum  residues. 

In  order  to  prevent  the  tar  from  frothing,  it  is  necessary  first  to  free  it  from  water  as 
completely  as  possible.  This  is  done  by  maintaining  the  mass  in  open  vessels  for  some 
hours  at  40°  to  50°  or  by  adding  quicklime  or  gypsum  as  a  dehydrating  agent.1 

The  products  which  distil  below  110°  at  ordinary  pressure  (sp.  gr.  0-900  to  0-920)  are 
somewhat  similar  to  the  ammoniacal  liquor  of  gasworks,  and  consist  of  a  more  or  less 
coloured  liquid  on  which  floats  an  oil  containing  a  little  benzene  and  toluene. 

The  second  portion  which  is  collected  is  that  distilling  between  110°  and  210°,  this 
forming  the  so-called  light  tar-oils  (sp.  gr.  0-935  to  0-995). 

From  210°  to  240°  the  phenols  or  medium  oils  or  creosote  oils  are  collected.  The  next 
fraction  consists  of  heavy  oils  (up  to  270°  ;  sp.  gr.  1  to  1-040),  and  the  final  one,  the  anthra- 
cene oil,  passes  over  up  to  270°  (sp.  gr.  1-050  to  1-095)  and  forms  a  buttery  mass  composed 
of  oils  and  crystalline  substances. 

According  to  whether  the  pitch  (residue)  is  required  to  be  more  or  less  liquid  or  solid, 
the  distillation  is  suspended  after  the  third  or  fourth  fraction  has  been  collected  ;  to  render 
the  pitch  shiny,  it  is  mixed  in  the  still  with  the  heavy  oil  remaining  after  the  crystallisation 
of  the  anthracene.  This  oil  is  also  used  with  other  lubricants  for  making  oil -gas  (see  p.  57), 
lampblack,  &c. 

Anthracene  was  very  dear  until  a  few  years  ago,  and  to  obtain  the  maximum  yield  the 
heating  was  continued  under  reduced  pressure  after  the  distillation  in  superheated  steam. 

Tar  from  metallurgical  coke  manufacture  gives  distillation  products  differing  in  their 
proportions  from  those  of  coal-tar,  and  even  with  the  latter  the  tar  from  the  hydraulic 
main  (p.  43)  is  richer  in  pitch  and  .poorer  in  light  oils  than  the  tar  from  the  condensers 
and  separators.  The  tar  from  coke  factories  contains  more  light  oils  and  less  water  than 
that  from  gasworks,  and  distils  more  regularly  and  more  rapidly.2 

STATISTICS  AND  PRICES.  The  price  of  tar  varies  considerably  with  the  locality, 
quality,  season,  demand,  &c.,  the  limits  being  about  Is.  Id.  and  3s.  2d.  per  quintal.  In 
Germany  the  price  reached  the  maximum  of  4s.  Qd.  per  quintal  in  1885  and  fell  to  Is.  8d. 
in  1898  ;  it  now  varies  from  2s.  4d.  to  2s.  5d.  In  1900  the  world's  production  of  the  various 
distillation  products  of  tar  was  as  follows  :  50,000  tons  of  naphthalene,  24,000  of  benzene, 
and  6000  of  toluene.  One-half  of  this  output  comes  from  coke  factories  and  about  one- 
third  from  Germany.  In  1904  Germany  produced  277,000  tons  of  tar  in  metallurgical  coke 
factories  (in  1908  about  632,400  tons)  and  225,000  tons  in  lighting  gasworks  (in  1908  about 

1  The  separation  of  water  is  necessary  in  order  that  the  distillation  may  be  regular;  if -water,  is  present,  dis- 
tillation is  very  slow  and  is  accompanied  by  bumping  and  frothing.  When  a  sufficient  separation  cannot  be 
obtained  by  decantation  from  the  tepid  tar  after  standing,  special  methods  are  used.  According  to  Ger.  Pat. 
161,528  the  tar  in  the  still  is  heated  first  at  the  surface  and  subsequently  in  lower  and  lower  layers  to  the  bottom. 
Oppenheimer  and  Kant  remove  the  water  by  means  of  gypsum  or  cement  (Eng.  Pat.  12,696,  1903). 

By  centrifuging  the  tar  in  a  non-perforated  drum  (as  for  starch,  see  p.  498),  the  proportion  of  water  can  be 
reduced  to  1  to  2  per  cent.  In  large  distilleries  the  water  is  now  eliminated  by  passing  the  tar  from  elevated 
tanks  to  the  cooling  coils  in  which  the  vapours  of  the  tar  are  condensed  ;  the  tar  heated  in  this  way  to  50°  to 
60°  enters  a  small  rectifying  column  fitted  to  a  large  retort  (150  to  200  hcctols.)  almost  full  of  tar  already  heated 
to  200°  and  freed  from  water.  An  overflow  pipe  to  the  retort  delivers  tar  almost  without  water,  while  from  the 
top  of  the  column  issue  steam  and  a  considerable  proportion  of  the  light  oils,  which  are  condensed  in  cooling  coils. 

The  estimation  of  water  in  tar  is  not  easy,  since  when  the  tar  is  heated  in  a  dish  it  readily  froths  and  overflows. 
H.  Beck  and  llispler  (1909  and  1904)  allow  200  grins,  of  the  tar  to  fall  drop  by  drop  from  a  separating  funnel  on 
to  about  500  grms.  of  water-free  heavy  tar-oil'contained  in  a  flask  of  about  2  litres  ;  each  drop  of  tar,  as  it  falls, 
is  instantly  evaporated,  and  the  water  distilling  over  is  condensed  in  the  refrigerator  connected  with  the  flask 
and  collected,  together  with  a  little  tar-oil,  in  a  graduated  cylinder ;  the  temperature  is  finally  raised  to  300°. 
The  cylinder  is  kept  at  a  moderate  temperature,  so  that  the  water  separates  from  the  oil ;  its  volume  is  then 
read;  If  much  naphthalene  also  distils  over,  it  is  difficult  to  read  the  volume  of  the  water  ;  in  this  case,  the  whole 
of  the  distillate  is  poured  on  to  a  small  filter-paper  steeped  in  benzene,  so  that  only  the  tar-oil  filters.  The  filter- 
paper  is  subsequently  pierced  and  the  water  allowed  to  pass  into  a  graduated  cylinder.  E.  Ott,  on  the  other 
hand,  heats  400  grms.  of  tar  in  a  copper  retort,  the  heating  being  carried  out  from  the  top  by  means  of  an  annular 
gas-pipe  with  oriflees  in  its  lower  side. 

1  In  a  large  German  coke-tar  distillery,  where  retorts  holding  350  ^quintals  were  used,  the  mean  yields  of 
several  years  were  as  follows  :  Ammoniacal  liquor,  4-27  per  cent. ;  light"  oils,  4-06  ;  medium  oils,  10-38  ;  heavy 
oils,  6-11 ;  anthracene  oil,  13-71 ;  pitch,  60-49  ;  loss,  0-93.  The  tar  distilled  contained  on  an  average  24  per  cent, 
of  matter  (carbon)  insoluble  in  benzene,  and  the  mean  cost  of  distilling  1000  kilos  of  tar  was  as  follows  :  Labour, 
7-7d. ;  coal  (at  Is.  7d.  per  quintal),  14-4n! ;  steam,  <i-8d.  ;  various  materials,  l-4rf. ;  repairs,  3-8d. ;  depreciation 
11  -5<Z. ;  total,  43-6rf.  In  a  large  distillery  fitted  with  retorts  holding  180  quintals  and  working  at  reduced  pressure 
a  larger  annual  output  was  attained,  while  the  mean  cost  per  ton  distilled  was  36-5rf. ;  the  yields  were  as  follow  : 
Ammoniacal  liquor,  3-86  per  cent. ;  light  oils,  1-24 ;  medium  oils,  12-02 ;  heavy  oils,  8-50 ;  anthracene  oil, 


TAR-OILS 


531 


300,000  tons)  ;  in  1908  40,000  tons  of  tar  were  imported  from  England  (in  1909  only 
18,000  tons  were  imported,  while  35,000  tons  were  exported).  In  1909  9659  tons  of  lignite- 
tar  were  also  imported  and  3078  tons  exported,  the  total  production  (in  30  lignite  distil- 
leries) being  59,174  tons,  which  were  worked  up  in  12  tar  distilleries.  In  1908  75  works 
in  Germany  distilled  altogether  about  812,000  tons  of  tar  (three -fourths  from  cokeworks 
and  the  remainder  from  gasworks)  of  the  value  of  £944,000.  This  gave  products  worth 
about  £1,800,000,  namely  :  485,000  tons  of  pitch  (£650,000) ;  36,000  tons  of  naphthalene 
(£131,000)  ;  13,230  tons  of  crude  and  refined  benzene  (£110,000)  ;  248,000  tons  of  heavy 
tar-oils,  including  phenol,  creosote,  and  naphthalene  oils  (£500,000)  ;  2600  tons  of  crude 

18-68  ;  pitch,  54-56  ;  loss,  1-14.  When  tar  free  from  water  is  distilled,  the  consumption  of  coal  is  diminished 
from  7-5  to  5  per  cent. 

The  various  fractions  obtained  in  the  first  distillation  of  tar  are  treated  as  follow  : 

I.  The  Light  Oils  from  gas-tar  (A)  are  richer  in  benzene  and  toluene  than  those  from  coke-tar  (B),  as  is  shown 
by  the  following  moan  yields  obtained  on  fractional  distillation  of  these  oils  : 


Crude  benzene  I  (distilled  up  to  135°) 

„          ,,        II  (distilled  at  135°  to  165°) 
Phenol  oils  (165°  to  195°) 
Itesidue  (medium  oils)     .... 
Water  and  loss 


A 

36-12  % 
15-59  % 
18-01  % 
26-51  % 
3-67  % 


B 

12-66  % 
16-42  % 
18-47  % 
49-36  % 
3-09  % 


The  cost  of  distilling  100  kilos  of  light  oils  is  as  follows  :  7-7d.  for  labour,  19d.  for  fuel,  8-15rf.  for  steam,  4-8rf. 
for  repairs,  ami  Is.  for  depreciation. 

The  light  oils  are  distilled  and  rectified  in  a  column  apparatus  with  stills  holding  100  to  150  quintals  and 
heated  by  direct  fire  or  by  superheated  indirect  steam  ;  the  first  three  fractions  (up  to  195°)  arc  collected  separately. 
The  crude  benzenes  I  and  II  can  be  purified  from  the  small  amount  of  phenols  they  contain  by  washing  with 
caustic  soda  solution  ;  the  remaining  benzene  is  then  rectified  again  in  order  to  remove  the  toluene,  of  which 
it  may  contain  as  much  as  25  per  cent,  (see  later,  Benzene).  The  phenol  oils  (distilled  between  165°  and  195°) 
contain  appreciable  quantities  of  naphthalene,  and  are  therefore  worked  up  with  the  medium  oils. 

II.  The  Medium  Oils  (or  Creosote  Oils)  obtained  by  the  direct  distillation  of  gas-tar  contain  about  50  per 
cent,  of  naphthalene  and  as  much  as  25  per  cent,  of  acid  oils  (phenols),  which  hold  the  other  impurities  in  solution 
and  allow  of  a  more  ready  separation  of  a  purer,  crystalline  naphthalene  when  the  crude  creosote  oil  is  left  to  stand 
for  some  days  in  the  cold  ;  the  oil  is  then  drained  away  underneath  and  the  residual  naphthalene  centrifuged. 
The  medium  tar-oils  from  metallurgical  coke-tar  contain  about  43  per  cent,  of  naphthalene  and  only  13  per  cent, 
of  acid  oils,  so  that  many  impurities  arc  deposited  with  the  naphthalene  ;  instead  of  allowing  the  naphthalene 
to  crystallise,  it  is  therefore  preferable  to  subject  the  oil  directly  to  fractional  distillation,  pure  naphthalene  being 
more  readily  obtainable  from  the  products  : 


Medium  tar-oils 

Gas 

Metallurgical  coke 

Crude  benzene  II  (to  165°)        .         .         . 
I'hfiiol  oils  (165°  to  195°) 
Naphthalene  oil  (195°  to  220°) 
Jicsidue     .                          .... 
Water  and  loss        ..... 

4-15  % 
21-77  % 
43-45  % 
26-91  % 
3-72  % 

1-78  % 
19-91  % 
28-68  % 
48-18  % 
1-45  % 

The  residue  is  added  directly  to  the  heavy  tar-oils,  which  are  treated  separately  (see  beloir).  The  naphthalene 
oil  and  the  phenol  oil  are  cooled  so  as  to  separate  the  naphthalene  in  large  scales,  which  can  be  purified  by  hydraulic 
pressure.  The  residual  oil  which  drains  off  contains  the  greater  part  of  the  phenols,  which  are  extracted  by 
means  of  caustic  soda  (to  this  may  be  added  the  alkaline  solution  of  the  phenols  separated  from  the  crude  benzene), 
this  being  decanted  off,  treated  with  dilute  sulphuric  acid  to  liberate  the  crude  carbolic  acid  as  a  dense  black  liquid. 
After  repeated  purification  (by  dissolving  in  soda  and  precipitating  with  acitl)  or  distillation  between  175°  and 
185°,  purified  carbolic  acid  is  obtained.  This  is  crystallised  by  intense  cooling,  the  white  crystals  obtained  being 
freed  from  the  last  liquid  impurities  by  ccntrifugation  (for  the  complete  purification  of  phenol,  see  p.  541). 

If  the  phenols  are  not  extracted  from  the  creosote  oil.u,  the  latter  can  be  used  for  the  impregr.ation  and  pre- 
servation of  timber  (see  later). 

The  cost  of  working  the  medium  oils  is  about  the  same  as  for  light  oils  (see  above). 

From  the  residues  from  the  carbolic  acid,  i.e.  the  portions  insoluble  in  caustic  soda,  a  little  naphthalene  can 
be  recovered  by  distilling  them  with  other  medium  oils,  care  being  taken  to  warm  the  condensing  coils  so  as  to 
prevent  them  from  becoming  blocked.  The  purification  of  naphthalene  is  described  later.  England  exported 
34,558,053  gallons  (£464,828)  of  creosote  oil  in  1910  and  29,729,000  gallons  (£397,431)  in  1911,  while  the  United 
States  imported  42,608,000  gallons  in  1910  and  49,311,000  gallons  (£464,600)  in  1911. 

III.  The  Heavy  Oil  from  gas.-tar  contains  about  28  per  cent,  of  naphthalene  and  16  per  cent,  of  acid  (phenol) 
oils,  while  that  from  coke  factories  contains  about  32  per  cent,  of  naphthalene  and  10  per  cent,  of  acid  oils. 

Heavy  tar-oil,  when  not  redistilled  in  a  vacuum  to  recover  the  anthracene,  is  used  as  an  illuminant,  or  for 
the  manufacture  of  lighting  gas,  or  as  fuel,  or  for  impregnating  wood.  To  obtain  illuminating  gas  the  oil  is  run 
in  a  thin  stream  into  heated  iron  retorts  (as  in  the  cracking  of  petroleum,  see  p.  74),  carbon  and  an  oil  still  con- 
taining a  considerable  proportion  of  benzsne  being  formed  in  addition  to  the  lighting  gas. 

When  these  oils  are  used  directly  for  heating  purposes,  they  arc  pulverised  under  the  furnaces  by  means  of 
a  steam-jet  which  introduces  the  necessary  quantity  of  air. 

At  the  Deutz  gas-engine  works  (near  Cologne),  heavy  tar-oil  has  beeii  applied  in  Diesel  engines.    These  heavy 


532  ORGANIC    CHEMISTRY 

and  pure  naphthalene  oils  (£38,825)  ;  4020  tons  of  crude  and  purified  anthracene  (£32,000)  ; 
385  tons  of  pyridine  bases  (£12,680)  ;  1000  tons  of  crystallised  phenol  (£68,000)  ;  2080 
tons  of  cresols,  i.e.  90  to  95  per  cent,  carbolic  acid  (£19,440)  ;  4700  tons  of  xylol,  i.e. 
solvent  naphtha  and  heavy  benzene  (£39,600).  In  addition,  about  £40,000  worth  of 
ammoniacal  compounds  (1174  tons  of  ammonium  sulphate,  1050  tons  of  ammonia,  &c.) 
were  extracted. 

In  England  175,000  tons  of  tar  were  treated  in  1870,  about  400,000  tons  in  1880,  more 
than  640,000  tons  in  1886,  and  at  the  present  time  considerably  over  750,000  tons  per 
annum.  The  following  quantities  of  creosote  oil,  extracted  from  tar,  were  consumed  in 
England :  346,500  hectols.  in  1903,  389,250  in  1904,  609,750  in  1905,  and  2,520,000  in  1909, 
a  large  proportion  of  this  being  used  as  carbolineum  or  heavy  tar-oil  for  the  impregnation 
and  preservation  of  timber  and  railway  sleepers,1  and  for  the  disinfection  of  lavatories. 

France  produces  now  about  100,000  tons  of  tar  per  annum,  Belgium  about  80,000  tons, 
and  Holland  about  35,000  tons.  The  United  States  produced  280,000  tons  in  1904. 

oils  cost  in  bulk  about  4s.  per  quintal  and  have  a  calorific  value  of  about  8800  to  8900  Cals. ;  in,  e.g.  a  60  h.p. 
engine,  1  h.p.  hour  would  cost  about  l-25d. 

IV.  The  part  of  the  tar  distilling  above  270°  (Anthracene   Oil)  contains  the  greater  part  of  the  solid  anthra- 
cene, which,  after  prolonged  standing,  is  freed  from  the  liquid  impurities  by  hydraulic  presses  or  filter-presses. 
To  effect  more  complete  removal  of  the  liquid  arid  also  of  the  phenanthrene  accompanying  the  anthracene  crystals, 
the  latter  are  washed  with  benzine.     The  residue  represents  50  per  cent,  anthracene,  the  remainder  being  paraffins 
and  small  quantities  of  chrysene,  pyrene,  fluorene,  retene,  &c.     The  further  purification  of  the  anthracene  is 
described  later.     The  anthracene  oil  which  does  not  crystallise  either  serves  for  making  regenerated  tar  by  mixing 
With  pitch,  or  is  used  as  it  is,  under  the  name  carbolineum  (see  later),  for  preserving  wood. 

V.  As  already  indicated,  the  Pitch  remaining  in  the  retorts  is  removed  carefully  so  as  to  avoid  ignition.     After 
cooling  it  becomes  hard,   since  nowadays  the  anthracene  is  removed  as  completely  as  possible  ;   if  a  softer  pitch 
is  required,  it  is  mixed  with  a  suitable  proportion  of  waste  heavy  oils.     Pitches  from  different  tars  (wood,  lignite, 
coal,  &c.)  contain  different  amounts  of  phenols.     Pitch  is  used  in  place  of  natural  asphalte  and  is  improved  by 
melting  it  with  sulphur.     Mixed  with  sand,  it  is  used  as  asphalte  for  paving  roads,  for  making  bitumenised  paper, 
asphalte  pipes  (with  paper  and  sand),  briquettes  from  coal-dust,  and  black  varnish  for  sheet-iron  and  timber  (see 
also  Bitumen,  <fec.,  pp.  83  and  84). 

1  True  carbolineum  Avenarius,  patented  and  improved  (Ger.  Pat.  46,021  of  1888),  does  not  appear  to  contain 
creosote  oil,  naphthalene,  anthracene,  or  phenols.  To  render  it  more  dense  (sp.  gr.  1-2),  less  inflammable  and 
of  a  less  unpleasant  odour,  it  is  gently  heated  and  treated  with  a  current  of  chlorine  ;  it  contains  also  a  little  zinc 
chloride.  According  to  the  quality  the  price  varies  from  12«.  to  36s.  per  quintal. 

Preservation  of  Wood.  Timber,  railway  sleepers,  telegraph  poles,  &c.,  especially  when  in  contact  with 
the  ground,  are  injured  and  become  unusable  in  a  few  years  owing  to  the  attacks  of  various  moulds  and  micro- 
organisms (Merulius  lacrimans,  Potyporus  vaporarius,  &c.).  Even  when  hard  wood  is  used  it  gradually  becomes 
considerably  attacked.  Telegraph  poles  and  railway  sleepers  have  been  successfully  treated  by  smearing  with 
pitch  or  bitumen  the  parts  which  come  into  contact  with  the  earth,  and  superficial  charring  of  the  wood  at  the 
points  most  subject  to  attack  has  also  been  tried.  Formerly  much  use  was  made  of  the  method  of  mineralising 
wood.  Concentrated  and  more  or  less  hot  solutions  of  various  salts  (ferrous  or  copper  sulphate,  zinc  chloride,  &c.) 
are  forced  into  the  pores  of  the  wood  under  pressure ;  or  the  wood  is  heated  in  a  large  autoclave,  which  is  then 
evacuated  to  remove  all  the  air  and  water  from  the  pores  and  subsequently  filled  with  the  salt  solution,  which 
thus  impregnates  the  wood  completely.  But  the  process  which  gives  the  best  results  and  has  become  widely 
used  in  recent  years  is  that  of  Bethell,  which  consists  in  the  complete  impregnation  of  the  timber  with  heavy 
tar-oils  (crude  creosote  oil) ;  these  contain  phenols,  cresols,  &c.,  which  have  a  marked  disinfecting  action.  In 
Italy  this  process  has  been  applied  for  some  years,  and  is  carried  out,  not  in  autoclaves,  but  in  open  vessels,  such 
as  are  used  in  America,  the  treatment  being  completed  in  zinc  solutions  according  to  the  improvements  of  the 
Giussani  patents.  The  beams  are  first  immersed  for  5  to  6  hours  in  a  bath  of  fused  masut  (see  p.  74)  kept  at  160° 
to  170°,  by  which  means  the  "wood  is  deprived  of  its  air  and  water  and  sterilised  ;  they  are  then  passed  into  a 
cold  vessel  containing  medium  tar-oil  (the  portion  distilling  at  210°  to  240°  and  having  an  acidity  of  25  per  cent, 
due  to  various  phenols)  where,  after  20  to  30  minutes  cooling,  the  oil  penetrates  the  pores  to  a  depth  of  1  cm. 
or  more.  The  wood  is  finally  left  for  3  to  4  hours  in  a  cold,  concentrated  solution  of  zinc  chloride,  which  forces 
the  oil  further  in  and  forms  a  thin  superposed  layer  in  the  pores  (the  wood  absorbs  as  much  as  15  per  cent,  of 
the  zinc  chloride  solution).  Thus  treated,  wood  resists  the  action  of  weather,  water,  and  soil  for  15  to  20  years, 
soft  wood  being  as  resistant  as  hard. 

The  German  railways  require  that  every  sleeper,  2-7  X  0-26  X  0-16  metres,  shall  contain  7  kilos  of  creosote 
oil.  In  order  to  economise  tar-oil,  Euping's  process  is  often  used.  This  consists  in  creating  an  air  pressure  of 
5  atmos.  in  the  autoclave  containing  the  wood  and  then  introducing  the  creosote  oil  at  10  atmos.  pressure. 
When  the  pressure  in  the  autoclave  subsequently  falls  off,  the  excess  of  oil  is  forced  out  by  the  air  compressed 
in  the  pores,  the  latter  remaining  coated  inside  with  a  thin  layer  of  oil.  In  this  way  2  kilos  of  creosote  oil  give 
the  same  sterilising  effect.  Seidenschnur  (1909)  holds  that  the  phenolic  (acid)  components  of  the  creosote  oil 
are  unnecessary,  since  the  phenols  aie  not  antiseptic  in  solutions  of  oil ;  he  prefers  the  use  of  aqueous  emulsions 
containing  2  per  cent,  of  anthracene  oils  (which  are  devoid  of  phenols),  every  sleeper  containing  after  impreg- 
nation 0-8  kilos  of  anthracene  oil,  which  preserves  the  wood,  as  well  as  7  kilos  of  creosote  oil.  Good  results  have 
also  been  obtained  with  heavy  petroleum  oils  heated  to  200°  with  2  per  cent,  of  sulphur  and  then  mixed  with 
40  per  cent,  of  creosote  oil. 

According  to  Friedmann  and  Heidenstam,  wood  is  preserved  well  by  impregnating  it  with  calcium  cresolate 
(soluble  in  water)  and  then  precipitating  calcium  carbonate  and  cresol  jn  the  pores  by  simple  exposure  of  the 
wood  to  air  or,  better,  to  fumes  rich  in  carbon  dioxide  (Danish  Pat.  12,419  of  1909). 

For  the  Disinfection  and  Deodorisation  of  Urinals,  continuous  rinsing  with  water  may  be  replaced  with 
advantage  by  brushing  on  a  thin  layer  of  a  mixture  of  tar-oils  of  various  compositions  (heavy  tar-oils  mixed 
with  heavy  mineral  oil,  Ac.).  This  mixture  should  answer  the  following  requirements  :  sp.  gr.  0-990  at  most ; 
b.pt.  165°  at  least ;  it  should  remain  liquid  at  0°  and  should  not  separate  into  different  layers  on  standing ;  it 
should  not  contain  soap,  alcohols,  or  free  mineral  acids  ;  at  least  75  per  cent,  should  distil  at  350°  ;  it  should^ 
contain  at  least  7  per  cent,  of  cresol. 


BENZENE  533 

^Italy's  imports  and  exports  of  tar  are  as  follow  : 

1906      1907       1903       1909       1910 

Vegetable/Imports,  quintals       9600         16,600         16,110         15,045        21,825  (£21,826) 
tar       \Exports         „  367  722          1,051  1,857          1,061  (£1,061) 

Perkin  calculated  the  value  of  the  final  products  of  the  complete  and  rational  treatment 
of  9,000,000  tons  of  coal  (costing  £5,400,000)  to  be  as  follows  :  dyes,  £3,350,000  ;  ammo- 
nium sulphate  (195,000  tons),  £1,960,000  ;  pitch  (325,000  tons),  £365,000  ;  creosote  oil 
(1,125,000  hectols.),  £208,000  ;  crude  carbolic  acid  (45,000  hectols.),  £220,000  ;  coke, 
£2,400,000.  Total,  £8,503,000,  exclusive  of  the  30  cu.  metres  of  gas  per  ton  of  coal  car- 
bonised. 

BENZENE  (or  Benzol),  C6H6.  This  was  discovered  by  Faraday  in  1825 
in  the  liquid  obtained  on  compressing  illuminating  gas,  but  the  more  abundant 
source,  tar,  was  found  by  Hofmann  in  1845. 

It  is  obtained  pure  by  the  dry  distillation  of  benzoic  acid  with  lime,  and 
then  forms  a  colourless,  mobile,  highly  refractive  liquid  of  sp.  gr.  0-8841  at 
15°,  b.pt.  80-4°,  and  m.pt.  +  5-4°  ;  it  burns  with  a  luminous,  smoky  flame. 
The  commercial  product  contains  thiophene  and  traces  of  carbon  disulphide, 
which  can  be  eliminated  in  various  ways,  e.g.  with  moist  ammonia  (Schwalbe, 
Ger.  Pat.  133,761)  which  separates  insoluble  oil  drops,  or  with  boiling  mercuric 
acetate  or  sulphur  chloride  ;  according  to  Ger.  Pat.  211,239,  formaldehyde, 
acetaldehyde,  or  phthalic  anhydride  may  also  be  used,  all  these  substances 
combining  with  thiophene.  Benzene  dissolves  resins,  fats,  sulphur,  rubber, 
gutta-percha,  camphor,  &c.,  it  mixes  with  alcohol,  ether,  acetone,  &c.,  and  is 
almost  completely  insoluble  in  water. 

The  preparation  of  artificial  benzene,  starting  with  petroleum,  w,as  described 
on  p.  75.  Benzene  forms  the  prime  material  for  many  varied  syntheses  of 
aromatic  compounds,  such  as  nitrobenzene,  aniline,  &c.,  and  of  dyes  (also 
nowadays  of  artificial  indigo).  It  is  used  as  a  solvent  for  fats  and  for  purifying 
many  organic  compounds  ;  the  addition  of  15  per  cent,  of  benzene  to  the 
alcohol  used  with  an  Auer  mantle  for  lighting  purposes  results  in  a  saving 
of  27  per  cent,  of  the  alcohol.  Large  quantities  of  90  per  cent,  benzene  are 
now  used  for  carburetting  illuminating  gas  to  which  water-gas  has  been  added 
(see  p.  52).  It  is  also  employed  for  dissolving  rubber  and  lacs  for  making 
linoleum,  for  removing  fat  from  bones,  and  for  automobile  engines.1 

At  one  time  it  was  obtained  exclusively  from  gas-tar,  this  yielding  also  larger  quan- 
tities of  toluene,  the  uses  of  which  were  limited.  After  1880,  when  the  tendency  was  to 
obtain  increased  yields  of  illuminating  gas  by  raising  the  temperature  of  carbonisation  of 
the  coal,  the  quantity  of  tar  diminished,  as  also,  in  still  greater  proportion,  did  the  amount 
of  benzene.  In  1882,  the  price  of  benzene,  then  in  great  demand  by  dye  manufacturers, 
exceeded  £12  per  quintal.  It  was  then  that  attention  was  turned  to  the  recovery  of  the 
tar  from  metallurgical  coke  factories,  but  although  this  tar  is  obtainable  in  large  amounts, 
it  is  very  poor  in  benzene,  most  of  which  escapes  with  the  gases  and  is  wasted  in  the  com- 
bustion furnaces.  Darby  was  the  first  to  suggest  the  recovery  of  the  benzene  from  the 
gases  of  the  coke  furnaces  ;  and  nowadays  these  gases,  before  being  burnt,  are  either 
strongly  cooled  to  condense  the  benzene  or  washed  with  slightly  volatile  tar-oils,  in  which 
the  benzene  dissolves  and  from  which  it  is  recovered  by  subsequent  heating.2  As  a  result 

1  When  sufficiently  cheap,  it  may  replace  petroleum  benzine  in  engines.     But  it  requires  more  oxygen  (air) 
for  its  combustion,  and,  in  order  to  prevent  it  from  freezing  in  winter,  should  contain  a  little  toluene. 

2  The  manufacture  of   crude  benzene  from  tar  was  described  on  p.  529.     The  rectification  of  the  hydro- 
carbons contained  in  the  first  distillate  from  the  tar  (light  oils)  is  regulated  so  as  to  give  three  fractions  : 
(1)  commercial  90  per  cent,  benzene  I  of  sp.  gr.  0-885  at  15°  (90  per  cent,  of  this  distils  at  100°  and  100  per  cent, 
at  120° ;  it  contains  about  20  per  cent,  of  toluene ;  120°  is  termed  the  dry-point  of  the  benzene) ;  (2)  50  per  ctmt. 
benzene  II  with  sp.  gr.  0-880  (50  per  cent,  of  this  distils  at  100°  and  90  per  cent,  at  120°) ;   (3)  heavy  benzene  or 
solvent  naphtha  with  sp.  gr.  0-875  (20  per  cent,  of  this  distils  at  130°  and  90  per  cent,  at  160°  ;  it  serves  as  a  good 
solvent  for  rubber.) 

An  apparatus  suitable  for  the  rectification  of  crude  benzene  is  that  of  Hirzel  described  and  illustrated  on 
p.  76,  or  the  similar  one  of  Heckmann  shown  on  p.  140,  but  having  a  still  with  a  smaller  base  in  the  form  oE  a 
short  horizontal  cylinder.  From  the  90  per  cent,  benzene,  pure  benzene  can  be  obtained  by  further  rectification 


534  ORGANIC    CHEMISTRY 

of  this  process,  the  production  of  benzene  became,  more  than  ten  times  that  of  toluene, 
the  price,  which  was  £2  to  £3  per  quintal  in  the  period  1885-1896,  falling  to  20s.  to  24s. 
in  1898-1910.  Pure  thiophene-free  benzene  costs  about  Is.  Qd.  per  kilo  ;  the  puriss. 
product,  obtained  from  benzoic  acid,  is  sold  at  32s.  per  kilo. 

The  German  association  for  the  sale  of  products  of  distillation  of  coal  (ammonia,  &c.) 
sold  about  15,000  tons  of  benzene  in  1903  and  nearly  16,200  tons  (90  per  cent.)  in  1904. 
In  1870  Germany  produced  1200  tons  of  benzene,  in  1890  4500  tons,  in  1896  7000  tons, 
in  1901  28,000  tons,  and  in  1904  37,000  tons,  of  which  80  per  cent,  was  used  in  dyeworks 
and  about  10  per  cent,  in  the  manufacture  of  illuminating  gas.  England  exported  2,672,770 
gallons  of  benzene  and  toluene  in  1910  and  4,068,740  gallons  (£139,193)  in  1911. 

Italy  imported  the  following  quantities  of  benzene  (including  small  amounts  of  toluene 
and  xylene)  :  37  tons  in  1906,  430  in  1907,  463  in  1908,  636  in  1909,  600  tons  (£10,800) 
in  1910. 

TOLUENE  (or  Methylbenzene),C6H5-CH3,  is  formed  by  the  dry  distillation  of  balsam 
of  Tolu  and  of  various  resins,  and  is  obtained  in  appreciable  quantities  by  the  distillation 
of  tar  (see  above).  It  boils  at  110°,  does  not  solidify  even  at  —  28°,  and  has  the  sp.  gr. 
0-87  at  15°.  It  occurs  to  the  extent  of  10  to  15  per  cent,  in  crude  benzene  I  and  of  25  per 
cent,  or  more  in  crude  benzene  II. 

Crude  toluene  is  purified  from  the  hydrocarbons  of  the  fatty  series  which  always  accom- 
pany it  (and  are  not  eliminated  by  rectification)  by  washing  it  with  hot  sulphuric  acid 
containing  a  little  nitric  acid,  the  olefines  being  thus  polymerised  and  the  thiophene  decom- 
posed. It  may  also  be  purified  by  heating  with  sodium. 

Commercial  pure  toluene  gives  99  per  cent,  of  distillate  below  112°  and  95  per  cent, 
between  108°  and  110°  (two  drops  per  second).  It  does  not  colour  on  protracted  shaking 
with  concentrated  sulphuric  acid,  and  if  90  c.e.  of  toluene  and  10  c.c.  of  nitric  acid 
(44°  Be.)  are  shaken  together  for  some  minutes  in  a  tall  glass-stoppered  cylinder,  the 
nitric  acid  should  become  only  a  transparent  red  and  not  a  greenish  black  and  should 
not  thicken. 

Toluene  is  used  in  the  manufacture  of  dyes,  pharmaceutical  products,  perfumes,  &c., 
and,  during  recent  years,  of  trinitrotoluene  (see  later),  which  is  used  in  large  quantities  as 
an  explosive. 

The  pure  toluene  of  commerce  costs  in  Germany  about  36s.  per  quintal  for  large  quan- 
tities. 

XYLENES  (Dimethylbenzenes),  C6H4(CH3)2.  Xylene  obtained  from  tar  contains  the 
three  isomerides,  o-,  m-,  and  p-,  metaxylene  being  present  to  the  extent  of  70  to  80  per 
cent.  They  cannot  be  separated  by  fractional  distillation  owing  to  the  small  differences 
between  their  boiling-points  (o-  142°  ;  m-  139°  ;  p-  138°). 

Treatment  with  concentrated  sulphuric  acid  in  the  cold,  however,  converts  the  o-  and 
m-compounds  into  the  corresponding  sulphonic  acids,  the  p-xylene  remaining  unchanged. 
The  sodium  salt  of  o-toluenesulphonic  acid  crystallises  more  readily  than  that  of  the 
m-compound,  so  that  the  three  hydrocarbons  can  be  separated.  With  oxidising  agents, 
the  xylenes  give  phthalic  acids  (see  later). 

It  is  mostly  m-xylene  which  is  used  in  the  manufacture  of  dyes,  and  the  commercial 
product  costs  about  £7  8s.  per  quintal  ;  chemically  pure  m-xylene  is  sold  at  14s.  per  kilo 
(chemically  pure  o-xylene  costs  72s.  per  kilo  and  the  p-compound  40s.). 

ETHYLBENZENE,  C6H5-C2H5,  is  obtained  by  Fittig's  synthesis  (see  p.  526)  and 
gives  benzoic  acid  on  oxidation  (difference  from  the  xylenes). 

and  freezing,  the  mass  of  benzene  crystals  being  pressed  and  centrifuged  to  remove  the  liquid  toluene  and  higher 
homologues. 

Commercial  benzene  obtained  from  coke-furnace  gases  contains  85  per  cent,  of  benzene,  11-7  per  cent,  of  toluene, 
1-4  per  cent,  of  xylene,  and  1-87  per  cent,  of  naphthalene  and  other  products.  Gas-tar  gives  less  than  1-5  per 
cent,  of  benzene  and  toluene  together,  most  of  these  products  (93  per  cent,  of  the  amount  obtained  on  distilling 
coal)  remaining  in  the  gas  (as  much  as  45  grms.  per  cu.  metre  ;  the  gases  from  metallurgical  coke  contain  only 
20  grms.).  Every  ton  of  Westphalian  coal  converted  into  coke  yields  about  4  kilos  of  benzene  and  0-9  kilo  of 
toluene  ;  other  coals  give  only  about  1-5  kilos  of  these  two  products  together. 

The  testing  of  commercial  benzene  is  carried  out  by  determining  its  density  and  by  fractionally  distilling  it ; 
100  c.c.  are  distilled  in  an  ordinary  flask  with  a  side-tube  (see  p.  3)  and  heated  on  a  metal  gauzs  with  a  flame  so 
adjusted  that  two  drops  distil  over  per  second  ;  the  flame  is  removed  for  a  minute  before  changing  the  cylinders 
in  which  the  separate  fractions  (100°,  120°,  130°,  160°)  are  collected.  In  some  cases  a  nitration  test  is  made, 
note  being  taken  of  the  yield  of  nitrobenzene,  purified  by  steam,  and  then  rectified  (see  later,  Nitrobenzene).  The 
addition  of  petroleum  spirit  to  benzsne  is  detected  by  the  lowering  of  the  density ;  also  petroleum  spirit  does 
not  dissolve  tar-pitch  or  picric  acid,  which  are  readily  soluble  in  benzene.  Further,  the  latter  reacts  vigorously 
with  concentrated  nitric  acid,  which  does  not  attack  petroleum  spirit. 


METHYLBENZENES  535 

TRIMETHYLBENZENES,  C6H3(CH3)3  (see  Table,  p.  527).    The  following  isomerides 
are  known  : 

(a)  Mesitylene  (symm.  1  :  3  :  5-)  is  a  liquid  of  pleasant  odour  boiling  at  165°.     Its 
constitution  is  proved  by  its  synthesis  from  acetone  or  allylene,  by  the  fact  that  it  does 
not  form  isomeric  compounds  by  further  substitution  in  the  nucleus,  and  by  its  oxidation 
products  :   nitric  acid  oxidises  the  three  side-chains  successively  and  chromic  acid  simul- 
taneously. 

(b)  Pseudocumene  (asymm.  1  :  2  :  4-)  is  prepared  from  bromo-p-xylene  (1:4:2)  or 
bromo-m-xylene  (1:3:  4)  by  Fittig's  synthesis,  which  indicates  its  constitution.     It  is 
obtained  in  small  proportion  from  the  distillation  products  of  tar,  and  is  separated  from 
mesitylene  by  conversion  into  the  slightly  soluble  sulphonic  acid  (see  Xylenes). 

(c)  n-Propylbenzene,   C6H5-CH2-CH2-CH3.     The  constitution  of  this  compound  is 
shown  by  the  facts  that  it  yields  benzoic  acid  when  oxidised  and  that  it  is  obtained  syn- 
thetically (Fittig)  from    propyl    iodide    and    bromobenzene    or    from  benzyl  chloride, 
C6H5-CH2C1,  and  zinc  ethyl. 

(d)  Isopropylbenzene  (or  cumene),  <^  J> — CH(CH3)2,  also    gives    benzoic    acid 


on  oxidation,  and  is  formed  from  benzene  with  either  isopropyl  iodide  or  normal  propyl 
iodide  (in  the  latter  case  aluminium  chloride  is  necessary  to  cause  molecular  rearrange- 
ment) ;  it  is  obtained  also  on  distilling  cuminic  acid,  C6H4(C3H7)-C02H,  or  by  the  inter- 
action of  benzal  chloride,  C6H5-CHCI2,  and  zinc  methyl. 

TETRAMETHYLBENZENES,  C6H2(CH3)4.     The  best  known  of  these  are  the  fol- 
lowing : 

(a)  Durene  (1:2:4:5)    or    s-tetramethyl benzene,    which   is   found,    together   with 
isodurene,  in  tar ;  it  is  a  solid,  has  a  smell  resembling  that  of  camphor,  and  is  prepared 
synthetically  from  toluene  and  methyl  chloride. 

(b)  and  (c)  Isodurenes,  two  isomerides  being  known  (1:2:3:4  and  1:2:3:5)  (see 
Table,  p.  527). 

(d)  p-Methylisopropylbenzene  or  cymene,  CH3<^  ^> — CH(CH3)2,   is  a  liquid  of 


pleasant  odour,  b.pt.  185°.  It  occurs  naturally  in  cumin  oil  (from  Cuminum  cyminum)  and 
in  various  essential  esters,  and  it  can  be  prepared  by  heating  camphor  with  phosphoric 
anhydride  or  by  the  interaction  of  oil  of  turpentine  and  iodine.  On  oxidation  it  yields 
various  acids. 

(e)  m-Isocymene  is  found  in  resin  oil. 

Hexamethylbenzene  (mellithene),  C6(CH3)6,  m.pt.  164°,  is  a  stable  compound  and  can 
be  neither  nitrated  nor  sulphonated,  owing  to  the  absence  of  hydrogen  atoms  from  the 
nucleus.  When  oxidised  with  potassium  permanganate,  it  gives  Mellitic  Acid,  C6(C02H)6. 

HYDROCARBONS  WITH  UNSATURATED  SIDE-CHAINS 

As  far  as  the  nucleus  is  concerned,  these  compounds  behave  like  true  benzene  deriva- 
tives, whilst  by  means  of  the  unsaturated  side-chain  they  give  all  the  reactions  of 
unsaturated  methane  derivatives. 

STYRENE,  C6H5-CH  :  CH2,  occurs  in  storax  and  is  formed  on  heating  cinnamic  acid, 
which  loses  CO2  :— C6H5  •  CH  :  CH  •  CO2H  =  C02  +  C6H5-CH:CH2.  It  is  a  liquid  of 
pleasant  odour  boiling  at  146°,  and  tends  to  polymerise  to  Metastyrene.  Styrene  combines 
with  bromine,  iodine,  hydrogen,  &c.,  in  the  same  way  as  olefines  do.  When  it  is  treated 
with  nitric  acid,  a  nitro -group  is  introduced  into  the  side- chain,  giving  Nitrostyrene, 
C6H5-CH  :  CH*N02,  the  constitution  of  this  being  shown  by  its  formation  from  benzal- 
dehyde  and  nitromethane  :  C6H5-CHO  +  CH3-N02  =  C6H5-CH  :  CH-N02  +  H20. 

Styrene  serves  for  the  synthesis  of  anthracene  (q.v.). 

PHENYLACETYLENE,  C6H5-C  :  CH,  is  a  liquid  of  pleasant  odour  boiling  at  142°, 
and  is  prepared  by  converting  acetophenone,  C6H5'COCH3,  by  means  of  PC16,  into  the 
dichloro -derivative,  C6H5-  CC12-CH3,  and  eliminating  2HC1  from  the  latter  by  the  action 
of  potassium  hydroxide. 

It  is  also  obtained  by  the  cautious  distillation  of  Phenylpropiolic  Acid,  C6H6-C  i  OC02H. 
Like  acetylene,  it  forms  metallic  compounds  ;  treatment  with  concentrated  sulphuric  acid 
results  in  the  addition  of  H20,  subsequent  dilution  with  water  giving  acetophenone. 


536  ORGANIC    CHEMISTRY 

B.  HALOGEN  SUBSTITUTION  PRODUCTS  OF  BENZENE 

Halogens  act  on  benzene  and  its  homologues,  replacing  one  or  more  atoms 
of  hydrogen  and  forming  colourless  liquids  (sometimes  crystalline  substances) 
which  are  heavier  than  water,  distil  unchanged,  and  dissolve  in  alcohol  and  in 
ether. 

In  aromatic  hydrocarbons,  a  halogen  in  the  benzene  nucleus  is  held  much 
more  firmly  than  one  in  a  side-chain  and  cannot  be  replaced  by  hydroxyl 
by  the  action  of  silver  hydroxide  or  by  the  ammo-group  by  treatment  with 
ammonia  ;  only  by  sodium  or  sodium  alkoxide  at  about  200°  can  the  halogen 
be  eliminated.  . 

The  chlorine  in  the  nucleus  of  chloro  toluene  is  united  as  firmly  as  in  chloro- 
benzene,  whilst  the  chlorine  in  benzyl  chloride  is  readily  replaceable,  just 
as  is  the  case  with  that  in  methane  derivatives.  To  ascertain  whether  the 
halogen  is  present  in  the  nucleus  or  in  the  side-chain,  the  oxidation  products 
are  studied;  thus,  chlorotoluene  gives  chlorobenzoic  acid,  C6H4C1-C02H, 
whilst  benzyl  chloride  yields  benzoic  acid. 

*•      For  distinguishing  isomeric  halogen  derivatives,   the  same  methods  are 
used  as  for  the  xylenes,  &c. 

In  order  to  be  able  to  name  aromatic  derivatives  the  more  readily,  the 
following  names  are  given  to  the  more  common  of  the  different  groups  or 
aromatic  residues  (known  as  aryl  radicals  and  denoted  generally  by  Ar)  : 
—OH,  phenolic  ;  —  C02H,  carboxyl  ;  —  0-CH3,  methoxy  ;  —  C6H5,  phenyl  ; 
-CH2-  C6H5,  benzyl  ;  -CO-C6H5,  benzoyl  ;  -CN,  nitrile  ;  -S03H,  sulpho 

C  ~ 
or  sulphonic;    —  C-C6H5,  benzenyl;    C6H4</>>0,  phthalyl  ;     —  CH-C6H5, 


benzylidene  or  benzal  ;    —  C6H4-C6H4—  ,  diphenylene. 

General  Methods  of  Formation.  (1)  In  direct  sunlight,  chlorine  and  bromine 
act  on  benzene,  giving  additive  products,  e.g.  C6H6C16  and  C6H6Br6,  but  in 
diffused  light  (best  in  presence  of  traces  of  iodine,  aluminium  chloride,  anti- 
mony trichloride,  &c.),  substitution  products  are  formed.  With  homologues  of 
benzene,  if  the  reaction  is  carried  out  in  the  cold  and  in  the  dark  (or  in  diffused 
light)  or  in  presence  of  iodine  (which  acts  catalytically),  the  halogen  only  enters 
the  benzene  ring  (even  in  the  hot,  if  iodine  is  present),  whilst  in  the  hot  or 
in  direct  sunlight,  the  substitution  takes  place  principally  in  the  side-chain. 

(2)  By  heating  halogenated  acids  with  lime  : 

C6H4C1-C02H  =  C6H5C1  +  C02. 

(3)  By    withdrawing    oxygen    from    oxygenated    compounds     (phenols, 
aromatic    alcohols,    ketones,    acids,    aldehydes)    by    means    of    PC15  ;     e.g. 
C6H5-OH  +  PC15  =  POC13  +  HC1  +  C6H5C1. 

(4)  By   boiling    with   cuprous   chloride    or   potassium   iodide    the    diazo- 
compounds   obtained  from   the   corresponding  nitro-   or  amino-compounds  : 
C6H5N  :  NCI  =  C6H5C1  +  N2  ;   C6H5N  :  NCI  +  KI  =  KC1  +  N2  +  C6H5I. 

(5)  lodo-derivatives  may  be  obtained  by  the  action  of  iodine,  iodic  acid 
being  added  to  oxidise  the  hydriodic  acid  which  is  formed.     They  are,  how- 
ever, usually  obtained  by  process  (4). 

(6)  lodobenzene,  C6H5I,  unites  with  two  atoms  of  chlorine,  forming  iodoso- 
benzene  chloride,  C6H5IC12,  digestion  of  which  with  alkali  yields  iodosobenzene, 
C6H51  :  0,  the  latter,  when  heated  or  oxidised  (with  chloride  of  lime)  giving 
iodylbenzene,   2C6H5IO  =  C6H5I  +  C6H5I02  or  C6H5IO  +  0  =  C6H5I02    (an 
explosive,  crystalline  compound). 

Chlorination  or  bromination  of  toluene  yields  the  para-  and  ortho-derivatives 
in  equal  quantities  ;  the  me  ta  -derivative  is  obtained  indirectly  (from  diazO- 
compounds). 


HALOGENATED  BENZENE  COMPOUNDS  537 

PRINCIPAL  HALOGEN  DERIVATIVES  OF  BENZENE 


Empirical 
formula 

Name 

Melting- 
point 

Boiling- 
point 

Specific 
gravity 

Chloro-derivatives 

C6H5C1 

Monochloro  benzene 

—  42° 

+  132° 

1-1  28  at  0° 

C6H4C12        . 

o-Dichloro  benzene  (1:2)      .          . 

— 

179° 

m-              „              (1:3). 

— 

172° 

•P-                „               (1:4)      ... 

+  53° 

172° 

C6H3CI3        *  . 

v-Trichloro  benzene  (1:2:3) 

16° 

218° 

as-              „                (1:2:4) 

63° 

213° 

s-                „                (1:3:5) 

54° 

208° 

C6H2C14         . 

v-Tetrachloro  benzene  (1  :  2  :  3  :  4) 

46° 

254° 

as-                  „                (1:2:3:  5) 

50° 

246° 

(1:2:4:5) 

137° 

244° 

C6HC15 

Pentachlorobenzene     .          . 

86° 

276° 

CgClg    .         •, 

Hexachlorobenzene      .          .          . 

226° 

326° 

Bromo-derivatives 

C6H5Br 

Monobronio  benzene     .          . 

-  31° 

+  155° 

1-51  7  at  0° 

C6H4Br2 

o-Dibromo  benzene  (1:2) 

—  1° 

224° 

2-003  at  0° 

m-               „               (1:3)      . 

+  1° 

220° 

1-955  at  20° 

P-                                (1:4)      . 

87° 

219° 

1-841  at  89° 

C6H3Br3        . 

r-Tribromobenzene  (1:2:3) 

87° 

— 

as-               „                 (1:2:4) 

44° 

275° 

s-                 „                (1:3:5) 

120° 

278° 

C6H2Br4        . 

v-Tetrabro  mo  benzene  (1:2:3:4) 

— 

— 

as-                 „                   (1:2:3:  5) 

98° 

329° 

(1:2:4:5) 

175° 

— 

C6Br6  . 

Hexabromobenzene     .          . 

above315° 

— 

C6H4Br-CH3 

o-Bro  mo  toluene  (1:2) 

-26° 

181° 

1-422  at  20° 

m-            „            (1:3)          .          . 

-  39-8° 

184° 

1-410  at  20° 

P-              „            (1  :  4) 

+  28° 

185° 

1-392  at  20° 

C6H5-CH2Br 

Benzyl  bromide            .          * 

liquid 

198° 

1-438  at  22° 

lodo  -derivatives 

C6H5I 

lodobenzene       •»         .         ..-•• 

-  30° 

188° 

CeH^ 

o-Di-iodobenzene  (1:2)        -, 

+  27° 

286° 

m-            „              (1:3)        .. 

40° 

285° 

P-             „              (1:4)        . 

129° 

285° 

BENZYL  CHLORIDE,  C6H5-CH2C1,  is  a  colourless  liquid  with  a  pungent  odour, 
melting  at  —  49°  and  boiling  at  178°  ;  its  specific  gravity  at  15°  is  1-113.  It  was  first 
prepared  by  Cannizzaro  in  1853,  and  is  obtained  by  chlorinating  boiling  toluene.  With 
potassium  acetate  this  chloride  gives  the  acetyl-derivative,  with  potassium  hydrosulphide 
a  mercaptan,  and  with  ammonia  amino-bases.  On  protracted  boiling  with  water  it  is 
transformed  into  benzyl  alcohol,  while  boiling  with  lead  nitrate  converts  it  into  benzalde- 
hyde  ;  when  heated  with  finely  divided  copper,  it  loses  chlorine  and  condenses  to  dibenzyl, 
C6H5  •  CH2  •  CH2  •  C6H5. 

It  is  used  for  the  preparation  of  oil  of  bitter  almonds  and  for  numerous  aromatic  syn- 
theses, its  chlorine  atom  being  readily  replaceable. 

The  commercial  product  costs  3s.  5d.  per  kilo  and  the  chemically  pure  5s.  Id. 

Benzyl  Bromide,  when  treated  with  potassium  iodide,  gives  Benzyl  Iodide.  These 
products  are  also  formed  from  benzyl  alcohol,  C6H5'CH2-OH,  and  halogen  hydracids  ; 
they  may  be  converted  back  into  the  alcohol  by  boiling  with  water  or  potassium 
carbonate  solution. 


538  ORGANIC    CHEMISTRY 

BENZAL  CHLORIDE,  C6H5-CHC12,  and  Benzotrichloride,  C6H5-CC13,  are  obtained 
either  by  protracted  chlorination  of  boiling  toluene  or  by  the  action  of  PC15  or  benzal- 
dehyds  or  benzoic  acid. 

Benzal  chloride  boils  at  204°  and  has  the  sp.  gr.  1-295  at  16°,  while  the  trichloride  melts 
at  -  22°,  boils  at  213°,  and  has  the  sp.  gr.  1-380  at  14°. 

Mixed  halogen  derivatives  are  known,  as  also  is  Hexachlorohexahydrobenzene, 
C6H6C16.  Numerous  halogenated  derivatives  of  unsaturated  aromatic  hydrocarbons  have 
likewise  been  prepared,  e.g.  o-Bromostyrene,  C6H5-CBr :  CH2,  and  /3-Bromostyrene, 
C6H5-CH:CHBr. 

C.  SULPHONIC  ACIDS 

These  are  formed  directly  from  the  aromatic  hydrocarbons  by  the  action 
of  concentrated  or  fuming  sulphuric  acid  or  of  chlorosulphonic  acid,  C1-S03H. 
Improved  yields  are  obtained  in  presence  of  mercury  or  ferrous  sulphate, 
which  exerts  a  catalytic  action. 

They  are  crystalline  substances,  readily  soluble  in  water  and  even  hygro- 
scopic, and  are  separated  from  the  excess  of  sulphuric  acid  either  by  means 
of  their  calcium  or  barium  salts,  which  are  soluble,  or  by  saturation  of  the 
aqueous  solution  with  sodium  chloride  and  subsequent  cooling  ;  in  the  latter 
case,  the  sodium  sulphonate  separates,  this  being  decomposed  with  the  calcu- 
lated quantity  of  a  mineral  acid  and  the  free  sulphonic  acid  extracted  with 
ether. 

When  treated  with  superheated  steam  or  with  hydrochloric  acid,  they 
lose  the  sulphonic  group,  the  aromatic  hydrocarbon  being  thus  regenerated. 
With  PC15  they  form  the  acid  chlorides,  e.g.  C6H5-  S02C1,  which,  with  ammonium 
carbonate,  yield  the  sulphamides,  C6H5-S02-NH2  (see  later).  On  energetic 
reduction,  thiophenol  (phenyl  hydrosulphide),  C6H5-SH,  is  formed. 

BENZENESULPHONIC  ACID,  C6H5-S03H,  is  obtained  by  the  direct  action  of  con- 
centrated sulphuric  acid  on  benzene :  C6H6  +  H2S04  =  H2O  +  C6H5-S03H.  Its  barium 
and  lead  salts  being  soluble,  it  can  be  readily  separated  from  the  excess  of  sulphuric 
acid. 

It  is  very  stable  and  is  not  decomposed  on  boiling  with  alkali  or  acid  (as  is  ethylsulphonic 
acid),  but  if  heated  with  hydrochloric  acid  at  150°  or  with  superheated  steam  in  presence 
of  concentrated  phosphoric  acid,  it  takes  up  water,  giving  benzene  :  C6H5  •  S03H  +  H2O  = 
C6H6  +  H2S04.  When  distilled  with  potassium  cyanide,  it  forms  benzonitrile,  C6HB  •  S03K 
+  KCN  =  K2S03  +  C6H6-CN. 

When  fused  with  alkali  it  forms  phenol,  C6H5-S03K  +  KOH  =  K2S03  +  C6H5-OH, 
while  with  PC15  it  yields  Benzene  Sulphochloride,  C6H5-S03H  +  PC15  =  POC13  +  HC1  + 
C6H5-S02C1  (decomposable  by  water). 

With  ammonia,  ammonium  carbonate,  or  primary  or  secondary  amines,  benzene 
sulphochloride  gives  more  or  less  substituted  Benzenesulphonamides,  e.g.  C6H5-S02'NH2, 
C6H5-S02-NHR,  C6H6-S02-NR2,  which  crystallise  well.  As  the  tertiary  amines  do  not 
give  this  reaction,  they  can  be  separated  from  other  amines. 

Owing  to  the  highly  acid  character  of  the  SO2  group,  the  amino-group  does  not  form 
salts,  but  its  hydrogen  can  be  replaced  by  metals,  e.g.  by  dissolving  in  sodium  hydroxide 
solution.  Sulphur  trioxide  concerts  benzene  into  Sulphobenzide  (sulphone),  (C6H5)2SO2. 

Nitration  of  benzenesulphonic  acid  yields  mainly  m-nitrobenzenesulphonic  acid,  but 
small  quantities  of  the  ortho-  and  para -derivatives  are  also  formed. 

Reduction  of  p-nitrobenzenesulphonic  acid  yields  Sulphanilic  Acid  (p-aminobenzene- 
sulphonic  acid),  NH2'C6H4-S03H  (discovered  by  Gerhardt  in  1845),  which  is  also  obtained 
on  heating  aniline  with  fuming  sulphuric  acid  or  on  heating  aniline  sulphate  at  200°.  This 
acid  and  also  the  corresponding  meta-acid  are  used  in  the  manufacture  of  artificial  dye- 
stuffs,  and  both  of  them  can  be  diazotised  (see  later). 

Sulphonic  compounds  and  their  salts  are  of  importance  in  the  dye  industry  as 

they  give  dyes  soluble  in  water  and  readily  applied  to  the  dyeing  of  textile  fabrics. 

Polysulphonic  acids  of  benzene  and  its  homologues  are  also  known,  some 


PHENOLS  530 

of  them  serving  for  the  separation  of  isomeric  aromatic  hydrocarbons  (see 
Toluene). 

D.  PHENOLS 

Phenols  contain  hydroxyl  groups  in  place  of  one  or  more  hydrogen  atoms 
of  the  benzene  nucleus.  They  have  a  characteristic  odour  (phenol,  thymol), 
and  certain  of  them  are  partially  soluble  in  water,  while  all  of  them  are  soluble 
in  alcohol  and  in  ether  ;  they  distil  unchanged  and  have  a  more  or  less  marked 
antiseptic  action. 

Their  properties  resemble,  to  some  extent,  those  of  tertiary  alcohols  and 
those  of  weak  acids.  Thus,  ethers  are  formed  by  the  action  of  alkyl  halogen 
compounds  on  the  sodium  derivatives  of  the  phenols,  anisole,  C6H5-  OCH3, 
and  phenyl  sulphate,  CgHg-O-SOgH,  being  obtained  in  this  way  ;  the  latter 
compound  is  readily  hydrolysed.  They  are,  however,  stable  towards  oxidising 
agents,  nitric  acid  forming  substitution  products.  The  hydroxyl  group  is 
with  some  difficulty  replaced  by  chlorine  by  the  action  of  PC15.  They  act  as 
weak  acids,  but  with  alkalis  form  stable  salts,  which  are  soluble  in  water,  are 
decomposed  even  by  carbonic  acid,-and  show  only  slight  electrical  conductivity. 

Halogens  and  nitric  acid  replace  the  benzene  hydrogen  of  phenols  more 
easily  than  that  of  benzene  itself  or  its  homologues,  so  that  even  in  dilute 
solution  phenol  can  be  precipitated  quantitatively  as  tribromophenol  by  the 
action  of  bromine  water. 

If  the  hydroxyl  group  is  joined  to  a  side-chain  and  not  to  the  benzene 
nucleus  directly,  the  compound  is  an  aromatic  alcohol  and  not  a  phenol. 

Oxidation  of  homologues  of  phenol  yields  hydroxy-acids,  the  side-chain 
being  oxidised  while  the  phenolic  groups  remain  intact. 

When  distilled  with  zinc  dust,  phenols  give  the  corresponding  aromatic 
hydrocarbons. 

In  aqueous  neutral  solution,  phenols  give  a  violet,  green,  or  other  coloration 
with  ferric  chloride,  calcium  hypochlorite,  or,  in  some  cases,  iodine.  In 
general,  they  exert  a  reducing  action. 

With  nitrous  acid,  phenols  form  isonitroso-derivatives  (oximes),  and,  in 
presence  of  concentrated  sulphuric  acid,  intensely  coloured  solutions  are 
formed  which  are  turned  blue  by  potash  (Liebermanris  reaction).  The  sodium 
or  potassium  derivatives  of  the  phenols  (phenoxides),  with  carbonic  acid  (or 
(CC14  +  KOH)  give  aromatic  hydroxy-acids  : 

~C6H5-OH  +  C02  =  OH-C6H4-C02H. 

With  chloroform  and  sodium  hydroxide,  they  yield  the  corresponding  alde- 
hydes. 

They  react  with  diazo-compounds  and  various  other  compounds  forming 
colouring-matters  (see  later).  The  action  of  zinc  chloride  (or  calcium  chloride) 
and  ammonia  on  phenols  results  in  replacement  of  the  OH  by  NH2. 

(a)  MONOHYDRIC    PHENOLS 

These  are  found  alone  or  together  with  polyhydric  phenols,  and  partly 
in  the  form  of  ethers  (e.g.  guaiacol,  OH-C6H4- OCH3,  cresol,  &c.)  in  the  tar 
obtained  by  the  dry  distillation  of  wood  or  coal.  They  are  separated  from 
the  tar-oils  by  means  of  caustic  soda,  which  renders  them  soluble,  and,  after 
separation,  are  set  free  by  mineral  acid  and  subjected  to  fractional  distillation. 

They  are  also  obtained  industrially  by  fusing  salts  of  sulphonic  acids  with 
alkali  (in  iron  vessels  ;  in  the  laboratory  silver  vessels  are  used)  : 

C6H5-S03K  +  2KOH  =  C6H5-OK  +  K2S04  +  H20. 

If  the  nucleus  contains  chlorine  atoms,  these  are  also  substituted  by  hydroxyl 
groups  by  this  reaction. 


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CARBOLICACID  541 

Phenols  are  formed  by  boiling  diazo-compounds  (see  later)  with  water  in 
dilute  sulphuric  acid  solution  : 

C8H5-N2C1  +  H20  =  N2  +  HC1  +  C6H5-  OH. 

Also,  when  benzene  is  oxidised  with  H202  or  with  oxygen  in  presence  of 
aluminium  chloride,  phenols  are  obtained. 

Chlorine  atoms  or  amino-groups  joined  directly  to  the  nucleus  can  be 
replaced  by  hydroxyl-groups  by  the  action  of  sodium  hydroxide,  but  only 
when  the  nucleus  contains  also  strongly  negative  groups,  e.g.  N02. 

PHENOL  (Carbolic  Acid),  C6H5- OH,  was  first  discovered  byRunge  in  tar  and  occurs, 
to  a  small  extent,  in  combination  in  urine. 

It  is  separated  from  tar-oils  (see  p.  530)  by  treatment  with  caustic  soda  solution  (sp.  gr. 
1-09)  and  agitation  by  a  current  of  air  ;  steam  is  passed  through  the  decanted  alkaline 
solution  of  phenol,  this  removing  the  naphthalene,  &c.  The  phenol  is  then  liberated  by 
H2S04  or  CO2  (e.g.  flue  gases)  and  washed  several  times  with  water,  crude  carbolic  acid 
(containing  40  per  cent,  of  phenol,  the  rest  creosote,  &c.)  of  sp.  gr.  1-05  to  1-06  being  thus 
obtained.1 

This  is  purified  by  repeated  distillation  between  175°  and  185°  or,  better,  rectification 
until  it  crystallises  at  the  ordinary  temperature  and  no  longer  turns  red  in  the  air.  To  free 
it  from  final  traces  of  cresol,  it  is  diluted  with  12  to  15  per  cent,  of  water  and  the  hydrate 
crystallised  at  —8°  to  —  10°  (cresol  hydrate  crystallises  at  20°),  centrifuged  and  distilled 
until  a  strength  of  99  per  cent,  is  attained  ;  repetition  of  the  operation  and  of  the  distilla- 
tion (in  earthenware  vessels)  gives  chemically  pure  phenol.  Minimal  quantities  of  water 
prevent  crystallisation  at  the  ordinary  temperature. 

The  low  price  of  benzene  renders  practicable  the  industrial  synthesis  of  phenol  ;  by 
means  of  fuming  sulphuric  acid  the  siilphonic  acid  is  formed,  this  being  then  fused  with 
one-half  of  its  weight  of  caustic  soda:  C6H5-SO3Na  +  2NaOH  =  H2O  +  Na2S03  + 
C6H5-  ONa.  The  addition  of  acid  then  liberates  pure  synthetic  phenol,  which  has  very  little 
smell  and  is  suitable  for  the  manufacture  of  picric  and  salicylic  acids,  &c. 

Pure  phenol  crystallises  in  long,  colourless  needles  melting  at  42-5°  and  boiling  unchanged 
at  183°  ;  it  has  a  specific  gravity  of  1-084,  dissolves  in  15  parts  of  water  at  16°,  and  is 
readily  soluble  in  alcohol  or  ether.  It  has  a  characteristic  odour,  is  poisonous,  and  on 
account  of  its  great  antiseptic  power  is  largely  used  as  a  disinfectant  in  medicine  and 
surgery  2  ;  in  many  cases  it  is,  however,  replaced  by  other  antiseptics  (corrosive  sublimate, 
cresols,  &c.)  which  have  not  the  unpleasant  odour  of  phenol.  The  maximum  antiseptic 
action  of  phenol  is  exerted  in  aqueous  solution  and  in  presence  of  acid,  owing  to  its  partial 
dissociation  into  the  ions  CeHgO1  and  H'  ;  according  to  Pfliigge,  when  dissolved  in  pure 
alcohol  or  in  oil,  it  has  no  antiseptic  action,  since  it  is  then  not  dissociated. 

It  dissolves  in  caustic  alkali  solutions  (forming  phenoxides,  e.g.  C6H5-ONa),  but  not 
in  those  of  alkali  carbonates.  With  formaldehyde  it  forms  resinous  condensation  products 
(artificial  sealing-wax  :  Resit,  1909). 

A  pine  splinter,  moistened  with  hydrochloric  acid,  is  coloured  bluish  green  by  phenol. 

1  Testing-  of  Carbolic  Acid.  Commercial  pure  phenol  melts  at  39°,  other  pure  forms  melting  at  30"  to  35° 
and  boiling  at  183°  to  186°.  When  pure,  phenol  should  dissolve  completely  to  a  clear  solution  in  15  parts  of 
water  and  should  leave  no  residue  on  evaporation.  Phenol  which  does  not  crystallise  at  the  ordinary  temperature 
contains  at  least  10  per  cent,  of  higher  phenol  liquors.  The  exact  quantitative  estimation  of  pure  phenol  (not 
containing  cresols,  which  behave  like  phenol)  is  effected  by  transforming  it  into  tribromobenzene  by  Koppe- 
schaar's  method.  There  is  no  characteristic  reaction  for  distinguishing  the  phenols  from  cresols,  but  the  latter 
are  the  less  soluble  in  water.  An  approximate  method,  which  is  used  in  practice,  and  is  suggested  also  in  the 
German  Pharmacopeia,  for  determining  the  phenol-content  of  crude  carbolic  acid  is  as  follows  :  10  vols.  of  the 
product  are  shaken  for  a  long  time  with  90  vols.  of  sodium  hydroxide  solution  (sp.  gr.  1-079)  in  a  graduated 
cylinder  and  then  left  to  stand  until  two  layers  separate  ;  the  volume  of  the  undissolved  non-phenol  is  then  read 
off  and,  after  this  has  been  removed,  the  residue  is  acidified  with  HC1  and  NaCl  added  to  separate  the  whole  of 
the  phenol,  the  volume  of  which  is  subsequently  measured. 

*  The  action  of  Antiseptics  or  Disinfectants  (see  also  p.  127)  depends  on  the  chemical  character  of  the 
antiseptic  substance  and  partly  on  the  quantity  and  nature  of  the  substance  to  be  disinfected.  The  poisonous 
action  of  disinfectants  is  the  result  of  a  chemical  action  between  the  proteins  of  the  plasma  of  the  living  cells, 
this  having  varying  affinities  towards  different  antiseptics  ;  the  concentration  of  the  latter,  the  duration  of  the 
action,  <tc.,  also  influence  the  action.  With  some  poisonous  and  very  dilute  solutions  (the  limit  of  dilution  for 
combination  to  occur  between  the  proteins  and  the  antiseptic  varies  with  the  nature  of  the  latter),  certain  micro- 
organisms fix  the  whole  of  the  metal  of  the  antiseptic  (e.g.  copper  or  mercury  from  their  salts) ;  the  solution 
does  not  then  react  with  hydrogen  sulphide,  while  the  cells  of  the  micro-organism  do  so.  The  following  Table 
shows  the  approximate  doses  of  different  antiseptics  necessary  to  kill  10  grms.  of  beer-yeast  (containing  30  per 


542 


ORGANIC    CHEMISTRY 


The  imports  of  carbolic  acid  into  Italy  were  888  quintals  in  1903,  1574  in  1904,  1882  in 
1907,  and  4000  (worth  £9100)  in  1910.  In  1905  Germany  imported  55,375  quintals  of  crude 
carbolic  acid  at  28s.  per  quintal  and  exported  53,000  quintals  of  the  refined  product  at 
58*.  per  quintal  (total,  £155,200)  ;  in  1908  39,825  quintals  (36,242  from  England)  were 
imported  and  44,476  quintals  (13,000  to  Russia  and  8000  to  the  United  States)  exported. 
In  1911  England  exported  8000  tons  (£162,500)  of  carbolic  acid,  while  the  United  States 
imported  1150  tons  (£38,000). 

The  price,  of  commercial  dark  carbolic  acid  is  about  13s.  to  16s.  per  quintal  for  the 
25  to  30  per  cent,  product  ;  20s.  to  24s.  for  50  to  60  per  cent.,  and  30s.  to  40s.  for  100  per 
cent.  ;  the  pale  acid  costs  34s.  to  56s.  ;  pure  redistilled  crystals,  m.pt.  35°,  110s.  ;  chemi- 
cally pure,  136s.,  and  synthetic  phenol,  148s.  Calcium  phenoxide  costs  16s.  for  the  20  per 
cent,  and  29s.  for  the  50  per  cent,  product. 

Phenol  forms  phenoxides  with  many  metals  (Na,  K,  Hg,  Cu,  &c.).  The  alkali  phenoxides, 
when  heated  with  alkyl  iodides,  give  ethers,  e.g.  ANISOLE,  C6H5-  0-  CH3  ;  PHENETOLE, 
C6H5-OC2H5,  &c. 

These  ethers  are  neutral,  very  stable  liquids,  and,  as  is  the  case  with  the  corresponding 
aliphatic  compounds,  boil  at  lower  temperatures  than  the  phenols. 

They  are  decomposed  only  in  energetic  reactions.  For  instance,  hydriodic  acid  at  140° 
acts  on  them  with  formation  of  methyl  iodide,  this  reaction  serving  for  the  estimation  of 
methoxy -groups  in  phenolic  ethers  (Zeisel) :  C6H5-OCH3  +  HI  =  CH3I  +  CgHg-OH.1 

Phenol  also  forms  Acid  Derivatives,  e. g.  phenylsulphuric  acid,  C6H5-OS03H,  which  is 
stable  only  as  salts,  these  being  obtainable,  for  instance,  by  the  action  of  aqueous  potassium 
pyrosulphate  on  potassium  phenoxide.  They  are  formed  in  the  urine  by  the  putrefaction 
of  proteins,  and  are  estimated  by  determining  the  amount  of  sulphuric  acid  liberated  in 

cent.,  i.e.  3  grms.,  of  dry  matter),  but  these  numbers  would  doubtless  require  considerable  modification  in  the 
disinfection  of  other  materials  : 


0-05    to  0-1      grm.  carbolic  acid 


0-02 

0-04 

1-00 

2-00 

0-5 

0-7 

0-2 

0-5 

0-001 

0-002 

0-005 

0-01 

0-05 

0-1 

0-01     , 

0-025      , 

formaldehyde 
acetaldehyde 
o-hydroxy  her.  zaldehyde 
acetic  acid 
copper  sulphate 
corrosive  sublimate 
sodium  fluoride 
hydrofluoric  acid 


0-01    to  0-02    grm.  silver  nitrate 


0-05 

0-05 

0-05 

0-05 

0-02 

0-015 

0-5 


0-1  „  zinc  sulphate 

0-1  ,,  lead  acetate 

0-1  ,,  hydrochloric  acid 

0-1  ,,  caustic  soda 

0-05  „  potassium  permanganate 

0-03  ,,  chlorine 

1-0  .  tannin 


1  Estimation  of  Alkoxy-groups  by  Zeisel's  Method.  When  the  apparatus  (Fig.  409)  has  been  found  to  be  air- 
tight, 0-2  to  0-3  grm.  of  the  substance  is  introduced  into  the  flask,  A  (30  to  35  c.c.),  50  c.c.  of  alcoholic  silver 
nitrate  (2  grms.  fused  nitrate  +  5  c.c.  water  +  45  c.c.  absolute  alcohol)  into  the  two  flasks,  C,  and  then  10  c.c. 


FIG.  409. 

of  pure  hydriodic  acid  (sp.  gr.  1-7)  into  A.  The  latter  is  then  attached  to  the  condenser,  K,  through  which  water 
at  40°  to  50°  circulates  ;  the  Geissler  bulbs,  B,  which  are  kept  at  50°  to  60°,  contain  water  with  red  phosphorus 
(0-3  to  0-4  grm.)  in  suspension  to  retain  hydrogen  iodide.  The  flask,  A,  is  heated  in  a  glycerine  bath  until  its 
contents  boil,  carbon  dioxide  being  passed  slowly  (2  bubbles  in  2  seconds)  through  the  flask.  The  operation 
requires  about  15  minutes  and  is  complete  when  the  precipitate  formed  ifi  A  separates  sharply  from  the  super- 
natant clear  liquid.  The  total  contents  of  the  two  flasks,  C,  are  diluted  in  a  beaker  with  500  c.c.  of  water  and 
concentrated  to  about  one-half  the  volume  on  a  water-bath.  A  little  water  and  a  few  drops  of  nitric  acid  are 
then  added  and  the  liquid  heated  until  the  silver  iodide  separates,  this  being  then  filtered,  dried,  and  weighed  in 
the  usual  manner.  Various  modifications  of  this  method  have  been  suggested  for  volatile  substances  and  especially 
for  those  containing  sulphur  (the  substance  is  hydrolysed  with  concentrated  KaOH  and  the  products  absorbed 
after  first  passing  through  a  U-tube  containing  pumice  moistened  with  CuSO,  ;  a  current  of  air  and  not  of  COS 
is  used  iu  this  case). 


DIHYDRIC    PHENOLS  543 

the  hot  by  dilute  hydrochloric  acid.  Even  carbonic  and  acetic  acids  form  analogous 
compounds. 

HALOGEN  DERIVATIVES  OF  PHENOLS.  The  hydroxyl  group  of  phenol  facilitates 
the  replacement  of  the  hydrogen  atoms  of  the  benzene  nucleus  by  halogens  ;  even  in 
the  cold,  bromine  water  forms  Tribromophenol.  Chlorination  can  be  effected  by  the  direct 
action  of  chlorine  or  by  sulphuryl  chloride,  while  replacement  by  iodine  is  facilitated  in 
alcoholic  solution,  or  in  presence  of  mercuric  oxide  (which  oxidises  the  hydriodic  acid  as 
it  is  formed),  or  in  an  aqueous  alkaline  solution.  The  halogen  usually  assumes  the  ortho- 
or  para-position  with  respect  to  the  hydroxyl. 

While  o-  or  p-cresol  combines  with  only  two  atoms  of  bromine,  the  action  of  chlorine 
on  anisole,  C6H5'0'CH3,  at  60°  in  presence  of  a  little  iodine,  yields  tetra-  or  even  penta- 
chloroanisole,  C6C15-OCH3.  Halogen  derivatives  of  phenols  may  also  be  obtained  by 
diazotising  halogenated  aminophenols. 

In  general,  they  are  colourless  crystalline  compounds  of  pungent  odour  and  decidedly 
acid  character  (trichlorophenol  decomposes  carbonates)  ;  when  they  are  fused  with  potash, 
the  halogen  atom  gives  way  to  another  hydroxyl  group,  which,  however,  often  enters  partly 
in  a  position  different  from  that  occupied  by  the  halogen.  Under  the  further  action  of 
chlorine,  tri-  and  penta-chloro  phenol  yield  additive  products,  the  OOH  group  being  at 
the  same  time  converted  into  CO. 

PHENOLSULPHONIC  ACIDS,  OH-C6H4-S03H,  are  obtained  by  treating  phenol 
with  concentrated  sulphuric  acid,  the  o-  and  p-compounds  being  formed  with  equal  ease  ; 
the  o-  is  converted  into  the  p-compound  by  heating  with  water.  The  m-compound  is 
obtained  indirectly  by  fusing  m-benzenedisulphonic  acid  with  alkali. 

HOMOLOGUES  OF  PHENOL  (see  Table,  p.  540).  Oxidation  of  the  side-chains  in 
these  leads  to  aromatic  hydroxy-acids. 

The  Cresols  are  not  oxidised  by  chromic  acid  mixture,  but  are  completely  decomposed 
by  permanganate  ;  if,  however,  the  hydroxylic  hydrogen  is  replaced  by  an  alkyl  or  by 
acetyl,  oxidation  proceeds  in  the  ordinary  way. 

The  three  isomeric  Hydroxy  toluenes,  CH3-C6H4-OH,  bear  the  generic  name  of  cresols. 
They  are  present  in  wood-tar  and  may  also  be  prepared  from  the  corresponding  amino- 
derivatives  or  sulphonic  acids.  The  cresols  react  with  bromine  water.  The  crude  cresols 
mixed  with  soap  solution  form  creoline  or  lysol,  which  serves  as  a  convenient  antiseptic 

and  is  largely  used.  p-Cresol,  CH3/  /OH,  is  formed  in  the  putrefaction  of  proteins. 

OH 

/  -  \  njr 

THYMOL,  CH3/  /CH<^       3,  js  found  in  oil  of  thyme  and  has  an  antiseptic 


action.      One  of  its  iodo  -derivatives,  Aristol,  is  used  as  a  substitute  for  iodoform. 
OH 

/  --  \  PJT 

CARVACROL,  CH3^  ^CH-c^    3,  occurs  in  Origanum  hirtum,  and  is  formed  by 


heating  camphor  with  iodine  or  by  the  action  of  phosphoric  acid  on  carvone  (see  Terpenes). 
ANETHOLE,  CH3O-CGH4-CH  :  CH-CH3,  is  a  colourless  solid  melting  at  228°,  boiling 
at  233°,  and  having  the  sp.  gr.  0-986  at  21-5°  ;  it  has  a  pleasing  odour  and  occurs  in  Anise 
oil  (from  the  seeds  of  Pimpinella  anisum),  from  which  it  is  obtained  by  repeated  fractional 
distillation  or  by  freezing;  Synthetically  it  is  prepared  from  anisaldehyde  and  sodium 
propionate  by  Perkin's  reaction  (see  p.  291  ),  its  constitution  being  thus  proved.  In  the  pure 
state  it  costs  20s.  per  kilo. 

(b)  DIHYDRIC  PHENOLS 

These  contain  two  hydroxyl  groups  united  to  the  carbon  of  the  benzene 
nucleus.  They  are  analogous  in  their  chemical  behaviour  to  monohydric 
phenols,  and  are  prepared  by  similar  methods  ;  certain  of  them  show  marked 
reducing  properties.  With  lead  acetate,  pyrocatechol  gives  a  white  precipi- 
tate, hydroquinone  is  precipitated  in  presence  of  ammonia,  while  resorcinol  is 
not  precipitated. 

PYROCATECHOL  (Catechol),  C6H4(OH)2  (1:2),  forms  crystals  melting  at  104°  and 
subliming  ;  it  dissolves  readily  in  water,  alcohol,  or  ether.  It  is  found  in  various  resins  and 


544  ORGANIC    CHEMISTRY 

is  obtained  by  distilling  catechu  (Mimosa  catechu) ;  it  is  now  prepared  by  fusing  o-phenol- 
sulphonic  acid  (see  p.  543)  with  caustic  potash. 

Its  alkaline  solution  is  unstable,  and  is  coloured  first  green  and  then  black  by  the 
oxygen  of  the  air  ;  it  reduces  silver  salts,  and  by  ferric  chloride  is  coloured  green  or  violet 
if  a  little  ammonia  is  present  (characteristic  reaction  of  ortho-dihydroxy- compounds).  With 
bromine  water  it  gives  tribromoresorcinol,  which  melts  at  118°,  is  soluble  in  water,  and  turns 
brown  in  the  air. 

OH 

Its  monomethyl  Ether,  <^  \OCH3,  is  called  GUAIACOL  and  occurs  abundantly 

in  beech-tar  ;  it  is  used  in  medicine  as  an  expectorant.  It  is  obtained  by  shaking  the 
creosote  oil  (fraction  boiling  at  200°  to  250°)  from  the  distillation  of  the  above  tar  with 
ammonia,  treating  with  alcoholic  potash,  washing  with  ether,  crystallising  the  potassium 
compound  from  alcohol,  and  decomposing  it  with  dilute  sulphuric  acid.  It  is  obtained 
crystalline  by  allowing  its  light  petroleum  solution  to  evaporate  slowly.  Synthetically 
it  is  prepared  by  diazotising  o-anisidine,  acidifying  with  dilute  sulphuric  acid,  and  distilling 
in  steam.  It  melts  at  29°,  boils  at  205°,  and  dissolves  in  about  60  parts  of  water.  It  costs 
from  10s.  to  13s.  per  kilo. 

RESORCINOL,  C6H4(OH)2  (1 :  3),  is  formed  on  fusing  various  resins,  such  as  galbanum 
and  asafcetida,  with  potash,  and  also  from  m-phenolsulphonic  acid  or  m-bromobenzene- 
sulphonic  acid  ;  it  is  prepared  industrially  from  m-  or  p-benzenedisulphonic  acid  (prepared 
from  toluene-free  benzene)  by  fusion  with  potash.  It  forms  rhombic  crystals  melting  at 
110°,  and  boils  at  270°  with  partial  decomposition.  It  turns  brown  in  the  air,  is  soluble 
in  water,  alcohol,  and  ether,  and  slightly  so  in  benzene,  and  reduces  silver  nitrate.  It  is  a 
less  energetic  disinfectant  than  carbolic  acid. 

With  nitrous  acid  or  diazo -compounds  it  forms  dyes  and,  like  all  m-dihydroxy benzenes, 
with  phthalic  anhydride  at  200°  it  yields  fluorescein.  Commercial  resorcinol  costs  5s.  Qd. 
per  kilo  and  the  pure  compound  20s. 

HYDROQUINONE  (Quinol),C6H4(OH)2  (1  :  4),  isobtained  by  oxidising  aniline  in  the 
cold  with  sulphuric  and  chromic  acids,  or  by  reducing  quinone  with  sulphurous  acid. 
It  forms  dimorphous  crystals  melting  at  169°,  and  with  ammonia  gives  a  reddish  brown 
coloration.  Oxidising  agents  convert  it  into  quinone.  Owing  to  its  strong  reducing 
properties  it  is  used  as  a  photographic  developer. 

The  chemically  pure  compound  costs  8s.  per  kilo. 

OH 

ORCINOL  (Dihydroxytoluene),  CH3(^  y  ,  does  not  form  fluorescein  with  phthalic 

anhydride.  Its  ammoniacal  solution  oxidises  in  the  air,  giving  Orceine,  C28H2407N2,  which 
is  the  principal  component  of  natural  archil  and  is  related  to  litmus. 

OH 

HOMOPYROCATECHOL  (Homocatechol),  CH3<^          \OH,  gives  a  monomethyl 

OH 
ether,  Creosol,  CH  /          \OCH3. 

OCH3 

The  unsaturated  derivative,  Eugenol,  CH2  :  CH  •  CH2/  /OH,  is  the   principal 

component  (90  per  cent.)  of  clove  oil,  from  which  it  is  extracted  with  aqueous  potash,  being 
then  liberated  with  acid  and  rectified  in  a  stream  of  C02.  It  is  a  liquid  boiling  at  247-5° 
and  has  the  sp.  gr.  1-073  at  14°.  Hot  alcoholic  potash  displaces  the  double  linking  of 

OCH3 

eugenol,  giving  Isoeugenol,  CH3-CH:CH('  /^^'s  wn*cn   a^so    has    a    pleasant, 

characteristic  odour. 


T  RIH  YD  RIC    PHENOLS  543 

(c)  TRIHYDRIC  PHENOLS  (Trihydroxybenzenes) 

The  constitutions  of  the  three  isomeric  trihydroxybenzenes  have  now  been 
fixed  with  certainty  :  Pyrogallol,  1:2:3;  Hydroxyhydroquinone,  1:2:4  (as), 
and  Phloroglucinol,  1:3:5  (s). 

PYROGALLOL  (1:2:  3-Trihydroxybenzene ;  also  improperly  called  Pyro- 
gallic  Acid),  C6H3(OH)3,  is  prepared  by  heating  gallic  acid  (see  later)  for  hall 
an  hour  in  an  autoclave  at  200°  to  210°  with  2  to  3  times  its  weight  of  water  ; 
the  solution  is  decolorised  by  boiling  with  animal  charcoal,  filtered,  concen- 
trated, and  crystallised.  The  pyrogallol  thus  obtained  is  purified  by  sublima- 
tion and  then  forms  shining,  white,  poisonous  scales  or  needles,  melting  at 
132°  and  boiling  at  210°.  It  may  also  be  prepared  by  distilling  a  mixture 
of  1  part  of  gallic  acid  with  2  parts  of  powdered  pumice  in  a  current  of  C02. 

It  dissolves  in  1-7  part  of  water  or  ether,  or  in  1  part  of  alcohol.  In 
alkaline  solution  it  is  an  energetic  reducing  agent  and  absorbs  oxygen  from 
the  air  with  avidity  ;  it  is  used  in  gas  analysis  in  all  cases  in  which  oxygen 
is  to  be  absorbed  (see  Orsat  Apparatus,  vol.  i,  p.  375).  By  fresh  solutions  of 
ferrous  sulphate  it  is  coloured  blue,  by  ferric  chloride  brown,  and  by  silver 
nitrate  black. 

It  does  not  react  with  hydroxylamine  (see  Phloroglucinol).  Its  dimethyl 
ether  (Dimethyl  Pyrogallate),  OH-  C6H3(OCH3)2,  is  contained,  along  with  other 
homologous  ethers,  in  beech-tar. 

When  pure  it  costs  12-s.  to  14s.  6d.  per  kilo. 

HYDROXYHYDROQUINONE  (1:3: 4-Tnhydroxybenzene),  C6H3(OH)3, 
is  obtained  by  fusing  hydroquinone  with  caustic  soda  and  has  not  been  very 
closely  studied.  It  crystallises  from  ether  in  plates  melting  at  140-5°,  readily 
undergoes  change  in  aqueous  solution,  and  does' not  react  with  hydroxylamine 
(see  Phloroglucinol). 

PHLOROGLUCINOL,  C6H6O3,  is  obtained  by  fusing  various  resins  with 
KOH.  Baeyer  prepared  it  synthetically  by  condensing  3  mols.  of  ethyl 
sodiomalonate  in  the  hot,  3  mols.  of  alcohol  being  thus  eliminated  : 

0 
COOC2H5  c 

/H  C2H5C02-(Na)C         C(Na)-C02C2H5 

I  +3C2H5-OH; 

Na'  0  :  C          C :  0 

\/ 
COOC2H5  C-C02C2H5 

Ntt 

acidification  of  this  product  results  in  the  substitution  of  the  sodium  by 
hydrogen  with  formation  of  phloroglucinoltricarboxylic  acid,  which,  when  fused 
with  caustic  potash,  loses  its  carbethoxy-groups  and  gives  phloroglucinol.  The 

PTT    PO 

latter  should    therefore  have  the   constitution  C 0<Cn|j:  _P(C>CH2,   which 

contains  no  double  linking  and  corresponds  with  triketohexamethylene ;  in  accord 
with  this  structure,  it  reacts  with  3  mols.  of  hydroxylamine,  giving  a  trioxime. 

On  the  other  hand,  it  behaves  also  as  a  trihydroxybenzene  or  trihydric 
phenol,  giving  a  triacetyl-derivative  with  acetyl  chloride,  so  that  it  is  able 
to  exist  in  two  tautomeric  forms. 

This  explains  why,  when  it  is  treated  with  alcoholic  potash  or  with  an 
alkyl  iodide,  the  alkyl  groups  unite  with  carbon  and  not  with  oxygen  (as 
they  would  with  a  triphenol),  giving,  e.g.  hexaniethylphloroglucinol. 

Pure  phloroglucinol  costs  about  £16  per  kilo. 


546  O  R  G  A  N  I  C    C  H  E  M  I  S  T  R  Y 

(d)  POLYHYDRIC  PHENOLS 

From  dinitroresorcinol  is  obtained  a  Tetrahydroxybenzene,  C6H2(OH)4  (1:2:4:5). 
which  boils  at  220°,  while  chloranilic  acid  (see  later)  is  formed  by  the  oxidation  of  the 
dichloro-  derivative. 

HEXAHYDROXYBENZENE,  C6(OH)6,  is  obtained  as  potassium  derivative,  C606K6, 
in  the  manufacture  of  potassium  by  reduction  of  its  carbonate  :  K2C03  +  C2  =  SCO  +  K2 
and  6K  +  6CO  =  C606K6.  These  reactions  represent  a  further  example  of  the  synthesis 
of  organic  substances  from  inorganic  matter.  Hexahydroxybenzene  is  a  white,  crystalline 
substance  which  oxidises  readily  in  the  air  and  yields  benzene  when  distilled  with  zinc 
dust. 

Of  the  additive  products  formed  by  polyhydric  phenols  with  hydrogen,  quercitol  and 
inusitol  may  be  mentioned. 

QUERCITOL  (Pentahydroxycyclohexane  or  Acorn  Sugar) 


/ 
OH-CH/  >CH2, 

\CH(OH).CH(OH)/ 

s  found  in  acorns  and  is  similar  to  mannitol  ;  it  has  a  sweet  taste  and  forms  monoclinic 
prisms  melting  at  234°,  its  specific  rotation  being  [a]p6  =  +  24-16°.  When  heated  to  240° 
in  a  vacuum  or  fused  with  alkali  it  loses  water  yielding  various  aromatic  derivatives 
(hydroquinone,  quinone,  and  pyrogallol)  ;  on  reduction  with  HI,  it  gives  benzene,  phenol, 
pyrogallol,  quinone,  and  hexane.  When  oxidised  with  nitric  acid  it  forms  mucic  and 
trihydroxyglutaric  acids,  while  with  permanganate  it  yields  malonic  acid,  the  presence 
of  the  methylene  group,  CH2,  being  thus  confirmed.  It  forms  a  pentacetyl-derivative,  an 
explosive  pentanitrate,  and  a  pentachlorohydrin,  C6H7C15,  melting  at  102°  ;  the  formation 
of  these  compounds  demonstrates  the  presence  of  five  hydro  xyl  groups. 

INOSITOL  (Hexahydroxycyclohexane  or  Muscle  Sugar),  C6H6(OH)6,  is  similar  to 
quercitol  but  contains  a  CH  •  OH  group  in  place  of  the  CH2.  It  has  the  appearance  and,  to 
some  extent,  the  sweet  taste  of  the  sugars,  with  which  it  was  for  long  confused.  That  it  is  a 
cyclohexane  derivative  is  shown  by  the  formation  of  phenol,  benzene,  and  triiodophenol 
on  reduction  with  HI,  and  that  of  quinone  and  some  of  its  derivatives  on  treatment  with 
PC15.  The  presence  of  six  hydroxyl  groups  is  proved  by  the  formation  of  a  hexa-qcetate 
(m.pt.  212°)  when  it  is  treated  with  acetic  anhydride  and  zinc  chloride,  and  of  a  hexanitrate, 
C6H6(NO3)6  (m.pt.  120°),  under  the  action  of  concentrated  sulphuric  and  nitric  acids  ; 
the  hexanitrate  is  highly  explosive  and  reduces  Fehling's  solution.  Four  optical  isomerides 
are  known:  (1)  inactive;  (2)  dextro-rotatory,  [a]D+68-4°,  crystallising  with  2H20 
and  melting  at  247°  j  (3)  laevo-  rotatory,  [a]D  —  65°,  m.pt.  247°  ;  (4)  racemic,  melting  at 
250°.  Baeyers  stereochemical  conceptions  indicate  eight  possible  isomerides,  according 
to  the  arrangement  of  the  OH  and  H  above  or  below  the  plane  of  the  hexagon.  Inositol, 
especially  the  inactive  form,  occurs  in  beans,  lentils,  peas,  the  muscles  of  the  heart,  the 
brain,  &c.  The  inactive  modification  crystallises  from  water  with  2H20  at  temperatures 
below  50°  and  in  an  anhydrous  form,  m.p.  225°,  at  higher  temperatures  ;  it  boils  unchanged 
in  a  vacuum  at  319°  and  is  not  fermented  by  yeasts.  It  does  not  combine  with  phenyl- 
hydrazine  or  reduce  Fehling's  solution,  but  it  reduces  ammoniacal  silver  nitrate  solution  ; 
it  forms  a  basic  lead  salt,  (C6HuO6)2Pb,  PbO.  It  does  not  yield  quercitol  when  reduced, 
so  that  the  hydroxyl  groups  are  symmetrically  distributed. 

The  rnonomethyl  ether  of  i-inositol,  or  bornesitol,  is  found  in  Borneo  rubber,  and  the 
dimethyl  ether,  or  dambonitol,  C6H6(OH)4(OCH3)2,  in  Gabon  rubber.  The  monomethyl 
ether  of  d-inositol,  or  pinitol,  which  occurs  in  many  plants  and  plant-juices,  melts  at  186°, 
sublimes  at  200°,  and  has  a  rotation  of  +  67-5°.  The  monomethyl  ether  of  1-inositol,  or 
quebrachitol,  melts  at  186°,  boils  at  200°  in  vaciw,  and  with  HI  forms  1-inositol  ;  it  occurs 
in  quebracho  bark. 

E.  QUINONES 

These  may  be  regarded  as  derivatives  of  phenols  obtained  by  elimination 
of  hydroxyl  groups,  with  consequent  displacement  and  partial  elimination  of 
the  double  linkings  of  the  benzene  nucleus.  They  are  usually  yellow  and 


Q  U  I  N  O  N  E  S  547 

of  pungent  odour  and  possess  oxidising  properties  ;   they  are  volatile  in  steam, 
with  partial  decomposition. 

Oxidation  of  meta-  and  ortho-diphenols  does  not  yield  quinones. 

BENZOQUINONE  or  simply  Quinone,  C6H4O2,  can  be  obtained  by  oxidising  either 
p-aminophenol  or  sulphanilic  acid  (1:4—  NH2-C6H4-S03H),  or  p-phenolsulphonic  acid, 
or  hydroquinone,  or  aniline  (on  a  large  scale)  with  chromic  acid. 

On  sublimation  it  forms  fine  yellow  crystals  which  melt  at  116°,  giving  a  characteristic 
irritating  odour.  It  is  soluble  in  alcohol  or  ether  and  slightly  so  in  cold  water.  It  fixes 
hydrogen,  which  transforms  it  into  hydroquinone,  while  the  halogens  give  addition  or 
substitution  products  according  to  the  conditions.  With  HC1  it  forms  monochloro- 
hydroquinone,  C6H402  +  HC1  =  C6H3C1(OH)2.  With  amines  and  with  phenols  it  forms 
dyes  which  crystallise  well  but  are  only  slightly  soluble. 

With  hydroquinone  it  forms  a  condensation  product,  Quinhydrone,  C6H4O2-  C6H4(OH)2, 
which  consists  of  green  prisms  with  a  metallic  lustre,  and  may  be  regarded  as  an 
intermediate  product  in  the  oxidation  of  hydroquinone  or  in  the  reduction  of  quinone 

0:C/          \CH-0. 0-CH< 


Constitution.     That  quinone  contains  two  carbonyl  groups  is  deduced  from  the  fact 
that  with  hydroxylamine  it  yields  quinone  monoxime  and  quinonedioxime  : 

CO  C : NOH  C : NOH 

/\ 

CH  I 


HCll   I  CH 

CO  CO  C :  NOH 

Quinonemonoxime 
(nitrosophenol) 

It  contains  two  double  linkages,  since  in  benzene  solution  it  absorbs  four  atoms  of 
bromine,  while  ozone  is  also  fixed  quantitatively  (see  pp.  88  and  299). 

OH  CO 

/\  y\ 

The    transformation  of    hydroquinone,    |X|  >  into  quinone,   ||       ||  ,   is   an   evident 


OH  CO 

example  of  the  convertibility  of  the  centric  form  of  benzene  into  that  with  two  double 
linkages. 

Tetrachloroquinone  (chloranil),  C6C1402,  prepared  by  oxidising  trichlorophenol  with 
dichromate  and  sulphuric  acid,  serves  for  the  manufacture  of  coal-tar  dyes  ;  the  com^ 
mercial  product  costs  20s.  per  kilo,  and  the  pure  80*.  Toluquinone,  C6H3O2-CH3, 
xyloquinone,  thymoquinone,  &c.,  are  known,  as  also  are  quinoneimides  (e.g. 
C6H40-NH)  and  quinonediimides  [e.g.  C6H4(NH)2], 

F.  NITRO-DERIVATIVES  OF  AROMATIC  HYDROCARBONS 

These  are  readily  obtained  by  treating  the  hydrocarbons  with  concentrated 
nitric  acid,  best  in  presence  of  concentrated  sulphuric  acid,  which  fixes  the 
water  as  it  is  formed  : 

C6H6  +  HN03  =  H20  +  C6H5-N02. 

With  the  hydrocarbons  homologous  with  benzene,  nitration  is  still  more 
easy,  but  not  more  than '  three  nitro-groups  can  be  introduced  directly  ; . 
tetranitro-derivatives  are  prepared  indirectly.  Aromatic  nitre-compounds 
cannot  be  obtained  by  the  action  of  silver  nitrite  on  chlorobenzenes,  as  is 
the  case  with  those  of  the  fatty  series  ;  but  this  method  serves  for  the  intro- 
duction of  nitro-groups  into  side-chains. 

The  nitro-compounds  are  liquid  or  solid  and  usually  more  or  less  yellow, 
although  some  are  red  ;  they  are  heavier  than  water  and  dissolve  readily  in 


548 


ORGANIC    CHEMISTRY 


>, 

i 

BD 
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NITROBENZENE  549 

alcohol,  ether,  o£  acetic  acid,  but  are  mostly  insoluble  in  water.  They  distil 
unchanged  and  are  volatile  in  steam. 

The  nitro-group  is  united  very  firmly  to  the  nucleus,  especially  in  mono- 
nitrobenzene,  and  is  not  directly  replaceable.  It  can  be  reduced  to  the  amino- 
group  by  means  of  nascent  hydrogen  in  acid  solution  ;  reduction  in  alkaline 
solution  results  in  the  formation  of  azoxy-,  azo-,  and  hydrazo-compounds,  whilst  in 
neutral  solution  or  with  hydrogen  sulphide,  the  nitro-group  becomes  a  hydroxyl- 
amino-group.  On  electrolytic  reduction,  nitro-derivatives  yield  amino-phenoK 

Polynitrobenzenes  are  easily  obtained  by  the  action  of  fuming  nitric  acid 
in  the  hot  ;  the  me  ta  -derivative  is  formed  first  and  this,  by  further  nitration 
with  nitric  and  fuming  sulphuric  acids  at  140°,  gives  symm.  trinitrobenzene. 

The  polynitro-compounds  react  more  readily  than  mononitro-derivatives  ; 
when  the  former  are  oxidised,  a  phenolic  group  is  formed,  while  the  nitro- 
groups  remain  intact. 

With  para-  and  ortho-dinitrobenzenes,  sodium  alkoxide  replaces  one 
nitro-group  quantitatively,  whilst  with  m-dinitrobenzene  no  reaction  occurs  : 

C6H4(N02)2  +  C2H5-ONa  =  NaN02  +  N02-C6H4-OC2H5. 
By  boiling  o-dinitrobenzene  with  caustic  soda,  o-nitrophenol  is  formed  : 
_  N02  _OH 

NaOH  -  NaN02  +  < 


while  boiling  with  alcoholic  ammonia  yields  o-nitralinine  : 


N02  NH2 

A  £ 


N02  +  NH3  =  HNO2  +  C  >N02. 


NITROBENZENE,  C6H5-N02,  is  an  almost  colourless,  faintly  yellow, 
refractive  liquid  which  has  the  sp.  gr.  T209  at  15°  and,  after  solidification, 
melts  at  3°  and  boils  at  208°.  Owing  to  its  pleasant  bitter-almond  smell,  it 
is  used  in  perfumery  under  the  name  of  artificial  essence  of  mirbane,  but  its 
vapour  is  somewhat  poisonous.  It  is  insoluble  in  water,  but  it  mixes  in  all  pro- 
portions with  alcohol,  ether,  or  benzene. 

It  is  of  considerable  industrial  importance,  as  it  forms  the  raw  material  for  the 
manufacture  of  aniline,  benzidine,  quinoline,  azobenzene,  various  explosives,  &c. 

On  a  large  scale  it  is  prepared  in  wrought-  or  cast-iron  vessels,  employing 
precautions  and  methods  similar  to  those  used  in  making  nitroglycerine  (see 
p.  225).  The  nitro -sulphuric  mixture,  consisting  of  120  kilos  of  HN03  (42° 
Be.)  and  180  kilos  of  H2S04  (66°  Be.),  is  poured  gradually  (in  8  hours)  into 
100  kilos  of  benzene.  The  mass  is  kept  mixed  by  means  of  a  stirrer,  and  during 
the  first  5  to  6  hours  is  maintained  at  25°  by  means  of  cold  water  circulating 
outride  the  apparatus.  In  the  final  phase  of  the  reaction  the  temperature  is 
raised  by  external  steam  to  70°  to  90°,  the  heating  being  then  stopped,  while 
the  stirring  is  continued  for  a  further  6  hours.  The  mass  is  then  forced  by  a 
suitable  elevator  into  a  tank  with  a  conical  base.  The  acid  mixture  gradually 
settles  to  the  bottom,  while  the  nitrobenzene  floats  ;  the  former  is  then  drawn 
off  through  taps  (see  Nitroglycerine),  and  the  nitrobenzene,  after  repeated 
washing  with  water,  distilled  in  a  current  of  steam  from  a  vessel  with  a  jacketed 
bottom  heated  with  steam  at  2  to  3  atmos.  pressure.  A  second  distillation  yields 
moderately  pure  nitrobenzene.  According  to  Ger.  Pat.  221,787  of  1907,  nitro- 
benzene can  also  be  obtained  by  running  benzene  into  a  mixture  of  sulphuric 
acid  and  sodium  nitrate  at  70°  to  90°.  It  is  sold  at  72s.  to  104s.  per  quintal. 

The  imports  of  nitrobenzene  into  Italy  are  as  follow  :  11  quintals  in  1900, 
18  in  1907,  138  in  1908,  and  182,  of  the  value  of  £874,  in  1910. 


550 


DINITROBENZENES.  By  the  action  of  fuming  nitric  acid  or  of  a  suitable  nitro- 
sulphuric  mixture  on  benzene,  m-dinitrobenzene  is  formed  along  with  small  proportions 
of  the  ortho-  and  para-compounds.  The  me ta -derivative  crystallises  from  alcohol  in 
colourless  needles,  m.pt.  90°,  and  is  insoluble  in  water,  but  readily  soluble  in  alcohol  or 
ether.  The  ortho-  and  para-isomerides  are  obtained  indirectly  from  the  corresponding 
dinitroanilines  (see  Aniline)  by  elimination  of  the  amino-group  ;  both  form  colourless 
crystals.  On  reduction,  m-dinitrobenzene  gives  first  m-nitraniline  and  then  m-phenylene- 
diamine.  The  crude  product  costs  £6  per  quintal,  and  the  chemically  pure  8s.  per  kilo. 
Dinitrobenzene  dust  is  somewhat  poisonous. 

TRINITROBENZENE  (symm. ),  C6H3(N02)3.  Attempts  are  now  being  made  to  utilise 
this  compound  as  an  explosive.  It  is  obtained  by  oxidising  trinitrotoluene  (see  later)  with 
sulphuric  and  chromic  acids  (Ger.  Pat.  127,325)  and  decomposing  the  resultant  trinitro- 
benzoic  acid  by  heat, 

NITROTOLUENES 

MONONITROTOLUENES,  NO2-C6H4-CH3  (ortho-,  m.pt.  -10°,  b.pt.  218°  ;  meta-, 
m.pt.  +  16°,  b.pt.  230°  ;  para-,  m.pt.  +  54°,  b.pt.  236°).  Large  proportions  of  the  ortho- 
and  para -compounds  and  a  small  proportion  of  the  meta-compound  are  obtained  when 
toluene  is  nitrated  with  fuming  nitric  acid,  the  relative  amounts  varying  with  the  condi- 
tions of  the  reaction.  Thus,  if  highly  concentrated  nitric  acid  (sp.  gr.  1-53)  is  employed 
and  the  mass  is  not  cooled,  65  per  cent,  of  p-nitrotoluene  is  obtained  ;  but  if  such  a  weak 
acid  is  used  that  it  scarcely  reacts,  and  the  reacting  mass  is  cooled,  67  per  cent,  of  o-nitro- 
toluene  is  formed.  When  toluene  is  nitrated  with  nitric  and  sulphuric  acids,  60  to  66  per 
cent,  of  the  ortho -compound  is  obtained  (100  kilos  of  toluene  are  added,  in  the  course  of 
12  hours,  to  a  mixture  of  100  kilos  of  nitric  acid  of  44°  Be.  with  150  kilos  of  sulphuric  acid 
of  66°  Be.,  the  mass  being  stirred  and  cooled  and  the  decanted  nitro -products  washed  with 
water  and  alkali)  ;  the  unaltered  toluene  is  distilled  off  in  steam  and  the  nitrotoluene 
eventually  distilled  by  means  of  superheated  steam.  The  ortho-  and  para -compounds  are 
separated  by  fractional  distillation  ;  40  per  cent,  of  ortho -compound  distils  at  222°  to  223°, 
then  a  little  meta-,  and  above  230°  the  p-nitrotoluene.  The  separation  of  the  ortho-  and 
para-isomerides  may  also  be  effected  by  cooling  to  —  6°  (Ger.  Pat.  158,219,  Fr.  Pat. 
350,200),  when  almost  colourless  p-nitrotoluene  (melting  at  54°  and  boiling  at  236°  when 
pure)  crystallises  out  ;  o-nitrotoluene  is  a  yellow  liquid,  which  solidifies  at  —  10-5°,  boils 
at  218°,  and  has  the  sp.  gr.  1-168  at  15°.  The  crude  mixture  of  these  two  isomerides  costs 
96s.  to  1125.  per  quintal  and  is  used,  either  as  it  is  or  after  separation,  for  the  manufacture 
of  toluidine,  tolidine,  and  fuchsine. 

m-Nitrotoluene  is  formed  in  small  quantity  in  the  direct  nitration  of  toluene  (see  also 
Dinitro toluene),  but  in  the  pure  state  is  obtained  only  indirectly  from  m-nitro-p-toluidinc 
N02 

2,  by  Griess's  reaction  (see  Aniline).     Only  with  difficulty  is  it  nitrated 


further  to  dinitrotoluene,  thus  differing  from  the  other  mononitro toluenes.  It  has  no 
important  practical  use,  and  when  impure  costs  4s.  per  kilo,  and  when  pure  32s.  It  forms 
crystals  melting  at  16°,  boils  at  230-5°,  and  has  the  sp.  gr.  1-168  at  22°. 

DINITROTOLUENES,  C6H3(CH3)(NO2)2,  exist  in  six  isomeric  forms,  which  are 
prepared  and  named  in  various  ways.  Denoting  the  methyl  group  by  M  (always  in  position 
1)  and  the  nitro -group  by  N,  the  isomerides  have  the  following  configurations  : 


5          3 

4 


M 


M 


N 

m-dinitro  toluene 
ordinary  dinitrotoluene 
o :  p-dinitrotoluene 
a-dinitro  toluene 
2  :  4-dinitrotoluene 
m.pt.  70-5° 


N 


p-dinitrotoluene 
e  -p-dinitrotoluene 
2  :  5-dinitrotoluene 
m.pt.  48° 


X 


N 


o :  m-dinitrotoluene 
1:2:  3-dinitrotoluene 
m.pt.  63° 


551 


N 


N 


X 


o  :  o-dinitrotoluene  m  :  m-dinitrotoluene  m  :  p-dinitrotoluene 

j3-dinitrotoluene  S-dinitrotoluene  y-dinitrotoluene 

2  :  6-dinitrotoluene  3  :  o-dinitrotoluene  3  :  4-dinitrotoluene 

m.pt.  61°  m.pt.  92°  m.pt.  60° 

Of  the  various  names,  the  last  given  in  each  case  is  the  simplest  and  clearest. 

When  toluene  is  nitrated  directly  with  a  suitable  nitro-sulphuric  mixture  (richer  in 
nitric  acid  and  poorer  in  water  than  for  mononitrotoluene)  and  the  mass  is  finally  heated 
almost  to  boiling,  the  main  product  is  ordinary  solid  dinitrotoluene  (2  :  4),  a  little  trinitro- 
toluene and  2  :  5-dinitrotoluene  being  also  formed.  About  35  per  cent,  of  the  crude  mass 
always  consists  of  a  liquid  product  which  is  separated  by  centrifugation  and  was  thought 
to  be  another  isomeride,  but  Glaus,  Becker,  Nolting,  and  Witt  have  shown  it  to  be  a  mixture 
of  2  :  4-  and  2  :  6-dinitrotoluenes  and  40  per  cent,  of  mononitrotoluenes  (equal  parts  of 
p-  and  m-  and  a  little  o-)  ;  the  mononitrotoluenes  can  be  removed  by  distillation  in  a 
vigorous  current  of  superheated  steam.  This  orange-red  mixture  of  liquid  products  gela- 
tinises collodion -cotton  well  and  serves  for  the  preparation  of  incongealable  dynamites  and 
powders  or  dynamites  with  ammonium  nitrate  as  basis. 

2 : 4-Dinitrotoluene  is  prepared  as  described  above  and  is  the  one  in  most  common  indus- 
trial use,  while  it  serves  also  for  making  ordinary  (2:4:6)  trinitrotoluene.  It  is  purified 
by  crystallisation  from  alcohol  or  carbon  disulphide  and  forms  monoclinic  crystals  melting 
at  70-5°  ;  it  is  insoluble  in  water,  slightly  soluble  in  cold  alcohol  or  ether,  still  less  so  in 
carbon  disulphide  (2-2  per  cent.),  and  readily  soluble  in  benzene.  It  dissolves  in  alkali, 
giving  a  red  solution,  from  which  acids  precipitate  a  reddish  brown  substance.  Fuming 
nitric  acid  oxidises  it  slowly  and  in  the  hot  gives  the  corresponding  o  :  p-dinitrolenzoic 
acid,  C6H3(CO2H)(N02)2-  With  hot,  concentrated  nitro-sulphuric  mixture,  it  forms  ordi- 
nary trinitrotoluene  (see  below).  Ammonium  sulphide  reduces  it  in  the  cold  to  o-nitro-p- 
toluidine  (m.pt.  105°),  while  in  the  hot,  p-niiro-o-toluidine  (m.pt.  78°)  is  also  formed.  By 
zinc  and  hydrochloric  acid  it  is  reduced  to  tolylenediamine. 

2  :  6-Dinitrotoluene  is  obtained  along  with  the  2  :  4-isomeride  and  accumulates  in  the 
mother-liquors,  when  mononitrotoluene  (ortho)  is  nitrated  further.  It  is  prepared  in  the 
pure  state  by  eliminating  the  amino-group  from  dinitro-p-toluidine  (m.pt.  168°).  It  forms 
shining  needles,  m.pt.  61°,  dissolves  to  some  extent  in  alcohol,  and  with  ammonium  sulphide 
gives  o-nitro-o-toluidine. 

2  : 3-Dinitrotoluene  is  obtained  by  heating  o  :  m-dinitro-p-toluic  acid  with  dilute  hydro- 
chloric acid  for  6  hours  at  265°  and  distilling  in  a  current  of  steam,  the  crystals  formed 
being  pressed  or  centrifuged  ;  it  separates  from  light  petroleum  solution  in  yellow  crystals, 
m.pt.  63°. 

2  :  5-Dinitrotoluene  is  obtained  together  with  the  2  :  4-derivative  when  toluene  or 
nitrotoluene  is  run  into  fuming  nitric  acid  ;  it  crystallises  from  alcohol  in  yellow  needles, 
m.pt.  48°.  Alcoholic  ammonium  sulphide  reduces  it  to  o-nitro-m-toluidine. 

3 :  5-Dinitrotoluene  is  formed  by  eliminating  the  amino-group  by  diazotisation  (see 
Aniline)  from  dinitro-o-toluidine  (m.pt.  208°)  or  from  m  :  m-dinitro-p-toluidine  (m.pt.  168°). 
From  water,  in  which  it  is  sparingly  soluble,  it  crystallises  in  needles,  m.pt.  92°.  It  is  soluble 
slightly  in  light  petroleum,  more  so  in  cold  alcohol  or  in  carbon  disulphide,  and  readily  in 
chloroform,  ether,  or  benzene.  It  distils  easily  in  a  current  of  steam,  and  with  benzene 
forms  the  crystalline  double  compound,  C6H3(CH3)(N02)2  +  C6H6. 

3 :  4-Dinitrotoluene  is  obtained  by  protracted  agitation  of  m -nitrotoluene  with  concen- 
trated nitric  acid  (sp.  gr.  1-54).  From  carbon  disulphide  (which  dissolves  2-19  per  cent.), 
it  crystallises  in  long  needles  melting  at  60°. 

TRINITROTOLUENES.  The  following  six  isomerides  are  possible,  only  the  first  three 
being  known : 


O  R  G  A  N  I  C    C  H  E  M  I  S  T  R  Y 

M  M  M 


N 


N 

a-triuitrotoluene 
2:4:  6-trinitrotoluenc 
melts  at  82°  and  solidifies 
at  80  5 


M 


X 


N 
2:3:  4-trinitrotoUiene 


X 


/3-triiiitiotolu3ne 
2:3:  6-trinitrotoluene 
m.pt.  112° 

M 


X 


3:4:  5-tiinitrotolucue 


X 


N 

p-trinitrotoluene 
2:4:  5-trinitrotolaene 
m.pt.  104° 


N 


X 


X 


3  :  5-trinitiotolucne 


Rudeloff  (1907)  is  of  opinion  that,  together  with  a  -trinitrotoluene,  two  other  isomerides, 
melting  at  73°  and  78°,  are  formed,  but  these  are  probably  more  or  less  impure  a-compounds. 

a-TRINITROTOLUENE  (ordinary  or  2  :  4  :  6-Trinitrotoluene)  is  formed  on  heating 
toluene  for  several  days  or,  better,  2  :  4-dinitrotoluene  for  some  hours,  with  a  highly  con- 
centrated nitro -sulphuric  mixture,  the  operation  being  begun  at  a  low  temperature  and 
with  constant  mixing,  and  the  temperature  being  raised  gradually  to  100°.  After  removal 
of  the  acids  by  decantation,  the  mass  is  washed  with  boiling  water  and  purified  by  crystal- 
lisation from  alcohol  or  from  concentrated  sulphuric  acid,  in  which  it  dissolves  in  the  hot 
(V.  Vender,  Fr.  Pat.  405,812  of  1909). 

It  forms  pale  yellow  crystals  which  darken  under  the  influence  of  light  ;  it  melts  at 
82°  and  solidifies  at  80-5°.  At  a  higher  temperature  it  undergoes  partial  sublimation,  and 
when  heated  rapidly  to  240°  it  sometimes  explodes.  It  is  very  slightly  soluble  in  water 
(0-164  per  cent,  at  100°  and  0-021  per  cent,  at  15°)  ;  the  mixture  of  nitric  and  sulphuric 
acids  containing  15  per  cent,  of  water  dissolves  from  2  per  cent,  to  5  per  cent,  according 
to  the  proportion  of  nitric  acid  present  ;  99  per  cent,  sulphuric  acid  dissolves  it  to  the 
extent  of  66  per  cent,  at  100°  and  of  10  to  12  per  cent,  at  20°.  Alcohol  dissolves  2  to  3 
per  cent,  of  it  in  the  cold  and  25  per  cent,  in  the  hot  ;  it  is  readily  soluble  in  ether,  acetone, 
or  benzene  ;  cold  carbon  disulphide  dissolves  only  0-39  per  cent. 

When  non -compressed  the  crystals  have  the  density  0-8  to  1,  but  if  they  are  fused  and 
allowed  to  solidify  under  ordinary  pressure  the  density  is  1-54  to  1-57  ;  while  if  the  solidifi- 
cation takes  place  under  a  pressure  of  3  to  4  atmos.  (Bichel,  1906)  or  with  rapid  cooling 
(Nobel  Dynamite  Co.,  Hamburg,  1907),  the  value  1-61  to  1-62  is  attained.  When  the 
crystals  are  compressed  in  a  hydraulic  press  to  200  to  600  kilos  (or  to  3000  kilos)  per  square 
centimetre,  they  assume  a  density  of  1-59  (or  1-68). 

When  aniline  is  poured  into  an  alcoholic  solution  of  trinitrotoluene,  a  double  compound, 
C6H2(CH3)(N02)3  +  C6H5'NH2,  separates  in  red  acicular  crystals  melting  at  84°.  If 
heated  at  180°  with  ten  times  its  weight  of  fuming  nitric  acid,  trinitrotoluene  is  converted 
into  s-trinitrobenzene.  While  picric  acid  (which  is  now  partly  replaced  by  trinitrotoluene 
as  an  explosive)  readily  forms  with  metals  picrates  dangerous  to  handle,  trinitrotoluene 
does  not  react  with  metals  and  can  be  manipulated  safely  even  in  the  hot,  since  it  burns 
slowly  without  exploding  ;  it  is  not  hygroscopic  and  does  not  form  a  bitter  and  poisonous 
powder  like  picric  acid.  It  is  highly  stable  to  shock,  and  when  compressed  is  exploded  with 
a  mercury  fulminate  cap  ;  but  when  fused  and  then  solidified  it  is  exploded  only  by  a 
detonator  of  moderately  compressed,  crystalline  trinitrotoluene,  which  in  its  turn  is 
exploded  by  a  fulminate  cap.  The  velocity  of  detonation  in  a  charge  50  mm.  in  diameter 
and  with  a  density  of  1-55  is  7500  metres  (picric  acid,  8000  metres). 

The  theoretical  decomposition  is  expressed  by :  2C6H2(CH3)(NO2)3  =  12CO  +  2CH4 
+  H2  +  3N2,  1  kilo  giving  778  litres  of  gases,  which  are  incompletely  burnt  owing  to  lack 
of  oxygen. 

The  use  of  trinitrotoluene  as  an  explosive  was  suggested  prior  to  1890,  and  attempts 


PHENYLNITROMETHANE  553 

were  made  to  compensate  the  deficiency  of  oxygen  by  addition  of  ammonium  nitrate.  But 
it  has  been  largely  used,  mainly  as  a  result  of  Bichel's  investigations,  only  since  1904,  and 
in  the  crystalline  state  it  now  forms  a  very  important  military  explosive.  In  the  com-' 
pressed  or  solidified  state  it  is  used  for  charging  projectiles,  grenades,  &c.  (it  does  not  serve 
for  propelling  projectiles,  owing  to  its  shattering  power  and  to  the  abundance  of  fumes  it 
forms  on  explosion).  Different  firms  produce  it  under  various  names  (trotyl,  trolite,  trilite, 
trinol,  tritole).  Germany  manufactures  12,000  to  15,000  quintals  per  annum,  and  Italy 
4000  to  5000  ;  the  price  varies  from  2s.  Gd.  to  4«.  per  kilo,  according  as  it  is  crystallised, 
granulated,  fused,  or  compressed. 

For  some  time  a  plastic  product  called  plastrotyl  (Bichel,  1906)  was  prepared  from 
trinitrotoluene,  resin,  collodion-cotton,  and  crude  liquid  dinitrotoluene,  but  this  is  no 
longer  manufactured. 

/3-TRINITROTOLUENE  or  2  :  3  :  6-Trinitrotoluene  is  formed  in  small  proportion  with 
a  large  proportion  of  the  y-isomeride  (see  below)  when  m-nitro toluene  is  boiled  for  a  day  with 
nitric  and  sulphuric  acids.  It  separates  from  carbon  disulphide  or  alcohol  in  colourless 
crystals  melting  at  112°,  and  is  readily  soluble  in  ether,  acetone,  or  benzene.  With  alcoholic 
ammonia  in  the  hot  it  gives  y-dinitrotoluidine  (m.pt.  94°). 

•y-TRINITROTOLUENE  or  2  :  4  :  5-Trinitrotoluene  is  formed  with  the  /3-isomeride 
(see  above),  from  which  it  can  be  separated  in  virtue  of  its  slight  solubility  in  alcohol  or 
carbon  disulphide.  It  forms  yellowish,  shining  crystals,  melting  at  104°.  When  heated 
with  alcoholic  ammonia  it  forms  /3-Dinitrotoluidine,  while  with  aniline  in  the  cold  it  gives 
Phenyldinitrotoluidine,  melting  at  193°.  Also  with  aniline  its  hot  alcoholic  solution  gives 
orange  crystals  of  y-Dinitrotolylphenylamine,  m.pt.  142°. 

CHLORO-  and  BROMO-NITROBENZENES.  The  para-derivatives  melt  at  higher 
temperatures  than  the  meta-  and  these  at  higher  temperatures  than  the  ortho -com pounds. 
This  rule  often  holds  with  aromatic  compounds. 

Nitration  of  chlorobenzene  yields  much  para-  and  little  or^o-derivative  ;  the  meta- 
compound  is  prepared  indirectly  from  m-nitraniline  by  transforming  the  amino -group 
and  replacing  it  by  halogen. 

TRINITROTERT.BUTYLXYLENE  has  an  odour  of  musk  and  is  used  as  a  perfume. 

PHENYLNITROMETHANE,  C6H5-CH2-NO2,  contains  the  nitro-group  in  the  side- 
chain,  as  is  shown  by  its  method  of  preparation  : 

C6H5.CH2C1   +  AgN02  =  AgCl   +  C6H6  -  CH2 .  N02. 

Benzyl  chloride 

It  is  obtained  also  by  heating  toluene  with  nitric  acid  (sp.  gr.  1-12)  under  pressure. 
This  compound  exists  in  two  isomeric  (or  tautomeric)  forms,  one  being  known  as  a  pseudo- 
acid  :  (1)  C6H5.CH2.N02  and  (2)  C6H6 . CH  :  NO •  OH  (pseudo-acid)  ;  the  former  does 
not  react  with  ferric  chloride,  while  the  latter  gives  a  coloration.  Modification  (1)  is  a 
liquid,  and  its  aqueous  solution  gives,  with  sodium  alkoxide,  the  sodium  salt  of  the  pseudo- 
acid  ;  when  the  acid  is  liberated  by  means  of  a  mineral  acid  it  forms  a  crystalline  product, 
which  has  the  same  composition  as  the  original  compound  and  gradually  changes  into 
this,  becoming  liquid.  The  presence  of  a  hydroxyl  group  in  the  pseudo-acid  is  demonstrated 
by  the  formation  of  the  characteristic  dibenzhydroxamic  (or  dibenzoylhydroxamic)  acid  by 
treatment  with  benzoyl  chloride  : 

C6H5-CH  :  NO-ONa  +  C6H5.CO-C1  =  NaCl  +  C6H5.CH  :  NO •  O •  CO •  C6H5 

C6H5.CO-NH.O.CO.C6H5 

Dibenzhydroxamic  acid 

That  these  isonitro -compounds  contain  hydroxyl  is  shown  also  by  the  fact  that  they 
react  in  the  cold  with  phenyl  isocyanate,  while  the  nitro -compounds  do  not. 

_N02 

Similar  behaviour  is  shown  by  m-Nitrophenylnitromethane,  ^  \  ;    the 

~CH2.N02 

passage  from  the  yellow  pseudo-acid  to  the  colourless  nitro-compound  is  clearly  shown 
by  the  change  both  in  colour  and  in  electrical  conductivity,  which  is  very  high  for  the 
pseudo-acid  (as  for  acids  in  general)  and  almost  zero  for  the  normal  nitro-compound,  into 
which  it  is  gradually  converted. 


554  ORGANIC    CHEMISTRY 

These  nitro -derivatives  of  the  side  chain  can  hence  yield  metallic  derivatives — of  the 
pseudo-acids  ;  treatment  of  these  derivatives  with  acid  yields  the  normal  form,  and  the 
latter  in  presence  of  alkali  is  only  slowly  neutralised,  this  being  characteristic  of  the  pseudo- 
acids. 

In  benzene  solution  the  true  acids  combine  rapidly  with  ammonia,  forming  insoluble 
ammonium  salts,  while  pseudo -acids  combine  only  slowly  or  not  at  all  with  ammonia. 

G.  AMINO-DERIVATIVES  OF  AROMATIC  HYDROCARBONS 

When  the  hydrogen  atoms  of  benzene  are  replaced  by  amino-groups  or  the 
hydrogen  of  ammonia  or  of  a  primary  aliphatic  amine  by  phenyl -groups,  the 
resulting  products  are  mono-,  dl-,  or  tri-amines  in  the  first  case  and  secondary 
and  tertiary  amines  in  the  second. 

Some  of  the  aromatic  amines  are  similar  to  but  weaker  than  the  aliphatic 
bases,  the  phenyl  group  being  somewhat  negative  in  character  compared  with 
the  positive  alkyl  groups. 

Aromatic  amines  form  salts  with  acids  and  double  salts  with  platinum 
chloride.  In  contact  with  the  vapours  of  volatile  inorganic  acids  they  form 
white  fumes  in  the  air  in  the  same  way  as  ammonia  ;  they  distil  undecomposed. 
The  diamines  are  more  highly  basic  than  the  monamines. 

Isomerides  of  the  amines  are  formed  when  the  amino  group  enters  side 
chains. 

1.  PRIMARY  MONAMINES 

Primary,  secondary,  and  tertiary  aromatic  monamines  are  distinguished  by 
the  same  reactions  as  are  used  for  aliphatic  amines  (by  nitrous  acid,  &c.  ;  see 
p.  201). 

Formation,  (a)  Mono-,  di-amines.  &c.,  are  usually  obtained  by  reducing 
the  nitro-derivatives  with  tin  or  stannous  chloride  and  hydrochloric  acid, 
or  with  iron  and  acetic  acid,  or  with  ammonium  sulphide,  &c.  :  -C6H5-N02  + 
6H  =  2H20  +  C6H5-NH2.  The  reduction  may  also  be  effected  electrolytically 
(see  later,  p.  566). 

(b)  By  heating  phenols  (or,  better,  nitrophenols  or  naphthols)  with  ammo- 
niacal  zinc  chloride  at  300°,  primary  amines  are  readily  obtained  with  small 
proportions  of  secondary  amines  :    C6H5-OH  +  NH3  =  H.,0  +  C6H5-NH2. 

(c)  By  heating  secondary  and  tertiary  bases   (substituted  amines)   with 
concentrated  hydrochloric  acid  at  180°,.  C6H5-N(CH3)2  +  2HC1  =  C6H5-NH2. 
+  2CH3C1 ;   at  higher  temperatures  the  alkyl  chloride  reacts  with  the  nucleus, 
giving  homologous  amines  higher  than  the  original  one  :    C6H5-NH2  +  CH3C1 
=  C6H4(CH3)-NH2,  HC1.   In  the  same  way,  trimethylphenylammonium  iodide 
yields  mesidine  hydriodide,  C6H2(CH3)3-NH2,  HI  (the  methyl  groups  of  the 
nucleus  never  assume  the  meto-position). 

Properties.  The  primary  monamines  are  liquid  or  solid  and  turn  brown 
in  the  air.  With  acids  they  form  crystalline  salts  soluble  in  water,  but  with 
carbonic  acid  they  do  not  give  salts,  so  that  they  may  be  liberated  from  their 
salts  by  means  of  sodium  carbonate.  With  platinum  chloride  they  form  double 
salts  (platinichlorides),  e.g.  (C6H5-NH2,  HC1)2,  PtCl4,  which  are  only  slightly 
soluble  and  serve  for  the  separation  of  these  bases. 

With  methyl  iodide  they  form  secondary,  tertiary,  and  quaternary  com- 
pounds :  C6H5-NH-CH3,  HI  -  -  C6H5-N(CH3}2,  HI  —  C6H5-N(CH3)3I ; 
the  base  can  easily  be  separated  from  the  acid  by  caustic  soda. 

Benzaldehyde  reacts  with  aniline,  forming  benzylideneaniline  :  C6H5-CHO 
+  C6H5-NH2  =  H20  +  C6H5-CH  :  N-C6H5,  while  acetaldehyde  gives  ethyli- 
denediphenyldiamine  : 

2C,H6-NH2  +  CH3-CHO  =  H2OT    6 


AROMATIC    AMINES 


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556  ORGANIC    CHEMISTRY 

The  action  of  the  organic  acids  on  amines  gives  acianilides,  which  are 
decomposable  by  alkali  : 

C6H5-NH2  +  CH,,-COOH  =  H20  +  C6H5-NH-C2HnO. 

Acotanilide 

When  heated  with  chloroform  and  alcoholic  potash,  the  primary  amines 
form  isonitriles  (carbylamines),  which  have  most  unpleasant  odours.  With 
carbon  disulphide  they  give  thioureas.  which  with  P205  give  mustard  oils  of  the 
aromatic  series. 

With  nitrous  acid  (or  nitrites)  in  acid  solution,  amines  yield  diazo-  or 
diazoamino-compounds,  these  giving  phenols  when  boiled  with  water.  Where 
the  amino-group  is  in  the  side-chain,  no  diazo-derivative  is  formed. 

Aniline,  see  later. 

2.  SECONDARY  MONAMINES 

These  are  basic  in  character,  not  when  they  are  purely  aromatic  compounds, 
but  only  when  they  contain  also  aliphatic  radicals.  These  mixed  derivatives 
are  obtained  from  primary  amines  by  treatment  with  methyl  iodide  and,  if 
the  acetylated  primary  base  is  employed,  the  simultaneous  formation  of 
tertiary  base  is  avoided  :  C6H5-NH-COCH3  +  CH3I  =  HI  +  C6H5-N(CH3) 
(COCH3)  ;  the  acetyl  group  may  be  removed  by  subsequent  hydrolysis. 

The  secondary  bases  may  be  separated  from  the  tertiary  by  means  of 
nitrous  acid  (potassium  nitrite),  with  which  the  former  yield  nitrosamines  : 
C6H5-NH-CH3  +  NO- OH  =  H20  +  C6H5-N(NO)-CH3,  which  are  neutral 
compounds,  insoluble  in  water.  When  these  nitrosamines  are  heated  with 
hydrochloric  acid  (alcoholic),  the  NO  group  passes  into  the  benzene  nucleus  : 
C6H5-N(NO)-CH3  gives  C6H4(NO)-NH-CH3. 

Pure  aromatic  secondary  monamines  are  obtained  by  heating  the  primary 
bases  with  the  corresponding  hydrochlorides  : 

C6H5-NH2  +  C6H5-NH2,  HC1  =  (C6H5)2NH  +  NH4C1. 

3.  TERTIARY  MONAMINES 

These  are  formed  by  alkylating  primary  or  secondary  bases. 

Triphenylamine  is  obtained  from  bromobenzene  by  the  action  of  dipotassio- 
aniline  :  2C6H5Br  +  C6H5-NK2  =  2KBr  +  (C6H5)3N. 

The  purely  aromatic  tertiary  monamines  are  not  basic  in  character,  and 
hence  do  not  form  salts.  They  do  not  give  isonitriles  with  chloroform,  or 
mustard  oils  with  CS2. 

With  alkyl  iodides  they  form  quaternary  compounds.  When  they  are 
treated  with  nitrous  acid,  the  NO  group  enters  the  benzene  nucleus,  this 
reaction  distinguishing  these  bases  from  the  tertiary  bases  of  the  fatty  series. 

4,  QUATERNARY  BASES 

These  are  analogous  to  the  corresponding  aliphatic  compounds.  Trimethyl- 
phenylammonium  Hydroxide,  C6H5-N(CH3)3OH,  for  example,  is  strongly 
alkaline,  colourless,  and  bitter,  and  is  decomposed  on  heating. 

5.  DIAMINES,  TRIAMINES,  TETRAMINES,  ETC. 

These  are  obtained  by  reducing  the  corresponding  nitroamino-  or  polynitro- 
derivatives  ;  thus  Tetraminobenzene  is  formed  from  dinitro-m-diaminobenzene. 

The  polyamines  give  various  reactions  with  nitroso -compounds  of  tertiary 
amines,  with  certain  azo-dyes,  &c. 

The  diamines  and  polyamines  are  solid  substances,   which  distil  unde- 


ANILINE  557 

composed  and  are  soluble  in  hot  water.  They  are  colourless,  but  turn  brown 
in  the  air  with  a  rapidity  increasing  with  the  number  of  ammo-groups  ;  they 
give  characteristic  colorations  with  ferric  chloride. 

The   ORTHODIAMINES   form  Anhydro-bases  or  Benziminazoles,   e.g. 

/NH\ 
C6H4\          >OCH3.       Further,    aldehydes    react    with    the    hydrochlorides 

|XN 

of  diamines,  forming  Anhydro-bases  or  Aldehydo-bases. 

Glyoxals   yield    Quinoxaline,    &c.,    while    nitrous    acid    gives   Azimino- 

/NH\ 
compounds,  e.g.  Aziminobenzene    (aminoazophenylene),  C6H4\          2^' 

\N^ 

m-DIAMINES  give,  with  nitrous  acid,  yellowish  brown  colouring-matters 
(Bismarck  brown :  sensitive  reaction).  With  diazobenzene  chloride  they  yield 
azo-dyes  (chrysoidin).  When  oxidised  together  with  p-diamines,  they  give  a 
blue  colour  which  becomes  red  on  boiling. 

p-DIAMINES,  when  oxidised  with  Mn02  +  H2S04,  yield  quinoiie,  C6H402, 
and  a  bomologue  with  a  peculiar  odour  ;  some  of  them  give  colouring-matters 
when  treated  with  solutions  of  hydrogen  sulphide  and  ferric  chloride. 

ANILINE  (Aminobenzene,  Phenylamine),  C6H5-NHa,  was  discovered  in 
1826  by  Unverdorbeii  among  the  products  of  the  dry  distillation  of  indigo  and 
was  called  crystalline,  since  with  acids  it  readily  formed  crystalline  masses. 
It  was-  then  found  also  by  Runge  in  1834  in  coal-tar,  and  he  named  it  kyanol 
or  blue  oil,  since  with  hypochlorite  it  gave  a  blue  coloration  and  its  salts  a  violet 
coloration. 

In  1841  Fritsche  obtained  it  by  distilling  indigo  with  potash,  and  he  termed 
it,  after  the  native  name  of  the  plant,  "  anil,"  aniline.  In  1842  Zinin  gave  the 
name  benzidam  to  the  product  obtained  by  reducing  nitrobenzene  with  ammo- 
nium sulphide.  The  identity  of  these  various  substances  and  their  true  con- 
stitution was  proved  by  Hofmann  in  1843. 

Industrially  it  is  prepared  by  treating  nitrobenzene  with  nascent  hydrogen  produced 
by  the  action  of  hydrochloric  acid  on  iron  filings  or,  better,  turnings,  as  was  proposed  in 
1864  by  Bechamp,  who  first  used  acetic  acid  in  place  of  hydrochloric  : 

C6HB.N02  +  6HC1  +  3Fe  =  C6H5.NH2  +  3FeCl2  +  2H2O. 

The  quantity  of  HC1  consumed  is,  however,  only  one-fortieth  of  the  theoretical  amount, 
so  that  after  a  certain  point  the  reduction  is  perhaps  continued  by  the  action  of  the  iron 
on  water  in  presence  of  ferrous  chloride:  2Fe  +  C6H5-N02  +  4H20  =  2Fe(OH)3  + 
C6H5.NH2.  The  apparatus  for  manufacturing  aniline  consists  of  a  cast-iron  cylinder  (the 
lower  half  is  furnished  with  a  discharge  tap  and  is  replaceable,  as  it  corrodes  rapidly) 
provided  with  a  cover,  through  which  pass  a  vertical  stirrer  worked  by  toothed  wheels 
and  a  direct-steam  coil.  The  cover  is  also  fitted  with  a  reflux  condenser  and  a  hopper  with 
a  wooden  plug  for  the  introduction  of  the  iron  turnings.  A  tube  fixed  laterally  to  the  lower 
part  of  the  reflux  condenser  carries  off  the  aniline  distilling  with  the  steam  to  a  condensing 
coil  on  one  side.  The  operation  is  carried  out  as  follows  :  300  litres  of  water,  180  kilos  of 
iron  turnings,  and  60  kilos  of  concentrated  hydrochloric  acid  are  kept  stirred  in  the  cylinder 
while  750  kilos  of  nitrobenzene  are  introduced.  The  reaction  is  started  by  a  jet  of  direct 
steam,  and  is  afterwards  maintained  by  gradually  adding  moist  iron  turnings  up  to  a  total 
quantity  of  650  kilos  ;  these  additions  are  made  over  a  period  of  6  to  7  hours  and  are 
arranged  so  that  the  mass  is  kept  hot,  but  the  reaction  is  allowed  to  calm  down  before 
fresh  iron  is  introduced.  If  the  reaction  becomes  violent,  benzene  and  ammonia  are  formed 
instead  of  aniline.  A  further  quantity  of  100  to  150  kilos  of  iron  turnings  is  added, 
nitrobenzene  evaporating  with  the  water  is  condensed  in  the  reflux  condenser.  At  the 
end  of  the  operation  the  vessel  contains  aniline,  aniline  hydrochloridc,  ferric  oxide  and 
o-  and  p-toluidines,  together  with  a  little  unaltered  nitrobenzene  and  some  impurities 
sucll  as  azobenzene,  &c.  Thick  milk  of  lime  is  then  added  until  the  reaction  is  strongly 


558  ORGANIC    CHEMISTRY 

alkaline,  and  the  mass  distilled  with  superheated  direct  steam.  The  condensed  distillate 
separates  into  two  layers,  the  lower  one  of  aniline  and  the  upper  one  of  water  containing 
2  to  3  per  cent,  of  aniline  in  suspension  or  solution  ;  this  lower  layer  is  used  in  the  reduction 
of  subsequent  quantities  of  nitrobenzene.  The  decanted  aniline  is  purified  by  distillation 
from  an  iron  still.  The  decomposition  of  the  aniline  hydrochloride  by  milk  of  lime  takes 
place  according  to  the  equation  : 

2C6H6.NH2,  HC1  +  Ca(OH)2  =  CaCl2  +  2H2O  +  2C6H6.NH2. 

A  purer  product  is  obtained  by  rectification  of  the  aniline  in  a  vacuum  apparatus. 

It  has  also  been  proposed  (Ger.  Pat.  184,809)  to  reduce  nitrobenzene  by  means  of 
sodium  bisulphite  in  the  hot. 

At  one  time  the  nitrobenzene  employed  was  obtained  from  crude  90  per  cent,  benzene 
containing  toluene,  the  resultant  product  being  a  mixture  of  aniline  and  toluidine,  which 
served  well  for  the  preparation  of  certain  dyes.  But  nowadays  it  is  often  regarded  as 
preferable  to  start  from  pure  benzene  and  pure  toluene  separately  and  to  mix  the  aniline 
and  toluidine  subsequently  in  the  required  proportions. 

Aniline  can  also  be  obtained  by  other  processes  which  have  not  yet  been  applied  on 
a  large  scale,  e.g.  by  passing  a  mixture  of  nitrobenzene  vapour  with  excess  of  hydrogen 
(or  water-gas)  over  reduced  copper  turnings,  heated  to  300°  to  400°  ;  the  copper  acts  as 
a  catalyst  and  remains  unchanged  (Ger.  Pat.  139,457).  Some  importance  is  now  being 
assumed  by  the  electrolytic  process,  according  to  which  nitro -derivatives  can  be  converted 
into  amino -derivatives  in  presence  of  metallic  salts  (e.g.  copper  salts),  which  also  separate 
at  the  cathode  (see  p.  566). 

Aniline  is  a  liquid  which  boils  at  183°  to  184°,  has  the  sp.  gr.  1-024  at  16°, 
and  solidifies  at  —  8°  (or  —  20°  if  impure).  It  is  colourless  and  refractive,  but 
becomes  brown  in  the  air  at  a  rate  increasing  with  the  proportion  of  impurities 
present.  It  is  soluble  in  alcohol,  ether,  benzene,  fatty  oils  and,  to  a  slight 
extent  (1  :  30)  in  water,  and  it  dissolves  sulphur  (in  the  hot),  phosphorus, 
camphor,  indigo,  a  little  water  (in  the  hot),  &c.  ;  it  is  readily  oxidisable.  It 
distils  easily  and  completely  in  steam,  and  its  vapour  is  somewhat  poisonous  * 
and  combustible.  As  a  base  it  is  weaker  than  ammonia  in  the  cold  but  stronger 
in  the  hot,  but  its  aqueous  solution  does  not  react  with  litmus  or  turmeric 
paper.  Although  it  is  a  weak  base,  it  precipitates  salts  of  zinc,  aluminium, 
and  iron,  and  in  the  hot  it  displaces  ammonia  from  various  salts. 

With  formaldehyde  it  gives  a  characteristic  (for  aniline  and  for  the  aldehyde) 
condensation  product,  (C6H5-  N :  CH2)3,  melting  at  40°.  With  chloride  of  lime  a 
solution  of  aniline  becomes  intensely  blue  if  pure  or  violet  if  impure  (sensitive 
reaction),  the  colour  rapidly  changing  to  brown  ;  if  the  aniline  solution  is  very 
dilute  this  coloration  does  not  appear,  but  a  red  colour  will  then  form  on  further 
addition  of  a  few  drops  of  ammonium  hydrosulphide,  minimal  traces  (1  :  250,000) 
of  aniline  being  thus  detectable.  Aniline  or  one  of  its  salts  forms  p -amino - 
benzenesulphonic  acid  with  concentrated  sulphuric  acid,  but  in  presence  of  a 
drop  of  potassium  dichromate  solution  a  fine  blue  colour  is  produced  which 
disappears  very  rapidly  ;  in  dilute  solution  a  green  and  then  a  black  colour 
(aniline  black)  is  formed.  Different  methods  of  oxidising  aniline  give  varied 
products  :  azobenzene,  nitroso-  and  nitro-benzene,  /3-phenylhydroxylaniine, 
p-aminophenol,  quinone,  p-aminophenylamine,  violaniline  (with  arsenic  acid). 
Oxidation  of  a  mixture  of  aniline  and  toluidine  yields  fuchsine,  while  a  mixture 
of  aniline  and  p-diamine  gives  safranine.2  Chlorine  transforms  dry  aniline  into 

1  Aniline  acts  on  the  nervous  system,  and  even  when  its  action  is  slight  the  edges  of  the  lips  are  turned  bluish 
and  an  effect  similar  to  drunkenness  is  produced,  but  the  face  becomes  pale  and  the  appetite  fails  ;  in  such  cases 
Epsom  salts  are  administered  as  purgative,  alcoholic  liquors  being  harmful.  Clothes  soaked  in  aniline  may 
produce  serious  poisoning,  the  lips  becoming  dark  blue  or  even  black,  and  giddiness  so  acute  as  to  cause  collapse 
When  this  happens,  recourse  should  be  had  to  excitants  or  ablution  or  to-  small  doses  of  ether  administered 
internally.  Benzene  and  nitrobenzene  vapours  are  also  injurious  to  health. 

For  the  making  of  aniline  black  and  other  dyes,  the  following  qualities  of  aniline  are  placed  on  the  market 
aniline  oil  for  Hue,  which  is  almost  pure  aniline,  b.pt.  182°  to  186°,  sp.  gr.  1-034  to  1-036  ;   aniline  oil  for  red,  con 
sisting  of  about  1  part  of  aniline  and  2  parts  of  o-  and  p-toluidines  and  boiling  at  190°  to  198°  ;   aniline  oil  for 
stfranine~'sj>.  gr.  1-032  to  1-034,  containing  35  to  50  per  cent,  of  aniline  and  50  to  65  per  cent,  of  o-toluidine 
Aniline  oil  is  tested  commercially  by  measuring  the  fractions  distilling  at  different  temperatures  from  100  grins- 


ANILINE    DERIVATIVES  559 

a  tarry  substance,  while  in  presence  of  water  trichJoraniline  and  trichlorophenol 
are  formed.  The  action  of  calcium  hypochlorite  on  a  solution  of  aniline  in 
chloroform  yields  azobenzene. 

In  1909  Germany  imported  639  quintals  of  aniline  and  exported  78,835  quintals 
(70,452  in  1908).  According  to  the  official  statistics,  Italy  imported  the  following 
quantities  of  aniline  oil  and  salt :  426  quintals  in  1908  ;  577  in  1909  ;  3695,  of  the  value 
of  £20,680,  in  1910.  But  these  figures  are  obviously  inaccurate,  and  private  information 
shows  that  the  Italian  consumption  (nearly  all  imported)  must  exceed  8000  quintals 
per  annum,  one-half  of  this  being  aniline  salt  (hydrochloride)  and  the  other  oil.  In  1911 
England  exported  aniline  and  toluidine  oils  to  the  value  of  £39,814. 

Chemically  pure  aniline  costs  2*.  to  4s.  per  kilo  ;  aniline  oil  for  blue  and  for  black  costs 
104s.  to  112s.  per  quintal,  and  that  for  red  120s.  to  152s.  ;  lower  prices  than  these  some- 
times prevail.  Aniline  salt  costs  about  10s.  less  per  quintal  than  the  oil.  There  is  no  import 
duty  on  the  oil  or  salt  in  Italy. 

Some  of  the  more  important  salts  and  derivatives  of  aniline  and  its  homologues  are 
as  follow  : 

ANILINE  HYDROCHLORIDE  (Aniline  Salt),  C6H5-NH2,  HC1,  is  obtained  pure  and 
dry  in  white  crystals  by  passing  a  current  of  dry  hydrogen  chloride  into  an  ethereal  solu- 
tion of  aniline.  It  melts  at  198°  and  partly  sublimes,  and  boils  unchanged  at  245°  ;  it 
dissolves  readily  in  water  or  alcohol,  but  is  insoluble  in  ether.  For  price,  see  above. 

It  is  prepared  industrially  by  neutralising  aniline  at  100°  with  concentrated  hydro- 
chloric acid,  free  from  chlorine.  After  standing  for  some  days,  crystalline  aniline  salt 
separates  out,  this  being  centrifuged  and  dried  at  50°  ;  the  mother- liquors  are  then  evapo- 
rated and  crystallised.  In  the  air  the  white  scales  assume  a  reddish  or  greenish  tint.  In 
presence  of  HC1  its  aqueous  solution  imparts  a  yellow  colour  to  pine-wood  or  elder-pith. 

ANILINE  SULPHATE,  (C6H5.NH2)2,  H2SO4,  is  only  slightly  soluble  in  water. 

Various  other  salts  of  organic  and  inorganic  acids  are  known. 

ANILINE  PLATINICHLORIDE,  (C6H6-NH2,  HC1)2,  PtCl4,  forms  yellow  leaflets 
dissolving  readily  in  water  and,  to  a  less  extent,  in  alcohol. 

METHYLANILINE,  C6H5-NH-CH3,  is  obtained  by  heating  aniline  hydrochloride 
with  methyl  alcohol  (free  from  acetone)  at  200°  in  an  enamelled  iron  autoclave.  It  is  a 
colourless  liquid,  sp.  gr.  0-976  at  15°,  b.pt.  191°,  with  an  odour  resembling,  but  stronger 
than,  that  of  aniline.  With  chloride  of  lime  it  gives  first  a  violet  and  then  a  brown  colora- 
tion. The  corresponding  nitrosamine,  C6H6-NO-CH3,  is  obtained  by  methylating  phenyl- 
nitrosamine  or  by  treating  methylaniline  with  nitrous  acid.  It  forms  a  yellow  oil  which 
distils  unchanged  only  in  a  current  of  steam  and  gives  Liebermann's  reaction,  characteristic 
of  the  nitrosamines  and  of  various  nitroso -derivatives  ;  this  reaction  consists  in  the  forma- 
tion of  a  dark  blue  coloration  when  the  nitroso -compound  is  heated  with  phenol  and 
sulphuric  acid  and  the  liquid  then  diluted  with  water  and  neutralised  with  potash. 

DIMETHYLANILINE,  C6H5-N(CH3)2,  is  a  mixed  tertiary  amine  and  is  obtained 
by  heating  aniline  hydrochloride  with  methyl  alcohol,  methyl  chloride  being  formed  as  an 
intermediate  product  and  reacting  with  the  aniline.  If,  however,  dimethylaniline  hydro - 
chloride  is  heated  with  gaseous  hydrogen  chloride  at  180°,  methyl  chloride  and  aniline 
are  formed.  When  dimethylaniline  is  heated  to  a  high  temperature,  the  alkyl  groups  pass 
into  the  nucleus.  The  hydrogen  in  the  para-position  of  these  dialkylamines  is  readily 
replaceable  by  different  groups  ;  thus,  the  action  of  nitrous  acid  yields  p-nitrosodimethyl- 
aniline,  which  forms  green  crystals  and  gives  a  yellow  hydrochloride.  Permanganate 
converts  the  NO  group  into  NO2,  giving  nitrodimethylaniline  (m.pt.  162°),  while  boiling 
with  caustic  soda  results  in  the  elimination  of  dimethylamine  and  the  formation  of  nitroso- 
phenol,  NO-C6H4-OH.  It  gives  a  straw-yellow  coloration  with  chloride  of  lime  and  reacts 
with  aldehydes  and  various  other  compounds. 

DIPHENYLAMINE,  C6H5.NH-C6H5,  is  obtained  by  heating  aniline  with  its  hydro- 
chloride  : 

C6H5.NH2,  HO  +  C6H5.NH2  =  NH4C1  +  C6H5.NH.C6H5. 

of  the  oil  in  a  suitable  distilling  flask  fitted  with  a  thermometer  graduated  in  fifths  of  a  degree  from  150°  to  225° 
the  heating  being  carried  out  on  a  sand-bath.  The  best  qualities  of  aniline  oil  give  95  to  98  per  cent  of  distillate 
between  182°  and  185°.  It  is  also  advisable  to  make  small  dyeing  tests  with  aniline  black  in  order  to  ascertain 
which  of  the  different  aniline  oils  and  salts  on  the  market  gives  the  finest  and  most  intense  black  (tee  later,  Dyeing 
Proce'ieg). 


560 

It  melts  at  54°  and  boils  at  310°,  and  forms  a  very  sensitive  reagent  for  the  detection  of 
traces  of  nitric  acid,  with  which,  in  presence  of  concentrated  sulphuric  acid,  it  gives  an 
intense  blue  coloration  (also  given  with  nitrous  acid  and  various  oxidising  agents  ;  see 
Detection  of  Nitrates  in  Water,  voL  i,  p.  214). 

Various  nitro-  and  nitroso-derivatives  are  known,  as  well  as  triphenylamine,  N(C6H5)3, 
which  crystallises  in  large  plates  melting  at  127°  and  distils  unchanged. 

BENZYLANILINE  (Benzylphenylamine),  C6H5-CH2.NH.C6H5,  is  obtained  either 
by  heating  benzyl  chloride  (1  mol.)  with  aniline  (2  mols.)  or  by  reducing  thiobenzanilide, 
u6H6.CS-NH-C6H5.  It  forms  crystals  melting  at  33°  and  boils  at  310°. 

ANILIDES  are  derivatives  of  aniline  in  which  one  or  both  of  the  hydrogen  atoms  of 
the  amino-group  of  aniline  are  replaced  by  one  or  two  inorganic  or  organic  acid  residues  ; 
in  the  latter  case,  compounds  of  considerable  interest  are  formed. 

ACETANILIDE  (Antifebrin),  C6H5-NH-COCH3,  is  obtained  by  boiling  a  mixture  of 
aniline  and  glacial  acetic  acid  for  a  couple  of  days  in  an  earthenware  vessel  fitted  with  a 
reflux  condenser  : 

C6H6.NH2  +  CHg-CO-OH  =  H20  +  C6H5.NH.COCH3. 

It  is  purified  by  repeatedly  crystallising  or  distilling,  best  in  vacua.  It  melts  at  113°,  boils 
at  295°,  and  dissolves  in  174  parts  of  cold  or  18  parts  of  boiling  water  or  in  3^  parts  of 
alcohol  ;  it  is  readily  soluble  in  ether  or  chloroform.  The  hydrogen  atom  united  to  nitrogen 
can  be  replaced  by  metals  (Na,  K,  &c.).  It  causes  considerable  lowering  of  the  temperature 
of  animal  organisms,  and  is  hence  used  as  an  antipyretic.  It  costs  about  2s.  6d.  per  kilo. 

Di-  and  Tri-acetanilides  have  analogous  properties,  and  Methylacetanilide, 
C6H5-N(CH3)'COCH3,  is  used  under  the  name  of  exalgin  as  a  specific  against  headache. 

PHENYLSULPHAMINIC  ACID,  C6H5-NH-SO3H,  is  obtained  by  the  action  of 
sulphur  trioxide  on  the  amine,  and  is  very  unstable  except  in  the  form  of  salts. 

CHLORACETANILIDE,  C6H4Q.NH-COCH3,  exists  in  three  isomeric  forms:  the 
or tho -compound,  melting  at  88°  ;  the  meta-,  at  72-5°  ;  and  the  para-,  at  172°.  The  chloro- 
and  bromo -derivatives  of  acetanilide  and  other  anilides  are  obtained  by  the  action  of 
chlorine  or  bromine  on  the  anilide  or  by  the  interaction  of  acctyl  chloride  and  the  substi- 
tuted anilines.  Another  series  of  isomerides  is  that  in  which  the  substitution  is  in  the  acid 
group,  e.g.  Phenylchloracetamide,  C6H5  •  NH  •  CO  •  CH2C1  (m.pt.  134°),  which  is  obtained 
froni  chloracetyl  chloride  and  aniline.  Phenyldichlor-  (m.pt.  118°)  and  phenyltrichlor- 
acetamide  (m.pt.  82°)  are  also  known. 

NITRACET ANILIDE,  NO2-C6H4-NH-COCH3.  The  three  isomerides  are  obtained 
by  the  action  of  acetyl  chloride  on  the  corresponding  nitranilines  ;  the  o-compound  melts 
at  92°  (yellowish  crystals),  the  m-  at  142°,  and  the  p-  at  207°. 

PHENYLACET  ANILIDE  (Diphenylacetamide),  (C6H5)2N-CO-CH3,  is  obtained  by 
treating  a  benzene  solution  of  diphenylamine  with  acetyl  chloride  ;  it  melts  at  99-5°. 

BENZANILIDE  (Phenylbenzamide),  CGH5.NH.c6c6H5,  is  prepared  from  benzoyl 
chloride  and  aniline  and  melts  at  162°.  It  is  very  stable,  but  is  decomposed  by  fusion  with 
alkali.  It  is  insoluble  in  water,  but  dissolves  in  alcohol. 

PHENYLGLYCOCOLL (Phenylaminoacetic or  Anilidoacetic  Acid),  C6H5.NH-CH2- 
CO2H,  is  obtained  by  protracted  heating  of  chloroacetic  acid  (1  mol.)  and  aniline  (2  mols.) 
with  water.  It  forms  crystals  melting  at  127°,  gives  characteristic  mercury  and  copper  salts, 

,CH2 
and  when  heated  at  150°  gives  up  water  and  yields  the  anhydride  C6H5  •  N\   |       ,  melting  at 

XCO 
263°. 

HOMOLOGUES   OF   ANILINE,   POLYAMINES,    AND  THEIR   DERIVATIVES 

(see  Table,  p.  555) 

ORTHO-  and  PARA-TOLUIDINES,  CH3.C6H4-NHo,  are  obtained  by  reducing 
the  corresponding  nitro -com  pounds.  Since  the  three  isomerides  are  formed  simultaneously 
in  the  nitration  of  toluene,  reduction  yields  a  mixture  of  the  three  toluidines  (m-toluidine 
in  small  amount).  In  order  to  separate  them,  the  mixture  is  poured  into  a  solution  of 
oxalic  acid  containing  hydrochloric  acid  and  the  liquid  heated  to  boiling  ;  the  p-toluidine 
oxalate,  which  is  only  slightly  soluble  in  water  and  insoluble  in  ether,  is  then  separated, 
the  filtrate  containing  the  soluble  hydrochlorides  of  tho  other  toluidines.  Also  Wiilfing 


PHENYLENEDIAMINES  561 

has  shown  that  only  amines  which  have  the  para-position  free  can  be  converted  (by  HC1  + 
NaNO2)  into  the  corresponding  aminoazo-derivatives,  the  unaltered  p-toluidine  being 
then  separable  by  distillation  in  steam.  p-Toluidine  can  also  be  separated  by  cooling,  since 
it  freezes  first.  The  toluidines  are  distinguished  from  aniline  by  the  different  solubilities 
of  the  nitrates,  hydrochlorides,  and  acetyl-derivatives.  p-Toluidine,  like  the  meta-com- 
pound,  costs  double  as  much  as  the  ortho-isomeride.  o-Toluidine,  which  is  also  found  in 
coal-tar,  is  a  liquid  (sp.  gr.  1-09)  boiling  at  199°  and  turning  brown  in  the  air.  p-Toluidine 
is  a  solid  melting  at  43°,  and  boils  at  198°  ;  it  is  sparingly  soluble  in  cold  water,  but  dis- 
solves readily  in  alcohol,  ether,  or  benzene.  The  toluidines  are  used  in  the  manufacture  of 
dyes. 

m-TOLUIDINE    is    obtained    indirectly    by   nitrating   acetylated    p-toluidine,    the 

compound   CH3/  \NH-COCH3  being  thus  formed  ;  the  acetyl-group  is  then  elimi- 

~N02 

nated  by  boiling  with  hydrochloric  acid  and  the  amino-group  by  diazotisation.  Reduction 
of  the  resultant  m-nitrotoluene  yields  m-toluidine,  which  is  a  colourless  oil  (sp.  gr.  0-998 
at  25°)  boiling  at  197°.  The  crude  product  costs  4s.  per  kilo  and  the  pure  ten  times  as  much. 

XYLIDINES.  Six  isomerides  are  known  (see  Table,  p.  555),  and  all  are  formed  together 
by  nitrating  crude  xylene  and  reducing  the  resulting  nitro -compounds  ;  the  most  im- 
portant is  m-xylidine.  Various  methods  of  separating  the  different  xylidines  are  known, 
almost  all  of  them  being  patented  and  based  on  the  varying  solubilities  of  the  acetates 
and  hydrochlorides  of  p-  and  m-xylidines.  The  separate  isomerides  are  prepared  pure 
from  the  corresponding  pure  nitro-compounds. 

BENZYL AMINE,  C6H5-CH2-NH2,  is  isomeric  with  the  toluidines  and  behaves  like 
the  amines  of  the  aliphatic  series.  It  is  obtained  together  with  di-  and  tri-benzylaminc 
by  heating  benzyl  chloride  with  ammonia.  It  is  a  colourless  liquid  of  ammoniacal  odour 
and  boils  at  185°  ;  it  has  an  alkaline  reaction  and  is  a  more  energetic  base  than  aniline, 
the  amino-group  being  further  removed  from  the  benzene  nucleus,  which  has  a  somewhat 
negative  (acid)  influence. 

PHENYLENEDIAMINES,  C6H4(NH2)2,  are  obtained  by  reducing  the  corresponding 
dinitrobenzenes  or  nitroanilines  with  iron  and  hydrochloric  acid.  m-Phenylenediamine  is 
also  obtained  by  electrolysing  m-nitroaniline  in  aqueous  saline  solution  in  presence  of  a 
cathode  of  copper  or  of  powdered  copper  (Ger.  Pat.  131,404).  It  forms  acicular  crystals 
melting  at  63°,  boils  at  287°,  and  readily  undergoes  change  in  the  air  ;  its  hydrochloride  is, 
however,  stable.  It  is  used  in  the  manufacture  of  dyes  and  also  as  a  reagent  for  detecting 
traces  of  nitrous  acid,  with  which  it  forms  a  brownish  yellow  coloration  (Bismarck  brown), 
p-Phenylenediamine  is  obtained  by  the  reduction  of  aminoazo benzene  (dissolved  in  aniline) 
with  hydrogen  sulphide,  or,  more  easily,  by  heating  p-dichlorobenzene  or  p-chloraniline 
with  ammonia  in  presence  of  a  copper  salt  (Ger.  Pat.  204,408).  It  melts  at  147°,  boils  at 
267°,  and  forms  crystals  which  are  soluble  in  water  and  blacken  a  little  in  the  air  ;  when 
pure  it  costs  40s.  per  kilo,  the  commercial  product  being  sold  at  about  14s.  As  well  as  for 
making  dyes,  it  is  frequently  employed  for  dyeing  hair  by  oxidising  it  with  hydrogen 
peroxide,  but  its  use  for  this  purpose  should  be  .prohibited  owing  to  its  poisonous  properties 
(see  below,  p-Tolylenediamine).  Its  asymmetric  dimethyl-derivative,  NH2.C6H4-N(CH3)2, 
is  used  in  presence  of  ferric  chloride  to  detect  traces  of  hydrogen  sulphide  (methylene  blue 
being  formed). 

o-Phenylenediamine  is  of  no  practical  importance. 

Commercial  m-phenylenediamine  costs  about  6s.  and  its  hydrochloride  7s.  per  kilo, 
the  pure  products  costing  about  six  times  as  much. 

TOLYLENEDIAMINES,  C6H3(CH3)(NH2)2.  The  most  common  of  these  is  the  o  :  p- 
compound,  i.e.  the  one  with  the  amino-groups  in  the  2  and  4  positions  and  the  methyl 
group  in  the  position  1.  It  is  obtained  by  reducing  the  corresponding  din itro toluene  (see 
p.  550)  with  iron  and  hydrochloric  acid  and  is  used  for  making  dyes  and,  together  with 
sodium  sulphite,  for  dyeing  hair,  as  it  does  not  seem  to  be  injurious  to  health,  as  p-phenylene- 
diamine  is.  It  costs  about  16s.  per  kilo. 

NITROANILINES.  Concentrated  nitric  acid  acts  very  energetically  on 
aniline,  and  in  order  that  the  nitro-groups  may  be  introduced  into  the  benzene 
nucleus  without  the  amino-group  being  attacked,  either  the  ammo  group  is 
acetylated  or  the  nitration  is  carried  out  in  presence  of  a  large  proportion  of 


562  ORGANIC    CHEMISTRY 

concentrated  sulphuric  acid.  In  the  former  case,  ortho-  and,  to  a  still  greater 
extent,  para-Nitroacetanilide,  N02-C6H4-NH-C2H30,  are  obtained,  the  acetyl 
group  being  then  removed  by  hydrolysis  with  HC1  or  KOH  ;  in  the  second 
case  a  mixture  of  m-  and  p-nitroanilines,  together  with  a  little  of  the  ortho- 
compound,  are  obtained.  The  ortho-  and  meta -derivatives  distil  unchanged 
in  steam.  Boiling  with  alkali  results  in  the  elimination  of  the  amino-groups 
and  the  formation  of  nitrophenols. 

PICRAMIDE,  (NO2)3C6H2-NH2,  is  a  yellow  substance  melting  at  188°  ;  on 
hydrolysis  it  gives  picric  acid. 


H.  NITROPHENOLS,  AMINOPHENOLS 

NITROPHENOLS.  The  ortho-  and  para -compounds  are  obtained  mixed 
by  treating  phenol  with  dilute  nitric  acid,  a  larger  proportion  of  the  para- 
derivative  being  formed  in  the  cold  and  of  the  ortho-  in  the  hot.  The  latter 
is  volatile  in  steam,  and  can  hence  be  readily  separated  from  the  former. 

m-Nitroaniline  gives  m-nitrophenol  only  by  passing  through  the  diazo- 
compound,  but  o-  and  p-nitroanilines  give  the  corresponding  nitrophenols 
when  simply  fused  with  potash. 

Nitrophenols  are  more  markedly  acid  than  the  phenols  and  decompose  the 
alkali  carbonates,  forming  Nitrophenoxides. 

_N02 

PICRIC  ACID  (Trinitrophenol),  N02^         /OH,    was  discovered  in  1771 

~N02 

by  Amato  di  Welter,  but  was  first  used  as  a  dye  and  much  later  as  an 
explosive.  It  is  formed  by  the  action  of  concentrated  nitric  acid  on  various 
substances,  such  as  silk,  wool,  indigo,  &c.,  and  by  the  oxidation  of  s-trini- 
trobenzene  with  potassium  ferricyanide.  Further  nitro-groups  cannot  be 
introduced  directly  into  picric  acid. 

It  is  prepared  industrially  as  follows  :  equal  weights  of  sulphuric  acid  (66°  Be.)  and 
pure  phenol  are  heated  at  120°  in  a  cast-iron  vessel  and  continually  stirred  until  a  small 
portion  of  the  mass  dissolves  in  water  without  separation  of  phenol.  The  phenolsulphonic 
acid  thus  obtained  is  poured  into  two  parts  of  cold  water  and  the  solution  introduced 
gradually  into  earthenware  jars  containing  65  per  cent,  nitric  acid  (sp.  gr.  1-400)  in  the 
proportion  of  3-5  parts  per  1  part  of  phenol.  The  jars  are  surrounded  by  a  water-bath 
and  are  covered  over  so  that  the  nitrous  fumes,  which  are  at  first  freely  evolved,  may  be 
drawn  off.  Towards  the  end  of  the  reaction  the  water-bath  is  heated  to  boiling.  The  stages 
of  the  process  are  represented  by  the  following  equations  : 

(1)  C6H5-OH  +  H2SO,t  =  H20  +  OH-C6H4-S03H  ; 

(2)  OH-C6H4-SO3H  +  3HNO3  =  2H20  +  H2SO4  +  OH-C6H2(N02)3. 

When  the  mass  is  cool  it  solidifies,  and  it  is  then  centrifuged  and  washed  with  a  little 
water  ;  by  this  means  the  picric  acid  crystals  can  be  efficiently  separated  from  the  mother- 
liquor.  The  acid  can  also  be  prepared  by  the  following  process,  the  details  of  which  are 
kept  secret  by  the  various  manufacturers :  To  pure  crystallised  phenol  (m.pt.  40°),  fused 
in  a  number  of  pear-shaped  retorts  by  means  of  indirect  steam,  is  added  a  mixture  of 
nitric  and  sulphuric  acids  in  proportions  varying  in  different  works.  When  the  reaction 
is  finished,  the  clots  of  picric  acid  formed  are  fused  and  allowed  to  fall  into  a  trough  con- 
taining cold  water,  with  which  they  are  kept  stirred,  the  water  being  repeatedly  renewed 
until  washing  is  complete.  The  crystallised  picric  acid  is  centrifuged,  again  melted  and 
run  into  cold  water,  the  size  of  the  yellow  scales  separating  out  increasing  with  the  tem- 
perature of  the  fused  acid  ;  the  crystals  are  then  centrifuged,  spread  out  on  tables,  and 
dried  in  a  current  of  air  at  40°  to  60°. 


PICRIC    ACID  5C3 

A  suggestion  has  been  made  to  prepare  picric  acid  in  the  cold,  as  follows  (Fr.  Pat. 
345,441) :  1  part  of  crude  phenol  is  stirred  into  a  mixture  of  10  parts  of  nitric  acid  (sp.  gr. 
1-4)  with  3  parts  of  denatured  alcohol,  the  mass  being  poured  into  hot  water  at  the  end 
of  the  reaction  ;  the  yield  is  good,  but  part  of  the  alcohol  is  oxidised  and  lost.  When  phenol 
is  dear,  aniline  is  sometimes  used,  being  converted  into  the  sulphonic  acid,  diazotised, 
and  treated  with  the  theoretical  quantity  of  nitric  acid  (Ger.  Pat.  125,096). 

Properties.  Picric  acid  forms  yellowish,  very  bitter,  and  somewhat  poisonous 
leaflets,  which  melt  at  122'5°  and  have  the  sp.  gr.  1-7635  or,  in  the  fused  state, 
1-62.  It  burns  without  exploding,  but  if  it  is  heated  in  a  closed  vessel,  or  if 
its  vapour  is  superheated,  it  may  explode  with  great  violence.  .  In  the  open, 
mercury  fulminate  is  not  able  to  explode  it,  a  detonator  of  dry  guncotton 
(or  lead  picrate)  with  a  mercury  fulminate  cap  being  necessary.  When  it  is 
exploded  in  a  closed  vessel,  its  shattering  effect  is  double  that  of  dynamite. 

One  hundred  parts  of  water  dissolve  O626  part  of  picric  acid  at  5°,  1-161 
part  at  15°,  1'225  part  at  20°,  or  3' 89  parts  at  77°.  It  is  readily  soluble  in 
alcohol,  and  benzene  dissolves  8  to  10  per  cent,  of  it  at  the  ordinary  tempera- 
ture. In  aqueous  solution  it  is  dissociated  to  some  extent  and  shows  a  marked 
acid  action.  The  yellow  colour  of  its  aqueous  solution  is  due  to  the  anion  ;  in 
light  petroleum  it  gives  a  colourless  solution,  and  is  hence  noil -ionised. 

It  is  non-volatile  in  steam.  Its  hydroxyl-group  is  highly  reactive,  owing 
to  the  presence  of  the  three  nitro -groups.  The  potassium  and  ammonium  salts 
are  exploded  by  percussion,  whilst  the  free  acid  requires  a  detonator. 

With  many  aromatic  hydrocarbons  it  forms  well-crystallised,  molecular 
compounds  which  serve  for  the  identification  and  separation  of  the  hydro- 
carbons ;  picric  acid  is  eliminated  from  these  compounds  by  ammonia. 

With  potassium  cyanide  it  gives  a  characteristic  and  sensitive  coloration  (isopurpuric 
acid).  With  nitron  acetate  it  gives  a  precipitate  of  nitron  picronitrate,  C2oH16N4, 
C6H3O(N02)3,  which  is  insoluble  in  extremely  dilute  aqueous  solutions  acidified  with 
sulphuric  acid,  and  can  be  filtered  off,  washed  with  water,  dried  at  110°,  and  weighed. 

N=C v 


NITRON  has  the  structure 


N-C6H6       J>N-C6H5,  and  in  presence  of  acetic  acid 


C6H5-N— CH— 
precipitates  N03  ions  from  very  dilute  solutions  even  when  nitrites  are  also  present. 

The  decomposition  of  picric  acid  on  explosion  has  not  been  thoroughly 
investigated,  but  is  represented  approximately  by  the  equation  : 

C6H2(OH)(N02)3  =  6CO  +  H20  +  3N  +  H  ; 

the  acid  is  hence  too  poor  in  oxygen  to  give  the  maximum  effect,  the  carbon 
monoxide  and  hydrogen  not  being  oxidised. 

Uses.  Picric  acid  is  employed  in  the  preparation  of  certain  organic  compounds  and 
was  at  one  time  used  for  dyeing  silk  and  wool  yellow,  but  the  colour  is  not  very  stable. 
It  is  now  mostly  used  as  an  explosive,  either  as  acid  or  in  the  form  of  ammonium  or  potas- 
sium salt,  these  exploding  at  310°  or  on  percussion  (see  Explosives,  pp.  215  et  seq.).  Melinite, 
a  very  powerful  explosive  suggested  by  Turpin  for  filling  grenades,  is  merely  picric  acid 
which  has  been  fused  in  a  tinned  vessel  ;  it  is  poured  into  the  empty  grenade,  the  interior 
of  which  is  also  tinned. 

From  ammonium  picrate  and  ammonium  salts  of  trinitrocresol,  sometimes  with  addition 
of  potassium  nitrate,  powerful  and  stable  explosives  are  obtained,  these  bearing  various 
names  (lyddite,  ecrasite,  &c.). 

In  1905  Germany  produced  10,350  quintals  of  picric  acid  (at  £9  per  quintal)  for  export 
alone. 

AMINOPHENOLS,  NH2-CfiH4-OH,  are  crystalline,  colourless  substances, 
which  turn  brown  and  resinify  in  the  air.  They  are  formed  by  reducing 


564  ORGANIC    CHEMISTRY 

nitrophenols  and  form  salts  only  with  acids.  p-Aminophenol,  melting  at  183°, 
.  is  obtained  by  electrolytic  reduction  of  nitrobenzene  in  acid  solution ;  it  is 
stable  in  a  solution  of  sodium  sulphite  and  is  used  thus  as  a  photographic 
developer  under  the  name  rodinal.  Methyl-p-aminophenol,  or  metol,  also 
serves  as  a  developer. 

Aromatic  photographic  developers  (see  vol.  i,  p.  800)  should  contain  several 
hydroxyl-  or  ammo-groups,  or  at  least  one  group  of  each  kind  ;  if  the  hydrogen 
of  the  hydroxyl-  and  amino -groups  is  partly  replaced,  the  compounds  lose 
their  developing  properties,  unless  some  of  these  groups  remain  unchanged. 

AMINO ANISOLES  (Anisidines),  NH2-C6H4-OCH3,  and  Phenetidines,  NH2.C6H4. 
OC2H5,  are  used  in  making  azo-dyes  and  are  similar  to  aniline.  Glacial  acetic  acid  yields,  for 
example,  PHENACETIN  (Acetyl-p-phenetidine),  CH3.(X).NH.C6H4.OC2H5,  Phenetole 
being  C6H5-OC2H5.  Phenacetin  is  used  as  an  antipyretic  and  antineuralgic  and  forms 
colourless  and  tasteless  white  crystals,  m.pt.  135°,  which  are  soluble  in  alcohol  and  slightly 
so  in  water.  It  costs  about  6s.  per  kilo. 

DIAMINOPHENOL  (1  :  2  :  4)  is  obtained  from  the  dinitrophenol  and  forms  the  photo- 
graphic developer,  amidol  (see  above). 

DIHYDROXYDIAMINOARSENOBENZENE  is  the  product  prepared  by  Ehrlich 
and  Bertheim  as  hydrochloride  and  placed  on  the  market  in  1910  under  the  name  salvarsan 
or  606.  It  is  a  straw-yellow  powder,  dissolving  in  water  to  an  acid  solution,  and  it  contains 
34  per  cent,  of  arsenic.  It  also  bears  the  name  Hata,  since  it  was  Dr.  Hata,  of  the  Ehrlich 
Institute,  who  first  injected  it  into  animals  and  found  it  to  be  highly  efficacious  in  cases 
of  syphilis  in  rabbits,  who  were  able  to  withstand  a  certain  dose  of  the  preparation.  It 
was  applied  to  man  by  Alt  in  the  case  of  a  syphilitic  paralytic,  and  was  subsequently  largely 
used  with  success  by  Iversen. 

Salvarsan  is  a  specific  remedy  for  syphilis,  the  spirochetes  being  killed  in  24  to  48  hours 
and  the  syphilitic  symptoms  disappearing  rapidly  even  where  treatment  with  mercury  or 
iodine  is  without  effect.  The  cure  seems,  however,  to  be  very  painful,  relapse  and  secondary 
effects  sometimes  occurring.  The  firm  of  Meister,  Lucius  und  Briining  (Hochst,  near 
Frankfort),  who  make  salvarsan,  sold  a  million  pounds'  worth  of  it  in  1911. 

THIOPHENOL  (Phenyl  Hydrosulphide),  C6H5-SH,  is  obtained  by  heating  phenol 
with  phosphorus  pentasulphide  or  by  reducing  benzenesulphonic  chloride,  C6H5-S02C1. 
It  is  a  liquid  of  very  unpleasant  odour  and  exhibits  the  characters  of  the  mercaptans. 

It  readily  forms  salts,  that  of  mercury,  (C6H5S)2Hg,  for  example,  crystallising  in  needles. 
When  oxidised  in  ammoniacal  solution,  thiophenol  yields  Phenyl  Bisulphide,  (C6H5)2S2, 
melting  at  60°. 

Phenyl  Sulphide,  (C6H5)2S,  is  obtained  from  thiophenol  and  diazobenzene  chloride, 
and  has  an  alliaceous  odour. 

AMINOTHIOPHENOLS,  NH2-C6H4-SH.     The  ortho-compound  readily  forms  con- 

/Nv 

densation  products  of  the  type  C6H4<'        /CH,  or  of  greater  complexity,  such  as  primu- 

NgK 

line  (a  yellow  dye  diazotised  on  the  fibre),  which  is  obtained  by  heating  p-toluidine  with 
sulphur  and  then  sulphonating.  When  heated  with  sodium  sulphide  and  sulphur,  p-amino- 
phenol  yields  Vidal  black,  which  colours  cotton  in  an  alkaline  and  reducing  bath  of  sodium 
sulphide.  The  black  thus  obtained  is  brilliant  and  stable,  like  most  of  these  sulphur  dyes. 
PHENOLSULPHONIC  ACID,  OH-C6H4-SO3H,  is  obtained  from  phenol  and  con- 
centrated sulphuric  acid  or,  better,  from  benzenesulphonic  acid.  The  ortho-  and  para- 
compounds  are  preferably  form  3d,  and  the  former  is  transformed  into  the  latter  on  heating. 
The  meta -derivative  is  prepared  indirectly.  The  ortho -compound  is  used  as  an  antiseptic 
under  the  name  sozolic  acid  or  aseptol. 


AZO-DERIVATIVES 

I.  AZO-,  DIAZO-,  AND   DIAZOAMINO-COMPOUNDS  AND 

HYDRAZINES 
1.   AZO-DERIVATIVES 

These  are  intermediate  reduction  products  of  nitro -compounds  and  contain 
a  characteristic  group  of  two  nitrogen  atoms,  each  of  which  is  united  to  an 
aromatic  group. 

In  acid  solution  hydrogen  reduces  nitro-derivatives  directly  to  aromatic 
amines,  but  in  alkaline  solution  two  benzene  nuclei  condense  and  become 
joined  by  two  nitrogen  atoms.  In  this  way  the  following  compounds  can  be 
obtained  from  nitrobenzene  :  (1)  Azoxybenzene,  C6H5-N  —  N-C6H5;  (2)  Azo- 

\0/ 

benzene,  C6H,,-N  :  N-C6H5  ;  (3)  Hydrazobenzene,  CCH5-NH-NH-CCH5. 
Reduction  of  nitrobenzene  with  zinc  dust  in  neutral  solution  yields  Phenyl- 
hydroxylamine,  CGH5-NH-OH. 

When  aliphatic  amines  are  oxidised,  the  alkyl  groups  are  detached  in  the 
form  of  acids  and  ammonia  is  generated,  but  the  aromatic  amines  yield 
important  intermediate  compounds,  e.g.  azoxy-derivatives. 

AZOBENZENE  (Benzeneazobenzene),  C6H5-N :  N-C6H5,  is  obtained  by  reducing 
nitrobenzene  with  a  solution  of  stannous  chloride  in  excess  of  potassium  hydroxide  or  by 
distilling  azoxybenzene  with  iron  filings.  It  forms  orange-red  crystals  melting  at  68°  and 
boils  at  295°  without  decomposition  ;  it  is  insoluble  in  water  and  is  volatile  in  steam.  On 
reduction  in  acid  solution  it  yields  benzidine  : 


NH/ 

Higher  homologues,  such  as  Azotoluene,  are  also  known. 

AZOXYBENZENE  is  formed  by  oxidising  aniline  with  potassium  permanganate  in 
alkaline  solution  or,  better,  by  boiling  nitrobenzene  with  alcoholic  potash.  It  forms  pale 
yellow  crystals  melting  at  36°.  When  heated  with  concentrated  sulphuric  acid,  it  is  con- 
verted into  HYDROXYAZOBENZENE  : 

C6H5  •  N  -  N  •  C6H5     — >      C6HG  •  N  :  N  •  C6H4 .  OH. 
\0/ 

Hydroxyazo-compounds  are  formed  also  by  the  action  of  diazo-compounds  on  phenols 
(especially  resorcinol  and  the  naphthols)  in  presence  of  alkali : 

C6H5.N2.C1  +  C6H5.OK  =  C6H5-N  :  N-C6H4.OH  +  KC1. 

These  compounds  form  yellow,  red,  or  brown  crystals,  readily  soluble  in  alcohol  but 
insoluble  in  water.  They  are  azo-dyes  (tropceolins). 

AMINOAZOBENZENES  are  obtained  by  the  following  methods,  which  introduce  the 
amino-group  into  the  para-position.  Aminoazobenzene  itself  is  formed  by  nitrating  azo- 
benzene  and  reducing  the  mononitroazo benzene  thus  obtained  ;  or  by  transposition  of  the 
diazoamino -compounds  (see  p.  569),  and  hence  indirectly  from  diazobenzene  and  a  primary 
or  secondary  amine  ;  or  by  coupling  diazo-compounds  with  tertiary  amines,  in  which  case 
the  aminic  hydrogen  of  the  aminoazo -compounds  is  substituted.  If  the  aminic  group 
cannot  enter  the  para-position,  owing  to  this  being  occupied,  the  reaction  becomes  more 
difficult  and  o -aminoazo -derivatives  are  formed.  The  interaction  of  diazo-compounds  with 
m-diamines  yields  diaminoazobenzenes,  which  are  yellow,  red,  or  brown  dyes  and  are  termed 
Chrysoidines,  C6H5.N2.C1  +  C6H4(NH2)2  =  HC1  +  C6H5-N  :  N.C6H?(NH2)2(chrysoidine). 
The  amino-group  of  p-aminoazobenzenes  can  also  be  diazotised,  giving  diazo-compounds, 
which  again  react  with  amines  to  form  a  group  of  substances  called  bisazo -compounds  or 
tetrazo-compounds,  e.g.  C6H5-N:  N-CCH4-N  :  N-C6Hd  -NHo  ;  trisazo -compounds  are  also 
known.  These  substances  are  used  for  Biebrich  scarlet,  croceine,  &c. 


566  ORGANIC    CHEMISTRY 

HYDRAZOBENZENE,  C6H5-NH-NH-C6H5,  is  obtained  by  reducing  azobenzene 
or  nitrobenzene  with  zinc  dust  and  alcoholic  potash,  and  forms  colourless  crystals  melting 
at  126°.  With  energetic  reducing  agents  it  gives  aniline,  while  oxidising  agents  (FeCl3  or 
atmospheric  oxygen)  convert  it  into  azobenzene. 

Under  the  action  of  a  strong  acid  it  undergoes  transformation,  even  in  the  cold,  into 
Jenzidine  (diaminodiphenyl) : 


— NH-NH— <  >   -H-   NH2<  \— /  >NH2  (benzidine) 


which  forms  a  sulphate  only  slightly  soluble  in  cold  water.  The  formation  of  benzidine  in 
this  way  shows  that  it  contains  the  amino-groups  in  the  para -positions,  and  this  is  con- 
firmed by  the  fact  that  this  transformation  does  not  occur  with  a  hydrazobenzene  in 
which  the  par  a -hydrogen  is  replaced  by  another  group. 

Electrolytic  Reduction  of  Nitroderivatives.  This  has  been  studied  more  especially  by 
Gattermann,  Haber  and  Elbs,  who  found  that,  in  the  electrolytic  conversion  of  nitro- 
benzene to  aniline  in  acid  solution,  various  intermediate  products  are  formed,  the 
primary  ones  being  : 

C6H-5N02    •- ->     C6H5-NO     *     C6H5-NH-OH     >     C6H5-NH2: 

Nitrobenzene  Nitrosobenzene  Phenylhydroxylamine  Aniline 

while  in  alkaline  alcoholic  solution  two  secondary  reactions  occur,  the  nitrosobenzene  first 
formed  reacting  with  the  phenylhydroxylamine  formed  later,  giving  azoxybenzene  : 

C6H5-NH-OH  +  C6H5'NO  =  H00  +  C6H5-N  -  N-C6H5, 

\0/ 

this  being  subsequently  reduced  to  hydrazobenzene,  which  reacts  with  the  excess  of  nitro- 
benzene, forming  azobenzene  and  azoxybenzene. 

The  reduction  of  hydrazobenzene  to  aniline  requires  a  tension  at  the  cathode  much 
greater  than  suffices  for  the  formation  of  nitrosobenzene  and  phenylhydroxylamine  ;  with 
1-47  volts,  only  traces  of  aniline  are  formed. 


2.  DIAZO-DERIVATIVES 

In  the  diazo-compounds  of  the  aromatic  series  (discovered  by  P.  Griess  in 
1860)  the  characteristic  group,  —  N2— ,  is  united  to  only  one  aromatic  radical 
(aryl,  Ar)  and  to  an  acid  residue  (X).  This  group  therefore  forms  two  series  of 
compounds. 

(1)  Diazonium  salts,  in  which  one  atom  of  "nitrogen  is  pentavalent  as  in 
ammonium  salts.  Hantzsch  showed  their  structure  to  be  :  Ar-N  :  N. 


(2)  True  diazo-compounds  with  two  trivalent  nitrogen  atoms,  Ar-N  :  N-X  ; 
these  exist  in  two  stereoisomeric  forms  (see  p.  22),  the  somewhat  unstable 
syn-diazo-compound,s,  Ar-N,  and  the  stable  anti-diazo-compounds,  Ar-N.  The 

II  II 

X-N  N-X 

two  groups  Ar  and  X  are  far  apart  in  the  cmfo'-compounds,  so  that  they  cannot 
easily  react,  these  compounds  hence  being  the  more  stable.  The  cyanide  of 
antidiazo-p-chlorobenzene,  C1-C6H4-N,  is  not  decomposed  by  powdered  copper 

N-CN 

and,  on  the  other  hand,  cannot  have  the  constitution  of  a  diazonium  salt, 
C1-C6H4-N  :  N,  which,  like  ammonium  salts,  should  be  colourless  (whereas 

CN 


DIAZO-COMPOUNDS  567 

the  cyanide  is  yellow)  and  should  have  an  alkaline  reaction  and  conduct  the 
electric  current  in  aqueous  solution  ;  neither  of  these  properties  is  shown  by 
this  cyanide,  although  they  are  found  with  the  analogous  diazoanisole  cyanide, 
CH30-C6H6-N  •  N. 

CN 

The  antidiazotates  behave  partly  like  acids  and  the  corresponding  pseudo- 
acids.  Indeed,  antidiazo -hydrate  gives  the  reaction  for  hydroxyl  and  forms 
a  conducting  aqueous  solution  ;  it  is  unstable  and  is  converted  by  acids  into 
the  nitrosamine  (pseudo-acid),  which  no  longer  gives  the  reactions  for  hydroxyl, 
does  not  conduct,  has  a  neutral  reaction,  and  in  dry  ethereal  solution  does 
not  form  the  ammonium  salt  with  ammonia  (as,  for  example,  Phenylnitro- 
methane  does).  By  alkali  the  nitrosamine  is  immediately  reconverted  into  the 
antidiazotate  : 

Ar-N  Ar-N-H 

N-OH  N:O 

Antidiazotate  Nitrosamine 

Preparation.  The  gradual  addition  of  sodium  nitrite  (1  grm.-mol.)  solution 
to  a  solution  of  the  salt  of  the  amine  (1  grm.-mol.)  cooled  with  ice  results  in 
the  formation  of  the  soluble  diazonium  salt : 

C6H5-NH2,  HN03  +  NO-OH  =  2H20  +  C6H5-N2-N03. 

Aniline  nitrate  Phenyldiazonium  nitrate 

C6H5-NH2,  HC1  +  NO-OH  =  2H20  +  C6H5-N2-C1. 

Aniline  hydrochloride  Phenyldiazonium  chloride 

These  diazonium  salts  are  highly  explosive  when  dry,  so  that  they  are 
always  used  in  aqueous  solution,  when  they  are  completely  harmless. 

In  these  compounds  the  group  C6H5-N2-  behaves  like  the  ammonium 
cation  and  with  strong  mineral  acids  gives  neutral  salts,  while  the  salts  formed 
with  carbonic  acid  have  alkaline  reactions,  since,  like  the  alkaline  carbonates 
(see  vol.  i,  pp.  91  and  436),  they  readily  undergo  hydrolytic  dissociation, 

These  salts  have  extremely  high  conductivities,  and  hence  are  dissociated 
like  potassium  and  ammonium  chlorides,  and  like  these,  too,  they  form  diazo- 
nium platinichloride,  (C6H5-N2-Cl)2PtCl4.  The  hydroxide,  C6H5-N2-OH  (from 
the  chloride  +  AgOH),  is  known,  although  it  has  not  yet  been  isolated  ;  it  is 
soluble,  colourless,  and  strongly  alkaline.  All  these  reactions  indicate  the 
existence  of  a  pentavalent  nitrogen  atom  in  the  group  N2.  Two  constitutional 

C6H5-N  :  N 
formulae  are  hence  possible  :  C6H5-  N  j  NX  and  |  ;  various  reactions 

indicate  the  latter  to  be  the  more  probable  (see  above). 

There  are  various  ways  of  eliminating  the  nitrogen  from  diazo -compounds 
in  the  free  state,  union  taking  place  between  the  benzene  nucleus  and  the 
other  group  joined  to  the  N2  complex  : 

(a)  By  heating  the  aqueous  solution  of  a  diazonium  salt  a  phenol  is  formed  : 
CGH5-N2-C1  +  H£0  =  C6H5-OH  +  N2  +  HC1. 

(6)  When  a  diazonium  salt  is  heated  with  alcohol  the  benzene  nucleus  unites 
with  the  alkoxy-group  : 

C6H5-N2-HS04  +  C2H5-OH  =  C6H5-0-C2H5  +  N2  +  H2S04 ; 

under  certain  conditions,  however,  the  alcohol  is  oxidised  and  aldehyde  libe- 
rated along  with  the  nitrogen  : 

N02'C6H4-N,-C1  +  C2H5-OH  =  C6H6-N02  +  N2  +  HC1  +  CH3-CHO. 

p-NitrodiRRobenzcne  chloride  AceUldebyde 


ORGANIC    CHEMISTRY 

(c)  When  a  diazonium  chloride  is  treated  with  cuprous  chloride  dissolved 
in  concentrated  hydrochloric  acid  (Sandmeyer),  the  chlorine  (or  other  halogen) 
is  introduced  into  the  nucleus  :  C6H5-N2C1  =  C6H5-C1  +  N2.   The  same  result 
is    produced  by  finely  divided  copper,   which,  however,   acts  catalytically 
(Gattermann). 

(d)  The  cyanogen  group  is  introduced  into  the  nucleus  by  the  action  of 
potassium  salt  in  presence  of  a  copper  compound  : 

C6H5-N2C1  +  KCN  =  KC1  +  N2  +  C6H5-CN. 

Benzonitrile 

This  is  a  general  reaction  for  obtaining  (by  subsequent  hydrolysis)  aromatic  acids. 

(e)  Dry  diazobenzene  chloride,  when  treated  with  benzene  in  presence  of 
aluminium  chloride,  gives  diphenyl : 

C6H5N2C1  +  C6H6  =  N2  +  HC1  +  C6H5.C6H5. 

With  tertiary  amines,  diazonium  salts  condense  in  the  para -position,  giving 
aminoazo-derivatives : 

C6H5N2C1  +  C6H6N(CH3)2'=  HC1  +  C6H5-N  :  N-C6H4(CH3)2. 
Diazonium  salts  also  form  hydro xyazobenzenes   (see  p.  565). 

DIAZOBENZENE  CHLORIDE  (Phenyldiazonium  Chloride),  C6H5-N2.C1,  forms 
colourless  needles  soluble  in  water  and  is  obtained  by  the  action  of  moist  AgCl  on  the 
corresponding  bromide  ;  the  bromide  is  obtained  in  nacreous  scales  by  the  interaction  of 
ethereal  solutions  of  bromine  and  diazoaminobenzene  (tribromoaniline  remains  in  the 
solution). 

DIAZOBENZENE  NITRATE  (Phenyldiazonium  Nitrate),  C6H6.N2.N03,  is  the  salt 
which  is  most  widely  used,  and  is  obtained  by  passing  nitroso-nitric  fumes  into  a  cold 
ethereal  solution  of  diazoaminobenzene  or  into  an  aqueous  paste  of  aniline  nitrate  until 
this  is  dissolved  ;  to  the  filtered  liquid  are  added  the  triple  volume  of  alcohol  and  then 
ether  until  the  nitrate  separates  in  colourless  needles.  It  is  readily  soluble  in  water  but 
insoluble  in  ether,  benzene,  chloroform,  &c.  It  has  a  strong  acid  reaction  and  is  easily 
exploded  by  shock. 

DIAZOBENZENE  SULPHATE  (Phenyldiazonium  Sulphate),  C6H5  -N2  •  HS04,  is  best 
obtained  by  treating  a  concentrated  solution  of  crude  diazobenzene  nitrate  with  moderately 
concentrated  sulphuric  acid,  precipitating  several  times  with  excess  of  alcohol  and  with 
ether,  and  allowing  to  crystallise  in  a  desiccator.  It  forms  crystals  which  are  readily  soluble 
in  water  and  deflagrate  at  100°. 

DIAZOBENZENE  PERBROMIDE,  C6H5-N2-Br3,  is  prepared  by  the  action  of  hydro- 
bromic  acid  and  bromine  water  on  diazobenzene  salts. 

xN2-OH 
DIAZOBENZENESULPHONIC    ACID,    C6tt/  ,    is   known  as   anhydride, 

XS08H 
/N2 
C6H4C    |      ,  and  is  obtained  by  adding  a  mixture  of   sodium  sulphanilate  and  sodium 

XS03 

nitrite  to  dilute  sulphuric  acid.    It  forms  white  needles  readily  soluble  in  water,  and  is 
used  to  prepare  azo-dyes. 

With  KOH,  phenyldiazonium  hydroxide  forms  a  potassium  compound,  C6H5'N2-OK, 
and  hence  behaves  as  an  acid  besides  as  a  base.  But  as  it  cannot  be  assumed  that  these  two 
functions  are  exhibited  to  such  marked  extents  by  one  and  the  same  substance,  Hantzsch 
supposes  that,  in  aqueous  solution,  it  forms  a  mixture  of  phenyldiazonium  hydroxide, 
C6H6.N.OH, 

HI  and    syn-diazobenzene    hydroxide,    C6H5-N  :sN-OH,    so    that    the    general 

N 
reactions  mentioned  above  would  be  explained  thus  : 

C6H5-N  :  N  +  H-OH  =  HC1  +  CGH5.N  :  N-OH     >     CtJH5.OH  +  N  •:  N. 

I 
Cl 


DIAZOAMINO-DERIVATIVES  569 

None  of  the  reactions  referred  to  above  can  be  explained  well  without  assuming  the 
passage  of  diazonium  salts  with  pentavalent  nitrogen  into  true  diazo -compounds  with 
trivalent  nitrogen  (—  N  ==  N  — )  (see  above). 

3.  DIAZOAMINO-DERIVATIVES 

These  contain  the  aminodiazo-group,  —  N  =  N  —  NH  —  ,  and  are  yellow, 
crystalline  substances  which  do  not  combine  with  acids.  They  are  obtained 
by  adding  to  diazo-salts  (freshly  formed  in  solution)  primary  or  secondary 
amines,  e.g.  aniline  hydrochloride  ;  the  separation  of  the  yellow  crystalline  mass 
is  hastened  by  addition  of  concentrated  sodium  acetate  solution  : 

C6H5-N2-C1  +  C6H5-NH2  =  HCl  +  C6H5-N2-NHC6H5. 

To  2  mols.  of  aniline  and  3  mols.  of  hydrochloric  acid,  kept  cool  with  ice,  is 
slowly  added  1  mol.  of  sodium  nitrite,  the  liquid  being  then  precipitated  with 
concentrated  sodium  acetate  solution. 

They  are  also  formed  directly  from  free  aniline  and  nitrous  acid,  in  whicl1 
case  diazobenzene  hydroxide  must  be  regarded  as  an  intermediate  product  : 

(a)  C6H5-NH2  +  HN02  =  H20  +  C6H5-N2-  OH  ; 

(6)  C6H5-N2-OH  +  C.H5-NHa  =  H20  +  C6H5-N2-NHC6H5. 

With  nitrous  acid  in  acid  solution,  diazoamino-compounds  are  converted 
into  diazonium  salts,  the  remaining  aminic  residue,  —  NHC6H5.  being  diazo- 
tised  : 

C6H5-N  :  N-NHC6H5  +  HN02  +  2HC1  ==  2H20  +  2C6H6-N2C1. 

When  heated  with  aniline  hydrochloride,  diazoaminobenzene  solution  yields 
aminoazobenzene,  which  is  a  colouring- matter  from  which  others  are  derived. 
In  this  transformation,  which  is  common  to  all  diazoamino-compounds,  the 
aniline  hydrochloride  acts  catalytically  and  takes  no  part  in  the  reaction  ; 
the  amino-group  is  carried  to  the  para-position  with  respect  to  the  diazo- 
group,  or,  if  this  is  occupied,  to  the  ortho -position  : 

C6H5-  N  :  N-  NHC6H5      ->     C6H5-  N  :  N-  C6H4-  NH2. 

Diazoaminobenzene  Amiuoazobcnzene 

It  has  been  shown  by  H.  Goldschmidt  that  the  velocity  constant  of  this 
transformation  increases  with  the  amount  of  the  catalyst  (aniline  hydrochloride), 
and  the  catalytic  powers  of  the  different  amine  salts  are  propprtional  to  their 
degrees  of  dissociation  in  water. 

4.  HYDRAZINES 

These  compounds  are  obtained  by  reducing  diazonium  salts  with  a  hydro- 
chloric acid  solution  of  stannous  chloride  : 

C6H5N2C1  +  4H  =  C6H5-NH-NH2,  HCl. 

Phenylhydrazine  hydrochloride 

The  use  of  sodium  sulphite  in  place  of  stannous  chloride  gives  first  the 
diazosulphonate,  which,  when  treated  with  zinc  dust  and  acetic  acid  and 
subsequently  boiled  with  hydrochloric  acid,  gives  phenylhydrazine  hydro- 
chloride  ;  this  salt  separates  out,  being  only  slightly  soluble  in  water  and  less 
so  in  acid. 

The  three  stages  of  the  reaction  are  as  follow  : 

(a)  C6H5N2C1  +  Na2SO3  =  C6H5-N2-S03Na  +  NaCl. 

Diazobenzcne  chloride  Sodium  diazobenzenesulphonate 

(6)  C6H5-N2-S03Na  +  2H  =  C6H5-NH-NH-S03Na. 

Sodium  phenylhyd  rayanesulphonate 

(c)  C6H5-NH-NH-S03Na  +  H20  =  NaHS04  +  C6H5-NH-NH2. 

Phenylhydrazine 


570  ORGANIC    CHEMISTRY 

PHENYLHYDRAZINE,  C6H5-NH-NH2,  is  the  most  important  member  of  this  group 
and  has  a  basic  character,  forming  well-crystallised  salts.  It  is  a  colourless,  oily  liquid 
which  turns  brown  in  the  air  ;  it  dissolves  only  slightly  in  water,  melts  at  17-5°,  and 
boils  at  241°  with  slight  decomposition.  With  energetic  reducing  agents  it  forms  aniline 
and  ammonia,  and  with  oxidising  agents  (e.g.  chloride  of  lime)  it  can  form  diazonium 
compounds,  but  usually  nitrogen  is  eliminated  with  formation  of  water  and  benzene.  It 
gives  characteristic  reactions  with  lactones,  sugars,  aldehydes,  and  ketones  (see  pp.  206 
and  210). 

The  constitution  of  phenylhydrazine  is  proved  by  the  fact  that  nitrosomethylaniline, 
C6H5-N(CH3)-NO  (obtained  from  the  secondary  amine,  methylaniline,  C6H5-NH-CH3, 
by  the  action  of  nitrous  acid),  on  reduction,  yields  as.phenylmethylhydrazine, 
C6H5.N(CH3).NH2,  which  can  also  be  obtained  from  phenylhydrazine  by  the  action 
of  metallic  sodium  (this  replaces  the  iminic  hydrogen)  and  subsequently  of  methyl 
iodide : 

C6H5.NH.NH2        — >        C6H5.N.NH2       — >       C6H5.N-NH2. 

I  I 

Na  CH3 

Replacement  of  the  aminic  hydrogen  by  an  acid  residue  yields  hydrazides  (a  and^3),  which 
give  a  reddish  violet  coloration  with  sulphuric  acid  and  potassium  dichromate.  The 
hydrazides  are  insoluble  in  water  and  may  hence  be  used  for  the  precipitation  of  soluble 
acids. 

DIPHENYLHYDRAZINE,  (C6H5)2N.NH2,  is  obtained  by  reducing  Diphenylnitro 
samine,  (C6H5)2N-NO,  in  alkaline  solution  with  zinc  dust  and  acetic  acid.  It  is  a  base 
boiling  at  34°  almost  without  decomposition,  and  oxidising  readily  in  the  air  ;  its  salts  are 
unstable.  It  is  insoluble  in  water  and  hence  reduces  Fehling's  solution  only  slightly,  even 
in  the  hot.  With  concentrated  sulphuric  acid  it  gives  a  blue  coloration.  The  action  of 
oxidising  agents  distinguishes  it  from  the  isomeric  hydrazobenzene  ;  the  latter  gives 
azobenzene,  whilst  diphenylhydrazine  yields  in  the  cold  Tetraphenyltetrazone, 
(C6H5)2N-N:  N-N(C6H5)2,  and  in  the  hot  diphenylamine  and  violet  colouring- matters 
with  abundant  evolution  of  nitrogen.  With  nitrous  acid,  hydrazobenzene  forms  nitroso- 
derivatives,  whilst  diphenylhydrazine,  like  other  secondary  hydrazines,  gives  diphenyl- 
nitrosamine  and  nitrous  oxide. 

BENZYLPHENYLHYDRAZINE,  C6H5-CH2-N(C6H5).NH2,  is  obtained  from  phenyl- 
hydrazine and  benzyl  chloride.  Benzylhydrazine,  C<5H5.CH2.NH-NH2,  boiling  at  135° 
(in  vacuo),  is  also  known. 

p-NITROPHENYLHYDRAZINE,  obtained  from  p-nitraniline,  forms  yellow  crystals 
and  is  a  useful  reagent  for  aldehydes  and  ketones. 

/3-PHENYLHYDROXYL AMINE,  C6H5.NH.OH,  is  obtained  by  the  gentle  oxidation 
of  aniline  or  the  cautious  reduction  of  nitrobenzene  with  zinc  dust  and  water,  and  forms 
colourless  crystals  melting  at  81°.  With  oxygen  it  gives  p-aminophenol,  with  oxygen 
azoxybenzene  and  with  dichromate  nitrosobenzene.  The  a-isomeride,  NH2-OC6H6,  is 
of  little  importance. 


L.  AROMATIC  ALCOHOLS,  ALDEHYDES,  AND  KETONES 

In  these  compounds  the  primary  alcohol  group,  the  aldehyde  group,  or  the 
ketonic  group  forms  a  side-chain  to  the  benzene  nucleus  and  shows  all  the 
general  properties  of  these  groups.  Di-  and  trihydric  alcohols  are  also  known, 
e.g.  Phthalic  Alcohol  (ortho)  ;  Xylylene  Alcohol  (para),  C6H4(CH2-  OH)2 ; 
Phenylglycerol,  C6H5-CH(OH)-CH(OH)-CH2-  OH. 

BENZYL  ALCOHOL,  C6H5-CH2-OH  (discovered  by  Cannizzaro  in  1853),  is  isomeric 
with  the  cresols,  CH3-C6H4-OH,  and  is  obtained  by  th«  interaction  of  benzyl  chloride 
and  potassium  acetate  and  subsequent  hydrolysis  of  the  acetyl-derivative  thus  obtained, 
or,  better,  by  the  action  of  aqueous  potassium  hydroxide  on  benzaldehyde : 

2C6H5.CHO  +  KOH  =  C6H5.CO2K  +  C6H5.CH2.OH. 
The  alcohol  readily  gives  benzyl  chloride  when  treated  with  PC16.     On  oxidation 


BENZALDEHYDE  571 

it  gives  first  benzaldehyde  and  then  benzoic  acid,  its  constitution  being  thus  proved.  It 
forms  simple  and  mixed  ethers  and  esters.  It  differs  from  aliphatic  alcohols  by  resinifying 
with  sulphuric  acid.  It  has  the  characters  of  a  true  alcohol  and  is  hence  insoluble  in  alkali 
(unlike  the  phenols).  It  is  slightly  soluble  in  alcohol  and  boils  at  206°. 

Various  higher  homologues  are  known  :  Tolylene  Alcohols,  CH3  •  C6H4  •  CH2  •  OH  ; 
Cumyl  Alcohol  (p-),  C3H7.C6H4.CH2.OH,  &c. 

Styryl  Alcohol,  C6H5  •  CH  :  CH  •  CH2  •  OH,  containing  an  unsaturated  side-chain,  is  found 
as  ester  (styracin)  in  storax  ;  it  forms  acicular  crystals  with  an  odour  of  hyacinth. 

With  alcoholic  potash  aromatic  aldehydes  are  partly  oxidised  and  partly 
reduced,  benzaldehyde,  for  instance,  being  converted  into  potassium  benzoate 
and  benzyl  alcohol  : 

2C6H5-  CHO  +  KOH  =  C6H5-  C02K  +  C6H5-  CH2-  OH. 

With  dimethylaniline  or  phenol  these  aldehydes  give  derivatives  of  Tri- 
phenylmethane  : 

xC6H4-OH 
C6H5-  CHO  +  2C6H5-  OH  =  H20  +  C6H5-  CH<f 

C6H4-  OH. 

^ 

BENZALDEHYDE,  C8H6-C^      ,  occurs  in  the  Amygdalin,  C2GH27NOn,  of  bitter 

XH 

almonds  in  the  form  of  a  glucoside.  It  is  a  liquid  of  pleasant  odour  and  dissolves  slightly  in 
water  ;  it  boils  at  179°,  has  the  sp.  gr.  1-05  and  forms  bitter  almond  oil.  It  oxidises  easily 
and  forms  crystalline  products  with  bisulphites,  while  it  combines  with  hydrogen,  hydrogen 
cyanide,  &c.,  forming  an  oxime,  a  hydrazone,  &c.  With  ammonia  it  gives  Hydro- 
benzamide,  3C6H5.CHO  +  2NH3  =  3H2O  +  (C6H5.CH)3N2.  It  is  formed  by  distilling  a 
mixture  of  calcium  formate  and  benzoate  and  also  by  oxidising  benzyl  alcohol. 

Until  recently  it  was  prepared  industrially  by  heating  benzal  chloride  under  pressure 
with  milk  of  lime  and  calcium  carbonate  : 

C6H6.CHC12  +  Ca(OH)2  =  CaCl2  +  C6H5.CHO  +  H2O. 

Nowadays,  however,  it  is  obtained  more  conveniently  by  treating  benzene  with  a  gaseous 
mixture  of  carbon  monoxide  and  hydrogen  chloride  in  presence  of  Cu2Cl2  or  AlBr3  (Ger.  Pat. 
126,241). 

Pure  benzaldehyde  may  also  be  readily  obtained  by  oxidising  toluene  (e.g.  with  PbO2 
and  H2SO4),  a  mixture  of  40  per  cent,  of  the  aldehyde  with  60  per  cent,  of  unaltered  toluene 
being  obtained  (Ger.  Pat.  154,499).  One  hundred  kilos  of  this  mixture  and  400  litres  of 
water  are  treated  with  sulphur  dioxide  until  about  26  per  cent,  is  absorbed.  In  this  way 
all  the  aldehyde  passes  into  solution  (improvement  on  the  use  of  sodium  bisulphite)  and 
can  be  decanted  from  the  undissolved  toluene.  It  is  then  sufficient  to  heat  the  sulphurous 
solution  slowly  from  30°  to  100°  to  eliminate  all  the  sulphur  dioxide  which  is  passed  into  a 
further  portion  of  the  aldehyde  mixture.  After  cooling  the  solution,  almost  the  whole  of 
the  benzaldehyde  is  obtained  in  a  pure  state  and  the  mother-liquors  are  utilised  in  succeeding 
operations  so  that  the  small  amounts  of  aldehyde  remaining  dissolved  may  not  be  lost. 

Commercial  benzaldehyde  and  that  for  industrial  uses  costs  about  3*.,  the  pure  product 
about  4s.,  and  the  chemically  pure  about  9s.  6d.  per  kilo.  For  industrial  purposes,  it 
should  have  a  specific  gravity  of  1-052  to  1-054,  and  should  distil  completely  in  a  current 
of  hydrogen  between  176°  and  180°.  Its  solution  in  concentrated  sulphuric  acid  should 
be  only  slightly  brown  and  it  should  dissolve  completely  in  sodium  bisulphite.  Any 
benzoic  acid  present  can  be  titrated  with  phenolphthalein  as  indicator. 

HOMOLOGUES  OF  BENZALDEHYDE  are  obtained  by  treating  aromatic 
hydrocarbons  with  gaseous  hydrogen  chloride  and  carbon  monoxide  in  presence 
of  A1C13  or  Cu2Cl2.  The  first  product  obtained  under  these  conditions  is  probably 
formyl  chloride,  which  then  reacts  thus  : 

X-C6H5  +  Cl-CHO  =  HC1  +  X-C6H4-CHO. 
Aldehydes  are  also  obtained  from  ethyl  chloroxajate  and  aromatic  hydro- 


572  ORGANICCHEMISTRY 

carbons  in  presence  of  A1C13,  the  ketonic  ester  obtained  being  hydrolysed  and 
the  acid  subjected  to  dry  distillation  in  order  to  expel  C02  : 

X-  C6H5  +  Cl-  CO-  COOC2H5  =  HC1  +  X- C6H4-  CO-  COOC2H5 ; 
X-  C6H4-  CO-  COOC2H5  =  X-  C6H4-  CHO  +  C02. 

The  action  of  HC1  and  HCN  on  aromatic  hydrocarbons  also  yields  alde- 
hydes, aldines  being  formed  as  intermediate  products  : 

C6H6  +  HCN  +  HC1  =  C6H5-  CH  :  NH,  HC1. 

Benzaldine  Hydrochloride 

C6H5-  CH  :  NH,  HC1  +  H20  =  C6H5-  CHO  +  NH4C1. 

CINNAMALDEHYDE,  C6H5-CH  :  CH-CHO,  is  an  oil  of  pleasant  odour,  boiling  at 
246°  ;  it  is  volatile  in  steam  and  is  separated  from  cinnamon  oil,  of  which  it  is  the  chief 
constituent,  by  means  of  sodium  bisulphite. 

NITROBENZALDEHYDES,  NO2-CfiH4-CHO,  are  prepared  in  various  ways.  The 
ortho-compound  is  obtained  either  from  o-nitrobenzyl  chloride  or  by  oxidising 
o-nitrotoluene.  It  forms  colourless  crystals  melting  at  46°  and  with  acetone  and  caustic 
soda  leads  to  the  synthesis  of  indigo.  • 

Nitration  of  benzaldehyde  yields  mainly  the  m-compound,  together  with  20  per  cent, 
of  the  o-derivative. 

CUMIN  ALDEHYDE  (Cuminol,  Isopropylbenzaldehyde),  C3H7-C6H4-CHO,  occurs 
in  Roman  cumin  oil. 

AROMATIC  KETONES 

ACETOPHENONE,  C6H5-CO-CH3,  is  obtained  by  distilling  calcium  acetate  with 
calcium  benzoate  or,  better,  by  treating  benzene  with  acetyl  chloride  in  presence  of 
A1C13. 

It  forms  crystals  melting  at  20°  and  boils  at  200°  ;  it  dissolves  only  slightly  in  water, 
has  a  pleasant  smell,  and  is  used  as  a  hypnotic  under  the  name  of  hypnone.  On  oxidation 
it  gives  either  benzylformic  acid  or  benzoic  acid  and  carbon  dioxide  ;  halogens  give  products 
substituted  in  the  side -chain. 

BENZOPHENONE  (Diphenyl  Ketone),  C6H5-CO-C6H5,  is  obtained  either  by  the  dry 
distillation  of  calcium  benzoate  or  by  the  action  of  benzoyl  chloride  on  benzene  in  presence 
of  A1C13.  Its  behaviour  is  similar  to  that  of  aliphatic  compounds,  and  with  hjdrogen  it 
forms  Benzhydrol,  C6H5.CH(OH).C6H5,  and  Benzopinacone,  (C6H5)2  =  C  -  C  =  (C6H5)2. 

OH   OH 

When  fused  with  potassium  hydroxide,  it  gives  benzene  and  potassium  benzoate  : 

C6H5.CO.C6H5  +  KOH  =  C6H6  +  C6H5-COOK. 

Benzophenone  exists  in  two  modifications  which  differ  physically  :  an  unstable  form, 
m.pt.  27°,  and  a  stable  form,  m.pt.  49°. 

QH4\ 
DIPHENYLENEKETONE,    |         /CO,  is  the  ketone  corresponding  with  diphenylene- 

C6H4 
methane  (see  later),  and  is  obtained  by  heating  phenanthraquinone  with  lime.     With  nascent 

CeH4s 
hydrogen  it  gives  Fluorene  Alcohol,  |         ^)CH-OH  (colourless  scales,  m.pt.  153°),  and, 

CeH,/ 
when  fused  with  potash,  Diphenylcarboxylic  Acid,  C6H5  •  C6H4  •  CO2H. 

Polyacetones,  such  as  Benzoylacetone,  C6H5-CO-CH2.CO-CH3,  and  Acetophenone- 
acetone,  C6H5 .  CO  •  CH2 .  CH2 .  CO  •  CH3,  are  also  known. 

Condensation  of  benzaldehyde  with  acetophenone  or  acetone  in  presence  of  NaOH 
gives  unsaturated  ketones  :  Benzalacetone,  CeHg  •  CH  :  CH  •  CO  •  CH3  (m.pt,  41°); 
Benzalacetophenone  (chalkone),  C6H5-CH  :  CH.CO-C6H5  (m.pt.  58°). 

AROMATIC  OXIMES  present  interesting  cases  of  isomerism  (see  pp.  22  and 
210).  Thus,  Benzaldoxime  is  known  in  two  forms  :  liquid  anti-benzaldoxime, 
which  boils  unaltered,  and  solid  syn-benzaldoxime,  which  readily  loses  water 


AROMATIC    ALCOHOL    DERIVATIVES      573 

C6H5-C-H  =  H20  +  C6H5-C  •  N. 
(with  acetic  anhydride),  forming  benzonitrile : 

N-OH 

Under  these  conditions  the  anti-aldoxime  gives  an  acetyl-derivative,  so  that 
the  two  aldoximes  can  be  distinguished  in  this  way. 

With  ketoximes  two  isomerides  are  formed  only  when  the  two  groups  united 
to  the  carbonyl  group  are  different : 

X-C-X'  X-C-X' 

II  and  || 

N-OH  .  OH  -  N 

syn  anti 

C6H5  —  C  —  C6H5 
Thus,  Benzophenonoxime,  ,  does  not  form  isomerides, 

N-OH 

which  are,  however,  obtained  if  a  hydrogen  atom  of  one  of  the  benzene  groups 
is  replaced  by  a  halogen,  alkyl  group,  &c. 

The  ketoximes  show  Beckmann's  transposition,1  in  which  the  isomeric 
ketoximes,  which  have  different  melting-points,  give  rise  to  two  different 
substituted  amides  according  as  the  transposition  takes  place  with  the  group 
X  or  X'  (see  Note). 

BENZALAZINE,  C6H5-CH  :  N-N  :  CH-C6H5,  is  obtained  by  the  condensation  of 
2  mols.  of  benzaldehyde  with  1  mol.  of  hydrazine  (sulphate),  and  forms  yellow  crystals 
melting  at  93°. 

BENZALDEHYDEPHENYLHYDRAZONE,  CRH5-CH  :  N-NHC6H5,  forms  colourless 
crystals  melting  at  132°  and  forms  stereoisomerides. 

M.  AROMATIC  HYDROXY- ALCOHOLS,  HYDROXY-ALDEHYDES, 
AND  KETONIC  ALCOHOLS 


j  'o  =  saligenin  ^.-rr     (°  —  salicylaldehyde 

\va\hydroxybenzyl        C6H4-<pTTQ  -  \m\hydroxybenzalde- 
[p  J      alcohols  [p  )         Tiydes 


n  TT  '     /"KTT  17-       7J  7     j     n  TT    ^OCHo    p  =    ttHlSlC  alcohol 

C6H3\— OH     6  protocatechuic  aldehyde  C6H4<.rrrr    nfr  /        <-  AK°    ^    ^  o^no\ 
\pwn  i  u±i2' u±i  ^m.pt.  40  ;  o.pt.  zoy  ) 


C6H3^-OCH3     3     vanillin 


OCH  /OH 

s  p  =  anisaldehyde  C6H3—OCH3       3    vanillic  alcohol 

4 
3 
1 

The  Beckmann  transposition  is  that  obtained  with  ketoximes  in  general  by  treating  them  with  acety  Jchloride 
or  concentrated  sulphuric  acid  or,  in  some  cases,  merely  by  fusion.  The  oxygen  of  the  oxime  changes  places 
with  a  radical  united  to  the  ketonic  carbon  giving  a  substituted  amide,  an  unstable,  tautomeric,  hydroxyl  com- 
pound being  probably  formed  as  an  intermediate  product : 

X-C:0 

x-c-x'  rX-c-OH- 


N-OH 


pX-C-OH-i 

I 

L      N-X'J 


The  structure  of  the  isomeric  syn-  and  anti-oximes  can  be  determined  by  Beckmann's  reaction.     Thus, 
the  above  oxime  is  the  anti-compound,  the  transposition  with  the  syn-isomeride  would  be  as  follows 

O    C-X' 


574  ORGANIC    CHEMISTRY 

The  three  isomeric  hydroxybenzyl  alcohols  are  known,  their  melting-points 
being  as  follow  :  o-,  82°  ;  m-,  67°  ;  p-,  110°.  The  most- common  of  these  is  : 

SALIGENIN  (o-Hydroxybenzyl  Alcohol,  see  above),  OH-CfiH4-CH2-OH,  occurring  in 
the  glucoside  salicin,  from  which  it  can  be  obtained  by  the  action  of  emulsin,  ptyalin  or 
dilute  acid  (Piria,  1845) : 

C6Hn06.O.C6H4.CH2.OH  +  H20  =  OH . CaH4 •  CH2 . OH  +  C6H12O6  (glucose). 

It  is  soluble  in  alcohol,  ether,  or  boiling  water  and  gives  a  dark  blue  coloration  with  ferric 
chloride. 

AROMATIC  HYDROXY ALDEHYDES,  or  phenolic  aldehydes,  are  obtained  (1 )  by  the 
action  of  chloroform  and  caustic  potash  on  phenols  :  C6H5  •  OH  +  4KOH  +  CHC13  = 
3KC1  +  3H20  +  CHO-C6H4-OK  ;  or  (2)  by  the  action  of  hydrocyanic  and  hydrochloric 
acids  on  phenols  in  presence  of  aluminium  chloride  or  zinc  chloride,  aldim  hydrochlorides 
being  formed  as  intermediate  products. 

With  difficulty  by  oxidising  agents,  but  readily  by  fusion  with  alkali,  these  aldehydes 
give  the  corresponding  hydroxycarboxylic  acids.  They  reduce  ammoniacal  silver  solution 
but  not  Fehling's  solution.  With  alkali  they  give  soluble  alkali  phenoxides  which  form 
the  alkyl  derivatives  of  the  phenols  when  treated  with  alkyl  iodides. 

SALICYLALDEHYDE  (o-Hydroxybenzaldehyde),  OH-C6H4-CHO,  is  found  in  the 
volatile  oil  of  Spircea  ulmaria.  Its  synthesis  by  means  of  chloroform  is  indicated  above 
and  it  is  separated  from  the  p-aldehyde  formed  at  the  same  time  by  distillation  in  steam. 
It  is  a  liquid,  b.p.  196°,  sp.  gr.  1-172  at  15°  ;  it  dissolves  to  some  extent  in  water  and  gives 
a  violet  coloration  with  ferric  chloride.  Like  all  o-hydroxy-aldehydes  it  colours  the 
skin  yellow. 

ANISALDEHYDE  (see  above)  is  obtained  by  the  cautious  oxidation  of  Anethole, 
CH3-CH  :  CH.C6H4-OCH3,  with  dichromate  and  sulphuric  acid,  the  aldehyde  being 
distilled  in  steam  and  purified  by  means  of  sodium  bisulphite.  It  boils  at  248°,  has  sp.  gr. 
1-123  at  15°,  and,  owing  to  its  strong  odour  of  hawthorn,  is  used  in  perfumery  (price  20s. 
per  kilo). 

VANILLIN,  C6H3(OH)(OCH3)(CH,0)4:3:  1  (m-Methoxy-p-hydroxybenzaldehyde), 
is  found  (about  2  per  cent.)  in  the  pods  or  fruit  of  vanilla  (Vanilla  planifolia) l  and  as  a 
glucoside  (coniferin,  Qi6H22O8  +  2H2O)  in  the  sap  of  the  conifers,  in  asparagus,  and  in 
beet -juice  ;  it  is  also  formed  by  oxidising  the  resin  of  olives. 

It  is  readily  obtained  artificially  by  treating  clove  oil  with  dilute  alkali,  which  dissolves 
the  eugenol  and  transforms  it  into  Isoeugenol,  C6H3(OH)(OCH3)(CH  :  CH-CH3),  which  is 
then  oxidised  by  ozone  or  permanganate.  It  forms  slender  white  crystals  which  melt  at 
80-81°  and  sublime,  and  it  boils  at  285°.  It  has  a  strong  odour  of  vanilla  and  now  costs 
about  36s.  per  kilo,  although  twenty  years  ago  its  price  was  several  hundreds  of  pounds 
per  kilo. 

ByHCl  at  200°  it  is  transformed  into  protocatechuic  aldehyde,  the  methylene  ether  of 

CHrCH.C-O. 
which  constitutes  Piperonal  (heliotropin  or  artificial  heliotrope),  ||       ^)CH2, 

CHO-C  :    CH-C-O/ 
(m.pt.  37°  ;  b.pt.  263°),  costing  from  16s.  to  28s.  per  kilo,  according  to  its  purity. 

BENZOYLCARBINOL,  C6H5-CO-CH2-OH,  obtained  from  Phenacyl  Bromide, 
C6H5-CO-CH2Br,  forms  stable,  shining  scales,  and  possesses  strong  reducing  pi opei ties. 
The  corresponding  acetonaldehyde  is  Phenylglyoxal,  C6H5  •  CO  •  CHO,  analogous  to  pyruvic 
aldehyde. 

i  Vanilla  is  a  climbing,  herbaceous  plant  growing  well  in  Mexico  and  in  Reunion.  The  fruit  is  fleshy  and 
cylindrical  (10  to  30  cm.  long)  and  contains  a  number  of  round  black  seeds  with  a  pleasant  odour.  The  fruit 
is  gathered  before  it  is  quite  ripe,  as  otherwise  the  pods  open  and  the  seeds  are  lost.  Their  vitality  is  destroyed 
by  steeping  them  in  waterat  80°  to  85°  or  placing  them  in  an  oven  at  5Q°  to  70°  or  in  the  sunlight.  The  capsules 
thus  turn  dark  brown  and  after  being  allowed  to  sweat  for  20  to  30  days  at  30°  to  40°  they  become  covered  with 
a  crystalline,  perfumed  powder.  They  are  then  tied  up  in  bundles  of  50  and  sold  in  boxes  holding  3  to  10  kilos 
at  20«.  to  64s.  per  kilo.  Of  inferior  quality  are  the  smaller  fruit  and  those  from  the  Antilles,  Brazil,  and  Guiana. 
They  are  used  for  pastry,  liquors,  perfumes,  and  chocolates.  The  United  States  imported  400  tons  (£247,200) 
of  vanilla  pods  in  1910  and  500  tons  (£427,400)  in  1911. 


AROMATIC    ACIDS  575 

N.  AROMATIC  ACIDS 

Like  the  aliphatic  acids,  these  form  salts,  anhydrides,  esters,  amides, 
&c.,  and  give  in  addition  other  products  by  substitution  in  the  benzene 
nucleus. 

Here,  too,  the  characteristic  group  is  the  carboxyl,  COOH,  and  the  acids 
may  be  either  mono-  or  poly-basic,  according  to  the  number  of  carboxyl  groups, 
this  being  indicated  in  the  name  : 

C6H5-COOH          C6H4(COOH)2          C6H3(COOH)3  C6(COOH)6 

Benzole  acid  Phthalic  acids  Benzenetricarboxylic  acids  Mellitic  acid 

(benzenecarboxylic  or         (benzenedicarboxylic  or      (benzenetrimethanoic  acids)          (benzenehexacarboxylic  or 
benzenemethanoic  acid)  bcnzenedimethanoic  acids)  benzenehexamethanoic  acid) 

Aromatic  acids  with  unsaturated  side-chains  are  also  known,  these  behaving 
like  unsaturated  aliphatic  compounds  : 

C6H5-  CH  :  CH-  C02H  C6H5-  C  i  C-  C02H 

Cinnamic  acid  Phenylpropiolic  acid 

There  are  also  various  acids  derived  from  the  hydrobenzenes,  with  characters 
resembling  those  of  aliphatic  compounds. 

Aromatic  hydroxy -acids  with  a  hydroxyl  group  in  the  nucleus  behave  partly 
like  phenols  and  partly  like  acids,  and  are  analogous  to  the  aromatic  alcohol- 
acids  containing  acid  groups  and  true  alcoholic  groups  in  the  side- chains. 

In  each  of  the  aliphatic  acids  a  hydrogen  atom  can  be  replaced  by  a  benzene 
residue,  giving  aromatic  acids  of  the  acetic  acid  series  (e.g.  Phenylacetic  Acid, 
C6H5-CH2-C02H)  and  of  the  glycollic  and  succinic  series,  &c. 

In  general,  aromatic  acids  are  crystalline  and  only  slightly  soluble  in  water, 
while  they  are  often  soluble  in  alcohol  or  ether.  The  more  simple  ones  sublime 
or  distil  unchanged  and  lose  C02  only  on  distillation  with  soda-lime,  this 
occurring  with  the  more  complex  acids  simply  on  heating.  Their  alkaline  salts 
are  soluble  in  water,  but  the  acids  are  precipitated  in  the  free  state  on  addition 
of  a  mineral  acid. 

GENERAL  METHODS  OF  FORMATION.  (a)  When  hydrocarbons 
homologous  with  benzene  are  oxidised,  each  side- chain,  no  matter  what  its 
length  or  nature,  yields  only  a  single  carboxyl  group  attached  directly  to 
the  benzene  nucleus.  When  several  lateral  chains  are  present,  dilute  nitric 
acid  oxidises  them  gradually,  whilst  with  chromic  acid  they  are  all  oxidised 
together:  C6H5-CH3  gives  C6H5-CO2H;  C6H5-C2H5  gives  C6H5-C02H; 
C6H5-CH:CH-C02H  gives  C6H5-C02H;  C6H4(CH3)2  gives  C6H4(C02H)2. 
Of  the  disubstituted  derivatives,  the  ortho-compounds  are  oxidised  very  easily 
and  do  not  give  carboxyls  unless  the  oxidation  is  carried  out  with  great  care, 
e.g.  with  dilute  nitric  acid  or  permanganate  ;  para-derivatives  are  readily 
oxidised  by  chromic  acid  and  the  meta-  less  readily.  Compounds  containing  a 
negative  group,  even  OH,  in  the  or^o-position  are  not  oxidised  even  by  chromic 
acid. 

(6)  By  oxidising  primary  alcohols  and  aldehydes  in  the  usual  way. 

(c)  By    hydrolysing    nitriles  :     C6H5-  CN  +  2H20  =  NH3  +  C6H5-  COOH. 
The  nitriles  are  formed  by  distilling,  e.g.  potassium  phenylsulphonate  with 
potassium  cyanide  or  ferrocyanide  :  C6H5-  S03K  +  KCN  =  K2S03  +  C6H5-  CN 
(benzonitrile)  or  from  the  chlorides  of  compounds  with  side-chains  :  C6H5-  CH2C1 
+  KCN  =  KC1  +  C6H5-CH2-CN    (benzyl   cyanide).      ^Nitriles    can   also    be 
obtained  from  primary  amines  by  diazotising  and  subjecting  the  diazo-com- 
pounds  to  Sandmeyer's  reaction  (see  p.  568)  ;  also  from  the  aldehydes  by  way 
of  the  oximes  (see  pp.  199  and  206). 

(d)  By  the  action  of  C02  on  monobromobenzenc  in  presence  of  sodium 


576  ORGANIC    CHEMISTRY 

(Kekule),  or  by  treating  benzene  or  its  homologues  with  phosgene  (COC12) 
in  presence  of  A1C13  (Friedel  and  Krafft)  : 

C6H5Br  +  C02  +  2Na  =  C6H5-COONa  +  NaBr; 

C6H6  +  COC12  =  HC1  +  C6H5-  CO-  Cl  (which,  with  H20,  gives  the  acid). 

(e)  Phenolic  Acids  are  obtained  by  the  action  of  C02or  CCl4and  alkali  on 
sodium  phenoxides : 

C6H5-ONa  +  C02     =  C6H4 


C6H5-  ONa  +  CC14    =  C6H4<^  •  +  NaCl,  and 
+  4NaOH  =  3NaCl  +  2H20  +  C6H4<2?nivr     (para). 


If  chloroform  is  used  in  place  of  carbon  tetrachloride,  ortho-  and  para- 
hydro  xyaldehydes  are  obtained. 

(/)  The  syntheses  with  ethyl  acetoacetate  or  ethyl  malonate  are  analogous 
to  those  of  the  fatty  series  (see  pp.  309  and  332)  and  are  carried  out  with  phenols, 
derivatives  with  halogens  in  the  side-chain,  &c.  ;  complex  ketonic  acids  are 
obtained  which  undergo  both  the  acid  and  the  ketonic  decomposition. 

Aromatic  acids  with  unsaturated  side- chains  are  obtained  by  the  methods 
used  for  aliphatic  unsaturated  acids,  or  by  Perkin's  reaction  (see  p.  291 )  between 
fatty  acids  and  aromatic  aldehydes  in  presence  of  aoetic  anhydride,  which 
removes  the  water  formed  : 

C6H5-  CHO  +  CH3-  C02Na  =  C6H5-  CH  :  CH-  COONa  +  H20. 

Sodium  acetate 

With  substituted  benzaldehydes  a  varied  series  of  unsaturated  aromatic  acids 
can  be  obtained. 

Also  benzal  chloride  and  sodium  acetate  give  unsaturated  acids  : 

C6H5-CHC12  +  CH3-COOH  =  2HC1  +  C6H5-CH  :  CH-COOH. 

Cinnamic  acid 

Ethyl  acetoacetate  and  also  malic  acid  act  on  phenols  in  presence  of  con- 
centrated sulphuric  acid,  giving  anhydrides  of  unsaturated  phenolic  acids,  e.g. 

/CH:CH 
C6H4\  I      (coumarin). 

0 CO 

(a)  MONOBASIC  AROMATIC  ACIDS 

The  isomerism  among  these  compounds  is  similar  to  that  of  the  halogen 
derivatives  of  aromatic  hydrocarbons. 

BENZOIC  ACID,  C6H5-COOH,  is  found  naturally  in  various  resins  (e.g. 
gum  benzoin)  and  in  balsam  of  Tolu,  from  which  it  is  obtained  by  sublimation 
or  by  heating  with  milk  of  lime.  It  is  formed  in  the  urine  of  herbivorous  animals 
as  Hippuric  Acid,  which  gives  glycocoll  and  benzoic  acid  on  putrefaction.  It 
forms  white  leaflets .  melting  at  121°  and  boils  at  250°;  it  sublimes  at  100° 
to  120°  and  distils  in  steam.  It  has  an  irritating  odour  and  is  soluble  in  boiling 
water  ;  its  alkali  salts  crystallise  well  (C6H5-  CO2K  +  |H20)  and  dissolve  in 
water. 

It  is  prepared  industrially  by  converting  toluene  (from  light  tar  oils), 
by  means  of  chlorine,  into  benzenyl  trichloride, 'C6H5-CCl3i  and  heating  this 
with  milk  of  lime  under  pressure:  2C6H5-CC13  +  4Ca(OH)2  =  3CaCl2  + 
(C6H5-COO)2Ca+4H20  (with  traces  of  chlorobeiizoic  acid).  Instead  of  being 
treated  with  lime,  the  benzenyl  trichloride  may  be  oxidised  directly  with 
dilute  nitric  acid,  in  vessels  fitted  with  stirrers,  as  long  as  hydrogen  chloride 
is  evolved,  the  benzoic  acid  being  then  distilled,  allowed  to  crystallise,  centri- 


MONOBASIC    AROMATIC    ACIDS 

MONOBASIC  AROMATIC  ACIDS 


577 


Formula 

1 
Name 

Position 
of  the 
groups 

Melting- 
point 

C,H6-C02H 

Benzoic  (benzenecarboxylic) 

_ 

121° 

CH,-C6H4.C02H 

o-Toluic  (o-methylbenzenecarboxylic) 

1:2 

105° 

» 

m-    ,,       (m-                    „                    ) 

1  :  3 

111° 

„ 

P-     „       (P-                     „                    ) 

1  :  4 

179° 

C6H6-CH2.C02H 

Phenylacetic  .... 

— 

76° 

C6H3(CH3)2-C02H 

Hemellitic       .... 

1     2-3 

144° 

,, 

o-Xylic  (l-CHa  ;   2-CH,  ;   4-CO2H) 

1    2-4 

166° 

,, 

m-  „       (vie.)  .... 

1    3-2 

98° 

,, 

m-  „       (a*.)    ....              ^ 

1    3-4 

126° 

» 

Mesitylenic      .... 

1    3-5 

166° 

» 

p-Xylic            .... 

1    4-2 

132° 

C,H6-CH2.CH2.C02H 

Hydrocinnamic 

— 

49° 

CeH6-CH(CH3)-CO2H 

Hydratropic  (methylphenylacetic) 

— 

below  —  20° 

(b.pt.  267°) 

C2H6.C,H4-C02H 

o-Ethylbenzoic 

1:2 

68° 

» 

p-          ,,                  ... 

1:4 

112° 

C.H2(CH3),-C02H 

Prehnitylie  (trimethylbenzenecarboxylic) 

1    2:3-4 

168° 

„ 

a-Isodurylic                         „ 

1    2:3-5 

215° 

,, 

Durylic                                 ,, 

1    2:4-5 

149° 

» 

•y-Isodurylic                         „ 

1    2:4-6 

127° 

» 

Mesitylenecarboxylie          „ 

1    3:5-2 

152° 

C3H,-C,H4-CO2H 

Cuminic  (p-isopropylbenzoic)    . 

1  :  4 

117° 

C,H(CH3)4.C02H 

Prehniteneearboxylic  (tetramethylbenzoic) 

1:2:3:4-5 

165° 

„ 

Isodurenecarboxylic                  , 

1:2:3:5-4 

161° 

» 

Durenecarboxylic                       , 

1:2:4:5-3 

179° 

C,(CH3)6.C02H 

Pentamethylbenzoic 

1:2:3:4:5:6 

210-5° 

C,H5-CH:CH-CO2H 

Cinnamic 

— 

133°  (b.pt.  300°) 

C6H5.C(:CH2).C02H 

Atropic 

— 

107°  (b.pt.  267°) 

CeH5-C  i  C-CO,H 

Phenylpropiolic 

— 

137° 

OH  •  CaH4  •  CH  :  CH  •  CO2H    . 

o-Coumaric 

1     2 

208° 

)J                                                      • 

P- 

1     4 

206° 

OH.C.H4.C02H. 

o-Hydroxybenzoic  (salicylic) 

1     2 

159° 

» 

m-             „                   ,, 

1     3 

200° 

»>              ... 

P- 

1     4 

210° 

CH3O-C;H4-CO2H 

Anisic    . 

1    4 

184° 

CH3.C,H3(OH)-C02H. 

o-Hydroxytoluic 

1:2-3 

164° 

If                                       •                  • 

m-           ,, 

1:3-4 

177° 

»»                                       •                  • 

P-            .» 

1:4-3 

151° 

»»                                       * 

/3-m-        „ 

1:3-2 

168° 

OH-C,,H4-CH2-CH2-CO,H  . 

Hydro-p-coumaric 

1  :  4 

118° 

C,H5-CH(OH)-CO2H  . 

Mandelic 

— 

118° 

C,H6.CH(CHa-OH).C02H    . 

Tropic    . 

— 

117° 

C,HS-CO-CO2H  . 

Benzoylformic 

— 

65° 

C.H6-CO-CH2-CO2H  . 

Benzoylacetic  . 

— 

103° 

CeH3(OH)2-C02H 

Protocatechuic 

1:3-4 

199° 

C6H3(CH3)(OH)2.C02H 

Orsellinic  (1  -methyl  3  :  5-dihydroxybenzene 

-2-carboxylic        ..... 

1:3:5-2 

176° 

CeH2(OH)3.C02H          .          .' 

Gallic  (3:4:  5-trihydroxybenzenecarboxylic 

3:4:5-1 

221° 

fuged,  and  purified  by  sublimation.  Jessnitzer  (Ger.  Pat.  236,489  of  1910) 
proposes  to  oxidise  with  calcium  hypochlorite  instead  of  with  nitric  acid. 

Benzonitrile,  C6H5-CN,  found  in  the  middle  tar  oils,  gives  pure  benzoic 
acid  when  hydrolysed  (Ger.  Pat.  109,122). 

According  to  Ger.  Pat.  136,410,  benzoic  and  phthalic  acids  are  readily 
obtainable  by  heating  naphthol  or  other  naphthalene  derivative  with  fused 
or  dissolved  alkali  in  presence  of  metallic  oxides  (Mn02,  CuO,  Fe203)  ;  the 
benzoic  acid  is  separated  from  the  mixture  by  distillation. 

Benzoic  acid  is  used  in  medicine,  in  making  certain  aniline  blues,  in  the 
seasoning  of  tobacco,  in  printing  textiles,  and  for  preserving  foodstuffs,1 
although  it  has  not  been  shown  to  be  harmless  when  used  in  this  way  ;  experi- 
ments made  in  the  United  States  in  1910  showed  that  doses  of  1  grm.  per 

1  Of  the  various  methods  for  detecting  benzoic  acid  in  foods,  the  following  may  be  mentioned.  According 
to  Joncscu  (1909)  the  presence  of  benzoic  acid  in  milk  may  be  shown  by  converting  it  into  salicylic  acid  by  means 
of  3  per  cent,  hydrogen  peroxide  diluted  ten  times,  and  then  testing  for  salicylic  acid  with  ferric  chloride  solution 
(  sp.  gr.  1-28)  diluted  ten  times  (as  in  the  examination  of  beer,  see  p.  179).  In  the  case  of  butter,  this  is  acidified 
with  sulphuric  acid  and  distilled  with  steam,  the  distillate  being  tested  as  above  (see  also  Salicylic  Acid). 

II  37 


578  ORGANIC    CHEMISTRY 

day  of  benzoic  acid  or  sodium  benzoate  have  no  injurious  effect.  It  costs 
about  3s.  to  4:8.  per  kilo. 

BENZOIC  ANHYDRIDE,  (C6H5-CO)20,  is  obtained  by  heating  an  alkali  benzoate 
with  benzoyl  chloride : 

C6H5-C02Na  +  C6H5-CO-C1=  NaCl  +  (C6H5-CO)2O, 

or,  according  to  Ger.  Pat.  146,690,  by  heating  nearly  2  parts  of  sodium  chlorosulphonate, 
Cl'SO3Na,  with  3  parts  of  sodium  benzoate;  by  changing  these  proportions,  benzoyl 
chloride  (see  below)  may  be  obtained. 

In  the  cold  it  is  not  decomposed  by  water,  but  on  boiling  it  gives  benzoic  acid.  It 
costs  16s.  to  20s.  per  kilo  according  to  its  purity. 

BENZOYL  CHLORIDE,  C6H5-CO-C1,  is  formed  by  the  action  of  PC16  or  POC13  on 
benzoic  acid,  and  is  obtained  industrially  either  by  the  action  of  chlorine  on  benzaldehyde 
or  from  sodium  chlorosulphonate  (see  above,  Benzoic  Anhydride).  It  is  a  colourless  liquid 
which  boils  at  194°,  and  has  a  very  pungent  odour.  Water  decomposes  it  very  slowly  in 
the  cold  (distinction  from  acetyl  chloride)  giving  hydrochloric  and  benzoic  acids.  It 
reacts  readily  with  many  compounds  in  alkaline  solution,  introducing  into  them  the 
benzoyl  group  (Schotten  and  Baumann's  method).  For  instance,  a  mixture  of  benzoyl 
chloride  with  a  little  potassium  hydroxide  acts  in  the  cold  on  aniline,  forming  Benzanilide,- 
C6H5  •  NH  •  CO  •  C6H5  (white  compound,  melting  at  158°,  and  boiling  unaltered).  With 
hydroxylamine  it  gives  Benzhydroxamic  Acid,  C6H6-CO-NH-OH,  which  gives  a  violet 
coloration  with  ferric  chloride. 

Benzoyl  chloride  is  used  in  the  preparation  of  benzaldehyde  and  of  various  dyes  ;  it 
costs  about  5s.  6d.  per  kilo,  or,  in  the  highly  purified  state,  1 6s. 

ETHYL  BENZOATE,  C6H5-CO2C2H5,  has  an  odour  of  mint,  and  is  obtained  by 
heating  benzoic  acid  with  alcohol  in  presence  of  sulphuric  acid. 

BENZAMIDE,C6H5-CO-NH2,  is  obtained  by  the  action  of  ammonia  (or  ammonium 
carbonate)  on  benzoyl  chloride,  or  by  the  interaction  of  sulphuric  acid  and  benzonitrile. 
It  forms  nacreous  crystals  melting  at  130°,  and  is  soluble  in  boiling  water.  It  forms 
metallic  derivatives  more  easily  than  acetamide. 

BENZHYDRAZIDE,  C6H5-CO-NH-NH2,  is  obtained  from  hydrazine  hydrate  and 
benzoic  ester  ;  with  nitrous  acid,  it  gives 

/N 
BENZAZIDE   (Benzoylazoimide),    C6H5-CO-N/   || ,   which  is  readily  hydrolysed, 

\N 
giving  hydrazoic  and  benzoic  acids. 

HIPPURIC  ACID,  C6H5-CO-NH-CH2-CO2H,  is  obtained  by  heating  benzoic  acid 
with  glycocoll.  It  occurs  in  the  urine  after  ingestion  of  benzoic  acid  or  toluene,  and  is 
found  in  considerable  quantities  in  the  urine  of  horses  and  other  herbivorous  animals.  It 
forms  rhombic  crystals  melting  at  187°,  and  is  soluble  in  hot  water. 

CHLOROBENZOIC  ACIDS,  C6H4C1-CO2H.  The  halogen  enters  preferably  the  meta- 
position  and  nitric  acid  (in  presence  of  concentrated  sulphuric  acid)  gives  mainly  m-Nitro- 
benzoic  Acid,  NO2-C6H4-C02H,  which,  on  reduction,  yields  Azobenzoic  Acids  and 
Aminobenzoic  Acids,  NH2  •  C6H4  •  C02H.  The  latter,  like  glycine,  exhibit  the  functions 

N:  N 
of  both  acids  and  bases  ;  with  nitrous  acid,  they  form  Diazobenzoic  Acids,  C6H4<^  ~  1    ^>. 

ANTHRANILIC  ACID  (o-Aminobenzoic  Acid)  is  formed  in  the  synthesis  of  indigo 
and  also  from  phthalimide.  It  is  prepared  by  boiling  the  potassium  derivative  of 
phthalylhydroxylamine  with  aqueous  sodium  carbonate  : 

OH  +  H20  =  C02  +  OX<^§H. 

\ 

Numerous  patents  have  been  taken  out  for  its  manufacture  (Ger.  Pats.  130,302,  136,788, 
138,188,  145,604,  146,716,  &c.).  It  melts  at  145°,  and  is  largely  used  in  the  manufacture 
of  dyes,  drugs,  and  perfumes.  The  pure  product  costs  64s.  and  the  crude  20s.  per  kilo. 

JOO 
Anthranilic  acid  forms  an  internal  anhydride,  Anthranil,  C6H4/  |    . 

NNH 


TOLUIC,    XYLIC,    AND    CINNAMIC    ACIDS  579 

Of  the  dibasic  Sulphobenzoic  Acids,  C6H4(S03H)(C02H),  the  ortho-isomeride  is  of 
interest,     since    its     imino-derivative    forms     SACCHARIN     (o-Benzoicsulphimide), 

SO 

which  is  a  white  powder  slightly  soluble  in  water,  and  is  500  times 


as  sweet  as  sugar.  Saccharin  is  prepared  as  follows  :  toluene  is  heated  at  100°  with 
concentrated  sulphuric  acid  and  the  mixture  of  o-  and  p-toluenemonosulphonic  acids 
thus  obtained  converted  into  calcium  salt  and  thence  into  sodium  salt.  This  is  dried 
and  distilled  in  presence  of  phosphorus  trichloride  and  chlorine  and  the  o-  and 
p-toluenesulphonic  chlorides  frozen  and  centrifuged  to  separate  the  crystalline  para- 
compound  from  the  liquid  ortho-compound.  With  ammonia,  the  latter  gives  o-toluene- 
sulphamide,  which  is  oxidised  by  permanganate  to  the  potassium  salt  of  o-benzene- 
sulphaminic  acid  and  treatment  of  this  with  an  acid  results  in  the  separation  of  crystals 
of  saccharin.  It  has  no  nutritive  value,  but  is  harmless  in  the  amounts  usually  introduced 
into  foods  ;  in  large  doses,  it  is  antiseptic,  antifermentative,  and  diuretic.  It  melts  at 
224°.  "In  Italy  its  consumption  is  prohibited,  for  fiscal  reasons.  It  costs  40s.  to  48s.  per 
kilo.  With  alkali  carbonates  it  forms  soluble  saccharin  (crystallose). 

Saccharin  was  discovered  in  1878,  and  in  1896  there  were  three  factories  in  Germany 
producing  33,528  kilos  ;  in  1897  four  factories  made  34,682  kilos  ;  in  1898  five  factories 
made  78,363  kilos  and  in  1899  six  factories  130,287  kilos  ;  in  1901  189,734  kilos  were  made, 
and  in  1902  174,777.  Its  sale  is  now  prohibited  in  Germany,  but  six  firms  in  Switzerland 
produce  annually  about  80,000  kilos  which  they  despatch  as  contraband  to  various 
countries.  In  1908  a  fine  of  nearly  £25,000  was  inflicted  at  Domodossola  for  the 
smuggling  of  623  kilos  of  saccharin.  A  pharmacist  in  Hungary  was  found  in  1908  to 
have  sold  saccharin  illegally  to  the  value  of  £20,000. 

In  Russia  56,332  kilos  were  imported  in  1899  when  its  consumption  was  allowed,  but 
after  its  importation  was  prohibited  it  fell  to  831  kilos  in  1906,  although  a  considerable 
amount  is  introduced  without  the  knowledge  of  the  Customs  authorities.  An  International 
Convention  at  Brussels  in  1909  passed  a  resolution  that  all  countries  should  prohibit  the 
use  of  saccharin  in  foods  and  beverages  and  placed  severe  restrictions  on  its  sale. 

TOLUIC  ACIDS,  CH3-C6H4vCOOH.  The  three  isomerid.es  are  obtained 
by  oxidising  the  corresponding  xylenes  with  dilute  nitric  acid  (see  Table, 
p.  577).  p-Toluic  acid  is  formed  also  by  the  oxidation  of  turpentine. 

Phenylacetic  Acid(a-Toluic  acid),  C6H5-CH2-C02H,  is  isomeric  with  the 
toluic  acids,  but  it  gives  benzoic  acid  on  oxidation,  whereas  the  toluic  acids 
give  pJithalic  acids. 

XYLIC  ACIDS,  C6H3(CH3)2-CO2H  ;  various  isomerides  are  known  (see 
Table,  p.  577). 

CUMINIC  ACID  (p-Isopropylbenzoic  Acid),  C3H7-C6H4-CO2H,  is  formed  in  animal 
organisms  by  the  oxidation  of  cymene,  and  is  obtained  by  oxidation  of  Roman  chamomile 
oil  with  permanganate.  It  melts  at  117°  and  yields  cumene  when  distilled  with  lime. 

CINNAMIC  ACID,  C6H5-CH  :  CH-C02H,  is  found  in  storax  and  in  certain 
balsams  (Tolu,  Peru,  &c.),  and  remains  as  sodium  salt  when  these  are  distilled 
with  caustic  soda.  It  is  prepared  according  to  Perkin's  synthesis  (p.  291)  by 
heating  benzaldehyde  with  sodium  acetate  in  presence  of  a  dehydrating  agent 
(acetic  anhydride)  ;  or  by  heating  benzylidene  chloride  (benzal  chloride) 
with  sodium  acetate  in  an  autoclave  at  200°  ;  or  by  the  malonic  synthesis  from 
benzaldehyde  and  ammonia  : 

C6H5-  CHO  +  CH2(COOH)2  =  H20  +  C02  +  C6H5-  CH  :  CH-  COOH. 

Cinnamic  acid  melts  at  133°  and  boils  at  about  300°.  It  readily  forms  addi- 
tive products  owing  to  the  double  linking  in  the  side-chain,  and  on  this  account 
also  reduces  permanganate  in  presence  of  sodium  carbonate  (Baeyer's  reaction, 
p.  88). 


580  ORGANICCHEMISTRY 

According  to  theory,  the  presence  of  the  double  linking  should  result  in 
the  existence  of  two  stereoisomerides  : 

C6H5-OH  C6H5-OH 

II  and  || 

H-OC02H  C02H-OH 

But,  in  addition  to  these,  two  others,  Allocinnamic  and  Isocinnamic  Acids, 
are  known  and  are  apparently  polymorphous  modifications  of  the  maleic 
form,  although  this  question — studied  by  Liebermann,  Michael,  and 
Erlenmeyer,  jun. — has  not  yet  been  completely  decided. 

Cinnamic  acid  costs  16s.  per  kilo,  and  is  used  in  medicine  and  in  the  synthesis 
of  various  perfumes. 

PHENYLPROPIOLIC  ACID,  C6H5  -C  :.  C  -CO2H,  is  obtained  by  heating  the  dibromide 
of  ethyl  cinnamate  with  alcoholic  potash; 

C6H5-CHBr-CHBr-C02C2H5  +  H20  =  2HBr  +  C6H5-C  •  OC02H  +  C2H5-OH. 

It  forms  shining  needles  which  melt  at  137°  and  readily  sublime.     Its  sodum  salt  is  used. 
n  1  to  3  per  cent,  solution  as  an  inhalation  in  cases  of  tuberculosis,  and  costs  £4  per  kilo 
o-Nitrophenylpropiolic  Acid,  obtained  in  a  similar  manner  from  ethyl  o-nitrocinnamate, 
s  used  in  the  synthesis  of  indigo. 


The  basicity  of  these  acids  is  given  by  the  number  of  carboxyl  groups,  and 
the  phenomena  of  isomerism  are  similar  to  those  of  the  dihalogenated  deriva- 
tives. The  carboxyl  groups  may  be  united  directly  to  the  benzene  nucleus  or 
to  side-chains,  and  by  means  of  them  esters,  amides,  acid  chlorides,  &c.,  can 
be  formed. 

PHTHALIC   ACID    (Phenylene-o-dicarboxylic    Acid),    C6H4<£oOH(2) 

is  obtained  by  oxidising  compounds  with  two  lateral  chains,  but  not  by  chromic 
acid,  which  would  partially  destroy  the  benzene  nucleus. 

At  one  time  it  was  prepared  industrially  by  chlorinating  naphthalene  and 
then  oxidising  (Laurent).  But  since  a  few  years  ago  it  has  been  obtained  more 
conveniently  by  oxidising  naphthalene  with  fuming  sulphuric  acid  in  presence 
of  mercury  salts  or,  better,  rare  earth  salts  (thorium,  &c.),  which  act  as  catalysts. 

This  catalytic  process,  which  is  due  to  Sapper,  allows  of  the  recovery  of 
the  whole  of  the  mercury,  while  the  sulphur  dioxide  evolved  is  converted  again 
into  sulphur  trioxide,  so  that  the  oxidation  of  the  naphthalene  may  be  regarded 
as  taking  place  at  the  expense  of  the  oxygen  of  the  air.  This  economical  process 
has  rendered  possible  the  industrial  preparation  of  artificial  indigo. 

The  process  of  fusing  naphthols  with  alkali  in  presence  of  metallic  oxides 
also  seems  to  give  good  results  and  yields  benzoic  acid  at  the  same  time  (see 
above).  According  to  Ger.  Pat.  152,063,  the  electrolysis  of  naphthalene  in 
presence  of  an  acid  solution  of  a  cerium  compound  yields  naphtha quinone  and 
phthalic  acid. 

It  is  a  white,  crystalline  substance  soluble  in  hot  water,  alcohol,  and  ether. 

CO 
It  melts  at  213°  and  is  then  transformed  into  Phthalic  Anhydride,  C6H4<^Q>0, 

which  melts  at  128°  and  boils  at  277°,  but  sublimes  considerably  below  this 
temperature  ;  the  anhydride  has  a  characteristicsodour  and  gives  phthalic  acid 
when  boiled  with  water. 

With  PC15,  phthalic  acid  gives  Phthalyl  Chloride,  C6H4<(^)2>0,  which givesPhthalide, 

f  (C«H6)2 
on  reduction,  and  Phthalophenone,C6H4<CCQ>>O,  with  benzene  (  +  A1C13). 


POLYBASIC    AROMATIC    ACIDS  581 

When  heated  with  phenols  and  sulphuric  acid,  phthalic  anhydride  forms  phthaleins,  e.g. 

C(C6H4-OH)2 
O  +  2C6H5-OH  =  H20  +  C6H4<      >0  (phenolphthalein). 


Phenolphthalein  is  a  yellow  powder  and,  being  a  phenol,  dissolves  in  alkali,  the  solution 
having  a  violet-red  colour  (it  forms  an  excellent  indicator,  see  vol.  i,  p.  97).  When 
heated  with  resorcinol  in  presence  of  zinc  chloride  at  210°,  phthalic  anhydride  yields 
Fluorescein  (resorcinolphthalein), 


6H3(OH)>°' 

which,  even  in  very  dilute  alkaline  solution,  shows  an  intense  greenish  yellow  fluorescence 
while  by  transmitted  light  the  solution  appears  reddish  (see  Triphenylmethane  Dyes). 

Tetrabromofluorescein,  or  eosin,  gives  alkaline  solutions  showing  a  marked  reddish 
green-yellow  fluorescence,  and  is  used  for  dyeing  silk  red,  producing  a  beautiful  fluorescent 
effect  ;  the  colour  is,  however,  not  very  stable,  especially  towards  light. 

CO 
With  dry  ammonia  in  the  hot,  phthalic  anhydride  gives  Phthalimide,  CgH^^pp.^NH, 

which  is  of  importance  since  the  iminic  hydrogen  can  be  replaced  by  metals  and  the  latter 
under  the  action  of  alkyl  halides,  by  alkyl  groups.  The  compounds  thus  obtained,  when 
heated  with  acid  or  alkali,  yield  phthalic  acid  and  a  primary  amine  free  from  secondary 
or  tertiary  amine  (important  general  synthesis  of  primary  amines,  discovered  by  Gabriel)  : 

r*o  r*o 

CtiH4<£Q>NK  +  C2H5Br  =  KBr  +  C6H4<^>NC2H5,  and 
C6H4<£°>NC2H5  +  2H20  =  C6H4<^H  +  (y^.j^ 

Phthalic  acid  is  used  in  the  synthesis  of  indigo  and  of  dyes  of  the  pyronine 
group,  and  is  usually  placed  on  the  market  as  the  anhydride  (although  called 
acid)  at  a  price  of  £6  per  quintal  (65  per  cent,  strength)  ;  chemically  pure,  it 
costs  4s.  per  kilo. 

ISOPHTHALIC  ACID,  C6H4(C02H)2(1  :  3),  is  obtained  by  oxidation  of  colophony 
with  nitric  acid,  or,  in  general,  by  the  oxidation  of  meta-derivatives  of  benzene.  The 
barium  salt  is  soluble  in  water. 

TEREPHTHALIC  ACID,  C6H4(CO2H)2(1  :  4),  is  formed  by  oxidising  oil  of  turpentine 
or  chamomile  oil,  or  by  oxidising  p-toluic  acid  with  permanganate.  It  is  almost  insoluble 
in  water  and  alcohol  and  sublimes  unchanged.  It  gives  a  sparingly  soluble  barium  salt, 
but  does  not  form  an  anhydride. 

POLYBASIC  ACIDS.  The  tri-,  tetra-,  penta-,  and  hexa  -car  boxy  lie  acids  are  known, 
but  are  of  little  practical  importance. 

The  Benzenetricarboxylic  Acids  are  :  TRIMESIC  ACID  (1:3:5)  derived  from 
mesitylene  ;  TRIMELLITIC  ACID  (1:2:4)  obtained  from  colophony  ;  HEMIMELLITIC 
ACID  (1:2:  3). 

The  Benzenetetracarboxylic  Acids  are  :  PYROMELLITIC  ACID  (1:2:4:5),  melting 
at  264°  ;  PREHNITIC  ACID  (1:2:3:4),  melting  at  237°  and  forming  an  anhydride 
Mellophanic  Acid  (1:3:4:5),  which  melts,  and  is  converted  into  anhydride,  at  280°. 

MELLITIC  ACID  (Benzenehexacarboxylic  Acid),  C6(COOH)6,  is  obtained  from 
mellite,  which  is  a  kind  of  mineral  found  in  deposits  of  lignite,  and  consists  of  yellow, 
quadratic  octahedra  of  aluminium  mellitate,  C6(COO)6A12  +  18H2O. 

Mellitic  acid  may  also  be  obtained  by  oxidising  wood  charcoal  with  alkaline  perman- 
ganate. It  forms  needles  insoluble  in  water  and  alcohol  and,  when  heated,  loses  2H2O  and 

1  4 

CO  CO 

2CO2,  forming  Pyromellitic  Anhydride,  0<<CQ>>C6H2<CQ>0,  which  gives  Pyromellitic 

2  5 
Acid,  C6H2(CO2H)4,  with  water. 

Mellitic  acid  cannot  form  substitution  products,  since  all  the  benzene  hydrogens  are 
already  substituted,  but  on  reduction  with  sodium  amalgam  it  readily  yields  Hydromellitic 
Acid,  C6H6(COOH)6,  which  gives  benzene  when  distilled  with  lime. 


582  ORGANIC    CHEMISTRY 

(c)  HYDROXY-ACIDS  AND  PHENOLIC  ACIDS 

These  are  formed  by  the  methods  given  on  p.  575  or  by  oxidising  homologues 
of  phenol  or  fusing  them  with  alkali.  The  basicity  is  given  by  the  number  of 
carboxyl  and  phenolic  groups,  both  of  these  leading  to  salt-formation,  but  the 
basicity  towards  sodium  carbonate  is  determined  by  the  carboxyl  groups  alone. 
When  both  the  carboxyl  and  hydroxyl  groups  are  etherified,  only  the  former 
can  be  subsequently  hydrolysed. 

SALICYLIC  ACID  (o-Hydroxybenzoic  Acid),  OH  •  C6H4-  COOH,  is  the  most 
important  of  the  hydroxy  -acids.  It  is  derived  from  salicin  (glucoside  of  willow 
bark),  which,  when  hydrolysed,  first  gives  glucose  and  Saligenin  : 


I      TT    H    _   P   TT    -*'•  I      (\   XT      O 

±12U      -  ^e^l^QJJ    .  QJJ    '      ^6±112U6' 

Salicin  .  Saligenin  Glucose 

the  saligenin  giving  salicylic  acid  on  oxidation.  The  acid  is  found  as  methyl 
ester  in  the  essence  of  Gaultheria  pracumbens. 

It  is  prepared  industrially  by  heating  sodium  phenoxide  with  carbon  dioxide 
in  an  autoclave  at  140°,  according  to  Kolbe's  process  ;  from  the  resulting  sodium 
salicylate  the  acid  is  liberated  by  treatment  with  a  mineral  acid.  In  Marasse's 
method  a  mixture  of  phenol  and  potassium  carbonate  is  heated  in  presence  of 
C02  at  140°  to  160°. 

It  forms  white  crystals  melting  at  156°,  subliming  at  200°,  and  distilling  in 
superheated  steam  at  170°.  It  is  readily  soluble  in  alcohol  or  in  ether,  and 
1  part  dissolves  in  444  parts  of  water  at  15°  and  in  13  parts  of  hot  water.  When 

/° 

heated  with  POC13  it  gives  the  Internal  Anhydride,  CgH^  I     ,  which  forms 

XCO 
a  white  powder  softening  at  110°  and  melting  at  261°. 

With  bromine  water  it  gives  a  precipitate,  C6H2Br3-OBr,  and  with  ferric 
chloride  it  gives  a  violet  coloration  even  in  alcoholic  solution  (phenol  is  coloured 
only  in  aqueous  solution).  With  lime-water  in  the  hot  it  forms  a  basic  salt, 

and  can  thus  be  separated  from  its  isomerides,  which  do 


not  give  this  reaction. 

It  is  used  as  an  antiseptic  for  preserving  foodstuffs,1  and  in  the  manufacture 
of  dyes  and  perfumes.  Its  sodium  salt  is  largely  used  as  a  medicine. 

When  heated  to  200°  it  loses  C02,  giving  Phenyl  Salicylate  (salol)  : 

20H-C6H4-CO,H  =  C02  +  H2O  +  OH-C6H4-C02C6H5, 

which  is  used  as  an  antiseptic  for  the  intestines. 

Salicylic  acid  costs  £12  14s.  per  quintal.  In  1905  Germany  exported  5018 
quintals  of  the  acid  and  its  sodium  salt. 

Acetylsalicylic  Acid  is  used  in  medicine  under  the  name  aspirin. 

m  and  p-HYDROXYBENZOIC  ACIDS  give  insoluble  basic  barium  salts  and  yield 
no  coloration  with  ferric  chloride  ;  the  m-acid  is  more  stable  to  heat  than  the  o-  or  p-acid. 

Anisic  Acid,  CH30  'C6H4-CO2H,  resembles  the  monobasic  acids  more  than  the  phenols 
and  is  obtained  from  p-hydroxybenzoic  acid,  methyl  alcohol,  potassium  hydroxide,  and 
methyl  iodide,  the  dimethyl  ether  obtained  being  then  partially  hydrolysed. 

Methyl  Salicylate,  OH'C6H4'C02CH3,  forms  90  per  cent,  of  oil  of  Gaultheria,  and  is 
prepared  artificially  by  the  interaction  of  salicylic  acid  (2  parts)  and  methyl  alcohol  (2  parts) 

1  The  examination  of  foods  for  the  presence  of  salicylic  acid  is  carried  out  in  the  same  way  as  with  beer  (p.  179). 
But  baked  starchy  substances  (bread,  <tc.)  contain  maUol,  which  gives  the  same  reaction  as  salicylic  acid  and  is, 
like  the  latter,  volatile.  In  this  case  Jorisscn's  method  must  be  used  in  testing  for  salicylic  acid  :  10  c.c.  of  the 
liquid  distilled  with  steam  arc  treated  with  5  drops  of  10  per  cent,  potassium  nitrite  solution,  5  drops  of  50  per  cent. 
acetic  acid,  and  one  drop  of  10  per  cent,  copper  sulphate  solution.  The  liquid  is  then  boiled  and  in  prescuce 
of  even  less  than  0-0001  grin,  of  salicylic  acid  a  reddish  coloration  forms,  which  rapidly  becomes  blood-red  (H.  C. 
Sherman,  1910). 


GALLIC    ACID:    INK  583 

in  presence  of  concentrated  sulphuric  acid  (1  part).  It  boils  at  224°,  is  used  as  a  perfume, 
and  costs  3s.  6d.  per  kilo. 

p-HYDROXYPHENYLACETIC  ACID,  OH-C6H4-CH2-CO2H,  formed  during  the 
putrefaction  of  proteins  and  occurring  in  the  urine,  gives  a  dirty  green  coloration  with 
ferric  chloride. 

Of  the  Dihydroxybenzoic  Acids,  PROTOCATECHUIC  ACID  (3  :  4-Dihydroxybenzoic 
Acid),  C6Ha(OH)2tCO2H,  forms  shining  scales  or  crystals  soluble  in  water  ;  in  solution  it 
is  coloured  green  by  ferric  chloride,  the  colour  being  changed  to  blue  and  then  to  red  by 
a  little  soda.  It  can  be  obtained  synthetically,  together  with  the  2  :  3-dihydroxy-acid, 
by  heating  catechol  with  ammonium  carbonate,  and  is  prepared  by  fusing  various  resins 
with  alkali.  Like  catechol,  it  exhibits  reducing  properties.  Its  monoethyl  ether  (30CH3) 
is  VANILLIC  ACID,  which  is  formed  by  the  oxidation  of  vanillin  (p.  574)  ;  its  dimethyl 
ether  [(OCH3)2]  is  VERATRIC  ACID,  found  in  the  seeds  of  Veratrum  Sabadilla  ;  and 

its  Methylene  Ether,  C02H-C6H3<Q>CH2,  is  PIPERONYLIC  ACID,  which  is  also 
obtained  by  oxidising  piperinic  acid. 

GALLIC  ACID  (3:4:  5  -  ? rihydroxybenzenecarboxylic  Acid), 
C6H2(OH)3-CO2H,  occurs  naturally  as  glucosid.es  in  various  plants  and  in  tea, 
gall-nuts,  &c.  It  is  formed  by  the  action  of  mould  on  solutions  of  tannin  or 
by  boiling  the  latter  with  dilute  acid  or  caustic  soda. 

It  reduces  gold  and  silver  salts  and  becomes  oxidised  and  turns  brown  in 
the  air.  With  ferric  chloride  it  gives  a  black  coloration,  and,  on  this  account, 
it  is  used  in  making  ink  l ;  its  reducing  properties  are  utilised  in  photography. 

When  pure  it  forms  colourless  needles  (+  H20)  which  decompose  at  200° 
into  carbon  dioxide  and  pyrogallol.  It  is  only  slightly  soluble  in  ether  or  cold 
water  but  dissolves  readily  in  alcohol  or  hot  water. 

Chemically  pure  gallic  acid  costs  about  5s.  per  kilo. 

There  are  a  number  of  hydroxy '-acids  with  hydro xyl  and  carboxyl  groups  in 
the  side-chains  :  mention  may  be  made  of  : 

(1)  COUMARIC     ACID    (o-Hydroxycinnamic    Acid),     OH-C6H4-CH  : 
CH-CO2H,  which  does  not  give  an  anhydride  owing  to  its  fumaroid  structure 
(see  Fumaric  Acid),  while  the  maleic  stereoisomeride,  Coumarinic  Acid,  is 
known  only  as  salts,  since  in  the  free  state  it  immediately  forms  Coumarin, 

0— CO 
C6H4\  |      ;  the  latter  may  also  be  obtained  by  heating  salicylic  acid 

XCH  :  CH 
with  sodium  acetate  (Perkin  synthesis  ;    see  Aldehydes). 

(2)  MANDELIC    ACID,   C6H5-CH(OH)-CO2H ;     of    the    various    stereo- 
isomerides,   that  occurring  naturally  is  laevo-rotatory,   while  that  obtained 
synthetically   (from  benzaldehyde    and    hydrocyanic  acid,   with  subsequent 
hydrolysis)     is     the    racemic    form.    In    solutions    of    the     latter,    certain 
Schizomycetes  destroy  the  d-  and  leave  the   1-isomeride,  whilst   Penicillium 

i  INK  is  made  by  adding  to  aqueous  gallic  acid  or  tannin  ferrous  sulphate  solution  slightly  acidified  with 
acetic  or  hydrochloric  acid  in  order  to  prevent  oxidation  and  the  formation  of  a  black  precipitate.  To  this  brownish 
solution  is  added  a  solution  of  indigo-carmine  or  logwood  to  render  the  writing  visible.  When  the  ink  is  exposed 
on  the  paper  to  the  air,  it  becomes  black  and  insoluble,  owing  to  the  evaporation  or  neutralisation  of  the  acid  by 
the  sizing  of  the  paper  (albumen,  &c.),  and  the  consequent  ready  oxidation  by  atmospheric  oxygen,  which  changes 
the  original  blue  colour  to  a  deep  black. 

To  make  the  ink  adhere  without  spreading,  a  little  gum  is  added,  and  to  preserve  it,  a  little  phenol  [1  Ltre  of 
this  normal  ink  may  be  obtained  from  23-4  grms.  of  tannin,  7-7  grms.  of  gallic  acid,  10  grms.  of  gum,  2-5  grms. 
of  hydrochloric  acid  (as  gas)  or  7-5  grms.  of  the  concentrated  acid,  30  grms.  of  ferrous  sulphate,  1  grm.  of  phenol, 
and  the  rest  water  ;  the  liquid  is  left  at  rest  for  four  days  and  then  decanted  from  the  deposit  and  coloured  with 
indigo-carmine  or  logwood  extract]. 

A  logwood  ink  may  be  obtained  as  follows  :  20  grms.  of  dry  logwood  extract  or  30  grms.  of  the  paste  (hsematei'n) 
are  dissolved  in  800  c.c.  of  water  and  to  the  hot  solution  are  added  15  grms.  of  soda  crystals  (7  grms.  of  Solvay 
soda),  and  then,  drop  by  drop,  and  with  shaking,  100  c.c.  of  a  solution  containing  1  grm.  of  normal  potassium 
chromate  ;  this  process  gives  a  fine  blue-black  tint,  and  the  ink,  which  does  not  attack  steel  pens,  and  dries  easily 
can  be  preserved  by  a  trace  of  phenol. 

Coloured  inks  are  aqueous,  gummy  solutions  of  aniline  dyes.  Copying  inks  are  similar  to  ordinary  writing 
inks,  but  are  more  concentrated,  and  contain  also  gly«erine,  sugar,  dextrin,  calcium  chloride,  &c.,  by  which  the 
writing  is  kept  moist  for  some  time. 


584  ORGANIC    CHEMISTRY 

glaucum  destroys  the  1-  and  leaves  the  d-compound.     Also,  if  the  cinchonine 
salt  of  the  racemic  form  is  prepared,  the  d-salt  crystallises  out  first. 

The  Dihydroxycinnamic  Acids  include :  CAFFEIC  ACID  (see  Chapter  on  Gluco- 
sides),  FERULIC  ACID  and  UMBELLIC  ACID  (p-hydroxy-o-coumaric  acid,  which  is 
readily  transformed  into  its  anhydride,  umbelliferone) ;  a  similar  acid  is  PIPERINIC  ACID, 

3-CH  :  CH-CH :  CH-C02H, 


which  is  formed  in  the  decomposition  of  piperine. 

The  derivatives  of  the  Trihydroxycinnamic  Acids  are  dealt  with  in  the  Chapter  on 
Glucosides  (cesculin  and  daphnin  from  horse  chestnuts  and  Daphne  mezereum,  &c., 
respectively).  Mention  may  be  made  here  of  ^ESCULETIN  (a  Dihydroxycoumarin), 

,O  •  CO 
C6H2(OH)2^  |    ,  and  of  the  isomeric  DAPHNETIN,  which  have  also  been  obtained 

'  \CH:CH 
synthetically. 

TANNIN  (Gallotannic  or  Tannic  Acid),  C14H10O9,  was  studied  originally  by 
Berzelius,  Pelouze,  and  Liebig.  According"  to  Hlasiwetz  (1867)  and  to  U.  Schiff  (1873), 
tannin  is  probably  a  partial  and  mixed  anhydride  of  gallic  acid,  2  mols.  of  which  are 
condensed  with  loss  of  1  mol.  of  water  from  a  carboxyl  and  a  hydroxyl  group  and 
formation  of  a  Digallic  Acid  (or  ether  of  3-gallolylgallic  acid) : 

OH/\C02H 
2  =  H20  + 

OHl       J  OH 

OH  OH  OH 

According  to  the  investigations  of  Nierensteln  (1908)  on  the  acetyl-derivatives  and 
hydrolysis,  commercial  tannin  would  seem  to  be  a  mixture  of  digallic  acid  and 
Leucotannin  (or  ether  of  3-hydroxygallolylgallic  acid) : 

j— CH(OH)— 0— /NcOjjH 


OH  OH 

There  appear,  however,  to  be  various  more  or  less  highly  polymerised  tannins  with 
widely  varying  molecular  weights.  Some  uncertainty  still  prevails  as  to  the  true  molecular 
magnitude  of  tannin.  Paterno  (1907),  from  a  study  of  the  colloidal  solutions,  arrived 
at  molecular  weights  varying  from  430  to  470  (i.e.  C21  ....),  while  Walden  (1898),  by 
the  ebullioscopic  method,  obtained  numbers  between  760  (about  C35  .  .  .  .)  and  1560 
(about  C70  ....),  which  are  sharply  distinguished  from  that  of  digallic  acid  (332). 
P.  Biginelli  (1911),  on  the  basis  of  the  property  shown  by  tannin  of  forming  additive 
products  with  water, >  alcohol  and  ether  [e.g.  C41H32O26,  C4H10O  (ether),  which  is  stable 
even  in  a  vacuum  and  is  analogous  to  the  oily  compound,  C41H32O25,  6C4H10O,  7H20, 
previously  obtained  by  Pelouze,  and  to  others  of  Biginelli's  compounds,  namely,  C41H32O25, 
6C4H100;  C41H32O26,  6C2H5-OH,  and  C41H32026,  5H20],  and  also  on  the  loss  of  C02 
and  H20  with  formation  of  Hexahydroxybenzophenone,  C13H10O7,  when  tannin  is  heated 
in  aqueous  solution  with  lead  dioxide  (the  C02  liberated  was  estimated),  holds  that  tannin  has 
the  formula  C41H32025,  and  that  it  is  probably  a  glucoside.  It  was,  indeed,  observed  by  Liebig 
and  also  by  Hlasiwetz  that  when  tannin  is  boiled  with  dilute  sulphuric  acid  it  decomposes 
into  gallic  acid  and  dextrin  or  gum  (reacting  with  6H20)  ;  but  Etti  (1884)  and  Lowe  found 
that  tannin  purified  with  ethyl  acetate  does  not  yield  saccharine  substances  (dextrin,  &c.). 

Tannin  is  widespread  in  nature  and  occurs  in  abundance  in  sumac  (Rhus 
coriaria),  gall-nuts  and  oak-galls,  which  are  pathological  excrescences  caused 
by  incision  of  the  oak  branches  by  insects.  To  extract  the  tannin,  the  gall-nuts 
are  ground  to  a  coarse  powder,  which  is  treated  in  a  battery  of  diffusors  similar 
to  those  used  for  extracting  beet-sugar  (see  p.  451).  The  crude  aqueous  solution 
of  tannin  thus  obtained  is  filtered  through  a  battery  of  filters  and  extracted, 


TANNIN  585 

in  a  closed  copper  vessel  fitted  with  a  stirrer,  with  crude  ether  (aqueous  or  not 
free  from  alcohol).  After  the  liquid  has  been  left  at  rest  in  vats  for  8  to  10 
days,  the  dense  lower  layer  containing  the  tannin  is  decanted  and  freed  from 
ether  by  distillation.  The  evaporation  of  the  water  present  is  effected  in  heated, 
rapidly  rotating  drums,  or  on  zinc  plates  placed  in  desiccators.  The  dry  mass 
is  then  subjected  to  short  and  gentle  treatment  with  steam — a  very  soft,  pale, 
ethereal  tannin  being  thus  obtained.  Tannin  solutions  are  also  concentrated 
under  reduced  pressure  in  multiple-effect  apparatus  (see  Sugar,  p.  461). 

Aqueous  or  Alcoholic  Tannin,  which  is  extracted  by  water  or  alcohol  without  being 
purified  by  means  of  ether,  is  less  pure. 

Pure  tannin  forms  a  pale  yellow  light  powder  or  sometimes  crystals.  It  is  darkened 
in  colour  by  light,  turns  brown  in  the  air,  and  dissolves  in  its  own  weight  of  water,  double 
its  weight  of  alcohol  or  eight  times  its  weight  of  glycerol  or  ethyl  acetate.  It  is  almost 
insoluble  in  ether,  benzene,  chloroform,  petroleum  ether  or  carbon  disulphide.  With  iron 
salts  it  forms  a  bluish  black  precipitate  and  with  albumin  or  starch,  a  gelatinous  precipitate. 
In  aqueous  solution  it  is  dextro-rotatory  (  +  15°  to  -f  20°). 

According  to  the  degree  of  purity,  it  costs  from  £10  to  £14  per  quintal,  and  it  is  used 
mainly,  in  conjunction  with  antimony  salts,  as  a  mordant  in  the  dyeing  of  cotton  with 
basic  dyes.  It  is  employed  also  in  making  ink  and,  along  with  gelatine,  in  clarifying 
beer  and  wine,  forming  with  the  gelatine  a  gummy  precipitate  which  gradually  settles 
and  carries  down  with  it  the  suspended  matter  of  the  liquid. 

In  1905  Germany  exported  7040  quintals  of  pure  tannin  of  the  value  £80,000,  while 
in  1909  the  exports  were  8135  and  the  imports  772  quintals. 

In  1908  Turkey  produced  70,000  tons  of  valonia  (Quercus  cegilops),  the  harvesting  of 
which  employs  70,000  workpeople. 

The  United  States  consumed  in  1909  different  tanning  materials  to  the  value  of 
£4,200,000. 

Imports  into  England  amounted  to  : 

1910  1911 

Tanning  extracts       .         ,          .     £749,410  ..  £739,329 

Tanning  barks            .          .          ..     225,642  ..  243,128 

Myrobolams   -.          .          .          .       225,168  ..  138,844 

Sumac      .          .          .         •.          .       105,620  . .  103,981 

Valonia 169,948  ..  121,227 

Gall-nuts.          .          .          ...       37,329 

Powdered  barks  or  woods  are  used,  either  before  or  after  extraction,  in  tanning  hides. 

These  tannin  extracts  [from  oak  bark  (containing  10  to  20  per  cent,  of  tannin),  mimosa 
(30  per  cent.),  leaves  and  twigs  of  sumac  (15  to  30  per  cent.),  valonia  (20  to  45  per  cent.), 
Asiatic  gall-nuts  (55  to  75  per  cent.),  European  gall-nuts  (25  to  30  per  cent.),  divi-divi  (40  per 
cent.),  myrobolams  (30  per  cent.),  quebracho  wood  (22  per  cent.),  horse-chestnut  bark  (2  to 
3  per  cent.),  catechu  or  cutch  (40  or  50  per  cent.),  &c.],  are  now  rationally  prepared  on 
an  enormous  scale  by  extracting  the  finely  divided  material  with  hot  water  in  batteries 
of  diffusors.  The  dilute  solutions  (1-5°  to  3°  Be.)  are  filtered  and  then  concentrated  in  a 
triple-effect  vacuum  evaporator  (see  p.  461)  to  the  density  25°-30°  Be.  For  some  years, 
however,  certain  extracts  have  been  clarified  or  partially  decolorised  with  alkali  sulphite, 
bisulphite,  or  hydrosulphite  (patented  by  Lepetit,  Dollfus  and  Gansser,  1896)  before 
concentration.  The  bisulphite  renders  the  extracts  much  more  soluble,  as  it  converts 
part  of  the  tannin  substances  into  soluble  sulphonic  compounds,  while  in  the  resinous 
extract  of  quebracho  it  also  causes  decomposition  of  a  glucoside  present,  giving  the  product 
the  property  of  imparting  a  yellow  colour  to  skins  with  an  aniline  mordant.  Decoloration 
is,  however,  due  more  especially  to  the  hydrosulphite  either  added  directly  (Lepetit's 
patent)  or  produced  by  reduction  of  the  bisulphite  added  to  the  extract  (1)  by  zinc  or 
aluminium  dust  (Eng.  Pat.  11,502  of  1902) ;  (2)  by  treating  the  crude  extract  with  aluminium 
sulphate  and  sodium  bisulphate  and  then  heating  under  pressure  at  120°-130°  (U.S.  Pat. 
740,283)  ;  (3)  by  treating  the  extract  with  a  mixture  of  formaldehyde-bisulphite  and 
forinaldehyde-sulphoxylate  (Fr.  Pat.  362,780) ;  or  (4)  according  to  the  recent  patent  of 
L.  Dufour  (Genoa),  by  reducing  the  sulphite  with  thiosulphate,  and  then  with  formaldehyde. 
Use  has  also  been  made  of  the  waste  sulphite  liquors  from  the  manufacture  of  cellulose 


586 


ORGANIC    CHEMISTRY 


(Ger.  Pat.  132,224  and  152,236  ;  U.S.  Pat.  909,343,  January  1909),  of  aluminium  amalgam 
(Ger.  Pat.  220,021),  and  of  chromous  salts  (chloride,  sulphate,  acetate,  &c.) 

An  interesting  method  of  clarifying  quebracho  extract  and  rendering  it  soluble  even 
in  the  cold  is  that  of  A.  Redlich,  L.  Pollak,  and  C.  Jurenka  (Ger.  Pat.  212,876  of  1908) : 
The  paste  deposited  from  the  crude,  cooled  extract  is  shaken  for  six  to  seven  hours  with 
1  part  per  thousand  of  soda  at  50°  to  100°,  50  litres  of  the  red  solution  thus  obtained  being 
mixed  with  1000  litres  of  the  crude  extract  previously  decanted  and  the  whole  left  to 
stand.  A  flocculent  deposit  is  thus  obtained  and  a  pale  solution  of  pure  extract  which  is 
decanted  off  and  can  be  concentrated  ;  the  flocculent  precipitate  can  be  dissolved  again 
in  dilute  soda  and  used  to  clarify  further  quantities  of  crude  extract.  Any  excess  of  red, 
alkaline  solution  may  be  employed  for  clarifying  extracts  of  sumac,  &c. 

The  price  of  tanning  extracts  is  roughly  proportional  to  their  content  of  tannin  or 
tannin  substances,1  which  may  vary  from  20  per  cent,  to  50  per  cent.,  but  for  a  given 
content  of  tannin,  extracts  rich  in  red  or  orange  colouring-matters  have  the  greater  value  ; 
these  matters  are  estimated  in  special  colorimeters  or  in  the  spectroscope.  A.  Gansser 
has  recently  (1909)  suggested  the  replacement  of  the  direct  test  on  hide  by  one  on  strips 
of  animalised  cotton  (the  latter  being  immersed  in  a  bath  of  gelatine  and  then  in  one  of 
formaldehyde)  ;  the  resultant  colour  on  the  textile  is  similar  to  that  obtained  on  hides. 

In  1905  Germany  imported  58,000  quintals  of  sumac  (£40,550),  139,054  quintals  of 
quebracho  extract  (£257,250),  and  126,315  tons  of  quebracho  wood  (£600,000),  145,000 
quintals  of  quebracho  extract  (£254,800)  being  exported. 

The  chestnut  extract  produced  in  Corsica  amounted  to  22,032  tons  in  1906,  to  18,275 
tons  in  1907  (the  diminution  being  due  to  strikes),  and  to  25,000  tons  in  1909. 

The  United  States  consumed  about  70,000  tons  of  solid  quebracho  extract  in  1908. 

For  the  manufacture  of  tannin  extracts  (e.g.  from  chestnut  wood)  to  pay,  at  least 
300  quintals  of  wood  must  be  treated  per  day  ;  the  plant  costs  over  £8000. 

TANNING  OF  HIDES.  The  hides  of  oxen,  horses,  sheep,  &c.,  even  when  freed  from 
hair  and  flesh  (i.e.  in  the  form  of  corium),  do  not  keep  and  readily  putrefy  during  drying 
or  in  presence  of  moisture.  When  dressed  (this  was  carried  out  as  early  as  2000  B.C.),  and, 
more  especially,  when  tanned,  the  hides  are  more  tenacious  and  resistant,  do  not  putrefy, 
and  do  not  gelatinise  with  boiling  water,  since  the  fibres  on  which  the  tanning  material 
is  fixed  (to  the  extent  of  30  per  cent,  or  even  more)  do  not  agglutinate  during  drying,  and 
hence  remain  fibrous  and  do  not  become  compact  and  horny.  The  corium  or  derma, 
i.e.  the  fibrous  substance  of  the  skin,  is  converted  by  tanning  into  leather.2  Rational 

ANALYSIS   OF  TANNING   MATERIALS.     A  solution  is  prepared  containing  not  more  than  0-6  to 

0-8  grra.  of  dry  residue  per  litre ;  for  this  purpose  9  to  10  grins,  of  solid  extract  or  15  to  20  grms.  of  liquid  extract  are 
dissolved  in  a  litre  of  tepid  water.  Of  the  various  analytical  methods,  the  least  inexact 
is  that  of  Procter,  which  was  accepted  by  the  International  Congress  of  Leather-Trades 
Chemists  at  Turin,  1904.  The  amount  of  total  soluble  substances  is  determined,  the 
difference  between  this  and  the  non-tannins  (not  fixed  by  powdered  hide)  giving  the 
tannins. 

The  total  soluble  substances  are  determined  by  evaporating  100  c.c.  of  the  clear,  filtered 
solution  to  dryness,  and  drying  the  residue  at  100°  to  105°  until  of  constant  weight. 

Non-tannins.  Powdered  hide  of  the  best  quality  is  employed.  With  this  is  filled  a 
glass  bell  or  funnel  (Fig.  410),  holding  about  30  c.c.  and  3-5  cm.  high  and  3  cm.  wide; 
the  funnel  is  fitted  with  a  rubber  stopper,  through  which  passes  a  capillary  glass  tube 
(2  mm.  diameter)  bent  in  the  form  of  a  syphon.  The  short  limb  of  the  tube  pene- 
trates 1  cm.  below  the  stopper,  and  its  end  is  surrounded  with  cotton-  or  glass-wool  to 
retain  the  hide.  The  funnel  holds  about  7  grms.  (not  less  than  5)  of  slightly  compressed 
powdered  hide,  and  the  mouth  of  the  funnel  is  closed  by  well-washed  muslin  tied 
tightly  on.  The  funnel  is  arranged  almost  on  the  bottom  of  a  200  c.c.  beaker,  con- 
taining a  little  of  the  filtered  tannin  solution,  and  is  left  for  an  hour  so  that  the  hide 
powder  may  become  moistened  uniformly.  The  beaker  is  then  filled  with  the  tannin 
solution  and  suction  applied  to  the  long  limb  of  the  syphon  (about  20  cm.  longer  than 
the  short  limb)  so  that  about  90  to  100  c.c.  flows  out  in  1-5  to  2  hours.  The  first 
30  c.c.  or  so  of  the  filtrate  is  discarded — until,  indeed,  a  small  portion  fails  to  give  a 
turbidity  with  the  liquid  obtained  by  treating  2  grms.  of  the  hide  powder  with  60  c.c. 
of  distilled  water  and  filtering.  Of  the  clear  liquid  free  from  tannin  substances, 
50  c.c.  are  evaporated  in  a  platinum  dish  and  the  residue  dried  at  100°  to  105°,  until 
of  constant  weight.  This  weight  is  multiplied  by  2  and  subtracted  from  the  total 
soluble  substances  (see  above). 
"  THEORY  OF  TANNING.  In  the  first  half  of  last  century,  Davy,  Seguin,  Dumas,  and  Berzelius  regarded 

the  absorption  of  tannin  by  hides  as  a  chemical  reaction.     In  1858  Knapp  defined  leather  as  an  animal  skin  the 

fibres  of  which  do  not  adhere  during  drying  owing  to  the  pores  separating  the  fibres  being  filled  with  the  tannin  ; 

tanning  would  hence  be  a  simple  physical  phenomenon.     Similar  views  were  expressed  by  Reiner  (1872),  Heinzerling 

(1882),  Schroder  and  Passler  (1892). 

Th.  Koruer  (1898-1903)  also  regarded  it  as  a  physical  process,  since  neither  the  tanning  material  nor  the  fibres 

constituting  the  hides  are  clcctrolytically  dissociated,  and  therefore  cannot  combine  to  form  a  kind  of  salt.     Herzog 

Adler,  and  Wislicenus  (1904)  also  supported  the  physical  theory. 


FIG.  410. 


THEORY    O'F    TANNING  587 

tanning  was  introduced  only  when  the  anatomical  structure  of  the  skin  became  exactly 
known  and  the  effects  of  tanning  materials  on  the  different  parts  of  the  hide  were  studied. 
Various  methods  of  tanning  are  in  use :  (a)  Mineral  Tanning  or  tawing,  by  means  of  alum 
and  sodium  chloride  ;  (6)  Oil  Tanning  or  chamoising,  with  fatty  materials  ;  (c)  Ordinary 
Tanning  with  tannin  substances  ;  (d)  Chrome  Tanning,  using  chromium  salts  (tanning 
with  formaldehyde,  proposed  by  Trillat  and  Payne  ;  with  quinone  by  Meunier  and 
Seyewetz  ;  with  naphthols  by  Weinschenck  ;  with  rare  earths  by  Garelli ;  with  fatty  acids 
by  Knapp,  or  with  the  corresponding  ammonium  soaps  by  Garelli  and  Corridi,  1909.) 

The  preparation  of  the  skins  for  tanning  (swelling,  unhairing,  &c.)  is  carried  out  as 
described  below  under  ordinary  tanning. 

(1)  Mineral  Tanning  or  tawing  is  frequently  used  for  light  lamb,  sheep,  and  goat  skins, 
which,  after  unhairing  (see  later),  are  passed  into  the  limes  and  are  then,  just  as  in  ordinary 
tanning,  swelled  in  an  acid  bath,  which  also  removes  all  the  lime.  They  are  then  placed 
in  the  tanning  vat  containing  alum  or  sodium  chloride  solution,  without  impregnating 
them  with  fatty  substances.  For  twenty  hides,  about  1500  grm.  of  alum  and  500  grm. 
of  sodium  chloride  are  dissolved  in  50  litres  of  tepid  water.  The  hides  are  well  saturated 
with  this  bath  and  are  heaped  up  still  wet  for  two  or  three  days,  after  which  they  are  pressed, 
washed,  and  allowed  to  dry  in  the  air. 

The  finishing  of  the  tanned  hides  is  carried  out  as  described  later. 

As  it  has  been  established  that  the  hide  is  capable  of  absorbing  at  its  surface  like  a  colloidal  solution,  Stiassny 
(1908)  holds  that  tanning  consists  simply  of  a  physical  absorption,  since  tannin  reacts  with  scarcely  any  of  the 
known  hydrolytic  products  of  hides.  Just  as  colouring-matters  are  fixed  by  carbon,  silica,  and  alumina  without 
there  being  any  special  groups  to  effect  combination,  so  also  in  tanning  all  the  known  phenomena  support  the 
physical  absorption  hypothesis. 

According  to  Stiassny,  every  tanning  process  consists  in  the  absorption  of  a  dissolved  colloidal  substance  by 
the  gel  of  the  hide  and  in  simultaneous  secondary  transformations  (polymerisations,  oxidations,  &c.),  to  which  the 
absorbed  matter  is  subjected  by  the  catalytic  action  of  the  hide,  and  which  render  the  absorbed  tannin  insoluble 
and  the  process  irreversible.  This  is  more  a  physico-chemical  than  a  physical  theory. 

Konnstcin  (Vienna)  also  regards  the  phenomena  as  a  physical  one,  owing  to  the  absence  of  stoicheiomctric 
relations. 

On  the  other  hand,  Miintz  (1870)  and  Schreiner  (1890)  hold  that  tanning  must  be  due  to  a  chemical  phenomenon, 
since  the  same  hide  always  absorbs  the  same  maximum  amount  of  a  given  tanning  material,  but  Schroder  and 
Piisslcr  advance  the  objection  that  below  the  limit  of  maximum  absorption,  the  quantity  fixed  varies  with  the 
concentration  of  the  bath,  there  being  no  stoichciometric  relations  characteristic  of  chemical  combination. 

Suida,  Gelmo,  and  Fahriou  (1903-1908)  revert  to  the  chemical  theory,  and  assert  that,  as  tanning  is  preceded 
by  treatment  with  acid  or  mordant,  slight  dissociation  or  hydrolysis  may  occur  (as  in  the  case  in  the  dyeing  of  wool) 
Further,  hide  powder  fixes  substantive  dyes  better  than  wool  itself,  and  that  the  combination  docs  not  exhibit 
stoicheiometric  proportions  is  explained  by  the  fact  that  the  hide  consists  of  compact  fibres  and  not  of  separate 
molecules  as  in  solution,  so  that  the  tanning  liquor  penetrates  only  slowly  into  the  interior  of  the  mass,  and  is 
gradually  impoverished  and  exhausted. 

Fahrion  (1908-1910)  points  out  that  in  tanning  with  formaldehyde  there  can  be  no  question  of  colloidal  material 
(as  with  tannin),  and  with  regard  to  the  elimination  of  alum  or  tannin  from  leather  by  the  mere  action  of  water, 
this  is  due  to  pseudo-tanning,  i.e.  to  the  formation  of  labile,  readily  hydrolysable  compounds,  the  tannin  of  which 
becomes  distributed  between  the  hide  and  the  water.  With  reference  to  the  non-stoicheiometric  relations,  he  observes 
that  the  fixation  of  more  tannin  from  concentrated  than  from  dilute  solutions  is  in  accord  with  the  law  of  mass 
action  for  reversible  chemical  reactions. 

According  to  lleidcnhain,  Zacharias,  and  Fahrion  (1908),  both  the  dyeing  and  the  tanning  process  occur  in 
two  phases,  the  absorption  and  penetration  of  the  tanning  substance  and  the  subsequent  chemical  combination 
of  this  substance  with  the  hide.  Garelli  (1907-1910),  from  the  results  of  his  tanning  experiments  with  rare  earths 
(ceria,  thoria,  zirconia),  supports  this  theory,  and  holds  that  all  substances  which  in  aqueous  solution  can  undergo 
hydrolysis  forming  basic  hydroxides  or  salts  (like  chromium,  iron,  and  aluminium  salts)  arc  capable  of  tanning 
hidi's  (i.e.  the  hide  hydrolyses  and  decomposes  the  salts,  which  thus  deposit  hydrates  or  basic  salts  on  the  fibres 
of  the  corium  or  derma,  the  fibres  and  the  salts  combining  to  form  leather).  Thus,  Garelli  effected  tanning  with 
the  rare  earths,  i.e.  with  compounds  of  the  trivalent  (cerium,  lanthanum,  and  didymium)  or  tetravalent  elements 
(cerium,  thorium,  and  zirconium  ;  Zacharias  had  used  stannic  salts  in  1903),  and  the  tanning,  as  when  alum  is  used, 
is  facilitated  by  sodium  chloride  (this  was  not  used  with  eerie  salts,  which  would  generate  chlorine).  The  most 
effective  tannings  are  those  in  which  an  oxidation  plays  a  part  (the  metals  pass  from  the  higher  to  the  lower  valency) 
and  those  with  alum,  which  cannot  give  salts  of  lower  valency  but  are  not  very  stable,  and  do  not  resist  even 
the  prolonged  action  of  cold  water  (pseudo-tanning).  Chromium  salts  are  reduced  to  oxides  by  the  skin  and  fixed, 
while  oils  and  fats  must  be  oxidised  (to  hydroxy -acids),  as  otherwise  the  tanning  is  not  complete. 

It.  Lepetit  (Ann.  d.  Soc.  chim.  di  Milano,  1907,  p.  83)  asserts  that  in  the  tanning  of  sole  and  upper  leather  it 
is  not  sufficient  to  effect  separation  and  stabilisation  of  the  fibres,  but  that  it  is  necessary  to  produce  swelling  and 
tilling  of  the  interstices  between  the  fibres  with  phlobaphenes.  These  arc  colloidal  substances  dissolved  or  suspended 
in  the  tannin  extracts  and  consisting  partly  of  internal  anhydrides  of  soluble  tannins  (see  p.  582)  and  partly  of 
condensation  products  of  formaldehyde  with  polyphenols  and  phenolcarboxylic  acids  derived-  from  the  tanning 
vegetable  organisms.  Indeed,  according  to  Nierenstein,  the  products  of  the  reaction  between  formalin  and  poly 
phenols  exhibit  tanning  properties,  and  at  the  present  time  glove  leather  is  successfully  tanned  by  formaldehyde 
(Trillat  and  Payne).  Also  Weinschenck  (1907-1908)  stated  that  a-  and  /3-naphthols  in  presence  of  formaldehyde 
are  able  to  tan  hides,  but  this  is  denied  by  Stiassny  and  llicevuto  (1908).  In  tanning  with  quinone  derivatives 
(suggested  by  Meunier  and  Seyewetz)  leather  is  formed,  owing  to  the  hydroquinone  derived  from  the  quinone 
reacting  with  the  amino-groups  of  the  proteins.  With  formaldehyde,  there  is  probably  production,  by  aldol 
condensation,  of  complex  colloidal  polymerides  of  formaldehyde  (especially  in  presence  of  alkali  carbonate),  these 
reacting  with  aminic  complexes  in  the  same  way  as  formaldehyde  and  the  aldols  react  with  aniline  (see  p.  558). 
Thuau  (1909)  found  that  if  the  hides  are  previously  treated  with  formaldehyde  .subsequent  chrome  tanning  is 
hastened. 


588  ORGANIC    CHEMISTRY 

Mineral  tanning  is  usually  a  rapid  process,  and  the  alum  combines  with  the  corium 
and  preserves  it,  but  the  leather  is  not  so  lasting  as  that  prepared  with  tannin  and  can  still 
be  gelatinised  by  prolonged  boiling  with  water. 

Chromium  salts  (the  alum  and  chloride)  are  often  used  nowadays  in  place  of  alum  and 
sodium  chloride. 

(2)  Chrome  Tanning  has  assumed  considerable  importance  of  recent  years  (since  1895), 
as  it  is  rapid  and  furnishes  boot  leather  highly  resistant  to  wet  ;  it  is  often  used  also  for 
girths,  &c.  (see  later,  Rapid  Tanning). 

This  method  of  tanning  can  be  carried  out  in  two  baths  or  in  a  single  bath.  In  the 
first  case,  the  prepared  hides  are  steeped  in  a  cold  bath  containing  40  grms.  of  dichromate 
and  40  grms.  of  hydrochloric  acid  for  every  four  litres  of  water  and  for  every  kilo  of  hide. 
Only  one-half  of  the  reagents  are  added  to  the  bath  at  first,  the  hides  being  stirred  with 
a  reel  for  2  to  3  hours,  after  which  the  remainder  of  the  reagents  is  added  "and  the  stirring 
continued  for  1  to  2  hours.  The  hides  are  then  removed  from  the  bath,  allowed  to  drain, 
stretched,  and  placed  in  the  reducing  bath  containing  105  grms.  of  sodium  thiosulphate 
per  4  litres  of  tepid  water  and  per  kilo  of  hide.  Here  they  are  stirred  for  half  an  hour, 
after  which  50  grms.  of  hydrochloric  acid  are  gradually  added  (in  the  course  of  1  to  2  hours) 
per  kilo  of  hide  ;  the  hides  are  finally  rinsed  with  water  and  the  tanning  is  at  an  end. 
When,  as  is  now  more  commonly  the  case,  a  single  bath  is  used,  this  contains  a  solution 
of  either  basic  chromium  oxychloride,  Cr2(OH)5Cl,  and  common  salt,  or  chromo-base, 
which  is  a  basic  sulphate  prepared  by  the  firm  of  Lepetit,  Dollfuss,  and  Gansser  ;  the 
procedure  is  as  in  the  preceding  case.  The  use  of  chromium  lactate  has  been  recommended, 
since  lactic  acid  reduces  chromium  salts,  even  in  the  cold. 

(3)  Oil  Tanning  or  chamoising.     This  is  used  to  obtain  very  soft  leather  for  gloves, 
clothing,  &c.     Deer,  stag,  lamb,  kid  skins,  &c.,  are  smeared  or  rubbed  with  various  fats 
(fish  oil,  wool  fat,  paraffin,  egg-yolk,  alum,  carbolic  acid,  sodium  chloride,  &c.),  the  absorp- 
tion of  which  is  effected  by  repeated  working  of  the  skins,  followed  by  drying  in  tepid 
chambers  ;    the  skins  are  thus  rendered  impermeable,  while  they  can  be  washed  many 
times  without  losing  their  tanning.     The  superficial  fat  is  finally  removed  by  washing  in 
soda  solution,  the  emulsion  thus  formed,  known  as  degras  (see  p.  389)  being  used  for  currying 
ordinary  hides. 

Heavier  hides  (cow,  horse,  ox,  buffalo)  intended  for  saddlery  are  subjected  to  mineral 
tanning  (without  being  treated  with  lime)  and  afterwards  to  a  kind  of  oil  tanning  which 
imparts  to  the  leather  considerable  resistance  to  tension. 

(4)  Ordinary  Tanning  (vegetable  tanning).     The  fresh  hides  as  they  come  from  the 
slaughterers  are  termed  green  hides,  and  in  this  condition  an  ox-hide  will  weigh  from  30  to  40 
kilos,  its  weight  being  reduced  to  one-half  by  tanning.     Many  hides  are  imported  from 
South  America  in  the  dried  and  salted  or  smoked  state.     Ox-hides  give  the  heaviest 
leather  for  boot-soles,  while  for  lighter  soles  cow-hide  is  used  ;    the  uppers  are  made 
preferably  from  calf-skin.     Saddles  are  made  from  horse-hide,  pig-skin,  and  seal-skin, 
while  sheep-skin  is  used   for   bookbinding   leather   and  goat-skin  for   morocco  leather. 
Deer-skin,  goat-skin,  &c.,  are  tanned  with  oil  to  obtain  chamois  or  buff  leather  (see  above). 

The  hides  are  first  softened  by  soaking  for  2  days  or  longer  (according  as  they  are  green 
or  dry)  in  water,  which  removes  blood  and  other  adherent  impurities.  They  are  then 
placed  on  a  "  beam  "  (Fig.  411)  and  scraped  on  the  flesh  side  with  a  curved  knife  (Fig.  412), 
which  is  drawn  across  them  horizontally.  They  are  then  soaked  for  24  hours,  scraped 
again,  washed  in  water  for  a  few  hours,  thrown  on  the  beam  and  allowed  to  drain.  This 
operation  is  hastened  if  the  softened  hides  are  subjected  to  fulling  in  a  revolving  vessel 
(Fig.  413)  or  in  a  vat  containing  cold  water  in  which  they  are  worked  with  wooden  mallets. 

In  order  to  remove  the  hair  fixed  in  the  epidermis  (not  in  the  corium),  the  epidermis 
must  be  attacked  and  almost  destroyed,  this  being  effected  in  various  ways  (by  putrefaction, 
lime,  or  sulphides).  Putrefaction  ("sweating")  is  carried  out  by  salting  the  flesh  side 
of  the  hides  or  sprinkling  them  with  crude  acetic  acid,  bending  the  hides  in  two  longi- 
tudinally with  the  hair  outside  and  stacking  them  in  tanks  or  in  a  warm  chamber  (30°  to 
50°)  ;  fermentation  soon  sets  in,  accompanied  by  heating  and  evolution  of  ammonia, 
the  hides  being  then  unhaired  on  the  beam  with  a  suitable  knife.  In  order  to  avoid  the 
possibility  of  excessive  heating,  the  hides  are  sometimes  placed  in  cement  troughs  fitted 
with  perforated,  wooden,  false  bottoms,  water  being  sprayed  on  to  the  hides  at  the  top, 
so  that  the  temperature  is  kept  down  to  10°  to  12°  ;  after  8  to  12  days  the  hides  can  be 


TANNING    PRACTICE  589 

readily  unhaired.  The  more  delicate  skins  of  small  animals  are  treated  with  sulphides, 
being  smeared  with  rusma,  which  consists  of  a  mixture  of  1  part  of  arsenic  sulphide 
(orpiment)  with  2  to  3  parts  of  slaked  lime  ;  calcium  hydrosulphide  is  also  used  and  gives 
better  results.  In  recent  years,  sodium  sulphide  has  also  been  used  for  heavy  hides,  unhair- 
ing  being  easily  carried  out  by  scraping  the  hides  (after  washing)  with  a  knife  against  the 
set  of  the  hair,  the  operation  being  facilitated,  if  necessary,  by  sprinkling  a  little  sand  or 
ashes  on  the  hide  ;  the  hair  serves  for  the  manufacture  of  felt,  but  that  treated  with 
sulphide  is  converted  into  fertiliser.  When  unhaired,  the  hides  are  well  washed  in  water 
and  beaten  on  a  large  beam  with  the  hair  side  uppermost  ;  if  necessary,  the  removal  of 
the  flesh  is  then  completed  by  means  of  a  knife,  the  useful  part  of  the  hide,  i.e.  the  corium, 
then  remaining. 

The  hides  have  by  this  time  lost  about  12  per  cent,  in  weight,  and  those  which  have  been 
limed  are  next  kept  for  two  or  three  days  in  several  successive  infusions  of  barley  flour  or  bran 
("  bran  drench  ")  in  active  acid  fermentation  ;  to  these  are  added  sulphurous  or  sulphuric 
acid,  lactic  acid  (or  better,  according  to  Boekringer,  Ger.  Pat.  234,584  of  1909,  a  solution  of 
lactic  anhydride  in  ammonium  lactate),  or  acetic  acid,  the  calcium  soaps  on  the  hides 
being  thus  decomposed  ;  the  acids  separate  at  the  surface  and  the  soluble  calcium  salts 


FIG.  411. 


FIG. 412.  FIG.  413. 

are  eliminated  by  washing  (at  one  time,  mixtures  of  dog  and  bird  dung  with  water  were 
used,  the  action  of  these  being  due  to  enzymes  and  amine  hydrochlorides).  After  a  few 
days  the  hides  swell  up  to  double  their  original  size  and  become  yellowish  and  transparent. 
Excessive  swelling  is  prevented  by  the  addition  of  a  little  tanning  material  to  the  infusion. 
All  these  preparatory  operations  are  required  to  make  the  material  to  be  tanned  more 
permeable  and  more  uniform  in  its  behaviour  towards  the  tanning  agents,  which  are 
fixed  to  the  extent  of  about  30  per  cent,  (calculated  on  the  dry  corium).1  The  tanning 
can  now  be  carried  out  by  the  following  methods  : 

(a)  Infusion  tanning.     This  process,  which  is  used  for  lighter  hides,  consists  in  passing 
the  hides  into  tanning  baths  of  gradually  increasing  strength,  so  that  the  tanning  may  be 
gradual  and  penetrative.     The  total  time  required  is  6  to  9  weeks,  and  between  each  bath 
and  the  succeeding  one  the  hides  are  drained,  pressed,  and  fulled  in  order  to  facilitate 
the  absorption  of  the  tannin. 

(b)  Tanning  in  layers  was  once  largely  used  but  is  now  employed  more  particularly 
for  sole  leather.     Fifty  or  sixty  hides  are  placed,  alternately  with  layers  of  powdered  or 
crushed  tanning  material  (bark,  wood,  &c.),  in  a  cement  or  wooden  vessel,  the  empty 
spaces  being  then  filled  with  the  tanning  material  and  the  whole  covered  with  water. 
The  vessel  is  then  closed  with  an  air-tight  cover  and  left  for  about  2  months,  the  hides  being 
then  transferred  to  a  second  similar  vessel  containing  rather  less  tanning  material,  where 
they  are  left  for  3  to  .4  months,  and  finally  to  a  third  vessel  containing  still  less  tanning 
material  (4  to  5  months). 

1  F.  Carini  (Ann.  d.  Soc.  chim.  di  Milano,  1903,  p.  23,  and  1904,  p.  144)  proposes  to  use  the  hydrostatic  balance 
in  order  to  obtain  the  weight  of  the  dry  hide  from  that  of  the  wet  hide,  without  drying.  The  hides  can  thus  be 
followed  through  all  the  operations,  from  their  entry  in  a  more  or  less  moist  state.  The  quantity  of  tanning 
material  fixed  can  also  be  determined  at  any  moment  in  this  way. 


590 


ORGANIC    CHEMISTRY 


FIG.  414. 


If  the  hides  are  very  heavy  and  resistant,  they  are  passed  to  a  fourth  and  sometimes 
to  a  fifth  bath  or  pit,  the  whole  operation  then  occupying  about  two  years  and  the  consump- 
tion of  bark  being  about  five  times  the  weight  of  the  dry  hides.  The  completion  of  the 
tanning  is  ascertained  by  cutting  the  hide  and  observing  that  the  section  is  uniform  and 

without  horny  or  fleshy  layers,  and 
that  the  grain  does  not  crack  when 
the  hide  is  carefully  bent. 

(c)  Rapid  tanning,  which  gives 
a  greater  output  of  leather,  has 
been  attempted  in  many  different 
ways :  By  immersing  and  com- 
pressing the  hides  in  relatively 
concentrated  tanning  baths  pre- 
pared from  active,  modern  ex- 
tracts, and  containing  a  certain 
amount  of  acid  to  prevent 
wrinkling  of  the  hides,  the  tan- 
ning liquor  being  circulated  by 
means  of  pumps  without  moving 
the  hides  ;  or  the  skins  are  placed 

in  revolving  barrels  or  drums,  the  lower  half  dipping  into  tanning  liquor  so  that  the  hides 
are  pressed  at  intervals.  The  diffusion  process  is  also  applied  by  placing  the  tanning  bath 
in  bags  composed  of  various  hides  sewn  together.  Tanning  in  a  vacuum  has  likewise 
been  used  in  order  to  effect  better  penetration  of  the  tanning  material,  considerable 
pressure  being  exerted  automatically  on  the  hides  at  regular  intervals,  and  the  operation 
being  facilitated  by  gentle  heat,  &c.  By  these  rapid  processes  (see  also  Use  of  Quinone, 
Ger.  Pat.  206957,  1907)  tanning  can  be  completed  in  6  to  8  weeks,  this  including  the 
preliminary  preparation  of  the  hides.  The  actual  tanning  may,  indeed,  be  limited  to 
30  hours  if  revolving  barrels  are  used  with  hot,  highly  concentrated  tanning  baths  (8°  to 
10°  Be).  When  such  a  rapid  process  is  used  it  is,  however,  indispensable  to  eliminate  all 
traces  of  lime  beforehand  by  immersion  in  formic  acid  solution.  Other  very  rapid  methods 
which  are  largely  used  are  chrome  tanning  (see  above)  and  formaldehyde  tanning  as 
proposed  by  Payne. 

The  tanned  hides  are  then  subjected  to  finishing,  which  varies  considerably  with  the 
nature  of  the  hide  and  the  kind  of  leather  required. 

For  sole  leather,  the  hides  from  the  layers  are  first  dried  in  the  shade  and  are  then 
beaten  or  hammered  by  means 
of  a  suitable  machine  (Fig.  414)  ; 
in  this  way  the  leather  is  rendered 
more  compact,  so  that  the  wear 
of  the  sole  is  diminished.  To 
make  the  leather  of  uniform 
thickness  and  to  eliminate  lumps, 
scurf,  wrinkles,  &c.,  the  hide  is 
scraped  or  shaved  on  the  under 
side  (i.e.  not  the  hair  side)  with  a 
sharp  curved  knife  or,  better,  with  WIG  415 

a  machine  carrying  steel  blades 

on  a  moving  band,  which  can  be  brought  more  or  less  near  to  the  skin,  the  latter  being 
stretched  on  a  movable  trolley  (Fig.  415)  so  as  to  facilitate  this  tedious  and  troublesome 
operation.  Regular  graining  is  attained  by  stretching  the  hide  on  a  bench,  one  side  being 
fixed  to  the  edge  of  the  bench  and  the  hide  then  bent  over  on  itself,  while  a  block  of 
wood  having  a  concave  base  with  pointed  grooves  (Fig.  416)  is  moved  backwards  and 
forwards  over  the  fold,  which  is  gradually  displaced  until  the  whole  surface  of  the  hide 
is  covered. 

Artificial  grain  is  nowadays  imparted  by  pressing  the  hides  between  special  fluted 
cylinders. 

Those  hides  which  are  required  to  show,  not  graining,  but  a  smooth  surface  are  first 
rendered  perfectly  uniform  at  the  surface  by  rubbing  both  sides  with  pumice  by  hand  or 


HYDROGENATED  BENZENE  COMPOUNDS  591 


Fio.  416. 


more  conveniently  by  a  kind  of  spindle-shaped  grindstone  covered  with  emery  (Fig.  417), 
against  which  the  surface  of  the  hide  is  gently  pressed.  In  some  cases  this  operation 
is  completed  by  polishing  the  bloom  side  with  a  concave  piece  of  wood,  similar  to  that  of 
Fig.  41 6,  but  with  a  smooth  surface  lined  with  cork. 

The  polishing  is  finished  on  the  bloom  side  with  a  heavy,  very  smooth  roller,  moved 
horizontally  by  a  rod  connected  with  an  eccentric.  All  these  finishing  operations  are 
carried  out  mechanically  by  machines  which  are  continually  being  improved  and  which 
cannot  be  described  here. 

Finally,  many  leathers  with  which  a  certain  degree  of  softness  is  required,  are  greased 
with  fish  oil  or  a  mixture  of  this  with  tallow  or  other  fats  (wool  fat)  or  degras  (see  p.  389). 
In  this  operation,  which  amounts  to  a  second  tanning  (chamoising,  see  above),  the  tanned 
and  still  moist  hides  are  well  smeared  with  the  fat  and  exposed  to  the  air  until  the  whole 
of  it  is  absorbed. 

Leather  for  boot  uppers  is  coloured  black  on  the  flesh  side  by  rubbing  with  concentrated 
solutions  of  iron  acetate  and  sulphate,  treating  with  oil, 
wax,   soap,    lampblack,   &c.,   and    then   polishing  with 
smooth  wood  until  a  shining  surface  is  obtained. 

For  special  purposes  hides  and  leathers  are  coloured 
with  basic  or  mordant  aniline  colours,  the  hides  being 
first  prepared  by  immersion  for  12  hours  in  cold  water 
in  which  is  dissolved  the  white  of  an  egg  for  each  hide. 
The  dyeing  is  carried  out  at  a  temperature  of  30°. 
Certain  leathers  are  varnished  with  ordinary  resin  var- 
nishes. In  order  to  supply  the  great  demand  for  large 
hides  for  the  hoods,  &c.,  of  carriages,  ox-hides  and  cow- 
hides are  nowadays  divided,  the  more  resistant  part  being 
kept  for  the  hoods,  and  the  flesh  side  for  the  seats,  &c. 

The  use  of  pure  water  is  indispensable  in  all  tanning 
operations,  since  water  which  is  too  hard  and  rich  in  lime 
readily  produces  white  efflorescence  on  the  hides.  The 
presence  of  iron  in  the  water  results  in  the  formation 

of  dark  patches,  while  suspended  organic  matter  is  always  harmful ;  waters  containing 
these  substances  must  hence  be  thoroughly  purified  before  use  (see  vol.  i,  pp.  218  and  665). 
In  order  to  avoid  the  formation  of  the  white  efflorescence — due  to  the  combination  of  lime 
with  the  fatty  matters  of  the  tanning  materials — it  has  been  proposed  to  replace  the  fats  by 
mineral  oils,  which  do  not  give  calcium  salts,  or  to  wash  the  hides  well  with  dilute  lactic  or 
formic  acid  which  form  soluble  calcium  salts.  The  suggestion  has  also  been  made  that 
the  hides  be  dressed,  not  with  fats,  but  with  the  anhydrides  or  lactones  of  fatty  acids,  as 
these  form  calcium  salts  more  slowly  (the  purgatol  recently  placed  on  the  market  consists 
mainly  of  anhydrides  or  lactones). 

England's  exports  and  imports  of  hides  are  as  follow : 


FIG.  417. 


Raw  hides 


Tanned  hides,  leather 


1910 
1911 
1910 
1911 


Imports 

£12,882,326 

11,104,326 

11,824,741 

12,227,606 


Exports 

£1,757,762 

1,685,583 

4,686,485 
4,880,932 


O.  HYDROGENATED  BENZENE  COMPOUNDS 

Considerable  interest  attaches  to  the  numerous  hydrophthalic  acids  studied 
by  Baeyer  in  their  various  constitutional  and  stereo -isomerides  (cis-  and  trans- 
isomerides  ;  see  p.  21). 

They  behave  largely  like  unsaturated  aliphatic  compounds  (see  p.  520),  as 
they  no  longer  possess  the  stability  of  the  true  benzene  nucleus.  The  position 
of  the  true  double  linkings  in  these  compounds  is  determined  by  the  addition 
of  bromine  or  by  subsequent  elimination  of  the  latter  by  reduction,  with  or 
without  substitution  of  hydrogen,  according  as  the  two  bromine  atoms  are  in 
para-  or  ortho-positions.  Simple  boiling  with  alkali  often  effects  displacement 


592  ORGANIC    CHEMISTRY 

of  a  double  bond  (as  with  oleic  acid  ;  seep.  293),  so  that  it  is  possible  to  pass 
from  one  isomeride  to  another. 

The  di-,  tetra-,  and  hexa-hydrophthalic  and  terephthalic  acids  can  be 
dehydrogenated  in  stages  by  heating  with  bromine  at  200°  ;  many  of  them 
form  anhydrides. 

From  the  results  of  his  investigations  on  the  hydrophthalic  acids  Baeyer 
drew  important  conclusions  concerning  the  constitution  of  the  benzene  nucleus. 

Many  important  hydrogenated  benzene  derivatives  occur  naturally,  among 
them  the  naphthenes,  found  in  abundance  in  Russian  petroleum  (see  p.  63), 
which  contain  hexamethylene  groupings  (see  Polymethylenes,  p.  520).  Syn- 
thetically they  may  be  obtained,  for  example,  from  calcium  pimelate  : 

222  2 


>CO  (ketohexamethylene)  . 

Also,  by  condensing  2  mols.  of  ethyl  succinate  with  sodium  and  then 
hydrolysing  the  product  and  heating  at  200°,  p-diketohexamethylene  is  obtained. 
Hydrogenation  of  benzene  and  its  homologues,  by  passing  their  vapours, 
mixed  with  hydrogen,  over  heated  finely  divided  nickel,  yields  hexamethylene  l 
and  its  homologues,  hexahydrophenol  (b.pt.  160-5°),  and  p-diketohexamethylene 
(m.pt.  78°).  The  latter  gives  the  corresponding  alcohol,  quinitol  (p-dihydroxy- 
hexamethylene),  which  forms  various  cis-  and  trans  -isomerides.  Inositol, 
C6H1206,  the  hexahydric  alcohol  derived  from  hexamethylene,  is  isomeric 
with  the  hexoses,  but  with  HI  or  PC15  yields  true  benzene  derivatives. 

Various  naphthenic  acids  are  obtained  by  oxidation  of  the  naphthenes  of 
petroleum  (see  p.  63),  and  are  distinguished  from  open-chain  acids  by  forming 
soluble  magnesium  and  calcium  salts  ;  by  this  means  they  can  be  detected 
when  used  in  the  manufacture  of  soaps. 

Still  more  interesting  are  the  terpenes  and  the  camphors,  which  are  found 
in  various  plants  and  form  the  principal  constituents  of  many  ethereal  oils  and 
essences  and  of  many  resins^ 

QUINIC  ACID  (TetrahydroxyhexahydrobenzoicAcid),  CO2H-C6H7(OH)4, 
is  optically  active,  but  only  an  inactive  modification  is  known.  It  is  obtained 
from  the  roots  of  coffee,  cinchona,  &c.,  and  forms  white  crystals. 


TERPENES 

These  are  regarded  chemically  as  hydrogenated  derivatives  of  cymene 
(dihydrocymene)  and  its  homologues,  and  have  the  generic  formula  Ci0H16. 
They  are  not  soluble  in  water,  but  can  be  readily  isolated  from  the  natural 
products  owing  to  their  volatility  in  steam. 

The  chemical  constitutions  of  the  principal  terpenes  have  been  established 
mainly  by  O.  Wallach's  investigations  over  a  period  of  more  than  twenty  years. 
By  their  syntheses,  their  halogenated  additive  compounds,  their  behaviour 
towards  oxidising  agents  and  their  molecular  refraction  (see  p.  26),  it  has 
been  shown  that  they  contain  two  double  linkings  and  a  closed  ring  of  six 
carbon  atoms. 

There  is,  however,  a  group  of  more  complex  terpenes  (pinene,  camphene, 
fenchene,  &c.)  which  have  only  one  double  bond.  In  order  to  define  the  position 
of  the  double  linkages  (A),  Baeyer  numbered  the  fundamental  carbon  atoms 
of  the  cymene  as  in  the  first  figure  of  the  following  scheme,  which  shows  the 

1  HEXAMETHYLENE  (hexahydrobenzene,  cydohexane,  or  naphthene)  is  found  in  Caucasian  petroleums 
and  is  obtained  synthetically  from  iodohexamethylene  or  1  :  3-dibromopropane.  It  is  a  colourless  liquid  smelling 
like  petroleum,  and  it  boils  at  80°  and  resists  the  action  of  permanganate.  By  hydriodie  acid  at  high  temperatures 
it  is  converted  into  methylpentamethylene. 


constitution  of  five  terpadienes  out  of  fourteen  possible  theoretically  without 
counting  enantiomorphs. 


5    8| 

v/ 


c_ c— c 

10      8        9 


H2 
H 


CH, 


H 


C3H7 
I 


H 


H 

x/t 

A 

H  C3H7 
II 


HCH3 

V 
HAa 


H 


C3H7 
III 


FIG.  418. 


H2 
Ho 


CH, 


H/\H 


H. 


,  H2 

f~H 
CH3-C-CH3      CH3-C=CH2 

IV  V 


10H16(N02)(NO),  or  Nitrosochlorides,   C10H16(NO)C1,   which  are 


To  indicate  the  position  of  the  double  linking  in  the  side-chain,  instead  of 
giving  only  the  lower  number  of  the  two  carbon  atoms  united  to  the  double 
linking,  as  in  the  case  of  the  nucleus  (e.g.  Ill  =  A3>5-terpadiene  or 
limonene ;  I  =  A1>4-terpadiene),  the  numbers  of  both  the  carbon  atoms 
united  to  the  double  linking  are  given,  the  higher  number  being  bracketed 
(e.g.  IV  =  AWUerpadiene  ;  V  =  A^O-terpadiene).  In  the  official 
nomenclature  the  name  terpane  is  given  to  Hexahydrocymene,  C10H20, 
Tetrahydrocymene,  C10H18,  being  called  terpene  and  the  Dihydrocymenes, 
G10H16,  terpadienes. 

As  separated  from  plants  or  fruits,  the  terpenes  are  generally  mixtures, 
and  when  obtained  from  conifers  are  termed  oil  of  turpentine.  Essence  of 
lemon  gives  citrene  ;  thyme,  thymene  ;  cumin,  carvene  ;  orange,  hesperidine, 
&c.  Although  their  boiling-points  differ  little  (160°  to  180°),  they  form  tetra- 
bromo-derivatives  and  dihydrochlorides  with  widely  different  melting-points, 
these  compounds  hence  serving  for  their  separation. 

Properties.  Owing  to  the  presence  of  double  linkings,  which  act  as  in 
aliphatic  compounds,  the  terpenes  can  combine  with  four  bromine  atoms  or  two 
mols.  of  HC1  (the  halogen  being  readily  replaced  by  hydroxyl,  with  formation 
of  camphor)  and  also  react  with  nitrous  acid  or  nitrosyl  chloride,  forming  solid 
Nitrosites,  C 
also  solid  and  sometimes  blue. 

They  oxidise  easily  and  with  mild  oxidising  agents  give  benzene  derivatives, 
whilst  on  energetic  oxidation  they  resinify  ;  they  polymerise  readily,  and 
by  acids,  for  instance,  are  converted  into  more  stable  isomerides.  In  alcoholic 
solution  they  give  characteristic  colorations  with  concentrated  sulphuric  acid. 
They  are  usually  optically  active. 

They  often  accompany  the  natural  perfumes  of  fruits  and  flowers,  which, 
now  that  they  have  been  subjected  to  thorough  chemical  study,  can  be  obtained 
purer  and  of  increased  value.1 

1  PERFUME  INDUSTRY.  A  considerable  number  of  the  natural  perfumes  have  been  prepared  from  the 
very  earliest  times,  but  with  the  perfected  methods  of  extraction  now  available  they  are  obtained  in  higher  yields 
and  in  a  more  highly  refined  condition.  The  most  abundant  supplies  of  raw  material  have  always  been,  and  are 
still,  obtained  from  eastern  countries,  where  whole  provinces  are  often  devoted  to  the  cultivation  of  flowers. 

The  most  delicate  perfumes  are  those  obtained  from  flowers  which  contain,  along  with  the  odorous  principle, 
other  substances  which  refine  the  aroma  and  render  it  softer.  The  name  artificial  perfumes  was  at  one  time 
given  to  mixtures,  in  proportions  carefully  chosen,  of  the  fundamental  natural  essences,  a  great  variety  of  perfumes 
being  thus  obtained  ;  this,  however,  required  a  very  highly  developed  sense  of  smell  in  the  operator. 

The  discovery  of  artificial  perfumes  did  not  diminisli  the  consumption  of  the  natural  products  since  these 
became  cheaper  and  thus  appealed  to  a  large  public. 

The  consumption  of  perfumes  fluctuates  with  the  fortunes  of  a  nation.  The  early  Eastern  races  and  then  the 
ancient  Egyptians  introduced  perfumes  into  religious  ceremonies,  their  secular  use  being  often  forbidden.  Gradually, 
however,  they  became  used  for  domestic  purposes,  together  with  many  diifercnt  pomades  and,  in  some  cases,  dyes. 
Egyptian  pomades  were  held  in  high  esteem  by  Cleopatra.  With  the  ancient  Greeks,  the  use  of  perfumes  and 
cosmetics  assumed  considerable  importance  and  often  degenerated  into  abuse,  and  Socrates  states  that  if  even  a 
slave  is  anointed  with  a  good  perfume  he  will  exhale  the  same  odour  as  his  master. 

Perfumery  flourished  under  the  Romans  and  declined  with  the  Empire,  being  re-established  in  Italy  only  a 
II  38 


594 


ORGANIC    CHEMISTRY 


CINENE  (AJ»8(9)-Terpadiene  or  Dipentene ;  Inactive  Limonene),  C10H16,  is  found 
together  with  cineol  in  oleum  cince  and  also  in  Laurus  camphora  and  in  Russian  and  Swedish 
turpentine  oils.  It  is  formed  by  isomeric  change  when  camphene,  active  limonene,  pinene, 
&c.,  are  subjected  to  protracted  heating  at  260°  to  270°,  and  is  obtained,  together  with 
isoprene,  when  rubber  is  distilled,  2  mols  of  the  isoprene,  CH2  :  CH-C(CH3) :  CH2,  under- 
going condensation. 

It  has  a  pleasant  odour  of  lemons,  and  boils  at  176°.     Nitrosodipentene  (inactive 

the  time  of  the  Renaissance.  It  then  passed  into  France,  where  it  became  a  true  national  industry,  culminating 
at  the  time  of  the  perfumed  Court  of  Louis  XV. 

Until  about  the  middle  of  last  century,  France  enjoyed  almost  a  monopoly  in  this  industry,  but  when  science 
pervaded  this  branch  of  human  activity,  the  clever  French  rule-of-thumb  manufacturers  did  not  grasp  quickly 
enough  the  benefit  to  be  derived  from  a  rational  development  of  their  industry,  of  which  England  and  Russia,  and 
more  especially,  during  the  past  quarter  of  a  century,  Germany  have  taken  advantage.  At  Grasse  and  Cannes, 
in  the  south  of  France,  however,  the  natural  perfume  industry  is  still  of  importance,  certain  factories  dealing 
with  as  much  as  3000  kilos  of  violets  (40  to  50  millions  of  flowers)  at  a  time. 

As  has  been  already  mentioned,  the  prime  materials  come  mainly  from  Eastern  Europe,  and  at  the  present 
time  also  from  the  Far  East.  But  the  cultivation  of  plants  for  perfumes  is  still  largely  carried  on  in  the  South  of 
France  and  in  Sicily. 

In  annuals  the  essential  oil  is  formed  in  the  green  organs,  and  the  majority  of  it  is  found  ill  the  flowers  before 
ertilisation.  The  extraction  of  perfumes  from  Dowers  and  leaves  is  carried  out  in  various  ways  :  (1)  By  distillation 
with  direct  or  indirect  steam  or  in  vacua,  the  distillates  of  different  densities  being  separated  ;  this  method  is  used  for 
lavender,  rosemary,  thyme,  orange  blossom,  and  roses,  •which  are  unaltered  at  steam  heat.  (2)  By  infusion  for  12  to 
48  hours  at  60°  to  65°  with  pure  fats  (olive  oil,  &c.),  the  flowers  being  renewed  four  to  six  times  until  the  fat  is 
highly  perfumed  ;  the  extracted  flowers  are  pressed  to  free  them  from  fat,  and  the  perfumed  fat  run  into  enamelled 
iron  vessels  as  a  concentrated  pomade  ;  in  this  way  are  treated  cassia,  violets,  jonquils,  and  sometimes  orange 
blossom  and  roses,  when  mixed  with  other  flowers.  (3)  By  absorption  in  the  cold  of  the  more  delicate  perfumes  of 
jessamine,  heliotrope,  and  tuberoses  ;  in  vessels  with  glass  walls  smeared  with  fat  or  covered  with  cloth  soaked  in 
oil,  the  petals  are  pressed  and  rubbed,  being  renewed  every  day ;  after  some  days  or  at  the  end  of  the  season 
the  perfumed  fats  are  shaken  for  a  long  time  with  alcohol,  which  extracts  all  the  perfume.  To  obtain  colourless 
products,  Piver  passes  a  slow  current  of  air  through  the  flowers  and  then  on  to  the  fatty  surface.  (4)  By  dissolution. 
The  use  of  this  method  is  spreading,  as  it  gives  highly  concentrated,  very  delicate  perfumes.  The  flowers  are 
immersed  in  petroleum  ether,  carbon  disulphide,  &c.,  the  perfume  being  extracted  by  a  current  of  steam  from 
the  solvent,  which  is  afterwards  recovered.  (5)  By  pressure  with  hand  or  hydraulic  presses,  this  method  being 
employed  with  orange-peel,  bergamot,  iris  rhizomes,  &c.  The  yields  obtained  per  1000  kilos  of  leaves  or  flowers 
are  about  as  follow  :  1  kilo  of  orange  oil  or  neroli,  from  the  flowers  (value  £24  to  £28),  or  3  kilos  of  petit  grain 
(from  the  leaves) ;  1  kilo  of  essence  of  basil  (£6  to  £8  per  kilo) ;  1200  grms.  of  essence  of  citronella  (88s.  per  kilo) ; 
9  to  15  kilos  of  eucalyptus  oil  (from  the  leaves) ;  120  grms.  of  essence  of  jessamine  (from  fresh  flowers) ;  1  kilo  of 
geranium  oil  (from  flowers  and  leaves) ;  10  kilos  of  oil  of  lavender  ;  6  kilos  of  marjoram  oil  ;  2  kilos  of  mint  oil; 
3  kilos  of  myrtle  oil ;  2  to  10  kilos  of  rosemary  oil ;  and  200  to  500  grms.  of  rose  oil. 

The  exports  from  Sicily  and  Calabria  and  the  imports  to  Italy  of  essences  were  as  follow  : 


Exports  from  Sicily  and  Calabria 

1906 

1907 

1908 

1909 

1910 

Orange  oil          .         .          kilos 

136,739 

162,274 

173,265 

242,762 

143,825  (£97,800) 

Bergamot  oil      .          .              ,, 

63,510 

87,538 

74,842 

73,803 

64,788  (£82,930) 

Lemon  oil          .         .             ,, 

440,500 

-  469,385 

476,842 

364,647 

425,076  (£154,025) 

Various  (mint,  mandarin,  &c.) 

oils        .         .         .          kilos 

— 

— 

28,500 

31,800 

13,500  (£14,800) 

Imports  into  Italy 

Clovu  oil  .          .          .           kilos 

2,446 

2,165 

1,538 

1,969 

1,878  (£1,502) 

Mint  oil    .          .          .              „ 

6,628 

6,484 

4,391 

5,334 

8,931  (£14,290) 

Rose  oil    ...             ,, 

493 

341 

101 

158 

109  (£3,920) 

Various  oils        .        '.              ,, 

67,797 

77,510 

81,830 

90,661 

99,228  (£79,380) 

As  much  as  100  quintals  of  flowers  for  perfumes  (at  28s.  per  quintal)  are  dispatched  per  day  from  San  Remo 
ii  the  spring  and  summer. 

In  the  neighbourhood  of  Giasse,  Cannes,  and  Nice  the  production  in  1902  was  2,500,000  kilos  of  orange  blossom, 
3,000,000  kilos  of  rose  leaves,  200,000  kilos  of  jessamine,  150,000  kilos  of  violets,  150,000  kilos  of  tuberoses,  &c.,  all 
these  being  extracted  on  the  spot. 

In  Germany,  although  the  climate  does  not  seem  very  favourable,  the  cultivation  of  certain  flowers  for  perfumes 
is  largely  carried  on  in  some  districts.  The  perfumery  factories  have  hundreds  of  hectares  of  land  under  flowers 
not  only  for  commercial  purposes,  but  also  for  analytical  and  research  work.  One  hectare  yields  10,000  to  15,000 
kilos  of  rose  leaves.  At  one  time  the  firm  of  Schiiumel  (Leipzig)  treated  as  much  as  600,000  kilos  of  fresh  rose  leaves 
per  day,  300  kilos  of  rose  oil  being  extracted ;  this  was  repeated  two  or  three  times  in  a  month  (June).  A  kilo 
of  the  oil  is  sometimes  obtained  from  2000  kilos  of  the  leaves. 

Rose  cultivation  is,  however,  carried  on  most  extensively  in  Turkey  and  Bulgaria,  where  preference  is  given  to 
the  red  rose  (Rosa  damasccena),  which  gives  on  an  average  1  kilo  of  oil  per  4000  kilos  of  leaves,  although  white  roses 
(Rosa  alba),  giving  1  kilo  of  oil  per  5000  kilos  of  fresh  petals,  are  also  largely  grown.  The  product  from  the  latter 
variety  is  less  fine,  but  it  gives  an  oil  crystallising  at  18°  to  20°  and  is  used  to  mask  oils  of  lower  quality  ;  the 
market  value  of  the  oil  is  judged  more  particularly  from  the  freezing-point,  which  should  be  between  17°  and  19° 
for  good  qualities.  Adulteration  with  alcohol  or  spermaceti  is  easily  discovered,  but  it  is  more  difficult  to  detect 
additions  of  geranium  oil  or  palmarosa  oil. 

In  1887  Turkey  produced  2400  kilos  of  pure  rose  oil  (attar  of  roses),  whilst  in  1904  and  1906  the  output  reached 
3600  kilos.  The  annual  production  varies  very  considerably,  as  the  plants  suffer  greatly  in  dry  seasons,  especially 
water  IB  scarce  in  the  month  of  May  preceding  the  harvest;  in  1907  indeed,  the  output  was  only  2000  kilos. 


PERFUMES  595 

carvoxime)  melts  at  93°.  With  HC1,  cinene  gives  two  stereoisorneiic  dipentcne  dihydro- 
chlorides  (1  :  4-dichloroterpanes),  melting  at  50°  and  25°.  The  tetrabromide  melts  at  125°. 
CARVENE  (rf-Limonene,  Hesperidine,  Citrene),  Ci0H16,  forms  the  greater  part  of 
orange-peel  oil  and  also  occurs  abundantly  in  cumin  oil,  anethum  oil,  &c.  ;  lemon  oil  is  a 
mixture  of  pinene  and  limonene.  It  is  a  liquid  boiling  at  175°  and  is  optically  active 
although  readily  convertible  into  inactive  dipentene.  It  forms  a  dextro-rotatory 
tetrabromide  melting  at  104°. 

In  Bulgaria  roses  are  still  more  largely  grown,  and  here,  too,  the  production  varies  widely.  The  exports  of  pure 
oil  were  as  follows  :  3190  kilos  (£71,280)  in  1897  ;  3900  kilos  in  1902  ;  6200  in  1903 ;  5000  in  1904  ;  less  than 
4500  in  1905.  In  1907  the  exports  were  valued  at  £168,000,  aud  in  1908  at  £184,000 ;  in  1909  6053  kilos  were 
exported.  At  one  time  two-thirds  of  the  oil  went  to  France,  but  now  only  one-third  goes  to  the  French  factories 
the  rest  being  sent  to  England  and  Germany. 

In  1910  England  imported  natural  ethereal  oils  to  the  value  of  £320,218,  artificial  ethereal  oils  to  the  value  of 
£34,369,  and  alcoholic  perfumes  to  the  value  of  £90,176.  The  United  States  imported  perfumes  and  other  toilet 
preparations  to  the  value  of  £303,600  in  1911. 

The  price  of  attar  of  roses  varies  from  £32  to  £80  per  kilo,  and  was  formerly  higher  than  this. 

In  1904  H.  von  Soden  patented  a  process  for  obtaining  more  refined  and  delicate  perfumes  from  flowers.  He 
first  obtained  a  petroleum  ether  extract  which  was  then  evaporated  and  the  residue  taken  up  in  alcohol,  the  latter 
being  distilled  off  and  the  residue  distilled  in  steam.  It  must,  however,  be  pointed  out  that  with  this  process,  1  kilo 
of  the  finest  rose  oil  would  now  cost  £1520  and  1  kilo  of  oil  of  violets  almost  £4000. 

From  what  has  been  already  stated,  it  will  be  recognised  that  considerable  interest  attaches  to  the  study 
of  the  composition  and  constitution  of  these  essences  and  to  their  artificial  production  by  synthetical  methods. 
In  former  times,  various  artificial  perfumes  have  been  obtained  empirically,  as  was  also  the  case  with  the  first  coal- 
tar  dye,  yet  it  has  required  systematic  chemical  investigation  to  open  up  new  fields  in  this  direction.  During  the 
last  thirty  years,  the  consumption  of  perfumes  has  increased  from  £480,000  to  £2,400,000,  owing  to  the  diminished 
prices  of  the  natural  and  artificial  products. 

The  first  artificial  perfume  was  nitrobenzene  or  artificial  myrbane  oil,  which  was  discovered  by  Mitscherlich  in 
1834,  placed  on  the  market  by  Colles  and  manufactured  on  a  large  scale  by  nitrating  benzene  from  tar  by  Mansfield 
in  1847.  In  about  1840,  Piria  oxidised  salicin  (a  glucoside  found  in  willow  bark)  and  thus  obtained  salicyl- 
aldehyde,  which  is  the  pleasant  smelling  essence  of  Spircea  ulmaria  (meadow-sweet).  A  few  years  later — in  1844 — 
Cahours  succeeded  in  isolating  the  active  principle  of  gaultheria  or  wintergreen  oil,  consisting  of  methyl  salicylate, 
which  can  be  obtained  synthetically  by  heating  salicylic  acid  with  methyl  alcohol  (wood  spirit)  and  sulphuric  acid. 
Many  of  the  natural  perfumes  contain  aldehydes,  and  in  1853  Bertagnini  showed  how  they  could  be  separated  pure 
by  first  combining  them  with  bisulphite.  Benzaldehyde  was  synthesised  by  Cahours  in  1868,  and  coumarin,  the 
essence  of  Asperula  odorata,  by  Perkiu  in  1875.  In  1876  Haarmaun  and  Tiemann  ascertained  the  constitution  of 
vanillin,  later  preparing  it  from  coniferiu  or,  better  still,  from  eugenol  extracted  from  clove  oil.  In  1888  Baur 
prepared  artificial  musk. 

In  1893  Tiemann  and  Kriigcr  succeeded  in  effecting  the  synthesis  of  violet  oil,  previously  obtained  at  enormous 
expense  from  the  natural  flowers  and  costing  more  than  £600  per  kilo.  They  also  separated  irone,  the  odorous 
principle  of  iris  root,  and  determined  its  chemical  constitution.  Immediately  afterwards  they  prepared  synthetically 
an  isomeride  of  irone,  ionone  (see  later)  to  which  the  delicate  odour  of  the  violet  is  due.  These  investigators  heated 
citral,  which  occurs  in  abundance  in  lemons,  with  acetone,  acetic  anhydride,  acetic  acid,  and  sodium  acetate, 
obtaining  first  pseudo-ionone,  which  has  an  unpleasant  smell,  and,  when  treated  with  mineral  acid,  yields  ionone. 
These  processes  were  patented  by  Tiemann  and  disposed  of  by  him  to  the  most  important  perfume  manufacturers 
for  £40,000. 

The  study  of  the  chemical  constitution  of  the  components  of  perfumes  reveals  a  certain  relation  between  the 
aroma  and  the  presence  of  definite  atomic  groupings  (osmophores)  and  attempts  were  made  to  establish  a  perfume 
theory  on  a  similar  basis  to  the  colour  theory  of  aniline  dyes,  the  characteristic  groups  of  which  are  termed  chromo-  • 
phores.  It  has  not  yet  been  found  possible  to  formulate  a  theory  as  rigorous  as  that  for  the  colouring-matters, 
and  all  that  has  been  fixed  is  that  aldehydes,  ketones,  mixed  ethers,  &c.,  often  enter  into  the  constitution  of 
perfumes,  and  that  the  introduction  of  certain  alcoholic  residues  into  the  molecules  may  intensify  or  modify  the 
aroma. 

The  action  of  perfumes  on  the  olfactory  nerves  is  not  thoroughly  understood,  although  it  is  regarded  by  some 
as  due  to  vibrations  of  the  ether  similar  to  those  by  which  light  and  heat  are  transmitted,  these  vibrations  originating 
•  from  the  oxidation  of  the  substance  in  the  air.  This  hypothesis  seems  to  be  supported  by  the  fact  that  many 
odorous  substances  emit  no  smell  when  worked  and  distilled  in  an  inert  gas  instead  of  in  air.  It  is  now,  however, 
generally  assumed  that  the  smell  is  propagated  by  small  particles  or  molecules,  which  become  detached  and,  in 
the  state  of  gas,  come  into  contact  with  and  excite  the  papillae  of  the  nasal  mucous  membrane.  The  fact  that  certain 
substances  have  little  smell  in  the  pure  or  concentrated  state  and  acquire  their-maximum  smell  only  when  con- 
siderably diluted,  is  well  explained  by  modern  views  on  solutions,  dissociation  in  dilute  solutions  giving  rise  to  the 
corresponding  ions,  which  become  detached  and  excite  the  olfactory  sense.  That  minimal  traces  of  these  substances 
transmit  perfume  is  shown  by  the  retention  of  this  property  by  garments  which  have  been  washed  five  or  six  times 
see  Experiment  described  in  vol.  i,  p.  3).  A  series  of  tests,  controlled  by  the  olfactometer,  showed  that  most  men — - 
who  have  by  no  means  a  very  delicate  sense  of  smell  in  comparison  with  other  animals — perceived  the  odour  of 
1  part  of  prussic  acid  in  100,000  of  water,  7  per  cent,  of  the  individuals  examined  detecting  it  in  a  dilution  of 
1  in  2,000,000.  Of  the  women  tested,  however,  not  one  was  able  to  detect  prussic  acid  in  a  dilution  as  small  as 
1  in  20,000.  These  results  support  the  view  that  male  animals  are  very  sensitive  to  the  odour  of  the  females, 
which  serves  to  excite  their  sexual  passions.  Some  individuals,  termed  anosmic,  are  quite  without  sense  of 
smell. 

The  following  data  give  an  idea  of  the  influence  exercised  by  the  artificial  products  on  the  prices  of  perfumes  in 
general :  vanillin  cost  £120  per  kilo  in  1878,  £35  in  1890,  and  £3  in  1892,  while  for  heliotropine  the  price  was  £100 
per  kilo  in  1881,  £15  in  1890,  and  about  30*.  in  1902.  That  the  consumption  of  the  natural  products  has  not  been 
diminished  but  has  increased  is  shown  by  the  importation  of  vanilla  to  France,  which  amounted  to  29,000  kilos 
in  the  period  1857-1866,  and  to  137,000  kilos  in  1887-1896. 

For  the  year  1897  it  was  calculated  that  the  total  imports  into  and  exports  from  Germany  of  ethereal  oils  and 
perfumes  amounted  to  £920,000. 

The  Italian  imports  of  alcoholic  perfumes  in  1904  were  valued  at  £18,640  and  those  of  non-alcoholic  at  £18,560, 
while  the  exports  were  valued  at  £3440  and  £16,000  respectively. 

For  fruit  essences  see  p.  371. 


596 


ORGANIC    CHEMISTRY 


Z-LIMONENE,  C10H16,  the  constitution  of  which  is  shown  on  p.  593  (V),  can  be  obtained 
from  d-carvone,  and  occurs,  together  with  1-pinene,  in  pine  oil.  Its  tetrabromide  melts 
at  104°. 

SYLVESTRENE,  C10H16,  is  possibly  derived  from  m-cymene  and  forms  a  dextro- 
rotatory component  of  turpentine.  It  boils  at  176°  and  gives  an  intense  blue  coloration 
with  concentrated  sulphuric  acid  and  acetic  anhydride. 

TERPINOLENE  (A1>4(8)-Terpadiene),  C10H16,  has  the  constitution  shown  at  IV  on 
p.  593.  It  is  obtained  by  the  elimination  of  water  from  terpineol  and  melts  at  185°. 

TERPINENE,  Ci0H16,  boiling  at  179°  to  180°,  is  obtained  in  the  transformation  of 
various  terpenes.  Its  nitrosite  forms  monoclinic  crystals  melting  at  155°. 

DIHYDROCYMENE,  C10H16,  obtained  synthetically  from  ethyl  succinylsuccinate, 
boils  at  174°. 

PHELLANDRENE,  Ci0H16,  is  known  in  both  the  laevo-  and  dextro-rotatory  forms, 
these  having  the  same  chemical  and  physical  properties  (excepting  the  optical  rotation) 
and  boiling  at  172°.  The  former  (1-)  is  found  in  Australian  eucalyptus  oil  and  the  latter  in 
Anethum  foeniculum  and  in  water-fennel  oil  (Phellandrium  aquaticum). 

MENTHENE,  C10H18,  boils  at  167°.  MENTHANE  (Hexahydrocymene),  C10H20, 
boiling  at  170°,  does  not  occur  naturally,  but  is  obtained  by  hydrogenating  cymene  in 
presence  of  nickel. 

COMPLEX  TERPENES 

Like  the  preceding,  these  are  composed  of  a  monocyclic  system,  but  with 
two  rings  ;  they  have  only  one  double  linking,  and  hence  combine  with  two 
atoms  of  hydrogen  or  halogen. 

They  can  be  converted  readily  into  cymene  and  its  derivatives. 

The  following  four  diagrams  show  how  a  trimethylene  ring  or  bridge  is 
formed  in  Carane  (not  known  in  the  free  state, 'although  the  corresponding 
saturated,  synthetic  ketone,  Carone,  is  known),  a  tetramethylene  ring  in 
pinane  and  pinene,  and  a  pentamethylene  ring  in  camphane  : 

CH, 


CH, 


CH2 
CH,— C— CHS 

CH2 


CH, 


CH 

Camphane 

PINENE  (Terebenthene,  Laurene,  Menthene,  &c.),  QioHie  (constitution,  see  above), 
forms  one  of  the  principal  components  of  oil  of  turpentine,  occurs  also  in  sage  and  juniper 
oil,  and,  mixed  with  sylvestrene  and  dipentene,  forms  Russian  and  Swedish  turpentine  oil. 

When  incisions  are  made  at  suitable  seasons  in  certain  varieties  of  pine,  fir,  and  larch, 
a  kind  of  balsam  is  exuded  in  the  form  of  a  juice  which  gradually  changes  to  a  soft  resin, 
more  or  less  clear  according  to  the  quality.  This  is  known  as  ordinary  turpentine  or  American, 
French,  Venetian,  according  to  the  particular  tree  and  to  the  locality  of  origin.  When 
turpentine  is  distilled  with  steam,  the  liquid  essence  or  oil  of  turpentine  (turps)  is  collected 
separately,  the  residue,  which  is  solid  in  the  cold,  being  Colophony.1  The  direct  extraction 

1  COLOPHONY  (rosin)  is  hard  and  brittle,  its  sp.  gr.  being  1-050  to  1-085  at  15°  and  its  fracture  shining  and 
conchoidal.  According  to  the  quality,  its  colour  varies  from  yellow  to  Drown,  but  it  gives  a  whitish  powder.  At 
70°  it  becomes  soft  and  it  forms  a  kind  of  emulsion  with  hot  water.  It  always  melts  below  135°  and  it  is  readily 
soluble  in  alcohol  (1  in  10),  ether,  benzene,  petroleum  ether,  and  carbon  disulphide.  It  burns  with  a  smoky  Uame 
and,  when  subjected  to  dry  distillation  out  of  contact  with  the  air,  yields  resin  oil.  It  contains  abietic  acid,  Ci9H28O2, 
which  has  two  double  Unkings,  melts  at  165°,  and  is  soluble  in  hot  alcohol.  From  gallipot  rosin  (Pinus  maritima) 
pimaric  acid,  C20H30O2,  m.pt.  148°,  has  been  obtained. 

Colophony  has  the  rotatory  power  —69-6°,  and  the  acid  number  145  to  185. 

One  cubic  metre  of  flr  contains  about  10  kilos  of  turpentine,  which  yields  as  much  as  7  kilos  of  colophony, 


COLOPHONY  597 

of  the  turpentine  from  resinous  woods  by  means  of  suitable  solvents  (hot  wood-tar  mixed 
with  pine  oil ;  U.S.  Pat.  852,236)  has  been  suggested.  Oil  of  turpentine  is  rectified  by 
heating  with  steam  in  presence  of  0-5  per  cent,  of  quicklime.  As  the  oil  always  resinifies 
to  some  extent  when  exposed  to  the  air,  it  is  often  desirable  to  redistil  it  before  use.  The 
strong  and  less  agreeable  odour  of  Russian  and  Greek  turpentine  oils  is  removed  or  lessened 
by  shaking  with  a  solution  of  permanganate,  dichromate,  or  persulphate. 

Fresh  oil  of  turpentine  is  clear,  colourless,  and  highly  mobile  ;  it  has  the  sp.  gr.  0-855 
to  0-876  and  boils  at  156°  to  161°.  It  absorbs  and  combines  with  considerable  quantities 
of  ozone  and  oxygen — part  of  the  latter  being  converted  into  ozone  and  the  oil  at  the 
same  time  resinifying.  It  dissolves  sulphur,  phosphorus,  rubber,  and  resins,  and  is  hence 
used  for  varnishes,  lacs,  oil  paints,  &C.1 

Permanganate  in  acid  solution  transforms  it  partly  into  Pinonic  Acid,  C10H1603,  while 
with  dilute  nitric  acid  it  gives  Terephthalic  and  Terebinic  Acids,  C7H10O4.  It  reacts 
violently  with  iodine  in  the  hot,  forming  cymene.  The  relation  between  resins  and  aromatic 
compounds  is  established  by  the  fact  that  when  the  former  are  distilled  with  zinc  dust 
they  form  aromatic  hydrocarbons,  while  if  fused  with  potash  they  give  di-  and  tri-hydroxy- 
benzenes.  Resin  substitutes  or  artificial  resins  are  now  prepared  by  heating  phenols  with 
formaldehyde  in  presence  of  hydroxy-acids  (e.g.  tartaric  acid)  or  mineral  acids  (Blumer, 
Eng.  Pat.  12,880  of  1902,  and  Fr.  Pat.  361,539  of  1905  ;  also  Baekeland,  1909). 

According  to  the  preponderance  of  laevo-  or  dextro-pinene,  turpentine  oil  is  laevo-rotatory 
(Venetian,  German,  and  French)  or  dextro-rotatory  (Australian). 

Pinene  contains  only  one  double  linking,  and  hence  unites  with  only  1  mol.  of  HC1, 
giving  Pinene  Hydrochloride,  C10H17C1,  which  melts  at  125°,  and  has  the  smell  of  camphor 
( Artificial  Camphor).  When  treated  with  alcoholic  potash,  this  hydrochloride  is  converted 
into  CAMPHENE,  C10H16,  m.pt.  50°,  which  is  known  in  three  optical  modifications  and  IB 

while  1  cu.  metre  of  pine  gives  22  kilos  of  turpentine,  this  leaving  16-6  kilos  of  colophony ;  the  larch  gives  an 
intermediate  yield. 

Colophony  is  used  in  large  quantities  for  mixing  with  soaps  (see  Resin  Soaps,  p.  420),  for  sizing  paper,  for  making 
varnishes,  mastics,  &c.  In  the  United  States  35  per  cent,  of  the  total  output  is  used  in  soap-making. 

Large  quantities  of  it  are  incorporated  with  artificial  wax  (cerasin),  which  is  thus  cheapened  ;  to  deodorise 
the  resin,  it  is  finely  ground,  macerated  with  dilute  sulphuric  acid  for  five  or  six  days  and  then  suspended  in  hot 
water  and  subjected  to  a  jet  of  steam  for  some  time.  After  this  treatment  it  melts  and  mixes  well  with  the 
cerasin. 

Colophony  is  also  used  for  making  sealing-wax  by  mixing  with  shellac,  turpentine,  and  a  larger  or  smaller 
number  of  mineral  substances  (chalk,  burnt  gypsum,  magnesia,  zinc  oxide,  baryta,  kaolin,  &c.),  according  to  the 
quality  required ;  the  fused  mass  is  coloured  with  cinnabar  (for  the  finer  red  qualities),  minium,  ferric  oxide, 
or  red  ochre.  The  best  qualities  contain  only  40  per  cent,  of  mineral  matter  and  are  mainly  shellac,  while  the 
inferior  kinds  contain  as  much  as  70  per  cent,  of  mineral  matter,  the  residue  being  principally  colophony. 
Sealing-wax  is  coloured  black  by  lampblack  or  boneblack,  green  by  Prussian  blue,  yellow  by  chrome  yellow,  or 
blue  by  ultramarine ;  when  fused,  colophony  may  be  coloured  also  with  algol  or  indanthrene  dyes  (?.».). 

Italy  imported  18  quintals  of  sealing-wax  in  1898  and  61  in  1910,  the  corresponding  exports  amounting  to  21 
and  86  quintals  respectively. 

In  1905  Germany  imported  41,042  quintals  of  shellac  and  sealing-wax,  of  the  value  of  £779,800,  and  exported 
9575  quintals  (£196,280). 

In  1909  200,000  cases  of  sealing-wax  were  dispatched  from  Calcutta  to  England,  Germany,  and  the  United 
States. 

The  importation  of  colophony  into  Italy  amounted  in  1896-1899  to  an  average  of  122,700  quintals  ;  in  1905 
to  125,000  quintals  (£72,450) ;  and  in  1910  to  149,000  quintals  (£119,200),  mainly  from  North  America.  Its  price 
varies  from  12«.  to  28s.  per  quintal. 

In  1910  England  imported  75,000  tons  of.rosin  (colophony),  of  the  value  of  £880,582,  and  8700  tons  of  shellac  and 
sealing-wax,  of  the  value  of  £627,629.  The  United  States  exported  2,269,000  barrels  (£2,474,800)  of  rosin  in  1910 
and  2,415,000  barrels  (£3,241,600)  in  1911,  and  imported  12,000  tons  (£638,200)  of  sealing-wax  in  1910  and  8000 
tons  (£478,600)  in  1911. 

1  OIL  OF  TURPENTINE.  Most  common  are  the  French,  English,  Russian,  German,  and  American 
varieties,  40,000  tons  of  the  last-named  being  landed  at  Hamburg,  London,  and  Antwerp  in  1897.  In  1908  the 
outpiit  in  the  United  States  was  1,700,000  quintals  (£2,800,000),  one-half  of  this  being  produced  in  Florida. 

In  1902  Germany  imported  63,600  barrels,  in  1906  about  68,000  barrels,  and  in  1908  77,000  barrels  (68,000  from 
America  and  9000  from  France)  :  in  1909  the  imports  were  318,884  quintals  (£1,200,000),  and  the  exports  12,457 
quintals,  100,000  tons  of  turpentine  resins  and  balsams  (£880,000)  being  also  imported,  and  21,000  tons  exported. 
In  1909  England  imported  222,000  quintals  of  oil  of  turpentine,  and  in  1910  23,612  tons  (£1,001,216),  whilst  the 
United  States  exported  14,252,000  gallons  (£1,925,400)  in  1910  and  18,198,000  gallons  (£2,187,400)  in  1911. 

Italy's  imports  of  oil  of  turpentine  were  as  follow  :  30,963  quintals  in  1906  ;  30,088  in  1907  ;  33,316  in  1908  ; 
26,932  in  1909,  and  27,941  (£111,760)  in  1910.  In  the  United  States  (on  the  Savannah  market)  the  output  was 
calculated  at  675,000  barrels  in  1907-1908,  725,000  in  1908-1909,  and  580,000  in  1909-1910. 

In  1904  there  were  1287  turpentine  distilleries  in  the  United  States,  with  a  total  capital  of  £1,400,000,  and 
in  1909  1585  distilleries  with  a  capital  of  £2,480,000  and  an  output  valued  at  £5,200,000. 

The  price  varies  from  56s.  to  76*.  per  quintal  and  reached  a  minimum  in  1908. 

The  smell  of  European  turpentine  oil  has  been  improved  by  treatment  with  oxidising  agents,  such  as  perman- 
ganate, persulphates,  or  chromic  acid,  or,  better  still,  with  hydrogen  peroxide  sodium  peroxide,  barium  peroxide, 
or  oxides  of  nitrogen. 

By  suitable  application  of  Halphen's  reagent  (p.  381)  or  mercuric  acetate,  C.  Grimaldi  (1910)  was  able  to 
detect  adulteration  with  pine  oil  or  resin  oil. 


598  ORGANIC    CHEMISTRY 

transformed  by  oxidising  agents  into  camphor  and  by  ozone  into  the  ozonide  (Harries, 
1910),  these  reactions  establishing  its  constitution.  FENCHENE  is  similar  to  camphene 
but  is  an  optically  inactive  liquid,  boiling  at  158°  to  160°  ;  it  resists  the  action  of  nitric 
acid,  but  not  that  of  permanganate. 

CAMPHANE,  C10H18,  forms  white  volatile  crystals  melting  at  154°  and  boiling  at  160°, 
and  is  obtained  by  reducing  d-  or  1-bornyl  iodide.  It  is  optically  inactive,  and  is  the 
saturated  hydrocarbon  of  the  camphor  nucleus. 

HOMOLOGUES  OF  TERPENES.  The  most  interesting  lower  homologue  is  Hemi- 
terpene  or  Isoprene,  C5H8  (see  p.  90),  which  gives  various  terpenic  polymerisation  products, 
such  as  (C6H8)3  (Clovene,  Cedrene,  Caryophyllene,  &c.),  C20H32  (Colophene),  C^H^ 
(Rubber),1  &c. 

1  RUBBER  (caoutchouc)  is  obtained  from  the  milky  juice  exuding  when  incisions  are  made  in  the  stems  of  certain 
plants.  The  latter  are  mainly  tropical  trees  (Apocynece.  Moracece,  Euphorbiacece,  &c.  ;  Siphonia  elastica,  more 
especially  in  Brazil,  and  Urceola  elnstica  in  Eastern  India).  According  to  Henri  (1906-1908),  the  faintly  alkaline 
latex  contains  the  rubber,  ready  formed,  in  the  form  of  minute  emulsified  drops  (50  .millions  per  c.c.),  which 
are  in  continual  movement,  and  of  which  this  author  was  able  to  obtain  a  cinematographic  representation  ; 
a  coagulum  is  produced  by  acids,  by  salts  of  divalent  metals  (Ca,  Mg,  Ba,  &c.),  and  less  rapidly  by  salts  of  trlvalent 
metals,  &c.,  but  not  by  alkalis.  The  conditions  of  coagulation,  which  are  not  identical  with  different  varieties  of 
latex,  are  in  general  related  to  the  quality  of  the  rubber  yielded.  The  best  quality  (Para  rubber)  is  obtained  by 
drying  superposed  thin  layers  of  fresh  latex  in  a  mould  by  means  of  hot  gases  until  about  a  hundred  layers,  each 
about  0-5  mm.  in  thickness,  are  obtained.  The  commoner  qualities  are  set  by  the  heat  of  the  sun,  with  addition 
of  acid,  water,  formalin,  or  a  trace  of  mercuric  chloride  ;  the  electrolytic  separation  of  rubber  has  also  been  suggested 
(Ger.  Pat  218,927  of  1908),  but,  according  to  Pahl  (Ger.  Pat.  237,789  of  1910)  hydrofluoric  acid  or  carbon  dioxide 
gives  the  best  results.  The  fundamental  component  of  rubber,  the  hydrocarbon,  C10H1(,  is  mixed  with  varying 
quantities  of  a  resin  soluble  in  alcohol  or  in  acetone  ;  Para  rubber  contains  less  than  2  per  cent,  of  resin,  but  the 
inferior  qualities  as  much  as  8  to  10  per  cent.  The  removal  of  mineral  substances  and  organic  detritus  is  effected 
by  manipulating,  softening,  and  cutting  the  rubber  in  cold  water,  first  in  a  kind  of  hollander  (see  Paper),  then  in 
a  mechanical  pulping  machine  and  between  rolls  ;  the  water  is  then  removed  and  the  rubber  dried  at  40°  to  50° 
The  consumption  of  rubber  on  a  large  scale  began  fifty  or  sixty  years  ago,  after  it  had  been  found  possible  to 
render  it  unattackable  by  ordinary  reagents  and  solvents  and  to  keep  it  elastic  even  when  exposed  to  the  air  and  to 
heat.  This  is  attained  by  vulcanising  (suggested  in  1839  by  Goodyear  and  by  Hancock),  which  consists  in  mixing 
sulphur  with  the  rubber  and  heating  in  an  oven  or  in  a  steam  apparatus  at  110°  to  140°.  Vulcanisation  can  also 
be  carried  out  in  the  cold,  by  immersing  the  rubber  in  a  mixture  of  sulphur  chloride  and  carbon  disulphide.  The 
weighting  materials  or  fillers,  e.g.  metallic  oxides,  kaolin,  barytes,  &c.  (10  to  15  per  cent.),  are  added  with  the 
sulphur.  In  place  of  sulphur  chloride,  which  may  give  rise  to  a  little  hydrochloric  acid,  Bloch  (Ger.  Pat. 
219,525  of  1908)  has  suggested  hydrogen  disulphide,  H2S2,  or  trisulphide,  H2S3,  dissolved  in  acetone  or  carbon 
disulphide. 

According  to  C.  O.  Weber  and  Henriques  (1894),  in  vulcanisation  in  the  cold,  the  excess  of  S2C12  may  form 
compounds  with  the  rubber  varying  in  composition  from  (C,0Hi,)24,  S2C]2  with  4-3  per  cent.  S,  to  (C10HI6)2,,  (S2C12)21 
with  23-6  per  cent.  8. 

E.  Stern  (1909)  holds  that  the  quantity  of  sulphur  fixed  is  variable,  while  Hinrichsen  (1910)  maintains  that  the 
amount  of  S2C12  combined  is  constant.  Ostwald  (1910)  explains  vulcanisation  as  an  adsorption  phenomenon  of 
the  colloidal  rubber,  and  assumes  that  the  sulphur  forms  a  series  of  reaction  products,  the  first  and  last  members 
of  which  cannot  be  isolated,  and  that  the  process  is  partly  reversible. 

By  protracted  vulcanisation  of  rubber  with  60  to  75  per  cent,  of  sulphur  or  sulphide  and  mixing  in  minera 
substances  (gypsum,  chalk,  inorganic  colours,  &c.),  ebonite  is  obtained.  (Guttapercha  is  similar  to  rubber  bu 
contains  oxygen.) 

Rubber  has  a  brown  or  black  colour  and  is  insoluble  in  water  when  not  vulcanised,  and  more  or  less  soluble 
n  chloroform,  ether,  petroleum  ether,  benzene,  or  carbon  disulphide.  A7ulcanised  rubber  is  almost  insoluble  in 
these  substances,  but  dichlorethylene,  C2H2C12,  forms  an  excellent  and  non-inflammable  solvent. 

With  age,  rubber  (tubing,  &c.)  becomes  hard  and  brittle,  and  cracks.  According  to  Wo.  Ostwald  (Ger.  Pat 
221,310  of  1908),  it  lasts  longer  if  quinoline,  aniline,  dimethylaniline,  A-c.,  is  used  in  its  preparation. 

Rubber  is  recovered  from  vulcanised  waste  by  subjection  of  the  latter,  after  removal  of  the  impurities  and 
comminution,  to  the  action  of  steam  under  a  pressure  of  6  atmos.  By  this  means  a  large  part  of  the  sulphur 
seems  to  be  converted  into  sulphuric  acid,  which  can  be  readily  removed  with  water  or  soda.  The  residue  is  com- 
pressed into  strips,  but  it  is  always  an  inferior  product.  There  are  now  numerous  patents,  some  of  them  fanciful 
for  devulcanising  rubber  by  means  of  alkaline  solutions,  phenols,  naphthalene,  aniline  (Ger.  Pat.  99,689),  &c.  In 
1907  Tissier  obtained  good  results  by  macerating  used,  finely  divided  rubber  with  double  its  weight  of  terpineol 
in  a  closed  vessel  at  120°  to  150°,  then  diluting  with  4  parts  of  benzene  and  decanting  the  solution  from  the 
impurities.  The  benzene  is  recovered  by  direct  distillation  and  the  terpineol  by  distillation  in  steam.  In  general, 
devulcanisation  is  based  on  depolymerisation  of  the  vulcanised  rubber  where  the  sulphur  is  not  united  chemically 
with  the  rubber  ;  it  is  almost  impossible  to  eliminate  the  sulphur  which  is  combined  chemically.  Old  rubber,  well 
devulcanised  and  then  again  vulcanised,  seems  to  give  a  more  resistant  product  but  of  lower  quality.  The  United 
States  import  10,000  tons  of  used  rubber  for  "  reclaiming."  The  Mitchell  process  is  often,  used  in  America  for 
obtaining  rubber  from  old  articles  (boots,  rubbered  textiles,  &c.),  which  are  treated  with  sulphuric  acid  of  20°  to 
25°  Be1.,  this  destroying  the  textile  fibres  but  not  the  rubber. 

The  chemical  constitution  of  the  hydrocarbon  of  rubber,  C10H,,,  was  determined  by  Harries  (1905)  by  means  of 
its  ozonide,  C,0H,,O6,  which  decomposes  into  levulinic  aldehyde,  so  that  the  hydrocarbon  must  be  regarded  as 

OH3-C  •  CH2  •  CH2  •  CH 
derived  from  an  eight-carbon-atom  ring  (a  ring  never  yet  found  in  natural  products);  ||  || 

CH-  CH2-CH2-C-CH8. 

In  1909  Harries  obtained  true  artificial  rubber  by  polymerising  isoprenc  in  presence  of  glacial  acetic  acid  in 
sealed  tubes  at  100°  :  (2C5H8)j.  =  (Ci0H16)r,  but  the  process  is  too  expensive  to  be  used  industrially.  The  firm 
of  Bayer  (Elberfeld)  also  obtained  artificial  rubber  from  isoprene  and  from  Erythrene  C4H,  (see  p.  90 ;  also 
Ger.  Pat.  235,423  and  235,686  of  1909  and  Fr.  Pat.  425,582  of  1911),  by  prolonged  heating  in  presence  of  benzene, 
&c.,  but  this  product  is  also  very  expensive  ;  in  consequence  of  this  method  of  formation,  the  formula  attributed 


RUBBER  599 

Other  hydrocarbons  related  to  the  terpenes  are :  ionene  and  irene,  two  isomerides 
of  the  formula,  C^H^,  the  ketones  of  which,  C^H^O,  are  irone  and  ionone,  i.e.  the  aromatic 
principle  of  iris  root,  having  a  marked  violet  smell. 

IONONE  (Artificial  Essence  of  Violets)  was  prepared  synthetically  by  Tiemann  and 
Kriiger  in  1883  by  shaking  equal  proportions  of  citral  and  acetone  with  barium  hydroxide 
solution,  extracting  with  ether  and  expelling  the  latter  by  evaporation. 

The  fraction  of  the  residue  boiling  at  138°  to  155°  is  Pseudoionone,  which  is  transformed 
into  the  isomeric  ionone  by  the  action  of  dilute  acid  (Ger.  Pat.  75,120).  According  to 
Ger.  Pat.  113,672,  the  condensation  may  be  effected  by  water  in  an  autoclave  at  170°, 
while  in  presence  of  sodamide  it  takes  place  at  the  ordinary  temperature  (Ger.  Pat. 
147,839).  See  also  Ger.  Pat.  138,939. 

by  Harries  to  the  hydrocarbon  is  now  contested.  Various  patents  have  recently  been  taken  out  for  the  preparation 
of  isoprene,  dimethylbutadiene,  erythrene,  &c.,  as  prime  materials  for  artificial  rubber  (Eng.  Pats.  29,566  and  29,277 
of  1909).  The  Badische  Anilin  und  Sodafabrik  (Ludwigshafen)  obtained  rubber  by  heating  isoprene  and  dimethyl- 
butadiene  (Fr.  Pats.  417,170  and  417,768  and  Eng.  Pat.  14,281  of  1910)  in  presence  of  alkali,  which  has  a  poly- 
merising action.  Harries  (1911)  showed  that  various  isomeric  artificial  rubbers  exist,  with  the  generic  formula 
fioTI,,,  C8H12.  Contrary  to  Weber's  statement,  Hinrichsen  (1909)  showed  that  the  latex  of  rubber  trees  does  not 
contain  diterprncs,  which  polymerise  to  form  rubber,  but  that  the  latter  exists  ready  formed  in  the  latex. 

The  world's  production  of  rubber  was  52,190  tons  in  1899  ;  59,750  in  1901  ;  68,500  in  1904  ;  73,680  in  1905  ; 
75,300  in  1907,  and  about  80,000  tons  (£30,000,000)  in  1910-1911.  The  French  East  African  possessions  give 
7000  tons  ;  the  French  Congo  3000  and  the  Belgian  Congo  6000.  The  total  consumption  in  1904  was  distributed 
as  follows  :  United  States,  26,470  tons  ;  Germany,  12,800  (about  15,600  in  1909) ;  England,  10,000  ;  France, 
4130  ;  Austria-Hungary,  1320  ;  Holland,  1218  ;  Belgium,  748  (increasing  rapidly) ;  Italy,  548.  One-half  of  the 
world's  output  of  rubber  comes  from  Brazil,  which  produced  28,600  tons  in  1902  and  nearly  34,500  tons  in  1908. 
Mexico  exports  rubber  to  the  value  of  £1,280,000.  The  exports  from  Ceylon  were  450  tons  in  1908  ;  750  in  1909, 
and  1700  in  1910,  while  Abyssinia  exported  9  tons  in  1908  and  79  tons  (£15,280)  in  1909.  A  considerable  part 
of  the  total  output  of  rubber  comes  from  Africa  (Senegal,  Madagascar,  the  Congo,  the  Cameroons,  &c.),  the  exports 
being  16,000  tons  in  1900  and  23,500  in  1906.  The  East  Indies  produce  about  2000  tons  per  annum,  but  the  culti- 
vation of  rubber  is  increasing  rapidly.  Brazil  exported  about  27,000  tons  of  rubber,  at  £60  per  ton,  in  1902  ; 
31,600  tons  in  1905  ;  and  35,000  tons,  valued  at  £1,720,000,  in  1906.  In  Malacca  the  English  have  rapidly  extended 
the  rubber  plantations,  the  exports  being  valued  at  ,£17,000  in  1900,  ana  at  £720,000  (1580  tong)  in  1908,  1017 
tons  being  exported  in  1907.  The  number  of  rubber-producing  trees  was  27,500,000  in  1907,  and  37,500,000  in- 
1908.  The  most  suitable  climate  and  soil  for  rubber  are  found  at  Malacca. 

The  areas  under  nibber  in  different  countries  in  1911  were  as  follow':  Malacca,  170,000  hectares  ;  Ceylon  and 
Southern  India,  110,000  ;  Borneo,  35,000  ;  Mexico,  Brazil,  and  Africa,  together,  45,000  ;  German  colonies,  20,000 
The  mean  yield  of  rubber  is  calculated  at  42  kilos  per  hectare  in  Ceylon  and  38  in  Samoa. 

The  Russo- American  Ilubber  Company  of  St.  Petersburg  produced  rubber  articles  to  the  value  of  £4,800,000 
in  1907,  £5,360,000  in  1908,  and  £5,800,000  in  1909. 

In  Germany  there  were  339  factories  (with  12,500  employees)  for  making  rubber  and  gutta-percha  articles  in 
1895,  and  100  factories,  with  35,000  employees,  a  capital  of  £5,600,000,  and  an  annual  output  valued  at  £10,000,000, 
in  1908.  ID  1904  Germany  imported  17,407  tons  of  rubber  of  the  value  of  £5,400,000,  and  exported  4569  tons, 
worth  £1,400,000.  In  1908  Germany  imported  more  than  13,000  tons  of  raw  rubber,  1500  tons  of  it  from  the 
German  African  colonies,  especially  the  Cameroons  ;  in  1910  the  imports  were  about  10,000  tons. 

In  Italy  the  firm  of  Pirelli  and  Co.,  founded  in  1872,  has  two  factories  for  the  working  of  rubber,  with  a  total 
capital  of  £600,000,  an  annual  turnover  of  £640,000  (including  submarine  cables),  and  about  4000  operatives.  A 
less  important  factory  is  that  of  the  Italian  company  for  the  manufacture  of  rubber  at  Milan.  Eaw  rubber  imported 
into  Italy  pays  no  duty,  but  the  manufactured  product  pays  from  £2  to  £3  per  quintal.  The  imports  of  raw  rubber 
and  gutta-percha  amounted  to  6688  quintals  in  1904,  7669  in  1905, 1500  in  1908,  and  18,800  (£980,000)  in  1910;  the 
exports,  in  the  form  of  string,  ribbon,  and  tubing,  being  639  quintals  in  1904,  1183  in  1905,  and  109  in  1910.  The 
total  imports  were  5715  quintals  in  1904,  8061  in  1905,  2400  in  1908,  and  2300  (£112,000)  in  1910  ;  and  the  tota 
exports,  3580  quintals  in  1904,  4884  in  1905,  625  in  1908,  and  1150  (£92,000)  in  1910. 

Belgium  occupies  1900  workpeople  in  the  rubber  industry  and  France  9000  (in  1901). 

The  amount  of  rubber  imported  into  England  was  35,000  tons  (£14,138,200)  in  1909  and  43,500  tons(£26,096,790 
together  with  4800  tons  (£1,136,500)  of  gutta-percha,  in  1910. 

The  imports  of  rubber  to  the  United  States  were  40,500  tons  (£19,600,000)  in  1910  and  37,000  tons 
(£14,880,000)  in  1911,  in  addition  to  16,000  tons  (£601,000)  of  waste  rubber  in  1910  and  8600  tons  (£306,000)  in 
1911. 

Gutta-percha  resembles  rubber,  and  is  obtained  mostly  in  Singapore  and  Borneo  from  a  large  tree,  Isonandra 
percha.  After  purification  and  manipulation  in  hot  water,  it  sets  in  the  cold  to  a  hard  mass,  soluble  slightly  in 
ether  and  alcohol  and  more  readily  in  hot  benzene,  carbon  disulphide,  or  chloroform.  It  is  used  as  an  electrica 
insulator  and  for  making  various  articles. 

The  price  of  raw  rubber  has  increased  rapidly  from  320*.  per  quintal  in  1850  to  448s.  in  1890  and  664s.  in  1907 
(at  Hamburg).  The  finer  qualities  of  Para  rubber  cost  720s.  in  1902,  1280s.  in  1905,  and  1280s.  to  1600s.  in  1909 
Gutta-percha  costs  360s.  per  quintal.  It  is  estimated  that  the  cost  of  native  labour  in  the  Congo  district  is  not 
more  than  120s.  per  quintal. 

RUBBER  SUBSTITUTES.  Many  of  these  have  been  prepared,  but  the  only  one  of  much  practical  import- 
ance is  the  so-called  factis,  of  which  two  types  are  on  the  market :  white  and  brown  or  black.  The  latter  is  made  by 
boiling  rape  oil  or  linseed  oil  in  an  open  vessel  for  two  hours,  cooling,  and  passing  a  current  of  air  through  it  for 
thirty-six  hours.  It  is  then  vulcanised  by  adding  2  per  cent,  of  flowers  of  sulphur,  heating  for  two  hours  at  140° 
adding  a  further  1  per  cent,  of  sulphur,  and  raising  the  temperature  to  150°,  when  it  begins  to  rise.  White  factis 
is  obtained  by  treating  the  oil  with  20  to  25  per  cent,  of  sulphur  chloride  (free  from  dichloride) ;  the  energy  of  the 
reaction  may  be  modified  by  adding  the  sulphur  chloride  dissolved  in  carbon  disulphide.  The  mass  is  obtained 
in  sheets  or  blocks  by  pouring  it  immediately  on  to  cold  metal  plates  or  moulds.  These  substitutes  are  almost 
as  elastic  as  rubber  and  are  used  to  adulterate  rubber,  their  price  being  72s.  to  96s.  per  quintal ;  they  are  insoluble 
In  water  or  acid,  but  dissolve  slightly  in  dilute  alkali.  They  are  distinguished  from  rubber  by  being  saponiflable 
with  alcoholic  potash. 


600  ORGANIC    CHEMISTRY 

The  constitution  of  synthetic  ionone  is  : 

CH3     CH3 

v 

C  . 


CH2      CH-CH:CH-CO-CH3 

I 
CIi2      C  •  CH3 

\/ 
CH 

Ionone  (100  per  cent.)  costs  £152  per  kilo,  and  fi-ionone,  £60  ;  the  20  per  cent,  solutions 
are  sold  at  one-fifth  of  these  prices. 


CAMPHORS 

While  the  terpenes  are  liquids, -the  camphors  are  generally  solid.  They 
contain  alcoholic  or  ketonic  oxygen,  and  the  principal  ones  with  a  single  ring 
are  :  Menthone,  C10H]8O,  and  Terpinol  with  the  same  formula,  while  Menthol 

H,n09.     Among  the  camphors 


and  Carvomenthol  are  C10H20 


0,  andTerpin  C10j.j.20w2. 


with  complex  rings  are  true  Camphor,  Fenchone,  and  Carone.  C10H160,  and 
Borneol,  C10H180. 

The  camphors  poorer  in  hydrogen  and  oxygen  contain  double  linkings, 
form  additive  products,  and  are  readily  oxidised,  while  the  others  behave  like 
saturated  compounds. 

When  reduced  with  sodium,  the  ketonic  camphors  yield  the  alcoholic 
camphors,  which  are  converted  into  the  former  on  oxidation.  It  is  possible 
to  pass  from  the  camphors  to  the  terpenes  by  way  of  the  chlorides,  and  reduction 
of  the  alcoholic  camphors  often  gives  the  terpene  hydrocarbons.  Thus,  the 
Terpane  (hexahydrocymene)  can  be  obtained  by  reducing  the  Terpanol  (menthol, 
C10H200),  which  contains  a  hydroxyl  or  secondary  alcoholic  group,  this  being 
transformed  by  oxidation  into  the  ketonic  group  with  formation  of  Terpanone 
(menthone),1  so  that  the  hydroxyl  should  be  in  the  ortho -position  with  respect 
to  the  CH3  and  C3H7  groups,  as  is  shown  below  in  the  constitutional  formulae. 

214 

On  the  other  hand,  since  Carvacrol,  C6H3(OH)(CH3)(C3H7)  (isomeric  with 
carvone  or  carvol),  of  known  constitution,  gives  on  reduction  a  terpanol 
(carvomenthol  with  the  hydroxyl  in  the  position  2)  different  from  that  of  menthol, 
the  hydroxyl  of  the  latter  must  be  in  position  3  : 


H    CH< 


H    CH, 


H    CH< 


H    CH, 


H2 

H(OH) 


H, 


H    C3H7 

Menthol 
(terpanol),  C10H20O 


H, 


Menthone 
(terpanone),  C10H18O 


H(OH) 
H, 


H     C3H7 

Carvomenthol 
Ci0H20O 


H    C,H7 

Carvomenthone 
Ci.HI80 


MENTHOL  (3-Terpanol),C10H19-  OH,  occurs  in  abundance  in  oil  of  peppermint,  from 
which  it  can  be  obtained  crystalline  by  cooling.  It  melts  at  42°,  boils  at  213°,  and  has 
the  strong  odour  of  peppermint.  The  position  of  the  OH  is  established  by  the  fact  that, 

1  Ciamician  and  Silber  (1910)  showed  that,  in  alcoholic  solution  and  nnder  the  action  of  light    menthone  i« 
hydrolysed  with  formation  of  decoic  acid,  and  nn  aldehyde  isomeric  with  citronellal  (p.  210) 


CAMPHORS  601 

with  bromine  in  chloroform  solution,  menthone  (which  is  the  corresponding  ketone,  boiling 
at  207°,  and  having  a  strong  smell  of  peppermint)  gives  dibromomenthone,  and  elimination 

of  2HBr  from  the  latter  gives  thymol  having  the  known  constitution,  C3H  Y  ^>CH3  ; 

o!T~ 

the  CH3  and  OH  are  here  undoubtedly  in  the  meta -position,  since  elimination  of  the  C3H7 
by  means  of  P2O5  yields  m-cresol.  When  heated  with  copper  sulphate,  menthol  yields 
cymene.  Four  isomerides  of  menthol  are  possible  theoretically.  It  is  used  as  an  anaesthetic 
and  as  a  disinfectant. 

PULEGONE  (A4(8)-Terpen-3-one),  C10H16O,  predominates  in  oil  of  pennyroyal 
(Mentha  pulegiiim).  It  is  a  ketone  boiling  at  222°,  and  on  reduction  gives  menthol,  so 
that  the  carbonyl  group  is  in  position  3. 

CARVONE  (Carvol  or  Terpadien-2-one),  C10H14O,  is  a  ketone  giving  Carvoxime, 
C10H14  :  NOH,  which  exists  in  optical  isomerides  and  is  identical  with  nitrosolimonene. 
It  forms  the  principal  component  of  cumin  oil,  boils  at  228°,  and  is  converted  into  Carvacrol, 
C10H13-  OH,  when  heated  with  potash  or  phosphoric  acid  : 

CH3  CH3 

I     '  I 

C  C 

/\  /\ 

CH    CO  CH    C-OH 

CH2  CH2  CH    CH 

\/    '  \/ 

CH  C 

I  I 

CH3— C  =  CH2  CH3— CH— CH3 

Carvone  Carvaorol 

TERPENOL  (A4(s)-Terpen-l-ol),  C10H18O,  melts  at  70°,  and,  like  tetramethylethylene, 
forms  a  solid  blue  nitrosochloride,  the  double  linking  being  in  the  4(8)-position,  between 
two  tertiary  carbon  atoms. 

TERPINEOL  (A^Terpen-S-ol),  C10H18O,  melts  at  35°,  boils  at  218°,  and  is  known 
in  the  form  of  various  optically  active  isomerides.  It  has  a  pleasing  odour  of  lily  of  the 
valley,  lilac,  and  cyclamen,  and  occurs  in  ethereal  oils.  With  sulphuric  acid  it  forms 
terpin  hydrate,  which  is  also  converted  back  into  terpineol  by  sulphuric  acid. 

TERPIN  (1  :  8-Terpandiol),  Ci0H18(OH)2.  Terpin  hydrate,  CxoHaoO^HaO,  is  slowly 
formed  from  oil  of  turpentine,  C10H16,  in  contact  with  dilute  nitric  acid  and  alcohol.  This 
crystalline  hydrate  melts  at  117°  and  then  loses  1  mol.  of  H20,  anhydrous  terpin  distilling 
over  at  258°.  This  is  optically  inactive  and  is  not  obtainable  in  active  modifications, 
so  that  the  presence  of  asymmetric  carbon  atoms  is  excluded.  The  hydrate  is  also  obtainable 
from  geraniol  by  the  prolonged  action  of  5  per  cent,  sulphuric  acid,  2H20  being  added  at 
the  double  linkings : 

CH3  CH3  CH3  CH3 

\/  i  I 

C  CH3— C— OH  CH3— C— OH 

II  I  I 

CH  CH2  CH 

/  /  /\ 

CH2  CH2-OH      „  nw  CH2  CH2-OH  CH2  CH 

I     "     I  .    Jl'Un  I  |  TT  n 


+      TT      0TT  >  |  n2^ 

CH2   CH  CH2  CH2  CH2   CH2 

Y  Y  .     Y 

I  /\  /\ 

CH,  CH3  OH  CH3  OH 

Geraniol  Terpin  hydrate  Terpin 


602  ORGANIC    CHEMISTRY 

Nitric  oxide  oxidises  terpin,  giving  Terebic  Acid,  which  has  the  known  constitution  • 

C02H 

(CH3)2  :  C  •  CH  •  CH2 

'    !  I' 

O CO 

so  that  the  position  8  must  be  occupied  by  a  hydroxyl ;  the  other  hydroxyl  can  only  be 
in  position  1,  since  otherwise  an  asymmetric  carbon  atom  would  be  obtained. 

CINEOL,  CioHigO,  has  the  constitution  of  terpin  less  H2O,  which  is  eliminated  from 
the  two  hydroxyls,  an  atom  of  oxygen  thus  remaining  united  to  the  two  carbon  atoms 
1  and  8.  Cineol  melts  at  —  1°,  boils  at  176°  and  occurs  in  abundance  in  eucalyptus  oil 
and  in  oil  of  wormseed. 

FENCHONE,  C10H16O.  The  dextro-form  occurs  in  fennel  oil  and  the  la?vo  in  thuja 
oil.  It  is  a  ketone  similar  to  camphor  and  can  be  converted  into  Fenchene. 

CAMPHOR  (ordinary  camphor,  laurel  camphor,  or.  Japan  Camphor). 
C10H16O,  is  the  constituent  which  separates  in  the  solid  form  from  the  essential 
oil  of  Laurus  camphora,  a  tree  which  is  cultivated  in  China,  Japan,  and  Formosa , 
and  grows  well  in  Southern  Europe  (Italy). 

The  wood  (thirty  to  forty  years  old)  is  chopped  up  and  boiled  with  water 
until  the  camphor  floats  at  the  surface  ;  on  cooling,  the  crude  camphor  sets 
to  a  solid  mass,  which  can  readily  be  separated.  In  some  cases  the  camphor 
is  distilled  directly  from  the  wood  in  a  current  of  steam.  The  yield  is  about 
1  kilo  per  quintal  of  wood.  The  crude  product  is  refinsd  by  mixing  with  quick- 
lime and  charcoal  and  subliming  at  a  gentle  heat. 

It  is  obtained  thus  as  a  white,  crystalline,  and  not  very  hard  mass,  which 
has  a  characteristic  odour,  and  partially  sublimes  at  the  ordinary  temperature. 
It  melts  at  178°,  boils  at  207°,  and  has  the  sp.  gr.  0-922-0-995  (the  finer  Borneo 
camphor  has  sp.  gr.  1-10).  In  alcoholic  solution  it  is  more  or  less  dextro- 
rotatory, according  to  its  origin,  but  matricaria  camphor  (from  the  leaves  of 
feverfew,  Matricaria  parthenium)  is  laevo-rotatory. 

With  iodine  in  the  hot  it  forms  carvacrol  (we  above),  while  oxidation  with 
nitric  acid  gives  Camphoric  Acid,  C8H14(C02H)2,  which  exists  in  two  active 
and  two  inactive  forms.  Further  oxidation  yields  Camphoronic  Acid.  C9H1406, 
which  gives  trimethylsuccinic  acid  on  dry  distillation.  When  distilled  with 
P205,  camphor  loses  H20  and  forms  cymene.  On  reduction  with  nascent 
hydrogen,  ordinary  camphor  gives  Borneol  (Borneo  camphor),  C10H17-OH, 
which  melts  at  208°,  boils  at  212°,  and  when  oxidised  gives  ordinary  camphor, 
which  it  strongly  resembles. 

Between  1860  and  1893  various  constitutional  formulae  for  camphor  were 
proposed  by  Kekule,  Armstrong,  Bredt  (1884),  and  G.  Oddo  (1891),  the  last 
of  whom  gave  a  formula  which  explained  well  all  the  reactions  and  properties 
observed  up  to  that  time.  More  and  more  acceptable  constitutions  were 
given  by  Widmann  (1891),  Collie  (1892),  Bouveault  (1892),  &c.,  and  finally 
by  Bredt  (1893). 

The  constitution  of  camphor  now  seems  to  be  definitely  established  as  the 
result  of  various  syntheses,  especially  that  from  ethyl  oxalate  and  ethyl 
/3/3-dimethylglutarate,  two  compounds  which  are  obtainable  synthetically 
from  their  elements.  The  various  stages  in  this  synthesis  are  as  follow, 
R  indicating  the  alkyl  group  : 
COOR  H-CH-C02R  CO  •  CH  •  C02R  CO  — CH-  C02R 


+     CH.-C-CH, 


°CH. 


CH.,  "C  'CHr 


COOR  H-CH-C02R          CO  •  CH  •  C02R          CO  —  C(CH3)-C02R 

Ethyl  Ethy  /3/3-dimethyl-  Ethyl  diketoapo-  Ethyl  diketo- 

oxalate  glutarate  camphorate  camphorate 


CH  , — C — CH  t 


CAMPHOR  603 

\ 


CH2  —  CH  - C02R          CH2  —  CH  —  CH2v  CH2  —  CH-CH2 -ON 


q— C— CH,  >0 


CH,— C— CH 


3 — r*J *~>i.i.  3 


CH2—  C(CH3)-C02R      CH2—  C(CH3).Or  CH2  —  C(CH3)— CO2H 

Ethyl  campliorate  Campholidc  Homocamphoric  nitrile 

CH2  -CH— CH2.C02H  CH2— CH CH2 


CH  , — C — CH  •: 


CH,— C— CH 


CH2  —  C(CH3)— C02H  CH2  —  C(CH3)— CO 

Homocamphoric  acid  Camphor  a 

This  constitutional  formula  proposed  for  a-camphor  by  Bredt,  although 
still  contested,  is  the  one  generally  accepted  by  chemists,  since  it  corresponds 
best  with  most  of  the  reactions  of  camphor.  In  1911,  Bredt  and  Hilbing 
prepared  (3-camphor,  containing  the  CO  group  in  the  /3-position,  from  bornylene- 
carboxylic  acid  ;  it  melts  at  182°  and  boils  at  213-4°. 

Camphor     forms     strongly    rotating     energetic     sulphonic     acids,     e.g. 

CH-S03H 
C8H14<^  |  ,  which  are  able  to  resoive  many  racemic  compounds  into 

^CO 
their  active  components. 

Since  many  terpenes  give  camphor  on  oxidation,  many  attempts  have  been 
made  to  prepare  artificial  camphor  from  oil  of  turpentine.1  The  latter  contains 
pinene,  C10H16,  which  is  readily  convertible  into  borneol,  C10H]7-OH,  or 
isoborneol,  this  giving  the  inactive  racemic  compound  corresponding  with 
natural  camphor  on  oxidation. 

According  to  Ger.  Pat.  134,553,  when  anhydrous  turpentine  is  heated  for  a  long  time 
at  120°  to  130°  with  dry  oxalic  acid,  a  mixture  of  camphor  with  pinyl  formate  and  oxalate 
is  obtained  ;  after  washing  with  water,  the  latter  are  hydrolysed  with  alkali  and  the 
resultant  borneol  converted  into  camphor  by  oxidation  with  dichromate  and  sulphuric 
acid. 

At  Monville,  near  Rouen,  a  factory  was  erected  in  1906  to  manufacture  artificial  camphor 
by  the  process  described  in  Fr.  Pat.  349,896  (of  Behal,  Magnier,  and  Tissier,  and  similar 
to  U.S.  Pat.  779,377) :  A  mixture  of  oil  of  turpentine  and  salicylic  acid  is  heated  and, 
after  elimination  of  the  excess  of  the  reagents,  the  isoborneol  ether  is  hydrolysed  to  a 
mixture  of  borneol  and  isoborneol.  Another  factory,  near  Calais,  utilises  Schering's  method 
(Fr.  Pat.  341,513),  already  in  use  on  a  large  scale  in  Berlin,  and  also  applied  in  a  factory 
established  in  1909  in  Finland. 

According  to  Fr.  Pat.  349,852,  pinene  hydrochloride  is  first  prepared  and  then  heated 
under  pressure  with  lead  acetate  in  acetic  acid  solution,  thus  giving  camphene,  which  with 
permanganate  forms  camphor  ;  or  treatment  of  the  pinene  hydrochloride  with  a  formate 
gives  the  formic  ester  of  borneol,  which  can  be  readily  hydrolysed.  The  final  oxidation  to 
obtain  camphor  is  carried  out  in  various  ways :  by  oxidising  the  borneol,  in  benzene  or 
petroleum  ether  solution,  with  aqueous  alkaline  permanganate  (Ger.  Pat.  157,590),  or  by 
means  of  ozone,  air,  or  chlorine  water  (see  Eng.  Pat.  28,036  of  1907  and  Ger.  Pats.  166,722 

1  It  has  been  pointed  out  that  a  difficulty  in  the  way  of  the  further  development  of  the  present,  artificial  camphor 
industry  may  be  the  excessive  price  of  oil  of  turpentine,  this  having  risen  from  56s.  per  quintal  in  1900  to  96s. 
in  1906  ;  these  conditions  might  easily  be  aggravated  by  the  formation  of  a  trust.  Further,  the  demand  for 
camphoi  may  diminish  in  the  future,  since  substitutes  are  continually  being  found  capable  of  replacing  it  in 
celluloid,  which  up  to  the  present  has  consumed  about  two-thirds  of  the  total  camphor  produced.  The  fact  that 
natural  camphor — almost  entirely  monopolised  by  the  Japanese  Government — can  be  sold,  without  loss,  at  144s. 
per  quintal  constitutes  a  menace  to  the  future  of  artificial  camphor,  which  could  never  be  sold  at  that  price  and 
depends  on  a  raw  material  the  price  of  which  cannot  be  regulated.  In  addition  to  the  70  per  cent,  absorbed 
in  the  manufacture  of  celluloid,  natural  camphor  is  used  for  explosive  powder  and  guncotton  (2  per  cent.),  for 
pharmaceutical  preparations  (13  per  cent.)  and  for  various  other  purposes  (15  per  cent.) 


604  ORGANIC    CHEMISTRY 

and  154,107),  or  by  oxidising  isoborneol  in  aqueous  acid  solution  with  permanganate 
(Ger.  Pat.  197,161  of  1906). 

Camphor  was  obtained  by  A.  Hesse  by  means  of  the  Grignard  reaction,  and  it  is  also 
formed  by  fusing  borneol  with  finely  divided  nickel  (1911). 

Natural  camphor  may  be  distinguished  from  the  artificial  product  by 
mixing  it  intimately  with  an  equal  weight  of  chloral  hydrate  :  the  former 
gives  a  syrupy  mass,  but  the  latter  does  not  liquefy.  Camphor  is  used  in 
pharmacy,  for  fireworks  and  nightlights  and,  in  large  quantities,  in  the  manu- 
facture of  celluloid  x  and  for  rendering  explosives  insensitive  to  shock.  The 
price  of  camphor  varies  somewhat,  and  during  the  Russo-Japanese  War  rose 
considerably  ;  it  is  usually  about  £24  per  quintal.  The  cost  price  of  artificial 
camphor  seems  to  be  about  4s.  per  kilo. 

The  production  of  camphor  in  Japan  and  Formosa  (State  monopoly)  amounted  to  about 
3,500,000  kilos  (three-fourths  in  Formosa)  in  1906,  and  to  4,300,000  kilos,  2,000,000  kilos 
being  exported  (two-thirds  to  Havre,  London,  and  Hamburg,  and  one-third  to  America),  in 
1907.  After  the  war  with  Russia,  Japan,  with  her  monopoly  of  the  production  of  camphor, 
tried  to  raise  the  price.  From  about  2s.  5d.  per  kilo  in  1903  it  became  4s.  5d.  in  1906 
and  1907.  At  the  same  time  large  plantations  were  laid  out  in  Formosa,  1,300,000  trees 
being  planted  in  1907,  about  1,400,000  in  1908,  and  more  than  5,000,000  in  1909.  The 
rise  in  price  caused  increased  production  of  artificial  camphor  in  Europe,  and,  owing  to 
this  competition,  the  price  fell  again  to  2s.  per  kilo  at  Japanese  ports  in  1911.  The  exporta- 
tion from  Japan,  which  had  fallen  to  1,500,000  kilos  in  1908,  rose  to  2,430,000  kilos  in 
1909,  but  steps  are  now  being  taken  to  regulate  the  output  so  that  the  price  may  not  be 
lower  than  the  actual  cost  of  production,  this  being  about  Is.  Qd.  in  Formosa  and  2s.  Wd. 
for  camphor  produced  in  Japan. 

In  1906  Japan  prepared  1,600,000  kilos  and.  in  1907  more  than  3,000,000  kilos  of 
camphor  oil. 

An  association  was  formed  in  the  United  States  in  1908  to  sterilise  the  camphor  trees 
of  Florida  and  Texas,  the  system  of  cultivation  being  thus  improved. 

The  exports  of  camphor  from  China  were  as  follow  :  120  quintals  in  1902  ;  660  in  1903  ; 
725  in  1904;  2450  (£60,000)  in  1905  ;  6000  (£220,000)  in  1906  ;  11,600  (£280,000)  in  1907— 
the  total  output  being  16,000  quintals  ;  4820  (£108,000)  in  1908,  the  total  output  being 
8000  quintals  ;  £100,000  worth  in  1909  and  still  less  in  1910.  Trees  have  been  used  up 
in  China  without  new  plantations,  which  require  40  years  before  giving  good  trees,  being 
established.  Continuance  of  this  procedure  will  result  in  the  complete  destruction  of  camphor 
trees  in  China  in  seven  or  eight  years. 

England  imported  nearly  387  tons  of  camphor  in  1899  ;  France  about  546  tons  and 
Germany  more  than  1000  tons  (£320,000)  in  1903.  The  average  price  of  camphor  in  Hamburg 
was  141s.  in  1881-1885,  181s.  in  1886-1890,  235s.  in  1891-1895,  268s.  in  1896,  and  200s. 
in  1897.  It  now  tends  to  increase  owing  to  the  Japanese  monopoly. 

The  United  States  imported  in  1910  1700  tons  (£226,000)  of  crude  natural  camphor, 
and  in  1911  1150  tons  (£165,000),  besides  160  tons  (£23,000)  of  purified  and  artificial 
camphor.  The  exports  of  celluloid  and  articles  made  therefrom  amounted  to  £286,800 
in  1910  and  £420,200  in  1911. 

The  world's  consumption  of  camphor  is  about  5000  to  6000  tons,  almost  all  placed  on 
the  market  by  Japan,  which  has  collected  Chinese  camphor  since  the  monopoly  there 
came  to  an  end  in  1904. 

Camphor  is  not  produced  in  Italy,  where,  however,  according  to  the  excellent -mono- 

1  Celluloid  is  obtained  by  mixing  nitrocellulose  and  camphor  in  the  following  manner  :  well-stabilised 
powdered,  and  partially  dried  collodion-cotton  (with  10  to  11  per  cent.  N.  ;  see  p.  239)  is  soaked  in  alcohol  in  a  covered 
centrifuge,  then  gelatinised  with  alcohol  and  one-third  or  one-fourth  of  its  weight  of  camphor,  coloured,  if  necessary, 
homogenised  between  rolls  and  then  formed  into  dense,  compact  blocks  by  pressing  while  hot.  It  is  then  ready 
to  be  cut,  sawn,  compressed,  polished,  &c.,  its  marked  plasticity  when  hot  being  utilised  in  working  it.  It  is  a 
homogeneous,  transparent,  colourless,  or  yellowish  substance  without  teste  and  of  sp.  gr.  1-37.  If  sufficiently 
dry  it  is  odourless,  but,  when  rubbed  or  heated,  it  develops  a  slight  smell  of  camphor.  It  is  a  very  bad  conductor 
of  heat  and  electricity,  and  its  elasticity  is  about  equal  to  that  of  ivory. 

Celluloid  is  used  for  making  toys,  balls,  combs,  walking-stick  handles,  tortoiseshell  objects  (substitutes  for 
tortoiseshell,  amber,  ebonite,  &c.),  films,  &c.  It  has  the  disadvantage  of  burning  rapidly  and  energetically  (without 
exploding)  when  brought  into  contact  with  an  ignited  or  incandescent  body.  If  the  collodion -cotton  used  is  well 
stabilised,  celluloid  will  withstand  a  temperature  of  125°  or  even  higher.  It  can  be  charged  with  mineral  substances 
to  render  it  less  inflammable  and  heavier. 


CONDENSED  BENZENE  NUCLEI     605 

« 

graph  presented  by  Giglioli  at  the  International  Congress  of  Applied  Chemistry  at  Rome 
(1906),  it  could  be  produced  advantageously  on  a  large  scale.  Italian  requirements  are 
met  by  the  importation  of  20  to  25  tons  per  annum  of  refined  camphor  from  Germany 
at  a  price  of  280s.  per  quintal  prior  to  1898, 400s.  after  1902,  and  480s.  after  1908  ;  the 
import  duty  is  20s.  per  quintal.  Italy  imported  1000  quintals  of  celluloid  in  1906,  2407  in 
1909,  and  4267  (£102,410)  in  1910. 

The  value  of  the  imports  of  celluloid  into  Japan  were :  £48,000  in  1905,  £80,000  in 
1906,  £30,000  in  1907,  and  £60,000  in  1908.  The  import  duty  is  £4  per  quintal  for  celluloid 
in  strips  or  in  the  crude  state,  and  40  per  cent,  for  manufactured  articles.  Two  large 
celluloid  factories  erected  in  Japan  in  1908  produce  annually  500,000  kilos,  300,000  kilos 
for  exportation,  and  the  rest  for  home  consumption,  this  being  previously  supplied  by 
importation  from  Germany  (five-sixths)  and  England  (one-sixth).  In  three  large  centres 
(Xeckaren,  Troisdorf,  and  Eilenburg),  Germany  produces  annually  about  5,500,000  kilos  of 
celluloid  of  the  value  of  £1,360,000. 


P.  CONDENSED  BENZENE  NUCLEI 
DIPHENYL  AND  ITS  DERIVATIVES 


DIPHENYL,  C6H5-C6H5,  or  <^  \  is  formed  by  treating 

an  ethereal  solution  of  bromobenzene  with  sodium  (Fittig),  by  the  trans- 
formation of  hydrazobenzene,  or  by  diazotising  benzidine  and  decomposing 
the  resultant  product.  It  can  also  be  obtained  by  passing  benzene  vapour 
through  a  red-hot  tube. 

It  forms  colourless  crystals  melting  at  71°  and  boiling  at  254°,  and  is  soluble 
in  alcohol  and  in  ether.  On  oxidation  with  chromic  acid,  it  gives  benzoic 
acid,  its  constitution  being  thus  confirmed. 

Of  monosubstituted  products  of  diphenyl,  three  isomerides  are  possible, 
corresponding  with  the  o-,  m-,  and  p-  positions  with  respect  to  the  carbon 
joined  to  the  second  nucleus.  Disubstituted  derivatives  exist  in  numerous 
isomeric  forms,  as  the  substitution  may  occur  in  only  one  nucleus  or  in  both  ; 
in  general,  however,  the  substituents  enter  preferably  the  para-positions. 

BENZIDINE  (p  :  p-Diaminodiphenyl),  NH2-C6H4-C6H4'NH2.  Nitration 
of  diphenyl  yields  p  :  p-dinitrodiphenyl,  which,  when  reduced  with  zinc  dust 
in  alkaline  solution,  gives  benzidine.  The  latter  may  also  be  obtained  by 
electrolysis  of  nitrobenzene  ;  see  also  Ger.  Pat.  122,046,  according  to  which 
azobenzene  is  electrolysed  in  hydrochloric  acid  solution  in  presence  of  stannous 
chloride. 

When  pure,  benzidine  forms  colourless  scales  melting  at  122°  and  then 
subliming.  It  dissolves  slightly  in  cold  water,  but  readily  in  hot  water,  ether, 
or  alcohol.  It  is  a  diacid  base  and  gives  a  sulphate,  C]2H8(NH2)2,H2S04, 
almost  insoluble  in  water. 

It  is  largely  used  in  making  substantive  dyestuffs  (such  as  Congo  red  and 
chrysamine,  which  dye  cotton  without  mordants),  being  first  diazotised  and  then 
combined  with  naphthylamine  or  naphthalenesulphonic  acids. 

Crude  benzidine  costs  about  5s.  per  kilo  and  the  pure  product  48s.  The 
crude  sulphate  in  paste  (63  per  cent.)  costs  2s.  per  kilo  and  the  pure  36s. 

A  higher  homologue  of  benzidine  is  o-Tolidine,  C12H6(CH3)2(NH2)2,  which 
melts  at  128°,  and  the  diazo-compound  of  which  combines  with  naphthionic 
acid  to  form  a  red  substantive  dyestuff,  benzopurpurin  45.  The  dimethoxy- 
compound,  (O'CH3)2,  of  tolidine  is  dianisidine,  which  with  a-naphthol-a- 
sulphonic  acid  forms  benzoazurin  G  (substantive  blue). 
CeH4\ 

CARBAZOLE,   |  NH,   is  found  in  coal-tar,   and    can  be  obtained 


606  ORGANIC    CHEMIST  RjY 

synthetically  by  distilling  o-aminodiphenyl  over  red-hot  lime  or  by  gently 
heating  diphenylamine  vapour. 

The  unions  of  the  nitrogen  with  the  two  phenyl  groups  are  in  the  diortho- 
positions, 


so  that  carbazole  may  be  regarded  as  a  pyrrole  derivative  (see  later).  It 
forms  colourless  scales  melting  at  238°  and  readily  subliming,  and  it  dissolves 
in  concentrated  sulphuric  acid,  giving  a  yellow  coloration. 

From  diphenyl  can  be  derived :  four  isomeric  Dihydroxydiphenyls, 
C12H8(OH)2;  the  Diphenylsulphonic  Acids  ;  Diphenyl  Oxide,  (.C6H4)20  ;  Hexa- 
hydroxydiphenyl,  C12H8(OH)6  (the  mother-substance  of  caerulignone) ;  and 
the  Diphenylcarboxylic  Acids  (the  di-p-acid  is  a  white  powder,  insoluble  in 
water,  alcohol  or  ether ;  the  di-o-acid  is  Diphenic  Acid,  CO2H  •  C6H4  •  C6H4  •  CO2H, 
m.pt.  229°)  which  give  diphenyl  when  heated  with  lime. 

2.   DIPHENYLMETHANE   AND   ITS  DERIVATIVES 

These  compounds  may  be  obtained  by  condensing  either  2  mols.  of  benzene 
(or  its  homologues)  with  one  of  methylene  chloride,  or  1  mol.  of  benzyl  chloride 
(or  benzoyl  chloride)  with  one  of  benzene  (or  its  homologues  or  derivatives) 
in  presence  of  aluminium  chloride  : 

2C6H6  +  CH2C12  -  2HCI+  C6H5-CH2-C6Hd 
CgHg  -j-  CgH5'CH2'Cl  =  HC1  -f-  GgHij'  GH2-  C6H5. 

Condensation  of  2  mols.  of  benzene  with  aldehydes  (Baeyer)  or  1  mol.  of 
an  aromatic  aldehyde  with  one  of  benzene  (V.  Meyer)  under  the  influence  of 
concentrated  sulphuric  acid  (ketones,  phenols,  tertiary  anilines,  &c.,  also  act 
similarly)  : 

2C6H6  +  CHg-CHO  =  HaO  +  CH3-CH(C6H5)2 
^6^6  +  C6H5-CH2-OH  =  H20  +  C6H5-CH2-C6H5. 

DIPHENYLMETHANE,  C6H5-CH2-C6H5,  forms  white  crystals  melting  at 
26°  and  boiling  at  262°,  has  a  smell  of  oranges  and  is  soluble  in  alcohol  or  in 
ether.  It  is  obtained  synthetically  (see  above).  With  water  at  150°,  its  bromo- 
derivative,  CHBr(C6H5)2,  is  converted  into  Benzhydrol  (diphenylcarbinol), 
(C6H5)2CH-OH,  which  is  also  obtained  on  reducing  benzophenone. 

p-Diaminodiphenylmethane,  CH2(C6H4-NH2)2,  and  Tetramethyldiamino- 
benzhydrol,  OH-CH[C6H4-N(CH3),]2,  are  used  in  the  preparation  of  dyestuffs. 

BENZOPHENONE  (Diphenylketone),  C6H5-CO-C6H5  (see  p.  572). 

o-DIHYDROXYBENZOPHENONE,  [C6H4(OH)]2CO,  by  the  elimination  of  a  molecule 

CO 
of  water  from  the  two  hydroxyls,  gives  Xanthone,   C6H4<^  ~  ^>C6H4.      p-Dihydroxy- 

benzophenone  is  obtained  from  anisaldehyde,  so  that  the  hydroxyl  groups  must  be  in 
the  para -posit  ions.  Trihydroxybenzophenone  is  formed  by  the  condensation  of  benzoic 
acid  with  pyrogallol  in  presence  of  zinc  chloride.  It  is  used  in  dyeing  under  the  name 
alizarin  yellow  C  (see  Dyestuffs). 

Other  higher  derivatives  of  diphenylmethane  are  ass  follow : 

as-DIPHENYLETHANE  (see  later  symm.dibenzyl)  is  liquid  and  is  formed  from 
paraldehyde  and  benzene  (see  above).  Benzilic  Acid  (diphenylgly  collie  acid), 
(C6H6)2C(OH)-CO2H,  is  a  solid  and  is  obtained  by  the  action  of  KOH  on  benzil ;  by 
reduction  with  HI  it  gives  Diphenylacetic  Acid,  (C6H5)2CH'CO2H. 

Tolylphenylmethane,  C6H5-CH2-C8H4'CH3,  exists  in  several  isomeric  forms. 


TRIPHENYLMETHANE  607 

Tolyl  Phenyl  Ketones,  C6H6-COC6H4-CH3.  The  stereoisomeric  oximes  of  these 
ketones  were  employed  by  Hantzsch  in  developing  the  stereochemistry  of  nitrogen 
(see  pp.  20,  210,  and  306). 

Benzoylbenzoic  Acids,  C6H5-CO-C6H4-COoH :  the  ortho-acid  gives  anthraquinone 
when  heated  at  180°  with  P205. 

C6H4-. 

FLUORENE   (Diphenylenemethane),   |         /CH2,    is   found    in    coal-tar,    and    is 

C6H4/ 

formed    on   heating   diphenylmethane   vapour.     It   melts  at    113°,  boils  at   295°,   and 
forms  scales  showing  a  violet  fluorescence. 

3.   TRIPHENYLMETHANE  AND  ITS  DERIVATIVES 

These  are  prepared  synthetically  by  processes  analogous  to  those  used  for 
diphenyl methane,  but  under  such  conditions  as  to  lead  to  the  condensation  of 
three  benzene  nuclei  in  the  methane  molecule.  The  action  of  chloroform  on 
benzene  in  presence  of  A1C13  gives  TRIPHENYLMETHANE  (m.pt.  93°; 
b.pt.  359°)  : 

CHC13  +  3C6H6  =  3HC1  +  CH(C6H5)3. 

The  condensation  of  benzaldehyde  and  dimethylaniline  yields  Tetramethyl- 
diaminotriphenylmethane,  C6H5-CH[C6H4-N(CH3)2]2,  which  is  a  leuco-base 
(see  Dyestuffs)  of  malachite  green  ;  phenols,  &c.,  condense  similarly.  When 
this  colourless  leuco-base  is  oxidised  with  Pb02  and  HC1,  it  gives  Tetramethyl- 
diaminotriphenylcarbinol,  C6H5  •  C(OH)  [C6H4N(CH3)2]2  which  is  also  a  colour- 
less base  and  forms  colourless  salts.  When,  however,  these  salts  are  heated 
in  solution,  they  lose  water  and  form  an  intense  green  colour  ing -matter,  the 
double  salt  of  this  with  zinc  chloride  or  oxalate  being  known  as  malachite  green  : 

/C6H4  •  N(CH3)2,HC1  /C6H4  •  N(CH3)2,HC1 

C6H5-C< -C6H4-N(CH3)2,HC1  H20  +  C6H5-C/ /         \_N(CH  } 


/ 

or      C6H5-C<^  ; 

C6H4-NC1(CH3)2 


on  reduction,  the  colouring-matter  (+  2H)  gives  the  leuco-base  again. 

PARAROSANILINE  is  obtained  by  oxidising  1  grm.-mol.  of  p-toluidine 
and  2  grm.-mols.  of  aniline  with  arsenic  acid  or  nitrobenzene.  The  methyl 
of  the  toluidine  furnishes  the  carbon  atom  for  the  methane  nucleus  : 


CH3-C6H4-NH2  +  2C6H5-NH2  +  30  =  2H20  +  OH-C^-C6H4-NH2  (base). 

XC6H4-NH2 

With  acids,  this  base  gives  a  red  colouring-  matter  which  is  precipitated  by 
alkali.  When  reduced  with  zinc  and  hydrochloric  acid  it  yields  paraleucaniline, 
HC(C6H4-NH2)3,  in  colourless  crystals  which  give  the  coloured  base  again  on 
oxidation. 

Elimination  of  the  amino-groups  by  diazotisation  leads  to  triphenylmethane, 
while  nitration  of  the  latter,  followed  by  reduction,  gives  paraleucaniline, 
which  yields  triaminotriphenylcarbinol  on  oxidation.  When  treated  with  acids 
the  latter  loses  H20,  giving  the  colouring-matter  : 

.(C6H4-NH2)2  X(C6H4-NH2)2 

OH-Cf  =     H20  +  CClf 

XC6H«  •  NH2,HC1  XC6H4  •  NHa 


608  ORGANIC    CHEMISTRY 

ROSANILINE  is  formed  by  oxidising  a  mixture  of  o-  and  p-toluidines 
and  aniline  with  arsenious  anhydride,  mercuric  nitrate,  or  nitrobenzene,  the 
carbon  of  the  methane  nucleus  being  furnished  in  this  case  also  by  the 
p-toluidine  : 

CH  CTT 

C6H/      3  (p)    +    C6H/      3  (o)     +  C6H5-NH2  +   30  = 
XNH2  XNH2 


2H20    +    OH-OV 

X(C6H4-NH2)2 

Rosaniline  hydrochloride  (with  1  HC1)  or  fuchsine  forms  crystals  with  a 
green  metallic  lustre,  while  the  aqueous  solution  is  red  owing  to  the  presence 
of  the  monovalent  cation,  C19H18N3,  the  salt  being  almost  completely 
ionised. 

All  fuchsine  salts,  at  the  same  dilution,  give  the  same  absorption  spectrum, 
as  they  contain  the  same  cation. 

If  3HC1  are  combined,  the  salts  become  yellow  (yellow  trivalent  cation)  ; 
indeed,  with  excess  of  HC1  fuchsine  is  almost  decolorised,  although  in  dilute 
solution  the  red  cation  is  again  formed  by  dissociation.1 

Replacement  of  the  hydrogen  atoms  of  the  amino-groups  by  alkyl  groups 
gives  various  colouring-matters,  the  intensity  of  the  violet  colour  increasing 
with  the  number  of  methyl  groups. 

Pentamethylpararosaniline  is  the  methyl  violet  of  commerce. 

ROSOLIC  ACID  and  AURIN  are  the  phenolic  compounds  corresponding 
with  rosaniline  and  pararosaniline,  from  the  diazo -compounds  of  which  they 
are  obtained  by  boiling  with  water  : 

f!H  ff!  H  -OH^ 

V^iJ.  q  Sf\\J  Ci±±.  A        \J  J--L  /O 

^C  F~  •  0  ^XC  H    •  0 

Rosolic  acid  Aurin 

They  are  colouring-matters  of  an  acid  character  and  of  but  little  importance 
and  they  form  dark  red  prisms  with  a  greenish,  metallic  reflection. 

PHTHALOPHENONE,     C^-C6H5         ,  may   be   regarded   as   a   deriva- 


0 


tive  of  phthalic  acid  (see  p.  580)  or  of  tripheny] methane. 

It  is  the  anhydride  of  triphenylcarbinol-o-carboxylic  acid,  C(OH)(C6H5)2 
(C6H4-C02H),  and  is  obtained  by  heating  phthalyl  chloride  with  benzene  in 
presence  of  aluminium  chloride.  It  forms  scales  melting  at  115°  and  dissolves 
in  alkali  giving  a  salt  of  the  acid,  the  latter  not  being  obtainable  in  the  free 
state.  Its  phenolic  derivatives  are  the  phthaleins  (see  p.  581). 

HEXAPHENYLETHANE,  (C6H5)3C.C(C6H5)3,  is  of  some  interest  theoreti- 
cally, as  its  molecule  was  at  first  regarded  as  C(C6H5)3(Triphenylmethyl)  and  was 

1  It  is  commonly  thought  that  in  the  hydrochloride  the  chlorine  is  joined  to  the  amiuo-group  and  not  to  the 
carbon  of  the  methane,  since,  as  Tortelli  showed  (1895),  all  the  chlorine  is  precipitable  by  silver  nitrate  ;  the  com- 
pound is  hence  a  salt  and  not  an  ether.  It  cannot,  however,  be  denied  that  there  are  compounds,  such  as  triphenyl- 
methyl  chloride,  (C6H6)3C  •  Cl,  which  behave  similarly,  being  hydrolysable  by  water  and  then  completely  precipitable 
by  silver  nitrate.  Then,  too,  methyl  iodide  is  hydrolysed  by  water  alone  to  the  extent  of  0-6  per  cent,  in  forty-three 
hours,  whilst  in  the  presence  of  silver  nitrate  96  per  cent,  of  the  iodide  is  hydrolysed  in  the  same  time.  It  is  hence 
more  accurate  to  state  that,  alter  hydrolysis,  these  ethereal  compounds  behave  like  salts. 

Kosenstiehl  maintains  that  every  double  decomposition  between  salts  (especially  organic)  is  preceded  by 
hydrolysis,  and  those  salts  and  ethereal  compounds  which  hydrolyse  slowly  he  calls  bradolytes,  and  those  which 
hydrolyse  rapidly,  stenolytes. 


DIBENZYL,ETC.  609 

looked  upon  as  the  first  example  of  an  organic  compound  containing  trivalent 
carbon.  But  cryoscopic  examination  shows  that  it  has  the  doubled  molecular 
weight,  and  hence  indicates  the  constitution  (C6H5)3C-C(C6H5)3.  It  was 
prepared  by  Gomberg  by  the  action  of  zinc  on  triphenylchloromethane,  and  is 
a  solid,  stable  substance  which,  in  solution,  has  a  yellow  colour  and  becomes 
unstable  owing  to  its  great  power  of  reacting  ;  with  the  oxygen  of  the  air  it 
forms  a  peroxide,  (C6H5)3-OO  'OC^CeH^g.  On  account  of  the  facility  with 
which  it  forms  additive  products,  hexaphenylethane  is  regarded  by  some  as 
having  in  solution  the  constitution  : 

H   H 


(C6H5)2  :  C  :  C 


I      I 
H  H 


An  analogous  compound  is  Pentaphenylethane,  (C6H5)3C  •  CH(C6H5)2,  stable 
at  the  ordinary  temperature  but  not  in  the  hot. 

4.  DIBENZYL  AND  ITS  DERIVATIVES 

The  constitution  of  these  compounds  is  shown  by  their  methods  of  synthesis 
and  by  the  fact  that  they  all  yield  benzoic  acid  on  oxidation. 

DIBENZYL  (symm.  Diphenylethane),  C6H5-CH2-CH2-C6H5,  is  obtained 
from  benzyl  chloride  and  sodium  : 

2C6H5-CH2-C1  +  Na2  ==  2NaCl  +  C6H5-CH2-CH2-C6H5  ; 
it  melts  at  52°. 

STILBENE  (symm.  Diphenylethylene),  C6H5-CH  :  CH-C6H5,  melts  at  125°,  and  is 
obtained  from  benzal  chloride  (benzylidene  chloride)  and  sodium.  Owing  to  its  double 
linking,  it  can  unite  with  two  atoms  of  Br,  which  can  be  eliminated  as  HBr  by  treatment 
with  alcoholic  potash,  the  resulting  product  being  TOLANE  (Diphenylacetylene), 
CfiHg-C  :  C-C6H5,  melting  at  60°,  and  behaving  like  an  acetylene  derivative. 

p-DIAMINOSTILBENE,  NH2-C6H4-CH  :  CH-C6H4-NH2,  is  used,  especially  in  the 
form  of  the  corresponding  sulphonic  acids,  for  the  preparation  of  various  substantive 
dyestuffs. 

BENZOIN,  C6H5-CH(OH)-CO-C6H5,  is  formed  by  oxidising  HYDROBENZOIN, 
C6H5-CH(OH)-CH(OH)-C6H5,  which  is  obtained  by  treating  benzaldehyde  with  sodium 
amalgam.  Benzoin  exists  in  two  stereoisomeric  modifications,  melting  at  138°  and  119°. 
It  reduces  Fehling's  solution  even  in  the  cold  (giving  benzil)  and  forms  a  phenylosazone, 
since  it  contains,  like  the  sugars,  the  group  •CO-CH(OH). 

BENZIL,  C6H5-CO-CO-C6H5,  is  a  yellow  diketone  and  forms  three  benzildioximes  (see 
pp.  22,  210,  and  572)  : 

C6H5-C  ---  OC6H5     C6H5-C  ---  OC6H5        C6H5-C—     --  OC6H6 

II  II  II  II  II  II 

N-OH   N-OH          OH-N  N-OH  N-OH  OH-N 

Amphi-benzildioxime  Anti-benziUioxime  Syn-benzildioxime 

When  heated  with  alcoholic  potash,  benzil  combines  with  H2O,  giving  benzylic  acid  : 

CH-CO-CO-C6H5  +  H-OH  =  (C6H 


DESOXYBENZOIN,  C6H5-CH2-CO-C6H5,  is  obtained  from  phenylacetyl  chloride, 
C6H5-CH2-CO-C1,  and  benzene  in  presence  of  aluminium  chloride,  and  also  from  benzoin 
and  benzil.     It  melts  at  55°  and  gives  dibenzil  when  reduced  with  hydriodic  acid. 
ii  39 


610 


ORGANIC    CHEMISTRY 


HEXABENZYLETHANE,  (C6H6-CH2)3C-C(CH2-C6H6)3,  was  prepared  by  F.  Schmerda 
(1909)  by  heating  tribenzylcarbinol  with  hydriodic  acid  in  a  sealed  tube  at  200°,  the  product 
being  shaken  with  bisulphite,  extracted  with  ether  and  the  latter  distilled  off.  It  forms  a 
yellowish  crystalline  mass  which  is  recrystallised  from  acetone  and  glacial  acetic  acid  ; 
it  melts  at  80°  to  81°.  From  the  mother-liquor  dibenzyl  is  obtained. 


5.  NAPHTHALENE  AND  ITS  DERIVATIVES 

NAPHTHALENE,  C10H8,  occurs  in  abundance  in  crude  illuminating  gas  and  in  coal- 
tar.  When  the  latter  is  distilled  (see  p.  526  et  seq.),  the  naphthalene  is  obtained  from  the 
portions  distilling  between  170°  and  230°  and  by  redistilling  the  residues  of  the  oils  from 
which  the  carbolic  acid  has  been  extracted  with  caustic  soda,  care  being  taken  to  surround 
the  condenser  coils  with  hot  water  to  prevent  stoppages. 

The  first  separation  of  the  naphthalene  from  the  crude  oils  yielded  at  various  stages 
of  the  distillation  is  effected  by  cooling  in  large  tanks,  crystallised  naphthalene  separating 
out. 

The  oily  impurities  of  the  crystals  are  removed  in  a  hydraulic  press  with  heated  plates. 

Attempts  have  been  made 
to  centrifuge  the  crude 
naphthalene,  but  even 
when  this  is  steamed  in 
the  centrifuge,  the  resi- 
dual product  is  always 
very  impure  and  unsuit- 
able for  distillation  or 
sublimation.  In  conse- 
quence of  this,  use  has 
been  made  of  hydraulic 
presses  with  horizontal 
rods  and  vertical  plates 
FIG.  419.  heated  by  steam,  but 

these      give      insufficient 

pressure  and  too  much  waste,  and  require  too  much  time  and  attention.  The  best  results 
are  given  by  presses  with  vertical  columns  and  ring  plates  (similar  to  the  presses  described 
on  p.  392),  which  work  continuously  and  readily  attain  a  pressure  of  102  kilos  per  square 
centimetre  with  a  diminished  consumption  of  steam.  Nowadays  hydraulic  presses  with 
perforated  steel  bells  are  used — similar  to  those  xised  for  oily  seeds — and  in  10  hours 
each  of  these  can  effect  30  compressions  of  100  kilos  ;  when  several  presses  are  worked, 
hydraulic  accumulators  (see  p.  393)  are  used.  If  well  pressed,  naphthalene  has  the  mean 
solidifying  point  78-6°  and  95-5  per  cent,  of  it  distils  between  216-5°  and  218-5°.  Attempts 
have  been  made  to  purify  naphthalene  with  a  solution  of  resin  soap,  but  such  a  method  is 
too  expensive  (a  centrifuged  naphthalene  containing  7  per  cent,  of  oil  gives,  with  5  per  cent, 
of  colophony  and  the  corresponding  quantity  of  caustic  alkali  solution,  85  per  cent,  of 
pure  naphthalene  with  the  solidifying  point  78-8°).  The  compressed  naphthalene  is  purified 
further  in  metal  vessels  with  conical  bases  and  fitted  with  stirrers  (sometimes  with  air- 
jets).  In  these  the  molten  naphthalene  is  agitated  for  15  minutes  with  5  per  cent,  of 
sulphuric  acid  of  50°  Be  (already  used  once)  to  dry  the  mass  somewhat  and  free  it  from 
pyridine  compounds  ;  after  removal  of  this  acid,  the  mass  is  shaken  successively  with 
5  to  6  per  cent,  of  sulphuric  acid  of  60°  Be.  for  30  minutes,  4  per  cent,  of  hot  water,  4  per 
cent,  of  caustic  soda  solution  of  19°  Be.  (already  used  once),  and,  finally,  2  per  cent,  of 
hot  water.  After  settling  and  removal  of  the  water  as  far  as  is  possible  by  decantation, 
the  naphthalene  is  distilled  in  large  stills  holding  100  to  150  quintals  and  furnished  with  a 
rectifying  column  2  to  3  metres  high.  Water  distils  over  first  and  then  pure  naphthalene, 
which  is  collected  in  metal  boxes,  allowed  to  crystallise  in  moulds  and  granulated  by 
means  of  a  crusher  ;  the  solidifying  point  is  then  70-7°,  while  97-5  per  cent,  distils  between 
216-6°  and  218°.  A  purer  product,  in  the  form  of  large,  shining  scales,  can  be  obtained  by 
sublimation  (instead  of  distillation)  in  an  open  vessel,  a  (Fig.  419),  having  an  area  of  2  to  3 
cu.  metres  and  covered  with  an  inclined  wooden  plane  leading  to  a  large  wooden  chamber, 
20  to  25  cu.  metres  in  capacity.  The  naphthalene  is  heated  by  a  pressure  steam-coil 


NAPHTHALENE 


Gil 


and  sublimes  and  condenses  in  the  large  chamber,  forming  on  the  walls  a  thick  layer  of 
shining,  white  scales  of  pure  naphthalene.  In  order  to  avoid  loss  and  to  obtain  continuous 
working,  the  naphthalene  is  introduced  into  long  cylindrical  boilers,  bricked  in  like  steam 
boilers  and  connected  with  a  large  wooden  chamber  (350  cU.  metres),  which  has  a  base 
fitted  with  conical  outlets  leading  to  sacks  for  catching  the  naphthalene  as  it  becomes 
detached  from  the  walls  (these  are  knocked  from  time  to  time).  In  this  way  70  kilos  of 
pure  naphthalene  are  obtained  per  12  hours  for  each  100  cu.  metres  of  capacity. 

Pure  naphthalene  forms  shining  scales  melting  at  79-6°  and  boiling  at  218°.  It  is 
insoluble  in  water,  but  dissolves  readily  in  boiling  alcohol  or  in  ether  j  it  volatilises  even 
at  the  ordinary  temperature  and  distils  readily  in  steam. 

Naphthalene  is  used  in  large  quantities  in  the  preparation  of  various 
dyestuffs  (eosin,  indigo,  Martius'  yellow,  tropseolin,  Biebrich  scarlet,  croceine 
scarlet,  &c.),  phthalic  acid,  lampblack,  varnishes,  and  cart-grease,  and  is 
employed  also  as  an  antiseptic  and  as  a  preventative  of  moth  in  clothes.  For 
some  time  it  has  been  mixed  with  camphor  in  order  to  render  celluloid  less 
inflammable  and  less  explosive. 

Crude  naphthalene  costs  11s.  to  12s.  per  quintal,  while  the  pure  white  scales  are  sold 
at  16s.,  pure  in  tapers  at  17s.  6d.,  and  chemically  pure  at  80s.  per  quintal.  In  1910  Italy 
imported  371  quintals  of  naphthalene,  of  the  value  of  £386  (in  1907,  42  quintals),  and 
exported  2214  quintals  (£2200) ;  the  production  in  Italy  was  8600  tons  (£71,880)  in  1908. 
In  1909  Germany  imported  77,445  and  exported  63,544  quintals. 

England  exported  3650  tons  of  naphthalene,  of  the  value  of  £28,110,  in  1911. 

Constitution  of  Naphthalene.  The  following  structural  formula  is  attributed  to 
naphthalene  : 

rl  rl 


H— C          C 

I  II 

H— C         C 


\ 
C— H 

C— H 


a 


H 


and  to  indicate  the  positions  occupied  by  groups  replacing  the  hydrogens  in  derivatives 
the  carbon  atoms  are  numbered  or  lettered  with  Greek  letters,  thus  : 


That  the  two  nuclei  are  united  by  means  of  two  carbon  atoms  in  the  ortho-position  is 
shown  by  the  fact  that  oxidation  of  naphthalene  in  such  a  way  as  to  destroy  one  of  the 
nuclei  results  in  the  formation  of  phthalic  acid,  which  is  known  to  contain  two  carboxyl 
groups  in  adjacent  positions. 

Further,  since  when  phenylisocrotonic  acid  is  heated,  a  naphthalene  derivative,  namely, 
a-naphthol,  results,  it  is  clear  that  the  second  nucleus  is  formed  by  the  elimination  of  a 
molecule  of  water  with  closure  of  the  chain  of  the  four  carbon  atoms  of  the  side-chain  of 
the  original  acid  and  two  ortho-carbon  atoms  in  the  benzene  nucleus  : 

CH      CH  CH     CH 

I  HC^/NCH 

H20  +     . 

TJp  llfvtr       ptr  Trri 

J  I  \_^A  >  V.CL      xVyJTLo  XX  V-'.j 


CH 


CO  -OH 


\/c\/°H 

CH^C-OH 


612  ORGANIC    CHEMISTRY 

That  there  are  two  condensed  benzene  nuclei  is  also  deduced  from  the  fact  that  oxidation 
of  a-nitronaphthalene  gives  nitrophthalic  acid,  the  benzene  nucleus  containing  the  nitro- 
group  being  preserved  and  the  other  destroyed.  If,  however,  the  nitro-group  is  first 
reduced  to  an  amino-group,  oxidation  results  in  the  destruction  of  the  nucleus  containing 
the  amino-group  and  in  the  preservation  of  the  other,  phthalic  acid,  which  undoubtedly 
contains  a  benzene  nucleus,  being  formed.  That  the  linkings  between  carbon  and  carbon 
are  different  in  the  two  nuclei  is  shown  by  the  addition  of  four  hydrogen  atoms  to  one  of 
the  nuclei,  which  probably  has  true  double  linkings,  while  the  other  nucleus  would  seem  to 
have  a  true  benzenic  character  with  centric  linkings  (Bamberger)  ;  further,  the  addition 
of  ozone  proves  with  certainty  the  presence  of  olefinic  double  linkings  (E.  Molinari,  1907)  : 


CH       CH 

C 


HC 


HC 


\ 


CH 


CH 


C 
CH       CH 


With  nitric  acid,  naphthalene  gives  a  nitro-derivative,  and  with  sulphuric  acid,  various 
sulphonic  acids.  The  hydroxy-derivatives  resemble  phenols  and  the  amino-derivatives 
are  capable  of  diazotisation. 

Hydronaphthalene  is  readily  formed  by  the  addition  of  nascent  hydrogen 
and  behaves  likes  hydrophenol,  i.e.  like  an  unsaturated  hydrocarbon  of  the 
aliphatic  series. 

The  isomerides  of  the  substitution  products  of  naphthalene  are  more 
numerous  than  in  the  case  of  benzene.  Thus,  there  are  two  isoineric  mono- 
substituted  derivatives,  the  a-compound  with  the  substituent  in  the  1-,  4-,  5-, 
or  8-position,  and  the  /3-compound  with  the  substituent  in  the  2-,  3-,  6-,  or 
7-position.  The  isomeric  disubstituted  compounds  with  two  similar  substituents 
are  ten  in  number,  while  with  two  different  substituting  groups  fourteen 
isomerides  are  possible,  and,  in  some  cases,  all  known. 

Compounds  with  substituents  in  the  1-  and  8-  or  the  4-  and  5-positions 
are  known  as  aa-  or  pen-compounds,  e.g.  Perinaphthalenedicarboxylic  Acid, 

>COOH 

,  which  readily  forms  an  anhydride  owing  to  the  proximity 
>COOH 

of  the  hydroxyls. 

The  number  of  isomerides  being  so  large,  it  is  sometimes  difficult  to  deter- 
mine the  constitution  of  any  derivative.  To  this  end  the  oxidation  products  are 
often  studied,  the  formation  of  phthalic  acid  indicating  that  all  the  substituents 
are  in  the  one  benzene  nucleus  destroyed  by  the  oxidation,  while  the  formation 
of  a  substituted  phthalic  acid  indicates  the  opposite  to  be  the  case. 

NITRON APHTH  ALENES,  Ci0H7  •  NO2.  Of  the  two  isomerides,  the  /3  is  of  no  industrial 
importance. 

a -NITRON  APHTH  ALENE  is  obtained  on  the  large  scale  by  nitrating  naphthalene 
(10  parts)  with  a  mixture  of  8  parts  of  nitric  acid  (sp.  gr.  1-49)  and  10  parts  of  sulphuric 
acid  (sp.  gr.  1-84),  the  temperature  being  kept  at  70°  for  six  hours.  The  supernatant 
acid  is  decanted  off  in  the  hot  and  the  fused  nitronaphthalene  washed  several  times  with  hot 
water  and  then  granulated  by  pouring  slowly  into  cold  water  with  vigorous  agitation. 

It  forms  a  yellow  crystalline  mass  which  melts  at  59°,  boils  at  304°,  and  in  the  molten 
condition  has  the  sp.  gr.  1-223  ;  it  is  insoluble  in  water  %ut  dissolves  readily  in  benzene, 
ether,  carbon  disulphide,  or  hot  alcohol. 

The  crude  commercial  product  costs  64s.  to  76s.  per  quintal  and  the  pure 
crystals  96s. 

It  is  used  in  the  manufacture  of  dyestuffs,  especially  for  making  n-naphthylamine 
and  thence  various  azo-derivatives  or  naphthol  derivatives.  It  is  also  employed  in  the 


NAPHTHALENE    DERIVATIVES  613 

treatment  of  oils.  When  it  is  stored  alone,  there  is  no  greater  danger  than  in  the  storage 
of  oil.  When  used  in  mixtures  not  excessively  hot,  it  presents  no  special  danger. 

With  reducing  agents,  ti-nitronaphthalene  gives  u-NAPHTHYLAMINE,  Ci0H7-NH2, 
and  this,  by  way  of  the  diazo-compound,  yields  u-naphthol,  identical  with  that  obtained 
from  phenylisocrotonic  acid.  ct-Naphthylamine  can  also  be  obtained  from  ci-naphthol 
by  means  of  ammonia  and  calcium  chloride,  or  ammonia  and  ammonium  sulphite.  Indus- 
trially it  is  obtained  by  the  various  processes  mentioned  above  for  aniline  :  usually  60  parts 
of  dry  u-nitronaphthalene  are  added  gradually  to  a  hot  mixture  of  80  parts  of  iron  turnings, 
4  parts  of  hydrochloric  acid,  and  a  little  water,  the  whole  being  mixed  and  kept  at  70°  for 
6  to  8  hours  ;  slaked  lime  (about  5  parts)  is  next  added  until  the  reaction  becomes  alkaline, 
the  naphthylamine  being  distilled  from  retorts  and  condensed  at  60°,  and  subsequently 
purified  by  rectification.  It  consists  of  pleasant -smelling,  white  crystals,  melting  at  50°, 
readily  subliming  and  boiling  at  300°.  With  oxidising  agents  it  gives  red  or  blue  colorations. 
The  isomerif;  /3-NAPHTHYLAMINE  is  obtained  by  heating  10  parts  of  /3-naphthol  with 
4  parts  of  caustic  soda  and  4  parts  of  ammonium  chloride  in  an  autoclave  at  160°  for 
60  to  70  hours  ;  the  unchanged  naphthol  is  removed  by  means  of  sodium  hydroxide 
solution  and  the  /3-naphthylamine  extracted  from  the  residue  by  hydrochloric  acid.  The 
preparation  with  ammonium  sulphite  (see  above)  gives  a  better  yield  owing  to  the  formation 
of  the  sulphuric  ether  of  /3-naphthol,  which  reacts  more  readily  with  ammonia.  It  forms 
shining,  odourless  scales  which  melt  at  112°,  boil  at  294°,  and  are  not  coloured  by  oxidising 
agents.  The  separation  of  a-  from  /3-naphthylamine  is  effected  by  solvents,  such  as 
xylene,  chlorobenzene,  &c.,  which  dissolve  both  isomerides  in  the  hot  and  deposit  almost 
all  of  the  a -compound  in  the  cold. 

The  commercial  a-derivative  costs  about  £8  per  quintal  and  the  /3-compound  three 
times  as  much.  Both  are  used  for  making  azo-dyestuffs. 

The  NAPHTHALENESULPHONIC  ACIDS  are  obtained  from  naphthalene  and  con- 
centrated sulphuric  acid.  They  form  deliquescent  crystals  and  when  fused  with  KOH 
give  the  naphthols  ;  the  a-sulphonic  acid  in  presence  of  sulphuric  acid  at  160°  is  converted 
into  the  /3-acid. 

a-  and  /3-NAPHTHOLS,  Ci0H7-OH,  are  found  in  coal-tar,  and  may  be  prepared  from 
the  sulphonic  acids  or  amines  (see  above).  They  form  shining  scales  with  a  phenolic  odour, 
and  dissolve  slightly  in  hot  water  and  more  readily  in  alcohol  or  ether.  a-Naphthol  melts 
at  95°  and  boils  at  282°  ;  /3-naphthol  melts  at  122°  and  boils  at  288°.  Their  hydroxyl 
groups  are  more  readily  substituted  than  those  of  the  phenols.  With  ferric  chloride, 
aqueous  a-naphthol  gives  a  violet  precipitate,  while  /3-naphthol  gives  a  green  coloration 

OTT 

and  precipitates  Dinaphthol,  C^oHe-cCV,    „    QTT 

The  two  naphthols  give  ethers,  e.g.  Neroline,  C^H^-O^IIg,  which  has  a  fruity  odour, 
Betol  or  Naphthosalol  (the  salicylic  ester  of  /3-naphthol),  C10H7-0-CO-C6H4-OH, 
melts  at  95°,  and  is  used  in  medicine  under  the  name  of  salol. 

NAPHTHIONIC  ACID  (l-Naphthylamine-4-sulphonic  Acid),  C10H6(NH2)(S03H),  or 
SOaH 

,  is  formed   by  sulphonating  a-naphthylamine,  and  is  used  for   preparing 

NH2 

Congo  red  and  other  dyes.  The  solutions  of  its  salts  have  an  intense  reddish  blue 
fluorescence. 

Of  the  a-  and  /3-naphthylaminesulphonic  acids,  13  isomerides  are  known. 

Eikonogen,  used  as  a  photographic  developer,  is  the  sodium  salt  of  o1-Amino-/3  - 
naphthol-/33-sulphonic  Acid. 


((-NAPHTHAQUINONE,  ,   is  obtained    in    yellow  crystals   melting  at 


0 

125°    by  oxidising   naphthalene    with    chromic    acid    in    boiling    acetic    acid    solution. 
From   its   constitution  those  of   other   substitution  products  of   naphthalene  can   be 


614 


ORGANIC    CHEMISTRY 


deduced,  since  when  the  substituent  groups  are  in  the  para-position,  oxidation  always 
leads  ultimately  to  a-naphthaquinone.     It  is  volatile  in  steam. 


/3-NAPHTHAQUINONE,  C10H6O2  or 


,  is  formed    by    the    oxidation   of 


0 


0 


1  :  2-aminonaphthol,    and    crystallises  in  reddish    yellow  leaflets    blackening    at    115° 
to  120°. 

The  following  compounds  are  also  known  :  Oxy-  and  Dioxynaphthaquinones  (naphtlta- 
zarinblack)  ;  a-  and  /3-Methylnaphthalenes,  C10H7-CH3  ;  Naphthoic  Acids,  C10H7-CO0H  ; 
HydroxynaphthoicAcids,C10H6(OH)(C02H);NaphthalicAcid,C10Hf)(CO2H)o;Dinaphtnyl, 


C10H7-C10H7;  Acenaphthene,  C10H6 


,  in  which  the  unions  with  the  ethylene  group 


are  in  the  ax-  and  appositions  (found  in  tar,  colourless,  melting  at  85°,  boiling  at  277°,  and 
giving  naphthalic  acid  on  oxidation). 


ADDITION  PRODUCTS  OF  NAPHTHALENE 

Naphthalene  gives  additive  products  more  readily  than  benzene  does,  those  containing 

four  atoms  of  chlorine  or  hydrogen  being  well  known.     It  has  been  shown  that  this  addition 

occurs  in  only  one  of  the  nuclei,  and  similar  behaviour  is  shown  on  oxidation.     Chlorine 

reacts  with  naphthalene  at  the  ordinary  temperature  and  forms  Naphthalene  Tetrachloride, 

H        HC1 


H 


H 


\ 


HC1 


HC1 


which  forms  colouiless  crystals  melting  at  181°  and  gives  phthalic 


H       HC1 

acid   on  oxidation,   and  Dichloronaphthalene,   C10H6C12,   when  treated  with   alcoholic 
potash. 

When  ^(3-naphthylamine  is  reduced  (Na  +  amyl  alcohol),  four  hydrogen  atoms  are 
added  to  the   nucleus  containing  the  amino-group,  giving   Tetrahydronaphthylamine, 
H      H2 


,  which  behaves  exactly  like  an  aliphatic  amine  and  does  not   form 


diazo-compounds  ;  it  is  oxidised  by  permanganate,  giving  o-Carboxyhydrocinnamic  Acid, 

/C-H2  *  C.H2  *  COjjH 

C6H4<^  .     o-Naphthylamine   also  gives    a    tetrahydro-derivative,    which 

\C02H 

behaves,  however,  as  an  aromatic  amine  and  can  be  diazotised  ;  on  oxidation  it  gives  Adipic 
CH2 


CH2  COOH 

Acid,    I  .  which  shows  that  the  four  hydrogen  atoms  are  added  to  the  benzene 

CH2  COOH 

CH2  H2 


nucleus  which  does  not  contain  the  amino-group  : 


11 


H. 


H 


H2   NH2 
INDENE,  C9H8,  may  be  regarded  as  formed  by  the  condensation  of  a  benzene  group 


ANTHRACENE  615 

CH 

/\ 

HC       C CH 

with  a  pentamethylene  group  :       )         ||          ||    .     It  is  a  yellow  oil  boiling  at  1 80°,  and  is 

HC       C        CH 


CH     CH2 

found  in  coal-tar  and  in  crude  pseudocumene  ;  it  has  an  odour  of  naphthalene  and  gives 
phthalic  acid  on  oxidation  and  Indrene,  C9H10>  on  reduction. 

6.  ANTHRACENE  GROUP 

a. 
CH 

^ 

ANTHRACENE,    C14H10,   or          K  .  ,  is  found  in 


coal-tar  to  the  extent  of  0-25  to  0-45  per  cent.  The  crude  anthracene  oil 
which  passes  over  at  a  high  temperature  (above  270°)  in  the  distillation  of  tar 
is  subjected  to  a  further  rectification  which  yields  a  50  per  cent,  anthracene. 
This  is  purified  by  distillation  from  iron  retorts  with  potassium  carbonate, 

C^H^x 

which  holds  back  the  large  amount  of  Carbazole,  |         /NH,  as  the  non-  volatile 

C6H4 

C6H4\ 

potassium  compound,  |         ^>NK.    The  distillate  then  contains  only  anthracene 

C6H4 

and  phenanthrene,  the  latter  being  removed  by  dissolving  it  in  carbon  disul- 
phide  or  a  mixture  of  this  solvent  with  concentrated  sulphuric  acid  (Ger.  Pat. 
164,508  and  Fr.  Pat.  349,337).  The  residual  anthracene  is  purified  by  crystalli- 
sation from  crude  benzene  (see  Treatment  of  Tar  described  on  p.  526  et  seq.). 
and  by  sublimation  with  superheated  steam. 

The  proposal  has  also  been  made  to  purify  crude  anthracene  (containing, 
say,  46  per  cent,  of  anthracene  and  13  per  cent,  of  carbazole)  with  hot  naphtha 
and  sulphuric  acid,  which  convert  all  the  basic  substances  into  salts  and 
dissolve  them,  the  anthracene  being  afterwards  separated  by  decantation. 
Evaporation  of  the  naphtha  gives  anthracene  of  about  84  per  cent,  strength 
and  this  gives  a  product  of  95  per  cent,  purity  on  crystallisation  from  benzene. 

It  forms  shining,  colourless  scales  with  a  blue  fluorescence,  and  melts  at 
216-5°  and  boils  at  351°  ;  it  dissolves  slightly  in  ether  or  alcohol,  but  is  readily 
soluble  in  hot  benzene.  Sunlight  gradually  converts  it  into  the  polymeric 
para-  Anthracene  (Cj  4H10)2.  With  picric  acid  it  forms  a  molecular  condensation 
product,  C14H10,C6H2(N02)3OH,  melting  at  138°.  By  reducing  agents,  anthra- 

CH 
cene  is  transformed  into  Hydroanthracene,  C6H4<<riTT2>.C6H4,   which  melts 

i  ^^2 

at  107°  and  is  readily  soluble  in  alcohol. 

It  is  used  for  the  manufacture  of  anthraquinone  and  alizarin. 

Crude  anthracene  oil  (green  grease)  is  sold  at  11s.  to  12s.  Qd.  per  quintal, 
crude  20  per  cent,  anthracene  at  Is.  6d.  per  kilo  and  the  purified  product  at 
6s.  to  8s.  per  kilo. 

Its  constitution  is  deduced  from  its  various  syntheses.  Anschiitz  obtained  it  from 
tetrabromoethane  and  benzene  in  presence  of  A1C13  : 

CHBr2  /CH\ 

2C6H6  +    |  =  4HBr  +  C6H4^  |     ))C6H4. 

CHBr2  ^CH/ 


616  ORGANIC    CHEMISTRY 

It  is  formed  also  when  o-tolyl  phenyl  ketone  ia  heated  with  zinc  dust : 


H20  +  C6H4< 


SCH' 


>C6H4  ; 


this  synthesis  establishes  the  ortho-position  of  the  connections  between  the  two  nuclei 
and  also  the  presence  of  the  CH-CH  group.  Confirmatory  evidence  is  obtained  from  the 
following  synthesis : 


4Na  =  4NaBr 


Br 

H 
CH2Br 

o-Bromobenzyl  bromide 

which,  on  oxidation,  loses  2H  and  gives  anthracene. 

Phthalic  anhydride,  when  heated  with  benzene  and  A1C13,  gives  o-benzoylbenzoic  acid, 
from  which  PC16  eliminates  water  with  formation  of  anthraquinone,  the  latter  giving 
anthracene  when  reduced  with  zinc  dust  in  the  hot : 


,CO-CfiHfi 


S\) 


anthracene. 


Centric  linkings  do  not  seem  to  be  present  in  the  nuclei  of  anthracene,  which  readily 
combine  with  ozone  (E.  Molinari,  1907),  this  property  being  characteristic  of  olefine 
double  linkings  (see  p.  88). 


SUBSTITUTION  PRODUCTS  OF  ANTHRACENE 

The  possible  isomerides  are  here  very  numerous,  but  only  few  of  them  have 
yet  been  prepared.  Three  monosubstituted  isomerides  are  possible,  as  is  seen 
from  the  constitutional  formula  (see  above).  The  constitution  of  the  isomerides 
is  ascertained  from  a  study  of  the  oxidation  products  and  of  the  methods  of 
synthesis.  When  the  substituents  are  in  the  yx  or  y2  position,  oxidation  gives 
anthraquinone.1  CO 


ANTHRAQUINONE,  C14H802,  or 


,  is   obtained  very 


easily  by  oxidising  anthracene  with  dichromate  and  dilute  sulphuric  acid  in 


1  Of  the  many  Derivatives  of  Anthracene,  the  following  may  be  mentioned  :  anthraccnecarboxylic  aciiis 
(«,  ft,  and  y)  ;  chlorobromoanthracenes,  which  contain  the  halogens  in  the  y-positions,  as  they  form  anthraquinone 
on  oxidation  ;  niiro-  and  dinitro-anthracenes  (y)  ;  p-anthramine,  C14H8-NH2,  obtained  from  /3-anthrol  and  NH,  ; 


anthrols  (a  and 


CH 


CH 
_CH2 


;  anthrone,  C,H4<C 


CH2 


CO 


y-anthranol,  C,H4<J 

C(OH) 
<^  | 

C(OH) 


CH 


C(OH) 
4  (three  isomerides  : 


_ 
y-hydroanthranol,  C,H4<^  ^>C,H4  ;   the  anthrahydroquinones,  C 

CH(OH) 

chrysazol,  rufol,  and  flavol)  ;  anthracenegtdphonic  and  disulphonic  acids  ;  unthraquinonesulpJionic  acids  ;  hydroxy- 
anthraquinones,  C14H,O2-OH;  quinizarin  (a,  ;  aa-dihydroxyanthraquinone)  ;  purpuroxanthin  (al  :  ^,-dihydroxy- 
anthraquinone)  ;  C6H4(CO2)-C6H(OH)S  («  :  ft  :  a,)  is  purpurin  (the  isomeric  flavopurpurin,  anthrapurpurin, 
anthragallol,  &c.,  are  also  known)  ;  OH  •  C6H3  •  CO2  •  C6H3  •  OH  (anthraflavinic  and  isoanthraflavinic  acidt,  with  which 
correspond  anthrarufin,  chrysazin,  &c.)  ;  tetrahydroxyanthraquinones  (rufiopin,  anthrachrysone,  quinalizarin)  ; 
hexahydroxyanthraquinones  (rufigallic  acid,  &c.)  ;  methyl-  and  dimethyl-anthracenes,  C14H,-CHS  and  C14H8(CH3).,  ; 

CH2      s 
phenylanthracene,     C14H,-C,H,  ;      alkylanthrahydrides,     C,H4\         ^>C,H4  ;      phenylanthranol    (phthalidinf), 

CHR 

C(C.H§)  C(C.H.)(OH) 

f-«H4<^  |  ^>C,H4  ;   phenylhydroxyanthranol  (phthalideine),   C,H4<^  ^>C8H4  ;  anthraceneearb- 

C(OH)  ~CO~ 

_CH,_ 

oxylic  acids  (a,  /3,  y),  C14H,-COaH  ;     alkylhydroanthmnoU,  C,H4<^  ">C,H,,  &c. 

CR(OH) 


ALIZARIN  617 

the  hot,  or,  better,  with  nitric  acid,  which  does  not  give  nitro-derivatives.  It 
can  also  be  obtained  from  phthalic  anhydride  and  benzene  in  presence  of 
A1C13  (see  above)  or  by  electrolysing  anthracene  in  20  per  cent,  sulphuric  acid 
in  presence  of  cerium,  chromium,  or  manganese  salts  (Ger.  Pat.  152,063, 
and  Perkin,  1904). 

It  can  be  purified  by  crystallisation  from  nitrobenzene  or  aniline,  which 
dissolve  it  in  the  hot  but  not  in  the  cold.  It  gives  two  isomeric  monosubstituted 
derivatives. 

It  forms  yellowish  needles  melting  at  274°  and  boiling  at  about  360°,  and 
it  dissolves  in  concentrated  sulphuric  acid,  but  is  precipitated  unchanged  on 
dilution.  It  is  very  stable,  is  not  easily  oxidised  and  has  the  character  of  a 
diketone  rather  than  of  a  quinone.  It  is  not  readily  reduced,  is  only  slightly 
volatile  and  has  no  pungent  odour.  That  the  two  lateral  benzene  nuclei  have 
centric  linkings  and  not  olefinic  double  bonds  is  shown  by  the  fact  that,  unlike 
anthracene  (see  above),  anthraquinone  does  not  fix  ozone. 

When  fused  with  potash,  it  gives  benzoic  acid  and,  when  heated  with 

zinc  dust  and  NaOH,  Hydroxyanthranol,  06H4<  ^Q^>C6H4,  which  has 

a  blood-red  colour  in  alkaline  solution  and  is  oxidised  to  anthraquinone  in 
the  air.  Reduction  of  anthraquinone  with  Sn  and  HC1  gives  Anthranol, 

C(OH) 

C6H4^   [  ^>C6H4,  which  is  a  weak  phenol. 

XC(OH)X 

More  energetic  reduction,  such  as  distillation  over  zinc  dust,  yields  anthra- 
cene. The  Bohn-Schmidt  reaction  permits  of  the  introduction  of  sulphonic 
or  nitro-groups  into  the  non-substituted  or  the  substituted  nucleus  of  anthra- 
quinone derivatives,  according  as  the  reaction  occurs  in  presence  or  in  absence 
of  boric  acid,  a-  or  /3-Nitroderivatives  can  also  be  obtained,  at  will,  by  means 
of  the  same  reaction  (Ger.  Pat.  163,042  of  1905),  which  is  facilitated  by  the 
presence  of  mercury  salts. 

Commercial  anthraquinone  costs  about  6s.  per  kilo,  and  the  sublimed 
chemically  pure  product  28s. 

The  most  important  derivative  of  anthraquinone  is  the  1  :  2-dihydroxy- 
compound  or  alizarin.  CO  OH 

ALIZARIN  (Dihydroxyanthraquinone),  C14H8O4,  or 


CO 

was  at  one  time  obtained  exclusively  from  madder  roots  (Rubia  tinctorum),  from 
which  Ruberythric  Acid  (a  glucoside  of  the  formula  C26H28O14)  is  extracted ; 
this  is  separated  into  glucose  and  alizarin  by  boiling  with  dilute  sulphuric 
acid.  It  is  a  very  beautiful  red  colouring -matter  and  was  known  to  the  ancients. 
Since  1870,1  following  Grabe  and  Liebermann's  synthesis  (1869),  it  has  been 
prepared  only  artificially  in  the  following  manner  :  anthracene  is  converted 
by  oxidation  with  H2S04  and  Na2Cr207  into  crude  anthracene. 

This  is  then  heated  at  100°  with  concentrated  sulphuric  acid,  which  leaves  the  anthra- 
quinone unaltered,  while  it  converts  the  impurities  into  sulphonic  acids  soluble  in  water. 
The  anthraquinone  is  then  filtered  and  washed  and  heated  at  160°  with  fuming  sulphuric 
acid  (containing  50  per  cent,  of  free  S03),  which  converts  it  largely  into  the  monosulphonic 
acid.  The  latter  is  dissolved  in  water  and  filtered  to  separate  it  from  unaltered  anthra- 
quinone ;  neutralisation  of  the  solution  with  caustic  soda  results  in  the  deposition  of  the 
sodium  salt,  which  is  only  slightly  soluble  in  cold  water.  One  hundred  parts  of  this  salt  are 
mixed  with  25  parts  of  caustic  soda  and  12  to  14  parts  of  potassium  chlorate,  which  facilitates 

1  In  1868  Prance  produced  and  exported  madder  to  the  value  of  £1,720,000  and  £1,240,000  respectively.     The 
exportation  fell  to  £800,000  in  1871  and  to  £160,000  in  1876,  the  production  then  ceasing  entirely. 


618  ORGANIC    CHEMISTRY 

the  reaction  ;  the  mixture  is  dissolved  in  the  smallest  possible  amount  of  water  and  the 
liquid  heated  at  180°  for  2  days  in  an  autoclave  fitted  with  a  stirrer.  The  sulphonic  group 
is  thus  replaced  by  hydroxyl  (or  ONa),  and  at  the  same  time  a  second  OH  group  is  formed 
by  the  action  of  the  chlorate  : 

co  pn 

C6H4<£Q>C6H3-S03Na  +  3NaOH  +  O  =  Na2S03  +  2H20  +  C6H4<^>C6H2(ONa)2. 

Sodium  anthraquinone- 
monosulphonate 

The  fused  mass  is  run  into  water  and  acidified  with  sulphuric  acid,  the  colouring- matter 
(alizarin)  being  thus  liberated. 

According  to  Fr.  Pat.  333,144,  if  fuming  sulphuric  acid  acts  on  anthraquinone  in  presence 
of  mercury,  there  is  no  partial  formation  of  the  m-sulphonic  compound,  the  sulpho-group 
entering  exclusively  the  ortho-position  to  the  ketonic  group. 

Alizarin  may  also  be  prepared  (Ger.  Pat.  186,526)  without  sulphonation  by  treating, 
say,  300  kilos  of  a  mixture  of  NaOH  and  KOH  with  30  kilos  of  NaC103  (or  Na202,  BaO2, 
Pb02,  &c.)  dissolved  in  100  litres  of  water,  100  kilos  of  anthraquinone  being  then  added  and 
the  liquid  heated  at  200°  in  an  oil-bath  until  the  oxidising  agent  disappears.  After  this, 
the  mass  is  poured  into  water  through  which  air  is  then  passed  ;  the  alizarin  is  precipitated 
with  milk  of  lime,  the  precipitate  being  filtered  off  and  decomposed  with  HC1  and  the 
alizarin  purified  from  anthraquinone  residues  by  means  of  caustic  soda.  This  method 
yields  a  purer  product  than  other  processes. 

Alizarin  has  been  prepared  recently  by  passing  an  electric  current  through  a  mixture 
of  anthraquinone  and  fused  potash. 

Alizarin  sublimes  in  fine,  orange-red  needles,  melts  at  289°,  and  is  almost 
insoluble  in  water  and  slightly  soluble  in  alcohol ;  owing  to  its  phenolic  groups 
it  dissolves  in  alkali  and  also  forms  a  diacetyl-derivative.  When  distilled  with 
zinc  dust  it  forms  anthracene. 

With  metallic  oxides  it  forms  insoluble  lakes  of  various  colours,  and  on  this 
is  based  its  use  in  dyeing.  With  ferric  oxide  it  gives  a  bluish  black  colour 
and  with  lime  a  blue  lake  ;  the  lakes  of  tin  and  aluminium  are  red  (Turkey 
red). 

The  constitution  of  alizarin  is  shown  also  by  its  synthesis  from  phthalic 
anhydride  and  catechol  at  150°  in  presence  of  sulphuric  acid : 

CeH^QQ^O  +  C6H4<TQjj  /2\   =  H20  +  C6H4< 

Derivatives  of  anthraquinone  and  of  hydroxyanthraquinone,  especially  the 
amino-derivatives,  form  colouring-matters  only  when  the  two  hydroxy- groups 
are  in  the  ortho-position  to  one  another. 

C6H4-CH 

PHENANTHRENE,  C]4H10,  or    |  ||      ,  is  an  isomeride  of  anthracene, 

C6H4-CH 

with  which  it  occurs  in  tar.  When  pure,  it  forms  shining,  colourless  scales, 
soluble  in  ether,  less  so  in  alcohol  (with  blue  fluorescence)  and  only  slightly 
soluble  in  water  ;  it  melts  at  99°  and  boils  at  340°.  The  separation  of  phenan- 
threne  from  anthracene  is  described  above  (see  Anthracene).  Synthetically 
it  is  obtained  by  condensing  1  mol.  of  o-nitrobenzaldehyde  (or  its  higher 
homologues)  with  1  mol.  of  sodium  phenylacetate  in  presence  of  acetic 
anhydride  : 

C6H5-CH2-C02Na  +  N02-C6H4-CHO  =  H20  -f  N02-C6H4-CH 

II 
C6H5-OC02Na 

Sodium  a-phenyl-o-nitrocinnamate 

Reduction  and  diazotisation  eliminate  the  N02,  treatment  with  powdered 


HETEROCYCLIC    COMPOUNDS  619 

C6H4 — CH 

copper  then  gives  /3-Phenanthrenecarboxylic  Acid,     |  ||  ,    from 

C6H4— C-C02H 

which  COo  is  eliminated  in  the  ordinary  way  with  formation  of  phenanthrene. 

C6H4-CO 
When  oxidised  with  chromic  acid,  it  gives  first  Phenanthraquinone,  | 

C6H4-CO 
(yellow  crystals,  m.pt.  200°),  and  then  Diphenic  Acid,  C14H1004,  or 

C02H       C02H 


The  constitution  of  phenanthrene  is  established  by  its  syntheses  and  by 
its  oxidation  products.  The  double  linking  between  the  two  methinic  carbon 
atoms  is  not  shown  by  the  ordinary  reaction  with  permanganate  (Baeyer) 
(see  p.  88),  but  is  made  evident  by  the  reaction  with  ozone  (E.  Molinari,  1907  ; 
see  p.  88).  The  constitutional  formula  of  phenanthrene  may  be  represented 
thus  : 

CH   CH 
CH    C/J       '~\C    CH 


CH    CH  CH   CH 

and  it  may,  therefore,  be  regarded  as  formed  by  the  condensation  of  three 
benzene  nuclei. 

OTHER  CONDENSED  NUCLEI  OF  LESS  IMPORTANCE,  found  in  the  portions  of 
petroleum  and  tar  distilling  above  360°,  are  as  follow  : 

CH CH  ' /          N .  CeH4— CH 

r  EL/I         II  /         \ /         \  •  I          II     • 

^6    4\  \  /~~  ~~\  /  ' 

\C6H3— CH  (\oHe-CH 

\ / 

Fluoranthrene,  CUH10  Pyrene,  C,,H,0  Chrysene,  C,,H,, 

Ctr       r*ti 
3x14 — \jH 


||      ;  )C6H2-CH 

CioHe-CH  C3H7/ 

Picene,  Ca2H14  Betene,  CUTLU 

Retene  has  m.pt.  98°  and  b.pt.  394°  ;  Chrysene,  m.pt.  250°,  b.pt.  448°  ;  Picene, 
m.pt.  364°  ;  Fluoranthrene,  m.pt.  110°  and  b.pt.  250°  (60  mm.)  ;  Pyrene,  m.pt.  148°, 
b.pt.  260°  (60  mm.). 

Q.  HETEROCYCLIC  COMPOUNDS 

These  are  substances  containing  at  least  one  nucleus,  the  atoms  forming 
the  ring  being  of  more  than  one  kind,  i.e.  they  are  not  all  carbon  atoms  as  in 
the  homocyclic  compounds  as  yet  studied,  one  or  more  of  these  carbon  atoms 
being  replaced  by  nitrogen,  oxygen,  sulphur,  &c.  One  of  the  simplest  of  these 
heterocyclic  compounds  is  furfuran. 

1.  FURFURAN  (Furan),  C4H4O,  is  a  colourless  liquid  which  is  insoluble 
in  water,  smells  like  chloroform,  boils  at  32°,  and  is  found  among  the  first 
products  of  the  distillation  of  pine-tar.  With  metallic  sodium  it  does  not 
give  hydrogen,  so  that  the  oxygen  is  not  present  as  OH  ;  nor  is  it  in  the  form 
of  carbonyl  (CO),  since  furan  does  not  react  with  phenylhydrazine  or  hydroxyl- 
amine.  It  can  be  converted  into  ccerulinic  aldehyde,  while,  under  suitable 


620  ORGANIC    CHEMISTRY 

conditions,  succindi aldehyde  loses  H20  giving  furan.     These  reactions  indicate 
its  constitution  : 


CH2-CHO         CH  :  CHX 

|       =  H,0  +  |       )0 
CH2-CHO         CH  :  VW 


0 


Succindialdehyde  .  Furau 

A  shaving  of  pinewood  moistened  with  HC1  gives  a  green  coloration  with 
furan.  The  latter  reacts  with  HC1  forming  a  white  mass. 

FURFURAL  (a-Furol,  Furfuraldehyde),  C6H4O2,  is  obtained  readily  and  abundantly 
by  the  action  of  sulphuric  acid  on  pentoses,  pentosans,  and  woody  substances  (see  p.  429)  ; 
it  is  found  in  fusel  oil  and  in  clove  oil.  It  is  a  colourless  oil  of  aromatic  odour,  turning 
brown  in  the  air  and  boiling  at  162°  ;  it  is  soluble  in  alcohol  and,  to  a  less  extent,  in  water. 

CHO 


Its  aldehydic  properties  justify  the  constitution 


With  alcoholic  potash  it 


gives  a  corresponding  Furfuryl  Alcohol, 


CH3-OH  C02H 


,  and  Pyromucic  Acid, 


the  latter  melts  at  132°,  sublimes  readily,  dissolves  in  hot  water,  decolorises  alkaline 
permanganate  and  combines  with  4  atoms  of  bromine,  the  presence  of  two  true  olefinic 
double  linkings  being  thus  confirmed.  If  heated  in  a  sealed  tube  at  275°  it  gives  furfuran 
and  CO2.  With  aniline  and  HC1,  or  with  aniline  acetate  paper,  it  gives  a  characteristic 
intense  red  coloration  (see  p.  430). 

2.  THIOPHENE,  C4H4S,  occurs  in  tar  and  always  accompanies  benzene,  on  account 
of  their  similarity  in  boiling-point  (84°)  and  other  properties.     For  the  preparation  of 
benzene  free  from  thiophene,  see  p.  533. 

Thiophene  is  produced  on  a  large  scale,  but  in  small  yield,  by  passing  acetylene  or 
ethylene  through  boiling  sulphur,  or  by  passing  illuminating  gas  over  red-hot  pyrites. 
W.  Steinkopf  (1911)  obtains  an  increased  yield  by  passing  a  current  of  acetylene  over 
pyrites  contained  in  a  revolving  iron  drum  and  heated  to  300°  in  a  furnace,  the  exhausted 
pyrites  being  continually  discharged  and  fresh  pyrites  introduced.  The  condensed  liquid 
product  contains  40  per  cent,  of  thiophene,  which  can  be  extracted  by  fractional  distillation. 

One  of  the  syntheses  of  thiophene  consists  in  the  distillation  of  succiiiic  acid  in  presence 
of  phosphorus  sulphide,  hydrogen  and  hydrogen  sulphide  being  evolved  ;  this  synthesis 
confirms  the  constitution : 

ft       « 
H2OCO2H  HC=CHX 

|  — »•  |  >S    (Thiophene). 

H2OC02H  HC=CHX 

/3l       a1 

Thiophene  is  a  colourless  and  almost  odourless,  refractive  liquid,  boiling  at  84°,  and 
having  the  sp.  gr.  1-062  at  23°.  The  presence  of  the  double  linkings  is  confirmed  by  the 
quantitative  addition  of  ozone. 

Pure  thiophene,  prepared  synthetically,  costs  £18  per  kilo. 

CH  :  C(CH3K 

Dimethylthiophene  (thioxene),    \  /S,  is  obtained  by  the  interaction  of  the 

CH  :  C(CH3)/ 

enolic  form  of  acetonylacetone  and  phosphorus  pentasulphide,  and  1  :  4-diketones  in 
general  yield  higher  homologues  of  thiophene,  which,  when  oxidised,  give  carboxyl  groups 
in  place  of  the  side-chains. 

Thiophene  compounds,  such  as  halogen  and  nitro-derivatives,  sulphonic  acids,  &c., 
behave  very  similarly  to  those  of  benzene. 

With  isatin  and  concentrated  sulphuric  acid,  thiophene  gives  a  blue  coloration  (indo- 
phenin,  C^H^NCS). 

3.  PYRROLE,  C4H5N,  is  found  in  small  quantity  in  tar  and  in  larger  quantity  in 
Dippel  animal  oil  (bone  oil),  especially  in  the  fraction  distilling  at  about  130°,  which  is 
freed  from  pyridine  bases  by  saponifying  with  soda  and  washing  with  dilate  sulphuric 


621 

acid.  It  is  purified  by  converting  into  the  potassium  derivative,  C4H4NK  (by  the  action 
of  potassium),  which  is  washed  with  ether,  in  which  it  is  insoluble,  and  then  treated  with 
water,  the  pyrrole  being  thus  liberated. 

After  fractional  distillation,  it  is  obtained  as  a  light,  colourless  oil,  boiling  at  131°, 
and  possessing  a  faint  odour  of  chloroform.  It  readily  turns  brown  and  polymerises 
under  the  action  of  light.  With  isatin  and  sulphuric  acid  it  gives  the  blue  indophenin 
reaction  (see  above). 

A  reaction  characteristic  of  the  pyrroles  is  the  red  coloration  they  give  with  a  pine  shaving 
moistened  with  HC1. 

The  hydrogen  of  the  iminic  group  is  replaceable  by  metals,  acetyl,  and  alkyl 
groups. 

Pyrrole  now  forms  the  basis  of  a  number  of  important  compounds,  which  are  obtained 
by  various  syntheses  investigated  by  Ciamician  and  his  collaborators  during  the  past 
quarter  of  a  century. 

The  constitutional  formula  of  pyrrole  is  as  follows  : 

/3'HC CH/3 


Us      2||    - 
u'HC        CHrt 
i 


N 
H 

this  being  deduced  from  a  number  of  reactions  and  syntheses,  e.g.  the  formation  of  pyrrole 
by  the  action  of  ammonia  on  y-diketones  or  on  succinic  aldehyde,  with  intermediate 
formation  of  diammonaldehyde  : 

CH2-CHO  CH:CHv 

+  NH3  =  2H20  +    |  )sNH. 

CH2-CHO  CH-.CH./ 

This  pyridine  nucleus  occurs  frequently  in  nature,  in  combination  with  other  groups 
in  alkaloids  (nicotine,  &c.),  in  the  colouring-matter  of  the  blood  and  of  chlorophyll,  &c. 

CH2-CH:N-OH 
When   boiled   with  hydroxylamine,  pyrrole  gives  Succindialdoxime,   |  , 

CH2-CH:N-OH 
CH2-CHO 
which,  with  nitrous  acid,  gives  succinic  aldehyde,    I 

CH2«CHO 

CH2-COv 
Pyrrole  is  formed  by  the  distillation  of  succinimide,    |  /NH,     with    sodium 

CH2-CCK 

or  zinc  dust,  while  the  oxidation  of  pyrrole  with  chromic  acid  gives  maleimide, 
CH-C(X 

II  >H. 

CH-CCK 

Pyrrole  is  changed  by  acids  ;  with  HC1  in  the  hot,  it  polymerises  and  condenses 
to  a  red  mass  (pyrrole  red).  It  has  a  faint  acid  character,  but  gives  a  hydrochloride, 
(C4H5N)3,  HC1,  only  in  ethereal  solution. 

With  the  halogens  it  gives  not  additive  products  but  only,  like  benzene,  substituted 
derivatives.  Tetraiodopyrrole  (iodol)  is  obtained  from  pyrrole  by  the  action  of  an  alcoholic, 
alkaline  solution  of  iodine  ;  it  is  an  efficient  antiseptic  and  is  used  instead  of  iodoform, 
being  without  the  unpleasant  odour  of  the  latter.  It  melts  at  190°,  and  is  colourless  when 
freshly  prepared,  but  it  gradually  turns  brown  and  deposits  iodine. 

With  nitric  and  sulphuric  acids,  pyrrole  resinifies  ;  the  nitro-derivatives,  which  contain 
the  isonitro-group,  NOOH,  are  prepared  indirectly  (e.g.  with  alkyl  nitrate). 

Pyrrole  is  analogous  in  many  of  its  properties  with  the  substituted  phenols  and  anilines  ; 
thus,  a  methyl-  or  acetyl-group  united  to  the  nitrogen  (N-derivatives)  is  displaced,  on 
heating,  to  a  carbon  atom  (C-derivatives) : 


622  ORGANIC    CHEMISTRY 

HC— CH  HC— CH  HC— CH  HC— CH 

II      II  II      II  II       II  II      II 

HC     CH  HC     C-CH3  ;  HC     CH  HC     C-CO-CH3. 

\/       —        \X  \/       —         \/ 

N  NH  N  NH 

I  I 

CH3  CO-CH3 

Potassium  pyrrolate,  C4H4NK,  and  CO2  give  pyrrolecar  boxy  lie  acid,  C4H3(C02H)-NH 
(m.pt.  102°)  ;  this  loses  C02  and  gives  pyrrole  again  when  heated,  while  it  loses  water  and 

N CO 


forms  a   dimolecular  anhydride,    Pyrocoll, 


,    when    treated    with 


CO N 


acetic  anhydride. 

Like  the  substituted  phenols,  the  C-alkylpyrroles  give  pyrrolecarboxylic  acids  by  simple 
fusion  with  potash.  In  analogy  with  the  formation  of  nitrosophenols  from  phenols,  pyrrole, 
with  ethyl  nitrite  in  presence  of  sodium  alkoxide,  forms  Nitrosopyrrole,  which  exists  in 
tautomeric  modifications : 

HC— C  :  NOH  HC— CH 

II      II  II 

HC    CH  and  HC     C :  NOH. 

\/  V 

•     N  N 

By  means  of  chloroform  and  sodium  alkoxide,  another  atom  of  carbon  is  introduced 
into  the  nucleus,  a  pyridine  derivative  being  formed. 

Hydrogenated  derivatives  of  pyrrole  are  formed  more  easily  than  those  of  benzene,  and, 
like  the  latter,  do  not  show  purely  aromatic  properties.  When  pyrrole  is  reduced  by  means 
of  zinc  and  hot  acetic  or  cold  hydrochloric  acid,  it  yields  Dihydropyrrole  (or  pyrroline, 
m.pt.  91°),  which,  with  HI  and  P,  gives  Tetrahydropyrrole  (or  pyrrolidine,  b.pt.  87°), 
H2 H2 


H 


H2  ;  the  latter,  together  with  N-methylpyrroline,  are  the  simplest  cyclic  alkaloids 


NH 


known  and  are  found  in  tobacco.     Pyrrolidine  is  found  in  carrot  seeds  and  a  C-methyl- 
pyrroline  in  pepper. 

When  proteins  are  decomposed  by  means  of  trypsin  or  hydrochloric  acid,  the  amino- 
acids  formed  are  accompanied  by  laevo-rotatory  a-Pyrrolidinecarboxylic  Acid.  Among  the 
products  formed  by  the  degradation  of  egg  albumin  by  baryta  is  a'-pyrrolidone-o  -carboxylic 


Acid,     OC      CH-CO2H,  which  is  also  known  as  pyroglutamic  acid  ;  it  melts  at  183°,  has 


NH 

a  neutral  reaction  and,  when  heated,  loses  C02  and  H20,  forming  pyrrole. 

PYRAZOLE,  C3H4N2,  is  a  heterocyclic  compound  with  two  nitrogen  atoms  in  the 
ortho-positions.  It  can,  indeed,  be  obtained  by  the  condensation  of  1  mol.  of  diazomethane 
with  1  mol.  of  acetylene  : 

CH  N  CH  =  N 

|||.  +  CH/H  |  ")NH  (Pyrazole). 

CH  XN  CH=CHX 

s 

It  is  very  stable,  melts  at  70°,  is  a  feeble  base,  and  has  a  neutral  reaction  in  water.  The 
a'/3'-dihydro-compound  is  known  as  Pyrazoline,  C3H6N2,  and  the  a'-keto-derivative 

CH  :  Nv 
pf    this,      |  /NH,   as    Pyrazolone.      Condensation    of    methylphenylhydrazine, 


PYRIDINE  623 

CH3  •  NH  •  NH  •  C6H5,  with  ethyl  acetoacetate  yields  Dimethylphenylpyrazolone, 
CH3-C-N(CH3K 

/N'C6H6,  which  bears  the  name  antipyrine  and  is  used  medicinally 
H-C—     —OK 

owing  to  its  marked  antipyretic  action  on  the  animal  organism  ;  it  melts  at  113°, 
dissolves  in  water  and  in  alcohol,  and  gives  a  greenish  blue  coloration  with  nitrous  acid 
and  a  red  coloration  with  ferric  chloride. 

NC=Hx 
THIAZOLE,  C3H3NS,  or   |  /S,  may  be  regarded  as  thiophens  with  one  CH 

CH=CHX 

group  replaced    by   N.     It    shows  analogies  with  the  pyridine  bases.     Just  as  benzene 
may  be  obtained  from  aniline,  thiazole  may  be  obtained  from  aminothiazole  (see  below). 
AMINOTHI  AZOLE,  C3H2NS  •  NH2,  is  obtained  by  the  action  of  monochloracetaldehy  de 
on  pseudo-thiourea  : 

CH2-C1  HNV  CH— 

+  >C—  NH2     =     HC1  +  H20      +      || 

CHO  HSX  CH  — 

and  is  a  base  analogous  to  aniline. 

N=CH\ 
IMIDAZOLE  or  Glyoxaline,  C3H4N2  or    |  NH,  melting  at  92°,  is  a  strong  base 


with  a  fishy  odour,  and  is  isomeric  with  pyrazole  (see  above)  ;  it  is  obtained  by  the  action 
of  ammonia  on  glyoxal  in  presence  of  a  little  formaldehyde.  Alloxan  (see  p.  366)  may 
be  regarded  as  a  derivative  of  imidazole. 

LYSIDINE,  Methyldihydroimidazole  or  Ethenylethylenediamine,  C3H3(CH3)N2H2, 
is  administered  as  a  solvent  for  uric  acid. 


OXAZOLE,  C3H3NO,  or    |  /O,  is  also  termed  Furazole,  owing  to  its  analogy 

HC=CH/ 
with  furfuran  (see  above).     Its  phenyl  derivatives  are  known,  as  also  are  those  of  Isooxazole, 


HC=N, 

OSOTRIAZOLE,       |          /NH,  is  faintly  acid  and  also  faintly  basic  in  character. 

HC=W 
It  melts  at  22°,  boils  at  204°,  and  is  soluble  in  water. 


TRIAZOLE  (or  Pyrrodiazole),     |  /NH,  melts  at  121°,  and  is  extremely  soluble 

HC  =  W 
in  water. 

HC=Nx 
TETRAZOLE,  /NH,  is  a  weak  acid  which  forms  explosive  salts  ;  it  melts 

N=N/ 
at  155°  and  is  soluble  in  water. 

HC=Nx 

AZOXAZOLE,      |  O,  is  also  termed  Furazan. 


4.  PYRIDINE  AND  ITS  DERIVATIVES 

Pyridine  is  a  heterocyclic  nucleus  containing  five  carbon  atoms  and  one 
nitrogen.  It  resembles  benzene  in  its  behaviour,  but  it  is  more  stable  or 
more  indifferent  towards  sulphuric,  nitric,  and  chromic  acids,  permanganate, 
&c.  Oxidation  of  the  homologues  with  side-chains  gives  pyridinecarboxylic 
acids,  and  the  latter,  when  distilled  with  lime,  give  pyridine. 

Its  hydro-derivatives  are  readily  formed  in  a  similar  manner  to  hydro- 
benzenes, 


624  ORGANIC    CHEMISTRY 

Halogen  derivatives  are  obtained  more  easily  by  the  action  of  PC15  or 
SbCl5  at  a  high  temperature  than  by  the  action  of  the  halogens  themselves. 

Oxidising  agents  attack  only  the  side-chains  and  not  the  pyridine  nucleus. 
With  sulphuric  acid,  a  pyridinesulphonic  acid  is  obtained,  and  this  gives  a 
hydroxyl-derivative  of  pyridine  on  fusion  with  potash,  or  a  nitrile  when 
treated  with  KCN.  There  is  hence  a  marked  analogy  to  benzene,  although 
direct  nitration  of  pyridine  is  not  possible  unless  phenolic  or  aminic  groups 
are  present. 

Pyridine  and  its  derivatives  are  decidedly  basic  in  character  (tertiary  bases) 
and  form  soluble  salts  with  hydrochloric  or  sulphuric  acid  and  insoluble  ones 
with  chromic  acid  ;  the  double  salts  with  platinum  and  gold  chlorides  are 
slightly  soluble.  Like  tertiary  bases,  they  combine  with  methyl  iodide  to  form 
quaternary  bases. 

From  the  complex  alkaloidal  groupings,  pyridine  compounds  are  often 
obtained  either  by  distillation  with  caustic  potash  or  merely  by  energetic 
oxidation . 

Coal-tar  and  Dippel  animal  oil  contain  various  pyridine  compounds  which 
are  separated  by  conversion  into  salts. 

General  methods  of  formation,  (a)  The  oxidation  of  quinoline  (see  later) 
yields  first  quinolinic  acid  (pyridinedicarboxylic  acid),  C5H3N(CO2H)2,  which 
then  loses  C02,  giving  pyridine.  /3-Methylpyridine  is  obtained  by  distilling 
acraldehyde- ammonia  ;  this  explains  the  presence  of  pyridine  products  in 
Dippel  oil,  acrolei'n  and  ammonia  being  formed  in  the  dry  distillation  of  non- 
defatted  bones. 

An  important  synthesis  is  the  general  one  of  Hantzsch  by  which  Ethyl 
Dihydrocollidinedicarboxylate,  for  example,  is  obtained  by  heating  aldehyde- 
ammonia  with  ethyl  acetoacetate  ;  other  pyridine  compounds  are  obtained 
from  different  aldehyde-ammonias  and  /3--ketonic  acids  : 

2CH3-CO-CH2-C02C2H5  +  CH3-CHO  +  NH3  = 

C5N(CH3)3H2(C02C2H5)2  +  3H20. 

From  the  ester  thus  formed  the  hydrogen  of  the  NH  and  CH  is  eliminated  by 
means  of  nitrous  acid,  and  the  resulting  collidinedicarboxylic  acid,  when  treated 
with  potash  and  distilled  with  lime,  loses  the  two  carboxyls  and  gives  collidine 
(trimethylpyridine)  ;  oxidation  of  the  latter  gives  pyridinecarboxylic  acid  and 
elimination  of  carboxyl  from  this  in  the  ordinary  way  forms  pyridine. 

When  ethylidene  chloride  is  heated  with  alcoholic  ammonia,  it  yields 
Aldehydine,  C8HU-N. 

The  constitution  of  pyridine  corresponds  with  that  of  benzene,  in  which  one  methinic 
group,  CH,  has  been  replaced  by  a  nitrogen  atom.  Korner  in  1869  proposed  the  following 
constitutional  formula,  which  still  agrees  well  with  all  the  general  properties  of  the  pyridine 
compounds : 


CH 
HC 

HC 


CH 

i 

N  N 

When  pyridine  is  reduced  with  alcohol  and  sodium,  it  fixes  six  atoms  of  hydrogen, 
giving  Piperidine  or  hexahydropyridine,  the  constitution  of  which  is  shown  by  its  synthesis 
when  pentamethylenediamine  hydrochloride  is  rapidly  heated : 

/CH2-CH2-NH2  /CH2-CH.2\ 

CH/  «        NH3       +       CH2<  ')NH. 


When  piperidine  is  heated  with  sulphuric  acid  it  gives  pyridine,  and  the  latter,  when 
strongly  heated  with  hydriodic  acid,  gives  normal  pentane.  The  constitution  of  pyridine 
is  confirmed  by  the  fact  that  the  isomeric  substitution  products  correspond  exactly  in 
number  with  those  derivable  theoretically  from  Korner's  formula.  There  are,  indeed, 
three  monosubstituted  isomerides  (a,  ft,  and  y),  and  six  disubstituted  isomerides :  aa', 
aft,  aft',  /3y,  and  ftft'. 

The  position  of  a  substituent  group  is  determined  by  converting  it  into  a  carboxyl 
group  with  formation  of  the  corresponding  acid  of  known  constitution  (see  later).  Thus, 
picolinic  acid  has  the  carboxyl  in  the  a-position,  nicotinic  acid  in  the  ft-,  and  isonicotinic 
acid  in  the  y-position. 

PYRIDINE,  C5H5N,  is  a  coiourless  liquid,  boiling  at  115°  and  having  the 
sp.  gr.  1-0033  at  0°.  It  dissolves  in  water  in  all  proportions  and  has  a  slight 
alkaline  reaction  (not  sensitive  to  phenolphthalein,  slightly  to  litmus,  and  more 
so  to  methyl  orange). 

It  has  an  unpleasant  odour  and  is  hence  used  to  denature  alcohol  (see  p.  152). 

It  forms  a  slightly  soluble  f errocyanide,  by  means  of  which  it  can  be  purified. 
It  forms  pyridineammonium  iodides,  e.g.  C5H6N,CH3I,  which  with  KOH  in 
the  hot  gives  Dihydromethylpyridine,  C5H4H2-NCH3,  with  a  characteristic 
pungent  odour. 

Metallic  sodium  polymerises  pyridine,  forming  Dipyridine,  C10H10N2 
(b.pt.  290°)  and  y-Dipyridyl,  C10H8N2  or  NC5H4-C6H4N  (m.pt.  114°).  With 
sulphuric  acid  it  gives  /3-Pyridinesulphonic  Acid,  NC5H4'S03H. 

Pyridine  is  administered  in  cases  of  asthma  and  has  been  suggested  as  a 
means  of  purifying  synthetic  indigo. 

Mixed  pyridine  bases  for  denaturing  cost  about  Is.  2d.  per  kilo  and  pure 
pyridine  8s. 

Of  the  homologues  of  pyridine,  the  following  may  be  mentioned  : 

PICOLINE  (Methylpyridine),  NC5H4'CH3,  exists  as  three  isomeric  liquids  similar  to 
pyridine  and  of  disagreeable  odour  ;  their  boiling-points  are  :  a,  129°  ;  ft,  142°  ;  y,  144°. 
Besides  by  general  synthetical  methods  (see  above),  /3-picoline  is  formed  by  heating  strych- 
nine with  lime,  a -Methylpyridine  condenses  with  aldehydes  by  means  of  the  methyl 
group,  giving  alkines  :  NC6H4-CH3  +  CH3-CHO  =  NC5H4-CH2-CH(OH)-CH3.  This 
a-picolylalkine  gives  up  a  molecule  of  water  yielding  a  pyridine  derivative  with  an  un- 
saturated  side-chain,  e.g.,  a-allylpyridine,  NC6H4-CH  :  CH-CH3. 

These  reactions  proceed  in  one  stage  if  zinc  chloride  is  present  with  the  aldehyde. 

LUTIDINES  (Dimethylpyridines),  NC5H3(CH3)2 ;  three  isomerides  are  known,  with 
the  boiling-points :  aa',  143°  ;  ftft',  170°  ;  ay,  157°. 

COLLIDINES  (Trimethylpyridines),  NC6H2(CH3)3,  are  isomeric  with  propylpyridine. 
a-Allylpyridine  (see  above)  fixes  hydrogen  (alcohol  and  sodium),  giving  the  alkaloid  CONIINE 
(inactive  racemic),  which  is  a-Propylpiperidine  ;  fractional  crystallisation  of  the  tartrate 
separates  the  laevo-  from  the  dextro-form,  the  latter  being  identical  with  natural  coniine 
(the  poison  of  hemlock),  boiling  at  1 67°.  The  asymmetric  carbon  atom  causing  the  activity 
is  the  a-  one  united  with  the  propyl  group. 

PYRIDONES  or  HYDROXYPYRIDINES,  NC6H4-OH.  The  three  isomerides  are 
known,  their  boiling-points  being :  a,  107°  ;  ft,  124°,  and  y,  148°.  They  are  obtained 
by  heating  the  corresponding  hydroxypyridinecarboxylic  acids  with  lime.  They  are 
phenolic  in  character  and  give  red  or  yellow  colorations  with  ferric  chloride.  a-Hydroxy- 
pyridine  forms  two  series  of  derivatives  corresponding  with  the  two  tautomeric  formulae  : 

/C(OHK  /C°\ 

C2H2\  /C2H<{  and  C2rI2\  x-C2H2, 


the  former  giving,  for  instance,  a  Methoxypyridine  and  the  latter  a  Methylpyridone. 

PYRIDINEMONOCARBOXYLIC  ACIDS,  NCSH4-C02H.  The  three  isomerides  are 
as  follow :  a  or  Picolinic  Acid,  m.pt.  135° ;  ft  or  Nicotinic  or  Nicotic  Acid,  m.pt.  231° ; 
y  or  isonicotinic  acid,  m.pt.  309°, 

They  are  formed  by  oxidation  of  pyridine  derivatives  with  a  side-chain  or  by  elimination 
n  40 


626  ORGANIC    CHEMISTRY 

of  one  carboxyl  from  the  pyridinedicarboxylic  acids,  that  nearer  to  the  nitrogen  being 
the  more  easily  eliminated.  Nicotinic  acid  is  obtained  on  oxidation  of  nicotine.  When 
boiled  with  sodium  amalgam  in  a  highly  alkaline  solution,  these  acids  lose  nitrogen  as  NH3 
and  give  saturated,  open-chain,  dibasic  hydroxy-acids. 

When  the  carboxyl  is  in  the  a-position  (with  the  dicarboxylic  acids  also),  an  orange 
coloration  is  given  with  FeS04. 

As  they  are  both  acid  and  basic  in  character,  they  exhibit  analogies  with  glycocoll  (see 
p.  355). 

The  PYRIDINEDICARBOXYLIC  ACIDS,  NC5H3(C02H)2,  have  the  following  melting- 
points  :  cm'  or  Dipicolinic  Acid,  226°  ;  /3/3'  or  Dinicotinic  Acid,  323°  ;  a/3  or  Quinolinic 
Acid,  190°  ;  Isocinchomeronic  Acid,  236°  ;  ay  or  Lutidinic  Acid,  235°  ;  /3y  or 
Cinchomeronic  Acid,  249°. 

Quinohnic  acid  is  formed  by  the  oxidation  of  quinoline,  its  constitution  being  thus 
established  ;  and  since  in  the  hot  it  loses  C02  from  the  a-position,  giving  nicotinic  acid, 
the  constitution  of  the  latter  is  also  fixed. 

Pyridinetricarboxylic  Acids  (obtained  by  oxidising  cinchonine  or  quinine),  as  well  as 
Pentacarboxylic  Acids  and  Hydroxypyridinecarboxylic  Acids,  are  also  known. 

HYDROPYRIDINES.  The  Dihydropyridines  are  mentioned  above.  The  tetra- 
hydropyridines  and  their  derivatives  are  known  also  as  piperideines,  while  the  hexahydro- 
pyridines  and  their  derivatives  —  included  in  the  term  piperidines—  embrace  pipecoline, 
NC5H10-CH3  ;  lupetidine,  NC6H9(CH3)2;  copellidine,  NC5H8(CH3)3,  &c. 

PIPERIDINE,  NC6Hn,  is  obtained  by  heating  Pipeline  or  piperylpiperidine, 
C6H10N-C12H903  (m.pt.  129°),  which  is  the  alkaloid  contained  in  pepper,  and  is  formed  by 
the  condensation  of  1  mol.  of  piperic  or  piper  inic  acid,  C12H1004,  or 

CH2<Q>C6H3-CH  :  CH-CH  :  CH-C02H 

with  1  mol.  of  piperidine.     For  the  constitution  and  syntheses  of  the  latter,  see  p.  624. 

Piperidine  boils  at  106°,  has  an  odour  of  pepper,  is  strongly  basic,  and  is  soluble  in  water 
or  alcohol.  With  H202  it  gives  aminovaleraldehyde. 

Piperidine,  being  a  secondary  base,  forms  with  2CH3I  an  ammonium  iodide  derivative 
which,  when  distilled  with  silver  oxide,  gives  an  unsaturated  open-chain,  tertiary  base  ; 
in  its  turn  the  latter,  with  CH3I,  Ag20,  and  distillation,  loses  trimethylamine  and  forms 
Piperilene,  CH2  :  CH-CH2-CH  :  CH2. 

To  the  group  of  heterocyclic  compounds  belong  the  following,  which  are  of 
little  importance  : 

0  N  CH  0 

/\  /\  /\  /\ 

HC       OH          HG       CH          HC       CH          CH2       CH2 


HC       CH          HC       CH  N       N  CH2       CH 


CO  N  CH  NH 


Pyrone  or  pyrocomane  Pyrazine  or  aldine  Pyrimidine  Morpholine, 

(m.pt.  32°)  J  the  iso-  (m.pt.  47°)  is  basic  or  m-diazine  a  base,  b.pt. 

meric  <*-pyrone  is  and  with  H  gives  (m.pt.  22°)  129° 

coumalin  piperazine,  C4H10N2 

From  these  compounds  can  be  derived  coumalinic  or  comanic  acid, 
C5H302-C02H  (also  formed  from  malic  acid);  Meconic  Acid,  CgHO^OH) 
(C02H)2,  which  can  be  obtained  from  opium  and  gives  pyromeconic  acid  by 
elimination  of  C02  ;  Chelidonic  Acid,  C5H2O2(CO2H)2,  which  is  found  in 
celandine,  loses  CO2  giving  comanic  acid  and  pyrone. 

^ 

ALKALOIDS 

These  are  found  in  various  plants  and  have  medicinal  and  often  poisonous 
properties  ;  some  of  them,  such  as  caffeine,  theobromine,  &c.,  were  described 
on  p.  368,  and  the  principal  ones  having  basic  characters  (vegetable  bases)  will 
be  considered  here. 


ALKALOIDS  627 

They  are  almost  all  laevo-rotatory  and  have  an  alkaline  reaction  and  a 
bitter  taste.  They  are  soluble  in  alcohol  and  to  a  less  extent  in  ether, 
and  are  usually  insoluble  in  water  and  in  alkali ;  in  acids  they  dissolve 
with  formation  of  crystallisable  salts.  Nearly  all  alkaloids  are  precipitated 
from  their  solutions  by  tannin,  phosphomolybdic  acid,  potassium  mercury 
iodide,  HgI2,KI,  or  aromatic  nitro- derivatives  (e.g.  picric  acid,  &c.),  &C.1 
From  plants  they  are  extracted  with  acid  solutions  and  are  then  liberated 
with  alkali  and  either  distilled  in  steam  or,  if  they  are  non-volatile, 
filtered. 

When  converted  into  salts  by  means  of  strong  acids,  their  specific  rotatory 
power  is  not  greatly  influenced,  since  these  acids  are  almost  completely  dis- 
sociated in  aqueous  solution  ;  with  weak  acids,  however,  the  salts  are  only 
slightly  dissociated  and  hence  the  rotatory  power  is  different,  being  due  to  very 
different  ions. 

A.  Pictet  (1906)  regards  the  alkaloids  not  as  assimilation  products  of  the 
organism,  but  rather  as  nitrogenous  decomposition  products  of  proteins, 
nucleins,  chlorophyll,  &c.,  which  have  condensed  with  other  substances  present 
in  the  plants.  It  is  supposed  that  alkaloids  containing  the  pyrrole  group 
have  their  origin  in  protein  or  chlorophyll,  in  which  such  group  is  certainly 
present,  while  those  with  a  pyridine  grouping  have  a  similar  origin,  the  trans- 
formation of  the  pyrrole  into  the  pyridine  nucleus  being  possible  even  in  the 
laboratory  ;  the  pyridine  group  itself  does  not  appear  to  exist  in  the  proteins, 
chlorophyll,  &c.2 

1  Separation  and  Tests  of  Alkaloids.     A  mixture  of  these  is  separated  as  follows  : 

I.  From  the  neutral  or  acid  aqueous  solution,  ether  extracts  :  digitalin,  picrotoxin,  and  colchicine,  and  from  a 
solution  of  these  the  first  and  last  are  precipitated  by  tannin. 

II.  From  the  alkaline  aqueous  solution,  ether  extracts :  coniine,  nicotine,  brucine,  delphinine,  narcotine,  vera.* 
trine,  atropine,  strychnine,  aconitine,  quinine,  codeine,  and  physostigmine. 

III.  From  the  alkaline  aqueous  solution,  cliloroform  extracts  :  cinchonine,  caffeine,  curarine,  morphine,  solanine, 
and  theobromine. 

The  separate  alkaloids  can  be  distinguished  by  the  following  colorimctric  tests,  arranged  by  Hager.  The  colours 
are  represented  shortly  (as  with  the  colouring-matters  ;  see  later)  as  follow  :  0  =  orange  ;  B  =  blue  ;  Br  = 
brown  ;  D  =  decolorised  or  colourless  ;  Y  —  yellow  ;  Or  =  grey  ;  Bl  =  black  ;  R  =  red  ;  r  =  rose  ;  Gn  = 
green  ;  V  =  violet ;  +  =  intense  ;  —  =  weak.  The  reagents  most  commonly  used  are  : 

(1)  Erdmann's  reagent :   to  20  drops  of  a  solution  containing  10  drops  of  HNO3  (sp.  gr.  1-153)  and  20  c.c.  of 
water  are  added  40  c.c.  of  concentrated  HaSO4.     One  cubic  centimetre  of  this  liquid  is  poured  ou  to  1  to  2  grms.  of 
the  dry  aklaloid  and  the  changes  observed  after  15  to  30  minutes. 

(2)  Friihde's  reagent :   0-5  grm.  sodium  molybdate  in  100  c.c.  cone.  HjSO4. 

(3)  Mandelin's  reagent :  1  grm.  ammonium  vanadate  in  200  grms.  H2SO«  (monohydrate), 

(4)  Marquis's  reagent :  a  solution  of  formalin  in  sulphuric  acid. 

(5)  Lafou's  reagent :  sulphuric  acid  solution  of  ammonium  seleuite. 
See  Table  on  p.  628. 

»  Synthesis  of  Alkaloids  and  Medicine.  Even  during  the  most  remote  ages  human  beings  sought  remedies 
for  their  ailments  in  the  principles  contained  in  various  plants  and  animals.  Galen  (A.D.  131-200)  studied  various 
medicines  more  rationally  than  had  been  previously  done  by  Hippocrates  (400  B.C.). 

Numerous  medicines  proposed  by  Galen  were  used  as  sovereign  remedies  for  some  centuries,  until  indeed 
Paracelsus  (1493-1541)  gave  a  new  direction  to  medicine  by  contesting  the  theory  of  Galen  and  of  Avicenna 
and  by  founding  iatrochemistry,  which  had  such  a  large  following  in  the  Middle  Ages,  and  which  ultimately  degene- 
rated into  the  most  fantastic  sorcery  (see  History  of  Chemistry,  vol.  i,  p.  14). 

Modern  chemistry  alone  could  yield  medicine  any  real  support,  by  rigorous  control  of  the  physiological  and 
chemical  actions  of  all  the  natural  and  artificial  drugs. 

In  the  past  the  curative  properties  of  various  substances  were  discovered  by  pure  chance  ;  this  was  the  case, 
for  instance,  with  antifebrin  (acetanilide),  which  was  administered  to  a  patient  in  mistake  for  naphthalene.  But 
nowadays  a  rational  procedure  is  followed,  use  being  made  either  of  analogy  in  chemical  constitution  between  the 
substance  under  consideration  and  others  of  known  action  or  of  systematic  physiological  tests,  first  on  animals 
and  afterwards  on  human  beings. 

Until  the  beginning  of  the  nineteenth  century,  the  energies  of  chemists  were  directed  to  the  discovery  of  the 
active  and  essential  principles  of  those  parts  of  plants  successfully  applied  in  medicine.  When  these  were  isolated 
in  the  pure  state,  attempts  were  made  to  establish  their  chemical  structures  and,  in  some  cases,  to  effect  their 
manufacture  synthetically. 

A»  early  as  1805  Serturner  discovered  and  isolated  morphine,  the  active  principle  of  opium,  and  in  1821  Pelletier 
and  Caventou  discovered  the  alkaloids  of  cinchona  bark,  which  were  studied  in  1850  by  Strecker  with  the  object 
of  ascertaining  their  chemical  constitution.  The  synthesis  of  these  alkaloids  was  by  no  means  an  easy  task,  but  in 
cases  where  they  themselves  have  not  been  obtained  by  laboratory  reactions,  simple  derivatives  have  been  prepared, 
and  these  often  exhibit  similar  therapeutic  properties.  Thus  synthesis  has  given  codeine  (or  methylmorphine) 
and  dionine  (ethylmorphine),  which  in  many  cases  are  excellent  substitutes  for  morphine,  as  they  are  scarcely  if 
at  all  poisonous.  Derivatives  of  cocaine,  such  as  eucaine  (a  derivative  of  y-methoxypiperidine  ;  Ger.  Pats.  90,235 
and  97,672),  and  of  quinine,  such  as  euquinine  (the  carbethoxy-derivative  of  quinine,  without  the  bitter  taste  of  the 
mother-substance),  have  also  been  prepared. 

Chemical  investigation  not  only  gives  new  products  but  leads  to  improved  manufacture  and  consequent  cheapen- 


628 


ORGANIC    CHEMISTRY 


Alkaloid 

H2S04 
cone. 

HN03 
sp.  gr. 
1-4 

Erd- 
mann's 
reagent 

Frohde's 
reagent 

Mando- 
lin's 
reagent 

Marquis's 
reagent 

Lafou's 
reagent 

2  per  cent, 
aqueous 
furfural 

Aconitine 

Y-Br; 

F 

Y-Br  ;  in 

Y-Br, 







— 

after  24 

the  hot 

then  D 

hours  Br- 

R-Br 

R;  after  4 

hours  D 

Atropine 

DOT  Br 

substance 

D 

D 

— 

— 

— 

— 

Br,  solu- 

tion D 

Brucine 

—  r 

+.R,then 

Band 

R,  then 

— 

— 

r 

— 

0 

then  F 

F  ;  after 

24  hours 

D 

Quinine 

D 

D 

-  D 

Dor  —Gn 

— 

— 

— 

— 

Quinidine 

-  D 

D 

-  D 

-  D 

— 

— 

—  • 

— 

Cinchonine 

D 

D 

D 

D 

— 

— 

•  — 

— 

Digitalin 

Br  then  R 

-  Br 

R-Br,  then 

+  Othen 

— 

— 

— 

— 

R  ;  after 

+R;  in 

15  hours 

30  minute 

+R 

Bl-Br  ; 

after  24 

hours 

* 

6'n-F 

Caffeine 

D 

D 

D 

D 

— 

— 

— 

— 

Codeine 

D,  after  8 

r  then  F 

D  then  B 

G'nthcn  B 

Gn  in  hot 

F 

Gn 

— 

days  B 

or  after  24 

B 

hours  —  F 

Cocaine 

D 

D 

D 

D 

— 

— 

— 

— 

Colchicine 

+  F 

FthenB 

Y 

Fand 

— 

— 

— 

— 

and  F 

-Gn-Y 

Coniine 

D 

Dthen 

D 

Y 

— 

— 

— 

— 

-FthenD 

Morphine 

D,  in  hot 

0  then  F 

—  .Rtiien 

V,  then 

— 

R 

Gn 

R 

R  then  F 

Br  . 

Gn,  Br, 

and  Gn 

after  24 

hours  F 

Narcotine 

-  Y  then 

F  then  D 

Y,0 

Gr,  then 

R 

— 

Gn-Br,  in 

— 

0  and 

Br,  Y,  r 

the  hot  R 

after  24 

hours  r 

Narceine 

Br  then  F 

F 

Fthen 

Br  then  F 

0,  in  the 

F 

B,  Br 

— 

-  Br 

andD 

hotB 

Nicotine 

D 

Fthen 

D 

Fthenr 

— 

— 

— 

— 

R-V  and 

then  D 

Papaverine 

V  then  B 

0 

V  then  B 

F  then  B 

— 

— 

— 

— 

YD 

Physostigmine 

FthenGn 

— 

'  — 

— 

— 

— 

— 

— 

Pipeline 

R  then  0 

0  and 

-Y-Br 

Fthen 

Br-Gn 

R 

GnBr 

Y-Gn 

with  alkali 

-f  BrBl 

toGnB 

R 

Solanine 

0,  and 

Dthen 

-Y 

JSthen 

0 

Br 

R-Br 

R  then  F 

after  20 

-B 

Br  and  F 

hours  Br 

Strychnine 

D  and  with 

Y 

D  ;  with 

D 

V 

— 

— 

— 

bichro- 

MnO2 F 

mate  F 

then  R 

Thebaine 

R  then  0 

Y 

R  then  O 

R  then  O 

R 

R 

— 

-  R  then 

and  Z» 

D 

Theobromine 

D 

D 

D 

Z> 



— 

— 

— 

Veratrine 

O  then  R 

Y 

O  then  R 

F  then  R 

R 

RBr 

— 

F,  in  hot 

B 

Adrenaline 

— 

— 

— 

Y  Br  then 

Y,Br 

RBr 

Gn 

-Y 

GnR 

Berberine 

Gn 

+  RBr 

Gn 

Gn-Br 

B  Fthen 

Fin  hot, 

BrGn 

— 

VBr 

Gn 

Hydrastine 

— 





Gn  Gr 

R 



Br 

— 

Picrotoxin 

— 

— 

— 

O 

YGn 

-R 

— 

— 

Digitoxin 

— 

— 

Br 

BrV 

r 

BrV 

V 

ANESTHETICS  629 

The  consumption  of  alkaloids  is  growing  in  all  countries.  The  imports 
into  Italy  (exclusive  of  quinine)  amounted  to  14,200  kilos  in  1908  and  17,320 
kilos,  of  the  value  of  £138,545,  in  1910. 

CONIINE,  C8H17N,  is  found  in  hemlock  (Conium  maculatum).  For  its 
constitution  and  syntheses,  see  above. 

NICOTINE,  C10H14N2,  is  a  strong  diacid  base  which,  in  combination  with  malic  and 
citric  acids,  forms  the  poisonous  alkaloid  of  tobacco.  It  is  an  oil  boiling  at  247°  and  possess- 
ing a  very  strong  odour  ;  it  is  soluble  in  water,  alcohol,  or  ether,  and  turns  brown  in  the 

ing  of  the  old  ones.  Thus,  quinine,  which  twenty  years  ago  cost  £40  per  kilo,  Is  now  sold  in  a  highly  pure  state 
for  32s.  Vast  works  now  turn  out  enormous  quantities  of  synthetic  drugs,  although  these  are  administered  in 
closes  of  centigrammes  ;  thus,  antipyrine,  discovered  by  Knorr,  was  consumed  to  the  extent  of  hundreds  of  thousands 
of  kilos  in  the  first  few  years  during  which  influenza  made  its  appearance. 

Modern  industrial  conditions  have  rendered  possible  the  development  of  serotherapy  (see  p.  115).  and  great 
results  are  now  promised  by  organotherapy  or  ototherapy.  This  is  based  on  the  fairly  general  phenomenon  that 
in  the  different  organs  of  a  healthy  individual  substances  are  continually  produced  capable  of  guarding  them 
against  different  affections.  This  principle,  introduced  vaguely  and  confusedly  by  Brown-Se'quard  in  France  in 
1891,  was  in  1895  brought  forward  with  triumph  by  Baumann,  who  found  that  in  many  persons  goitre  is  due  to 
deficient  secretion  of  iodo-products  by  the  thyroid  glands  (see  vol.  i,  p.  151),  and,  having  extracted  the  active 
iodine  principle,  thyroidin,  from  the  thyroid  of  healthy  sheep,  that  this  constitutes  a  rapid  and  effective  cure  for 
goitre.  For  the  treatment  of  other  diseased  organs,  ovarin,  cerebrin,  nucleiti,  &c.,  were  prepared  from  the 
corresponding  organs  of  healthy  animals. 

Coal-tar  derivatives  have  been  employed  for  the  synthesis,  not  only  of  artificial  alkaloids,  antipyretics,  and 
antiseptics,  but  also  of  an  important  group  of  anaesthetic  or  hypnotic  substances  which  have  been  of  great  service 
to  medicine  and  especially  to  surgery  in  rendering  painless  the  most  complicated  operations.  At  first,  substances 
such  as  ether  and  chloroform  were  employed  which  produced  general  ancesthesia  of  the  organism ;  but  the  use  of 
these,  especially  of  chloroform,  was  attended  by  much  inconvenience  and  often  by  death  of  the  patient.  Sulphuric 
ether  was  recognised  as  an  anaesthetic  by  Faraday  as  early  as  1818,  but  it  was  used  for  the  first  time  by  the  American 
doctor,  0.  W.  Long,  in  1842. 

The  anaesthetic  is  carried  by  the  blood  into  contact  with  the  nerve-centres  which  perceive  pain,  producing 
a  poisoning  and  a  paralysis  which  last  for  some  time,  but  at  the  same  time  those  centres  which  govern  the  action 
of  the  heart  and  of  respiration  are  also  affected,  thus  causing  the  dangers  and  disturbances  accompanying  general 
anaesthesia.  The  nervous  currents  start  from  the  periphery,  from  the  points  where  the  surgical  operation  begins, 
and  are  transmitted  to  the  brain,  which  transforms  them  into  the  sensation  of  pain,  and  it  is  precisely  by  the 
influence  of  the  anaesthetic  on  the  cerebral  centres  that  pain  is  avoided.  But  anaesthesia  ceases  to  be  dangerous 
when  the  paralysis  is  effected  on  the  peripheral  nerve-centres  at  the  beginning  of  the  nervous  currents,  without, 
however,  reaching  the  brain.  In  this  way  the  idea  of  local  ancesthesia  was  arrived  at,  this  being  much  more  rational 
and  much  less  dangerous,  since  by  its  means  only  the  single  organ  or  region  of  the  body  to  be  operated  on  is  rendered 
insensible. 

To  chloroform,  ether,  &c.,  were  added,  in  1885,  cocaine,  which  paralyses  only  the  sensitive  peripheral  nerves 
and  does  not  influence  the  motor  nerves.  It  can  now  be  indicated  which  specific  atomic  groupings  in  the  molecules 
of  anaesthetics  or  hypnotics  confer  on  these  their  special  properties. 

Hypnotics  include  those  of  (1)  the  chloral  hydrate  group,  to  which  belong  also  chloralamide  (chloralformamide) 

/-1TTT  /I    TT 

and  paraldehyde ;  (2)  the  tert.  amyl  alcohol  class,  r«H*^>c<CoH  *'  cliaracterised  bv  the  presence  of  a  hydroxyl 
and  of  a  carbon  atom  united  to  three  alkyl  groups,  the  action  of  these  compounds  increasing  with  the  molecular 
weight ;  (3)  the  intermediate  dormiol  [tert.  amylchloral,  CCla'CH(OH)(OC5H,,)]  class ;  (4)  the  urethane  deri- 
vatives, including  hedonal  (methylpropylcarbinol  urethane,  NHj'CO-O-CH(CHs)(CsH7)  ;  (5)  a  group  of  compounds 
containing  a  single  carbon  atom  united  to  two  alkyl  groups  and  to  two  sulphonic  residues,  e.g.  trional, 

("*TT  SO  "C*  TT 

£ Tr3^>c<Cso1'-C  H  (metfylsl'lPJlonal or  diethylsulphonemethylethylmethane) ;  (6)  a  group  studied  by  B.  Fischer 
and  consisting  of  urea  derivatives,  e.g.  NHs-CO-NH-CO-CH(CjH5),  (diethylacelylurea)ot,  better,  diethylmalonylurea, 
CO<^NJT]CO^>C<^Q!VS  (diethylbarbituric  acid),  which  bears  the  name  of  veronal  (m.pt.  191" ;  it  was  prepared 

by  E.  Fischer  and  J.  Mering,  patented  by  Messrs.  Merck  in  1903  and  then  made  by  Messrs.  Fr.  Bayer,  of  Elberfeld) 
and  serves  to  replace  chloroform,  being  free  from  the  dangerous  consequences  of  the  latter  (provided  that  it  is  not 
administered  to  patients  with  weak  kidneys).  Change  of  the  alkyl  groups  in  veronal  is  accompanied  by  change 
in  the  properties  ;  thus,  dimethylbarbituric  acid  has  no  hypnotic  properties,  dipropylbarbituric  acid  is  more  effective 
than  veronal,  while  dibenzylbarbituric  acid  is  without  action,  possibly  owing  to  its  slight  solubility. 

According  to  H.  Meyer  and  Overton,  all  substances  capable  of  dissolving  fats  are  more  or  less  anaesthetic, 
and  according  to  Nicloux  (1909)  the  substance  of  the  nervous  system  contains  an  abundance  of  lipoids,  i.e.  of 
compounds  soluble  in  the  same  solvents  as  fats  and  hence  capable  of  fixing  the  anaesthetics  (they  may  contain 
nitrogen  and  also  phosphorus).  Thus  the  quantity  of  anaesthetic  fixed  by  the  organism  and  hence  effective 
is  directly  related  to  the  quantity  of  lipoids  present  in  the  various  parts  of  the  body.  It  is  also  interesting  that 
structural  isomerism  produces  marked  change  in  the  physiological  action,  tropacocaine,  for  instance,  being  j>u 
anaesthetic,  while  benzoyltropine  acts  as  a  mydriatic. 

Of  the  numerous  other  anaesthetics,  orthoform  (methyl  ester  of  m-amino-p-hydroxybenzoic  acid),  alipme 
holocaine,  may  be  mentioned. 

But  in  order  that  local  anaesthesia  may  be  efficacious  and  lasting,  it  is  necessary  to  prevent  the  anaesthetic 
inoculated  at  a  certain  place  from  being  carried  away  (resorbed)  by  the  blood,  and  this  was  at  first  attained  by 
causing  the  venous  blood  at  that  place  to  stagnate  by  preventing  circulation.  The  same  end  was  reached  later 
by  intense  local  cooling  produced  by  the  rapid  evaporation  of  ethyl  or  methyl  chloride. 

For  internal  surgical  operations  (e.g.  in  the  thorax,  &c.),  adrenaline,  C,Ha(OH)2-CH(OH)-CH2'NH>CH,,  is 
of  the  greatest  use,  as  it  produces  considerable  contraction  of  the  blood-vessels  without  driving  all  the  blood 
from  them,  although  it  prevents  fresh  blood  from  arriving ;  the  anaesthetic  can  thus  be  kept  as  long  aa  is  desired 
in  the  inoculated  region.  The  substitution  of  cocaine  by  stovaine  (less  poisonous)  leads  to  partial  spinal  ancesthesia 
orjmedullary  anaesthesia,  which  now  permits  the  most  difficult  surgical  operations  on  the  abdominal  organs  and 
even  renders  possible  painless  childbirth. 


630 


ORGANIC    CHEMISTRY 


air.     When  oxidised  by  permanganate  it  forms  nicotinic  acid,  and  as  further  it  contains 
also  a  pyrrolidine  group,  its  constitution  is  represented  as  follows  : 


/CH^CH, 
CH/  \C— CH< 

^N  —  CH^ 


SN(CH3)— CH2 


Synthetically  it  is  obtained  from  /3-aminopyridine  which  is  converted  into  its  mucic 
cid  salt,  and  then  passes  through  the  following  stages : 


— N< 


N 


CH 


CH 


.CH-CH 


SNH-CH 


/3-Pyridylpyrrole 


a  :  /3-Pyridylpyrrole 


,CH CH 


Nicotine 


X 


N(CH3) 

Nicotyrine 


CH 


Practically  it  is  prepared  from  ordinary  tobacco  extract,  by  diluting,  rendering  strongly 
alkaline  with  NaOH,  and  extracting  with  ether.  From  the  ethereal  solution,  the  alkaloid 
is  extracted  by  shaking  with  dilute  sulphuric  acid  and  decanting  off  the  acid  solution.  The 
latter  is  again  made  strongly  alkaline  and  shaken  with  ether,  and  the  ethereal  solution 
dehydrated  by  means  of  solid  NaOH.  The  ether  is  then  distilled  off  and  the  remaining 
nicotine  distilled  in  a  stream  of  hydrogen. 

It  is  a  very  powerful  poison  and  is  used  medicinally  to  counteract  nervous  irregularity 
of  the  heart  and  is  employed  in  agriculture,  as  tobacco  extract,  to  kill  insects.1  Impure 
75  per  cent,  nicotine  costs  148s.  per  kilo,  and  the  pure  product  184s. 

1  Tobacco  is  a  herbaceous  plant,  originally  an  annual  but  now  sometimes  a  biennial,  of  the  order  Solonacese 
(Nicotiana  tabacum),  which  includes  about  fifty  species  and  sub-species  of  American  origin,  e.g.  the  Virginia  tobacco 
plant  (Nicotiana  tabacum,  see  Fig.  420),  the  Maryland  large-leaved  tobacco  (N.  latissima,  N.  rustica,  N.  suffruticosa, 
<fcc.).  These  grow  well  in  various  countries,  as  is  shown  by  the  following  Table,  giving  the  mean  production  of  raw 
tobacco  a  few  years  ago  (the  figures  given  are  tons) : 


Output 

Imports 
less 
Exports 

Exports 
less 
Imports 

Output 

Imports 

Exports 

United  States. 

250,000 

_ 

115,000 

Dutch  Indies  .         . 

34,000 

18,000 

British  India  . 

185,000 

— 

— 

Japan    .         .         . 

26,000 

— 

Austria-Hungary 

70,000 

14,000 

— 

France  .         .         . 

25.000 

23,000 

— 

Russia   . 

58,000 

— 

5,000 

Cuba      ."  '      . 

24,000 

— 

13,500 

Turkey  . 

40,000 

— 

14,000 

Philippines     .  '       . 

22,000 

— 

12.000 

Germany 

37,000 

45,000 

— 

Brazil    . 

17,000 

— 

11,000 

(a)  Belgium,    (6)  Al- 

Greece  .         . 

9,000 

— 

5,000 

geria,  (c)  Australia, 

(a)       Bosnia,       (6) 

(d)      Porto     Rico, 

(«)10,000 

(d)  4,500 

Netherlands  (c)  Ar- 

(c) 5,200 

(e)     R  o  u  m  a  n  i  a  , 

(c)    5,000 

(/)  3,000 

gentine,  (d)  Cochin 

(/)    San    Domingo, 

(e)   1,300 

(<7)  3,000 

China,    (e)  Mexico, 

(?)     Ceylon,     each 

each  about 

3,300 

about  . 

5,000 

(a)  China,  (6)  Para- 

(a) 5.500 

(a)  Italy,  (b)  Switzer- 

(6) 5,000 

guay     and     other 

(6)  5,000 

land,     (e)     Servia, 

(c)  1,000 

countries,   together 

120,000 

(d)    Sweden,    each 

(d)  4,300 

England 

— 

50,000 

from  1500  to. 

2,300 

Italy  imports  about  2000  tons  of  tobacco  leaf  (about  £1,080,000)  and  exports  manufactured  tobacco  to  the  value 
of  about  £200,000. 

The  world's  production  of  raw  tobacco  varies  from  900,000  to  1,000,000  tons,  of  the  value  of  £48,000,000  to 
£56,000,000.  The  price  is  about  £32  to  £40  per  ton  for  the  ordinary  quality  and  £120  to  £160  for  the  finer  qualities 
(Manila,  Havana,  Sumatra). 

Ordinary  tobacco  plants  are  only  slightly  branched  and  have  a  height  of  about  1  metre,  although  some  exceed 
li  metre.  They  are  studded  with  sticky  hairs,  and  the  leaves  are  wide  and  oval  or,  sometimes,  long  and  narrow, 
as  with  Chinese  tobacco  (N.  chinensis).  The  flowers  are  in  clusters  and  resemble  those  of  potatoes,  but  are  usualy 
flesh-red.  The  cultivation  of  tobacco  requires  a  good  soil  rich  in  humus,  and  the  climate,  soil,  and  mode  of  growing 
exeit  a  considerable  influence  on  the  quality  of  the  tobacco.  The  readiness  with  which  a  tobacco  burns  in  the  form 
of  cigars  depends  on  the  potash-content  of  the  plant,  while  chlorides  hinder  the  combustion.  On  this  account 
fertilisation  with  stable  manure,  sewage,  or  potassium  chloride  is  avoided,  preference  being  given  to  potassium 
or  ar  monium  sulphate  mixed  with  a  little  Thomas  slag  and  stable  manure.  The  young  plants  from  the  forcing 


TOBACCO 


631 


ATROPINE,  C17H23O3N,  is  the  alkaloid  of  the  berries  of  Atropa  belladonna  (deadly 
nightshade)  and  of  the  fruit  of  Datura  stramonium  (thorn-apple).  In  dilute  solution  it  is 
used  as  a  mydriatic  (enlarging  the  pupil  of  the  eye)  and  as- an  analgesic  (relieving  pain). 
It  is  somewhat  poisonous  and  melts  at  115-5°.  As  the  products  of  the  decomposition  of 
atropine  in  various  ways  comprise  heptamethylene  derivatives,  substituted  pyrrolidines 
and  piperidines,  Tropine,  NC8H15O,  and  Tropic  Acid  [C9H1003,  or  a-phenyl-/3-hydroxypro- 
pionic  acid,  OH-CH2-CH(C6H5)-G02H],  atropine  is  regarded  as  an  ester,  a  tropate  of 

house  arc  planted  out  in  about  March,  and  at  the  beginning  of  July  the  dry  and  dirty  leaves  near  the  soil  are 
detached,  together  with  the  useless  branches  and  the  flowers.  The  other,  useful  leaves  are  then  removed 
as  they  begin  to  yellow  and  are  dried  on  strings  or  in  steam  drying-ovens,  and  are  then  sorted  and  tied  in 
bundles. 

In  January  the  loaves  are  placed  in  heaps  so  as  to  induce  fermentation,  which  renders  them  brown  and  gives 
them  flavour. 

The  leaves  arrive  at  the  factory  in  cloth  bales.  They  are  first  sorted  into  kinds  suitable  for  different  types  of 
tobacco  and  are  then  beaten  to  remove  sand  and  dust.  They  are  then  arranged  in  layers,  each  of  which  is  sprinkled 
with  5  to  10  per  cent,  salt  solution  (it  is  this  which  renders  cigars 
hygroscopic)  to  soften  it,  to  facilitate  the  subsequent  operations 
and  to  prevent  putrid  fermentation.  In  this  state  it  is  some- 
times placed  in  tepid  apartments  to  initiate  a  second  fermenta- 
tion, which  refines  the  milder  qualities  ;  in  some  cases  this  end 
is  attained  by  washing  with  dilute  solutions  of  salts,  alkali,  or 
acid,  or,  more  rarely,  by  torrefying  at  60°  to  70°. 

The  best  flavour  and  aroma  are  obtained,  however,  by  curing, 
i.e.  by  immersing  the  leaf  in  an  aqueous  solution  of  saccharine 
substances,  various  drugs,  nitre,  colouring-matters,  aromatic 
substances,  alcohol,  &c.  (each  manufacturer  has  his  particular 
method  of  curing) ;  the  drained  or  pressed  leaves  are  then  left 
in  heaps  for  a  longer  or  shorter  time  until  they  are  uniformly 
soaked. 

By  suitable  machines  the  ribs  of  the  leaves  are  either  cut  or 
beaten  off  and  the  cut  leaves  then  dried  by  heating  in  revolving 
metal  drums  ;  the  dried  leaves  are  rapidly  cooled  in  a  current  of 
air,  A-c.  The  subsequent  operations  for  the  preparation  of 
cigars,  cigarettes,  cut  tobacco  for  pipes,  or  snuff  are  merely 
mechanical  and  need  not  be  described  here. 

Mention  may,  however,  be  made  of  recent  attempts  to 
diminish  the  harmful  effects  of  tobacco,  which  is  now  smoked 
in  every  country  in  the  world.  It  seems  that  when  the 
Spaniards  invaded  America,  the  use  of  tobacco  was  already 
known  in  that  country,  and  they  not  only  extended  its  use 
there  but  introduced  it  into  Europe  (by  the  Th6vet  brothers  in 
1517),  arousing  grave  apprehension  owing  to  a  statement  by 
the  medical  men  that  it  was  highly  injurious  to  health.  In 
1613  Tsar  Michael  Federowitz  prohibited  its  use  in  his  territory 
under  penalty  of  death  or  of  the  cutting  off  of  the  nose.  James 
of  England  published  in  1619  a  decree  forbidding  the  use  of 
tobacco  and  describing  smoking  as  a  "  habit  disgusting  to  the 
sight,  nauseating  to  the  smell,  dangerous  to  the  brain,  harmful 
to  the  heart,  and  spreading  around  the  smoker  repugnant 
exhalations."  In  1660  the  Senate  of  Berne  punished  the  use 
of  tobacco  like  robbery  or  homicide,  and  in  1623  Amurat  IV 
prohibited  its  use  by  the  Turks  in  order  that  they  might  not 
become  intoxicated  or  infertile.  But  to  human  nature  the 
forbidden  fruit  is  the  most  desired,  and,  being  useless,  is  none 
the  less  necessary.  The  employment  of  tobacco  spread  rapidly 
everywhere,  and  many  states,  to  limit  its  consumption,  imposed 
enormous  taxes  on  tobacco,  and  ended  by  making  it  a  Govern- 
ment monopoly  and  thus  deriving  a  vast  income  to  the 
Treasury. 

Since  then  no  Government  has  occupied  itself  with  the  health  of  its  subjects,  the  only  care  being  the  enlarge- 
ment of  the  Exchequer.  In  Italy,  after  the  partnership  between  the  Government  and  a  private  company  from 
1868  to  1883,  the  trade  in  tobacco  became  a  monopoly  of  the  State,  which  derives  from  it  a  net  annual  income  of 
about  £7,000,000. 

The  mean  yearly  consumption  of  tobacco  per  head  is  as  follows  :  North  America,  3-1  kilos  ;  Netherlands,  2-5  ; 
Belgium,  2-8  ;  Switzerland,  2-3  ;  Germany,  1-5  ;  Austria-Hungary,  1-5  ;  Sweden,  1-2  ;  Russia,  0-9  ;  Servia, 
08-  France,  0-8;  England,  0-7;  Italy,  0-6  ;  Roumania,  0-2  ;  Denmark,  0-1 ;  Finland,  0-1. 

The  harm  caused  by  tobacco  is  due  especially  to  the  nicotine,  to  which  man  becomes  accustomed  without 
serious  inconvenience,  in  the  same  way  as  to  change  of  climate,  food,  drink,  or  other  conditions.  Attempts  have 
been  made  in  recent  years  to  render  tobacco  less  injurious  by  extraction  of  the  nicotine  with  one  of  a  number  of 
solvents,  but  such  treatment  results  in  the  removal  of  the  aromatic  substances  of  the  tobacco  (gee  also  Ger.  Pats. 
178,962,  197,159,  and  212,417  of  1908). 

Better  results  are  obtained  by  filtering  the  smoke  through  fibres  or  textile  materials  before  it  reaches  the  mouth. 
Thus  the  Thorns  process  (Ger  Pat.  145,727),  which  has  proved  very  satisfactory,  consists  in  arranging  in  the 
mouthpiece  of  the  pipe  a  small  plug  of  cotton-wool  impregnated  with  ammoniaoal  ferric  chloride  or  ferrous  sulphate, 
this  retaining  all  the  burning  ethereal  oils,  the  hydrogen  sulphide,  a  considerable  proportion  of  the  hydrocyanic 
acid,  and  almost  all  the  nicotine  and  its  basic  derivatives  in  the  smoke.  Treating  the  raw  tobacco  with  ozone 
has  also  been  employed  with  the  view  of  facilitating  the  elimination  of  the  nicotine,  increasing  the  combustibility, 
and  improving  the  quality.  The  aroma  of  tobacco  is  also  intensified  by  the  addition  of  small  quantities  of  methyl- 
eugenol  and  methylisoeugenol. 


FlO.  420. 


062  ORGANIC    CHEMISTRY 

tropine,  the  structure  of  the  latter  (which  has  also  been  prepared  synthetically)  being, 
CH2— CH-    — CH2(«) 

N-CH3     CH-OH     (m.pt.  62°  ;  b.pt.  220°). 

I  I 

— CH CH2  (a) 

Hyoscyamine,  stereoisomeric  with  atropine,  melts  at  109°. 

Tropine,  formed  by  the  splitting  of  atropine  with  barium  hydroxide,  is  a  tertiary  base 
containing  a  secondary  alcoholic  group  and  is  therefore  known  also  as  tropanol.  When 
oxidised  with  chromic  acid,  it  forms  first  a  ketone,  Tropinone,  C8H13ON,  and  then  Tropinic 
Acid,  CH3N  :  C4H6(CO2H)(CH2-CO2H),  owing  to  the  rupture  of  the  piperidine  ring.  With 
concentrated  HC1,  tropine  forms  Tropidine  (or  tropene),  C8H13N,  which  is  obtained  also 
by  elimination  of  CO2  from  anhydroecgonine  and  forms  an  oily  base,  b.pt.  162°. 

OTHER  ALKALOIDS  are :  Veratrine  (cevadine),  C32H29O9N,  found  in  Veratrum 
album  ;  Sparteine,  C]5H26N2,  found  in  Sparticum  scoparium  ;  Sinapine,  C16H25O6N,  found 
in  the  seeds  of  white  mustard  and  derived  from  choline  and  from  Sinapic  Acid  (dimethyl- 
trihydroxycinnamic  acid),  C11H12O5 ;  Hydrastine,  C21H21O6N,  obtained  from  the  roots  of 
Hydrastis  canadensis,  has  similar  properties  to  the  alkaloid  from  Secale  cornutum  and  gives 
Hydrastinine,  C11H11O2N,H20,  on  oxidation. 

MORPHINE,  C17H1903N.  The  latex  of  the  capsule  of  Papaver  somniferum  when 
condensed  forms  opium,  which,  along  with  various  other  compounds  (see  next  page), 
contains  considerable  quantities  of  morphine  (about  10  per  cent.).1  Morphine,  melting  and 
decomposing  at  230°,  is  slightly  soluble  in  water  and  odourless,  and  possesses  narcotic 
and  analgesic  properties,  being  used  in  medicine  as  hydrochloride,  C17Hig03N,HCl,3H20. 
It  is  a  tertiary  base  with  phenolic  characters  and,  when  distilled  in  presence  of  zinc  dust, 
gives  pyridine,  pyrrole,  quinoline,  and  phenanthrene. 

Morphine  is  extracted  from  opium  by  means  of  water,  the  evaporated  aqueous  extract 
being  treated  with  sodium  carbonate  to  precipitate  all  the  alkaloids  (about  twenty) 
of  the  opium  ;  after  24  hours  the  precipitate  is  washed  with  water  and  then  with 
alcohol,  which  removes  the  resins  and  all  the  alkaloids  excepting  nearly  the  whole  of  the 
morphine.  The  crude  morphine  remaining  is  dissolved  in  acetic  acid  (which  leaves  behind 
the  narcotine  impurities),  the  solution  filtered  through  animal  charcoal,  and  the  morphine 
liberated  by  means  of  ammonia,  washed  with  cold  water  and  dried.  It  is  obtained  in  a 
purer  form  by  repeatedly  boiling  its  alcoholic  solution  with  animal  charcoal  and  recrystal- 
iising. 

The  action  of  opium  is  due  to  the  presence  of  a  number  of  alkaloids,  which  are  divided 
by  A.  Pictet  into  : 

(1)  The  Morphine  Group,  including: 

Morphine,  C17H17ON(OH)2  Codeine,  C17H17ON(OH)(OCH3) 

Pseudomachine,  [C17Hi6ON(OH)2]2  Thebaine,  Ci7H15ON(OCH3)2 

(2)  The  Papaverine  Group,  comprising  mainly  isoquinoline  derivatives,  which  have  a 
mild  physiological  action : 

Papaverine,  C16H9N(OCH3)4  Laudamine,  C17H15N(OH)(OCH3)3 

Laudanidine,  C17H15N(OH)(OCH3)3  Laudanosine,  C17H15N(OCH3)4: 

Codamine,  C18H18ON(OH)(OCH3)2  Cryptopine,  C19H1703N(OCH3)2 

Narcotine,  C19H14O4N(OCH3)3  Oxynarcotine,  C19H14O5N(OCH3)3 

Protopine,  C2oH1905N  Narceine,  C2oH]805N(OCH3)3 

Tritopine,  (C21H2703N)20  Meconidine,  C21H2304N 

i  Estimation  of  Morphine  in  Opium.  Of  the  various  methods,  that  of  Stevens  (1902)  gives  good  results  : 
^grms.  of  powdered  opium  are  mixed  in  a  mortar  with  2  grms.  of  fresh  calcium  hydroxide  and  10  grins,  of  water  ; 
an  additional  quantity  of  19  c.c.  of  water  is  then  introduced,  the  whole  being  mixed  for  half  an  hour,  and  filtered. 
Exactly  15  c.c.  of  the  nitrate  are  mixed  in  a  60  c.c.  bottle,  with  4  c.c.  of  alcohol  and  10  c.c.  of  ether,  0-5  grm.  of 
ammonium  chloride  being  then  added  and  the  bottle  shaken  for  30  minutes,  stoppered,  and  left  at  rest  in  a  cool 
place  for  12  hours.  The  mass  is  then  poured  on  to  a  filter  containing  a  tuft  of  cotton-wool  to  retain  the  morphine 
c  rystals.  The  bottle  and  funnel  are  washedwith  water  saturated  with  morphine  until  the  filtrate  becomes  colourless. 
The  funnel  is  now  placed  over  the  bottle,  the  cotton  lifted  with  a  glass  rod  drawn  out  to  a  curved  point,  and  the 
crystals  rinsed  into  the  bottle  with  12  c.c.  of  N/10-sulphuric  acid  ;  the  cotton  is  then  also  put  into  the  bottle,  which 
is  corked  and  well  shaken.  After  rinsing  both  cork  and  funnel  with  water,  the  excess  of  acid  is  titrated  with  N/10- 
caustic  soda,  using  as  indicator  a  solution  of  wdo-eosin  (eosin  blue)  or  litmus.  Multiplication  of  the  number  of 
cubic  centimetres  of  acid  fixed  by  the  morphine  by  1-5038  gives  the  percentage  of  morphine  in  the  opium,  but  this 
number  must  be  increased  by  1-12  to  compensate  for  the  morphine  remaining  in  solution. 


COCAINE,    ETC.  633 

Papaveramine,  C21H2105N  Gnoscopine,  C22H33O7N 

Santaline,  C37H3609  Hydrocotarnine,  CUH12O2N(OCH3) 

Lautopine,  C23H25O4N  Berberine,  C20H1704N 

Opium  contains  also  Meconic  Acid,  €71X407,  in  combination  with  various  alkaloids,  and 
further :  wax,  proteins,  caoutchouc,  pectio  and  gummy  matters,  lactic  and  sulphuric 
acids,  ammonium  salts,  &c. 

Good  opium  contains  8  to  24  per  cent,  of  water,  3-5  to  5  per  cent,  of  ash,  45  per  cent, 
of  aqueous  extract,  9  to  15  per  cent,  of  morphine,  about  5  per  cent,  of  narcotine,  0-8  per 
cent,  of  papaverine,  0-4  per  cent,  of  thebaine,  0-3  per  cent,  of  codeine,  and  0-2  per  cent,  of 
narceine. 

The  price  of  good  opium  is  28s.  to  32s.  per  kilo,  pure  crystalline  morphine  costing 
£24  and  its  hydrochloride  £18  per  kilo.  In  1905  Germany  imported  687  quintals  of  opium 
of  the  value  of  £65,200.  China  imported  26,000  quintals  in  1908,  about  25,000  in  1909, 
and  nearly  20,000  in  1910. 

In  1909  England  imported  200  tons  of  opium  (£269,695)  and  in  1910  300  tons  (£434,064), 
while  in  1911  the  exports  were  of  the  value  of  £78,982.  The  United  States  imported 
190  tons  (£273,800)  in  1910  and  300  tons  (£552,000)  in  1911. 

COCAINE,  Ci7H2iO4N,  with  other  alkaloids,  constitutes  the  active  part  of  the  leaves 
of  Erythroxylon  coca.  It  is  Isevo-rotatory,  melts  at  98°,  has  an  analgesic  action  and  serves 
also  to  produce  local  anaesthesia  (Roller,  1884). 

Strong  acids  in  the  hot  decompose  it  into  methyl  alcohol,  benzoic  acid  and  ecgonine, 
C9H15O3N(Lossen,  1865),  which  is  the  a-carboxyl  derivative  of  tropine(see  above),  and,  as 
with  methyl  alcohol  and  benzoic  acid  it  gives  cocaine  again,  the  latter  must  contain  the 

rOPTT 

groups  C9H13O2N{  n/-^^  ;    confirmation  of   this  is  given  by  the   synthesis  (rather  a 
^UL-6xl5 

complicated  one)  of  cocaine.  The  constitution  of  cocaine  is  as  follows  (Willstatter,  1898) : 
CH2— CH—  —  CH-C02CH3 

N*CH3      CH'C02C6H5;    the  characteristic  group  (ancesthesiophore)  is  the  benzoyl 

CH2 — CH CH2 

residue,  while  elimination  of  the  methyl  group  united  to  the  nitrogen  atom  or  of  the 
C02CH3  group  scarcely  affects  the  anaesthetic  properties.  On  the  other  hand,  almost  all 
the  aminohydroxybenzoic  esters  are  mild  local  ancesthetics  (Einhorn  and  Heinz,  1897),  e.g. 
ancesthesin  or  ethyl  p-aminobenzoate,  NH2'C6H4-CO2C2H5.  The  anaesthetic  characters 
of  these  substances  are  intensified  if,  in  place  of  NH2,  N(CH3)2  groups  are  present,  preferably 
joined  to  other  methyl  groups.  This  is  the  case,  for  instance,  in  : 

C6H5-C02X      /CH3  C6H5-C02X      /CH2-N(CH3)2 

^C^  and  )>C<( 

C2H/     XCH2-N(CH3)2  C2H/      XCH2-N(CH3)2 

Stovaine  Alipine 

prepared  by  Messrs.  Bayer  in  1905.  Both  of  these  are  less  poisonous  than  cocaine,  but  have 
not  its  property  of  contracting  the  blood-vessels.  They  are  therefore  mixed  with  adrenaline, 
which  shows  this  property  in  a  marked  degree  and  also  diminishes  the  toxicity  of  certain 
alkaloids,  especially  of  cocaine. 

NARCOTINE,  C22H2307N,  exists  to  the  extent  of  6  per  cent,  in  opium,  melts  at  126°, 
and  is  a  slightly  poisonous,  weak,  tertiary  base  containing  three  methoxyl  groups.  When 
hydrolysed,  narcotine  gives  Meconic  Anhydride,  C^H^O^,  and  Cotarnine,  C12H1303N, 
which  is  a  derivative  of  isoquinoline  (see  later),  and  with  bromine  gives  dibromopyridine. 

STRYCHNINE,  C21H22O2N2,  is  present,  with  Brucine,  C23H26O4N2,  and  Curarine,  in 
the  seeds  of  Strychnos  nux  vomica.  They  are  very  powerful  poisons,  which,  even  in  small 
doses,  cause  death,  accompanied  by  tetanic  muscular  contorsions  ;  curarine  is  used  as  an 
antidote  to  the  other  two  alkaloids.  Strychnine  melts  at  265°,  and  is  a  mono-acid  tertiary 
base  slightly  soluble  in  water  ;  it  gives  indole  and  quinoline  when  fused  with  potash 
and  /3-picoline  on  distillation  with  lime. 

QUININE,  C20H24O2N2.  The  bark  of  various  species  of  cinchona  has  yielded,  up  to 
the  present,  twenty-four  alkaloids,  the  most  important  being  quinine  and  Cinchonine, 


634 


ORGANIC    CHEMISTRY 


C19H22O2N2,  both  of  these  possessing  in  different  degrees  febrifugic  properties.  The  other 
alkaloids  include  Hydroquinine,  C20H26O2N2  ;  Cinchonidine,  C19H22ON2 ;  Hydro- 
cinchonidine,  CjgH^ON-j  ;  Quinidine,  C2oH24O2N2,  &c. 

Quinine  is  laevo- rotatory,  slightly  soluble  in  water  and  odourless  and  has  an  intensely 
bitter  taste  ;  it  melts  at  177°,  or,  when  crystallised  with  3H2O,  at  57°.  It  is  a  di-acid  base, 
containing  two  tertiary  nitrogen  atoms  capable  of  salt-formation  with  two  equivalents  of 
acid,  then  often  giving  aqueous  solutions  showing  blue  fluorescence  characteristic  of  quinine. 
It  contains  a  hydroxyl  and  a  methoxyl  group,  and  its  constitutional  formula,  although  not 
completely  established,  must  consist  of  two  cyclic  systems,  NC10H15(OH)  — NC9H5-OCH3, 
the  first  being  somewhat  analogous  to  tropine  (see  above)  and  the  second  representing 
5-methoxyquinoline,  which  can  be  obtained  by  fusing  quinine  with  potash.  After  pro- 
tracted investigation,  W.  Konigs  (1906-1907)  arrived  at  the  following  probable  structures 
for  cinchonine  and  quinine  : 

N- 


*^X12  (\J1LJ\J          ( 
1 

CH     C                                                       C 

/\/\                                       H2C  • 
HC       C       CH                                          \ 

^Hj  ^Ji2 

H2 
CH-CH  :  CH 

1        II        1                                                 CH 
HC       C      CH 

\/\7 

•      CH   N 

Cinchonine 


(OH)C    CH,,  CH2 

CH2 

H2C     I      CH-CH  :  CH2 

\l/ 
CH 


CH2 

CH    C 

/\/\ 
CH30-C       C      CH 

I        II        I 
HC       C       CH 

\/\/ 
CH     N 

Quinine 

Rabe  (1906-1907),  however,  proposed  for  cinchonine  the  formula  : 

CH2  — CH— CH— CH  :  CH2 


*/      CH2        dr2 

I     '          I 
>— C(OH)— N—  CH2 


which  is  in  harmony  with  the  Beckmann  oxime  reaction. 

Oxidation  of  quinine  gives,  among  other  products,  Quinic  Acid,  C9H5N(OCH3)-CO2H. 

To  combat  fever,  especially  malarial  fever,  use  is  made  of  the  normal  sulphate  of  qiiinine, 
(C20H2402N2)2,H2SO4,8H20  (from  alcohol  it  crystallises  with  2H20),  or  of  quinine  hydro- 
chloride,  C20H2402N2,HC1,2H2O,  which  is  far  more  readily  soluble  in  water. 

Quinine  bisulphate  or  acid  sulphate  contains  1  mol.sof  quinine  per  1  mol.  of  sulphuric 
acid. 

Quinine  is  extracted  from  the  finely  ground  bark  by  mixing  it  with  lime  and  extracting 
with  hot  mineral  oils  (paraffin  oil,  &c.)  of  high  boiling-point.  From  this  solution  the 
alkaloid  is  obtained  by  shaking  with  dilute  sulphuric  acid,  neutralisation  of  the  acid  solution 
with  sodium  carbonate  in  the  hot  resulting  in  the  crystallisation  of  most  of  the  quinine 


QUINOLINE  635 

as  sulphate  from  the  cold  solution,  the  other  alkaloids  remaining  dissolved.  From  the 
sulphate  the  quinine  is  liberated  by  means  of  ammonia. 

The  purification  of  quinine  is  not  easy  and  is  sometimes  effected  by  precipitating  it 
from  solution  as  tartrate  by  addition  of  Rochelle  salt. 

Statistics.  Quinine  bisulphate  costs  about  28s.  per  kilo  ;  the  sulphate  32*.  ;  and  the 
hydrochloride  40s.  Of  the  world's  output  of  cinchona  bark,  90  per  cent,  conies  from 
Java,  which  in  1900  exported  60,000  quintals,  and  in  each  year  from  1905-1909  more  than 
80,000  quintals  of  the  bark,  giving  6  to  6-5  per  cent,  of  quinine  sulphate. 

In  1898  Germany  imported  3537  tons  of  cinchona  bark,  worth  about  £128,000  ;  ii? 
1905  the  imports  amounted  to  2594  tons,  of  the  value  of  £168,000,  and  in  the  same  y eat 
Germany  exported  1404  quintals  of  quinine  and  its  salts,  of  the  value  of  £224,000,  and 
461  quintals  of  other  alkaloids,  of  the  value  of  £424,000  ;  in  1907  the  exports  were  1700 
quintals  and  in  1908  about  1500  quintals  at  22s.  per  kilo. 

England  imported  1080  tons  (£35,759)  of  cinchona  bark  in  1909,  1123  tons  (£39,520) 
in  1910,  and  1020  tons  (£37,169)  in  191],  while  the  imports  and  exports  of  quinint,  salts 
were  as  follow : 

Imports  Exports 

1909  .         .         .         „         .     £82,556  £55,065 

1910  .         \-       .         .         .       90,771  56,866 

1911  ...         .         .         .       98,056  75,080 

The  United  States  imported  1500  tons  (£52,200)  of  cinchona  and  similar  barks  in  1910 
and  1550  tons  (£55,000)  in  1911  ;  also  quinine  salts  and  alkaloids  to  the  value  of  £76,400 
in  1910  and  £95,400  in  1911. 

In  1904  Italy  imported  1627  quintals  (in  1908,  1384)  of  cinchona  bark  of  the  value  of 
£13,650.  In  1878,  at  the  time  of  the  Fabrica  Lombarda  of  quinine  in  Milan,  Italy  consumed 
10,000  kilos  of  quinine  (5000  furnished  by  the  Fabrica  Lombarda,  which  also  sent  20,000 
kilos,  at  £28  to  £32  per  kilo,  to  Russia).  After  1902,  in  consequence  of  the  valuable  studies 
of  Ross,  Grassi,  and  Celli  on  malaria  (a  disease  which  is  transmitted  by  the  Anopheles 
mosquito  and  against  which  a  couple  of  small  doses  of  quinine  per  week  render  one  immune), 
a  Government  monopoly  was  instituted  to  distribute  quinine  cheaply  or  gratuitously  in 
the  malarial  centres.  The  beneficial  results  obtained  are  shown  by  the  following  figures : 
in  1902-1903  the  consumption  of  quinine  distributed  in  this  way  was  2242  kilos  ;  in 
1903-1904  7234  kilos  ;  in  1904-1905  14,071  kilos  ;  in  1905-1906  18,712  kilos,  and  in 
1906-1907  21,723  kilos.  The  mortality  from  malaria,  which  was  21,000  in  1887  and  15,865 
in  1900,  fell  to  9908  in  1902,  to  8513  in  1903,  to  8501  in  1904,  to  7838  in  1905,  and  to 
4690  in  1906.  In  addition  to  these  advantages,  the  Italian  Government  made  in  1906 
a  profit  of  more  than  £1400  from  its  commerce  in  quinine.  There  is  now  scarcely 
any  quinine  made  in  Italy,  but  the  imports  amount  to  30,000  to  40,000  kilos,  20,000  to 
30,000  kilos  being  converted  into  pastilles  and  sold  practically  at  cost  price  to  combat 
malaria. 


5.   QUINOLINE  AND  ITS  DERIVATIVES 

Quinoline  and  pyridine  are  related  in  the  same  way  as  naphthalene  and 
benzene. 

CH  CH 


QUINOLINE,  C9H7N,  i.e.  Hc^     °  'isa 

CH 

highly  refractive,  colourless  liquid  of   peculiar  odour  and  is  found  in  bone 
tar  and  also  in  coal-tar,  but  is  now  prepared  in  the  pure  state  by  Skraup's 
synthesis. 

It  is  slightly  soluble  in  water,  has  the  sp.  gr.  1-1081  at  0°,  boils  at  236° 
and  functions  as  a  tertiary  base  (the  nitrogen  not  being  combined  with  nitrogen). 
With  acids  it  forms  salts,  e.g.  the  bichromate  (C9H7N)2H2Cro07. 


636 


ORGANIC    CHEMISTRY 


Its  constitution  is  deduced  from  the  following  syntheses  : 

(1)  By  the  interaction  of  Allylaniline  and  Pb02  at  a  red  heat : 


H    CH 


0      =    2H0 


H    NH 


N 


(2)  Skraup  obtained  it  by  heating  aniline  with  glycerol,  sulphuric  acid, 
and  nitrobenzene ;  in  this  way  acrolei'n  is  formed,  which  then  gives  Acroleih- 
aniline,  C6H6-N  :  CH-CH  :  CH2.     The  nitrobenzene  acts  purely  as  an  oxi- 
dising agent  and  can  be  replaced  by  As203. 

(3)  o-Nitrocinnamaldehyde  on   reduction  gives    o-aminocinnamaldehyde, 
which  loses  1  mol.  H20  and  yields  quinoline.  the  fact  that  the  latter  is  an  ortho- 
derivative  of  benzene  being  thus  proved  : 


H  —  H2°    = 


When  quinoline  is  oxidised,  the  benzene  nucleus  is  attacked  first,  with 

^COOH 


formation  of  a  dibasic   Quinolinic  Acid, 


COOH 


,   which   gives   pyridine, 


N 


,  when  distilled  with  lime.    Hence,  as  was  suggested  Jong  ago  byKorner, 


N 

quinoline  contains  a  benzene  and  also  a  pyridine  nucleus.  It  is  analogous 
to  naphthalene,  one  u-CH  group  being  replaced  by  a  nitrogen  atom.  .That  the 
linkings  in  quinoline  are,  at  least  in  part,  olefinic  double  bonds  is  shown  by  the 
behaviour  of  this  compound  to  ozone. 

Quinoline  forms  many  isomeric  derivatives,  seven  monosubstitutecl, 
twenty-one  disubstituted,  and  still  more  trisubstituted  compounds  being 
possible. 

The  positions  of  the  replaceable  hydrogen  atoms  are  indicated  by  numbers 
or  by  the  letters  «,  /3,  and  y  for  the  pyridine  nucleus  and  o,  m,  p,  a  (ortho-, 
meta-,  para-,  ara-)  for  the  benzene  nucleus. 

The  constitution  of  quinoline  derivatives  can  be  determined  by  means  of 
the  general  synthesis  of  Skraup,  variously  substituted  anilines  with  the  sub- 
stituents  in  the  benzene  nucleus  being  used  ;  or  often  by  oxidation,  which 
usually  attacks  the  benzene  nucleus  and  not  the  pyridine  nucleus,  so  that  it  is 
easily  ascertained  whether  the  substituent  is  in  the  one  or  the  other  nucleus. 

The  sulpho-acids  (or  sulphonic  acids)  of  quinoline,  when  fused  with  KOH,  give  hydroxy- 
quinolines,  and  these,  on  being  heated  with  KCN,  form  cyanoquinolines,  which  are  converted 
by  hydrolysis  into  the  corresponding  quinolinecarboxylic  acids— those  containing  the 
carboxyl  in  the  benzene  nucleus  are  called  quinolinebenzocarboxylic  acids.  Oxidation  of 
cinchonine  gives  cinchonic  acid,  C9H6N-CO2H  (m.pt.  254°),  which  is  quinoline-y-carboxylic 
acid,  and  from  this  is  derived  quinic  acid  (see  above],  C9H5N(OCH3)-C02H  (p  ;  y),  con- 
sisting of  yellow  prisms  melting  at  280°.  When  acridine  is  oxidised  it  yields  quinoline- 
°- :  /3-dicarboxylic  acid  or  acridic  acid. 


QUINOLINE    DERIVATIVES 


63? 


Carbostyril  is  2 -Hydroxy  quinoline, 


,  and  has  the  character  of  the  phenols, 


OH 


dissolving  in  alkali  and  being  reprecipitated  by  C02,  &c. 

When  quinoline  is  reduced  with  nascent  hydrogen,  this  unites  with  the  nitrogenated 

H2 


nucleus,  forming  Tetrahydroquinoline,  C9HnN,  or 


,   which    behaves  as  a 


\/\/  2 

NH 

secondary  aromatic  amine  (^>NH). 

If  the  reduction  is  pushed  further,  the  hydrogen  is  added  also  to  the  benzene  nucleus, 
forming  decahydroquinoline,  C9H17N,  which  behaves  like  an  aromatic  amine. 

Quinaldine  or  a-Methylquinoline,  CjoHgN,  is  found  in  coal-tar  and  boils  at  246°  ;  with 
phthalic  anhydride  it  gives  a  fine  colouring- matter,  Quinoline  Yellow,  C10H7N(CO)2C6H4. 

When  quinoline  is  heated  with  metallic  sodium  it  gives  diquinolyl,  CgHeN-CgHgN, 
analogous  to  dipyridyl  and  diphenyl.  Polymerisation  of  quinoline  yields  diquinoline, 
(C9H7N)2,  crystallising  in  yellow  needles. 

METHOXYQUINOLINE,  C9Ht;N-OCH3,  corresponding  with  anisole,  resembles 
quinoline;  among  its  derivatives  are  the  antipyretic,  Thalline,  C9H10N-OCH3,  and 
Analgen  (o-ethoxy-a-benzoylaminoquinoline). 


ISOQUINOLINE,  C9H7N  or 


\  I  /\  I  / 


,  is  a  colourless  liquid  boiling  at  237°, 


melting  at  21°  and  forming  a  slightly  soluble  sulphate. 

It  is  obtained  from  tar  and  also  synthetically  by  heating  the  ammonium   salt  of 
homophthalic  acid : 

xCH2-COONH4  CH2-CO 

C6H4<^  ,    =     2H20      +     NH3      +     C6H4/          |    , 

XCOONH4  \CO •  NH 

riTi     rr<i  Homophthalimide 

/Ori2  •  VA^ig 

which  with  POC13  gives  C6H4\'  |       ,  and  elimination   of   2HC1  from  this  yields 

XCC12-NH 

<a 

,  i.e.  dichloroisoquinoline. 


When  oxidised  it  gives  phthalic  acid  and  CinchonWdnie  Acid,  C6H3N(C02H).j  (a 
pyridine  derivative). 

Since  it  does  not  fix  ozone,  it  must  be  assumed,  contrary  to  the  former  view,  that  it  does 
not  contain  olefinic  double  linkings,  but  that  centric  bonds  are  probably  present  in  both 
nuclei  (Molinari,  1907). 

Other  condensed  nuclei,  similar  to  quinoline,  are  as  follow : 


,0  •  CH 

CHROMONE,  C6H4  /          ||    ,  of  which  the  /3-methyl-derivative, 
\CO  •  CH 


m.pt.  71°,  is  well  known. 
FLAVONE,  the  phen 
occurs  as  hydroxy-derivatives  in  many  glticosides,  to  which  it  imparts  the  yellow  coloration, 


/O  •  C  •  C6H6 

FLAVONE,  the  phenyl- derivative   of  chrdtftone,  C6H4/  ,  melts  at  97°,  and 

\CO-CH 


638  ORGANIC    CHEMISTRY 

Thus  it  occurs  in  quercetin  (or  flavin),  which  is  a  pentahydroxyflavene,  while  with  isodulcitol 
it  forms  the  glucoside  Quercitrin,  C2iH23012,  obtained  from  tea,  hops,  and  the  bark  of 
Quercus  tinctoria  (morin  is  an  isomeride  of  quercetin,  and  is  found  in  Madura  tinctoria). 
Chrysin,  C15Hj  004,  is  a  dihydroxyflavone  found  in  poplar  buds  ;  Luteolin,  C^HjoO^HaO, 
is  a  tetrahydroxyflavone,  and  forms  the  colouring-matter  of  Reseda  luteola,  while  apigenin 
is  a  glucoside  of  trihydroxyflavone,  and  is  found  in  parsley  and  celery. 

Of  numerous  dyestuffs  formed  by  the  condensation  of  heterocyclic  groups,  mention 
will  be  made  later  in  the  chapter  on  colouring-matters,  but  a  group  of  substances  with 
heterocyclic  nuclei  and  intimately  connected  with  indigo  will  be  considered  here. 

WTT 

ISATIN,  C6H4<^pp.^>CO,  forms  reddish  yellow  prisms  soluble  in  alcohol  and  in  hot 

Water,  and  may  be  regarded  as  the  lactam  (see  p.  355)  of  Isatinic  Acid,  NH2  •  C6H4  •  CO  •  COOH. 
It  is  obtained  from  o-nitrobenzoylformic  acid  (see  later,  Indole),  by  oxidising  indigo  with 

NK 

nitric  acid,  &c.     It  dissolves  in  KOH,  giving  first  a  violet  colour  (C6H4<^       ^>CO),  while 

TU-TT 

in  the  hot  it  yields  potassium  isatinate,  CeH^-c^,,,  2  „  „.    Oxidation  of  isatin  with  chromic 

OU  '  V^UjjIY 

xNH-CO 
acid  gives  rise  to  Isatic  Acid  (anhydride  of  anthranilcarboxylic  acid),  C6H4^ 

XX)  -O 

/co\ 

From  PseUdoisatin,  C6H4('         ^C-OH  (which  would  be  a  lacttm)  is   derived  the 


methyl  ether  or  Methylpseudoisatin,  C6H4('         V>OCH3  (red  powder).     Methylisatin, 

\N<T 

,  is  also  known, 

DIOXYINDOLE,  C6H4<^Tu        '>CO,  is  formed  by  reducing  isatin  with  zinc  and 
W  il'  -- 

HC1  and  readily  gives  isatin  again  on  oxidation.  It  is  the  internal  anhydride  of  o-amino- 
mandelic  acid,  and  exhibits  both  basic  and  acid  properties.  It  crystallises  in  colourless 
prisms,  melting  at  180°. 

OXINDOLE,  C6H4<<r,TT  ^>CO,  acts  both  as  an  acid  and  as  a  base,  and  hence  dissolves 

in  alkali  and  in  HC1.  It  is  the  lactam  of  o-aminophenylacetic  acid,  and  can,  indeed,  be 
obtained  by  reducing  o-nitrophenylacetic  acid.  It  forms  colourless  needles,  m.pt.  120°, 
and  forms  dioxyindole  on  oxidation. 

NH- 
INDOXYL,  C6H4<^  ^CH'  is  isomeric  with  tne  preceding  compound,  and  is 

x  C(OH)  r 

formed  by  fusing  indigo  with  KOH  or  by  the  elimination  of  CO2  from  indoxylic  acid  or 
indophore'. 

It  occurs  in  the  urine  of  herbivorous  animals  in  the  form  of  Potassium  Indoxylsulphate, 

NH 

C8H6N'0'SO3K(?'nrfica»  of  the  urine).     Derivatives  of  Pseudoindoxyl,  C6H4<_~  ^>CH2, 

are  also  known. 

NH-X 
SKATOLE,  C6H4<'  ^**,  is  formed  during  the  putrefaction  of  protein  or  by 


fusing  the  latter  with  KOH,  and  is  hence  found  in  the  faeces  ;    it  is  found  in  the  African 
Viverra  civetta.     It  forms  white  scales,  m.pt.  95°,  with  an  intense  fecal  odour. 

/NH\ 
INDOLE,  C6H4('          ^C**,  is  of  importance  owing  to  its  intimate  connection  with 

\CH^ 

indigo.     By  treating  o-nitrobenzoyl  chloride  with  AgCN,  the  nitrile  is  obtained  and  this, 
on  hydrolysis,  gives  o-nitrobenzoylformic  acid  : 

COC1(1)  „      CO-CN  CO-COOH. 

LeH*<N02  (2)  C6H*<N02  Cf5H4<K02 


INDIGO 

this  acid,  on  reduction,  gives  the  amine,  which  loses  1  mol.  H20,  forming  Isatin  : 


,00-COOH 
C6H4<^  =  H20 


C6H4 


XXK 


\  N  ' 

Isatin 


Indole  is  obtained  by  distilling  oxindole  with  zinc  dust  and  by  various  synthetical 
processes  (see  later,  Indigo) ;  it  is  formed  in  the  pancreatic  putrefaction  of  protein  or  on 
fusion  of  this  with  KOH.  In  the  impure  state  it  has  a  fecal  odour,  but  when  pure  and 
highly  diluted  it  smells  like  flowers,  and  is  hence  used  in  perfumery.  It  forms  shining 
scales  which  melt  at  52°,  are  volatile  in  steam,  and  with  ozone  give  indigo. 

With  sodium  bisulphite  it  forms  a  crystalline  compound,  and  with  nitrous  acid  a  red 
precipitate  ;  it  imparts  a  red  colour  to  a  pine  shaving  moistened  with  HC1.  It  may  be 
regarded  as  formed  by  the  condensation  of  1  mol.  of  benzene  and  1  mol.  of  pyrrole : 


It  forms  numerous  derivatives  with 


N 


substituents  in  the  benzene  or  pyrrole  nucleus,  the 
two  CH  groups  near  the  NH  being  termed  a  and  /3. 


INDAZOLE,  C6H4 


N,  is  a  weak   base 


FIG.  421. 


prepared  by  decomposing  the  diazo  -compound  of 
p-nitro-o-toluidine  with  acetic  acid  in  the  hot  and 
then  eliminating  the  N02  group.  ^ 

INDIGO,  C16H10O2N,  is  a  very  stable, 
natural,  blue  colouring-matter,  which  was 
in  use  in  the  Far  East  in  the  most  remote 
times,  and  was  bartered  to  the  Egyptians  — 
mummies  of  the  Eighteenth  Dynasty  (1580 
years  B.C.)  are  found  with  wrappings  coloured 
with  indigo  —  then  to  Greece,  and  later  to 
Italy.  Until  the  middle  of  the  nineteenth 
century  the  trade  in  indigo  remained  a 
monopoly  of  the  Dutch. 

It  is  extracted  from  the  branches  and 
leaves  (of  a  yellowish  green  colour)  of  Indi- 
gofera  tinctoria  (Fig.  421),  which  grows  very  readily  in  tropical  countries 
and  is  extensively  cultivated  in  India,  Java,  China,  &c.,  being  sown  in  the 
spring  and  cut  two  or  three  times  a  year  before  flowering.1  At  one  time,  'ft 
was  extracted  also  in  Europe  (Hungary,  Thuringia,  &c.)  from  woad  (I  satis 
tinctoria,  Fig.  422),  where,  however,  it  occurs  only  in  the  leaves  and  in  smaller 
quantity.  There  are  several  varieties  of  Indigofera  (tinctoria,  disperma,  anil, 

1  Indigo  belongs  to  the  leguminous  plants,  and  is  hence  capable  of  enriching  the  soil  with  nitrogenous  products 
owing  to  the  action  of  bacteria  which  fix  atmospheric  nitrogen  (see  vol.  i,  p.  301).  It  has  therefore  been  proposed 
to  plant  indigo  in  rotation  with  sugar-cane,  especially  in  soils  which  have  been  exhausted  by  the  latter.  At  every 
cutting  25  to  30  quintals  of  indigo  plants  are  obtainable  per  hectare  and  5  to  6  kilos  of  60  per  cent,  indigo  for  every 
ton  of  plants. 

In  India  indigo  is  sown  in  February  or  March  in  well-tilled  land  at  the  rate  of  about  14  kilos  of  seed  per  hectare. 
After  three  months  the  flowering  stage  is  reached,  the  plants,  which  then  contain  the  maximum  of  colouring- 
matter,  being  cut  off  close  to  the  ground,  tied  in  bundles,  and  despatched  immediately  to  the  factory  to  be 
extracted.  A  second  cutting  in  September  gives  a  smaller  quantity  of  indigo. 

The  cultivation  of  indigo  reached  its  greatest  extent  in  1896-1897  with  a  total  area  of  640,000  hectares,  one-third 
in  Bengal,  one-fourth  in  the  North-  West  Provinces,  one-fourth  in  Madras,  and  one-twelfth  in  the  Punjab.  In 
1880  India  contained  2800  indigo  factories  and  6000  works  employing  primitive  methods  of  extraction,  the  total 
number  of  persons  employed,  exclusive  of  agricultural  labourers,  being  360,000.  After  the  appearance  of  artificial 
indigo,  the  area  under  indigo  steadily  diminished,  being  only  180,000  hectares  in  1906-1907. 

There  is  a  tendency  in  India  to  extend  the  cultivation  only  on  the  most  suitable  soils.,  and  to  abandon  those  less 
fitted,  and  in  1908-1909  the  area  under>ndigo  fell  to  115,000  hectares  ;  in  1909-1910  there  was  a  slight  increase  to 
117,450  hectares. 


640 


ORGANIC    CHEMISTRY 


argentea,  and  others  of  less  importance).  They  are  herbaceous  shrubs  50  to 
100  cm.  in  height,  covered  with  silky  hairs,  with  pinnate  leaves  and  many 
small  leaves. 

From  the  results  of  tests  made  at  Calcutta  it  would  seem  that  Indigofera 
leptostachya,  cultivated  in  Java  but  indigenous  to  Natal,  is  better  in  every 
respect  than  Indigofera  tinctoria,  while  it  lasts  four  to  five  years.  Still  better 
results  seem  to  be  given  by  Indigofera  erecta. 

In  order  that  the  indigo  may  be  extracted  from  the  cut  plants,  it  is  necessary  that  the 
glucoside  they  contain  (indicari) — consisting  of  a  compound  of  glucose  with  indigotin 
(the  leuco-base  of  indigo) — be  decomposed  by  fermentation  in  large  vessels  with  water. 
After  10  to  14  hours  the  glucose  is  fermented,  while  the  indigo,  owing  to  the  presence  of 
ammonia,  forms  a  yellowish  solution.  The  liquid  is  transferred  to  deep  vats,  where  it  is 
subjected  to  "  beating  "  for  2  to  3  hours  with  wooden  paddles  or  wheels,  or  to  "  blowing  " 
by  means  of  a  current  of  air.  The  oxidation  thus  effected  causes  the  separation  of  the 

indigo  in  flocks,  which  are  removed  by  decantation 

after  3  to  4  hours  : 


C(OH) 
NH 


NH 


C6H4 


Indigotin 
/C(OHk 

2C6H4^  )CH    — > 

\  NH   / 

Indoxyl 

r*n  pn 

/V>W   v  s\j\J   \ 

C\P  .  fur  \ri  TI 

6"4\  /V    :    ^\  /^G^i 

Indigo  blue 

The  5  per  cent,  indigo  paste  separated  by  decanta- 
tion is  passed  through  sieves  to  remove  fragments  of 
the  plants  and  is  then  boiled  by  means  of  steam  for 
15  minutes  in  order  to  sterilise  the  mass — which 
would  otherwise  undergo  change — and  to  eliminate 
FIG.  422.  part  of  the  brown  matter  and  to  effect  better  sepa- 

ration of  the  particles  of  indigo.     These  then  deposit 

more  easily  and  are  collected  on  a  large  cloth  filter,  the  first  liquid  passing  through  being 
returned  to  the  filter  until  it  comes  through  faint  red  ;  the  8  to  12  per  cent,  paste  thus 
obtained  is  pressed  in  primitive  presses.  The  large  cakes  thus  formed  contain  about 
80  per  cent,  of  water  and  are  cut  into  small  cubes,  which  are  arranged  on  grids,  dried  in 
the  air  for  two  or  three  months  and  placed  on  the  market  in  boxes  holding  50  to  140  kilos 
under  the  name  of  cakes.  During  the  drying,  these  cakes  evolve  ammonia  and  become 
covered  with  mould,  which  is  finally  removed  with  brushes.  The  yield  of  indigo  is  about 
0-2  per  cent,  on  the  weight  of  the  green  plant  or  2  per  cent,  on  that  of  the  dry  plant. 

To  combat  the  competition  of  artificial  indigo,  various  improvements  have  been  intro- 
duced during  recent  years  into  the  methods  of  cultivation,  manuring,  and  extraction  ; 
attention  may  be  directed  to  the  rational  fermentation  with  suitable  enzymes  (oxydases) 
proposed  by  Calmette  and  others  (Fr.  Pata.  300,826  and  302,169). 

The  indigo-content  of  the  cakes  varies  considerably,  some  of  those  on  the  market 
containing  only  20  per  cent,  and  others  as  much  as  90  per  cent.  It  hence  becomes  necessary 
to  determine  the  value  of  any  sample  on  the  basis  of  the  proportion  of  pure  indigo  ascer- 
tained by  exact  analysis.1  According  to  Fr.  Pat.  323,036  an  increased  yield  and  an 

1  Analysis  of  Commercial  Indigo.  Commercial  indigo  from  Bengal  contains,  on  an  average,  60  per  cent, 
of  indigotin  ;  that  of  Madras,  30  to  50  per  cent. ;  that  of  Java,  72  to  82  per  cent. ;  that  of  Guatemala,  about 
40  per  cent. ;  that  of  Martinique,  60  to  70  per  cent. ;  and  that  of  Cambay,  China,  and  Tonkin,  8  to  15  per  cent. 

Indtgotin  can  be  estimated  as  follows  :  1  grm.  of  well-dried  indigo  is  mixed  (in  a  bottle  with  a  ground  stopper) 

fithlO  grms.  of  garnets  or  glass  beads  and  20  c.c.  of  sulphuric  acid  mixture  (composed  of  3  parts  of  concentrated 

sulphuric  acid  and  1  part  of  oleum  containing  20  per  cent,  of  free  S08).    The  mass  is  thoroughly  mixed  and  is 

terwards  shaken  occasionally  over  a  period  of  12  hours  or  so,  until  solution  is  complete,  the  whole  being  then 

poured  carefully  into  cold  water  and  the  bottle  thoroughly  rinsed  out.    The  aqueous  solution  is  boiled  for  10  minutes 

ana  altered,  the  filter  being  washed  with  hot  Water  until  the  washings  become  colourless  and  the  filtrate  then  mods 


INDIGO  641 

improved  product  are  obtained  by  macerating  the  fresh  plants  in  presence  of  tannin 
materials  which  leave  only  the  indigo  undissolved. 

The  cakes  of  indigo  are  blackish  blue  in  colour  and  give  a  fracture  showing  a  bronzy 
reflection.  Natural  indigo  always  contains,  besides  indigotin,  other  substances  and  colour- 
ing-matters (such  as  indigo  gum,  indigo  brown  and  red,  &c.)  which  affect  the  tint,  sometimes 
favourably. 

A  good  Bengal  indigo  gave,  on  analysis,  62  per  cent,  of  indigo  blue,  7-3  per  cent,  of 
indigo  red,  4-7  per  cent,  of  indigo  brown,  1-5  per  cent,  of  indigo  gum,  6  per  cent,  of  water, 
and  19  per  cent,  of  mineral  matter. 

Pure  or  refined  indigo  is  obtained  in  various  ways,  e.g.  the  crude  indigo  is  treated  with 
a  mixture  of  concentrated  acetic  and  sulphuric  acids,  the  indigo  alone  passing  into  solution 
as  sulphate,  which  is  decomposed  after  filtration  by  excess  of  water,  this  precipitating  pure 
indigo  or  indigotin.  In  order  to  avoid  dilution  with  water  and  loss  of  acid,  it  has  been 
proposed  to  separate  the  sulphuric  acid  directly  by  addition  of  calcined  sodium  sulphate, 
which  transforms  it  into  bisulphate  ;  the  acetic  acid  is  then  distilled  off  and  the  bisulphate 
removed  together  with  a  little  water.  According  to  Ger.  Pat.  134,139  pure  indigo  is  extracted 
from  the  crude  product  by  means  of  hot,  crude  pyridine.  To  purify  artificial  indigo,  it  is 
heated,  according  to  Ger.  Pat.  179,351,  at  200°  to  270°,  at  which  temperature  it  does  not 
sublime  or  decompose,  while  the  indigo  red  and  other  impurities  are  destroyed,  leaving  an 
indigo  highly  valued  for  its  fine  bronzing. 

Of  some  interest  is  colloidal  indigo,  which  behaves  like  dissolved  indigo,  and  has  been 
recently  prepared  by  Mohlau  by  heating,  out  of  contact  with  the  air,  a  suspension  of  indigo 
in  an  aqueous  solution  of  alkali  and  sodium  hydrosulphite,  the  liquid  being  treated,  after 
cooling,  with  protalbinic  acid  (obtained  by  Mohlau  by  the  alkah'ne  hydrolysis  of  protein 
and  subsequent  dialysis  ;  this  acid  has  the  power  of  precipitating  various  metals  in  a  colloidal 
state  from  their  salts).  Addition  of  hydrogen  peroxide  to  the  filtered  liquid  gives  indigo 
blue  in  the  colloidal  condition,  which  is  retained  even  after  evaporation. 

Properties.  Pure  indigo  forms  a  dark  blue  powder  which,  when  rubbed, 
gives  a  metallic,  coppery  reflection.  It  sublimes  at  about  170°,  giving  red 
vapour  and  forming  copper-red,  shining  prisms.  It  is  insoluble  in  water, 
alcohol,  ether,  alkali,  or  acid,  and  dissolves  only  slightly,  even  in  the  hot, 
in  amyl  alcohol,  chloroform,  phenol,  carbon  disulphide,  pure  acetic  acid,  nitro- 
benzene, aniline  or  melted  paraffin.  It  has  neither  odour  nor  taste  and  is 
indeed  an  almost  completely  indifferent  substance  ;  this  explains  why,  although 
materials  have  been  dyed  from  time  immemorial  in  the  Far  East,  in  Europe 
no  process  for  dyeing  textile  fibres  was  discovered  for  so  many  centuries — until 
the  sixteenth. 

The  portion  soluble  in  hot  aniline  colours  this  blue  but  colours  fused  paraffin 
purple-red  ;  from  these  solutions,  rhombic  crystals  showing  marked  dichroism 
separate  on  cooling. 

From  hot  oil  of  turpentine  indigo  crystallises  in  blue  plates. 

Concentrated  sulphuric  acid  converts  it  in  the  hot  into  a  monosulphonic 
derivative,  soluble  in  water  but  insoluble  in  salt  solutions.  With  fuming 
sulphuric  acid  it  forms  the  disulphonic  compound,  which  gives  more  soluble 
salts,  the  sodium  salt  being  sold  as  a  paste  under  the  name  of  indigo-carmine, 
this  dyeing  wool  like  an  acid  aniline  dye. 

When  dry  distilled,  indigo  gives  aniline  and  other  aromatic  compounds. 

up  to  a  litre.  Fifty  cubic  centimetres  of  this  solution  are  mixed  with  900  c.c.  of  distilled  water,  and  the  liquid 
titrated  with  0-05  per  cent,  potassium  permanganate  solution  until  the  blue  colour  becomes  golden  yellow  without 
green  reflection.  In  order  to  accustom  the  eye  to  this  end-point,  which  is  not  sharp,  it  is  advisable  to  make  a  com- 
parative test  with  pure  indigo  of  known  strength ;  1  c.c.  of  the  permanganate  solution  corresponds  with  about 
0-00125  grm.  of  indigotin.  In  order  to  prepare  pure  100  per  cent,  indigo  for  purposes  of  comparison,  10  grins,  of 
pure,  powdered  artificial  indigo  (98  per  cent.)  marked  B.A.S.P.  or  M.L.B.)  are  treated  in  a  beaker  with  120  grms. 
of  caustic  soda  solution  (sp.  gr.  1-21),  330  grms.  of  concentrated  sodium  hydrosulphite  solution  and  100  grms.  of 
water  (or,  if  50  grms.  of  20  per  cent,  indigo  paste  are  taken,  only  60  grms.  of  water  are  added),  the  mixture  being 
heated  on  a  water-bath  at  40°  to  50°  with  occasional  shaking  and  the  air  being  gradually  expelled  from  the  beaker 
by  means  of  a  current  of  coal-gas.  When  solution  is  complete,  the  liquid  is  rapidly  filtered  and  a  current  of  air 
passed  into  the  yellow  or  greenish  filtrate.  The  precipitated  indigo  is  collected  on  a  hardened  filter  and  washed 
first  with  hot  water,  then  with  hot  dilute  hydrochloric  acid  (30  c.c.  of  the  concentrated  acid  diluted  to  a  litre), 
next  with  water  again,  and  repeatedly  with  alcohol  and  with  alcohol  and  ether.  When  dried  at  101°  to  110° 
until  of  constant  weight,  the  product  represents  pure  100'per  cent,  indigo.. 

n  41 


ORGANIC    CHEMISTRY 

Energetic  oxidising  agents  (nitric  or  chromic  acid  or  permanganate)  decolorise 
it  more  or  less  rapidly,  converting  it  into  isatin.  Chlorine,  bromine,  and 
iodine  give  halogenated  derivatives  of  isatin. 

The  white  indigotin,  which  is  the  leuco-base  of  indigo  blue,  is  obtained  from 
the  latter  in  a  soluble  form,  by  the  action  of  alkaline  reducing  agents  (sodium 
amalgam,  ferrous  sulphate,  hypophosphorous  or  hydrosulphurous  acid, 
glucose,  gallic  acid,  &c.)  or  enzymes.  When  heated  with  acid,  the  greenish 
yellow  alkaline  solution  deposits  indigotin  white,  which  is  readily  converted 
into  the  blue  form  by  the  oxygen  of  the  air. 

Indigo  may  be  regarded  as  a  substantive  dye  which  colours  both  animal 
and  vegetable  fibres  without  a  mordant.  It  is  first  reduced  in  the  vats  by  means 
of  enzymes  in  presence  of  sugar,  urine,  zinc,  arsenic,  or  reducing  salts  (sulphites, 
hydrosulphites),  thus  becoming  decolorised,  soluble  in  alkali  and  capable  of 
impregnating  textile  fibres,  on  which  it  becomes  firmly  fixed  when  rendered 
insoluble  by  the  action  of  atmospheric  oxygen. 

In  1890  the  German  Government  permitted  alizarin  blue  to  be  used  for 
dyeing  part  of  the  cloth  for  military  uniforms,  these  having  been  previously 
coloured  exclusively  with  indigo. 

The  first  efforts  to  ascertain  the  chemical  nature  of  indigo  were  those  of  Erdmann 
and  of  Laurent,  who  simultaneously  (in  1841)  obtained  isatin  by  oxidising  indigo  with 
nitric  acid.  In  1848  Fritzsche  obtained  aniline  by  distilling  indigo  with  caustic  potash  ; 
Baeyer  and  Knop,  in  1865,  reduced  indigo  to  dioxyindole,  oxindole,  and  indole,  the  last 
of  these  being  prepared  synthetically  by  Baeyer  and  Emmerling  in  1869  from  o-nitro- 
cinnamic  acid.  In  1870  Engler  and  Emmerling  effected  the  first  complete  synthesis  of 
indigo  by  heating  o-nitroacetophenone  with  lime  and  zinc  dust,  and  in  1874  Nencki  pre- 
pared indigo  by  oxidising  indole  with  ozone. 

In  an  interesting  series  of  studies  extending  from  1870  to  1878  Baeyer  and  his  pupils 
established  the  constitution  of,  and  synthesised,  oxindole,  transforming  it  into  isatin, 
and  the  latter,  in  various  ways,  into  indigo.  The  new  complete  synthesis  effected  by 
Baeyer  in  1880-1882  firmly  established  the  structure  of  the  indigo  molecule. 

Of  the  new  syntheses  of  indigo  following  that  of  Baeyer  —  which,  in  spite  of  costly 
attempts,  could  not  be  rendered  capable  of  industrial  application  —  the  most  important 
from  a  practical  point  of  view  is  that  of  Heumann  (1890),  in  which  fusion  of  phenylglycine- 
o-carboxylic  acid  with  alkali  is  succeeded  by  oxidation. 

The  starting-point  and  the  various  intermediate  products  of  Baeyer  's  1880  synthesis 
of  indigo  are  as  follow  : 

P  TT     JUH2-CO2H  CH2  _^C(:  NOH) 

Mi4<NQ  —  >     CeH^^jj^-U.        —  >      C6H4<_  NH  _ 

o-Nitrophenylacetic  acid  Oxindole  Isatoxime 


Amino-oxindole  Isatin  Isatin  chloride 

CO  CO 

C6H4<NH>C  :  C< 

Indigo 

Baeyer's  other  synthesis,  which  was  tried  on  an  industrial  scale  by  the  Badische  Anilin- 
und  Soda-Fabrik  of  Ludwigshafen  in  1882,  and  gave  a  yield  of  60  per  cent.,  started  from 
benzaldehyde,  the  product  of  the  interaction  of  benzylidene  chloride  and  sodium  acetate 
being  nitrated  (and  subsequently  esterified)  and  a  mixture  of  70  per  cent,  of  o-nitrocinnamic 
acid  and  30  per  cent,  of  p-nitrocinnamic  acid  thus  obtained.  After  removal  of  the  latter, 
the  former  is  converted  into  the  dibromide,  which,  with  alcoholic  potash,  loses  2HBr  and 
forms  o-nitrophenylpropiolic  acid,  this  giving  indigo  when  heated  with  alkali  and  glucose  : 

CH  :  CH-C02H  C  :  C-C02H  CO 

^o^^NOg  Le    4<-N02  C6H4<N 

O-Wtrocinnamie  acid  o-Jf  itrophenylpropiojic  acicl  Indigo 


SYNTHESES    OF    INDIGO 


643 


Owing  to  the  high  price  of  o-nitrophenylpropiolic  acid,  this  artificial  indigo  is  used  only 
for  printing  textiles. 

In  1882,  by  means  of  a  new  and  theoretically  elegant  synthesis,  Baeyer  and  Drewsen 
succeeded  in  raising  the  yield  to  70  per  cent.  ;  o-nitrobenzaldehyde  and  acetone  were 
condensed  in  presence  of  caustic  soda,  indigo  being  formed  as  follows  : 

f    2CH3-CO-CH3    =    2C6H4<^(OH)'CH2'CO'CH3     =• 


o-Xitrobenxaldehyde 


Acetone 


2H20   +  2CH3-C02H 


Indigo 


In  printing,  the  synthesis  takes  place  directly  on  the  textile,  the  acetone  being  rendered 
soluble  by  conversion  into  the  bisulphite  compound  (Kalle's  salt).  The  industrial  prepara- 
tion of  o-nitrobenzaldehyde  presented,  however,  a  serious  disadvantage,  the  direct  nitration 
of  benzaldehyde  yielding  a  considerable  proportion  of  the  unusable  m-nitrobenzaldehyde  ; 
while,  starting  from  benzil,  the  p-nitro-compound  is  obtained.  A  happy  solution  of  this 
difficulty  was  found  in  the  preparation  of  o-nitro toluene  directly  from  toluene  (only 
40  per  cent,  of  p-nitrotoluene  is  formed),  oxidation  with  manganese  dioxide  and  su'phuric 
acid  then  giving  a  good  yield  of  o-nitrobenzaldehyde.  To  the  general  application  of  thn 
process  were  opposed  a  number  of  difficulties.  In  order  that  the  artificial  indigo  might 
displace  the  natural  product,  the  annual  consumption  of  which  was  about  5,000,000  to 
6,000,000  of  kilos  (100  per  cent.),  it  was  necessary  that  there  should  be  on  the  market  a 
sufficient  quantity  of  raw  material  (toluene)  at  a  reasonable  price.  It  was  found  that, 
even  although  the  use  of  modern  metallurgical  coke  furnaces  (see  vol.  i,  p.  366,  and  this 
vol.,  p.  530)  increased  the  quantity  of  crude  benzene  (in  1900  the  total  output  in  Europe 
amounted  to  30,000  tons),  yet,  since  the  latter  contains  only  one-sixth  of  its  weight  of  toluene 
and  since  4  kilos  of  toluene  are  required  to  furnish  1  kilo  of  artificial  indigo,  the  use  of  all 
the  toluene  extractable  from  the  benzene  on  the  market  would  give  only  1,000,000  kilos 
of  indigo,  i.e.  one-fifth  or  one-sixth  of  the  whole  consumption.  Increase  of  the  production 
of  crude  benzene  for  the  purpose  of  obtaining  more  toluene  would  lead  to  over-production 
of  unusable  benzene,  and  hence  to  increase  in  the  price  of  toluene  and  hence  in  that  of 
artificial  indigo,  which  would  be  unable  to  compete  with  the  natural  product. 

After  much  further  investigation  and  many  unsuccessful  trials,  the  industrial  prepara- 
tion of  artificial  indigo  has,  however,  become  an  accomplished  fact.  Having  acquired 
Baeyer's  patents  for  a  sum  approaching  £20,000  without  deriving  any  practical  benefit 
from  them,  the  Badische  Anilin-  und  Soda-Fabrik  of  Ludwigshafen  did  not  hesitate  to 
purchase  later  the  patents  of  K.  Heumann,  who  was  the  first  to  discover,  in  1890,  that 
indigo  is  obtained  on  fusion  of  phenylglycocoll  with  caustic  potash,  but  that  a  better  yield 
is  obtained  if  the  phenylglycocoll  is  replaced  by  phenylglycine-o-carboxylic  acid, 
C6H4(CO2H)(NH-CH2-CO2H).  The  economical  preparation  of  this  acid  necessitated 
investigations  and  trials  extending  over  more  than  seven  years,  and  the  synthesis  became 
of  industrial  value  only  when  it  was  found  possible  to  employ  naphthalene  as  the  initial 
substance.  Quite  50,000  tons  of  naphthalene  are  produced  annually  in  the  distillation 
of  tar,  and  up  to  that  time  only  about  15,000  tons  of  this  had  been  utilised,  the  rest  being 
left  in  the  heavy  tar-oils  or  used  for  making  lamp-black  (p.  528).  The  complete  synthesis 
takes  place  in  the  following  stages  : 


Naphthalene 


0     — 


— CO. 

\\r 

-CO/ 

Phthalimide 


NH    — 


C02H 

+ 
NH2 

Anthranilic  acid 


HOI   -!- 


C02H 
,       ,-NH-CH2'C02H 

PhenylglycJne-0-ca.rboxylie  acid 


644 


/NVrv«ym  /  \-rvn~m.  /    \-r,n  .  .m./\ 


C(OH) 


V., 


NH  — ' 


•C(OH) 


CH  — 


•NH— ' 


NH/  \NH 


Indoxylic  acid  Indoxyl  Indigo 

The  oxidation  of  naphthalene  to  phthalic  anhydride  by  means  of  chromic  acid  is  too 
expensive,  but  the  same  end  was  attained  by  the  use  of  fuming  sulphuric  acid  rich  in  sulphur 
trioxide,  after  it  had  become  possible  to  prepare  this  cheaply  by  the  catalytic  method 
(see  vol.  i).  The  action  of  the  acid  was  moderated  with  mercury  bisulphate,  while  the 
sulphur  dioxide  was  recovered  by  the  catalytic  process  (in  1901  the  Badische  Company 
recovered  in  this  way,  for  the  manufacture  of  phthalic  anhydride  alone,  about  40,000  tons 
of  sulphur  dioxide). 

Phthalimide  is  then  easily  obtained  by  the  action  of  ammonia,  while  the  monochloro- 
acetic  acid  can  be  prepared  cheaply  and  in  large  quantity  by  using  the  liquid  chlorine 
(1,000,000  kilos  in  1900)  resulting  from  the  electrolytic  manufacture  of  caustic  soda  or 
potash  and  glacial  acetic  acid  (about  20,000  quintals  obtained  per  annum  from  the  distilla- 
tion of  100,000  cu.  metres  of  wood).  The  reaction  between  anthranilic  acid  and  mono- 
chloroacetic  acid  proceeds  readily,  but  the  formation  of  indoxylic  acid  was  found  to  be  much 
more  difficult,  the  conditions  required  for  the  fusion  of  the  phenylglycinecarboxylic  acid 
being  inconvenient  ;  this  obstacle  was,  however,  finally  overcome.  The  ultimate  oxidation 
of  the  indoxyl  is  effected  by  means  of  a  current  of  air.  The  indigo  separates  in  small 
crystals,  and  in  order  to  obtain  it  in  a  finely  divided  state,  it  is  converted  into  sulphate 
and  this  decomposed  with  water.  After  being  washed,  the  paste  thus  formed  is  identical 
with  natural  indigo  and  is,  indeed,  of  greater  value  owing  to  its  higher  purity  and  to  its 
constancy  of  composition. 

Process  of  the  Farbwerke  vormals  Meister,  .Lucius  und  Bruning  (of  Hdchst).  This 
consists  in  the  action  of  sodamide  (obtained  by  treating  gaseous  ammonia  with  sodium) 
on  phenylglycocoll,  subsequently  heating  in  an  autoclave  at  250°  : 


NH2Na  +  C6H5-NH-CH2-C02Na  =  NH3  +  Na2O  +  C6H4<>CH2  (indoxyl), 
2  mols.  of  the  indoxyl  then  condensing  in  presence  of  oxygen  : 
+  02  =  2H20  + 


This  process  was  originally  patented  by  the  Deutsche  Gold-  und  Silber-Scheide  Anstalt 
(Frankfort),  from  whom  it  was  purchased.  A  yield  as  high  as  65  per  cent,  has  been 
obtained,  but  sodium  at  28d.  per  kilo  is  too  expensive  to  make  the  process  practicable. 

Sandmeyer's  synthesis  (patented  by  Messrs.  Geigy  of  Basle  ;  Eng.  Pat.  15,497  of  1899). 
Aniline  is  treated  with  carbon  disulphide  in  presence  of  alcoholic  potash,  diphenylthio- 
urea  being  obtained:  CS2  +  KOH  +  2C6H5-NH2  =  KHS  +  CS(NH-C6H5)2  +  H20. 
The  action  of  lead  cyanide  on  diphenylthiourea  gives  Hydrocyanocarbodiphenyl- 

C6H5-  Nx 
imide,  /C.CN,    which  with   ammonium    sulphide    yields    the    Thioamide, 

C6H5-NH/ 
C6H5-  N  ^  NH2 

yC  •  C/'          ,  and  this  with  sulphuric  acid  forms  a-Isatinanilide, 
CH-NH/         ^S 


C-NH-C6H5, 

CO/ 

4  \ 

reduction  of  the  latter  by  means  of  ammonium  sulphide  then  giving  indigo.  All  the  materials 
used  in  this  synthesis  are  cheap,  but  the  indigo  produced  was  not  able  to  compete  for  long 
with  that  of  the  Badische  Company  and  of  Messrs.  Meister,  Lucius  und  Bruning,  who 
continually  lowered  the  price  in  order  to  suppress  natural  indigo  and  made  use  of  the  two 
improved  Heumann  processes  starting  from  phenylglycocoll  and  phenylglycinecarboxylic 
acid. 


The  struggle,  lasting  for  more  than  twenty  years,  between  the  producers  of  natural 
indigo  and  the  scientific  men  connected  with  the  various  industrial  undertakings  has  now 
ended  in  uncontested  victory  for  the  latter.  The  figures  already  given  showing  the  areas 
under  indigo  at  different  times  (see  p.  639)  justify  the  conviction  that  in  a  few  years  time 
Indigofera  tinctoria  will  be  of  interest  only  historically,  just  as  is  the  case  with  madder, 
now  supplanted  by  artificial  alizarin. 

With  its  lower  price,  its  more  ready  applicability  in  dyeing,  and  the  considerable  use 
now  made  of  its  halogenated  derivatives,  the  consumption  of  indigo  will  certainly  increase. 
In  1908,  owing  to  the  slight  difficulty  of  reducing  indigo,  even  when  finely  powdered, 
several  firms  placed  on  the  market  the  leuco-product  itself  (indigo  white),  this  being 
obtained  by  reduction  with  iron  and  alkali,  or,  better,  with  hydmsnlp}u.te(Grandmougin),  &c. 
The  following  figures  will  give  a  clearer  idea  of  the  commercial  and  industrial  importance 
of  indigo,  both  natural  and  artificial. 

Statistics.  The  production  in  India  was  50,000  quintals  in  1892  and  75,000  quintals 
(containing  56  to  70  per  cent,  of  indigotin),  of  the  value  of  £3,200,000,  in  1896,  while  in  1909 
it  was  only  12,000  and  in  1910  9000  quintals  (£240,000).  Of  Indian  indigo  60  per  cent. 
is  sold  at  Calcutta,  which  supplies  Europe  and  America,  30  per  cent,  at  Madras  to  Egypt 
and  the  East,  and  10  per  cent,  at  Bombay  and  Karachi.  In  1882  the  Indian  Government 
abolished  the  export  duty  on  indigo.  Until  1865  almost  all  the  indigo  was  sent  to  London, 
which  was  the  centre  of  the  European  trade.  In  1905-1906  exportation  from  India  had 
fallen  to  15,000  quintals  (£400,000),  the  cultivation  of  indigo  being  replaced  by  that  of 
rubber  (28,000  quintals),  turmeric  (25,000  quintals),  hemp,  cotton,  tanning  plants,  &c 
During  recent  years  the  cultivation  of  natural  indigo  has  increased  in  the  districts  more 
suitable  to  it  and  diminished  in  those  less  fitted. 

The  amount  of  indigo  produced  in  British  India  in  1911  was  6  per  cent,  in  advance 
of  that  of  the  preceding  year,  although  the  area  under  cultivation  was  2  per  cent.  less. 
England  imported : 

f  1909      500  tons  of  the  value  of      £139,335 

Natural  indigo     J  1910      167  „  „        .        43,054 

[1911       245  „  „        .        67,430 

I  1909     1670  „  „        .      117,100 

Artificial  indigo   -!  1910     1450  „  „        .      101,249 

[  1911     1215  „  „        .        85,143 

The  United  States  imported  3100  tons  of  natural  and  artificial  indigo  of  the  value 
of  £229,800  in  1910  and  3400  tons  of  the  value  of  £224,600  in  1911. 

In  1854  the  Philippines  exported  194,727  kilos  of  indigo  paste  (£17,445^  and  liquid 
indigo  (tintarron)  (£5470),  while  in  1866  the  amounts  were  251,574  kilos  of  indigo  paste 
(£96,950)  and  959,206  kilos  of  liquid  indigo  (£28,180).  The  industry  was  still  flourishing 
in  1875-1881,  when  the  producers  began  to  adulterate  with  sand  and  other  substances  ; 
prices  were  thus  ruined  and  fell  from  £12  per  quintal  to  £4,  the  cultivation  being  to  some 
extent  abandoned.  With  careful  cultivation,  as  much  as  4  quintals  of  good  indigo  can  be 
obtained  per  hectare.  By  1905  the  exportation  had  diminished  to  a  total  of  250,000  ki'los 
of  pasty  and  liquid  indigo.  The  output  in  Java  amounted  to  547,000  kilos  in  1904  and  to 
500,000  in  1905,  but  in  1908  the  exports  were  only  105,000  and  in  1909  100,000  kilos. 

In  1895  the  consumption  of  indigo  in  different  countries  was  as  follows :  England, 
13,000  quintals  ;  United  States,  11,500  ;  Germany,  10,000  ;  France,  7100  ;  Belgium, 
1500  ;  Austro-Hungary,  5500.  In  1911  the  world's  consumption  of  indigo  (calculated 
for  100  per  cent.)  was  estimated  to  be  about  60,000  quintals,  but  is  possibly  higher  than 
this,  the  amounts  used  in  China  and  some  other  countries  not  being  known  exactly.  In 
1900  the  Badische  Anilin-  und  Soda-Fabrik  produced  10,000  quintals  of  artificial  indigo, 
which  corresponds  with  the  output  from  104,000  hectares. 

Italy  imported  the  following  quantities  of  natural  and  artificial  indigo  : 

1903  1906  1907  1908  1909  1910 

Natural,  quintals       -.         ;         5564       1419         972         944         910          474  (£13,270) 
Artificial,  quintals       ;'      "•  .  2956       3028       3474       4243       .5164  (£72,300) 

The  quantities  of  artificial  indigo  (20  per  cent.)  exported  from  Germany  in  1900  (and 
in  1905),  in  quintals,  were  as  follows  :  to  England  1668  (15,612)  ;  to  France,  1000  (1350)  ; 


646  ORGANIC    CHEMISTRY 

to  Austria-Hungary,  3773  (11,407);  to  Russia,  950  (3160);  to  Italy,  1078  (3200,  worth 
£76,800;  besides  2160  quintals  of  natural  indigo  of  the  value  of  £52,000);  to  Belgium, 
385  (2346)  ;  to  Switzerland,  595  (819)  ;  to  the  United  States,  4926  (25,357)  ;  China, 
1 189  (26,000)  ;  and  Japan,  174  (7000).  In  1907  the  total  production  of  artificial  indigo  was 
about  43,200  quintals  (of  100  per  cent.),  i.e.  four-fifths  of  the  world's  consumption. 
In  the  same  year  Germany  exported  artificial  indigo  to  the  value  of  £2,000,000  (in  1910 
£2,160,000)  and  imported  natural  indigo  worth  £60,000  ;  in  1908  the  exports  were  154,560 
quintals,  and  in  1910  about  161  quintals. 

The  price  of  natural  indigo  reached  its  maximum  of  22s.  per  kilo  in  1870,  at  which 
time  aniline  dyes  came  into  competition  with  it. 

The  price  of  artificial  indigo  (calculated  to  100  per  cent.)  in  1897  was  15s.  to  16*.  per 
kilo,  a  corresponding  amount  of  the  natural  product  costing  16*.  to  18s.  In  1900  natural 
indigo  cost  12*.,  while  in  1905  artificial  indigo  was  sold  at  one-half  the  price  of  the  natural 
dye,  i.e.  at  about  1*.  Id.  per  kilo  of  20  per  cent,  strength. 

The  first  artificial  indigo  plant  of  the  Badische  Anilin-  und  Soda-Fabrik  in  1897  cost 
£480,000,  and  in  1900  two  competitors,  namely,  Messrs.  Meister,  Lucius  und  Briining 
and  Messrs.  Geigy,  made  their  appearance,  the  considerable  fall  in  price  thus  produced 
resulting  in  Messrs.  Geigy's  abandonment  of  the  manufacture  and  of  the  fusion  of  the 
indigo  interests  of  the  two  remaining  firms  with  a  capital  of  £1,200,000.  In  1910  the 
manufacture  of  artificial  indigo  was  started  by  the  Rahtjen  Company  of  Hamburg — 
which  is  a  company  with  a  capital  of  £280,000  and  makes  use  of  Rahtjen's  improved 
Sandmeyer  process — and  by  the  firm  of  Heyden  (Radebeuf),  which  employs  the  phenyl- 
glycine  method.  The  Society  of  Chemical  Industry  in  Basle  also  began  making  artificial 
indigo  in  1911-1912. 

R.  COLOURING-MATTERS 

Only  a  certain  proportion  of  the  innumerable  coloured  substances  are  capable 
of  being  fixed  on  vegetable  or  animal  fibres,  imparting  to  them  a  more  or  less 
stable  coloration,  and  only  those  able  to  fulfil  this  function,  directly  or  indirectly, 
belong  to  the  true  Colouring-Matters. 

Coloured  substances  are  those  which  absorb  constituents  of  white  light  of 
certain  definite  wave-lengths,  emitting  the  rest. 

Generally  speaking,  only  the  luminous  waves  visible  to  the  eye  have  yet 
been  closely  studied,  and  it  is  probable  that  new  laws,  possibly  more  important 
than  those  already  known,  will  be  discovered  when  the  infra-red  and  ultra- 
violet rays  absorbed  or  reflected  by  coloured  substances  are  considered. 

Hartley  has  indeed  shown  that  the  apparently  colourless  substance,  benzene, 
is,  strictly  speaking,  coloured,  as  it  absorbs  certain  ultra-violet  rays  invisible 
to  the  eye,  and  that  in  the  benzene  series  the  luminous  vibrations  are  gradually 
rendered  slower  and  so  made  visible  as  the  molecular  weight  is  increased  by 
substituent  groups. 

Dichroic  Substances  allow  certain  rays  to  traverse  them  and  reflect  certain 
others,  so  that  they  appear  to  be  of  one  colour  by  transmitted,  and  of  another 
by  reflected,  light ;  such  are,  for  example,  fluorescent  substances.  Certain 
alkaline  fluorides,  such  as  those  of  the  alkali  metals,  allow  infra-red  and  ultra- 
violet radiations  to  pass  through  them,  while  various  nitrates,  nitric  acid, 
the  hydrocarbons,  the  aldehydes,  &c.,  although  they  do  not  retain  any  of  the 
constituents  of  white  Mght  and  hence  appear  colourless,  yet  do  absorb  waves 
of  many  wave-lengths. 

Light  itself  is  to  the  human  organism  only  a  sensation  due  to  absorption  of 
a  portion  of  the  radiations  by  the  crystalline  lens  of  the  eye. 

Between  coloured  and  non-coloured  substances  there  is  often  complete  or 
nearly  complete  identity  in  chemical  composition,  so  that  the  colour  depends, 
not  on  the  composition,  but  only  on  the  constitution  or  atomic  structure  of  the 
molecule. 

It  is  now  universally  admitted  that  the  colour  of  substances  is  closely 


CHROMOGENS 


647' 


dependent  on  the  presence  in  the  molecule  of  certain  well-defined  atomic 
groupings  or  nuclei. 

The  various  organic  substances  of  the  benzene  series  which  form  coloured 
or  colouring  matters  always  contain  these  groups  (chromophores,  see  below), 
some  of  which  are  univalent  and  quite  simple,  e.g.  —  N02,  X  —  N=N  —  , 
X  —  CO  —  .  But  of  more  importance  are  the  divalent  groups  formed  of  a  benzene 


nucleus  of  the  constitution   >>C<< 


pTT 


where  X2  may  be  0,  NH, 

NR,  CR2,  while  the  other  two  valencies  in  the  para-position  may  be  satisfied 
by  0,  NH,  N,  R2,  Cl. 

As  early  as  1867  Graebe  and  Liebermann  arrived  at  the  conclusion  that 
the  colouring-matters  capable  of  fixing  hydrogen  with  decoloration  and  forma- 
tion of  the  so-called  leuco-bases  (see  p.  607),  are  transformed  into  coloured 
substances  on  oxidation.1 

In  1876  N.  0.  Witt  defined  the  nature  of  these  simple  groups,  which  are 
always  contained  in  the  more  complex  benzene  groups  characteristic  of  the 
colouring-matters,  terming  the  former  chromophores  and  the  latter  chromogens? 

1  Some  of  these  leuco-products  regenerate  the  original  colouring-matter  simply  by  oxidation,  while  others  do 
not.     For  instance,  reduction  of  nitro-groups  gives,  as  final  products,  amino-derivatives,  which  yield  nitro-groups 
again  on  oxidation.     The  complete  reduction  of  azo-compounds  yields  amino-groups,  but  there  may  also  be 
intermediate,  less  highly  reduced  products  (hydrazo-compounds),  which  are  themselves  new  leuco-derivatives. 

2  Examples  of  chromogens  are  : 


>=N-C,H4-NH2; 
Indamine 


/  -N-C8H4-NH2; 


=C=(C,H4-NH,)S 


Indophenol 


Rosaniline 


Rosolic  acid 


CO 


CO 

Anthraquinone 


NH 

Thiodiphenylamine 


NH, 


OH 


N 

Thionine 

In  these  chromogens  is  seen  the  analogy  between  the  chromophores  in  the  different  molecules,  characterised  by 

divalent  or  polyvalent  atoms  or  atomic  groups  (=NH,=N'  —  ,  =C=O,  S,  —  O  —  ,  ^>CO)  united  to  the  ring  in  a 

closed  chain,  the  whole  forming  the  true  chromophore,  which,  joined  to  the  rest  of  the  molecule,  gives  the  chromogen. 

The  passage  from  simple  to  more  complex  chromophores  is  often  accompanied  by  change  from  a  yellow  colour 

to  a  more  intense  yellow  or  to  red  or  blue. 


Resorufln 


ORGANIC    CHEMISTRY 


The  latter  are  colourless  or  slightly  coloured  but  approximate  to  the  colouring- 
matters  in  chemical  composition.  Jt  is,  indeed,  sufficient  to  introduce  into 
the  chromogen,  in  place  of  hydrogen,  a  salt-forming  basic  or  acid  radical  (OH, 
SO3H,  C02H,  NH2),  to  produce  the  colouring-matter.  Thus,  nitrobenzene, 
C6H5'N02,  is  a  chromogen  which  becomes  a  true  colouring-matter  in  nitro- 
phenol,  C6H4(OH)'N02,  and  in  nitraniline  (phenol  itself,  C6H5'OH,  is  colourless). 
The  intensity  of  the  coloration  increases  with  the  number  of  these  acid  or  basic 
groups  ;  thus, 

Aminoazobenzene,  C^H^Na-NH^,  is  pale  yellow, 
Diaminoazobenzene,  C12H8N2(NH2)2,  is  orange,  and 
Triaminoazobenzene,  C12H7N2(NH2)3,  is  brown. 

Such  regularities  often  occur  with  artificial  colouring-matters,  so  that  the 
colour  of  a  new  compound  of  a  certain  constitution  can  be  foretold  before 
the  compound  is  prepared.1 

In  the  light  of  the  above  definition  it  would  be  difficult  to  understand 
how  colouring-matters  could  be  formed  of  hydrocarbons  alone,  since  these 
contain  none  of  the  characteristic  chromophores  just  mentioned.  The  few 
hydrocarbon  colouring-matters  were  for  some  time  regarded  as  exceptions, 
but  it  was  found  later  that  they  contain  a  characteristic  complex  chromophore, 
different  from  those  previously  known  and  with  molecular  weight  higher 
than  a  certain  limit.  The  following  two  chromophores,  for  example,  are  well 
defined  : 


| 

\~> 


and 


— X  X— / 


Further,  what  are  usually  the  more  energetic  chromophores  cease  to  be 
so  when  they  occur  in  molecules  which  are  small  or  poor  in  carbon.  To  this 
is  due  the  very  small  number  of  colouring-matters  in  the  aliphatic  series. 

Thirteen  chromophores  of  well-defined  constitution  are  now  known,  while 
concerning  others  there  is  still  doubt  owing  to  the  pseudoisomerism 
(tautomerism)  they  exhibit.2 

1  With  fuchsines  (rosanilines  and  p-rosanilines)  the  colour  becomes  more  intense  and  more  violet  with  increase 
in  the  alkyl  groups  replacing  the  aminic  hydrogen.  The  faintly  acid,  ph<*iolic  colouring-matters  which  are  fixed 
by  mordants  give  highly  resistant  colours  if  they  contain  at  least  two  OH  groups,  or  OH  and  COOH,  in  the  ortho- 
position,  and  better  still  if  these  are  also  in  ortho-positions  with  respect  to  the  chromophores.  In  the  colouring- 
matters  of  the  nitrophenol  group,  the  colour  passes  from  greenish  yellow  to  orange-yellow  as  the  distance  between 
the  OH  and  NOj  groups  increases.  Fast  colours  on  mordants  are  given  especially  by  those  colouring-matters 
containing  hydroxyl-groups  in  the  ortho-position  with  respect  to  one  another  and  to  the  chromophore  (alizarin,  &c.). 

Of  the  triphenylmethane  colouring-matters,  those  which  have  a  sulphonic  group  (SO8H)  in  the  ortho- 
position  with  respect  to  the  central  carbon  atom  are  stable  to  alkali  and  to  soap  (Suais  and  Sandmeyer). 

8  According  to  Hantzsch  (1906)  all  the  true  nitro-hydrocarbons  of  the  aromatic  or  aliphatic  series  and  also  all 
polynitro-compounds  are  colourless  when  quite  pure,  so  that  the  NO2  group  by  itself  is  never  a  chromophore.  Only 
certain  nitrophenols  are  coloured  when  their  phenolic  hydrogen  is  free  and  hence  mobile  (forming  tautomeric  com- 
pounds) and  for  the  same  reason  all  salts  of  nitrophenols  are  coloured.  By  the  discovery  of  the  quinonic  (aci-) 
ethers  of  nitrophenols  besides  the  true  ethers,  it  was  shown  that  many  colourless  or  almost  colourless  hydrogenated 
compounds  capable  of  forming  highly  hydrogenated  salts,  are  pseudo-acids,  so  that  the  coloured  salts  are  derived 
from  a  hydrogenated  compound  differing  from  the  original  ;  if  it  were  possible  to  obtain  these  free,  they  also  would 
be  coloured. 

Nitrophenols  are  certainly  true  tautomeric  hydrogenated  compounds  which  give  two  series  of  structurally 
isomeric  ethers,  such  as  are  given  also  by  nitrous,  sulphurous,  hydrocyanic,  and  cyanic  acids.  The  true  nitro- 
phenolic  ethers  are  colourless,  while  the  aci-ethers  (tautomeric)  are  coloured  an  intense  red  ;  the  former  correspond 


with  the  general  formula,  CtH4: 


O 


*"+' 


(derived  from  the  colourless  true  nitrophenol,  C,H, 


0 


-OH 


),  and 


the  hitter  with  C.H^  [derivatives  of  aci-nitrophenol  (quinonic),  C,H4^  ].      It  is 

^NO'OC;,Ht,,  +  t  ^\NO'OH 

hence  possible  to  tell,  from  the  mere  colour,  to  which  of  the  two  groups  a  given  nitro-compound  belongs. 
When  true  nitrophenols  (even  in  the  solid  state)  are  slightly  coloured,  it  is  assumed  that  a  minimal  quantity  of  Ihe 
aci-nitrophenol  is  dissolved  in  a  large  quantity  of  true  nitrophenol  (solid  solution).  Also,  the  fact  that  the  colour 
of  the  substance  is  sometimes  not  intensified  by  increase  in  the  number  of  nitro-groups  is  explainable,  not  on  the 
old  view  of  tht  theory  of  chromophores,  but  only  by  the  new  theory  of  transposition  (tautomerism)  : 

,on      — ^  ,o 

C.FT./  C,H4^ 

\NO'OH 


SALT-FORMING   GROUPS  640 

In  practical  dyeing  it  is  of  interest  to  know,  not  only  that  a  substance  has 
colouring  properties  but  to  what  chemical  conditions  or  groups  these  properties 
are  due.  Especially  is  this  the  case  with  animal  and  vegetable  textile  fibres 
(see  Theory  of  Dyeing,  p.  708). 

Chromophores  are  generally  of  basic  (electropositive)  or  acid  character 
(electro-negative,  e.g.  the  quinonoid  group,  &c.)  and  when  they  form  coloured 
substances  do  not  retain  their  colouring  properties ;  the  latter  are,  however, 
manifested  if  the  basic  or  acid  character  is  reinforced  or  even  inverted  by 
means  of  salt-forming  groups. 

The  acid  groups  (S03H,  C02H,  &c.)  have,  however,  a  slight  influence  on 
the  colour.  Thus,  azobenzene,  C6H5'N  :  N'C6H6,  although  a  coloured 
chromogen  (containing  the  chromophore  -N  :  N-)  does  not  colour  textile 
fibres  since  it  is  neutral,  while  its  sulphonic  derivative  is  a  feeble  colouring- 
matter. 

The  basic  groups  (especially  NH2  and,  in  some  cases,  OH,  &c.),  on  the 
other  hand,  exert  considerable  influence  on  the  colour,  and  Witt  calls  them 
auxochrome  groups  to  distinguish  them  from  the  acid  groups,  which  he  terms 
salt-forming  groups.1 

The  tendency  to  tautomeric  transposition  may,  indeed,  be  increased  or  diminished  by  the  entry  of  new  groups. 
Thus,  in  solutions  of  nitrophenols  and  their  salts,  the  coloration  is  not — as  it  would  be  according  to  the  modern 
theory  of  indicators  (see  vol.  i,  p.  97) — due  to  ionisation,  but  rather  to  the  formation  of  coloured  tautomeric 
compounds  (aci-nitrophenolic  ethers)  in  agreement  with  the  old  chemical  theory  of  indicators. 

It  is  thus  proved  that  the  formation  of  coloured  salts  and  coloured  ions  derived  from  colourless  hydrogenated 
compounds  is  of  a  purely  chemical  nature.  It  is  caused  first  of  all  by  intramolecular  transposition,  from  which, 
by  the  action  of  a  positive  metal  (salt),  there  results  a  negative  quinonic  atomic  grouping  (chromophore),  the 
appearance  of  coloured  ions  being  a  secondary  reaction.  Hence  the  actions  of  chromophore  and  of  auxochrome 
cannot  be  held  to  be  distinct  but  are  exerted  together,  both  of  them  (nitro-  and  phenol-group)  causing  the  appearance 
of  colour  at  the  expense  of  their  mutual  transformation,  which  generates  a  quinonic  grouping  containing  neither 
nitro-  notfphenolic  group. 

These  views  may  be  extended  to  other  groups  of  organic  substances  since,  in  general,  colourless  acids  unchange- 
able in  constitution  (i.e.  not  giving  tautomeric  forms)  give  only  colourless  ions  and  yield  colourless  salts  with  colour- 
less metallic  oxides,  and  colourless  ethers  and  esters  with  colourless  organic  radicals  (alkyl  and  acyl).  If  -oloured 
ions  and  salts  are  derived  from  a  colourless  alkyl  compound,  it  may  be  stated  with  certainty  that  intramolecular 
change  occurs. 

According  to  E.  Fischer  and  0.  Fischer  (1900)  many  colouring-matters  derive  their  properties  from  the  presence 

in  the  molecule  of  quinonoid  groups,  although  A.  v.  Baeyer  (1902-1905)  and  Hantzsch  (1905)  showed  that  the  true 

quinone  group  does  not  always  cause  coloration  (i.e.  is  not  the  chromophore),  and  Kostanecki  and  Haller  pointed 

out  that,  in  addition  to  the  two  carbonyl  groups  of  the  quinone,  two  ethylene  double  linkings  must  be  present, 

CO  CO 


HOf        ;CH  H,C'       > 


;  in  fact,  diketohexamethylene, 


CH, 


,  which  has  not  these  double  bonds,  is  completely 


CH, 


HtH        "CH  H,C 

CO  CO 

colourless.  As  a  metaquinone  with  two  ethylene  double  linkings  cannot  exist  such  meta-compounds  are  incapable 
of  producing  colouring-matters. 

CH      CH  cm 

'  n   -a      t  ^-HLj 

/  \  /    '    '  i  NH 

'  Rosaniline,  HN  =  C\  >C  =-  C(  l       *  (see  corresponding  base,  p.  608),  which  is  coloured 

\        /         XC.H^NH, 
CH    CH 

CH=CH 
contains  as  chromophore  the  group  HN  =  C/  \r>^-'»  and  as  auxochfomes  two  ammo-groups.    When  the 

\ /<- 

CH=CH 

salt  with  a  single  molecule  of  HC1  is  obtained  and  the  substance  is  dyed  red,  proof  is  given  that  the  salt  is  formed 
with  the  imino-group  of  the  chromophore,  since  a  red  coloration  is  formed  on  the  fibres.  On  the  other  hand,  salts 
of  rosaniline  with  two  or  three  molecules  of  HC1,  which  form  salts  also  with  the  auxochrome  amino-groups,  are 
yellow  but  do  not  dye  textile  fibres  yellow.  It  can  hence  be  affirmed  that  the  auxochromes  do  not  unite  with  the 
fibres  and  hence  have  no  action  as  salt-forming  groups  but  only  contribute  to  increase  the  basic  character  of  the 
colouring-matter  or  even  to  increase  the  intensity  of  the  colour ;  this  is  clearly  shown  with  safranine  (see  later  and 
also  above,  Aminoazobenzene).  In  general,  the  union  of  an  acid  chromophore  with  a  basic  auxochrome  gives 
colouring-matters  of  slight  intensity ;  for  instance,  the  nitroanilines  are  feeble  and  the  nitrophenols  more  intense 
colouring-matters. 

The  replacement  of  the  hydrogen  of  the  auxochrome  OH  by  a  metal  increases  the  power  of  the  auxochrome, 
while  an  alkyl  or  aromatic  radical  lowers  it  and  an  acid  radical  often  annuls  it.  Substitution  of  the  hydrogen  of 
the  auxochrome  NHj  by  alkyl  radicals  raises  the  colouring  power,  while  two  aromatic  radicals  sometimes  lower  it 
considerably,  exceptions  to  this  being  shown  by  sulphonal  and  picryl,  C,Hj(NO,)j,  which  cause  the  NH,  group  to 
assume  an  acid  character.  The  hydrazinic  and  hydroxylaminic  groups  also  behave  as  auxochromes ;  thus  phenyl- 
hydrazine  is  slightly  yellow  while  aniline  is  colourless,  and  nitrophenylhydrazine  is  more  highly  coloured  than 
nitroaniline.  Anthraquiuone  (faintly  acid  chromogen)  gives  an  intensely  coloured  derivative  with  hydrazine 


ORGANIC    CHEMISTRY 

The  acid  or  basic  character  of  a  colouring-matter  decides  also  its  behaviour 
towards  different  textile  fibres— vegetable  and  animal — and  in  general  acid 
colour  ing -matters  contain  the  group  S03H  or  COOH,  the  feebly  acid  ones  the 
group  OH,  and  the  basic  ones  the  groups  NH2,  NHR,  NR2,  either  as  chromophore 
or  as  auxochrome. 

If  the  auxochrome  of  a  colouring-matter  is  weak  and  the  chromophore 
strong,  or  vice  versa,  the  colouring-matter  is  generally  feeble. 

For  dyeing  purposes  the  colouring-matters  are  placed  on  the  market  in  a 
state  soluble  in  water,  the  auxochrome  groups  being  converted  where  possible 
into  salts  (e.g.  S03Na,  &c.).  When  wool  (which  is  both  basic  and  acid  in  cha- 
racter) is  dyed  with  acid  colours,  since  the  basic  properties  of  the  wool  are  usually 
not  sufficiently  strong  to  displace  the  metal  (Na)  of  the  acid  colour,  an  energetic 
acid  (acetic  or  sulphuric)  is  added  to  the  hot  aqueous  dyeing  bath,  this  liberating 
the  acid  residue  of  the  colouring-matter,  which  can  then  combine  with  the  basic 
group  of  the  wool  to  form  a  coloured  stable  insoluble  salt  in  the  fibre  itself. 

Thus  wool  is  dyed  directly  both  by  acid  and  by  basic  colours  (with  the  latter 
it  is  not  necessary  to  render  the  bath  acid).  Cotton,  on  the  other  hand,  is  not 
usually  dyed  by  acid  dyes  but  only  by  basic  ones,  and  then  only  when  the 
fibres  are  previously  mordanted  with  tannin  materials  and  metallic  salts. 

During  the  past  twenty  years,  however,  numerous  neutral  or  substantive 
dyestuffs  have  been  discovered,  capable  of  dyeing  cotton  directly  in  a  neutral 
or  faintly  alkaline,  but  not  acid,  bath,  previous  mordanting  being  unnecessary. 
Many  of  these  colouring-matters  have  a  common  benzidine  group  (see  p.  605), 
others  contain  a  basic  group  (primulin)  and  others  again  a  phenolic  group 
(curcumin).  Colouring-matters  sometimes  acquire  this  property  by  mere 
accumulation  of  chromophores  in  a  single  molecule  (Rupe,  1901 ).  The  nature  of 
the  metal  present  in  these  colouring-matters  alters  to  some  extent  the  properties 
and  the  affinity  towards  cotton,  but  this  is  always  related  to  the  capillary 
constant  of  the  aqueous  solution.  The  precipitation  of  the  unaltered  colouring- 
matter  on  the  fibres  is  facilitated  by  increasing  the  osmotic  pressure  of  the  bath 
by  the  addition  of  considerable  quantities  of  salts  (NaCl  or  Na2S04). 

As  a  rule  phenolic  compounds  form  weak  colouring-matters,  but  they  have 
the  property  of  giving  intensely  coloured  lakes  with  metals  (phenoxides),  the 
metallic  atom  united  to  the  phenolic  oxygen  functioning  as  an  energetic 
auxochrome.  These  colouring-matters  having  no  affinity  for  textile  fibres, 
the  latter  are  previously  charged  with  metallic  oxides  (mordants).  Lakes  of 
different  colours  are  formed  with  different  metals  (Hummel  hence  called  such 
colouring-matters  polygenetic),  but  for  practical  purposes  it  is  indispensable 
that  they  should  be  resistant  to  atmospheric  agents  and  to  ordinary  physico- 
chemical  treatment.1  The  best  among  these  substances  are  those  containing 
in  the  ortho-position  either  two  phenolic  groups  (OH)  or  one  OH  and  one 
COOH,  and  of  such  those  are  best  in  which  these  groups  are  in  the  ortho- 
position  with  respect  to  the  chromophore  (Liebermann  and  Kostanecki, 

groups.  The  hydroxylamine  derivatives  are  few  in  number  and  have  been  but  little  studied.  H.  Kaufmann 
(1911)  has  shown  that  two  auxochromes  reinforce  one  another  when  they  are  in  the  para-position  and  to  a  less 
extent  or  not  at  all  when  they  are  in  the  ortho-  or  meta-position.  This  rule  is  confirmed,  not  only  by  the  greater 
intensity  of  the  colour,  but  also  by  the  increased  luminescence  or  fluorescence  assumed  by  these  substances  when 
they  are  exposed  to  ultra-violet  rays  (see  vol.  i,  p.  121) ;  in  solution,  only  compounds  of  the  para-  series  give  direct 
fluorescence.  By  the  law  of  distribution  it  is  proved  that  the  maximum  and  sometimes  the  only  effect  of  auxo- 
chromes in  the  para-position  is  exerted  when  the  chromophore  and  auxochrome  are  in  the  same  benzene  nucleus. 
1  In  addition  to  what  has  been  already  stated  with  reference  to  the  application  of  lakes,  it  may  be  said 
that  they  are  derived  from  acid  or  basic  colouiing-matters,  coloured  pigments  or  colouring-matters  of  the  anthra- 
quinone  group.  The  soluble  acid  colouring-matters  are  precipitated  by  salts  of  calcium,  barium,  strontium,  alu- 
minium (chlorides),  magnesium  (sulphate),  &c.  Solutions  of  basic  dyes  are  precipitated  by  tannin,  Turkey  red 
oil,  resin,  or,  more  commonly,  sodium  phosphate  or  sodium  arsenate.  Anthraquinone  dyes  (alizarin,  coerulein, 
&c.)  form  lakes  with  greater  difficulty,  and  it  is  necessary  to  observe  rigorously  the  proper  temperature  conditions. 
In  pieparing  lakes,  great  importance  attaches  also  to  the  substance  on  which  the  precipitated  lake  is  deposited 
or  with  which  it  is  mixed  (aluminium  hydroxide,  barytes,  zinc  or  lead  white,  ferric  oxide,  fresh  aluminium  silicate, 
&c.),  and  of  these,  the  ones  more  easily  decomposable  by  dilute  acids  retain  the  colour  best.  Lake-formation 
is  hence  not  a  simple  absorption  phenomenon  but  also  a  chemical  phenomenon. 


DYES    IN    RELATION    TO    FIBRES 

1887-1893)  and  in  which  the  auxochrome  is  formed  from  iron,  aluminium, 
or  chromium.  Not  all  colouring-matters  which  give  insoluble  lakes  can  be 
fixed  on  fibres  mordanted  with  metallic  oxides,  and  this  perhaps  depends 
on  the  fact  that  only  certain  coloured  lakes  are  capable  of  combining  with  the 
fibre,  the  constitution  of  the  colouring-matter  (see  Alizarin)  being  here  also 
of  considerable  importance. 

When  basic  or  neutral  colouring-matters  are  sulphonated  with  concentrated 
H2S04,  acid  colouring -matters  (Simpson  and  Nicholson,  1862)  are  often  obtained. 
In  the  form  of  soluble  salts  of  the  alkali  metals,  these  can  be  fixed  directly, 
in  an  acid  bath,  on  animal  fibres  with  the  same  colour  as  the  colouring-matter, 
the  animal  fibre  forming  a  kind  of  new  salt  ;  indeed  the  fibre  assumes  the 
colour  of  the  original  salt  of  the  colouring-matter  and  never  that  of  its  free 
coloured  acid  liberated  in  the  bath  by  means  of  acetic  or  sulphuric  acid  (see 
above,  Process  of  Dyeing).  These  acid  colours  are  fixed  also  by  cotton,  provided 
the  latter  is  first  rendered  basic  either  by  nitrating  and  then  reducing,  or 
by  oxidising  (oxycellulose),  or  by  hydrating  (with  NaOH  :  mercerisation), 
or  by  treating  with  NH3  under  pressure  in  presence  of  ZnCl2  (Vignon). 

Basic  colouring -matters  which  owe  their  basicity  to  the  chromophore  and  more 
especially  to  the  auxochrome  NH2,  form  salts  with  acids  and  are  used  in  practice 
in  the  form  of  hydrochlorides,  sulphates,  &c.,  from .  hot  acidified  aqueous 
solutions  of  which  wool  and  silk  fix  the  coloured  base.  These  basic  dyes  also 
form  insoluble  salts  with  tannin,  &c.,  so  that  they  are  capable  of  dyeing  cotton 
- — which  has  no  affinity  for  basic  dyes — if  this  is  previously  mordanted  by  • 
prolonged  immersion  in  cold  solutions  of  tannin  extracts  (sumac,  &c.),  followed 
by  fixation  of  the  tannin  in  another  bath  containing  an  antimony,  aluminium 
or  iron  salt,  or  gelatine.  In  the  subsequent  dyeing-bath,  the  dye  is  fixed 
rapidly,  even  in  the  cold  (the  fixation  is  more  regular,  i.e.  slower,  in  presence 
of  a  little  alum).  The  full  (intense),  bright  colours  thus  obtained  on  cotton 
resist  the  different  reagents  well  but  are  destroyed  during  washing  by  the 
rubbing.  In  1901  C.  Favre  suggested  the  use  of  resorcinol  and  formaldehyde 
as  mordants  in  place  of  tannin.1  Many  colouring-matters  exert  a  poisonous 

1  Behaviour  of  Colouring-Matters  towards  different  Fibres  and  Mordants,  according  to  Noelting.  If  a 
skein  of  wool,  silk,  or  cotton  is  immersed  for  some  hours  in  a  solution  of  a  basic  ferric  salt,  the  fibres  assume  a 
brown  colour,  having  fixed  a  certain  amount  of  ferric  oxide  or  basic  salt.  The  same  holds  generally  for  all  salts  of 
oxides  corresponding  with  the  formula  R2O,.  The  salts  of  protoxides  (RO),  e.g.  those  of  copper,  iron,  manganese, 
nickel,  cobalt,  &c.,  especially  the  tartrates  or  in  presence  of  tartar,  are  fixed  by  wool  or  silk,  but  not  at  all  or  but 
slightly  by  vegetable  fibres. 

Not  only  metallic  salts,  but  also  certain  organic  substances  (tannin  materials)  and  salts  of  hydroxyoleic  and 
hydroxystearic  (sulpho-oleates)  acids,  can  be  fixed  by  fibres. 

A  large  number  of  colouring-matters  are  fixed  directly  on  animal  fibres  in  a  neutral  or  acid  bath,  more  rarely 
in  an  alkaline  bath.  To  this  group  belong  the  nitro-derivatives  of  the  phenols  and  amines  :  the  azo,  basic,  and 
acid  dyes  ;  basic,  acid,  or  sulphonated  derivatives  of  triphenylmethane  ;  certain  phthaleins  (fluorescein  and  eosin)  ; 
the  aminophenazines,  safranines,  thioindamines,  phenoxazine  derivatives  (gallocyanine  and  Meldola's  blue), 
phenylacridine  complexes  (phosphine),  quinoline  complexes  (cyanine,  quinoline  red,  quinophthalone),  hydrazides, 
osazones  (tartrazine),  ketonimides  (auramine)  and,  among  the  natural  colours,  indigo-carmine,  berberine,  safHower, 
saffron,  archil,  and  catechu.  Almost  all  of  these  dyes  are  fixed  in  minimal  quantity  or  not  at  all  on  vegetable 
fibres.  Those  which  are  fixed  by  the  latter  are  less  numerous  and  include  :  a  first  group  of  substances  which  aie 
fixed  only  with  difficulty  (better  with  tannin),  e.g.  certain  aminoazo-compounds,  phenylene  brown,  chrysoidine, 
methylene  blue,  Victoria  blue,  safranine  ;  a  second  group  fixed  stably  and  directly  and  consisting  of  numerous 
azo-derivatives  of  beoeidine,  tolidine,  diaminostilbene,  p-phenylenediamine,  naphthylenediamine,  diamino- 
azobenzene,  diaminoazoxybenzene  and  its  homologues,  diaminodiphenylamine,  canarine  (oxidation  product  of 
thiocyanates),  and  the  sulphur  dyes  of  Croissant  and  Bretonnierc  ;  a  third  group  which  do  not  dye  wool,  cotton,  or 
silk  directly  but  give  bright  fast  colours  if  these  fibres  (especially  with  wool)  are  previously  mordanted  with  salts 
of  iron,  aluminium,  or  chromium  :  such  are  certain  phthaleins  (gallein),  derivatives  of  anthraquinone  (alizarin, 
purpurin,  alizarin  orange,  anthragallol),  anthraquinoline  (alizarin  blue),  phenoxyanthranol  (ccerulein),  and 
almost  all  the  natural  colouring-matters  (logwood,  cochineal,  quercitron,  cudbear,  sandalwood,  &c.).  Noelting 
gave  the  name  substantive  dyes  to  those  which  dye  animal  and  vegetable  fibres  directly  and  that  of  adjective  dyes 
to  those  which  dye  the  fibres  only  after  mordanting. 

Certain  dyestuffs  are  fixed  directly  by  wool  and  silk  and  only  indirectly  by  cotton,  i.e.  when  the  latter  has  been 
mordanted.  Such  are  gallocyanine  and  various  carboxylic  acids  of  azo-compounds.  In  dyeing  with  aniline  black, 
the  fibre  fixes  both  the  aniline  salt  and  also  the  oxidising  agent,  the  latter  oxidising  the  aniline  on  the  fibre  with 
formation  of  an  insoluble  aniline  black.  Dyes  which  are  not  fixed  directly  by  cotton,  dye  it  only  after  mordanting 
with  tannin  or  sulpholeic  acids  if  they  are  basic  in  character,  or  after  mordanting  with  metallic  oxides,  with  or  with- 
out sulpholeates,  if  they  are  acid. 

Further,  various  substantive  colouring-matters  have  the  property  of  fixing  others  on  them  ;  for  instance,  chrys. 
amine  and  canarine,  which  are  yellow,  fix  basic  colouring-matters,  such  as  fuchsine  forming  an  orange,  malachit 


652  ORGANIC    CHEMISTRY 

action  oil  micro-organisms,  as  they  unite  with  the  protoplasm,  and  even,  in 
dilute  solution,  cause  death  (Th.  Bokorny,  1906). 

In  recent  years  attempts  have  been  made,  but  without  practical  success,  to 
utilise  the  colouring-matters  produced  by  certain  chromogenic  bacteria,  e.g. 
B.  prodigiosus) . 

MANUFACTURE  OF  COLOURING-MATTERS 

Since  1856-1860,  when  Perkin  in  England  made  mauveine  and  Renard 
and  Frank  in  France  made  fuchsine  on  an  industrial  scale,  scientific  progress 
in  colouring-matters  has  advanced  pari  passu  with  the  industrial  development. 

In  the  history  of  the  artificial  colouring- matters,  side  by  side  with  the  names 
of  the  scientific  men,  such  as  Perkin,  Williams,  A.  W.  Hofmann,  Graebe, 
Liebermann,  Baeyer,  Witt,  Nietzki,  Noelting,  Caro,  &c.,  who  laid  the  first 
stones  in  this  marvellous  chemical  edifice,  are  those,  not  less  worthy,  of  the 
brilliant  and  daring  industrial  workers  who,  by  uninterrupted  energy  and  the 
application  of  ingenious  processes,  carried  these  theoretical  discoveries  into 
the  larger  field  of  industry  and  commerce.1 

green  forming  a  yellowish  green,  and  methylene  blue  forming  a  blue  colour.  All  the  benzidine  colours  have  the 
same  property,  to  .which  Noelting  gives  the  name  secondary  dyeing,  a  term  applicable  also  to  all  dyeing  with  mordants . 
Direct  dyeing  would  then  be  primary  dyeing. 

In  some  cases  a  third  colouring-matter  can  be  superposed  ;  for  instance,  the  violet  lake  of  alizarin  and  iron 
combines  with  methyl  violet  giving  a  brilliant  triple  lake.  The  red  lake  of  alizarin,  alumina,  and  lime,  which  is 
not  very  bright  and  rather  opaque,  is  rendered  brilliant  and  more  fast  by  the  fixation  of  a  sulpholeate,  which 
forms  a  quadruple  lake  ;  finally,  this  can  still  fix  tin  from  a  soapy  solution  of  tin  salt,  a  new  lake  with  five  components 
being  formed. 

If  a  tissue  removed  from  a  solution  of  a  basic  iron  salt,  instead  of  being  washed  immediately  (in  which  case  it 
becomes  yellowish),  is  treated  directly  with  alkali  or  soap  (or  with  a  solution  of  a  salt  the  acid  residue  of  which 
forms  an  insoluble  compound  with  oxide  of  iron),  it  becomes  much  more  intensely  coloured  and  the  quantity  of 
iron  fixed  by  the  fibres  is  considerably  increased.  Oxide  of  iron  can  be  accumulated  on  the  fibre,  not  only,  as  just 
mentioned,  from  an  alkaline  bath,  but  also  by  impregnating  the  fibre  itself  with  ferrous  salts  of  volatile  acids,  e.g. 
the  acetate,  and  then  exposing  it  in  the  moist  state  to  the  air.  The  ferrous  salt  is  thus  converted  into  basic  ferric 
salt,  this  in  warm,  moist  air  losing  part  of  its  acid  and  undergoing  change  into  an  insoluble,  highly  basic  salt, 
which  is  not  removed  from  the  fibre  even  by  repeated  washing. 

In  order  to  help  the  action  of  the  air  and  render  a  larger  quantity  of  basic  salt  insoluble,  the  fibre  may  be  passed 
into  a  bath  of  cow-dung  or  lime  and  potassium  silicate,  phosphate,  or  arsenate.  Aluminium  salts  are  similarly 
rendered  insoluble  by  formation  of  a  basic  salt.  The  basic  chromium  salt  is  fixed  by  a  subsequent  bath  of  sodium 
carbonate  or,  better  still,  by  impregnating  the  tissue  with  a  solution  of  chromium  sesquioxide  in  caustic  soda 
and  exposing  it,to  the  air,  the  caustic  alkali  being  thus  converted  into  carbonate,  which  precipitates  the  sesquioxide 
of  chromium  ;  instead  of  exposure  to  the  air,  the  action  of  steam  may  be  employed.  Chromous  oxide  is  precipi- 
tated by  simple  washing  of  the  impregnated  tissue  with  a  tin  salt.  Sulphoricinate  is  fixed  by  solutions  of  aluminium 
salts  and  tannin  by  solutions  of  tartar  emetic  or  ferric  or  aluminium  salts. 

The  action  of  a  chromate  bath  or  catechu  is  twofold  ;  first,  the  catechu  undergoes  oxidation  with  considerable 
darkening,  and  then  combination  takes  place  between  the  oxidation  product  and  the  chromium  sesquioxide 
resulting  from  the  reduction  of  the  chromate. 

1  At  first  France  was  at  the  head  of  the  aniline  dye  industry,  with  numerous  pioneers,  such  as  Verguin,  Renard 
Brothers,  Frank,  Poirrier,  Guinon  Mamas  and  Bonnet,  Coupler,  Girard  and  de  Laire,  Baubigny,  Persoz,  Bardy, 
Lauth,  Kopp,  Rosenstiel,  Roussin,  <fec.,  but  of  all  these  very  few  have  been  able  to  withstand  the  wonderful  organi- 
sation of  the  large  German  manufacturers.  Even  England,  the  cradle  of  the  industry,  is  now  in  a  position  greatly 
inferior  to  that  of  Germany.  The  six  English  factories  now  working  employ  altogether  35  chemists,  while  the  six 
largest  German  firms  employ  600,  besides  350  engineers  and  technical  directors.  From  1886  to  1900,  the  English 
firms  took  out  86  patents,  while  the  six  more  important  German  ones  took  out  948. 

The  principal  English  firms  to-day  producing  dyes  are  :  Brooke,  Simpson,  and  Spiller,  London  ;  The  Clayton 
Aniline  Company,  Manchester ;  Read,  Holliday,  and  Sons,  Limited,  Huddersfield  ;  and  I.  Levinstein  and  Company, 
Limited,  Manchester. 

The  German  firms  which  enjoy  almost  a  monopoly  of  the  world's  trade  in  aniline  colours  are :  (1)  Badische 
Anilin-  und  Soda-Fabrik,  Ludwigshafen ;  (2)  Farbenfabriken  vormals  Fr.  Bayer  und  Co.,  Elberfeld ;  (3)  Farb- 
werke  vormals  Meister,  Lucius  und  Briining,  Hochst ;  (4)  Leopold  Cassella  and  Co.,  Frankfort ;  (5)  Actien-Gesell- 
schaft  fur  Anilin-Fabrikation,  Berlin  ;  (6)  Kalle  and  Co.,  Biebrich  ;  of  less  importance  are  the  firms  of  Oehler  in 
Offenbach,  Leonhardt  of  Mulheim,  &c.  Firms  (1),  (2),  and  (5)  work  together  to  regulate  the  output  and  trade, 
and  the  same  is  the  case  with  (3),  (4),  and  (6). 

In  point  of  magnitude,  the  German  firms  are  immediately  followed  by  those  of  German  Switzerland  (Basle) : 
Gesellschaft  fur  chemische  Industrie  ;  Durand,  Huguenin  and  Co. ;  Geigy  ;  Kern  and  Sandoz,  &c. 

Of  the  German  factories,  the  Badische  Anilin-  und  Soda-Fabrik  alone,  with  a  capital  of  over  £1,400,000,  employed 
in  1908  about  8000  workmen  (in  1896  less  than  5000  and  in  1865,  the.  first  year  of  working,  30),  and  more  than 
160  chemists  and  75  engineers  ;  for  more  than  twenty  years  the  dividends  paid  by  this  company  have  been  about 
25  per  cent. 

The  Bayer  Company  of.  Elberfeld  employs,  in  its  various  works,  170  chemists,  35  engineers,  and  about  6000 
workmen.  Its  principal  works  were  originally  at  Elberfeld,  but  the  most  important  of  their  manufactures — colour- 
ing-matters, pharmaceutical  and  photographic  materials — were  transferred  several  years  ago  to  a  new  factory  at 
Leverkusen,  near  Cologne,  which  occupies  an  area  of  529  hectares  and  finds  employment  for  4000  workpeople. 
Some  mention  may  be  made  here  of  the  conditions  under  which  the  operatives  work  and  the  benefits  they  enjoy- 
Leaving  out  of  account  the  fact  that  the  average  wage  of  the  workmen  is  more  than  five  shillings  per  day,  the 


MANUFACTURE    OF    DYESTUFFS 


653 


The  dye  industry,  although  not  born  on  German  soil,  has  there  reached 
its  greatest  development  and  borne  its  richest  fruit,  far  in  excess  of  the  dreams 
of  its  founders.  This  result  has  been  reached  in  Germany  as  a  result  of  various 
fortunate  circumstances. 

This  industry  does  not  confine  itself  to  the  application  or  development 
of  discoveries  made  here  and  there  by  individual  scientific  workers,  but  has 
made  itself  a  centre  of  research.  The  industry  has  its  own  laboratories,  which 
have  nothing  to  distinguish  them  from  those  of  the  more  important  universities 
and  contain  hundreds  of  chemists  controlled  by  renowned  directors.  By  this 
means  it  has  been  possible'  to  accumulate  many  details  of  great  practical 
importance,  which  escaped  those  prosecuting  research  in  university  laboratories . 
Such  rational  systematisation  of  specialised  scientific  research  in  a  single  branch 
of  industry  has  cost  enormous  sums,  but  has,  at  the  same  time,  borne  fabulous 
fruits.  The  investigations  and  discoveries  made  in  these  establishments 
are  of  great  advantage  to  science  itself,  opening  up  new  fields  of  study  and 
completing  and  generalising  rudimentary  rules  so  that  they  become  positive 
laws. 

The  prime  materials  for  dyes  are  the  various  aromatic  hydrocarbons 
obtained  from  tar,  which  may,  however,  be  first  transformed  into  substances 
more  active  chemically  (phenols,  amines,  &c.). 

The  fundamental  reactions  to  which  the  distillation  products  (benzenes, 
phenols,  naphthalene,  pyridine,  &c.)  of  tar  are  subjected  consist,  in  general,  of 

company,  starting  from  the  idea  that  the  employer  owes  to  the  employee  more  than  his  wages,  has  created  a  number 
of  institutions  which  now  represent  a  total  capital  of  £600,000.  Among  these  is  a  library  of  12,000  volumes  used 
by  44  per  cent,  of  the  workpeople,  the  books  demanded  in  1907  consisting  of  popular  works  on  scientific  subjects 
to  the  extent  of  52  per  cent,  and  of  miscellaneous  literature  to  the  extent  of  48  per  cent. ;  the  library  committee 
consists  of  chemists,  engineers,  and  workmen.  Five  hundred  baths  have  been  built,  150,000  baths  being  taken 
annually.  There  are  dormitories  with  beds  at  2$d.  per  night,  refectories  which  supply  the  three  meals  of  the  day 
to  men  for  a  shilling  and  to  boys  and  girls  for  9d.  There  are  also  free  technical  schools  and  schools  of  art  and  music. 
A  lying-in  hospital  (also  for  wives  of  workmen  not  employed  in  the  factory)  cost  £7200,  the  annual  expenses  being 
£1600.  A  hall  for  theatrical  performances  and  conferences,  another  for  lectures,  concerts,  <fec.,  and  a  third  for 
conferences  of  workmen,  cost  £18,000.  There  are  sickness  funds,  savings  banks,  and  a  life  insurance  scheme, 
supported  to  the  extent  of  two-thirds  by  the  funds  of  the  company ;  also  old-age  pensions,  and  accident  funds 
in  addition  to  the  State  fund,  the  company  paying  for  the  first  three  days  after  the  accident  (not  paid  by  the  insu- 
rance companies)  and  supplementing  the  legal  payment  by  50  per  cent.  The  sale  of  alcoholic  drinks — beer  included 
— -is  forbidden  in  the  refectories,  but  coffee,  tea,  milk,  <fec.,  are  obtainable  at  very  low  prices.  On  all  these  institu- 
tions the  Bayer  Company  spends  more  than  £80,000  and  is  yet  able  to  pay  its  shareholders  a  dividend  of  25  to 
30  per  cent,  on  a  capital  of  £1,200,000. 

The  scientific  and  technical  work  of  the  company  is  indicated  in  the  4000  patents  filed  up  to  the  year  1907. 

Many  of  the  Russian  and  French  factories  are  branches  of  German  ones. 

In  spite  of  the  optimistic  views  sometimes  expressed,  it  does  not  seem  possible  to  start  an  aniline  dye  factory 
in  Italy,  especially  as  even  in  England,  which  is  situated  far  more  favourably  as  regards  raw  materials  and  fuel, 
this  industry  has  not  been  able  to  compete  seriously  with  Germany. 

Statistics.  Germany  now  supplies  six-sevenths  of  the  world's  requirements  in  artificial  organic  dyes  (although 
importing  from  Switzerland  special  dyes  to  the  value  of  £200,000  to  £250,000),  and  the  progress  of  the  industry 
is  clearly  shown  by  the  following  data  concerning  the  exports : 


1880 

1890 

1895 

1900 

1905 

1907 

1909 

Aniline  dyes    .  tons 
Alizarin  dyes   .     ,, 
Indigo     .         .     „ 

2,141 
5,588 
497 

7,280 
7,906 
733 

15,789 
8,928 
658 

23,781 
8,591 
1,873 

36,570 
9,339 
11,165 

43,716  (£5,600,000) 
10,500  (£1,200,000) 
16,350  (£2,160,000) 

47,777 
34,784 
£2,000,000 

To  the  total  of  £8,960,000  (in  1907)  must  be  added  £1,200,000  for  various  crude  materials  (aniline  oil  and  salts) 
for  the  manufacture  of  dyes  abroad. 

Switzerland,  with  six  factories  in  the  canton  of  Basle,  has  a  capital  of  £560,000  invested  in  the  manufacture 
of  dyes,  which  occupies  2000  workpeople  and  exported  60,000  quintals  of  dyes,  of  the  value  of  £880,000,  in  1906  ; 
in  1910  the  value  of  the  exports  exceeded  £1,000,000,  although  in  1903  it  was  not  more  than  £680,000. 

In  1905  Italy  imported  40,820  quintals  of  aniline  dyes  in  powder  and  4300  in  paste  (excluding  indigo  and  extracts 
of  dye-tfoods),  of  a  total  value  of  £532,000  (£400,000  from  Germany  and  the  rest  almost  aJl  from  Switzerland).  In 
1900  the  value  of  the  imported  dyes  was  about  one-third  less  than  the  above,  while  53,000  quintals  were  imported 
in  1908,  61,890  in  1909,  and  about  53,560,  besides  5500  of  pasty  dyes,  in  1910. 

Other  countries  imported  from  Germany  in  1907  the  following  quantities  of  aniline  dyes,  at  an  average  price 
of  £12  to  £13  per  quintal :   England,  9048  tons  ;   United  States,  10,670  ;   Austria-Hungary,  2980  ;  France,  1035 
Russia,  1269  ;   Japan,  2649  ;   China,  3476  ;   India,  2040  ;   Belgium,  1490  ;    Switzerland,  680. 

In  1909  the  value  of  the  aniline  dyes  imported  into  China  was  £280,000,  that  of  the  natural  indigo  £28,000, 
and  that  of  the  artificial  indigo  £520,000. 


654  ORGANIC    CHEMISTRY 

nitration,  reduction,  diazotisation,  sulphonation,  fusion  with  caustic  soda, 
chlorination,  and  oxidation. 

These  reactions  lead  to  intermediate  products  very  near  to  the  true  colouring- 
matters.  Thus,  nitrobenzene  and  its  homologues  yield  aniline,  toluidine,  &c., 
by  simple  reduction  with  iron  turnings  and  hydrochloric  acid,  and  aniline 
then  gives  diphenylamine,  dimethylaniline,  sulphanilic  acid,  &c. 

Oxidation  of  aniline,  toluidine,  &c.,  gives  fuchsine,  safranine,  methyl 
violet,  &c.  The  nitroanilines  serve  for  the  preparation  of  azo-dyes,  while 
the  action  of  sulphur  on  amines  leads  to  primuline  and  the  new  class  of  sulphur- 
dyestuffs. 

With  another  reducing  agent  (Zn  +  KOH),  nitrobenzene  gives  other 
products  (hydrazobenzenes,  &c.),  from  which  other  classes  of  colouring- 
matters  originate. 

A  further  important  reaction  consists  in  the  introduction  of  sulphuric  acid 
residues  (Sulphonic  Group,  S03H)  into  benzene  nuclei  in  place  of  hydrogen 
or  other  groups  by  treatment  of  benzene  derivatives  with  concentrated  sulphuric 
acid.  The  resulting  sulphonic  acids  are  of  great  importance  and  often  decide 
whether  a  dyestuff  is  acid  in  character  and  hence  able  to  dye  wool  and  silk 
directly  in  an  acid  bath,  or  neutral  (or  almost  so)  and  capable  of  colouring 
cotton  directly,  or  still  basic  and  able  to  dye  cotton  mordanted  with  tannin 
or  wool  and  silk  directly  in  a  neutral  or  faintly  alkaline  bath. 

The  sulphonic  group,  in  its  turn,  may  be  replaced  by  hydroxyl  by  fusion 
of  the  sulphonic  acid  with  caustic  soda,  this  being  a  very  important  reaction, 
as  it  allows  of  the  ready  preparation  of  resorcinol  and  of  Alizarin.  The  OH 
group  may  also  be  introduced  into  the  molecule  directly  by  means  of  the 
Bohn-Schmidt  reaction,  which  consists  in  treating  various  substances  in  the 
hot  with  sulphur  trioxide  dissolved  in  concentrated  sulphuric  acid. 

Oxidation  is  likewise  of  great  value  and  was  first  used  for  preparing  fuchsine, 
safranine,  &c.  It  has  now  been  found  that  naphthalene  can  be  oxidised  with 
sulphuric  acid  in  presence  of  mercury,  giving  phthalic  and  anthranilic  acids  at 
a  cost  so  low  as  to  admit  of  the  competition  of  artificial  Indigo  with  the 
natural  product  (see  p.  643). 

The  methods  of  dyeing  textile  fibres  are  becoming  continually  more  simple 
and  more  certain  and  capable  of  giving  the  most  varied  colours.  Nowadays 
stable  dyes  can  be  produced  directly  on  the  cotton  fibre  in  a  single  operation, 
starting  with  simple  chemical  reagents.  The  ideal  method  would  be  for  the 
manufacturers  of  chemical  products  to  furnish  reagents  to  the  dyer  so  that  the 
desired  colours  could  be  made  directly  on  the  tissues. 


CLASSIFICATION  OF  COLOURING-MATTERS 

Nietzki  divides  the  artificial  organic  colouring-matters  into  the  following 
general  groups,  with  reference  especially  to  their  chemical  composition  : 

I.  Nitro-  colouring-matters.  II.  Azo-  colouring-matters.  III.  Derivatives 
of  hydrazones  and  pyrazolones.  IV.  Hydroxyquinones  and  quinoneoximes . 
V.  Diphenyl-  and  triphenyl-methane  colouring-matters.  VI.  Derivatives  of 
quinonimide.  VII.  Aniline  black.  VIII.  Quinoline  and  acridine  derivatives. 
IX.  Thiazole  colouring-matters.  X.  Oxyketones,  xanthones,  flavones,  and 
coumarins.  XI.  Indigo  and  similar  and  other  natural  colouring-matters. 
XII.  Sulphur  colouring-matters. 

But  for  practical  dyeing,  more  importance  is  attached  to  the  division  into 
the  following  five  groups  on  the  basis  of  the  behaviour  of  the  colouring-matters 
towards  different  textile  fibres,  since  in  practice  it  is  more  important  to  know 
if  a  colouring-matter  is  basic  or  acid  or  if  it  dyes  with  or  without  mordant, 
than  to  know  if  it  is  a  nitro-compound,  quinone,  hydrazone,  &c.  : 


CLASSIFICATION    OF    DYESTUFFS         655 

1.  Basic  colour  ing -matters,  which  in  a  neutral  bath  dye  animal  and  vege- 
table fibres ;   the  latter  should,  however,  be  previously  mordanted  with  tannin. 

2.  Acid  colouring-matters,  which  dye  animal  fibres  in  an  acid  bath. 

3.  Adjective  or  mordant  colouring -matters,  which  dye  fibres  mordanted  with 
metallic  oxides  (of  iron,  chromium,  aluminium,  &c.). 

4.  Almost  neutral  or  substantive  colouring -matters,  which,  as  alkali  salts,  dye 
vegetable  textile  fibres  directly,  without  mordanting. 

5.  Insoluble  colour  ing -matters  or  pigments  are  formed  directly  on  the  fibre, 
i.e.  are  used  for  vat-dyeing  or  are  developed  on  the  fibre. 

I.  NITRO-  COLOURING -MATTERS.     All  the  nitro-derivatives  of  the  amines  and 
phenols   are    energetic    clyestuffs,  those  of  the  phenols  especially  being  markedly  acid 
colouring- matters,  since  the  Chromophore  NO2  reinforces  the  acid  character  of  the  OH 
group.    Even  the  basic  substances  may  become  acid  if  many  NO2  groups  are  present.    It  is 
particularly  the  salts  of  these  compounds  which  are  coloured  ;  p-nitrophenol,  for  example, 
is  colourless  while  its  salts  are  yellow. 

The  coloration  of  the  nitrophenols  disappears  if  the  phenolic  groups  are  etherified  by 
alkyl  groups. 

Of  the  nitrophenols  the  ortho-products  (OH  :  NO2  =1:2)  are  the  more  important 
and  the  more  highly  coloured.  Examples  are :  Picric  Acid  (trinitrophenol),  C6H2(N02)3-OH  ; 
Naphthol  Yellow  S  =  dinitronaphtholsulphonic  acid,  C10H4(NO2)(NO2)(OH)(SO3H) 
(2:4:1:7)  ;  Victoria  Yellow  (or  Victoria  orange)  =  dinitrocresol,  C6H2(OH)(CH3)(NO2)2. 

II.  AZO-  COLOURING-MATTERS.    The  azo-  colouring- matters,  unlike  other  groups, 
have  retained  their  original  importance,  not  only  as  regards  the  number  that  can  be 
produced,  but  especially  because  the  gradations  of  colour  and  the  stability  can  be  modified 
at  will.     Thus,  the  azo-group  includes  substantive  dyestuffs,  which  dye  cotton  without  a 
mordant,  wool  colouring-matters  fast  to  milling  and  to  sulphuring,  and  stable  adjective 
dyes  such  as  alizarin. 

Their  basic  chromophore  is  — N=N —  and  the  chromogen,  R — N=N — R',  R  andR' 
being  aromatic  radicals. 

These  compounds  form  the  largest  and  perhaps  the  most  important  group  of  artificial 
colouring-matters.  They  are  not  of  themselves  (especially  in  the  case  of  the  more  simple 
ones,  such  as  azobenzene)  intense  dyestuffs,  but  they  become  such  on  the  introduction 
into  the  benzene  nuclei  of  acid  (OH)  or  basic  (NH2)  auxochromes,  and  with  increase  of 
the  number  of  these  the  intensity  increases,  passing  from  yellow  to  red,  to  blue  or  to  brown. 
Blues  are  obtained  with  several  chromophores  — N=«N —  (di-  and  tetra-azo-compounds), 
while  naphthalene  groups  give  reds.  The  higher  the  molecular  weight  the  more  intense 
becomes  the  colour. 

In  certain  cases  it  must  be  assumed  that  these  auxochromes  are  united  in  some  way 
with  the  chromophore,  and,  since  /3-naphthazobenzene  no  longer  exhibits  phenolic  character, 
Liebermann  attributed  to  it  the  structure  C6H5 — NH — N  —  C^H^,  instead  of  the  ordinary 


O 

constitutional  formula  C6H5  •  N  :  N  •  CjoHg  •  OH. 

Certain  azo-compounds  show  behaviour  recalling  that  of  quinones  and  ketones,  e.g. 
they  combine  with  sodium  bisulphite.  In  such  case,  the  formula  is  represented  thus : 
C«H5-NH-N  :  C6H10O. 

Almost  all  azo-compounds.  dissolve  in  concentrated  sulphuric  acid,  giving  a  charac- 
teristic coloration,  which,  in  general,  serves  for  their  recognition  and  distinction  from  other 
colouring- matters  (see  Table  given  later). 

Substituted  azo-compounds  are  always  obtained  by  coupling  a  diazo- compound  with 
a  phenol  or  with  an  amine,  and,  in  the  latter  case,  diazoamino- compounds  are  formed  as 
intermediate  products. 

The  first  azo-dyestuff  of  industrial  importance  (triaminoazobenzene)  was  prepared 
in  1867  by  Caro  and  Griess,  and  it  was  only  with  the  dyes  discovered  by  Witt  and  Roussin 
subsequently  to  1876  that  this  group  assumed  a  position  of  practical  importance. 

After  1880  azo-  colouring- matters  again  came  to  the  front  owing  to  the  preparation  of 
direct  dyes  for  cotton,  and  later  these  dyes  were  produced  directly  on  the  cotton  fibre, 
new  dyeing  methods  being  thus  created. 


656 


ORGANIC    CHEMISTRY 


They  are  prepared  industrially  by  first  diazotising  the  amine,  or  its  sulphonic  acid 
diluted  with  water,  by  means  of  hydrochloric  acid  and  sodium  nitrite,  the  mass  being 
cooled  with  ice  and  tested  with  starch-potassium  iodide  paper  so  as  to  avoid  any  large 
excess  of  nitrite.  After  diazotisation,  the  coupling  is  carried  out  by  pouring  the  whole 
slowly  into  an  alkaline  solution  of  the  phenol,  the  mass  being  kept  alkaline.  The  colouring- 
matter  thus  formed  is  separated  in  an  insoluble  state  on  addition  of  salt  and  is  then  filter- 
pressed.  The  reaction  between  the  amines  and  the  diazo- compounds  is  more  complex  : 

R-NH2)HC1(  +  £N203)  >  R-NC1  :  N(  +  R'-OH,  phenol)  >  HC1+R-N  :  N-R'-OH. 

The  diazo-group  enters  in  the  para-position  to  H,  OH,  or  NH2,  or  if  this  is  occupied,  in 
the  ortho-position. 

Azo-  colouring-matters  are  so  numerous  and  so  varied  in  constitution  and  behaviour 
that  they  may  be  divided  into  several  sub-groups. 

The  MONOAZO-COMPOUNDS  may  be  sulphonated  (aminoazo-derivatives  give 
basic  colouring- matters  and  the  hydroxyazo-derivatives  without  carboxyl,  acid  colouring- 
matters)  or  not  sulphonated  (the  aminoazo- compounds  give  basic  and  acid  colouring- 
matters  and  the  hydroxyazo- compounds  basic  and  adjective  colouring-matters).  POLY- 
AZO-COMPOUNDS  yield  substantive  and  adjective  dyestuffs  (i.e.  without  benzidine 
nuclei  and  then  form  acid,  basic,  and  mordant  colouring- matters).  Finally  theic  is  the 
sub-group,  the  members  of  which  are  generated  directly  on  the  cotton  fibre. 

(a)  Aminoazo-derivatives.     These  are  obtained  in  the  usual  way,  in  the  cold  and  in 
alkaline  solution,  from  diazo-compounds  (amino-  or  not)  and  amines. 

Among  these  are  fast  yellow,  acid  yellow,  tropceolin,  the  oranges,  Indian  yellow  (nitro- 
derivative  of  phenylaminoazobenzenesulphonic  acid),  orange  IV  or  tropceolin  00  (sodium 
salt  of  the  non-nitrated  product,  S03H-C6H4-N  :  N-C6H4-NH-C6H5)  and  vesuvine 
or  Bismarck  brown,  which  is  the  hydrochloride  of  triaminoazobenzene,  NH3-C6H4-N  : 
N-C6H3(NH2)2,  mixed  with  C6H4[-N  :  N-C6H3(NH2)2]2. 

Indoin  is  a  basic  blue  obtained  by  coupling  diazotiscd  safraninc  with  /3-naphthol. 

On  textiles  they  are  not  very  fast  to  light,  the  less  fast  being  those  which  do  not  contain 
the  sulphonic  group.  In  printing  textiles  these  colours  are  corroded  by  the  stannous 
chloride. 

(b)  Hydroxyazo-derivatives       (or      azoxy-compounds),       e.g.       hydroxyazobenzcne, 
C6H6'N  :  N'C6H4'OH.     Tropceolin  0  is  a  dihydroxyazobenzenesulphonic  acid. 

N:N- 


Of  greatest  importance  are  the   derivatives  of  a-  and  /5-naphthols, 


(a) 


N:  N- 
/\/\OH 


OH 


and 


(/3),  the  compounds  with  the  auxochrome  in  the  ortho  :  /3-position  with 


respect  to  the  chromophore  (-N  :  N-)  being  colouring-matters  of  greater  fastness  to  acid 
and  alkali  than  the  ortho- :  u-compounds.     But  if  another  azo  group  be  introduced  into  the 

OH 


latter,  it  will  occupy  the  /3-(ortho)-position, 


N  :  N- 


,  the  fast  brown  dyestuffs 


N  :  N- 
being  obtained. 

Those  most  used  are  the  sulphonic  derivatives,  obtained  from  various  naphtholsulphonic 
acids.  s 

Of  the  numerous  colouring-matters  of  this  group,  the  most  important  are  :    orange  II 
tropceolin  OOO  N.  II  or  N.  I,  croceine  orange,  orange  G,  &c.,  Ponceau  (various),  Bordeaux  S, 

N-C,0H6.S03H      (4), 


amaranth,  rocelline,  croceine,  azorubin  S   I   j 


>  &c. 


BENZIDINE  657 

(c)  Azo-  Colouring-Matters  derived  from  Carboxylic  Acids  are  obtained  from  carb- 
oxylic  diazo-compounds  and  phenols  or  amines. 

These  compounds  (especially  the  o-hydroxycarboxylic  acids,  such  as  salicylic  acid) 
have  an  affinity  for  metallic  mordants,  particularly  for  chromium  oxide.  The  hydroxyl 
and  carboxyl  groups  are  in  the  ortho-positions. 

Among  the  nitrobenzeneazosulphonic  acids  are  alizarin  yellow,  the  diamond  yellows,  &c., 
which,  on  cotton  and  wool,  give  colours  very  resistant  to  light  and  to  fulling.  The  hydroxy- 
azo-acids  include  various  tropseolins  (V,  B,  0,  OOO,  &c.),  chrysoin,  cochineal  scarlet, 
ponceau,  palatine  scarlet,  &c. 

(d)  Azo- Colouring-Matters  derived  from  Dihydroxynaphthalenes.  Several  of  these 
compounds  are  fixed  by  mordants  when  they  have  two  hydroxyl  groups  in  the  ortho-  (1  :)  2 

OH  OH 


peri-    (1:8)   position,    as    in   anthraquinone    (see   Alizarin)  and  .     But 


S03H 

these  compounds  are  used  practically,  not  on  mordants,  but  for  the  dyeing  of  wool,  as  they 
give  very  regular  results  (such  are  the  azofuchsines),  while  the  peridihydroxynaphthalenes 
are  used  on  mordants  and  form  the  so-called  chromotrop  colouring- matters,  which  dye 
unmordanted  wool  in  an  acid  bath,  giving  a  fine  red  turned  violet  by  addition  of  alumina 
mordants  or  blue- black  with  chrome  mordants. 

POLYAZO-  COLOURING-MATTERS  (di-  and  tetra-azo)  contain  the  chromophore 
•X  :  N-  several  times  and  vary  according  as  the  chromophores  are  in  the  same  benzene 
nucleus  or  in  different  nuclei  and  as  the  auxochromes  are  or  are  not  in  the  same  nuclei 
as  the  chromophores. 

Here  are  found  benzidine  derivatives  in  which  the  two  chromophores  are  in  two  different 
nuclei,  joined  by  a  single  linking. 

Among  the  sulphonic  derivatives  are,  for  example,  Biebrich  scarlet,  and  the  croceines, 
while  among  the  polyazo-compounds  are  also  naphthol  black,  naphthylamine  black  D, 
diamond  black  (which  is  obtained  from  aminosalicylic  acid  and  is  fixed  by  mordants),  &c. 


BENZIDINE,  NH2<^  /NH2,  when  treated  with  nitrous  acid,  gives 

a  tetrazo-derivative  which  yields  yellow,  red,  blue,  or  violet  colours  on  combination  with 
amines  or  phenols.  With  naphthionic  acid,  tetrazodiphenyl  gives  Congo  red,  which  was 
the  first  substantive  dyestuff  obtained  and  was  patented  by  C.  Bb'ttiger  in  1884  : 


the  free  sulphonic  acid  is  blue  while  the  salts  are  red  and  are  ixed  directly  on  cotton, 
but  have  the  disadvantage  of  becoming  blue  or  black  in  contact  with  even  weak 
acids. 

The  Benzopurpurins  (see  p.  605)  are  obtained  in  a  similar  manner. 

These  benzidine  derivatives  cease  to  form  substantive  colouring-matters  if  the  meta- 
positions  (with  respect  to  the  NH2)  are  occupied. 

Substantive  or  direct  colours,  when  fixed  on  cotton,  function  as  weak  mordants  for  basic 
dyestuffs. 

The  different  firms  making  colouring  -matters  place  on  the  market  a  large  number  of 
substantive  dyes  under  various  names.  For  instance,  Messrs.  Casella  have  a  long  and 
important  series  of  diamine  colours  (diamine  yellow,  green,  red,  black,  blue,  &c.),  while 
Meister,  Lucius  und  Briining  call  their  substantive  colouring-  matters  dianil  colours. 
The  Bayer  Company  have  the  most  numerous  and  important  series  of  substantive  dyes, 
which  they  term  benzidine  or  benzo  dyestuffs  (e.g.  benzo  azurines,  benzo  browns,  benzo 
reds,  &c.).  The  Actien-Gesellschaft  fur  Anilin-Fabrikation,  Berlin,  call  these  dyes 
Columbia,  Zambesi,  &c. 

II  42 


658  ORGANIC    CHEMISTRY 

o 


The  Derivatives  (e.g.  sulphonic)  of   azoxystilbene,    C6H4<^  /C6H4,  have  the 

>0  =  (X 

H      H 

special  property  of  dyeing  cotton  directly  in  an  acid  bath. 

The  firm  of  Meister,  Lucius  und  Briining,  in  1896,  placed  on  the  market  a  class  of 
strongly  basic  colouring-matters  (Janos  dyes),  which  colour  cotton  directly — without 
previous  mordanting — in  an  acid  bath  and  also  dye  with  the  same  colour  the  wool  and  cotton 
of  a  mixed  fabric  when  the  latter  is  boiled  in  a  bath  acidified  with  sulphuric  acid.  These 
dyes  change  their  tint  temporarily  if  brought  into  contact  with  hot  objects  (hot  iron). 

Of  very  great  importance  is  the  group  of  azo-dyes  produced  directly  on  the  fibre  by 
processes  of  diazotisation  and  combination,  these  bearing  the  name  of  Ingrain  Colours. 

Cotton  fabrics  or  yarns  are  impregnated  in  the  cold  with  a  base  (aniline,  p-nitraniline, 
aminoazobenzene,  benzidine,  safranine,  &c.)  or  they  may  be  first  dyed  with  one  of  the 
substantive  tetrazo-dyes  containing  free  auxochrome  amino-groups  (e.g.  diamine  black, 
primuline  yellow,  benzo  brown,  blue,  or  black,  &c.).  They  are  then  transferred  for  15 
minutes  to  a  wooden  vessel  containing  a  cold  diazotising  solution,  this  consisting,  per  100 
kilos  of  cotton,  of  2000  litres  of  water,  2  to  4  kilos  of  sodium  nitrite,  and  6  to  10  kilos  of 
hydrochloric  acid  at  20°  Be.  ;  this  diazotisation  is  carried  out  in  dimly  lighted  rooms, 
since  sunlight  readily  decomposes  the  diazo-compounds  formed.  After  removal  from  this 
bath,  the  cotton  is  allowed  to  drain  for  a  short  time  and  is  then  placed  in  a  developing  bath 
(coupling  bath)  containing  2000  litres  of  water,  0-5  kilos  of  sodium  carbonate  and  0-5  to 
1  kilo  of  /3-naphthol  previously  dissolved  in  415  to  430  grms.  of  caustic  soda  at  40°  Be. 
The  cotton  is  manipulated  rapidly  and  in  a  few  minutes  intense  development  of  the  colour 
takes  place.  When  substantive  dyestuffs  are  thus  further  diazotised  on  the  fibre,  they 
exhibit  increased  fastness  to  scouring,  and  this  is  still  more  the  case  if  the  fabric  is  subse- 
quently treated  with  a  bath  of  potassium  or  sodium  bichromate  at  90°  to  95°  for  20  minutes  ; 
a  final  copper  sulphate  bath  at  50°  for  25  minutes  gives  greater  fastness  to  light  ;  but  both 
«opper  and  chromium  compounds  diminish  the  brightness  of  the  colour  to  some  extent, 
and  on  this  account  the  firm  of  Geigy  suggests  the  use  of  a  final  bath  of  formalin.  Instead 
of  /3-naphthol,  a-naphthol,  resorcinol,  phenylenediamine,  benzonitrole  (diazotised  p-nitrani- 
line), &c.,  may  be  used.  By  this  method  of  diazotising  and  developing  on  the  fibre  the 
original  tint  of  the  basic  substance  is  intensified,  certain  yellows  become  orange  or  scarlet 
•(p-nitraniline  gives  with  /3-naphthol  a  fine  scarlet  similar  to  Turkey  red,  while  with  a-naph- 
thol it  yields  a  violet-red),  certain  reds  become  brown  or  even  blue,  the  blues  become  intense 
blacks,  &c.  Different  developers  give  different  colours  or  shades. 

The  coupling  of  a  phenol  with  a  diazo-compound  is  prevented  by  the  presence  of  a 
reducer  which  destroys  the  latter  ;  as  reducing  agent  stannous  chloride  was  at  one  time 
used,  but  use  is  now  made  of  sodium  or  zinc  hydrosulphite,  which  permits  of  the  printing 
of  textiles  in  white  designs  on  a  coloured  ground. 

III.  HYDRAZONE  AND  PYRAZOLONE  COLOURING-MATTERS.  Hydrazones 
.are  obtained  by  the  action  of  phenylhydrazine,  C6H5-NH-NH2,  on  compounds  con- 
taining ketonic  groups  (see  p.  210).  Thus,  for  example,  the  condensation  of  phenyl- 

CO 


hydrazine  with  a-naphthaquinone, 


gives  a  hydrazone  of  the   constitution 


CO 

•C6HB  •  NH  •  N  :  CVoHe  :  0.  The  same  compound  is  obtained  by  the  interaction  of  a-naphthol 
.and  diazobenzene,  so  that  its  constitution  might  be  that  indicated  by  the  equation  : 

C6H6-N2-C1  +  CioHT-OH  =  HC1  +  C6H5-N  :  N-QoHe-OH, 

one  hydrogen  atom  being  mobile  and  oscillating  between  nitrogen  and  oxygen.  The 
hydrazones  may  hence  be  regarded  as  azo-compounds  and  can  be  prepared  from  diazo- 
•derivatives  and  phenols.  This  is  true  for  aromatic  compounds  (which  can  be  diazotised), 


QUINONE    DYE  STUFFS  659 

but  not  for  those  of  the  aliphatic  series,  which  are  only  exceptionally  diazotised  ;   in  the 
latter  case,  the  hydrazones  must  be  obtained  by  means  of  phenylhydrazine. 

The  colouring-matters  of  the  hydrazone  group  have  not  as  yet  been  practically  applied, 
as  they  are  too  weak.  It  was  formerly  thought  that  tartrazin  was  a  hydrazone,  but 
Anschiitz  showed  it  to  be  a  pyrazolone.  In  general  the  Tartrazins  are  obtained  by  con- 
densing, in  hot  acid  solution,  the  aromatic  hydrazines  (sulphonated)  with  dihydroxy- 
tartaric  acid,  CO2H'C(OH)2-C(OH)2'CO2H,  which  probably  reacts  with  phenylhydrazine 

CO2H-C  :  N-NH-C6H4-SO3H 
as     a    true    di-ketone,     C02H  •  CO  •  CO  •  CO2H,     giving  ; 

C02H-C :  N-NH-C6H4-S03H 
a  molecule  of  water  is  then  lost  from  a  carboxyl-  and  an  imino-group, 

/N(C6H4-S03H)-CO 

<  1 

— C(CO2H) C  :  N  •  NH  •  C6H4  •  SO3H. 

The  sodium  salt  is  used  as  a  fast  yellow  for  wool,  in  an  acid  bath.  Some  tartrazin 
nitrates  are  fixed  also  by  mordants.  In  an  acid  bath  tartrazin  dyes  wool  a  bright  and 
fairly  fast  yellow. 

IV.  COLOURING-MATTERS  DERIVED  FROM  QUINONES  AND  QUINON- 
OXIMES.  All  these  colouring-matters  give  very  fast  tints  on  fibres  mordanted  with 
metallic  oxides  with  which  they  form  lakes.  If  the  hydroxyl  groups  present  are  not  in  the 
ortho-position  with  respect  to  one  another  and  to  the  chromophore  C0<^ ,  the  lakes 
formed  have  no  affinity  for  the  fibres.1 

The  most  important  colours  of  this  group  are  formed  by  introducing  into  the  chromo- 
phores,  naphthalene  groups  ;  e.g.  Naphthazarin,  which  is  a  dihydroxynaphthaquinone, 


The  quinonoximes  contain  the  group  :  N-OH  in  place  of  the  ketonic  oxygen  ;  they 
have  properties  similar  to  the  hydroxyquinones,  and  here  too  the  affinity  for  metallic 
mordants  is  most  marked  in  the  derivatives  of  the  orthoquinones.  A  few  colouring- 
matters  derived  from  the  oxime  0=\  j>=NOH,  are  known,  e.g.  fast  green  for  cotton, 


naphthol  green,  &c. 

Among  these  quinone  derivatives  are  almost  all  the  alizarin  (see  p.  617)  and  anthracene 
(see  p.  615)  colouring-matters,  purpurin,  &c.,  in  all  gradations  from  yellows  to  reds,  blues, 
blacks,  greens,  &c. 

For  hundreds  of  years  Alizarin  was  the  sole  representative  of  a  group  of  excellent 
colours,  and  was  only  obtained  naturally  mixed  with  purpurin,  from  which  it  was  separated 
with  difficulty.  Nowadays,  not  only  is  alizarin  prepared  artificially,  but  there  are  quite 
fifty  other  colouring-matters  of  this  group,  fast  to  light  and  chemical  and  atmospheric 
reagents. 

And  while  nature  yields  colours  such  as  madder  and  indigo  in  an  impure  condition 
(as  these  are  secondary  products  of  vegetable  life)  and  not  directly  applicable  for  dyeing, 
the  artificial  products  are  highly  pure,  much  brighter  in  colour  and  more  easily  utilisable 
as  dyes. 

Alizarin  and  anthracene  dyes,  which  are  the  prototypes  of  mordant  colouring -matters, 
are  used  in  large  quantities  for  the  fast  dyeing  of  wool  for  clothing  and  military  uniforms. 
As  a  rule  the  wool  is  mordanted  first,  by  boiling  for  an  hour  with  an  aqueous  solution 
containing  2  to  3  per  cent,  of  potassium  dichromate  and  1  per  cent,  of  sulphuric  acid  and 

1  Mordant  colouring-matters  are  generally  obtained  with  the  following  groups  in  the  ortho-position  :  OH  and 
NO  (or  CO  and  NOH),  2NOH,  2OH.  Also,  according  to  Noelting  (1909),  in  the  anthraquinone  series  intense 
mordant  dyes  are  obtained  also  with  OH  and  NH2  in  the  ortho-position  (less  important  and  less  intense  are  those 
with  OH  and  NHj  in  the  para-position). 


660 


ORGANIC    CHEMISTRY 


amounting  to  15  to  20  times  the  weight  of  the  wool.  After  mordanting,  the  wool  is  rinsed 
well  in  water  and  dyed  in  a  solution  of  the  dyestuff  faintly  acidified  with  acetic  acid  ;  this 
bath  is  heated  very  gradually  to  boiling,  the  latter  being  maintained  for  1  to  2  hours  to 
obtain  the  maximum  intensity  and  fastness.  If  fresh  addition  of  the  colouring-matter 
is  necessary  in  order  to  obtain  the  desired  shade,  it  is  best  first  to  lower  the  temperature 
of  the  bath  to  40°  to  50°with  cold  water  in  order  to  prevent  non-uniformity  of  tint. 

V.  DIPHENYL-     AND     TRIPHENYL  -  METHANE     COLOURING  -  MATTERS, 

P  TT  r1  TT 

CHo^6;;5  and  C6H5—  CH<^6-[T5.     It  has  been  shown  on  p.  647  that  in  these  colouring  - 
^C6.H.5  "^e-H-s 

matters  the  chromophore  consists  of  the  benzene  group  with  two  double  linkings  in  the 
para-position,  R=Cy  /**• 

The  mode  of  formation  and  the  general  properties  of  diphenyl-  and  triphenyl-  methane 
derivatives  were  described  on  pp.  606,  607. 

In  this  group  are  found  Auramine  (basic)  and  Pyronine  (also  basic)  which  dye  wool 
in  an  acid  bath  and  cotton  mordanted  with  tannin. 

The  rosaniline  group  embraces  all  the  basic  colouring-  matters  derived  from  triphenyl- 
methane,  e.g.  malachite  green,  methyl  violet,  for  my  I  violet,  fuchsine,  &c.,  while  with  sulphonic 
and  other  groups,  acid  dyes  are  obtained,  such  as  patent  blue  (carmine  blue),  acid  fuchsine,  &c. 

There  are  also  azo-  derivatives  of  triphenylmethane,  such  as  Rosamine,  which  dyes 
silk  violet-red  with  a  yellow  fluorescence,  and  has  the  formula  : 

C6H3[N(CH3)2] 


CfiHs-C/ 


^C6H3[N(CH3)2C1] 


The  Rosolic  Acid  group,  O= 


>-<fe5&«R>r°H» formed  by fusion  of 


phenol  with  oxalic  acid  in  presence  of  concentrated  H2S04,  also  furnishes  numerous  colouring- 
matters,  e.g.  aurine,  coralline,  pittacal,  chrome  violet. 

Benzoazurin  is  formed  from  1  mol.  of  phenylchloroform  with  2  mols.  of  phenol : 

/  =\  r\  TT    .  Off 

0  :  <  > :  C<Vi6Tj4          5  these  colouring-matters  have  no  practical  application  and 


are  obtained  by  the  condensation  of  phenols  with  phthalic  anhydride  : 

xCOx  /C(C6H4  •  OH)2X 

C6H4<         >0  +  2C6H5-OH  =  H20  +  C6H4<  >0. 

NXK  — -co  — 

Phenolphthalein 

Phthaleins  (see  p.  581)  with  the  hydroxyls  in  the  para-positions  are  of  some  importance  ; 
if  resorcinol,  C6H4(OH)2,  is  used  in  place  of  phenol,  Fluorescein  is  obtained : 

0 


C6H4  •  CO  •  O 

while  if  dimethylaminophenol  is  taken  instead  of  resorcinol,  or  if  fluorescein  chloride  is 
heated  with  a  secondary  amine,  NHR2,  fine  red  colouring-matters,  Rhodamines,  which 
are  basic  in  character,  result : 

O 


R2 :  NCI  = 


— NR2 


QUINONIMIDE    GROUP  661 

If  previously  brominated  phthalic  anhydride  is  used,  the  Eosins  are  obtained  : 

C6H4-C 
| 
CO-^O 


C6HBr2(ONa) 


these  give  beautiful  fluorescent  red  colours  on  silk  but  are  not  very  fast  to  light  (see 
p.  581). 

VI.   COLOURING-MATTERS  OF  THE  QUINONIMIDE  GROUP.     To  this  belong 
the  derivatives  of  indophenol  and  indamine. 


Of  the  hypothetical  quinonimides,  HN=: 


>=0  and  NH= 


>=XH, 


various  derivatives  and  condensation  products  are  known,  e.g.  Indamine, 
H2N/          X>-N=</'        "\=NH; 


Indophenol, OH< 


The    Thiazones,   e.g.    thiodiphenylamine, 


0= 


>=N— < 


>NH,. 


with    indamines     form 


Thiazimes  (e.g.  Lauih's  violet  or  thionine,  meihylene  blue,  methylene  green,  &c.,  which  are 
basic  dyes). 

The  Oxamines  and  Osazones  have  an  oxygen  atom  in  place  of  the  sulphur  of  thiazones, 

/\/°\/\ 

,  and  undergo  various   condensations :    Capri  blue,  naphthol  blue,  Nile 


blue,  &c.,  which  are  also  basic. 

The  Cyanamines  are  related  to  Nile  blue  ;  Resorufin  is  an  osazone,  namely,  hydroxy- 

0=/\/°\/\OH 


diphenosazone, 


;  Gallocyanine,Ci5H1205N2,is  obtained  by  heating 


nitrosodimethylaniline  with  gallic  acid  in  alcoholic  solution.  They  dye  chrome-mordanted 
wool  a  very  fast  violet,  and  are  used  in  printing  linen,  which  is  treated  with  sodium  bisulphite 
and  chromium  acetate  and  subsequently  steamed. 

The   Azines  were   formerly    called    Safranines  ;    the  simplest  type  is  Phenazine, 

C6H4<^  |    j>C6H4.     The  eurodines  are  used  for  dyeing  cotton  mordanted  with  tannin. 

The  Safranines  contain  four  nitrogen  atoms  and  three  aromatic  nuclei : 

,Nv 


NH2 


Cl 


and  are  strongly  basic  and  give  red  colours  on  cotton  mordanted  with  tannin. 

Indulins  are  obtained  by  heating  aniline  hydrochloride  with  aminoazobenzene.    The 
following  constitution  has  recently  been  established  for  one  of  the  indulins : 


662 


ORGANIC    CHEMISTRY 

N-C6H5 


C6H5-HN- 


-NH-C«HS 


N-C6H5 


The  Quinoxalines  contain  the  nucleus 


represented  by  the  formula  : 


.N. 


C— H 


;  the  Fluorindines  can  be 


SHT/ 

H 
X 


C— H 


H 

VII.  ANILINE  BLACK.  The  oxidation  in  various  ways  of  aniline  salts  in  acid 
solution  gives  aniline  black,  which  is  of  considerable  importance  in  the  dyeing  of  cotton. 

Among  the  different  oxidising  agents,  a  special  place  is  occupied  by  vanadium  salts 
(suggested  by  Witz  in  1877),  which  bring  about  the  oxidation  of  large  quantities  of  aniline 
(transferring  oxygen  by  catalytic  action)^;  1  part  of  vanadium,  in  presence  of  a  sufficiency 
of  potassium  chlorate,  oxidises  as  much  as  270,000  parts  of  aniline  hydrochloride.  In 
point  of  efficiency,  vanadium  is  followed  by  caesium  and  then  copper,  the  action  of  iron 
being  much  less. 

Aniline  black  has  a  feebly  acid  character  and  is  insoluble  in  almost  all  solvents.  It 
dissolves  with  difficulty  in  aniline  and  forms  with  it  a  violet  and  then  a  brown  colour  ; 
phenol  dissolves  it  more  easily,  giving  a  green  coloration.  With  fuming  H2S04,  it  yields 
soluble,  coloured  sulpho-compounds.  Acetic  anhydride  gives  a  faintly  coloured  acetyl- 
derivative,  and  potassium  dichromate  a  violet-black  product.  When  treated  with  per- 
manganate and  then  with  oxalic  acid,  aniline  black  is  partially  decolorised.  Energetic 
reducing  agents  (Sn  +  HC1)  decompose  it  completely.1 

1  The  chemical  constitution  of  aniline  black  has  been  the  subject  of  much  discussion.  Assuming  that  the  first 
intermediate  product  of  the  oxidation  of  aniline  is  aniline  black  (Jv  ictzki),  it  cannot  be  true,  as  is  often  thought, 
that  the  transformation  of  aniline  into  quinone  by  oxidation  takes  place  through  the  intermediate  stages  of  phenyl- 
hydroxylamine  and  p-aminophenol,  since  these  do  not  yield  aniline  black  on  oxidation,  phenylhydroxylamine 
giving  a  nitrosobenzene  and  not  a  quinone  ;  nor  can  aminodiphenylamine  (Never,  1907)  be  formed,  since  this, 
on  oxidation,  gives  emeraldine,  a  compound  never  obtained  in  the  oxidation  of  aniline.  It  has  now  been  found 
possible  to  convert  aniline  black  to  the  extent  of  95  per  cent,  into  quinone  by  oxidising  with  lead  peroxide  (chromic 
acid  giving  less  than  80  per  cent.),  so  that  the  indaminic  formula  (proposed  by  Bucherer.  1907)  can  no  longer  be 
attributed  to  aniline  black,  since,  according  to  this,  it  would  give  only  50  per  cent,  of  quinone.  This  result  led 
B.  Willstatter  and  S.  Dorogi  (1909)  to  suggest  for  aniline  black  the  formula  (C6H4N  :  C6HYNH)4,  i.e.  C48Ha,Ns> 
which  is  confirmed  by  the  fact  that  the  oxidation  requires  1J  atom  of  oxygen  per  molecule  of  aniline  with  a  yield 
of  97  per  cent.  Further,  the  determination  of  the  molecular  weight  by  hydrolysis  of  aniline  black  with  dilute 
sulphuric  acid  at  200°  indicates  clearly  the  separation  of  one-eighth  of  the  nitrogen  as  ammonia  : 

C6H4N  :  C6H4  :  NH  +  H20  =  C6H4N  :  CeH4  :  O  +  NH3. 


All  these  results  point  to  the  trebly  quinonoid  formula  of  aniline  black  as  the  most  probable  : 


This  aniline  black  is  obtained  by  oxidising  aniline  in  the  cold  with  rather  less  than  the  theoretical  quantity  of 
dichromate,  chlorate,  or  persulphate.  Further  oxidation  with  H2O2,  for  example,  results  in  the  elimination  of 
•2H  and  the  formation  of  a  quadruply  quinonoid  aniline  black,  C48H34N8,  the  base  of  which  is  very  dark  blue-black 
while  the  salts  are  dark  green.  It  absorbs  only  2JHC1  whilst  the  trebly  quinonoid  black  absorbs  4HC1 ;  all  of 
the  latter  are  displaced  by  ammonia,  which,  however,  in  the  former  case,  leaves  1HC1  (4-5  per  cent,  of  01  in  the 
nucleus).  In  practice  the  quadruply  quinonoid  black  is  obtained  with  excess  of  a  slow  oxidising  agent  acting  in' the 
cold,  e.^.with  chlorate  and  copper  sulphate  or  with  chlorate  and  vanadium.  On  hydrolysis,  the  quadruply  quinonoid 
black  also  loses  one-eighth  of  its  nitrogen  as  ammonia,  forming  the  more  complete  black,  C18HSaON7,  which  is 
not  turned  green  by  SO2.  Oxidation  of  the  corresponding  product  of  hydrolysis  of  the  trebly  quinonoid  black 
gives  the  same  quadruply  quinonoid  black,  C48H3,ON7.  The  practical  preparation  of  aniline  black  in  a  single 
bath  leads  to  the  quadruply  quinonoid  black  that  turns  green,  and  further  oxidation  of  this  in  the  hot  yields  the  black 


QUINOLINE,    THIAZOLE,    ETC.  663 

In  practice  aniline  black  is  produced  directly  on  the  fibre  and  the  use  of  this  very  stable 
colouring-matter  is  due  especially  to  the  studies  and  initiative  of  Prud'homme,  C.  Koecklir, 
Paraf,  &c. 

After  many  improvements,  the  production  of  aniline  black  (termed  also  oxidation 
black  or  fine  black)  directly  on  cotton  fibre  is  now  carried  out  as  follows  (the  quantities 
given  are  for  50  kilos  of  cotton).  The  three  following  solutions  are  prepared  separately  : 

I.  5-5  kilos  of  aniline  oil  (see  p.  558)  +  6-25  kilos  of  commercial  HC1  +  50  litres  of  water  ; 

II.  3-5  kilos  of  sodium  (or  potassium)  chlorate  +  50  litres  of  water  (1-5  kilo  of  starch  is 
sometimes  added)  ;   III.  3  kilos  of  potassium  ferrocyanide  in  20  litres  of  water.     When 
cool,  the  solutions  are  mixed  (1  grm.  of  vanadium  chloride  is  sometimes  introduced)  and 
the  yarn  or  fabric  immersed  until  it  is  well  soaked.     It  is  then  gently  pressed  and  passed 
slowly  over  rollers  through  the  oxidation  chamber  (see  illustration  given  later)  so  that  at 
least  an  hour  elapses  before  it  emerges  at  the  opposite  end.    The  temperature  of  the  chamber 
should  not  exceed  50°  and  the  humidity  25°.     The  fabric  assumes  a  coarse  greenish  colour, 
which  is  changed  to  a  fine  black  when  it  is  transferred  to  a  Jigger  (see  later)  containing 
2  kilos  of  potassium  dichromate,  250  grms.  of  sulphuric  acid  and  100  to  120  litres  of  water 
at  the  temperature  50°.     The  black  thus  obtained,  when  thoroughly  washed,  is  turned 
green  only  to  a  slight  extent  in  the  light. 

VIII.  QUINOLINE  AND  ACRIDINE  COLOURING  -MATTERS.  Among  the 
quinoline  dyestuffs  are  quinoline  yellow  (water-  or  alcohol-soluble),  quinoline  red, 

,CH  :  CH 

cyanine,  &c.  ;  all  of  them  contain  one  or  more  of  the  chromophores,  C6H4\  |     , 

\N    :  CH 
or  its  homologues. 

Acridine   derivatives   possibly   contain   a   quinonoid   chromophore   of    the    formula 
H3(  :  NHk 


—  C6H4— 

They  are  obtained  by  condensing  m-diamines  with  formaldehyde,  heating  the  resulting 
tetraminodiphenylmethane  with  acid  to  remove  ammonia,  and  finally  oxidising  with 
ferric  chloride.  To  this  group  belong  acridine  orange  and  yellow,  phosphine,  benzoflavin,  &c. 

=  C-NX 
IX.  THIAZOLE    COLOURS.      These    contain  the  group  ^C—  with   the 


chromophore  —  C=X  —  and  are  formed  by  heating  p-toluidine  with  sulphur,  the  resulting 
Primulin  being  probably  of  the  constitution 

X*v          /Nv 

CH3-C6H3<       )C-C6H3<       }C-C6H4-NH2: 

xs/  \s/ 

it  may  be  easily  sulphonated,  dyes  cotton  directly  and  may  be  diazotised  and  developed 
on  the  fibre  (see  p.  658).  The  methyl  derivative  is  Thioflavin.  These  colouring-matters 
are  not  very  fast  against  light. 

X.  COLOURING-MATTERS  OF  THE  OXYKETONES,  XANTHONE,  FLAVONE, 
COUMARIN.  This  group  embraces  many  valuable  mordant  colouring-matters  :  alizarin 
yellow,  anthracene  yellow,  alizarin  black  (see  Alizarin  Colouring-Matters,  p.  659),  flavopurpurin, 
alizarin  green,  alizarin  blue,  alizarin  cyanine,  anthracene  blue,  &c.  The  characteristic 

0 


group  of  the  xanthones  is 


,   and  that  of  the  flavones 


— CO— CR 


— 0  — CH 


Indian  yellow  is  a  hydroxy- derivative  of  xanthone. 

XI.  INDIGO,  INDIGOIDS,  AND  OTHER  NATURAL  COLOURING-MATTERS.  In 

addition  to  what  has  been  stated  with  reference  to  indigo  (see  p.  639  et  seq.),  it  may  be  said 
that  there  are  a  number  of  derivatives  of  artificial  indigo  which  are  reduced  with  hydro- 

which  does  not  turn  green,  the  terminal  imino-group  being  hydrolysed.  This  latter  black  is  obtained  also  by  the 
two-  (or  more)  bath  process  or  by  steaming.  Oxidation  of  aminodiphenylamine  instead  of  aniline  gives  first  the 
reddish  blue  imine  (C!4  ..,.),  emeraldine,  which  then  polymeiises,  forming  the  black  (trebly  quinonoid). 


664 


ORGANIC    CHEMISTRY 


sulphite  and  alkali  and  give  very  fast  colours  which  are  superior  to  indigo  and  resist  even 
concentrated  solutions  of  chloride  of  lime.1 

The  Indanthrene  Colours,  which  were  at  first  very  expensive,  are  now  obtainable  at 
more  reasonable  prices  and  give  medium  and  dark  shades.  They  are  so  resistant  to 
various  reagents  that  they  are  used  as  pigments  in  place  of  ultramarine,  &c.  ;  they  are  used 
also  for  blueing  sugar  and  other  foodstuffs,  as  they  are  fast  to  light  and  non-poisonous. 

1  Bohn  has  given  the  name  vat  dyestuffs  to  those  insoluble  pigments  the  molecule  of  which  contains  at  least 
one  ketonic  group  capable  of  being  reduced  (e.g.  by  hydrosulphites),  taking  up  hydrogen  and  thus  becoming  soluble 
in  an  alkaline  liquid  and  flxable  by  animal  and  vegetable  fibres.  These  vat  dyestuffs  may  be  divided  into  two 
classes  :  indigoids  and  indanthrene  derivatives.  The  first  class  comprises  two  series  :  symmetrical  (indigo,  <tc.) 
and  unsymmetrical  (indirubin,  &c.),  and  each  series  contains  various  families  of  the  following  types,  to  all  of  which 
the  chromogen,  — CO — C=C — CO,  is  common. 


(1)  With  nitrogenous  chromogen. 

42  2'  4' 

»_c(K  i    r^JO-JXV 


Naphthindigo 


NXNX 


(2) 


-CO. 


CO  — 


Mixed  symmetrical  with  nitrogen  and  sulphur 
chromogens 


(3) 


>c  =  c 


, 


NX 


— s 


Symmetrical  with  sulphur  chromogen 


(4) 


NH, 


CO 


>NH 


Indigo  and  its  halogenated  and  other  substitution  deriva- 
tives :  chloro-,  bromo-,  alkyl-,  and  naphthol-indigo. 
The  substitution  takes  place  in  the  benzene  nucleus  ; 
many  polybromo-derivatives  are  formed.  The  colours 
range  from  reddish  blue  to  greenish  blue.  The  antique 
purple  recently  studied  by  Friedlander  is  6  :  6'-di- 
bromoindigo.  5-Bromoindigo  (pure  indigo  R),  5  :  5'-di- 
bromoindigo  (pure  indigo  2B),  5:7:  5'-tribromoindigo 
(Ciba  blue  B),  5:7:5':  7'-tetrabromoindigo  (Ciba  blue 
2B  or  indigo  4B)  have  been  prepared. 


CON 


Besides   the  chromophore 


also    the    chromophore  =C< 


>C  =  of  indigo,  these  have 


Belonging    to    this 


family  are  :  Ciba  grey  G  (monobromo-derivatives),  Ciba 
violet  R,  B,  3  R  (these  are  polybromo-derivatives  of  Ciba 
violet  A). 

'The  first  term  is  Friedlander's  thloindiyo  (or  thioindigo 
red  B)  ;  Ciba  bordeaux  B  (5  :  5'-dibronTothioindigo)  and 
numerous  derivatives  in  which  the  5-  and  o'-positions  are 
occupied  by  alkoxy-  and  thioalkyl-groups  have  been 
prepared,  among  these  being  red  and  brown  colours 
and  the  various  colours  of  the  helindone  series  of  Meister 
Lucius  und  Briining. 


Indirubin  is  not  a  colouring-matter,  since  on  reduction  it 
forms  indigo.  But  use  is  made  of  tetrabromoindirubin 
(Ciba  heliotrope  B) : 

XNH<  /—CO  —  v 


C.HjBr 


Indirubin  with  asymmetric  nitrogen  chromogen 


'\ 


>C=C< 


>NH 


CO  - 


C  = 


NX" 


CO 


\ 


\  _ 

Thioindigo  scarlet  B 


I  The  dibromo-derivative  forms  thioindigo  scarlet  G  (or  Ciba 
red  G) : 

Q  C*O 

fi  TT  /          NP  n/  \"\rw 

L«H*N  XU  -  °\    .  X^11 


>Is  known  by  the  name  of  thioindigo  scarlet  2  G  (Ciba  scarlet  G). 


•This  is  a  new  family  which  has  given  the  first  yellow 
colours  of  the  indigoid  group  (Ciba  indigo  yellow  3  <? 
and  Ciba  yellow  G,  which  is  a  dibromo-derivative  of  the 
preceding).  The  group  Ar  is  the  benzoyl  residue,  but 
it  is  not  known  whether  Y  is  H  or  OH,  or  whether  it 
represents  a  double  linking  to  the  nitrogen  atom. 


ANTHRACENE    DYESTUFJFS 

Materials  dyed  with  indanthrene  dyestuffs  do  not  stand  heating  in  an  autoclave,  with 
alkali,  the  colours  being  reduced  and  rendered  soluble.     The  Badische  Anilin-  und  Soda- 

The  second  class  is  that  of  the  anthracene  derivatives,  with  the  following  families  : 

(1) 

Indanthrene  is  formed  by  condensing  2  mols.  of  amino- 
anthraquinone  by  means  of  fused  alkali  and  is  a  dianthra- 
quinonedihydroazine.  With  reducing  agents,  partial 
reduction  of  the  ketonic  group  occurs,  dihydroindan- 
threne  becoming  soluble  in  alkali  and  dyeing  cotton 
directly.  The  halogenated  derivatives  are  of  a  more 
greenish  blue,  resistant  to  oxidising  agents  and  to 
chlorine.  Use  is  made  of  indanthrene  blue  GC,  GCD, 
3  G,  and  3  RC  and  of  algol  blue  and  algol  green.  The 
GCD  blue  is  obtained  by  boiling  indanthrene  with 
aqua  regia.  Anthraflavone  (yellow)  is  similar  to  indan- 
6  v  threne,  but  without  the  NH  groups. 

Indanthrene  blue 


HNl 


NH 


O 

Flavanthrene 


Benzanthrone 


Flavanthrene  (or  indanthrene  yellow  G  and  R)  is  obtained 
by  oxidising  2-aminoanthraquinone  with  antimony 
pentachloride  in  boiling  nitrobenzene  solution.  An 
analogous  compound  which  has  an  orange-yellow 
colour  and  in  which  the  two  nitrogen  atoms  are  replaced 
by  CH,  is  pyranthrene  (or  indanthrene  golden  orange  G), 
the  halogen  derivatives  of  which  tend  to  red  ;  of  these, 
dibromopyranthrene  (or  indanthrene  scarlet  G)  is  used. 


Benzanthrone  is  obtained  by  condensing  anthraquinone 
or  its  derivatives  with  glycerol  in  presence  of  concen- 
trated H8SO4.  Benzanthrone  and  its  halogen  derivatives 
are  not  colouring-matters,  but  by  various  conden- 
sations they  lead  to  excellent  colouring-matters,  such  as 
vwlanthrene,  the  dibromo-derivative  of  which  is  indan- 
threne green  B ;  isoviolanthrene  (which  has  a  similar 
constitution  to  pyranthrene)  and  its  dichloro-derivative 
(indanthrene  violet  RR  extra). 


Anthraquinonimide  derivatives 


<5)  Aciaminoanthraquinone  derivatives 
O  O 


-NH-CO-NH 


\/\/\/ 

O  O 

Helindone  yellow  SON 


Various  types  :  Rufanthrene,  leucol,  cibanones, 
hydrones,  indigolignoids 


{Indanthrene  bordeaux  and  indanthrene  red  G  and  R  are 
formed  from  3  mols.  of  anthraquinone  joined  in  various 
ways  by  two  imino-groups.  Algol  red,  which  was  the  first 
red  vat  dyestuff  of  the  anthraquinone  series,  consists  of  2 
mols.  of  anthraquinone  united  by  an  NH  group,  one  of 
them  being  condensed  with  a  pyridone  ring. 


Characteristic  of  these  is  the  complex  of  several  NH 
groups  united  once  or  more  times  to  CO  groups.  Helin- 
done yellow  3  G  represents  two  anthraquinone  groups 
condensed  with  urea.  Various  other  condensations  of 
aminoanthraquinones  with  benzoyl,  succinic,  tartaiic, 
phthalic,  &c.,  groups  give  algol  reds  G,  R,  and  5  G,  &c. 

These  colouring-matters  are  obtained  by  fusing  aminoan- 
thraquinones with  sulphur  or  alkaline  sulphides'  ruf- 
anthrene  browns,  greys,  olives),  indanthrene  brown, 
cibanone  brown,  cibanone  yellow ;  the  first  cibanone 
black  was  obtained  from  methylbenzanthrene,  and  the 
leucol  colours  of  the  firm  of  Bayer  are  also  of  this  group. 
A  mixed  indigoid-anthracene  group  has  recently  been 
obtained.  Thus,  the  action  of  isatin  chloride,  &c., 
on  a-naphthol  (or  its  ortho-derivatives)  gives  the  indigoid 
colouring-matter  and  an  isomeride  of  analogous  pro- 
perties, e.g.  indonaphthalene  or  indolignone  (Friedlander 
and  Bezdzich,  1909) ;  both  the  indigoid  and  the  indo- 
lignone are  decomposed  by  alkali  into  anthranilic  acid 
and  the  corresponding  hydroxynaphthaldehyde.  A 
group  of  sulphur  vat  dyestuffs  is  that  of  the  indrone 
blues  (Cassella),  derived  from  carbazole,  which  with 
p-nitrosophenol  gives  a  base, 


)OH, 

and  this,  when  fused  with  sulphur  or  sulphides   forms 
reducible  colouring-matters  soluble  in  alksli. 


666 


ORGANIC    CHEMISTRY 


Fabrik  recommend  the  addition  of  an  oxidising  agent  to  the  autoclave  bath  to  prevent  the 
reduction. 

The  principal  natural  mordant  colouring-matters  are :  logwood,  brazilein,  archil, 
cochineal,  catechu,  sandalwood,  &c.  ;  and  the  natural  substantive  dyes  for  cotton  and 
wool  are  :  bixin,  curcumin,  carthamin,  &c. 

These  dyewoods  are  placed  on  the  market  in  small  trunks  or  in  chips  ;  for  economy 
in  transport  and  convenience  in  use,  dense  aqueous  or  concentrated  dry  extracts  are  often 
prepared.  Italy  imported  the  following  quantities  : 


1906 

1907 

1908 

1909 

1910 

quintals 

quintals 

quintals 

quintals 

quintals 

Woods   for    dyeing    and 

tanning 

223,762 

273,272 

219,985 

275,300 

266,400     (£140,000) 

Dye  extracts 

7,883 

7,540 

5,573 

6,699 

6,412     (£23,080) 

Catechu  and  gambier 

5,603 

4,025 

3,998 

4,587 

5,806     (£13,935) 

Germany's  imports  and  exports  were  as  follow : 


IMPORTS 

EXPORTS 

, 

1908 

1909 

1908 

1909 

quintals 

quintals 

quintals 

quintals 

Logwood      .... 

111,165 

94,489 

14,046 

8,563 

Yellow  wood         .    .     . 

7,697 

9,424 

1,372 

1,016 

Bed  wood             . 

7,245 

11,266 

2,030 

812 

Catechu       .... 

33,852 

35,438 

2,426 

2,425 

LOGWOOD  or  Campeachy  is  obtained  from  the  barked  trunk  of  a  tree  (Hcematoxylon 
campechianum  ;  Fig.  423  shows  twig,  leaves,  flowers,  and  seeds)  which  grows  in  Central 
America  and  in  the  Antilles,  the  best  qualities  being  those  of  Honduras,  San  Domingo, 
and  Jamaica.  Just  as  the  consumption  of  indigo  has  not  diminished  in  spite  of  the  com- 
petition of  the  numerous  artificial  aniline  and  alizarin  colours,  so  also  the  use  of  logwood 
in  dyeing  tends  to  increase,  although  not  in  similar  proportion  to  that  of  the  artificial 
dyes.  The  wood  arrives  in  Europe  in  logs  weighing  150  to  200  kilos,  which  are  sawn  into 
short  pieces,  chopped  and  reduced  to  chips  or  raspings  ;  more  rarely  they  are  ground. 

The  colouring- matter  of  logwood  was  studied  by  Chevreul  in  1810,  by  Erdmann  in 
1842,  and  by  Hess  and  Reim  in  1871.  It  consists  of  a  glucoside  which  occurs  in  the  fresh 
wood  and  which,  perhaps  by  simple  fermentation  or  by  the  action  of  water  and  air,  separates 
the  base  of  the  colouring-matter,  i.e.  Haematoxylin,  C16H90(OH)5,  and  this,  under  the 
influence  of  atmospheric  oxygen  (best  in  presence  of  alkali),  gives  the  colouring- matter 
hcematein  (which  dyes  with  metallic  oxides),  C^H^Oe,  2H  being  thus  lost.  Haematein 
is  moderately  soluble  in  water,  alcohol,  ether,  or  glacial  acetic  acid,  and  insoluble  in  chloro- 
form or  benzene.  In  ammoniacal  solution  it  assumes  a  purple-red  colour,  which  becomes 
brown  in  the  air.  By  reducing  agents  (H2S,  S02,  Zn  +  HC1,  &c.)  hsematein  is  decolorised 
without,  however,  giving  hsematoxylin. 

Hsematoxylin  is  probably  3:4:3':  4'-Tetrahydroxyrufenol  : 


C-OH 
CH 

CH2-C6H3(OH)2(3  :  4), 


LOGWOOD,    ARCHIL 


66T 


and  haematein  would  have  a  quinonoid  formation  in  place  of  the  hydroxyl  of  the 
first  nucleus,  H  being  lost  together  with  another  H  from  the  para-CH  of  the  second 
nucleus. 

In  dyeing,  logwood  is  used  in  chips  or  as  an  extract.  The  chips  are  first  matured 
(?  fermented)  by  moistening  with  water,  heaping  up  and  stirring  every  two  or  three  days 
for  one  or  two  weeks,  care  being  taken  to  prevent  heating  of  the  mass,  which  would  destroy 
the  colouring- matter.  The  wood  changes  from  a  yellowish  to  a  brownish  red  colour  and 
is  extracted  with  boiling  water,  to  which  it  gives  up  2-5  to  3  per  cent,  of  its  weight  ;  the 
solution,  which  is  rich  in  haematein,  is  used  as  it  is  in  the  dye-vat.  Logwood  extracts 
are  prepared  by  boiling  the  non-fermented  wood  with  water  in  open  boilers  or  in  autoclaves 
and  concentrating  the  solution  in  vacua  to  30° 
Be.  ;  these  extracts  are  very  rich  in  hsema- 
toxylin. 

Haematein  is  a  mordant  colouring-matter,  i.e. 
is  fixed  and  gives  intense  and  fast  colours  only  on 
mordanted  fibres,  and  is  generally  used  for  black 
or  blue-black  shades  with  various  shot  effects, 
according  to  the  nature  of  the  mordant :  with 
aluminium  salts  it  gives  a  greyish  violet-black, 
with  chromium  salts  blue-black,  with  iron  salts 
grey-black,  with  copper  salts  greenish  blue-black, 
and  with  tin  salts  violet- black. 

A  fine  black  is  usually  obtained  by  mordant- 
ing, e.g.  wool,  for  2  hours  in  a  boiling  bath  con- 
taining 2  to  3  per  cent,  of  potassium  dichromate, 
3  to  4  per  cent,  of  tartar  (or  2  per  cent,  sulphuric 
acid,  3  per  cent,  lactic  acid,  &c.)  and  0-5  to  1  per 
cent,  of  copper  sulphate  (all  calculated  on  the 
weight  of  fabric).  The  mordanted  fabric  is  well 
washed  and  dyed  in  a  boiling  aqueous  bath,  to 
which  is  added  the  dilute  logwood  extract  or  5  to 
8  per  cent,  of  the  concentrated  extract  or  the 
matured  chips  in  bags.  To  obtain  black-black 
(coal-black  without  blue  reflection),  0-2  to  0-5  to 
1  per  cent,  of  Cuba  yellow  wood  extract  is  added. 
Dyeing  is  followed  by  thorough  washing  in  cold 
water. 

Cotton  is  first  mordanted  in  the  usual  way  in 
a  tannin  bath  (2°  to  3°  Be.  overnight),  then 

passed  into  an  iron  nitrate  bath  (see  Dyeing  of  Silk,  and  note  on  p.  651),  rinsed  and  dyed 
in  the  hot  aqueous  bath  with  logwood  and  yellow  wood.  After  dyeing  the  brqnze-red 
appearance  is  removed  by  a  soap  bath. 

For  dyeing  silk  black,  see  later. 

Logwood  extracts  are  often  adulterated  with  chestnut-bark  extract,  molasses,  dextrin, 
sumac,  &c.,  and  as  a  rule  the  best  test  consists  in  dyeing  equal  weights  of  mordanted 
fabric  with  equal  weights  of  the  suspected  and  a  pure  extract.  Sugar  (molasses)  or  dextrin 
maj-  be  detected  by  precipitating  with  a  slight  excess  of  lead  acetate  and  examining  the 
filtrate  by  means  of  either  Fehling's  solution  or  the  polarimeter. 

Chestnut- bark  extract  is  detected  by  treating  1  grin,  of  the  extract,  dried  at  100°, 
with  ether  and  weighing  the  portion  dissolved  by  the  ether.  The  residue  is  then  extracted 
with  absolute  alcohol  and  the  amount  dissolved  determined.  A  good,  dried  extract 
contains  86  to  88  per  cent,  of  matter  soluble  in  ether  and  12  to  14  per  cent,  soluble  in  alcohol, 
while,  if  chestnut-bark  extract  is  present,  less  dissolves  in  ether  and  more  in  alcohol. 

Statistics.     See  above. 

ARCHIL  is  extracted  from  Roccella  tinctoria  (2  to  12  per  cent.)  or  from  other  lichens 
growing  on  the  coast  or  on  bare  rocks  in  mountainous  districts.  The  red  colouring-matter  is 
formed  after  fermentation  in  presence  of  a  little  ammonia,  and  after  the  action  of  atmospheric 
oxygen.  Prior  to  fermentation,  the  colourless  compounds  contain  roccellic  acid  (p.  305) 
and  erythric  acid,  while,  after  the  decomposition,  orcin  (see  p.  544)  is  present ;  the  latter, 


FIG  423. 


668  ORGANIC    CHEMISTRY 

when  oxidised  in  presence  of  NH3,  gives  orceine  (see  p.  544),  which  forms  violet-red  lakes. 
Archil  is  placed  on  the  market  as  extract  or  solid  preparation. 

Cudbear  (or  perseo)  is  obtained  from  Lecanora  tartar ea  and  dyes  wool  and  silk  very 
uniformly  in  presence  of  alum,  tin  salt,  and  tartaric  acid. 

Litmus  (or  tournesol)  is  formed  from  orcin  by  the  action  of  ammonia  or  soda,  and  is 
obtained  from  various  lichens  (Roccella  tinctoria).  The  extract  is  mixed  with  gypsum  or 
chalk  and  made  into  tablets,  which  contain  also  various  colouring-matters  (azolitmin, 
erythrolein,  erythrolitmin,  spaniolitmin).  It  is  very  sensitive  to  acids,  which  redden  it, 
and  to  alkalis,  which  turn  it  blue,  and  hence  serves  as  an  excellent  indicator. 

COCHINEAL  has  been  long  used  as  a  colouring-matter  and  is  the  female  of  the  insect 
Coccus  cacti,  which  lives  on  the  cactus  of  the  Canary  Islands,  Algeria,  Java,  Guatemala, 
&c.  When  the  insect  is  three  months  old  (weight  =  0-0065  grms.)  it  is  killed  with  hot  water, 
(black  grain)  or  in  an  oven  (silver  grain).  The  colouring-matter  is  Carminic  Acid,C17H16010. 
The  dry  insects  are  powdered  and  extracted  several  times  with  boiling  water,  the  dye-bath 
being  prepared  with  hot  water,  3  per  cent,  of  oxalic  acid  and  1-5  per  cent,  of  tin  salt ;  the 
wool  is  immersed  in  this  for  at  least  30  minutes  at  a  boiling  temperature.  The  wool  may 
be  first  mordanted  separately  with  oxalic  acid  and  tin  salt  and  then  dyed  in  the  aqueous 
cochineal.  Italy  imported  47  quintals  of  cochineal  and  kermes  in  1906  ;  24  in  1908,  and 
33  (£330)  in  1910. 

YELLOW  WOOD  or  Cuba  Wood  (Old  fustic)  is  obtained  from  the  trunks  of  Morus 
tinctoria  or_of  Madura  tinctoria  of  the  West  Indies,  Brazil,  and  Mexico,  the  best  kinds 
being,  however,  those  of  Cuba,  Tampico,  Porto  Rico,  and  Jamaica.  The  colour  may  be 
extracted  from  the  wood  by  means  of  steam,  and  the  concentrated  extract  contains  a  tanning 
material  (maclurin),  since  a  brighter  yellow  is  obtained  on  dyeing  if  a  little  gelatine  is  added 
to  precipitate  this  tanning  substance  ;  if  this  is  not  done,  prolonged  boiling  gives  dark  or 
brownish  shades.  Although  Cuba  yellow  dyes  pure  fibres  directly,  really  fast  colours  are 
obtained  only  by  chrome  mordanting,  &c.  ;  hence  Cuba  yellow  is  used  together  with 
logwood  or  even  alizarin  or  anthracene  colouring-matters. 

Statistics.     See  above. 

QUERCITRON  is  sold  in  small  chips  or,  better,  as  a  coarse  powder  obtained  by  grinding 
the  bark — freed  from  epidermis — of  Quercus  tinctoria  and  Q.  nigra,  which  grow  in  Penn- 
sylvania, Carolina,  Scotland,  France,  and  the  South  of  Germany. 

The  dilute  aqueous  extract  does  not  keep,  and  must  hence  be  used  immediately. 
Chevreul  separated  from  the  bark  the  compound  Quercitrin,  C2iH22On  +2H20,  which  when 
boiled  with  acid  takes  up  1  mol.  H20,  giving  Quercetin,C15H1007,and  Isodulcitol,C6H1406. 
Quercetin  is  1  :  3  :  3' :  4'-Tetrahydroxyflavanol) 

OH  CO 


HO 


>OH; 


0  OH 


it  dissolves  in  alkali,  giving  an  orange-yellow  coloration  and  yields  phloroglucinol  and 
protocatechuic  acid  when  fused  with  alkali.  It  is  sulphonated  by  concentrated  sulphuric 
acid,  forming  a  direct  dye  for  wool. 

It  dyes  more  especially  animal  fibres  (wool)  either  previously  mordanted  or  with  an 
alum  or  chrome  mordant  added  to  the  dye-bath.  Similar  behaviour  is  shown  by  flavin, 
which  is  a  more  concentrated  preparation  of  quercitron  and  contains  quercetrin  and 
quercetin. 

Natural  INDIAN  YELLOW  is  still  extracted  in  Bengal  from  the  evaporated  residue 
of  the  urine  of  cows  fed  on  mango  leaves.  It  contains  a  hydroxyl  derivative  of  xanthone, 
namely,  Euxanthone,  as  glycoronic  ester  (euxanthinic  acid,  C^H^O.^),  which  is  decomposed 


by  hot  hydrochloric  acid  into  Euxanthine,  C13H804  or 


HQ/   N— CO— 


—  O  — 


OH 


(obtained 


synthetically  by  condensing  hydroquinonecarboxylic  acid  with  /3-resorcylic  acid). 

Natural  Indian  yellow  functions  as  a  mordant  dyestuff,  but  is  now  scarcely  used  for 
textiles  as  it  is  not  very  stable  to  light. 


CHLOROPHYLL  669 

BRAZIL  WOOD  or  Red  Wood  is  obtained  from  the  trunk  of  Ccesalpina  brasiliensis 
and  other  varieties.  The  colourless  glucoside  it  contains  gives,  on  fermentation  or  when 
treated  with  acids,  glucose  and  Brazilin,  Cl6R1^O5or  C6H3(OH)2-C4H40-C6H5O2,  which 
is  coloured  carmine  by  alkali  and  decolorised  by  acids  or  reducing  agents  ;  it  gives  intensely 
coloured  lakes  and  oxidises  in  the  air,  forming  Brazilein,C16H1205,  while  with  concentrated 
nitric  acid  it  gives  trinitroresorcinol  and,  when  fused  with  alkali,  resorcinol.  It  is  a  red 
mordant  (alum  or  chrome)  colouring- matter,  but  is  only  slightly  fast  to  light. 

Brazilin  seems  to  have  a  constitution  analogous  to  that  of  haematoxylin  (see  p.  666) 
with  a  hydroxyl  group  less  in  the  first  benzene  nucleus,  brazilein  being  apparently  the 
corresponding  quinonoid  derivative  similar  to  haematein  (see  above). 

SANDAL  WOOD  is  the  wood  of  Pterocarpus  santalinus,  which  grows  in  Madagascar,, 
tropical  Asia,  and  Ceylon.  Santalin  or  Santalic  Acid,  C^Hj  606,  which  forms  the  colouring- 
matter  of  this  wood,  occurs  in  abundance  in  other  plants  (in  barwood  or  Baphia  nitida  of 
Sierra  Leone  and  in  camwood  or  kambewood  from  West  Africa). 

Santalin  gives  resorcinol,  acetic  acid,  &c.,  when  fused  with  alkali,  but  its  constitution 
is  not  yet  established.  It  is  a  mordant  colouring-matter,  like  logwood,  and  was  once  used 
with  alizarin  to  dye  cotton  red. 

CATECHU  (or  Cutch)  and  GAMBIER  are  extracted  from  various  plants  of  India, 
Bengal,  Malay,  &c.  (palm,  mimosa,  Rubiaceae,  Acacia  catechu,  Areca  catechu,  Uncaria 
gambier,  &c.).  They  contain  tannin  and  colourless  catechol,  partly  combined  to  a  brown 
colouring- matter.  When  fused  with  alkali,  they  give  phloroglucinol,  pyrocatechol,  and 
protocatechuic  acid.  With  various  mordants  they  give  stable  browns  or  olives,  which 
do  not,  however,  withstand  chlorine  or  alkali.  On  cotton  they  give  reddish  or  yellowish 
brown  colours  which  become  fast  to  light  after  treatment  with  a-lkali  dichromate  at  60° 
to  70°  (khaki  used  for  uniforms  in  the  British,  German,  and  Italian  armies). 

Nowadays  a  much  faster  khaki  is  obtained  by  impregnating  the  white  fabric  in  a  cold 
concentrated  bath  of  pyrolignite  of  iron,  chromium  acetate,  and  a  very  small  proportion 
of  manganese  chloride,  drying  it  thoroughly,  immersing  it  in  a  boiling  bath  of  caustic 
soda  (11°  Be.)  and  a  little  sulphoricinate,  and  oxidising  in  a  hot-air  chamber  or  by  means 
of  dichromate  solution.  With  a  less  concentrated  soda  bath  or  one  not  boiling,  the  metallic 
oxides  would  be  precipitated  superficially  on  the  fibre,  and  the  dry  fabric  would  be  dustv 
and  would  wear  out  sewing  needles. 

This  khaki  is  very  fast  against  light,  scouring,  and  chlorine,  but  does  not  resist  perspira- 
tion (test  with  a  mixture  at  1°  Be.  of  hydrochloric,  formic,  and  acetic  acids  for  5  hours). 
Fastness  to  perspiration  is  given  by  boiling  the  dyed  fabric  for  2  hours  in  a  silicate  bath  at 
6°  to  7°  Be. 

Statistics.     See  above. 

CHLOROPHYLL  is  not  a  colouring- matter  for  textiles  but  is  the  green  pigment 
which  occurs  in  many  plants  (those  which  assimilate  C02)  and  brings  about  the  transforma- 
tion of  the  carbon  dioxide  into  starch  in  the  leaves  under  the  action  of  sunlight — especially 
of  certain  rays  of  the  spectrum — and  apparently  also  with  the  help  of  an  enzyme  (Will- 
statter and  Stoll,  1911)  known  as  Chlorophyllase.  With  starch,  wax,  &c.,  it  forms  the 
characteristic  chlorophyll  granules  of  green  leaves. 

It  is  soluble  in  oil,  alcohol,  ether,  or  chloroform,  its  solutions  showing  blood-red 
fluorescence  and  readily  undergoing  change.  Its  constitution  is  still  uncertain,  and  it 
does  not  appear  to  contain  combined  iron  as  was  formerly  thought.  Following  the 
indications  of  the  botanists  Borodin  (1882)  and  Monte verde  (1893),  Willstatter  and 
Benz  (1908)  obtained  a  pure  chlorophyll1  (2  grms.  from  1  kilo  of  dried  leaves)  in  dark, 
bluish  black  crystals  with  a  metallic  lustre,  which  are  insoluble  in  petroleum  ether 
but  soluble  in  alcohol  or  ether,  giving  a  bluish  fluorescence.  The  green  solution  of  this 
product,  which  exhibits  the  same  spectrum  as  the  chlorophyll  of  fresh  leaves,  is  turned 
brown  by  alkali,  but  again  becomes  green.  Its  formula  is  probably  C55H72O6N4Mg,  and 
the  magnesium  present  (3  per  cent.)  is  perhaps  the  cause  of  the  catalytic  action  effecting  the 
transformation  of  CO2  into  starch  ;  it  does  not  contain  phosphorus,  as  many,  including 

1  As  chlorophyll  readily  undergoes  change,  it  is  extracted  in  the  cold  with  methyl  alcohol  from  the  carefully 
dried,  powdered  leaves  (Willstatter),  previously  washed  with  petroleum  ether.  In  order  to  separate  it  from 
other  colouring  impurities,  its  alcoholic  extract  is  suitably  diluted  and  extracted  with  ether  (benzene  or  carbon 
disulphide),  many  of  the  impurities  remaining  dissolved  in  the  alcohol ;  or  the  alcoholic  extract  may  be  shaken 
with  a  large  amount  of  water,  which  dissolves  the  chlorophyll  in  the  colloidal  state,  the  decanted  aqueous  solution 
being  treated  with  salt  and  extracted  with  petroleum  ether  containing  a  little  alcohol.  From  this  solution  the- 
chlorophyll  is  deposited  pure  if  the  whole  of  the  alcohol  is  eliminated  by  washing, 


670  ORGANICCHEMJSTRY 

Stoklasa,  have  thought.  Acids  remove  all  the  magnesium,  the  residue  being  Phoeophytin, 
which  is  similar  to  chlorophyll,  is  ethereal  in  character,  and  forms  various  products  (e.g. 
phytol,  phytochlorin,  and  phytorodin)  when  hydrolysed  with  alkali.  Phytol  forms  one- 
third  by  weight  of  the  chlorophyll  of  plants  and  is  a  primary,  unsaturated,  monohydric 
alcohol,  C20H400.  Plants  produce  also  an  amorphous  chlorophyll  which,  unlike  the  other, 
gives  phytol  on  hydrolysis.  It  is  thought  that  it  is  analogous  in  chemical  composition 
to  the  colouring-matter  of  the  blood  (see  later),  since  both  yield  pyrrole  when  distilled  with 
zinc  dust.  Willstatter  and  Isler  (1911)  showed  that  chlorophyll  contains  two  colouring- 
matters  :  (a)  bluish  green  and  (b)  yellowish  green,  thus  confirming  the  hypotheses  of 
Stokes  (1867  and  1873)  and  of  Tswett  (1906)  ;  the  two  colours  are  separated  by  more  or 
less  dilute  alcohol.  Chlorophyll  is  used  in  practice  to  colour  oils,  soaps,  fats,  preserved 
vegetables,  &c.  ;  it  costs  8s.  per  kilo  or,  for  the  highly  purified  product,  80s.  per  kilo. 

XII.  SULPHUR  COLOURING-MATTERS.  These  colouring- matters,  which  have 
been  discovered  since  1893,  are  very  fast  on  cotton,  which  they  dye  directly  without  a 
mordant,  but  in  alkaline  and  reducing  solution  (sodium  sulphide  and  sometimes,  a  little 
glucose)  which  prevents  any  unevenness  which  might  be  produced  in  the  colouring  owing 
to  contact  with  the  air.  The  sulphur  colouring-matters  do  not  dye  wool  or  silk  in  presence 
of  sodium  silicate  (or  of  blood  or  diastofor),  so  that  two  colours  can  be  obtained  on  wool 
and  cotton  fabrics,  the  wool  being  dyed  first  with  an  acid  dyestuff  and  the  cotton  subse 
quently  with  a  sulphur  colouring-matter  in  a  bath  of  sodium  sulphide  and  silicate  (or 
blood  or  diastofor). 

They  are  obtained  by  melting  together  sulphur  or  sodium  sulphide  and  various  other 
colouring-matters  or  other  organic  compounds.  Cachou  de  Laval  has  been  known  since 
1873  but  has  been  used  but  little  It  was  obtained  by  Croissant  and  Bretonniere  by  fusing 
sawdust,  bran,  or  the  like  with  sodium  sulphide.  In  1893  the  discovery  of  Vidal  black 
turned  the  attention  of  manufacturers  to  this  interesting  group  of  colouring-matters,  which 
now  include  almost  all  tints  except  red,  and  are  obtained  by  fusing  with  sulphur  or  sodium 
sulphide,  derivatives  of  benzene,  naphthalene,  diphenylamine,  anthraquinone,  &c.  These 
colouring- matters  are  placed  on  the  market  by  various  firms  under  different  names,  although 
their  compositions  are  practically  the  same :  the  firm  of  Cassella  calls  them  immedial 
colours  ;  the  Bayer  Company,  katigenic  colours  ;  the  Badische  Company,  kriogenic  colours ; 
the  Berlin  Aktien-Gesellschaft,  sulphur  colouring-matters,  &c.  The  constitution  of  these 
colours  has  not  been  firmly  established,  but  during  recent  years  a  little  light  has  been 
thrown  on  them.  According  to  Sandmeyer  (1901)  they  are  derivatives  of  Piazthiol, 

N, 

/S,    the     compound   soluble    in    sodium    sulphide    having    the    constitution 
W 

\ 
R 

Nv  xNa 

/S  =  S\        ;   but  nowadays  other  interpretations  have  been  given. 
N/  XNa 

I 
R 

When  diphenylamine-derivatives  are  fused  with  Xa2S,  black  colouring  matters  are 
preferably  formed,  with  aminohydroxydiphenytamine  derivatives  and  the  corresponding 
N-alkyl  and  N-aryl  compounds  blue  colours  are  obtained,  while  in  presence  of  stable 
metasubstituted  compounds,  brown  or  yellow  colouring-matters  are  formed. 

In  general  the  reaction  takes  place  with  preliminary  formation  of  aromatic  mercaptans 
or  polymercaptans  (in  the  ortho-position  with  respect  to  N  or  to  0),  which  give  further 
condensation  products,  e.g.  black  derivatives  of  thiodiphenylamine  (of  thiazine), 


/  \   /  '  x    ^" 

,s/  \/ 

and  yellow  or  brown  colouring-matters  derived  from  thiazole  (see  above), 


TESTING    OF    DYESTUFFS 


671 


They  form  insoluble  condensed  products  (disulphides)  with  the  oxygen  of  the  air,  these 
being  rendered  soluble  again  by  alkaline  reducing  agents  (sodium  sulphide,  hydrosulphites, 
&c.).  The  fixation  and  development  of  the  colour  in  the  cotton  fibres  consist  simply  in  the 
oxidation  of  the  mercaptan  to  disulphide.  The  black  or  blue  sulphur  colouring-matters  are 
quinonimino-derivatives  of  the  thiazine  group.  These  colouring-matters  are  now  used  in 
large  quantities,  the  production  of  sulphur  black  alone  in  1909  being  estimated  at  nearly 
5,000,000  kilos.  It  has  been  proposed  (1909)  to  render  them  faster  to  washing  by  treatment 
with  formaldehyde  or  by  immersion  in  a  nickel  sulphate  bath. 


TESTING  OF  COLOURING-MATTERS 

Of  the  thousands  of  colouring-matters  sold  by  different  firms  under  most  varied  and 
fanciful  names,  the  majority  represent,  not  chemical  individuals,  but  intimate  mixtures 
of  several  colours  which  give  directly  the  tints  desired. 

The  colouring- matters  obtained  at  the  end  of  the  manufacture  by  precipitation  or 
separation  from  their  solutions  by  means  of  salt  (just  as  with  soap)  are  not  sold  in  the  pure 
state,  but  are  diluted  with  50  per  cent,  or  75  per  cent,  of  finely  ground  sodium  chloride  or 
sulphate.  A  mixture  may  be  distinguished  from  a  chemical  individual  by  the  following 
simple  test :  a  few  milligrams  are  blown  in  a  cloud  from  a  watch-glass  and  are  caught 
on  a  moist  filter-paper  spread  on  a  sheet  of  glass  at  a  short  distance  from  the  watch-glass. 
If  the  filter-paper  were  not  too  moist,  it  shows  on  drying  isolated,  swollen  points  of  colour, 
the  uniformity  or  non-uniformity  of  which  is  readily  seen.  A  variation  of  this  test  consists 
in  sprinkling  a  little  of  the  powder  on  to  the  surface  of  concentrated  sulphuric  acid  contained 
in  a  flat  porcelain  capsule. 

The  use  of  the  spectroscope  has  been  suggested  for  differentiating  between  various 
groups  of  colouring- matters,  the  positions  of  the  absorption  bands  being  observed  when 
white  light  is  passed  through  an  aqueous  or  alcoholic  solution  of  the  colouring-matter  of 
definite  concentration  contained  in  a  glass  vessel  with  parallel  glass  walls.  The  spectroscope 
is  now,  however,  scarcely  ever  used,  owing  to  the  uncertainty  of  the  results  obtained  ;  but 
it  is  useful  in  detecting  the  colouring-matter  of  the  blood  (see  later  Haemoglobin). 

The  qualitative  analysis  of  colouring- matters  for  the  detection  of  the  principal  groups 
may  be  carried  out  according  to  the  method  of  A.  G.  Rota  L  or  to  those  of  Weingartner 
and  Green.  The  latter,  which  are  largely  used,  are  briefly  as  follow  : 

I.  COLOURING-MATTERS  SOLUBLE  IN  WATER.  (A)  If  the  aqueous  solution 
gives  a  precipitate  with  a  solution  containing  10  per  cent,  of  tannin  and  10  per  cent,  of 
sodium  acetate,  the  presence  of  basic  colour  ing -matters  is  denoted : 

(1)  If  the  solution  of  the  colouring-matter  is  reduced  with  zinc  dust  and  dilute  hydro- 
chloric acid,  a  few  drops  of  the  decolorised  solution  are  placed  on  a  piece  of  filter-paper  : 

(la)  The  reappearance  of  the  original  colour  of  the  substance  when  the  paper  is  waved 

1  Rota's  method,  extended  by  Buzzi  (1911),  for  analysing  colouring-matters  consists  of  four  series  of  tests  : 

A.  This  is  based  on  the  usually  quinonoid  character  of  these  matters  and  hence  on  their  behaviour  towards 
acid  reducing  agents,  preferably  stannous  chloride ;  the  alkaline  reducing  agents  do  not  serve  well,  as  with  all 
colouring-matters  they  give  leuco-derivatives  which  are  not  very  characteristic. 

The  behaviour  with  SnCla  +  HC1  permits  of  the  division  of  all  colouring-matters  into  the  following  four 
groups  : 

I.  Those  which  are  decomposed  may  contain  the  following  chromogens  (p.  647) : 


OH 


=  N-OH 


>NH—  X=( 


,  &c. 


\ / 


II.  Those  which  are  reduced  to  colourless  leuco-compounds,  which  can  be  reoxidlsed,  contain  the  chromogen 
(P.  647) : 

N  N  N 


H,N 


NH,-C1 


(orO) 


672 

in  the  air  indicates  azines,  oxazines,  thiazines,  and  acridines,  i.e.  according  to  the  colour, 
pyronine,  safranine,  rosinduline,  phosphine,  benzoflavin,  indulin,  &c. 

(16)  If  the  original  colour  appears  but  weakly  or  not  at  all,  but  is  formed  immediately 
on  moistening  with  a  drop  of  1  per  cent,  chromic  acid  solution,  the  colouring-matter  belongs 
to  the  rhodamines  or  to  the  triphenylmethane  group  ; 

(Ic)  The  non-appearance  of  the  original  colour  under  any  conditions  indicates  auramine, 
thioflavin,  chrysoidin,  Janos  colours,  Bismarck  brown. 

III.  Colouring-matters  which  are  neither  reduced  nor  decomposed,  but  have  a  basic  character  and  arc  partly 
decolorised  or  precipitated  by  caustic  soda,  contain  the  chromogens  (p.  647) : 


H,N 


/\ 


NH2-C1  (or  =  O) 


\/\/\/ 
C 


H,N 


NH, 


IV.  Those  which  are  neither  reduced  nor  decomposed,  andjhave  a  phenolic  character  (feebly  acid)  and  are 
increased  in  colour  and  solubility  by  caustic  soda,  contain  the  chromogens  : 


T 

OH 


\_/ 


=0i 


OH 


Groups  III  and  IV  always  contain  the  chromophore 


OH 


OH 


and  to  these  belong  the  acridines,  the  thiazoles, 


theauramines,  the  rosanilines,  the  pyronines,  the  rosamines,  the  phthaleins,  the  rhodamines,  the  hydroxyacetones, 
the  hydroxyanthraquinones,  the  coumarins,  flavone,  flavonal,  &c. 

B.  To  distinguish  between  the  different  chromogens  of  the  separate  groups,  other  special  reactions  are  used, 
for  instance  : 

The  acridines,  with  concentrated  sulphuric  acid,  give  a  fluorescence  resembling  that  of  petroleum. 
The  «0o-dyestuffs,  with  concentrated  nitric  acid,  regenerate  the  respective  diazo-salts. 
The  hydroxyacetonic,  hydroxyquinonic,  &c.,  colouring-matters  are  precipitated  as  lakes  by  stannous  chloride 
and  subsequent  treatment  with  sodium  acetate. 

The  transformation  of  azo-  colouring-matters  and  their  derivatives  into  thiazole  (polychromin). 

The  conversion,  by  special  reagents,  of  one  colouring-matter  into  another,  e.g.  gallein  into  ccarulein. 

C.  After  the  restriction  of  the  colouring-matter  to  one  of  the  four  groups,  and  after  the  various  tests  for  defining 
more  exactly  the  character  of  the  chromophore  have  been  carried  out,  the  process  of  identification  is  continued  by 
means  of  systematic  dyeing  tests  which  vary  with  the  auxochromes  and  salt-forming  groups  (see  p.  649),  imparting 
to  the  colouring-matter  a  basic,  acid,  phenolic,  substantive,  or  a  mixed  character,  such  as  basic  phenolic,  acid 
phenolic,  substantive  basic,  substantive  phenolic. 

The  group  with  azo-chromophores  contains,  for  example,  Bismarck  brown,  which  is  basic  (see  p.  656)  ;  metanil 
SO,H 


yellow, 


_  N  =  N— 


—  NH  — 


;  which  is   acid ;    alizarin  yellow   R, 


stantive ;    chromotrop  2R, 


)OH,   which  is   phenolic ;    Congo  red   (see   p.  657),   which  is   sub- 

CO2H 

SO,H 

/ — NH — N=\  /  =  o-  which  is  acid  phenolic  ;  carbazole  yellow, 


\ 
/ 


NH 


>— NH— N=: 


)— NH— N=r 


OH 


:=O 


SO3H 


which  is  substantive-phenolic  in  character. 


CO2Na 


DYEING    TESTS 

B.  Non-precipitation  of  the  solution  by  tannin,  &e.  (.t?r  above)  denotes  the  presence  of 
arid  colouring-matters  : 

(2)  The  solution  of  the  colour  is  reduced  as  in  (1)  or  with  Zn  -h  NH3  and  a  drop  placed 
on  a  strip  of  paper  : 

(2a)  The  reappearance  of  the  original  colour  on  shaking  the  paper  in  the  air  indicates 
sulphonic  or  mordant  dyes  of  the  groups  of  azines,  oxazines,  thiaziiies,  soluble  indulin, 
nigrosins  or  azocarmine,  thiocarmine,  indigo-carmine,  gallocyanine,  Mikado  orange. 

(26)  If  the  coloration  reappears  only  after  treatment  with  chromic  acid  or  ammonia 
vapour,  the  original  aqueous  solution  is  acidified  with  sulphuric  acid  and  shaken  with 
ether  ;  coloration  of  the  ether  and  complete  or  almost  complete  decolorisation  of  the  solu- 
tion indicates  phthaleins  or  auramines,  while  non-coloration  of  the  ether  shows  triphcnyl- 
methane  dyes. 

(2r)  Xon- coloration  of  the  paper  even  when  heated  in  a  flame  or  treated  with  ammonia 
vapour  points  to  azo-,  nitro-,  nitroso-,  or  hydrazine-colours,  which,  when  burnt  in  powder 
directly  on  a  platinum  foil,  give  coloured  vapours  (e.g.  naphthol  yellow  S,  picric  acid,  Victoria 
yellow). 

(2d)  If  on  reduction  the  solution  is  not  decolorised  but  becomes  reddish  brown  and  in 


In  the  group  with  hydroxyazinc  chromophorcs  are,  for  instance,  Meldola's  blue, 
K 


,  which  is  basic;   gallocyanine  (see  p.  661), 


N          CO2H 


C1(CH3)2N  O 

which  is  basic-phenolic  in  character. 

So,  also,  the  thiazinc  group  (see  p.  061)  contains  methylene  blue, which  is  basic,  and  thiomnnine,  which  is  acid. 

The  dyeing  tests  arc  made  in  hot  neutral  and  acid  baths,  in  each  of  which  tour  samples  arc  immersed,  nann-ly, 
cotton,  cotton  mordanted  witli  tannin,  wool,  and  wool  mordanted  with  dichromate  (for  the  mordanting,  see  pp.  651 
and  706).  The  more  or  less  intense  colours  assumed  by  the  samples  give  indications  concerning  the  character 
of  the  colouring-matter  (see  p.  650),  and  confirmation  of  this  is  obtained  by  various  tests  on  the  dyed  fabric  : 

(«)  The  colour  is  substantive  if,  when  the  dyed  sample  of  natural  wool  is  heated  in  faintly  alkaline  water,  the 
colour  passes  to  the  white  cotton  placed  in  (he  same  bath  ; 

(b)  The  colour  is  acid  if  the  change  indicated  in  it  is  not  observed,  and  if,  when  the  bath  is  acidified,  the  wool 
takes  up  the  colour  it  gave  up  to  the  alkaline  bath  ; 

(c)  The  colour  is  basic  if  in  bath  («)  t  be  colour  passes  from  the  wool  to  a  sample  of  white  cotton  mordanted  with 
tannin  ; 

(rf)  The  colour  is  phenolic  if  the  tint  on  mordanted  wool  varies  with  the  nature  of  the  mordant. 

Tests  may  also  be  made  on  the  solution  of  the  colouring-matter  ;  thus,  if  it  is  precipitated  by  tannin  or  picric 
acid,  the  colour  is  basic  ;  if  ether  extracts  the  colouring-matter  in  an  acid  medium,  the  colour  is  phenolic,  whereas 
if  ether  extracts  the  coloured  base  in  an  alkaline  medium,  the  colour  is  basic. 

If  it  is  established  that  the  colouring-matter,  containing  a  given  chromophore,  is  basic  in  nature,  all  acid,  sub- 
stantive, phenolic,  A-c.,  colouring-matters  with  the  same  chromophore  are  excluded. 

1).  For  the  further  individualisation  of  the  colouring-matter,  useful  information  is  given  by  the  following 
reactions  characteristic  of  the  substituent  radicals. 

The  NH2  group  is  recognised  by  diazotising  and  then  coupling  (see  p.  658),  by  which  means  a  new  azo-  colouring- 
matter  is  formed,  or  by  boiling  the  diazotised  product  with  water,  the  formation  of  the  OH  group  being  shown 
by  the  increased  solubility  in  NaOH  compared  with  that  of  the  original  colour. 

The  more  or  less  basic  groups  are  indicated  by  the  greater  or  less  sensitiveness  of  the  solutioii  to  mineral  acids  : 

The  N(CH3)2  group  is  sensitive,  as  seen  in -methyl  violet  and  methyl  orange  ; 

The  NH2  group  is  less  sensitive,  as  in  fuchsine  and  acid  yellow  ; 


The  group  — NH- 


is  less  sensitive  still,  as  in  aniline  blue  and  metanil  yellow.    Different  colorations 


with  different  concentrations  of  acid  indicate  several  salt-forming  groups. 

To  complete  the  characterisation  of  a  colouring-matter,  the  latter  must  be  tested  for  halogens  and  nitro-groups. 


Thus,  to  distinguish  alizarin  yellow  11  (see  above)  from  diamond  yellow  O,  CO2H( 


>OH,  the 


CO2H 

nitro -group  is  tested  for  by  reduction  and  diazotisation,  its  presence  indicating  alizarin  yellow.  Other  colouring- 
matters  are  differentiated  by  testing  for  chlorine  and  bromine.  The  azo-dyestufls  are  characterised  also  by  the 
formation  of  the  corresponding  diazonium  nitrates  when  treated  with  concentrated  nitric  acid  : 


)OH 


)OH 


SO, II 


then  by  testing  for  diazo-eompound  with  /3-naphthol  and  ascertaining  the  solubility  of  the  nitro-derivative,  the 
position  of  the  sulphonic  group  in  the  molecule  may  be  determined. 

The  Tables  given  on  pp.  674-679  afford  considerable  help  in  the  rapid  characterisation  of  colouring-matters. 

n  43 


674 


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ABBEEVI 

G80  O  R  G  A  NIC    CHEMISTRY 

the  air  regains  its  original  colour  more  or  less,  alizarin  S,  alizarin  blue  S,  and  the  like  are 
indicated. 

(2e)  Complete  or  almost  complete  failure  of  Zn  -I-  NH,j  or  Zn  +  HC1  to  decolorise  the 
solution  shows  thiazole  yellow,  mimosa,  quinoline  yellow  S,  primuline,  thioflavin  8,  chlor- 
amine  yellow,  &c. 

II.  If  the  colouring-matter,  in  a  little  water  and  HC1,  is  precipitated  and  gives  an  evolu- 
tion of  SH2  (detectable  with  lead  acetate  paper),  and  is  redissolved  in  10  per  cent,  sodium 
sulphide  solution,  the  presence  of  a  sulphur  dyestuffis  certain. 

III.  If  the  colouring-matter  is  insoluble  in  water,  it  is  moistened  and  treated  with  a 
couple  of  drops  of  5  per  cent.  NaOH  solution  : 

A.  If  it  dissolves  it  is  reduced  with  zinc  dust  and  ammonia  and  a  paper  streaked  wilh 
it :  (1 )  The  rapid  reappearance  of  the  original  colour  in  the  air  shows  coerulein,  gallocyanine, 
gallein,  galloflavin,  alizarin  blue,  black,  or  green  ;    (2)  the  non-appearance  of  the  colour 
in  the  air  indicates  alizarin  derivatives,  alizarin  itself,  nitrosonaphthol,  nitrosoresorcinol, 
Soudan  brown,  &c. 

B.  The  colouring-matter  does  not  dissolve  in  NaOH  but  is  soluble  in  70  per  cent,  alcohol: 
(a)  the  solution  shows  fluorescence,  which  with  33  per  cent.  NaOH  solution  either  disappears 
(Magdala  red)  or  does  not  disappear  (alcohol-soluble  eosin,  cyanosine)  ;    (b)  the  solution 
is  not  fluorescent  and  is  coloured  reddish  brown  by  33  per  cent.  NaOH  (alcohol-soluble 
indulin,  alcohol-soluble  nigrosin,  alcohol-soluble  aniline  blue)  ;  (r)  the  solution  remains 
fluorescent  (indophenol). 

C.  The  colouring-matter  dissolves  in  neither  NaOH  nor  70  per  cent,  alcohol  [indigo, 
alizarin  black,  sulphur  colours  (soluble  in  sodium  sulphide)]. 

Green  (1905)  has  shown  that  the  different  groups  of  colouring- matters  may  lie 
characterised  by  their  behaviour  towards  the  compound  of  sodium  hydrosulphite  with 
formaldehyde. 

RECOGNITION  OF  THE  PRINCIPAL  COLOURING-MATTERSON  DYED  FIBRES. 
When  the  nature  of  a  colouring-matter  is  to  be  studied,  a  dyeing  test  should  always  be 
made  first  (see  later)  and  the  tests  described  below  carried  out  in  the  cold  on  the  dry,  dyed 
fabric,  a  small  piece  (about  1  sq.  cm.)  being  treated  in  a  porcelain  dish  with  1  to  2  c.c.  of 
the  reagent  and  any  change  observed.  In  testing  with  nitric  acid,  one  or  two  drops  of 
the  latter  are  placed  on  the  fabric  and  the  colour  of  the  drop  and  that  of  its  edges  noted. 
The  hydrochloric  acid  solution  of  stannous  chloride  is  prepared  by  dissolving  100  grins, 
of  the  latter  in  100  grms.  of  the  concentrated  acid  and  50  grms.  of  water.  Abbreviations 
of  the  names  of  the  colours  and  of  the  changes  produced  are  used,  and  when  a  compound 
colour  is  formed,  it  is  indicated  by  the  two  fundamental  colours  composing  it  ;  thus 
combination  of  red  (R)  and  yellow  ( Y)  gives  scarlet  (RY),  green  (Gn)  and  brown  (Br)  give 
olive  (Gn  Br),  &c.  (.see  Note  at  foot  of  Table,  pp.  G74  at  seq.). 

To  ascertain  if  an  indigo  dye  on  wool  contains  also  logwood  or  aandalwood,  a  piece  of 
the  fabric  is  heated  with  dilute  nitric  acid  (1:6);  indigo  alone  gives  a  straw-yellow,  while 
in  presence  of  either  of  the  other  colouring- matters,  a  more  or  less  brownish  colour  is 
obtained.  Or  the  shredded  dyed  textile  is  heated  for  an  hour  with  fused  phenol  on  the 
water-bath,  the  phenol  being  decanted  off,  the  operation  repeated  with  fresh  phenol,  and 
the  material  washed  two  or  three  times  with  strong  alcohol  and  pressed.  If  the  wool  were 
dyed  with  pure  indigo  it  will  be  quite  white,  but  if  there  were  threads  dyed  with  other 
colours  (e.g.  anthracene  blue,  sandalwood,  &c.)  these  are  seen  under  the  microscope  to 
be  still  coloured. 

According  to  E.  Knecht  (1909)  the  indigo  on  a  cotton  fabric  may  be  determined  quanti- 
tatively as  follows  :  4  grms.  of  the  fabric,  cut  into  pieces,  are  dissolved  at  40°  in  25  c.c. 
of  80  per  cent,  sulphuric  acid  ;  the  volume  is  then  made  up  to  120  c.c.  with  water,  the 
indigotin  of  the  soluble  sulphate  being  thus  precipitated.  This  is  collected  on  a  Gooch 
filter,  dried  at  110°  to  115°  and  weighed.  It  may  be  redissolved  in  a  little  sulphuric  acid 
by  heating  on  the  water-bath  for  an  hour,  the  indigotinsulphonic  acid  in  the  diluted 
solution  being  titrated  with  permanganate.  The  pre?*ence  of  basic  or  sulphur  colours 
does  not  interfere  with  the  estimation,  since  these  either  remain  dissolved  or  are 
decomposed.  If  the  fabric  has  a  coating  of  manganese  dioxide,  it  must  first  be  dissolved 
in  bisulphite. 

p-Nitraniline  red  may  be  distinguished  from  other  reds  (Turkey-red,  benzo  purpurin, 
primuline,  &c.)  on  cotton  by  heating  the  fabric  at  one  point  over  a  small  flame  ;  a  clear 


WOOL 


681 


spot  is  formed  and  part  of  the  colour  sublimes  on  to  a  piece  of  paper  placed  above  the 
fabric.  The  spot  does  not  resume  its  original  colour  either  on  cooling  or  on  moistening 
(Knecht,  1!X>5). 

TEXTILE  FIBRES 

Before  a  description  is  given  of  the  processes  and  plant  used  in  dyeing  textile  Hbres, 
the  physico-chemical  properties  of  these  may  be  outlined. 

WOOL.  Only  sheep  and  certain  goats  furnish  true  wool  used  in  the  great  textile 
industries.  The  wool  fibre  is  readily  distinguished 
from  the  hairs  of  other  animals  by  its  softness  and 
fineness  and  by  its  waviness  and  curling,  which  can 
be  seen  with  the  naked  eye.  Also  under  the  micro- 
scope a  marked  difference  from  all  other  hairs  is  easily 
discernible  (Figs.  424  and  425).  The  whole  filament 
seems  to  be  composed  of  closely  superposed  scales, 
which  are  more  or  less  large  according  to  the  quality 
of  the  wool.  It  is  the  saw-like  or  serrated  structure 
of  these  scales  which  explains  why  wool  readily 
forms  a  felt  when  rubbed,  the  filaments  becoming 
more  or  less  firmly  attached  one  to  the  other.1 

The  quality  of  a  wool  is  closely  dependent  on  the 
breed  of  sheep  producing  it  and  only  partially  on  the 
climate,  food,  and  age.  The  yield  of  wool  is 
greatest  from  the  second  to  the  sixth  year.  The 
finer  wools,  furnished  generally  by  the  merino  breed,2 
are  long,  slender,  soft,  and  very  wavy  and  form  the 
so-called  combing  wool  for  the  best  woollens.  Shorter 
wools  cannot  be  combed  but  only  carded  (Hiksian,  AWvm),  although  nowadays  nearly 
all  could  be  combed  with  the  improved  machinery  available,  and  a  large  part  of  the  carded 


FIG.  424. 


II 


III 


IV 


FIG.  425. 

'  The  whole  of  the  wool  covering  the  sheep  forms  the  fleece,  which  is  kept  entire  even  after  shearing  (this  is 
done  in  May)  owing  to  the  scaly  structure  of  the  filaments.  Wool  obtained  by  shearing  twice  a  yenr  is  called 
liistose,  while  that  from  slaughtered  sheep  is  termed  skin  ivool  and  frequently  contains  dead  hairs,  which  have 
little  affinity  for  colouring-matters  and  arc  often  impure  owing  to  the  use  of  lime,  arsenic,  &c.,  as  preservatives. 
If  the  sheep  is  washed  in  the  tank  before  shearing,  the  wool  is  known  as  washed,  the  other  being  called  in  grease  or 
unwashed. 

The  fleece  (weighing  2-5  to  3  kilos)  contains  different  parts  of  different  qualities  and  these  the  sorters  separate 
by  cutting.  In  one  and  the  same  fleece  the  finest  wool  is  that  of  the  shoulders,  then  conies  that  of  the  neck,  stomach, 
flanks,  and  back,  the  poorest  qualities  being  those  of  the  head  and  legs.  Certain  African  sheep  (Morocco),  and, 
to  some  extent,  the  Lincoln,  Leicester,  and  Wellington  breeds  give  long,  coarse,  and  only  slightly  curved  fibres, 
which  are  used  for  special  fabrics  and  for  mattresses. 

*  Merinos  are  indigenous  to  the  plains  of  Estremadura  and  Andalusia  (Spain),  where  they  were  jealously 
guarded  for  some  centuries,  exportation  being  prevented.  In  the  nineteenth  century  the  Spaniards  themselves 
introduced  them  into  the  Argentine,  where  three  principal  types  were  developed  :  Rambouillet,  Negrette,  and  Lincoln, 
and  a  similar  result  followed  the  concessions  made  to  France  and  Sweden.  The  English  introduced  them,  with 
great  success,  into  Australia  and  Cape  Colony.  Ths  Electoral  breed  originated  in  merinos  which  were  imported 
in  ]  760  into  the  Electorate  of  Hesse,  and  spread  into  Silc.-sia,  Saxony,  Wiirtcmberg,  Hanover,  Moravia,  and  Hungary  ; 
it  now  furnishes  a  large  proportion  of  the  raw  material  of  German  and  Austiian  wool  factories. 

In  England  the   C'/ieviot   breed   has  assumed  considerable  importance  and   yields   a  long,  yellowish  wool, 


682 

wool  is  obtained  from  shoddy.1  The  lengths  of  wool  fibres  vary  from  4  cm.  to  30  cm. 
and  the  diameter  from  0-014  mm.  to  0-06  mm.  The  finer  wools  (merinos,  Fig.  424)  have 
as  many  as  13  waves  per  centimetre,  while  the  more  ordinary  ones  have  only  3  (Fig.  424  B, 
natural  size). 

The  number  of  sheep  in  different  countries  in  1906  was  as  follows  (in  millions) :  Australia, 
72-8  ;  Argentine,  74-4  ;  Russia,  61-5  ;  United  States,  50-6  ;  England,  29-2  ;  New  Zealand, 
20-1;  Uruguay,  17-9;  France,  17-8;  British  India,  17-6;  Spain,  13-3;  Cape  Colony, 
11-8;  Algeria,  9-1;  Hungary,  8-1;  Germany,  7-9;  Italy,  11-2  (in  1908);  Bulgaria, 
6-9;  Roumania,  5-7;  Mexico,  3-4;  Servia,  3-1;  Austria,  2-6 ;  Canada,  1-8;  Sweden, 
1-1  ;  Norway,  1  ;  Denmark,  0-9  ;  Holland,  0-7  ;  Natal,  0-6  ;  Belgium,  0-2  ;  Switzer- 
land, 0-2. 

The  world's  production  of  wool  in  1903  was  about  1,300,000  tons,  namely,  450,000  in 
Europe,  140,000  in  North  America,  240,000  in  South  America,  2500  in  Central  America 
and  the  West  Indies,  130,000  in  Asia,  240,000  in  Australia,  60,000  in  Africa,  and  23,COO 
in  Oceania.  For  the  separate  countries  the  figures  (tons)  were  as  follow  :  United  States, 
130,000;  England  and  Ireland,  60,000;  France,  48,000;  Spain,  4800;  British  South 
Africa,  47,000  ;  Uruguay,  45,000  ;  British  India,  40,000  ;  European  Turkey  and  Balkan 
Peninsula,  30,000  ;  Austria-Hungary,  29,000  ;  Russia  in  Asia,  27,000  ;  Germany ,  23,000  ; 
Central  Asia,  22,000  ;  China,  16,000  ;  Asiatic  Turkey,  15,000  ;  Algeria  and  Tunis,  14,000  ; 
Italy,  10,000  ;  Venezuela,  7000  ;  Portugal,  6000  ;  Norway  and  Sweden,  3500  ;  Chili, 
3500  ;  Mexico,  2300  ;  Egypt,  1400  ;  and  Brazil,  700. 

The  Argentine  Republic  exported  less  than  18,000  tons  in  1860,  nearly  66,000  in  1S70, 
about  98,000  in  1880,  about  120,000  in  1890,  and  more  than  200,000  (and  34,000  tons  of 
skins)  in  1895,  while  in  1905  the  exports  were  about  191,000  tons  of  wool  and  27,000  tons 
of  skins,  besides  120,000  live  sheep  and  3,325,000  frozen  carcases. 

The  wool  exported  from  Morocco  in  1908  was  valued  at  £240,000,  that  from  Algeria 
in  1906  at  £720,000  (£640,000  to  France),  and  that  from  Tunis  in  1906  at  £100,000. 

The  great  market  for  wool  in  Europe  is  at  Antwerp,  and  the  price  is  fixed  by  auction, 
account  being  taken  of  the  yields  of  the  various  wools  (Conditioning,  see  later)  after  washing, 
some  of  them  losing  40  to  70  per  cent,  of  their  weight  owing  to  the  removal  of  dirt,  grease, 
&c.  ;  the  normal  or  natural  moisture,  after  washing  and  drying,  is  taken  as  18-25  per  cent. 
The  price  of  raw  wool  varies  somewhat  from  year  to  year  and  even  in  the  same  season 

not  so  flue  as  merino.      Crossbreeds,  obtained  by  crossing  Argentines  with  Cheviots,   arc  also  largely  bred  in 
England. 

The  Russian  breeds  are  derived  from  pure  and  Saxon  merinos.  The  commonest  varieties  are  the  fitiugsk, 
aidarsk,  rescetiovesk,  and  romanovsk  (this  is  used  for  furs).  In  France  the  wool  of  the  Burgundy  and  of  the  Berry 
uhighly  valued.  » 

Italian  wools,  which  were  once  famous,  are  now  of  little  importance,  and  only  Apulia,  the  Tuscan  marshes, 
and  the  Roman  province  furnish  a  small  part  of  the  wool  consumed  in  Italy. 

Good  wool  is  also  obtained  from  certain  breeds  of  goats,  such  as  those  of  Cashmir,  which  flourish  in  the  Himalayas, 
nearly  5000  metres  above  sea-level.  They  furnish  a  very  fine  wool  mixed,  however,  with  much  white  or  grey 
hair  ;  it  is  exported  to  France  and  Russia.  The  Thibetan  goat,  acclimatised  also  in  France  and  in  Bengal,  likewise 
yields  a  valuable  wool.  The  Angora  goat  of  Asia  Minor  gives  milk  and  a  long  wool  (mohair)  valued  for  its  lustre, 
even  after  dyeing. 

The  vicuna  of  the  Peruvian,  Chilian,  and  Mexican  mountains  gives  a  fine  wool,  used  in  certain  cloths,  which 
are  now  made  partly  from  rabbit  fur  (the  name  vicuna  or  vigogne  yarn  is  also  applied  to  fabrics  of  wool  and  cotton 
which  are  quite  distinct  from  vicuna  wool).  Alpaca  is  greyish,  and  is  fuinished  by  a  kind  of  tall,  long-necked 
sheep  (llama)  indigenous  to  Peru.  Camel-hair,  which  is  worked  like  wool,  has  coarse  fibres,  and  in  its  natural 
colour  is  woven  into  certain  very  strong  textiles  used,  for  instance,  for  the  seats  and  curtains  of  railway  carriages. 
1  Shoddy  is  obtained  by  disintegrating  woollen  rags  (previously  sorted  with  respect  to  colour,  and  separated 
from  those  mixed  with  cotton)  by  means  of  an  opener  or  devil,  formed  of  a  drum  furnished  with  a  number  of  steel 
points  and  rotating  rapidly  inside  a  second,  fixed  drum  also  provided  with  points  ;  from  this  the  rags  issue  in  short, 
flocculent  fibres,  which  are  carded  and  then  spun.  This  industry,  started  in  England  in  1845  and  since  then 
extended  to  other  countries,  allows  of  the  utilisation  of-  all  woollen  waste  (fabrics  and  yarn) ;  England  alone 
imports  from  all  parts  of  the  world  about  15,000  tons  of  woollen  rags  per  annum.  The  coloured  rags  may  often 
be  partially  decolorised  by  boiling  them  with  2  to  3  per  cent,  potassium  dichromate  and  a  little  sulphuric  acid. 
Admixed  cotton  (sewing  and  other)  may  be  eliminated  from  the  rags  by  so-called  carbonisation,  which  consists 
in  immersing  the  rags  in  sulphuric  acid  (4°  to  5°  Be\),  centrifuging  and  heating  them  in  ovens,  the  temperatme 
of  which  is  raised  to  120°  to  140°.  In  the  course  of  an  hour  the  cellulose  of  the  cotton  is  transformed  into  brittle 
hydrocellulose  and  partly  carbonised,  so  that  it  can  be  easily  removed^by  subsequent  rubbing  or  by  washing  with 
water,  this  also  carrying  away  the  acid  from  the  wool,  which  is  not  affected  by  such  treatment.  In  some  cases, 
hydrochloric  acid  vapour  or  aluminium  chloride  solution  is  used  instead  of  sulphuric  acid.  The  carbonised  wool 
shows  increased  affinity  for  acid  colouring-matters. 

Also  woollen  fabrics  which  contain  bits  or  fibres  of  cotton  in  such  quantity  that  it  is  impracticable  to  pick  them 
out  by  hand,  are  carbonised  with  sulphuric  acid  or  aluminium  chloride  before  dyeing  and  are  thoroughly  washed 
after  removal  from  the  oven. 

Decolorised  shoddy  mixed  with  new  wool  can  he  recognised  under  the  microscope  owing  to  its  different  colour, 
which  often  recalls  the  original  tint.  Italy  produces  annually  100,000  to  120,000  quintals  of  shoddy. 


WOOL  683 

from  about  Is.  2d.  to  2s.  per  kilo.  Australian  wool  is  worth  more  than  that  from  the 
Argentine. 

Unwashed  wool  (Australian  weighs  about  160  kilos  per  bale),  after  sorting,  is  washed 
with  soap  and  soda  at  45°  to  50°  in  vessels  (Leviathans)  provided  with  loose  forks  for  mixing 
and,  when  rinsed,  is  dried  in  revolving  drums  by  means  of  hot  air.  The  washed  (or  salted, 
such  as  Italian  or  Cape  wool,  weighing  about  110  kilos  per  bale)  wool  is  then  carded  or 
combed.  In  some  districts  the  washing  is  preceded  by  treatment  with  benzene  to  remove 
the  grease  (see  p.  393). 

The  great  European  market  for  combed  wool,  not  yet  spun  but  wound  into  balls  of 
4  to  5  kilos  (tups),  is  in  France,  at  Roubaix  (and  also  at  Tourcoing  and  Lille),  where  prices 
are  fixed  at  auction,  although  there  is  a  considerable  trade  in  combed  wool  at  Bradford 
and  to  a  less  extent  at  Leipzig. 

These  wools  are  classified,  according  to  their  fineness,  as  A,  B,  ...  F,  the  first  being 
the  finest  and  the  last  the  commoner  sorts  ;  very  fine  wools  are  marked  AA  or  AAA. 

Before  being  spun  the  washed  wool  is  subjected  to  the  operation  of  blending,  i.e.  the 
various  qualities  of  wool  (fine,  ordinary,  long,  short,  waste,  shoddy,  &c.)  being  mixed  so 
as  to  obtain  yarn  of  the  desired  count  and  fabric  corresponding  with  the  price  and  quality. 
To  facilitate  spinning  and  avoid  felting,  the  wool  is  slightly  oiled  (with  olive  oil,  commercial 
oleine,  soap  emulsion,  &c.,  but  not  with  non-saponifiable  substances,  such  as  mineral 
oils  or  resins,  which  would  be  difficult  to  remove  from  the  fabric  by  washing,  and  would 
lead  to  irregular  dyeing).  In  passing  through  the  combs  or  cards,  the  various  fibres  are 
perfectly  mixed  and  rendered  parallel.  The  coarse  strands  (tops)  are  gradually  converted 
into  finer  but  not  twisted  strands,  which  are  wound  on  bobbins  (prepared)  and  are  then, 
by  means  of  ingenious,  self-acting  machines  of  enormous  capacity,  spun  to  the  desired 
fineness  to  give,  when  twisted,  yarn  of  the  required  count.1  During  spinning,  the  air  of 
the  room  must  be  kept  moistened  with  water  vapour  (see  vol.  i,  p.  291)  to  prevent  the  parallel 
fibres  from  diverging  and  giving  a  non-uniform  yarn.  Satisfactory  weaving  also  requires 
a  certain  degree  of  moisture. 

Italy's  imports  and  exports  of  wool  (raw,  carded,  combed,  spun,  woven,  &c.)  from 
1905  to  1910  were  as  follow: 


1905 

1906 

1907 

1908 

1909 

1910 

Imports,  quintals 
Exports,        ,, 

184,936 
59,164 

202,834 
47,996 

228,626 

38,862 

257,808 
28,348 

265,643 
39,351 

278,432  (£5,736,600) 
41,697  (£1,043,500) 

Woollen  yarns  of  counts  above  10  (international)  pay  52s.  per  quintal  on  entry  into 
Italy,  while  combed  wool  fabrics  weighing  less  than  200  grms.  per  sq.  metre  pay  £10  per 
quintal.  The  quantity  of  wool  consumed  (production  +  importation  —  exportation)  in 
Italy  was  20,160  tons  in  1886  and  about  28,000  in  1905. 

The  imports  of  raw  wool  into  Japan  were  :  1700  tons  in  1894,  9622  tons  (£1,028,000) 
in  1904,  and  10,240  tons  (£1,880,000)  in  1907. 

Chemical  Properties  of  Wool.  Pure  wool  consists  of  C,  H,  O,  N,  and  S,  the  last  varying 
somewhat  in  amount  and  being  partly  removed  by  repeated  washing  in  boiling  water. 
It  is  hence  improbable  that  wool  consists  of  a  single  chemical  compound  (it  was  at  one  time 
thought  to  be  keratin,  containing  4  to  5  per  cent.  S,  but  there  appear  to  be  other  substances 
also).  In  1888  Richard  showed  that  the  compounds  forming  wool  contain  NH2  and  NH 
groups.  In  a  solution  of  alkali  or  a  salt,  wool  fixes  chemically  part  of  the  alkali  or  salt. 
Concentrated  alkali  dissolves  wool,  forming  amino-acids,  the  most  important  being  lanugic 
acid,  which  was  isolated  by  Knecht  and  Appleyard  and  exhibits  the  same  behaviour 
towards  colouring-matters  as  does  wool. 

1  The  Count  of  Yarn,  either  cotton  or  wool,  is  given  by  the  number  of  kilometres  weighing  1  kilo  (international 
count)  or  half  a  kilo  (French  count).  In  Great  Britain,  the  count  represents  the  number  of  hanks  of  840  yards 
(1  yard  =  0-914  metre)  per  1  Ib  (453  grms.) ;  hence  English  count  No.  1  is  equal  to  French  count  No.  0-847  and  to 
international  count  No.  1-694.  Division  of  the  international  count  by  1-66  gives  the  English  count,  multiplication  of 
the  French  count  by  2  gives  the  international  count,  while  division  of  the  English  count  by  1-18  gives  the  French 
count. 

A  thread  spun  from  two  yarns  of  count  60  has  the  count  30.  its  weight  per  unit  length  being  doubled.  Fine  wools 
are  spun  so  as  to  give  a  count  of  CO  to  80  or  even  of  120,  while  the  commoner  qualities  give  counts  of  'SO  or  even  less. 

For  till;  the  International  Congress  at  Paris  in  1900  accepted  the  Italian  count,  which  expresses  the  weight 
in  denari  (one  denaro  =  0-05  grm.)  of  a  length  of  -150  metres,  tlic  finer  yarns  thus  having  the  lower  counts.  Silk 
is  often  spun  to  a  count  of  12  to  20  denari,  and  artificial  silk  to  60  to  120  denari. 


684 


ORGANIC    CHEMISTRY 


It  is  probable,  therefore,  that  wool  contains  at  least  one  carboxyl  group.  The  affinity 
of  wool  for  acid  colouring-matters  (often  sulphonic  acids)  is  explained  by  the  presence 
of  amino-groups  and  that  for  basic  dyes  by  the  presence  of  the  carboxyl  group.  Certain 
highly  basic  colouring -matters  (such  as  methyl  green)  do  not,  however,  colour  wool,  the 
acid  character  of  which  is  too  weak,  while  they  colour  silk,  which  is  more  markedly  acid. 
The  fixation  of  metallic  oxides  (of  Cr,  Fe,  Cu,  Al,  &c.)  in  the  mordanting  of  wool  is  due  to 
the  formation  of  salts  with  the  carboxyl  group. 

The  salt-forming  property  of  wool  can  be  easily  demonstrated  by  immersing  it  in  a  hot 
colourless  solution  of  rosanilinc  (base),  which  colours  it  red  just  as  though  it  were  dyed 

with  red  rosaniline  hydro - 
chloride.  Knecht,  Witt,  and 
Nilsen  have  shown  that  the 
action  of  chlorine  on  wool  is 
to  intensify  its  acid  character, 
so  that  it  fixes  basic  dyes  the 
more  readily  ;  at  the  same 
time  it  loses  partially  its  capa- 
city to  felt. 

Bolley  found  that  wool  de- 
composes potassium  bitartrale 
in  boiling  solution,  generating 
the  neutral  tartrate  and  lixing 
tartaric  acid.  In  1898  Kertesz 
utilised  industrially,  for  the 
simultaneous  production  of  two 
colours  on  wool,  the  property 
this  shows  of  fixing  acid  colour- 
ing-matters more  intensely  at 
points  where  it  has  been  care- 
fully treated  with  caustic  soda, 
the  latter  neutralising  the  carb- 
oxyl group  and  thus  rendering 
the  basic  character  more  pro- 
nounced. 

Wool  loses  much  of  its 
affinity  for  acid  colours  when 
treated  with  phosphotungstic 
acid,  but  recovers  it  when 
subjected  to  the  action  of 
ammonium  bicarbonate  (Scrida, 
1909). 

Of  practical  importance  is  the  behaviour  of  wool  (or  cotton)  waste  containing  ordinary 
oils  or  fats  (not  wool-fat),  as  it  readily  ignites  owing  to  energetic  oxidation  and  causes 
fires  (see  Pyrophoric  Substances,  vol.  i,  p.  174). 

An  aqueous  extract  of  pure  wool  gives  a  precipitate  with  either  tannin  or  basic  lead 
acetate,  while  true  glue  or  gelatine  yields  no  precipitate  with  the  latter  reagent.  Pure 
wool  contains  14  per  cent.  N. 

COTTON  is  the  white  down  surrounding  the  black  cotton-seed  and  is  contained  in  capsules 
(each  weighing  about  30  grms.,  10  grms.  being  cotton)  which,  to  the  number  of  300  to  400, 
form  the  fruit  of  Gossypium — a  shrub  2  to  4  metres  in  height  (see  Fig.  426).  When  the 
fruit  is  ripe  (in  America  in  August),  the  capsule  opens  and  throws  out  a  white  tuft  of  cotton, 
which  is  fixed  to  the  seeds.  After  harvesting,  the  cotton  is  freed  from  seeds  by  means 
of  cotton-gins  and  compressed  hydraulically  into  bales  holding  180  to  200  kilos.  Cotton, 
is  produced  most  abundantly  in  North  America  and,  tosa  less  extent,  in  South  America 
(Brazil,  Peru,  Colombia,  &c.),  and  the  Antilles  (Haiti,  Cuba,  &c.).  Its  cultivation  is  also 
of  importance  in  the  East  Indies,  Syria,  Macedonia,  &c.  Egyptian  cotton  (makb)  is  valued 
on  account  of  its  lustre  and  length  of  fibre.  Cotton  is  also  grown  in  Australia.  Attempts 
have  recently  been  made  to  cultivate  it  in  the  Italian  colony  of  Eritrea,  but  without  great 
success. 


FIG.  426. 


MERCERISED    COTTON 


685 


The  best  qualities  have  fibres  30  to  40  mm.  in  length  and  the  lower  qualities  10  to 
14  mm.  The  fibres  are  0-015  to  0-020  mm.  in  thickness  and  under  the  microscope  have 
the  appearance  of  flattened  ribbons  with  a  twist  here  and  there  (Fig.  427,  the  upper  part 
of  which  shows  the  transverse  sections).  When  treated 
with  ammoniacal  copper  oxide  solution,  cotton  swells 
very  considerably,  forming  superposed  capsules  sepa- 
rated by  constrictions  (Fig.  428).  By  cold  concen- 
trated caustic  soda  solution  (30°  to  35°  Be.)  the  flat 
fibre  is  converted  into  a  cylindrical  one  almost  circular 
in  section  (Fig.  427  /  ;  see  Mercerisation)  with  a  thin 
central  channel.  If  immersion  in  the  soda  is  prolonged 
for  two  or  three  minutes,  during  which  the  skein  or 
fabric  is  kept  stretched,  and  the  soda  is  subsequently 
washed  away  while  the  tension  is  maintained,  the  skein 
will  not  contract  and  the  fibres  present  a  lustrous 
appearance  (mercerised  cotton)  and  are  stronger  and 
heavier  than  in  their  original  state  (soda-cellulose  and 
then  hydrocellulose  are  formed).1 

The  chemical  characters  of  cotton  are  those  of 
cellulose  described  on  p.  503,  purified  cotton  being 
pure  cellulose.  For  its  behaviour  towards  different 
dyes,  see  p.  651,  and  also  later. 

The  world's  production  of  cotton  is  about  3,500,000 
tons  per  annum,  about  three-fifths  of  this  quantity 
being  given  by  the  United  States,  which  exports  about 
1,700,000  tons,  nearly  one-half  to  England,  about  one- 
quarter  to  Germany,  and  the  remaining  quarter  to 

1  History   and    Properties    of    Mercerised   Cotton.      In  1844 

J.  Mercer,  chemist  in    a    Lancashire   calico-printing  works,  having  Flo.  427. 

filtered  a  concentrated  caustic  soda  solution  through  a  cotton  filter,  (Magnified  300  timos) 

noticed  that  the  cloth  had  contracted  somewhat  and  had  become 
thicker  and  transparent.  Before  filtration  the  liquid  had  the  sp.  gr. 
1-300,  but  after  filtration  only  1-265.  On  studying  the  phenomenon 
more  closely,  Mercer  found  he  could  reproduce  it  at  will  with  yarn 
immersed  in  caustic  soda  solution  of  20°  to  30°  Be1.,  while  he  estab- 
lished with  certainty  that,  under  such  treatment,  the  cotton  fibre 
shortens  by  20  to  25  per  cent.,  thickens  and  becomes  stronger  (by 
about  50  per  cent.)  and  of  increased  affinity  for  colouring-matters. 
He  showed,  too,  that  the  phenomenon  is  more  rapid  and  more  intense 
at  low  temperatures,  while  at  the  boiling-point  no  contraction  occurs. 
Similar  changes  are  produced  by  treating  cotton  with  sulphuric  acid 
of  50°  to  55°  B6.  or  with  zinc  chloride  solution. 

In  October  1850  Mercer  was  granted  an  English  patent  (13,296)  for 
increasing,  by  this  treatment,  the  resistance  and  compactness  of 
cotton  and  its  affinity  for  dyes. 

In  1884  P.  and  C.  Depoully  patented  a  process  for  the  partial 
morcerisation  of  fabrics  by  which  parts  of  the  fabric  were  brought  FlG.  428. 

into  contact  with  an  alkali  solution  ;  these  parts  contracted  and  caused  (Magnified  200  times) 

the  other  parts  to  curl,  beautiful  crape  effects  being  thus  obtained. 

In  1896  the  textile  world  was  astounded  to  see  on  the  market  samples  of  fine  cotton  of  the  most  brilliant  colours 
and  the  lustre  and  feel  of  silk.  This  product  was  prepared  by  the  great  dyeing  firm  Thomas  and  Prevost  of 
Crefeld,  according  to  their  German  Patent,  No.  85,564  of  March  24,  1895,  which  reads:  ".  .  .  .  improvement  in 
the  mercerisation  of  vegetable  fibres  with  alkaline  or  acid  solutions,  by  subjecting  the  tightly  stretched  yarn  or  fabric 
to  the.  action  of  alkali  (caustic  soda  of  15°  to  32°  Be.),  or  of  acid  (sulphuric  acid  of  49-5°  to  55-5°  Be.),  the  stretching 
being  maintained  until  washing  is  complete— when  it  is  relieved  spontaneously— and  the  shortening  of  the  yarn 
or  fabric  thus  prevented."  The  specification  does  not  refer  to  the  lustre  assumed  by  the  yarn,  but  this  is 
mentioned  in  a  later  addition. 

These  Thomas  and  Prevost  patents  were,  however,  annulled  a  couple  of  years  later  in  all  countries,  since  various 
competitors  found  that  an  identical  process  had  been  patented  (No.  4452)  in  England  in  1890  by  H.  A.  Lowe  but 
had  not  been  renewed  within  a  year  because  Lowe  could  not  find  an  English  manufacturer  disposed  to  make  prac- 
tical use  of  it.  Large  quantities  of  mercerised  cotton  are  now  freely  produced  in  all  countries. 

The  shortening  of  the  fibre  and  its  increase  in  resistance  produced  by  concentrated  alkali  solution  may  be  under- 
stood if  the  changes  occurring  in  the  fibre  itself  are  followed  under  the  microscope.  While  the  fibre  of  ordinary 
cotton  is  seen  to  be  a  flattened  empty  tube  with  an  occasional  twist,  that  treated  with  caustic  soda  without  stretching 
is  shortened  and  swollen  and  forms  an  oval,  almost  round  tube  with  thickened  walls,  but  still  with  an  internal 
channel ;  outside  it  shows  creases  and  a  rough  surface.  But  by  mercerisation  under  tension,  the  fibre  becomes 
like  a  straight,  round  tube,  smooth  and  without  visible  creases  outside  and  almost  entirely  filled  up  inside.  These 
:hanges  explain  the  silky  lustre  and  also  the  increased  strength,  the  fibre  becoming  more  compact.  Buatroek'i 
experiments  showed  that  mercerisation  occurs  very  rapidly  :  with  caustic  soda  of  30"  Be.  the  shortening  of  the 
fibre  after  one  minute  is  23  per  cent,  and  after  33  minutes  29  per  ceut.,  which  is  the  maximum  attainable. 


686  ORGANIC    CHEMISTRY 

the  rest  of  Europe)  especially  France,  Austria,  and  Italy).  The  cotton  exported  from 
the  United  States  in  1901  represented  a  value  of  £62,000,000. J  Mexico  produces  45,000 
tons  ;  Egypt,  about  250,000  ;  British  India,  450,000  ;  Japan,  30,000  ;  and  in  the  South 
of  Italy  there  are  about  12,000  hectares  under  cotton,  about  5000  tons  being  produced. 
In  1899  Italy  imported  about  130,000  tons  of  cotton,  mostly  from  the  United  States.  The 
import  duty  in  Italy  is  29d.  per  quintal,  yarns  paying  from  14s.  to  48s.  according  to  the 
count  and  fabrics  48*.  to  104s.  ;  on  exported  yarns  and  fabrics  the  Government  grants  a 
rebate  of  3s.  per  quintal  for  yarns  and  3s.  6d.  for  fabrics  per  quintal  (freed  from  dressing), 
the  weight  of  the  cotton  being  increased  by  8  per  cent,  to  allow  for  its  natural  moisture. 

The  conversion  of  cotton  from  flock  to  yarn  is  effected  by  carding  or  combing  in  a  similar 
manner  to  shoddy  (see  above).  Very  fine  counts  (150)  are  spun  in  some  countries,  but  in 
Italy,  where  at  one  time  30  was  the  finest,  60  and  90  are  the  usual  ones,  although  130  is 
sometimes  obtained.  ... 

The  immense  importance  of  the  cotton  industry  is  shown  by  the  Table  on  page  687.  which 
refers  to  the  year  1905  (in  the  previous  year  the  production  was  13,635,000  bales). 

In  one  of  the  cotton  mills  of  the  United  States  1 34  workpeople  are  sufficient  to  overlook 
2000  Northrop  looms,  a  clever  workman  attending  as  many  as  20  looms,  while  with  the 
less  expert  the  number  never  falls  below  12  ;  these  looms  make  165  strokes  per  minute 
with  good  warp  and  weft. 

In  Italy  the  consumption  of  cotton  yarn  and  fabric  amounted  in  1905  to  813,000 
quintals,  or  2-5  kilos  per  head  of  the  population.  As  a  result  of  the  Turko-Italian  War 
Italy  has  lost  the  cotton  trade  in  the  Near  East,  which  it  had  previously  captured  in  com- 
petition with  England  and  Germany. 

Japan  in  1903  with  4933  looms  produced  69,800,000  metres  of  cotton  fabric,  the  exports 
being  valued  at  £720,000  ;  in  1905  7128  looms  turned  out  104,500,000  metres,  exports 

W.  Vieweg  (1908)  determines  the  degree  of  mercerisation  by  a  method  based  on  the  fact  that,  in  13  to  24  per 
cent.  NaOH  solution,  cotton  fixes  an  amount  of  NaOH  corresponding  with  (C0H10OD)jNaOH,  while  in  a  40  per 
cent,  solution  it  fixes  double  this  amount,  (C6H,0O5)22NaOH.  This  soda-cellulose  loses  its  soda  when  washed, 
and  the  recovered  cellulose  has  the  property  of  taking  up  more  or  less  caustic  soda  in  a  2  per  cent.  NaOH  solution, 
non-mercerised  cotton  fixing  1  per  cent.,  and  mercerised  1  to  3  per  cent,  of  NaOH  according  to  the  degree  of  previous 
mercerisation.  In  practice  this  degree  of  mercerisation  is  ascertained  as  follows  :  3  grms.  of  the  dry  mercerised 
cotton  are  shaken  for  an  hour  with  200  c.c.  of  exactly  2  per  cent.  NaOH  solution  in  a  separating  funnel,  50  c.c. 
of  the  solution  being  then  titrated  with  seminormal  acid  and  the  amount  of  NaOH  absorbed  by  the  cotton  calculated. 
A  qualitative  test  for  detecting  mercerised  cotton  mixed  with  ordinary  cotton  and  oxycellulose  was  given  on  p.  506. 
To  ascertain  if  a  fabric  is  mercerised  H.  David  (1907)  places  a  drop  of  concentrated  soda  on  the  fabric,  which  is 
then  washed  and  dyed  with  a  substantive  dye  ;  a  more  intense  colouring  on  the  place  touched  by  the  soda  indicates 
that  the  original  fabric  was  not  mercerised. 

When  cotton  is  mercerised  with  tension  its  strength  increases  by  35  per  cent.,  and  when  mercerised  without 
tension  by  as  much  as  68  per  cent.  The  elasticity  is  greater  in  cotton  mercerised  without  tension  (27  per  cent.), 
while  with  cotton  mercerised  under  tension  it  is  unchanged  (20  per  cent.).  The  lustre  of  mercerised  cotton  is  not 
altered  by  washing  or  dyeing. 

In  order  to  obtain  satisfactory  results  and  a  good  lustre  by  mercerising,  it  is  best  to  use  long-fibred  cotton  ; 
the  shorter  the  fibre  the  greater  must  be  the  tension.  It  is  also  necessary  to  boil  the  cotton  thoroughly  and  wash  it 
completely  before  placing  it  in  the  caustic  soda  bath,  as  otherwise,  besides  obtaining  less  lustre,  there  is  great 
danger  of  irregular  dyeing. 

The  dyeing  is  carried  out  in  the  usual  way  with  basic  dyes,  being  preceded  by  mordanting,  or,  better,  with 
substantive  dyes  in  baths  containing  a  little  Turkey-red  oil  or  soap,  the  temperature  being  kept  low  at  the  start 
to  avoid  non-uniformity.  Old  caustic  soda  baths,  which  become  largely  converted  into  sodium  carbonate  and  so 
diminish  in  activity,  can  be  used  for  soap-making. 

To  impart  a  silky  feel  to  mercerised  cotton,  the  latter  is  well  washed,  immersed  for  a  few  minutes  in  a  calcium 
acetate  bath  at  0-5°  B6.,  pressed,  introduced  into  a  bath  of  Marseilles  soap  (1  grm.  per  litre),  again  pressed,  placed 
in  an  acetic  or  tartaric  acid  bath  (10  grms.  per  litre)  and  finally  pressed  and  dried  without  washing. 

Mercerised  may  be  distinguished  from  unmercerised  cotton  by  immersion  in  a  solution  of  5  parts  KI  +  20 
water  +  2  iodine  +  30  ZnClj  in  12  water.  All  cotton  is  thus  coloured  blue,  but  thorough  washing  with  water 
decolorises  only  that  which  has  not  been  mercerised  (H.  Lange,  1903). 

1  The  increase  in  the  production,  consumption,  and  exportation  of  cotton  in  the  United  States  is  shown  by  the 
following  figures  [in  1874  the  production  (home  consumption  +  exportation)  was  3.500,000  bales  of  500  lb.]  : 

Home  consumption  Exports  Imports 

bales  bales  bales 

1903  .  .       v  .          .     3,980,567  6,290,245 

1904  .          ...  4,523,208  9,119,614 

1905  ...          .  4,877,465  6,975,494 

1906  ...          .  1,974,199  8,825.237                         202,733 

1907  .          .          .  4,493,028  7,779,508                         140,8fi9 


1909  .          .          .  10,300,000 

1910  .          .          .  12,000,000 

In  the  United  States  in  1907  cotton-seeds  gave  also  660,000  tons  of  oil  and  1,490,000  tons  of  pressed  oil-cake  for 
cattle-food.  These  products  were  partly  exported — oil  to  the  value  of  £3,400,000  and  cake  to  the  value  of 
£2,320,000. 


FLAX 


687 


Consumption 

Country 

umber  of 

Spindles 

Looms 

Workpeople 

in  bales  of 

mills 

200  to  225  kilos 

England           . 

2207 

50,964,874 

704,357 

550,000 

3,640,000 

United  States,  North 

573 

14,810,164 

340,682 

197,137 

2,167,700 

South 

659 

8,050,879 

174,324 

120,000 

2,203,406 

Russia    .          , 

227 

6,554,577 

154,577 

350,000 

1,177,000 

Poland              .   • 

56 

1,268,547 

12,000 

35,000 

325,000 

Germany 

870 

8,832,016 

211,818 

350,000 

1,761,369 

France   . 

420 

6,150,00(1 

206,000 

90,000 

840,000 

Austria  ... 

ISO 

3,280,330 

110,000 

100,000 

650,000 

Hungary 

3 

103,400 

— 

—  • 

— 

Switzerland 

68 

1,711,300 

17,385 

19,000 

100,000 

Italy       . 

760 

2,435,000 

110,000 

139,000 

560,000 

Spain      .          , 

257 

2,614,500 

68,289 

— 

300,000 

Portugal 

15 

160,000 

— 

— 

— 

Syria 

35 

372,000 

10,000 

— 

80,000 

Norway 

9 

87,832 

2,293 

2,635 

12,000 

Denmark 

3 

6.0,000 

— 

— 

18,000 

Holland.          . 

23 

376,234 

20,100 

17,000 

67,000 

Belgium 

43 

1,222,138 

24,000 

15,000 

100,000 

Roumania 

— 

40,000 

— 

— 

— 

Turkey  .          .          . 

5 

80,000 

':'!* 

— 

23,000 

Greece    . 

— 

970,000 

2,100 

— 

15,000 

Asia  Minor 

4 

60,000 

— 

— 

18,000 

India 

191 

5,119,121 

45,337 

184,779 

1,744,766 

China 

15 

620,000 

2,200 

— 

— 

Japan     .          . 

64 

1,332,000 

— 

68,261 

900,000 

Brazil     . 

142 

450,000 

23,000 

20,000 

250,000 

Canada  . 

22 

773,538 

18,267 

10,000 

99,000 

Mexico 

114 

628,096 

20,287 

26,000 

140,000 

Total 

6224 

119,127,146 

2,117,016 

2,295,120 

17,511,241 

being  £1,360,000,  and  in  1907  9260  looms  made  125,000,000  metres,  the  exportation 
amounting  to  £1,880,000. 

FLAX  (Linum  usitatissimum)  is  a  herbaceous  annual,  growing  usually  in  temperate 
regions,  and  reaching  a  height  of  60  to  80  cm.  (Fig.  429).  It  bears  clusters  of  blue  flowers 
which  give  capsules  (Fig.  430,  2)  containing  flattened  lenticular  seeds  (Fig.  430,  1).  It  was 
cultivated  first  in  Egypt,  then  in  Greece,  and  later  in  Italy  and  various  other  parts  of 
Euro[  j  (Belgium,  Holland,  Russia,  &c.)  ;  in  Italy  the  cultivation  has  diminished  very 
considerably,  although  it  is  still  followed  in  some  parts  and  is  carried  on  in  the  south  of 
Sicily  for  obtaining  the  seeds.  There  are  two  ordinary  varieties  which  are  grown  for 
both  fibre  and  seed  :  autumn  or  winter  flax,  which  has  a  coarse  fibre  and  is  sown  in  October 
and  harvested  at  the  end  of  spring,  the  ground  being  left  free  for  another  crop  ;  and  that 
sown  in  March,  which  is  pulled  in  the  summer  when  the  seeds  begin  to  brown  but  are  not 
quite  ripe.  Flax  plants  are  pulled  by  hand  and  arranged  in  sheaves  to  dry  and  to  mature 
the  seeds.  After  removal  of  the  latter  by  threshing,  the  plants  are  made  into  large  bundles, 
which  are  left  for  15  to  20  days  in  stagnant  water,  where  the  action  of  micro-organisms 
(Amylobacter,  butyric  bacteria)  results  in  the  dissolution  of  those  parts  of  the  tissues  which 
unite  the  long  fibres  to  the  cortex  and  to  the  pith.  The  bundles  are  then  opened  and  dried 
in  the  field.  Instead  of  being  retted  in  this  way,  flax  is  in  some  countries  heated  in  large 
autoclaves  for  half  an  hour  at  125°  with  water  from  a  preceding  operation  and  then  for  an 
hour  with  steam  at  a  pressure  of  5  atmos.  The  dried  flax  is  freed  from  the  friable  cortex 
by  bruising  between  sticks,  the  operation  being  completed  by  blows  from  scutching  knives 
(the  waste  forms  the  tow).  The  flax  is  then  combed  and  placed  on  the  market  in  large, 


688 


ORGANIC    CHEMISTRY 


twisted  tresses  of  200  to  300  grms.  at  144s.  per  quintal  or  80s.  to  96s.  for  short  fibre.     In 

Italy,  a  hectare  of  winter  flax  yields  about  300  kilos  of  fibre  and  900  kilos  of  seed,  March 

flax  giving  200  and  700  kilos  respectively  ;  in  Ireland,  Belgium,  and  Germany  double  as 

much  fibre  is  obtained.     The  world's  production  is  about  6,000,000  quintals,  more  than 

one-half  of  which  is  produced  in 
Russia  (where  1,000,000  hectares  are 
under  flax  and  two-thirds  of  the 
output  is  exported),  while  Germany 
produces  about  450,000  quintals 
//,_,  (importing  600,000  and  exporting 
250,000),  Austria'-Hungary  400,000, 
France  400,000,  Belgium  250,000. 
North  America  about  200,000,  Italy 
(from  52,000  hectares)  less  than 
150,000  (with  100,000  spindles  for 
flax  and  hemp),  and  England  about 
120,000  quintals.  England,  however, 
imports  700,000  quintals  of  flax  (two- 
thirds  from  Russia  and  one-third 
from  Holland  and  Belgium)  to  supply 
its  1,500,000  spindles  (three-fourths 
in  Ireland  for  fine  yarn  and  one- 
fourth  in  Scotland).  The  cultivation 
of  flax  is  falling  in  all  countries  except 
Russia.  Thus,  France  had  at  one 
time  120,000  hectares  under  flax  but 
now  has  only  20,000  (in  spite  of 
Government  awards  of  £100,000 
annually  to  encourage  its  growing), 
about  800,000  quintals  being  im- 
ported (four-fifths  from  Russia)  to 
supply  its  700,000  spindles,  20,000 
hand  looms,  and  22,000  power  looms. 
Italy  has  not  more  than  50,000 

hectares  under  flax,  and  for  the  manufacture  of  fine  fabrics  imports  annually  about  40,000 

quintals  of  fine  or  semi-fine  flax  and  about  1400  quintals  of  undressed  flax. 

The  flax  fibre  has  a  diameter  of  0-02  mm.  and  is  readily  distinguishable  under  the 

microscope  from  other  vegetable  fibres  (Fig.  431  :    1,  spiral  stria- 

tion  ;  2,  extremity  of  the  fibre  and  polygonal  section  ;   3,  bruised 

places).     The   fibre  is  spun  into  yarn   in  the  same  way  as  with 

cotton,  but  special   machines   are   used    for    the    recombing    and 

repreparing   of   coarse   fibres,  which  are  drawn  out  in  the    moist 

state  to  a  finer  thread,  and,  at  a  certain  stage,  twisted.     The  tow 

from  these  operations  is  worked  up  by  carding  (see  Shoddy).     Flax 

can  be  spun  by  hand  to  a  count  of  300,  but  by  machinery  only  to 

200  ;  certain  qualities  of  flax  can  be  hand-spun,  for  very  fine  work, 

to  a  count  of  1400,  such  yarn  costing  as  much  as  £80  per  kilo. 

HEMP  (Cannabis  saliva)  belongs  to  the  order  Cannabineae  and 

bears    male    and    female   flowers    on  different    plants  (dioecious). 

When  growing  wild  it  branches  (Fig.  432),  but  when    cultivated 

for  industrial  purposes  it  grows  to  a  height  of  2    metres  or  more 

without  branching  and  has  a  finer  and  closer  tuft  in  the  case  of 

the  female  plants  (Fig.  433).     Of  the  different   varieties  of  hemp 

(jute,  Manila,   New  Zealand,    and  ordinary),  the   most   important 

is  the  ordinary.      It  is  sown  very  close  in  heavy,  deeply  worked 

soil,  and  is  gathered  in  August,  the   plants   being  dried  in  bundles  on  the  ground.     The 

treatment  is  similar  to  that  of  flax,  but  with  a  more  protracted  maceration.     The  residue 

from  the  breaking  is  used  to  some  extent  in  paper-making  ;  the  hemp,  more  or  less  combed, 

is  twisted  into  tresses  like  flax  and  made  up  into  bales  of  150  kilos.     Hemp  fibres  have  a 


Fro.  431. 

iiiflrd  200  times) 


J  IT  T  E 


689 


diameter  of  0-04-0-05  mm.  and  are  easily  distinguished  microscopically  rom  other  fibres 
(Fig.  435 :  1,  displaced  fibres  ;  2,  a-d,  form  of  the  tip  of  the  fibre  ;  3,  section  of  a  bundle 
of  fibres  ;  4,  striation :  the  crossed  transverse  lines  are  not  always  seen,  the  parallel 


FIG.  432. 


FIG. 433. 


FIG.  434. 


longitudinal  striations  being  more  common).     The  long  stems  are  cut  into  three  lengths 

of  about  70  cm.  and  are  combed  first  by  hand  and  then  by  a  machine  with  long,  coarse 

points,  the  waste  forming  the  first  and  second  tow,  which  can  be  subsequently  carded. 

A  third  combing  is  carried  out  with  finer  and  closer  teeth,  the  coarse  and  then  the  finer 

ribbon  being  passed  through  machines  similar 

to  but  coarser  than  those  used  for  cotton  and 

wool  (preparing),  and  finally  twisted  for  coarse 

twine  yarn,  for  canvas  yarn  (count  of  7  to  10), 

&c.     Two  twines  twisted  together  give  a  string, 

several   strings  combined  and  twisted  form   a 

rope,  and  several  ropes  a  cable. 

As  well  as  for  string,  rope,  &c.,  hemp  is 
largely  used  for  making  coarse-,  strong  cloth 
for  bags,  waggon  covers,  sails,  &c.  In  order  to 
render  hemp  fabrics  more  compact  and  durable, 
they  are  sometimes  mercerised. 

The  output  of  hemp  in  Europe  is  less  than 
4,000,000  quintals,  1,000,000  coming  from 
Russia,  960,000  from  Italy,  750,000  from 
Austria-Hungary,  600,000  from  France,  20,000 
from  Belgium,  and  10,000  from  Holland.  Italy 
exports  nearly  40,000  quintals  of  string  and  TIG.  435. 

rope,  35,000  of  rough  hemp  and  flax,  and  1200  (Magnified  200  times) 

of  twisted  hemp  and  flax. 

JUTE  (Corchorus  capsularis  of  the  order  Tiliacese)  has  been  grown  on  an  enormous 

scale  in  India  and  Bengal  from  time  immemorial  and  is  now  replacing  indigo.     Even  in 

1851  India  exported  282,350  quintals,  and  in  1858  the  exports  of  jute  sacks  were  valued 

at  almost  £240,000.     These  figures  are  now  nearly  doubled,  owing  to  the  development 

n  44 


690 


ORGANIC    CHEMIST  R  Y 


of  the  large  works  in  Calcutta.     In  Europe  its  cultivation  was  commenced  subseqxiently 
to  1830.     It  is  grown  also  in.  South  America  and  in  the  United  States. 

Jute  requires  a  moist,  hot  climate  and  soil.     It  is  sown  in  spring,  and  the  plants,  15 
to  20  cm.  apart,  mature  in  four  months  and  attain  a  height  of  3  to  4  metres.     The  shape 

of  the  leaves,  stem,  seeds,  &c.,  is  shown  in  Pig.  436. 
It  is  treated  in  a  similar  manner  to  hemp,  and  the 
bales,  weighing  180  kilos,  are  tightly  pressed  for 
transport.  The  principal  European,  centre  of  the 
jute  trade  and  industry  is  at  Dundee.  The  jute 
fibre  is  brownish  yellow,  and  is  bleached  in  a 
faintly  alkaline  chloride  of  lime  bath  (5°  Be.)  at 
25°  to  30°,  then  rinsed,  immersed  in  a  0-5  per 
cent,  sulphuric  acid  bath  for  15  minutes,  and 
finally  thoroughly  washed. 

Raw  jute  fibres  are  easily  distinguished  from 
other  fibres  under  the  microscope  (see  Fig.  437  : 
1,  irregular  lumen  of  the  fibre  dotted  at  the  top  ; 
2-,  fibre  with  broken  lumen  ;  3,  tip  of  fibres  ;  4  and 
5,  sections  of  fibre  with  thin  or  thick  walls)  and 
show  more  or  less  lustre  according  to  their  fine- 
ness. 

Jute  competes  directly  Avith  hemp  since  it 
serves  for  making  the  same  articles  (sacks,  packing 
cloth,  carpets,  tents,  furniture  coverings,  &c.),  but 
when  made  of  jute  these  cannot  be  washed. 

In  1901  Italy  imported  249,000  quintals  of  raw 
jute  to  be  manufactured  and  4000  of  jute  yarn 
(some  again  exported),  and  exported  about  15,000 
quintals  of  jute  tissue  (jute,  flax,  and  hemp  fabrics 
are  highly  protected  in  Italy,  the  duty  ranging 
from  8s.  to  16s.  or  even  more  for  the  finer  counts 
and  for  tissues). 

The  consumption  of  jute  in  different  countries 
is  as  follows:  England,  1.280,000  bales  (of  180 
kilos)  ;  India,  1,200,000  ;  United  States,  540,000  ;  Ger- 
many, 450,000 ;  France,  260,000  ;  Austria-Hungary, 
170,000  ;  Italy,  120,000  ;  Belgium,  100,000,  &c.  Raw 
jute  in  bales  costs  28s.  to  36s.  per  quintal. 

SILK.  The  Chinese  seem  to  have  known  the  silk- 
worm as  early  as  2600  years  B.C.  Although  they 
understood  the  preparation  of  silk  materials,  they  did 
not  at  once  trade  with  other  races,  but  maintained 
great  secrecy  on  the  rearing  of  silkworms  and  strictly 
prohibited  the  exportation  of  the  eggs. 

According  to  tradition  it  was  only  in  150  B.C.  that 
silkworms  arrived  in  Japan,  where  they  were  imported 
secretly  by  the  daughter  of  a  Chinese  emperor,  and 
whence  they  spread  later  throughout  the  rest  of  Asia. 
They  were  apparently  imported  into  Italy  in  the  sixth 
century  by  three  monks  who  hid  them  in  their  staves, 
although  the  manufacture  of  imported  silk  was  begun 
in  Italy  three  centuries  earlier.  From  that  time  up  to 
the  present  Italy  has  maintained  the  first  place  among  the  countries  of  Europe  for  tin- 
rearing  of  silkworms  and  the  production  of  silk.1  \ 

1  Silk  is  produced  by  one  of  the  Lepidoptera,  Bombyx  mori,  a  larva  which  after  birth  (when  it  weighs 
about  0-5  mgrm.),  feeds  on  mulberry  leaves  (Moms  alba)  and  atta.ns  the  height  of  its  development  (with  a 
weight  of  3  to  5  grins.)  in  five  weeks,  passing  through  four  moults  or  sleeps  during  which  it  casts  its  skin.  It 
finally  passes  to  brushwood  arranged  above,  where  it  constructs  a  cocoon  with  the  silky  exudation  secreted  by  two 
long  glands  tilled  with  fibroin  and  leading  along  the  body  beside  the  intestinal  canal  to  two  very  fine  apertures  in 
the  mouth.  The  two  contiguous  and  parallel  threads  thus  formed  are  immediately  stuck  together  by  a  liquid 
(sericin)  exuded  by  two  other  channels  near  the  first  pair,  the  result  being  an  apparently  single  thread,  which  is 


Fic.436. 


f  -•• 


FIG.  437. 

(Magnified  200  times) 


S  I  L  K  W  O  R  M    C  U  L  T  U  R  E 


601 


In  144;}  Florence  contained  84  large  silk  factories  and  in  1580  Milan  began  to  acquire 
the  ascendancy,  but  fell  back  later,  to  advance  again  in  the  middle  of  the  nineteenth 

either  white  or  some  shade  of  yellow  (the  double  thread  is  shown  in  Fig.  438).  In  three  days  the  silkworm  is  trans- 
formed into  a  chrysalis  from  which  the  butterfly  originates  (in  10  to  14  days)  if  the  temperature  ia  sufficiently 
high  (15°  to  30°).  The  butterfly  emits  from  its  month  an  alkaline  liquid  with  which  it  moistens  one  end  of 
the  cocoon  and  then  perforates  it  and  issues  to  proceed  to  the  coupling  necessary  for  the  preservation  of  the 
species. 

Immediately  aff  pnvards  the  female  di'ixisits  numerous  fertile  eggs  (qraine),  and  both  it  and  also  the  male  die, 
( heir  short  life-cycle  being  at  an  end  (Fig.  439).  One  kilo  of  cocoons  gives  three  ounces  of  eggs.  Part  of  tho 
eggs  (or  of  the  butterflies)  are  selected  under  the  microscope  and  are  kept  in  a.  cool  place  until  the  following  spring, 
when  they  are  hatched  by  incubating  for  a  couple  of  weeks  in  an  oven,  the  young  worms  being  distributed  to 
the  rearing-houses.  In  1904  Italy  exported  1521  kilos  of  eggs,  of  the  value  of  £20,240 ;  in  1908  9228  kilos  ;  in 
1909  2885  kilos,  and  in  1910  3330  kilos,  worth  £40,000.  The  imports  of  graine  (from  France)  were  4178  kilos 
in  1906,  18,928  in  1908,  13,629  in  1909,  and  5612,  worth  £44,880,  in  1910. 

By  moans  of  extreme  cleanliness,  disinfection  of  the  brushwood  and  microscopic  tests  of  the  eggs,  the  numerous 
diseases  which  cause  havoc  among  silkworms  at  all  stages  (calcino,  flacherie,  <frc.)  have  been  partially  overcome. 
The  crossing  of  different  varieties  has  also  proved  beneficial,  and  in  Lombardy  the  use  of  the  Chinese  cross  is  fairly 
general.  The  silkworms  from  an  ounce  of  eggs  consume  altogether  about  12  quintals  of  leaves.  It  has  been 
proposed  to  disinfect  the  leaves  with  lysoform,  tachyol  (ozone  :  Molinari,  1908),  &c.,  but  without  good  results. 

In  order  that  a  maximum  yield  of  good  silk  may  bo  obtained,  the  butterfly  is  not  allowed  to  issue  from  the 
cocoon,  since  the  silk  cannot  subsequently  be  readily  unwound  from  perforated  cocoons  and  much  waste  is  pro- 
duced ;  indeed  when  the  cocoons  are  placed  in  water  (see  later),  the  perforated  ones  become  filled  with  water 


FIG.  438. — «,  double  thread  (bam)  with 
scales,  d;    b,  section  of  double  thread; 
c,  isolated,  smooth  bava,  after  cleansing. 
(Magnified  120-180  times) 


FIG.  439. 


and  sink,  thus  breaking  the  thread  during  the  unwinding.  The  formation  of  the  butterfly  in  the  cocoon  is  prevented 
by  stifling  (i.e.  killing)  the  chrysalis  by  heating  in  an  oven,  where  the  cocoon  loses  two-thirds  of  its  weight.  Such 
procedure  also  allows  of  the  sale  of  the  cocoons  at  the  season  of  the  year  when  the  prices  are  most  remunerative. 
Ten  or  eleven  kilos  of  fresh  cocoons  yield  4  kilos  of  dry  cocoons,  and  these  give  1  kilo  of  silk. 

In  Japan  silkworms  are  raised  as  many  as  three  times  a  year.  An  ounce  of  eggs  yields  50  to  60  kilos  of  cocoons, 
which  are  sold,  freed  from  waste,  at  prices  varying  in  different  years  from  2s.  to  3s.  6rf.  per  kilo  ;  as  waste  arc 
considered  doubled  cocoons  (doupions).  stained  or  mouldy  cocoons,  those  attacked  by  calcino,  and  also  incomplete, 
light,  soft  cocoons,  and  the  flake  silk  or  cover  which  surrounds  the  cocoons  and  attaches  them  to  the  brushwood. 

The  suffocated  cocoons  have  an  average  weight  which  varies,  more  particularly  with  the  variety,  from  0-5  to 
0-8  grm.  The  ratio  between  the  weight  of  dead  chrysalis  and  silk  lies  between  1-4  :  1  and  1-6  :  1  and  the  length  of 
silk  per  gramme  is  900  to  1500  metres  ;  the  thread  (bava)  varies  in  thickness  from  0-18  to  0-30  mm. 

The  cocoons  are  first  placed,  a  few  at  a  time,  in  basins  of  almost  boiling  water  and  are  rubbed  with  a  hancl- 
hrush  of  twigs,  to  which  the  tangled  filaments  covering  the  cocoons  become  attached.  Among  these  filaments  is 
that  by  which  the  cocoon  can  be  completely  unwound.  The  other  filaments  form  the  floss,  which  is  worked  up 
with  the  other  waste  (see  nbore).  Five  (or  more)  of  the.  threads  are  attached  to  a  reel,  which  revolves  rapidly  and 
completely  unwinds  the  cocoons.  The  latter  float  in  hot  water,  which  softens  and  dissolves  part  of  the  gum 
uniting  trio  threads,  while  the  remainder  of  the  gum  drys  again  on  the  reeled  silk,  joining  the  five  threads  to  a  single 
filament  constituting  raw  silk.  As  one  cocoon  is  finished,  it  is  replaced  immediately  by  another  so  as  to  form 
a  homogeneous  thread.  The  chrysalides  remaining  form  about  70  per  cent,  of  the  weight  of  the  fresh  cocoons 
:m.l  contain  22  to  26  per  cent,  of  oil  (fetid) ;  they  are  generally  defatted  and  sold  as  nitrogenous  fertiliser  (for 
hemp,  &c.)  at  13s.  or  14s.  per  quintal.  Cocoons  which  do  not  unwind  regularly  also  pass  into  the  waste. 

Good  cocoons  give  as  much  as  800  metres  of  good  silk  and  the  count  of  the  single  thread  varies  from  1-5  to 
4  denari  according  to  the  breed  of  silkworm  ;  the  tenacity  lies  between  5  and  12  grms.  and  the  elasticity  between 
80  and  150  mm. 

White  or  greenish  yellow  cocoons  give  white  or  almost  white  (Chinese)  silk  and  the  yellow  ones  golden-yellow 
silk.  The  following  types  of  silk  are  distinguished  commercially  :  European,  Japanese,  Chinese,  Canton,  Bengal, 
titssah  (Chinese  wild  silk),  and  Indian  tussah,  and  of  each  of  these  there  are  various  qualities. 

Jn  the  raw  silk  trade  the  variations  of  the  count  are  indicated  ;   thus,  first-quality  silk  from  8  to  10  denari 


092  O  R  G  A  N  1  ('    C  II  E  M  I  S  T  R  Y 

century.  In  1804  Como  had  only  920  looms,  which  incrca-scd  lo  JSOO  in  I  ,S.r>8,  while  Lyons 
possessed  10,000  looms  as  early  as  1685,  40,000  in  1834,  and  05,000  in  1852  (present  con- 
ditions are  indicated  later). 

Raw  silk  consists  of  60  to  70  per  cent,  of  Fibroin  (the  fundamental  constituent 
of  pure  silk)  and  25  to  35  per  cent,  of  Sericin,  which  is  the  <rum  surrounding  the 
threads  and  holding  them  together,  and  can  be  easily  eliminated  with  hot  water 
and  soap  or,  partially,  with  hot  water  alone. 

Various  formulae  have  been  attributed  to  fibroin  :  (J15H20()(("N5  (Schiitzcn- 
berger),  C71H107O25N24  (Bourgeois,  1875).  From  the  chemico-tintorial  point 
of  view,  silk  has  the  character  of  an  ammo-acid  (or  of  the  corresponding  internal 
anhydride),  but  its  acid  nature  is  more  marked  than  that  of  wool.  The;  decom- 
position of  fibroin  by  means  of  hydrochloric  acid  gives  glycocoll,  aminopro- 
pionic  acid,  tyrosine,  1-leucine,  and  other  amino-acids  (E.  Fischer). 

The  formula  C18H15O8N5  is  ascribed  to  Sericin,  which  closely  resembles 
fibroin,  but  gives  large  proportions  of  diamino-acids.  It  is  thought  by  some 
that  the  silkworm  contains  only  fibroin,  and  -that  at  the  moment  when  the 
thread  is  produced  this  is  transformed  superficially  into  sericin  under  the 
influence  of  air  and  moisture.  The  yellow  colour  of  certain  raw  silk  is  due 
to  a  natural  colouring-matter.  Carotin  (Dubois'  hydrocarbon). 

Under  the  microscope  raw  silk  has  the  appearance  of  slightly  flattened, 
cylindrical,  transparent  threads,  not  very  smooth  on  the  surface,  and  composed 
of  two  bave  joined  by  the  sericin  (which  can  be  distinguished  from  the  inner 
part  or  fibroin)  and  thinly  covered  with  an  adhesive  soluble  in  hot  water 
and  different  from  sericin,  which  dissolves  only  in  hot  soap  solution. 

In  many  cases  the  Dyeing  of  silk,  especially  with  mordant  dyestuffs,  is  similar  to  that 
of  wool.  Under  all  circumstances,  however,  the  silk  should  be  thoroughly  cleaned  before 
dyeing,  and  as  in  spinning  and  weaving  the  silk  is  treated  with  dressing  (soap  emulsion, 
vaseline  oil  emulsion,  soluble  starch,  &c.)  to  facilitate  the  operations  and  sometimes  also 
to  increase  the  weight,  both  yarns  and  fabrics  (even  if  white)  are  subjected  to  rapid  cleansing 

is  marked  -,"«•  first-grade  tussah  of  40  to  45  denari.  }V,  <tc.).  The  price  of  tussah  silk  (16s.  to  24s.  per  kilo) 
is  less  than  half  that  of  fine  European  silk,  but  the  prices  vary  from  year  to  year. 

With  Asiatic  silk  it  is  always  stated  whether  spun  in  Europe  or  on  the  spot ;  the  latter  gives  much  more  waste 
in  the  subsequent  operations. 

Haw  si!k  threads  are  seldom  made  into  textiles  (then  called  raw  silk)  and  real  silk  thread  is  obtained  by  joining 
two  or  more  threads  of  raw  silk  and  twisting  them  to  form  the  tram  silk  or  oraansine  (warp)  used  in  weaving. 

To  this  end  the  raw  silk  is  first  wound  on  bobbins,  from  which  it  passes  through  felted  forks — to  free  it  from 
down — to  other  bobbins.  It  is  then  ready  for  twisting,  which  is  carried  out  in  different  ways  for  tram  silk  and  for 
mirp  (organsine).  For  the  latter  the  best  silks  are  used,  these  being  at  once  twisted  from  right  to  left,  the  product 
being  known  under  different  names  according  as  the  number  of  the  twists  per  metre  are  244  to  440,  440  to  488, 
or  488  to  610.  The  twisted  threads  are  then  joined  in  twos,  threes,  or  fours,  the  combined  threads  being  twisted 
from  left  to  right  (or  rice  versa) — 380  to  450  twists  per  metre  for  taffeta,  320  to  360  for  satin,  550  to  560  for  velvet, 
and  2200  to  3000  for  Chinese  crape.  Before  dyeing  or  bleaching  the  raw  organsine  is  ungmnmed  or  stripped  for 
about  30  minutes  in  boiling  neutral  soap  solution  (25  to  30  per  cent,  of  soap  calculated  on  the  silk).  In  order  to 
remove  the  gum  and  to  obtain  a  maximum  lustre,  a  second  boiling  soap  bath  is  used,  and  finally  a  third.  The, 
boiled  silk  weighs  about  25  per  cent. less  than  the  original  organsine.  When  the  organsine  is  to  be  dyed  a  pale  or 
delicate  colour,  it  is  subjected  to  special  treatment  with  sulphur  or  hydrogen  peroxide  (see  vol.  i.  p.  235) ;  tussah 
organsine  (brownish)  is  only  bleached  with  hydrogen  peroxide. 

In  preparing  tram  silk  the  raw  threads  are  not  immediately  twisted,  but  are  first  joined  in  fives  or  tens  (or  more) 
and  then  twisted,  but  only  with  80  to  125  twists  per  metre.  The  cleansing  with  soap  is  carried  out  at  35°  and  the 
colouring-matter  is  readily  destroyed  by  immersion  for  15  minutes  in  an  aqua  regia  bath  (2-5°  to  3°  Be.)  at  20° 
to  25°,  and  thorough  washing  with  water.  The  white  tram  (so-called  souple)  has  lost  in  these  operations  only 
5  per  cent,  of  its  weight ;  if  it  is  to  be  dyed  a  pale  tint  it  is  then  sulphured.  When  a  more  lustrous  tram  is  required 
for  obtaining  special  effects  in  textile  design,  it  is  subjected  to  boiling  like  the  organsine. 

Silk  Waste,  including  doiipions  (cocoons  formed  by  two  larva1  in  the  same  covering  ;  these  cannot  be  unwound 
in  the  ordinary  way),  pierced  cocoons,  the  waste  from  twisting  (2-5  per  cent,  in  Italian  and  8  per  cent,  in  Asiatic 
silks),  stained  (mouldy)  cocoons,  diseased  cocoons,  small  or  incomplete  cocoons  (from  inert  worms),  silk  tow,  <fcc., 
constitutes  25  to  35  per  cent,  of  the  total  crop  of  cocoons  and  often  goes  under  the  name  of  floss  (at  4*.  to  6s.  per 
kilo  :  real  floss  costs  6s.  to  7s.  per  kilo).  It  is  worked  very  similarly  to  cotton  and  to  woollen  rags  by  means  of 
special  carding  and  combing  machines,  giving  first  a  kind  of  wadding  and  then  ribbons  and  threads  with  parallel 
fibres.  These  can  be  converted  into  yarn  called  chappe,  which  is  consumed  in  large  quantities  as  it  costs  less  than 
one-half  as  much  as  pure  silk  and  for  some  fabrics  (velvets)  is  a  good  substitute  for  ordinary  silk.  The  waste  from 
the  carding  and  combing  of  chappe  is  also  spun,  giving  bourettes.  In  Italy  a  large  company  with  seven  works 
enjoys  a  kind  of  monopoly  in  this  trade  :  they  work  up  foreign  waste  and  part  of  the  native  waste,  the  Italian 
Government  imposing  a  small  export  duty  which  acts  detrimentally  against  the  spinners  and  forms  a  protective 
duty  on  foreign  waste  yarn. 

The  value  of  the  raw  waste  worked  uii  in  Italy  is  about  £1,000,000,  its  subsequent  value  being  about  £1,600,000 
(sec  also  Statistics). 


WEIGHTING    OF    SILK  G0r> 

with  hot  soap  solution  (80°  to  85°)  containing  a  little  sodium  carbonate,  and  are  then 
well  rinsed  in  tepid  water.1  If  the  wares  are  to  remain  white,  they  are  sulphured  (see 
Note)  or  treated  with  hydrogen  peroxide  solution,  the  characteristic  rustle  (scroop  or 
crackle)  of  silk  being  imparted  by  immersion  in  a  1  to  2  per  cent,  sulphuric  or  acetic  acid 
bath,  centrifugation  and  drying  without  rinsing. 

Dyeing  is  in  general  carried  out  in  soap  baths,  using  one-third  or  one-fourth  of  the 
soap  solution  remaining  after  the  boiling  of  the  raw  silk,  acidifying  it  with  sulphuric  acid, 
boiling  and  agitating.  The  silk  is  immersed  in  this  emulsion  for  a  time  and  then  removed, 
the  bath  being  diluted  with  water  and  the  colouring -matter  (acid  or  basic)  ;  the  dyeing 
is  begun  at  35°  to  40°,  the  temperature  being  gradually  raised  almost  to  the  boiling-point. 
Acid  colouring-matters  are  fixed  by  silk  also  from  a  hot  acidified  aqueous  solution,  but  the 
tints  are  not  so  lasting. 

The  dyed  silk  is  rinsed  in  water  and  transferred  to  the  acid  bath  to  obtain  the  crackle, 
which  becomes  more  pronounced  as  the  acidity  and  temperature  of  the  bath  are  raised, 
but  the  acid  remaining  in  the  dry  fibre  slowly  attacks  it,  with  injury  to  its  tenacity  and 
elasticity. 

Nowadays  silk  is  usually  weighted,  i.e.  impregnated  with  various  substances  (organic 
and  inorganic),  in  order  to  increase  its  weight  (by  30  to  40  per  cent,  and  sometimes,  with 
black  silk,  even  by  300  per  cent,  or  more).  Silk  possesses,  indeed,  the  property  of  absorbing 
from  solution  large  quantities  of  tannin  ;  this  can  be  fixed  by  means  of  salts,  and  fresh 
tannin  can  then  be  absorbed,  and  so  on.  Successive  amounts  of  insoluble  metallic  salts 
(tin  salts,  phosphates,  silicates,  &c.)  may  also  be  precipitated  on  silk.  To  weight  white 
silk,  the  boiled  silk  is  soaked  for  an  hour  in  a  stannic  chloride  bath  of  25°  to  30°  Be.  [at 
one  time  pink  salt,  SnCl4,2NH4Cl  (see  vol.  i,  p.  609)  was  largely  used,  but  at  the  present 
time,  crystallised  tin  salt,  SnCl4,5H2O,  is  mostly  employed],  manipulated  for  30  to  40 
minutes  in  a  hot  disodium  phosphate  bath  (4°  to  5°  Be.),  washed  slightly  with  water, 
introduced  into  a  sodium  silicate  bath  (3°  to  4°  Be. )  and  again  washed.  Treatment  with  this 
series  of  baths  (stannic  chloride,  phosphate,  and  silicate)  is  repeated  several  times,  according 
to  the  degree  of  weighting  desired  ;  five  such  repetitions  give  a  weighting  of  100  to  120  per 
cent,  (the  weight  being  doubled).2  Weighted  silk  can  be  dyed,  and  in  the  preparation 

1  It  is  generally  necessary  to  ascertain,  before  dyeing,  what  will  be  the  loss  in  weight  of  the  silk  during  ungum- 
ming  or  stripping.     White  Italian  silk  loses  on  an  average  21-5  per  cent. ;  Japanese,  20  per  cent.  ;    Canton  and 
Chinese,  24  per  cent. ;  raw  yellow  Italian,  24  per  cent. ;  and  cliappe,  4  per  cent.     The  loss,  which  includes  also  any 
weighting  of  the  yarn  with  vaseline,  soap,  oils,  glycerine,  &c.,  is  determined  as  follows  :  50  grms.  of  the  silk  are 
manipulated  in  a  solution  of  15  grms.  of  seasoned  Marseilles  soap  of  good  quality  in  a  litre  of  hot  water,  which  is 
allowed  to  boil  gently  for  half  an  hour,  and  are  then  removed,  pressed  or  centrifuged,  boiled  for  a  further  period 
of  30  minutes  in  a  soap  bath  similar  to  the  first,  and  washed  thoroughly  with  water  until  the  latter  remains  clear  ; 
after  being  centrifuged,  the  silk  is  dried  in  an  oven  until  of  constant  weight.    The  loss  of  weight  on  stripping  is 
referred  to  100  grms.  of  dry  silk,  so  that  allowance  should  be  made  for  the  normal  humidity  (11  per  cent.)  of 
silk. 

2  The  phenomenon  of  iveighting  is  explained,  according  to  Sisley  (1911),  by  regarding  silk  as  a  colloid  (see  vol.  i, 
p.  102),  which  absorbs  hydrogels  (e.g.  stannic)  of  various  salts  of  polybasic  acids.     But  many  substances  which 
give  precipitates  and  insoluble  salts  do  not  serve  for  weighting,  since  they  are  not  firmly  retained  by  the  silk  fibre 
• — and  are  therefore  eliminated  during  washing  and  dyeing — and  are  not  dyed.     The  weightings  which  have 
given  the  best  results  in  practice  are  :    (1)  tin  hydroxide  (used  as  early  as  1869  in  a  Lyons  dyeworks) ;    (2)  tin 
phosphate  ;  (3)  tin  silicophosphate  ;  (4)  tin  and  aluminium  silicophosphates.     Sisley  (1896)  showed,  and  Franckel 
and  Fasal  (1897)  and  Sevcrini  (1906)  confirmed,  that  weighting  is  due  purely  to  a  physical  and  not  to  a  chemical 
phenomenon,  since  the  weighting  bath  undergoes  no  chemical  change  and  no  alteration  in  concentration.    Further, 
when  silk  soaked  in  stannic  chloride  is  washed  with  water,  the  precipitated  stannic  hydroxide  which  is  formed  in 
abundance  as  a  result  of  hydrolysis  is  not  fixed  by  the  silk  and  is  derived  from  the  chloride  on  the  surface  of  the 
thread,  that  absorbed  inside  the  fibre  remaining  as  a  kind  of  colloidal  solution  of  stannic  hydroxide  in  hydrochloric 
acid  ;  the  acid  diffuses  into  the  fibre,  which  retains  it,  whilst  the  stannic  hydroxide  is  fixed  as  a  gel  and  does  not 
influence  the  feel  and  lustre  of  the  silk.     The  absorption  of  stannic  chloride  is  avoided  if  the  silk  is  previously 
treated  with  tannin.     In  12  hours  silk  which  has  absorbed  II  per  cent,  of  tannin  fixes  from  a  stannic  chloride 
bath  of  30°  B6.,  only  1-25  per  cent,  of  SnO2,  while  silk  without  tannin  fixes  about  12  per  cent,  of  SnO2  from  the 
same  bath  ;   these  different  silks  also  take  up  varying  quantities  of  colouring-matters.     When  washed,  the  stannic 
hydroxide  formed  on  the  fibre  is  Sn(OH)4  or  ,Sn<V2H.,O,  retaining  small  amounts  of  HC1  ;  the  washed  silk  is  there- 
fore introduced  into  a  bath  of  sodium  carbonate,  which  forms  a  labile  compound  of  Na2CO3  and  SnO,,2H2O,  this 
being  decomposed  by  acid  with  formation  of  a  tin  hydroxide  insoluble  in  acid  and  in  subsequent  stannic  chloride 
baths. 

Boiling  or  treatment  witli  a  soap  bath  of  washed  silk  containing  SnO2.2H2O  results  in  the  separation,  in  a  firmly 
fixed  condition,  of  the  hydrate  Sn4O2,H2O,  i.e.  Sn4O(OH)2.  which  has,  however,  but  little  affinity  for  phosphates 
and  silicates  (Gianoli.  1907).  Weighting  with  stannic  chloride  gives  a  regular  increase  of  10  to  12  per  cent,  in 
t  he  weight  for  each  separate  operation  on  the  same  silk.  In  weighting  with  tin  phosphate  (after  the  chloride  bath, 
the  silk  is  passed  into  a  hot  disodium  phosphate  bath  and  then  washed  thoroughly  with  water,  the  operation  being 
repeated  if  necessary),  the  tlrst  operation  gives  an  increase  of  about  20  per  cent.,  but  subsequent  operations  produce 
larger  increases  ;  the  third  may  «ive  as  much  as  :'.5  per  cent.  Silk  alone  has  no  affinity  for  salts  of  polybasic 
acids  (phosphoric,  tuiiL'slic,  &c  ),  but  if  it  is  first  passed  into  a  tin  salt  bath  it  fixes  them,  for  example,  as 
SnO2,XajW<)4  or  Snu..Na,lll'04  (sodium  phosphostamiatc.  insoluble  in  water  but  soluble  in  concentrated  sodium 
phosphate  solution);  only  pho-pbat.'s  containing  hydroxyl  groups  are  fixed  by  tin,  so  that  trisodiimi  phosphate 


Fia.  440. 


ORGANIC    CHEMISTRY 

of  black  silk,  the  weighting  may  be  increased  considerably  by  passing  the  weighted  white 
silk  (washed  with  a  little  soda)  into  a  cold  bath  of  ferrugine  (a  slightly  acid  solution  of 
basic  ferric  sulphate  prepared  by  heating  a  solution  of  ferrous  sulphate  with  sulphuric 
and  nitric  acids),  slightly  washing  the  silk  thus  coated  with  oxide  of  iron  and  immersing 
it  in  a  bath  of  potassium  ferrocyanide  (acidified  with  HC1)  which  colours  it  blue.  It  is 
then  placed  in  an  almost  boiling  tannin  bath  (e.y.  chestnut  extract),  next  in  a  tin  bath  to 
fix  the  tannin,  and  finally  in  a  hot  bath  of  logwood  extract  to  obtain  an  intense  black  tint  ; 
the  dyed  silk  is  rinsed  in  soap  solution  or  an  acidified  oily  emulsion,  livened  in  a  sulphuric 
acid  bath,  centrifuged  and  dried.  By  repeating  the  tannin  and  metallic  baths  teri  or 
fifteen  times,  weighting  of  300  to  400  per  cent,  may  be  obtained.  Black  silk  weighted 
to  the  extent  of  400  per  cent,  and  partly  attacked  shows  under  the  microscope  a  heavy 
incrustation  round  the  fibre  (Fig.  440) ;  much  of  its  resistance  has  been  destroyed,  and  under 
the  action  of  sunlight  it  undergoes  rapid  corrosion  (umbrellas  of  heavily  weighted  black 
silk  split  even  without  using).  ().  Meister  at  Zurich  (1902)  and  independently  G.  Gianoli 

at  Milan  (1904  ;  Ger.  Put.  163.622)  found 
that  this  inconvenience  can  be  largely 
avoided  by  •  means  of  a  t  hiocyanate  bath. 
In  1906  the  Societa  della  stagionatura  della 
seta  di  Milano  (as  a  result  of  investigations 
of  Sisley  at  Lyons  and  of  Gianoli  and 
Colombo)  filed  a  patent  in  America  for  the 
preservation  of  weighted  silk  by  intro- 
ducing it  in  a  bath  of  thiourea  faintly 
acidified  with  citric  acid  ;  U.S.  Pat. 
873,902,  was  granted  in  February  1908, 
and  appears  to  give  excellent  results  in  practice.1  O.  Mcistcr  (1910)  suggests  the  use 

and  sodium  pyrophosphate  are  not  fixed.  If  the  sodium  carbonate  bath  follows  the  chloride  bath,  less  sodium  " 
phosphate  is  subsequently  fixed.  Treatment  of  the  silk  in  the  acid  bath  results  in  the  removal  of  the  whole  or  a 
good  part  of  the  sodium.  When  the  silk  lias  been  treated  in  the  first  sodium  phosphostannate  bath,  it  is  washed 
and  introduced  a  second  time  into  the  stannic  chloride  bath,  the  double  decomposition  thus  produced  resulting 
in  the  formation  of  insoluble  phosphate  of  tin,  which  is  fixed  on  the  fibre,  and  of  sodium  chloride,  which  passes 
into  the  bath,  while  at  the  same  time  the  silk  becomes  impregnated  anew  with  SnCl4 — this  fixing  tin  hydroxide 
on  the  fibre  when  the  latter  is  washed.  This  tin  hydroxide  gives  fresh  sodium  phosphostannate  when  introduced 
into  a  second  disodium  phosphate  bath,  while  the  bath,  which  becomes  impoverished  in  soda,  continually  increases 
iii  acidity  and  the  weighting  of  the  silk  increases  during  successive  operations. 

Still  higher  weighting  is  obtained  if  the  sodium  phosphostannate  silk  is  introduced  into  one  or  several  more  or 
less  concentrated  and  more  or  less  hot  sodium  silicate  baths.  By  this  means  part  of  the  phosphate  residue  united 
to  the  tin  oxide  is  replaced  by  silica,  the  compound  3SiO2,Xai,O,SnO2,  being  formed  ;  the  silicate  bath  becomes 
acid  and  contains  trisodium  phosphate.  In  the  acid  bath,  this  silk  readily  loses  sodium,  being  formed  of  insoluble 
tin  trisilicate.  This  weighting  was  patented  by  Neuhaus  in  1893,  but  had  been  previously  used  in  France. 

The  highest  weighting  of  silk  is  obtained  by  following  repeated  phosphate  baths  with  a  bath  of  an  alum  salt, 
as  was  proposed  by  Puller  (Crefeld)  (Fr.  Pat.  254,659  of  1906).  In  this  way  the  aluminium  is  fixed  as  phosphate 
and  a  little  sodium  passes  into  solution.  After  washing,  this  silk  is  passed  into  a  sodium  silicate  bath  and  has  the 
property  of  fixing  much  more  silica  than  in  the  case  described  by  Neuhaus  ;  further,  the  silk  loses  practically 
nothing  in  the  acid  bath,  since  the  sodium  of  the  tin  silicophosphate  has  been  replaced  by  aluminium.  Nicolle 
and  Sisley  (1911)  found  that  various  other  salts  may  be  used  in  place  of  those  of  aluminium,  but  that  only  those  of 
zinc  gave  good  results  in  practice. 

This  general  theory  of  Sisley  on  the  phenomenon  of  weighting  of  silk  is  not  universally  accepted.  P.  Heermann 
(1904-1911)  holds  that  while  the  silk  is  immersed  in  the  stannic  chloride  bath  the  latter  diminishes  in  concentration, 
and  part  of  the  tin  lemains  fixed  even  when  the  silk  is  washed  with  Avater  ;  he  also  regards  the  formulae  of  the  salts 
fixed  on  the  silk  as  different  from  those  given  by  Sisley. 

1  In  determining  the  weighting  of  silk  2  grnis.  are  boiled  for  two  hours  in  a  soap  bath  (30  grms.  soap  per  litre)  and 
1  lien  for  at  least  an  hour  (to  expel  the  ammonia)  in  a  sodium  carbonate  bath  at  1-5°  Be.,  the  water  evaporated  being 
gradually  replaced.  It,  is  then  rinsed  well  with  water  and  dried  and  the  nitrogen  in  0'6  to  0-8  grm.  determined 
(as  was  suggested  by  St.  Claire  Ueville  in  1878)  by  Kjeldahl's  method  (see  p.  10) ;  from  this  the  quantity  of  true 
fibroin  can  be  determined,  knowing  that  5-455  parts  of  fibroin  correspond  with  1  pait  of  nitrogen.  With  black 
silk  containing  cyanide  (Prussian  blue),  the  latter  must  be  previously  eliminated.  In  order  that  the  fibroin  may 
be  acted  on  as  little  as  possible,  P.  Sisley  (1907)  separates  it  as  follows:  2  grins,  of  the  fabric  are  boiled  for  10 
minutes  in  25  per  cent,  acetic  acid,  washed,  heated  for  10  minutes  at  50°  in  a  3  per  cent,  sodium  phosphate 
(JVa3PO4,12H.,O)  solution,  washed  again,  and  boiled  for  20  minutes  in  a  bath  containing  3  per  cent,  of  soap  and 
0-2  per  cent,  of  soda;  this  procedure  is  repeated,  the  tissue  being  washed  and  dried  and  its  nitrogen-content 
determined.  The  percentage  weighting  p  (the  increase  in  weight  of  the  original  silk)  is  given  by  j)  •=  100(3  —  c),c, 
where  g  indicates  the  weight  of  the  dyed  silk  while  e  represents  that  of  the  raw  silk  (i.e.  fibroin  +  sericin  +  11  per 
cent,  moisture)  or  fibroin  +  normal  loss  on  stripping  (21-5  or  24  per  cent. ;  see  preceding  Xote).  A  silk  is  said  to 
be  weighted  50  per  cent,  when  1000  grms.  of  raw  silk  give  1500  grms.  of  dyed  silk. 

During  recent  years,  another  simple  method  has  been  used  for  determining  the  ordinary  tin  silicophosphate 
weighting  :  2  grms.  of  weighted  silk  of  known  moisture  content  (e.g.  10  per  cent.)  are  treated  for  an  hour  in  a  plat  i- 
iiuin  dish  with  100  c.c.  of  a  cold  aqueous  2  per  cent,  hydrofluoric  acid  solution  ;  the  latter  is  poured  away  and 
another  100  c.c.  of  the  acid  added  and  left  in  contact  with  the  silk  for  an  hour.  The  silk  is  washed  seven  times 
with  successive  amounts  of  150  c.c.  of  water,  pressed,  anil  dried  at  100°  to  105°  until  of  constant  weight.  If  the 
latter  is  0-95,  then  2  grms.  of  moist  silk  =  1-8  grm.  dry  silk,  and  1-8  -  0-95  -.  0-85  (weighting).  So  that  if  the 


695 


of  formaldehyde  bisulphite  (1  to  5  per  cent,  bath)  to  check  this  corrosion,  while  Berg  and 
JanhofY  (15)1.1)  prefer  the.  use  of  hydroxylamine.  The  use  of  a  diastofor  bath  (see  p.  500) 
after  dyeing  has  also  been  proposed.  Silk  weighted  with  ZnCl2  is  preserved  in  a  thio- 
sulphate  bath  (Herzig,  1908). 

STATISTICS.  An  idea  of  the  importance  of  the  Italian  silk  industry  is  given  by  the 
tact,  that  silk  always  makes  up  more  than  one-third  of  the  value  of  the  total  exports: 
.U2,760,000  out  of  £41 ,040,000  in  1.81)4  ;  £20,800,000  of  £57,240,000  in  1899,  and  £24,680,000 
of  £(',9.240,000  in  1905. 

The  production  of  cocoons  in  Italy  during  the  past  ten  years — with  the  exception  of  the 
scarce  crop  of  about  45,000,000  kilos  in  1903— averages  55,000,000  to  60,000,000  of  kilos, 
weighed  alive  (from  1,200,000  ounces  of  silkworms)  ;  in  1908  the  crop  was  52,000,000, 
in  1909  50,000,000,  in  1910  44,000,000,  and  in  1911  about  39,000,000  of  kilos,  although  the 
inaccurate  official  statist  ies  gi ve  much  lower  values.  About  38  per  cent,  of  the  crop  is  yielded 
by  Lombardy,  19  per  cent,  by  Piedmont,  21  per  cent,  by  Venice,  7  per  cent,  by  Emilia, 
f»  per  cent,  by  Marches  and  Umbria,  5  per  cent,  by  Tuscany  and  Latium,  and  5  per  cent, 
by  Southern  Italy  and  the  Italian  Islands.  The  price  per  kilo  of  fresh  cocoons,  according 
to  returns  from  Milan,  has  shown  the  following  fluctuations,  depending  partly  on  the 
si/.e  of  the  crop  :  IS!»2,  33c/.  ;  1893,  38-5rf.  ;  1895,  29-fx/.  ;  1896-1898,  about  23d.  ;  1899, 
Il4d.  ;  1900-1902,  about  28</.  ;  1903,  36-5rf.  ;  1904,  24rf.  ;  1905-1906,32(7.;  1907,  39rf. 

In  Japan  two  or  three  crops  of  cocoons  arc  gathered  per  annum  (bivoltine  or  trivoUine 
worms),  59,000,000  kilos  in  the  spring,  13,250,000  in  summer,  and  nearly  20,000,000  in  the 
autumn.  The  production  of  cocoons  in  1909  was  900,000  kilos  in  Spain  and  8,546,536 
in  France  (same  in  1 5)08.  and  5,110,000  in  1911). 

Japan  also  produces  a  considerable  amount  of  green  wild  silk — of  Bombyx  yamamai, 
which  feeds  on  chestnut  and  oak  leaves  (the  wild  silkworm  of  India  eats  castor  oil  leaves). 

The  world's  production  of  nnr  xilk  (excluding  the  local  consumption  of  the  Far  East, 
this  being  valued  at  about  55,000  quintals  for  China  and  47,000  for  Japan,  in  1906,  and 
about  one-third  more  in  1907)  is  shown  in  quintals  by  the  following  Table  (the  value  of 
raw  Italian  silk  is  taken  as  32*\  to  36s.  per  kilo)  : 


Average  for  the  years 

Locality 

1881-1885 

1886-1890 

1891-1895 

1896-1900 

1901-1905 

1906 

1909 

Italy       .... 

27,600 

33,110 

44,280 

42,150 

43,260 

47,450 

42,500 

France    .... 

6,310 

6,920 

7,470 

6,500 

5.910 

6,050 

6,740 

Spain       .... 

860 

720 

860 

830 

800 

560 

800 

Austria-Hungary 

1,530 

2,650 

2,570 

2,720 

3,150 

3,420 

3,800 

Anatolia  (Brusa) 

1,400 

1,860 

2,650 

4,020 

5,180 

5,540 

^ 

Svria  and  Cyprus      .          i. 

2,350 

3,030 

4,000 

4,560 

4,870 

4,700 

-    15,700 

Salunica,  Adrmnople 

1,010 

1,340 

2,000 

1,620 

2,350 

2,570 

lialkan  States 

— 

— 

120 

470 

1,410 

1,850 

3,150 

(Jreece  and  Crete      .          .                I8 

21 

380 

410 

640 

750 

700 

Caucasia. 

— 

— 

2,760 

3,910 

4,550     I          5,400 

Turkestan         .          .          .           S.050 

94 

1,920 

1,680 

4,680 

6,280 

China,        exported        from 

Shanghai       .           .           .          24,480 

•27.  :.70 

40,300 

45,080 

42.270 

42,620 

China.  exported  from  Canton         8,940 

1,277 

13,730 

20,210 

21,280 

19,620 

157,200 

.hi  pan.  export  cd  from  Yoko- 

I 

hama   ....           '••'•""" 

80,500 

:;:!,oo<> 

34,590 

48,050 

50,020 

India,  exported   from    Cal- 

1 

cutta  and  Bombay          .           *>(mo 

4,380 

261 

2,930 

2,560 

325 

World's  total,  quintals       .          94,380          1  Hi.  000          1.V2.950 

170,530 

190,920 

209,130 

242.000 

raw  silk  is  calculated  to  lose  '24  per  cent,  on  stripping,  the  weighting  will  be  0-95  :  0-85  =  76  :  x  (76  is  the  percentage 
of  silk  remaining  after  stripping)  and  x  =»  68  •  hence  the  dyed  dry  silk  contains  76  parts  of  dry  stripped  silk  (or 
100  of  raw  silk)  and  08  of  weighting,  total  144.  The  silk  was  hence  weighted  44  per  cent.  Gianoli  and  Colomba 
(190.7)  showed,  however,  that  in  some  eases  when  metustannic  acid  is  formed  on  the  fibre,  e.g.  by  the  fixation  of 
1  in  salts  with  sodium  carbonate,  the  whole  of  the  weighting  is  not  eliminated  by  hydrofluoric  acid,  even  when  this 
is  followed  by  a  bath  of  I1C1.  A  more  certain  result  is  then  obtained  by  the  old  method  (see  abuce)  or  by  using 
Urst  soda  and  then  potassium  hydrogen  oxalate.  P.  Hermann  (1909)  proposes  to  modify  the  alternate  treatment 
with  hydrochloric  aeid  and  caustie  potash  (Kistenpart,  1908)  of  black  on  tin  salt  and  eatechu,  by  replacing  thu 
caustic  potash  with  a  solution  of  normal  caustic  potash  and  concentrated  glycerine  (28°  B6.)  in  equal  parts,  the 
latter  preserving  the  silk,  readily  dissolving  Prussian  blue  (by  treatment  for  an  hour  in  the  cold  or  10  minutes  at 
80*0,  but  leaving  the  oxide  and  tannate  of  iron  unchanged. 


696  ORGANIC    CHEMISTRY 

The  world's  production  was  18  millions  of  kilos  in  1903  ;  20-5  in  1904  ;  18-5  in  1905  ; 
21  in  1906  ;  22  in  1907  ;  24  in  1908;  and,  in  spite  of  diminished  European  production, 
24-2  in  1909  (15-7  from  the  Far  East,  3-1  from  the  Levant,  and  5-4  from  Europe). 

In  China  the  exportation  of  real  silk  tends  to  diminish,  but  that  of  wild  silk  (or  tussah) 
increases  ;  this  is  produced  by  Anterea  mylitta  and  is  readily  recognised  under  the  micro- 
scope (Fig.  441 ).  China  exported  1  .2(10,000  kilos  in  1900  ;  1 ,325,000  in  1903,  and  2,000,000 
in  1904. 

To  the  quantity  of  raw  silk  produced  in  Italy  from  home-grown  cocoons  must  be  added 
that  obtained  from  cocoons  imported  from  abroad,  viz.  3000  quintals  in  1893  ;  7320  in 
1898  ;  11,000  in  1903,  and  13,000  in  1906.  The  mean  annual  importation  from  1901  to 
1905  of  cocoons  (calculated  dry)  was  37,736  quintals  (46,000  in  1906)  with  a  mean  yield  of 
1  kilo  of  silk  per  4  kilos  of  dry  cocoons  (at  7*.  to  Qs.  M.  per  kilo)  or  per  11-5  kilos  of  fresh 
cocoons. 

To  the  60,000  quintals  of  raw  silk  yarn  produced  in  Italy  must  be  added  24,000  quintals 
of  silk  simply  treated  and  imported  from  the  Far  East  to  be  spun  and  twisted.  But  only 
about  10,000  quintals  are  woven  in  Italy,  the  rest  being  exported  (50,000  quintals  of  raw 
silk  and  39,000  of  twisted). 

It  is  estimated  that  in  1903  there  were  more  than  61,000  basins 
(against  54,000  in  1891) ;  about  95,000  operatives  for  treating  the  silk 
(100  basins  require  10  to  12  quintals  of  fuel  per  day);  more  than 
1,667,000  spindles  (against  1,500,000  in  1891)  with  54,000  workpeople  ; 
and  20,000  looms  (of  which  one-half  are  power-looms  running  at  100 
to  160  picks  per  minute,  and  the  remainder  hand-looms  at  50  to 
60  per  minute)  with  30,000  workpeople  (against  10,000  looms  in  1891), 
almost  all  of  these  being  in  the  province  of  Como  and  neighbouring 
districts.  Eighty  per  cent,  of  the  workpeople  are  women. 

The  Italian  weaving  industry  is  capable  of  considerable  extension, 
its  produce  being  valued  at  only  £3,200,000,  while  Switzerland1  (with 
35,000  looms)  produces  silk  fabrics  to  the  value  of  £5,600,000,  France  2 
(with  140,000  looms)  £19,600,000  ;    England  about   £13,600,000  (im- 
FIG.  441.  porting    £8,800,000)  with   87,000    looms,   and    about    the   same  for 

Germany.      If   Italy  were  to  weave  the    £8,000,000  worth  of    yarn 
which  it  exports,  the  value  would  be  increased  to  £16,000,000  (a  kilo  of  fabric  costs  about 
double  as  much  as  a  kilo  of  yarn)  while  200,000  more  workpeople  would  be  employed. 
Mention  has  been  made  of  the  silk  waste  industry  in  Italy  on  p.  692. 
During  the  past  twenty-five  years  the  silk-weaving  industry  has  become  of  considerable 

1  Switzerland  has  two  very  important  centres  at  Zurich  and  Basle,  where  the  output  of  silk  goods  is  continually 
increasing,  although  the  production  of  cocoons  is  gradually  diminishing.  In  the  canton  of  Tieino,  where  the  silk- 
worm is  reared,  the  cocoons  produced  have  diminished  from  187,500  kilos  in  1872  to  58,000  in  1904,  while  there 
lias  been  a  "Corresponding  increase  in  the  importation  of  raw  silk  from  China,  Japan,  and  Italy.  This  importation 
rose  from  514,400  kilos  in  1893  to  637,000  (worth  £960,000)  in  1902,  but  about  one-third  of  this,  after  being  twisted 
in  the  Swiss  factories,  is  exported  to  Germany,  Russia,  and  Italy.  In  the  canton  of  Zurich  alone  in  1900  there 
were  at  work  about  21,000  hand-looms  and  13,330  power-looms  for  silk  and  mixed  silk  fabrics. 

The  Swiss  exports  of  pure  silk  tissues  in  1893  were  966,700  kilos  (£2,506,100),  those  of  mixed  tissues  being  valued 
at  £580,000.  In  1903  the  exports  of  silk  fabrics  were  1,760,300  kilos,  worth  £3,780,000,  while  the  total  imports 
in  the  same  year  were  149,000  kilos  (£330,800)  of  silk  fabrics  and  also  mixed  fabrics  to  the  value  of  £112,000. 
One-half  of  the  exports  goes  to  England.  The  silk  ribbon  and  embroidery  industry  of  Switzerland  is  steadily 
advancing. 

Germany  is  a  large  importer  of  raw  silk  (about  3,000,000  kilos,  largely  Italian),  and,  besides  supplying  home 
demands,  exports  considerable  quantities  of  manufactured  goods  (see  Table  later). 

Russia  consumes  about  1,500,000  kilos  of  raw  silk  annually. 

a  None  the  less  interesting  is  the  condition  of  affairs  in  France,  although  the  production  of  fresh  cocoons  is  only 
8,000,000  kilos  (1905).  The  imports  of  raw  silk  are  calculated  to  be  about  9,000,000  kilos,  and  the  silk  industry 
(almost  entirely  concentrated  in  the  city  of  Lyons)  occupies  one  of  the  foremost  positions  among  French  industries. 
The  province  of  Lyons  contains  more  than  25,000  power-looms  for  silk-weaving,  in  addition  to  a  larger  number 
of  hand-looms.  In  order  to  reduce  the  importation  of  raw  silk  and  increase  that  of  cocoons,  and  so  encourage  the 
direct  spinning  of  the  latter,  the  French  Government  in  1892  offered  a  premium  of  £16  for  every  new  four-threaded 
basin  established,  but  the  results  did  not  come  up  to  expectations. 

While  in  1893  the  production  of  silk  goods  was  valued  at  £15,150,000,  in  1902  it  reached  £17,800,000.  The 
French  exportation  of  silk  wares  of  all  kinds  amounted  in  1896  to  4,220\000  kilos,  worth  about  £10,000,000,  while 
in  1904  it  rose  to  5,700,000  kilos,  of  the  value  of  £13,200,000  (including  about  £1,200,000  worth  despatched  by 
parcel  post). 

The  value  of  the  products  \yoven  in  Lyons  in  1904  was  £16,360,000.  in  1905  £15,640,000,  and  in  1906  £17,040,000. 
In  the  department  of  Saint-Ktienne  the  output  of  silk  ribbon  in  1906  was  valued  at  £3,760,000,  one-third  of  it 
for  export. 

The  French  home  consumption  of  silk  wares  is  about  4,000,000  kilos,  this  large  amount  helping  considerably 
to  maintain  the  silk  industry  in  an  active  condition. 


ITALIAN    SILK    INDUSTRY  697 

importance  in  the  United  States,  where  raw  silk  is  almost  free  from  customs  duty,  while 
the  manufactured  products  (yarn  and  fabric)  are  very  heavily  taxed.  These  conditions 
have  led  to  the  rapid  development  of  American  spinning  and  weaving.1  The  importation 
of  raw  silk  into  the  United  States  shows  continuous  and  rapid  increase,  the  annual  averages 
being:  1881-1885,15,300  quintals;  1886-1890,23,100;  1891-1895,31,300;  1896-1900, 
43,500  ;  1901-1905,  65,300  quintals,  which  is  about  one-third  of  the  world's  production 
(excluding  the  local  consumption  of  the  Far  East). 

The  Italian  silk  industry  has  passed  through  various  crises,  not  on  account  of  excessive 
production — since  working  on  stock  is  not  usual  with  silk  articles  and  the  demand  is  often 
greater  than  the  supply — but  owing  to  various  circumstances,  not  the  least  among  which 
are  the  tariffs  raised  against  Italy  as  retaliation  for  the  protection  of  many  Italian  industries 
by  the  tariff  of  July  1887.  The  most  acute  crises  of  the  Italian  silk  industry  were  those 
of  1893  and  1903,  which  were  the  cause  of  numerous  financial  disasters,  and  that  of 
1907-1908,  the  effects  of  which  are  still  felt,  and  which  resulted  from  the  great  American 
crisis  and  is  now  being  aggravated  by  French  and  Japanese  competition.  The  quin- 
quennial average  price  of  raw  Italian  silk  fell  gradually  from  62-1*.  per  kilo  in  1876-1880 
to  38 -Is.  in  1901-1905,  mainly  owing  to  increase  in  the  world's  production  (see  Table,  p.  695). 
In  1906  and  1907  a  rise  in  price  of  raw  silk  occurred  ;  thus,  that  of  organsine  sublime 
(count  i£)  was  40s.  per  kilo  at  the  end  of  1905,  and  rose  to  49s.  Qd.  towards  the  end  of 
1906  and  to  60s.  Qd.  in  August  1907,  after  which  a  fall  took  place  owing  to  the  American 
crisis. 

Silk-twisting  in  Italy  in  1910  employed  800,000  spindles  (four-fifths  in  Lombardy  and 
the  remainder  in  Piedmont),  which  produced  4,500,000  kilos  of  organsine  and  tram,  about 
one-half  from  imported  raw  silk. 

The  silk-waste  which  was  produced  in  Italy  in  1910  (and  was  exported  to  the  extent 
of  two-fifths  while  the  remainder  was  worked  up  in  Italy)  amounted  altogether  to  5,300,000 
kilos  of  the  value  of  £500,000. 

Silk,  carded  and  combed  in  Italy,  amounts  to  about  1,500,000  kilos  and  the  chappe 
yarn  to  almost  900,000  kilos,  of  which  200,000  kilos  are  consumed  in  Italy  and  the  rest 
exported.  Six  thousand  workpeople  are  employed  in  the  treatment  of  waste,  the  ten  estab- 
lishments in  this  trade  containing  about  80,000  spindles  in  1912. 

The  exportation  of  fabrics  from  Italy  was  288,428  kilos  in  1892  ;  443,371  in  1895  ; 
1,011,567  in  1900  ;  1,254,416  in  1905;  and  1,304,750  in  1908. 

The  countries  with  large  outputs  of  cocoons  are  not  always  large  consumers  of  silk 
wares,  while  in  general  large  consumers  are  not  producers.  Italy  has  a  total  internal 
consumption  of  6500  to  7500  quintals  of  silk  articles,  and  the  relation  between  home 
consumption  and  exportation  for  the  principal  countries  in  1899  was  as  follows  : 


France 
Germany . 
Austria    . 
Italy  .      . 

As  regards  the  quantity  of  raw  silk  passing  through  their  conditioning  establishments, 
the  two  principal  silk  markets  in  the  world  are  Lyons  and  Milan,  which  together  receive 

1  The  protective  duty  on  manufactured  wares  was  50  per  cent,  ad  valorem  in  1883,  while  it  rose  to  75  per  cent, 
in  1897,  and  later  to  90  per  cent.  In  1882  there  were  only  8000  power-looms  (including  2500  for  ribbon)  and  3100 
hand-looms  for  silk  in  the  United  States,  while  in  1901  the  number  of  power-looms  was  52,000  (7000  for  ribbon) 
and  that  of  hand-looms  was  reduced  to  800.  In  the  same  period  the  number  of  spindles  for  twisting  and  spinning 
increased  from  450,000  to  1,900,000.  The  output  of  silk  gloves  was  2000  dozens  in  1887  and  more  than  180,000 
dozens  (£200,000)  in  1901.  The  production  of  silk  articles  increased  sixtyfold  during  the  latter  half  of  the  nineteenth 
century. 

The  output  in  America  is,  however,  not  equal  to  tin-  consumption,  the  proportion  bet\ 
per  cent,  for  silk  fabrics.  85  per  cent,  for  ribbons,  and  5:5  per  cent,  for  velvet.  In  1901  the  IT 
silk  wares  to  the  value  of  £5,760,000,  now  diminished  to  £3.200,000-43  pel  cent,  from  l-'ra 
Japan,  17  per  cent,  from  Germany,  and  16  percent,  from  Switzerland.  The  American  (!o\ 
times,  by  offering  prizes,  attempted  to  initiate  the  cultivation  of  mnlberiies  and  the  reaiing  < 
poor  success,  probably  because  skilled  agricultural  labour  is  lacking  and  is  not  easy  to  turn 


Home 
consumption 

Exports 

Home 
consumption 

Exports 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

61 

39 

Switzerland 

5 

95 

60 

40 

United  States 

95-100 

0-5 

88-5 

12-5 

China  . 

.     about  50 

about  50 

20 

80 

Japan 

„      50 

„      50 

cl  States  import  c<l 
18  per  cent,  from 
incut  have  several 
Ikwonns,  but  with 
rapidly,  and  also 


because  labour  is  expensive. 

The  attempts  which  have  been  made  in  the  Argentine  have  been  somewhat  more  successful  but  not  altogether 
satisfactory.  To  the  800,000  mulberry  -trees  planted  during  the  course  of  20  years,  -4,000,000  have  been  added 
during  the  past  four  years,  and  in  1907  the  crop  of  cocoons  was  250  quintals. 


698  ORGANIC    CHEMISTRY 

about  two-thirds  of  all  the  silk,  conditioned  in  Europe,  the  separate  amounts  being  as 
follow : 

Milan  Lyons 

1881  36,652  53,480 

1 890  43,477  44,072 

1900  72,335  tio,4IS 

I9o:j  .         .         .               83,725  <;<;,5os 

1905  .          .                 94,391  70,102 

190(5  .          .          .                101,484  71,719 

1908  .          .          .                 95,293  73,728 

In  1908  13,186  quintals  arrived  at  Lyons  from  Europe,  7564  from  the  Levant,  and 
50,000  from  the  Far  East ;  and  at  Milan.  67,187  quintals  from  Europe,  1477  from  the 
Levant,  and  36,530  from  the  Far  East.  During  recent  years  Milan  has  lost  ground 
compared  with  Lyons. 

SEA  SILK  (Hi/Mftu.y)  is  found  in  tufts  protruding  from  the  shells  of  a  mollusc  (Pinna 
nobilis),  30  to  40  cm.  long  anil  15  to  20  cm.  broad,  attached  to  the  rocks  of  the  Red  .Sea 
and  the  Mediterranean  (Sicily,  Sardinia,  Elba).  It  has  a  pale  golden,  more  or  less  brownish 
colour,  and  sometimes  shows  greenish  reflection.  After  being  washed  with  soap  and  water 
and  dried  in  the  shade,  it  is  combed  and  spun  like  other  textile  fibres.  Although  sometimes 
regarded  as  an  abundant  product,  it  is  in  reality  rare,  at  least  in  Italy,  and  figures  rather 
in  museums  than  on  the  market. 

ARTIFICIAL  SILK  is  the  inaccurate  name  given  to  the  product  which  has  been  for 
some  time  on  the  market  in  competition  with  natural  silk.  There  is,  indeed,  no  chemical 
relation  between  the  two  products.  In  place  of  the  fibroin  and  sericin  produced  by  Bombyr 
mori,  the  new  silvery  thread  contains  merely  cellulose,  as  is  t  lie  case  with  so  many  other 
vegetable  products.  It  has,  however,  the  lustrous  appearance  of  natural  silk  and  only 
by  reason  of  this  property  does  it  compete  with  the  latter. 

The  struggle  between  the  natural  and  the  artificial  product  has  scarcely  begun  and  it 
is  not  easy  to  foretell  within  what  time  and  what  limits  the  one  or  the  other  will  be  victorious. 
We  are  certainly  on  the  eve  of  neither  a  serious  convulsion  in  the  agricultural  industry 
nor  the  disappearance  of  the  mulberry  and  silkworm,  but  it  may  be  affirmed  that  artificial 
silk  has  established  a  position  in  the  making  of  certain  fabrics  formerly  obtained  solely 
from  the  natural  product. 

But  the  new  artificial  fibre  has  still  many  defects  which  limit  its  use,  for  the  present, 
to  definite  branches  of  the  textile  industry,  and  time  is  thus  given  to  the  producers  of 
natural  silk  to  repair  the  grave  error,  committed  in  the  past,  of  spoiling  their  valuable 
product  by  excessive  weighting,  and  so  injuring  its  sale. 

The  first  beneficial  effect  of  the  appearance  of  artificial  silk  should  hence  be  to  bring 
the  silk  industry  to  the  sound  basis  on  which  it  was  built,  and  which  would  enable  it  to 
withstand  any  artificial  competitor  for  many  years  to  come. 

The  prime  material  for  the  preparation  of  artificial  silk  is  cellulose,  that  remarkable  sub- 
stance which  has  so  simple  a  composition — carbon,  hydrogen,  and  oxygen — but  so  complex 
and  highly  polymerised  a  molecule  (see  p.  503),  and  already  yields  so  many  most  important 
industrial  products — from  mercerised  cotton  to  celluloid  and  pegamoid,  from  guncotton 
to  collodion,  from  explosive,  smokeless  gelatines  to  alcohol,  and  finally  to  artificial  silk.1 
Artificial  silks  of  various  different  types  are  met  with  on  the  market  :  - 

1  When  cellulose  is  in  the  form  of  wood  for  fuel,  I  en.  metre  costs  about  (i.s\  ;  the  s;ime  eiiliie  metre  of  wood, 
when  boiled  with  lime,  soda,  and  sulphite  gives  a  paper  pulp  worth  about  32s.  and  yielding  paper  valued  at.  Mn., 
or  more.  But  it'  this  pulp  is  transformed  into  artificial  silk,  its  value  may  be  as  high  as  JC80  to  i!24(l,  according 
to  the  articles  prepared  (artificial  hair  and  silk,  oellulo.se  acetate). 

3  Artificial  silk,  although  of  recent  preparation,  lias  already  an  interesting  history.  As  early  as  I  7:U  Iteauinur 
foresaw  the  possibility  of  preparing  lustrous  fibres,  similar  to  silk,  from  gummy  or  adhesive  substances,  and  in 
1886  Audemare  (of  Lausanne)  attempted  but  with  imperfect  success  to  put  Reaumur's  idea  into  practice. 

Expectation  of  success  in  the  solution  of  this  important  problem  arose  only  later  when  it  was  found  possible 
to  prepare  slender  collodion  fibres  for  the  manufacture  of  the  carbon  filaments  of  incandescent  electric  lamps. 
In  1885  Count  Hilaire  de  Chardoimet  of  Besaneon,  then  a  student  at  1  he  Paris  Polytechnic,  filed  a  patent,  for  the 
manufacture  of  artificial  silk  by  spinning  collodion  solutions,  and  at  the  1'aris  Exhibition  of  1889  he  showed  his 
lirst  machine  working.  Swan,  in  London,  had  previously  obtained  fibres  of  artificial  silk,  but  these  were,  without 
practical  interest. 

In  1891  de  Chardonnct  formed  a  < ipany  at  Besancon  with  a  capital  of  £'2-4(i.(l(in.  for  the  manufacture  of  this 

new  product  on  a  large  scale. 

But  for  some  years  de  Chardoimet  silk  could  not  be  used  as  it  was  composed  of  nitrocellulose,  and  hence  highl; 


699 

(1 )  That  obtained  by  the  denitration  of  collodion  cotton  previously  dissolved  in  a  mixture 
of  alcohol  and  ether  and  then  reduced  to  very  fine  fibres  by  means  of   special  spinning 
machinery  (de  Chardonnet,  Lehner,  Viviers)  (see  also  Details  of  working  methods). 

(2)  That  prepared  by  passing  hydrocellulose  (mercerised  cotton)  dissolved  in  ammoniacal 
popper  oxide  solution,  through  very  fine  capillary  glass  tubes  so  as  to  obtain — after  complete 
coagulation  in  a  bath  of  sulphuric  acid  a)  1  (>    to  20    Be.  ur  one  of  5  per  cent,  caustic  soda — 
filaments   so   slender  that    225,000  metres   do   not  weigh  1  kilo  (Pauly  or  Fremery  and 
Urban  silk).1 

(3)  That  obtained  by  decomposing,  with  ammonium  sulphate,  cellulose  thiocarbonate 
(sodio-cellulose  xanthate),  suitably  matured  (i.e.  polymerised)  and  converted  into  slender 
fibres  by  being  forced  through  a  platinum  plate  furnished  with  eighteen  very  small  orifices  so 
as  to  give  simultaneously  eighteen  filaments,  1,000,000  metres  of  one  of  these  weighing  less 
than  1  kilo  (viscose  silk  of  Cross,  Bevan,  Beadle,  Stearn,  and  Tophar,  1892-1900). 2 

(4)  The  silk  prepared  from  cellulose  acetate  by  Cross  and  Bevan  seems  to  be  free  from 
I  he  defects  mentioned  above  and  to  be  superior  to  all  other  artificial  silks  in  its  resistance, 
which  is  equal  to  that  of  natural  silk.      The  manufacture  of   this  was  started  a  few  years 
ago  by  Count  Donnersmark,  using  acetic   anhydride  and  chloroform,  but  it  is  too  costly 
to  compete  with  other  silks,  and  is  dyed  only  in  dilute  alcoholic  solutions  (Ger.  Pat.  152,432). 
Excellent  solvents  for  cellulose  acetate  have  been  found  in  tetrachloroethane  and  formic 
acid  (Ger.  Pat.  237,718  of  1907). 

(5)  Millar  and  Hummel's  Vandura  silk,  obtained  from  gelatine  solution  and  now  from 
casein,  is  not  used  praetieally. 

((>)  K.  Hofmann  (Ger.  Pat.  227,198  of  1909)  obtains  artificial  silk  and  also  hair  and 
films,  by  dissolving  cellulose  at  220°  in  a  mixture  of  concentrated  phosphoric  and  acetic 
acids,  and  then  precipitating  with  water  or  salt  or  alkali  solution. 

The  raw  material  for  the  de  Chardonnet  and  Fremery  silks  is  cotton  waste,  which  should 
answer  the  same  requirements  as  that  used  in  making  collodion  and  guncotton.  For 
viscose  the  raw  material  is  wood-cellulose,  such  as  is  used  in  paper-making.  Although 
the  chemical  processes  arc  different,  the  final  product  for  all  three  types  of  silk  is 
more  or  less  oxidised  hydrocellulose  ;  Chardonnet-Lehner  silk  consists  of  hydrated  oxy- 
cellulose. 

dangerous  to  the  wearer  and  to  warehouses  in  which  it  was  stored,  owing  to  its  inflammability.  Attempts  to  render 
the  silk  harmless  by  the  addition  of  various  substances  proved  futile,  and  the  problem  was  sqlved  subsequently 
to  1893  by  the  elimination  of  the  nitro-groups  combined  with  the  cellulose  and  the  regeneration  of  the  latter  without 
alteration  of  its  lustre.  When  treated  in  this  way  it  burns 'quite  like  other  cotton  or  silk  fibre. 

But  this  operation  is  accompanied  by  a  new  disadvantage  which  has  not  yet  beeii  completely  removed.  On 
denitration,  the  artificial  silk  loses  part  of  its  resistance,  and  when  it  is  wetted  the  resistance  and  elasticity  diminish 
further  by  two-thirds.  But  in  spite  of  this  defect  the  product  is  marketable,  its  production  being  started  before 
the  Paris  Exhibition  of  1900  and  subsequently  prosecuted  on  a  large  scale. 

1  The  first  patent  for  this  process  was  that  of  Despeissis  in  1890,  but  this  was  not  renewed  in  a  year's  time. 
The  process  was  improved  and  rendered  practicable  by  Pauly,  Bronnert,  Fremery,  and  Urban,  and  the  manufac- 
ture was  undertaken  by  the  Vereinigten-Glanzstoff  Fabriken  of  Elberfeld.  Well  defatted  cotton  waste  is  lixiviated 
with  sodium  carbonate  and  hydroxide  in  an  autoclave  for  3  to  4  hours,  rinsed,  bleached  with  cold  hypochlorite 
solution,  well  washed  and  centrifuged.  The  mass  is  then  treated  with  concentrated  caustic  soda  to  mercerise 
it  and  form  sodio-cellulose,  which  is  more  soluble  than  cellulose  ;  or  concentrated  ammonia  is  added  to  a  mixture 
of  the  centrifuged  cotton  witli  caustic  soda  and  copper  sulphate  solutions  until  the  whole  dissolves  (6  to  7  kilos  of 
cotton  per  100  litres  of  solution).  When  cellulose  is  to  be  dissolved  in  cupro-ammoniacal  solution  the  latter  is 
prepared  beforehand  in  large  tanks  (in  cellars)  containing  scrap  copper  and  concentrated  ammonia  solution  kept 
in  circulation  by  a  pwnp  which  also  injects  air  until  each  litre  of  solution  contains  about  15  gnus,  of  dissolved 
copper.  In  this  liquid,  stirred  now  and  then,  cellulose  dissolves  in  6  to  8  days,  the  solubility  increasing  as  the 
amount  of  copper  present  increases  and  as  the  temperature  is  lowered  (between  0°  and  4°).  As  soon  as  the  cellulose 
lias  dissolved  and  the  mass  become  dense  and  stringy  it  must  be  filtered  under  pressure,  since  if  this  is  delayed 
i  no  or  three  days  the  cellulose  begins  to  undergo  depolymerisation  (especially  in  a  warm  place),  and  the  mass 
loses  its  viscosity,  with  the  result  that  the  silk  obtained  is  of  poor  quality,  irregular  and  weak. 

Spinning  follows  closely  on  filtration.  Tlie  threads  from  the  capillary  glass  tubes  were  at  one  time  coagulated 
by  passing  them  into  sulphuric  acid  of  about  20°  Be.,  but  there  is  then  danger  of  weakening  of  the  fibre  owing  to 
excessive  hydration,  which  is  facilitated  by  the  rise  of  temperature  caused  by  the  neutralisation  of  the  ammonia. 
On  this  account  it  is  now  preferred  to  produce  coagulation  by  means  of  5  per  cent,  caustic  soda,  this  giving  a  softer 
and  more  lustrous  silk  from  which  a  very  weak  sulphuric  acid  bath  readily  eliminates  the  traces  of  copper  hydrate 
precipitated  by  the  soda.  According  to  Ger.  Pat.  221,041  (1908)  coagulation  with  alkaline  sulphite  or  bisulphite 
solution  appears  advantageous. 

1  According  to  F.  Todtenhaupt  (1909),  to  obtain  perfect  solution  and  transformation  into  xanthate,  the 
carbon  disulphide  is  diluted  with  an  indifferent  liquid,  e.g.  benzene,  ligroin,  CC1«,  &c.,  the  sodio-cellulose  being 
thus  the  more  completely  and  easily  penetrated.  Before  spinning,  the  pulp  is  matured  by  heating  at  70°  to 
90°  or  by  leaving  for  a  longer  time  at  15°  to  18°.  In  making  viscose  silk  it  was  for  some  years  found  difficult  to 
iiit  on  the  exact  maturation-point  (polymerisation  of  the  cellulose)  and  to  avoid  excessive  adhesive  properties. 
But  this  difficulty  has  now  been  overcome  and  about  1,500,000  kilos  of  viscose  silk  are  produced  annually. 

It  must,  however,  be  remembered  that  of  the  single  thread  (lava)  of  the  silkworm,  6,000,000  to  7,000,000  metres 
are  required  to  weigh  1  kilo. 


700  ORGANIC    CHEMISTRY 

Of  the  innumerable  now  patents  for  the  manufacture  of  artificial  silk,  mention  may  be 
made  of  the  following  : 

Luiniere  Bros,  of  Lyons  dissolve  the  nitrocellulose  in  amyl  acetate  so  as  to  avoid 
clotting  (Ger.  Pat.  IBS, 173  of  1905).  It  has  been  suggested  to  add  resin,  oil,  oleic  acid, 
&c.,  to  the  solvent  to  economise  the  latter  and  to  give  a  more  homogeneous  solution,  hut 
such  additions  retard  the  subsequent  denitration.  Also  the  addition  of  acid  leads  to  the 
formation  of  oxycellulose  during  the  denitration,  with  diminution  in  the  strength  of  the 
silk. 

To  obtain  Chardonnet  silk,  collodion-cotton  is  prepared  in  the  way  described  in  the 
section  on  Explosives  (pp.  232  et  seq.),  and  after  elimination  of  the  acid  by  thorough  washing, 
the  cotton  is  pressed  hydraulically  or  centrifuged  to  reduce  the  moisture-content  to  25 
to  30  per  cent.  In  this  condition  it  is  dissolved  in  5  to  10  times  its  weight  of  a  mixture 
of  3  parts  of  ether  and  2  of  alcohol,  with  which  it  is  shaken  for  a  couple  of  hours  in  revolving 
iron  drums  ;  de  Chardonnet  first  prepared  solutions  of  collodion  with  dried  nitrocellulose, 
but  Lehner  of  Frankfort  found  that  moist  nitrocellulose  also  dissolves  in  alcohol  and 
ether,  avoiding  the  danger  of  drying  and  also  giving  a  more  homogeneous  fibre.  If  a  little 
mineral  acid  is  added  to  the  collodion  solution,  the  mass  becomes  much  more  fluid  and 
requires  less  pressure  for  spinning  [according  to  Eng.  Pat.  10,932  of  1910,  acetylene  tetra- 
chloride  (see  p.  102)  is  an  excellent  solvent  for  nitrocellulose].  The  dense  collodion  solution 
is  passed  under  a  pressure  of  40  atmos.  through  a  cotton-wool  filter,  then  left  for  a  couple 
of  days  for  the  air-bubbles  to  escape,  and  finally  forced  first  through  cotton-wool  and  then 
through  capillary  glass  tubes  having  a  bore  of  0-2  to  0-08  mm.,  under  a  pressure  of  60 
to  80  atmos. 

The  slender  threads  issuing  from  the  capillary  tubes  under  pressure  and  in  a  closed-in 
machine,  through  which  a  current  of  air  passes  to  carry  off  the  alcohol  and  ether  vapour,1 
are  united  in  a  number  varying  from  6  to  20,  and  under  a  water-jet  are  wound  on  glass 
spools  in  a  coagulated  condition,  but  still  somewhat  adhesive  owing  to  the  moisture  left  in 
the  nitrocellulose.  After  a  short  time  on  these  spools  the  fibre  solidifies  completely  and 
can  be  manipulated  without  danger  of  the  filaments  adhering.  It  is  then  combined, 
twisted,  and  reeled  in  the  same  way  as  silk. 

The  artificial  silk  fibre  thus  obtained  is  as  lustrous  and  strong  as  natural  silk,  even 
in  the  moist  state.  But  it  has  a  rather  horny  feel,  is  completely  impermeable  to  water, 
and  hence  cannot  be  dyed  in  vat,  while  it  exhibits  also  the  serious  disadvantage  of  ready 
inflammability,  which  came  to  be  avoided  by  elimination  of  the  nitro-groups  (1893). 

Ferrous  chloride,  formaldehyde,  thiocarbonate,  &c.,  were  tried  as  denitrating  agents, 
but  the  best  results  were  obtained  with  hydrosulphides  of  ammonium,  calcium  (0-4  to 
0-5  per  cent,  solution),  and  magnesium,  and  with  dilute  sodium  sulphide  solution  acting 
for  3  to  4  hours  in  the  cold.  The  denitration  must  be  carried  out  with  great  care  since 
if  as  little  as  0-1  per  cent,  of  nitrogen  remains,  irregular  striations  are  obtained  on  dyeing. 
In  practice  all  but  0-05  per  cent,  of  N  can  be  eliminated,  it  being  impossible  to  push  the 
denitration  as  far  as  the  disappearance  of  the  diphenylamine  reaction  without  considerable 
attack  of  the  fibre.  The  regularity  of  the  dyeing  is  also  largely  influenced  by  the  manner 
in  which  the  white  silk  is  first  dried.  Too  rapid  drying  at  a  temperatiire  above  70°  and 
with  too  dry  air,  gives  rise  at  many  points  to  oxycellulose  which  alternates  with  hydro- 
cellulose  and  hence  gives  rise  to  non-uniformity  of  tint. 

After  denitration;  the  silk  contains  only  minimal  traces  of  nitro-groups,  but  these  are 
in  sufficient  amount  to  allow  of  the  distinction  of  Chardonnet  silk  from  other  artificial 
and  from  natural  silks,  by  means  of  the  diphenylamine  reaction.  'Artificial  silks 
may  also  be  differentiated  from  natural  silk  by  microscopic  examination  (see  Figs. 
442,  443). 

Denitrated  silk  is  less  resistant  and,  as  with  other  qualities  of  artificial  silk,  the  resis- 


ARTIFICIAL    SILK    DYEING 


701 


banco  is  considerably  less  in  (he  moist  state  ;  under  such  conditions  it  can  still  compete 
with  heavily  weighted  natural  silks.1 

In  general  a  libro  of  artificial  silk  can  be  distinguished  from  one  of  natural  silk  owing 
( o  t  he  small  resistance  of  the  former  to  tension  when  in  the  moist  condition. 

In  bleaching  artificial  silk,  the  latter  is  passed  first  into  a  weak  sulphoricinate  bath  at 
1<>  and  then  into  a  weak  bath  of  sodium  hypochlorite  and  acetic  acid  or  of  calcium  hypo- 
chlorite  (0-15  per  thousand)  or  of  permanganate  (see  Cotton).  It  is  then  dried,  the  loss 
in  weight  (water  and  denitration)  being  nearly  50  per  cent. 

When  the  artificial  silk  factories  supply  a  homogeneous  product,  dyeing  is  usually 
accomplished  without  difficulty  on  skeins  of  yarn,  just  as  with  cotton  and  silk.  The 
methods  of  dyeing  arc  those  used  for  cotton  or,  more  exactly,  for  mercerised  cotton,  which 
is  also  cellulose.  The  dyeing  can  bo  carried  out  without  special  mordants  if  substantive 
dyesfuH's  (diamme,  beir/.o,  congo,  &c.)  are  used  in  a  bath  of  sodium  sulphate  and  a  little 
sodium  carbonate  at  the  temperature  of  50°  to  60°,  various  precautions  being  taken  in 
the  manipulation, 

With  basic  dyes,  a  tannin  or  tartar  emetic  mordant  is  used,  just  as  with  cotton,  the 


d 


KJ<;.  442. — (Pauly)  d,  sign  of  crossed  fibres; 
•s7,  striation ;  b,  air- bubbles;  q,  fine  transverse 
striations;  B,  sections  of  fibres 

1  According  to  Hassack  the  strengths  are  as  follow  : 


Elasticity 
Xatural  silks  boiled  and  lustred    .         .         .          .20 

,.          ,,      red,  slightly  weighted        .         .         .20 

.,          .,      blue-black,  100  per  cent,  weighting    .     20 

„          „      black,  140  per  cent,  weighting  .          .     20 

500        „  ,,  .          .     20 

Cellulose  acetate  silk    ......     17 

White  Chardonnet  silk          .         .         .         .         •  I    o 

U'hner  (Frankfort)  silk          .          .          .          .          .  f 

I'auly  (Elbcrfeld)  silk 14 

Viscose  silk  .......      14 

Cotton  thread  14 


FIG.  443. — (Chardonnet)a,  air- bubbles ; 
B,  sections  of  fibres 


Tenacity  in  kilos  per  sq.  mm. 


Dry 
37-5 
20-0 
12-1 
7-9 
2-2 
10-2 
14-1 
17-1 
19-1 
21-5 
11-5 


Moist 

35 

15-6 
8-0 
6-3 

5-8 
1-7 
4-3 
3-2 

18-6 


Th<  ,-/tiisticit./j  is  the  elongation  exhibited  by  100  cm.  of  the  fibre  before  breaking.  The  tenacity  or  resistance 
of  natural  silk  is  3  to  13  grms.  for  the  single  thread  (bava).  Echallier  (Lyons)  has  recently  increased  the  resistance 
of  viscose  in  the  moist  state  by  treating  it  in  a  bath  containing  15  per  cent,  of  formaldehyde,  5  per  cent,  of  alum 
and  5  per  cent,  of  lactic  acid. 

A  further  disadvantage  of  artificial  silk  is  its  high  specific  gravity,  the  same  weight  of  yarn  of  the  same  size 
giving  a  larger  quantity  of  fabric  in  the  case  of  the  natural  silk  than  with  the  artificial.  Hut  while,  with  the  first 
artificial  silks,  the  excess  of  specific  gravity  was  15  to  20  per  cent.,  the  difference  is  now  reduced  to  7  to  8  per 
cent.,  and  further  progress  in  this  direction  is  not  improbable.  Natural  silk  has  the  sp.  gr.  1-36  and  cellulose 
acetate  silk  1-251,  while  other  artificial  silks  show  values  exceeding  1-5. 

Marked  advances  have  been  made  also  in  the  count  of  the  thread.  Until  a  few  years  ago.  only  yarn  of  120 
denari  (75,000  metres  per  kilo)  could  be  made,  but  nowadays  counts  of  80  denari  (112,000  metres  per  kilo)  are 
regularly  spun,  and  in  some  cases,  with  Lehnei  silk,  40  denari  (225,000  metres  per  kilo)  has  been  reached.  These 
are  still  far  from  the  fineness  of  natural  silk  (10  to  20  denari)  but  represent  an  appreciable  step  forward. 

The  machinery  used  in  spinning  artificial  silk  has  now  undergone  further  improvements  which  permit  of  the 
product  ion  at  once  of  bundles  of  threads,  these  being  subjected  during  their  development  to  rapid  rotation  so  that 
the  completely  twisted  yarn  is  obtained  in  a  single  operation.  There  are  also  machines  which  give  two  bundles  of 
threads  twisted  in  opposite  directions  and  at  the  same  time  wind  the  two  bundles  one  on  the  other  so  as  to  produce 
finished  organsine  of  two  threads. 


ORGANIC    CHEMISTRY 

dyeing  being  commenced  in  the  cold  and  terminated  at  a  gentle  heat  in  presence  of  2  to 
3  per  cent,  of  acetic  acid.  Certain  basic  colours  dye  Chardonnet  silk  even  without 
mordanting.  The  new  sulphur  colours  are  also  used. 

These  different  processes  give  all  colours,  from  the  pale  and  more  delicate  ones  to 
black,  in  all  shades.  One  merit  of  artificial  silk  is  that  it  cannot  be  weighted  so  heavily  or 
so  easily  as  natural  silk.  Only  when  black  can  it  be  relatively  heavily  weighted. 

Cellulose  acetate  silk  is  not  readily  dyed  by  aqueous  solutions  of  colouring-matters, 
but  as  it  easily  fixes  phenols  even  from  dilute  solution,  a  tine  pa  rani  tramline  red  can  be 
obtained  by  passing  the  silk  into  a  hot  0-5  per  cent.  /3-naphthol  bath  and  then  into  a 
1-5  per  cent,  p-nitraniline  hydrochloride  bath  containing  sodium  acetate. 

The  most  valuable  property  of  artificial  silk  is  its  great  lustre,  which  exceeds  that  of 
natural  silk  and  permits  of  its  use  for  a  large  number  of  different  articles.  Beautiful 
new  effects  are  obtained  by  using  it  as  weft  in  figured  textiles  with  warp  of  natural  silk, 
a  new  opening  being  thus  provided  for  the  latter.  It  is  also  used  with  advantage  as  weft 
in  silk  ribbons.  For  some  years  it  has  held  almost  undisputed  sway  in  the  lace  industry, 
and  a  single  Italian  manufacturer  of  this  material  consumes  annually  15,000  to  20,000 
kilos  of  artificial  silk.  Fringe  and  cord  for  ornamenting  garments,  lace,  embroidery,  &c., 
are  now  largely  made  from  artificial  silk.  Special  articles  which  cannot  be  obtained  with 
natural  silk  are  made  from  the  artificial  product.  There  is  now  a  large  consumption  of 
artificial  hair  prepared  from  artificial  silk  by  fusing  together  several  thin  fibres  so  as  to 
form  a  single  large  compact  filament  which,  unlike  large  fibres  obtained  directly  bv  spinning, 
is  flexible  and  resistant.  This  artificial  white  hair,  which  can  be  dyed  various  colours, 
is  in  great  demand  as  a  substitute  for  horsehair,  which  is  difficult  to  bleach  and  also 
rather  expensive  owing  to  the  increased  demand  for  horses  for  military  purposes.  This 
hair  is  used  for  various  ornaments  but  mostly  for  making  wigs  for  ladies  and  artificial 
bristles. 

Another  interesting  application  of  artificial  silk  is  in  the  manufacture  of  incandescent 
gas-mantles  according  to  Plaissetty's  patent :  such  mantles  are  more  resistant  to  shock, 
even  after  burning,  and  can  be  used  in  trains. 

Largely  used  also  is  a  new  product  obtained  from  viscose,  namely,  a  kind  of  ebonite, 
which  serves  well  for  the  manufacture  of  artistically  worked  and  coloured  umbrella  handles, 
knife  handles,  &c.,  and  resists  the  actipn  of  the  acids  and  alkalis  with  which  it  is  likely  to 
come  into  contact. 

Casein  products,1  which  have  also  been  suggested  for  these  purposes,  cannot  compete 
with  viscose  ebonite,  which  exhibits  marked  advantages  over  bone  and  horn  in  the  manu- 
facture of  brushes,  as  it  can  be  more  easily  worked  and  more  easily  pierced  to  allow  of  the 
fixing  of  the  bristles. 

As  hair-ornaments  for  ladies,  great  use  is  made  of  artificial  silk  in  thin  sheets  or  ribbons 
showing  brilliant  colours  and  sparkle.  Artificial  silk  is  also  used  in  large  quantity  for 
making  materials  for  tapestry,  upholstery,  neckties,  hat-linings,  &c.,  with  which  no  re- 
sistance to  the  action  of  water  is  required.  With  zinc  salts  viscose  smeared  on  paper  or 
.  fabric  shows  fine  silky  effects  and  fine  results  are  also  obtained  with  bronze  powder  made 
into  a  paste  with  viscose  and  spread  on  different  cloths. 

Important  new  outlets  would  offer  themselves  for  artificial  silk  if  the  resistance  to  the 
action  of  water  could  be  improved.  It  seems  to  be  a  question  of  saturating  the  hydroxyl 
groups  of  hydrocellulose  so  as  to  render  the  latter  stable  towards  water,  and  the  most 
promising  attempt  yet  made  is  that  with  cellulose  acetate,  which  gives  a  silk  highly 
resistant  but  as  yet  too  expensive,  since  acetic  anhydride  is  used  in  its  manufacture, 
while  the  cellulose  acetate  must  be  dissolved  in  chloroform  to  be  spun.  In  America  this 
new  product  is  used  as  an  electrical  insulator  (its  dielectric  constant  is  4  and  that  of  viscose 
7,  compared  with  5-6  for  porcelain). 

The  last  patents  of  the  Badische  Anilin-  und  Soda-Fabrik  in  1904  and  the  more  recent 
ones  of  Friedrich  Bayer  and  Co.,  indicate  that  a  speedy  solution  of  this  important  problem 
may  be  hoped  for. 

1  According  to  a  Dutch  patent  of  1911  (No.  431,052),  part  of  the  casein  suited  to  the  manufacture  can  be  sepa- 
rated by  precipitating  the  unsuitable  casein  (which  gives  brittle  products)  from  skim-milk  by  means  of  sodium 
pyrophosphate  solution  (3  grms.  of  the  salt  per  litre  of  milk).  From  the  decanted  liquid,  the  soluble  part  of  the 
casein  is  then  precipitated  by  means  of  dilute  acid.  This  precipitate  is  pressed,  dissolved  in  a  little  dilute  ammonia, 
filtered,  reprecipitated  with  acid,  again  pressed,  rendered  plastic  with  a  little  ammonia,  and  spun  ;  the  thread  is- 
rendered  insoluble  by  means  of  Dilute  formaldehyde  solution. 


TESTS    FOR    FIBRES 


70.3 


In  Kurope  there  are  30  large  artificial  silk  works,  with  a  capital  of  more  than 
£2,400,000,  among  these  being  the  original  Chardonnet  factory  at  Besancon,  which  produces 
2000  kilos  of  silk  per  day,  and  the  equally  important  ones  at  Frankfort  and  Tubize  (Belgium), 
and  that  of  the  Glanzstoff  Company  at  Elberfeld.  In  France  there  are  7  factories  working 
profitably  ;  in  Germany,  8  ;  Belgium,  3  ;  England,  2  ;  Spain,  1  ;  Austria-Hungary, 
4  ;  America,  3  ;  Russia,  3  ;  Japan,  1. 

The  world's  production  of  artificial  silk  was  about  2,500,000  kilos  in  1905  and  more 
tlian  6.000.000  kilos  in  1011,  about  2,500,000  being  nitrocellulose  silk,  an  equal  amount 
ammoniacal  copper  oxide  silk,  and  nearly  1,500,000  kilos  viscose  silk.  The  output  in 
France  was  about  1,700,000  kilos  in  1908,  the  exports  being  63,700  kilos  in  1908,  78.500 
in  1909,  and  161,700  in  1910. 

Italy  consumes  large  quantities  of  artificial  silk.  The  three  large  Italian  factories 
(Padua,  Pa  via,  and  Turin)  arc  working  under  adverse  conditions  owing  to  the  excessive 
cost  of  patents  and  the  keen  foreign  competition.  As  is  shown  by  the  following  figures, 
the  importation  of  artificial  silk  into  Italy  is  continuously  increasing: 


190.> 

1906 

1907 

1908 

1909 

1910 

kilos 

kilos 

kilos 

kilos 

kilos 

kilos 

White       . 
Dyed        . 

275 
2,338 

12,900 

8,080 

25,500 
10.920 

38,250 
2,762 

68,822 
1,080 

210,000 
1,560 

(£126,030) 

(£1,060) 

The  exports  wen,- 

White     . 
Dyed       . 

—  • 

— 

572 
5,238 

18,890 
1,187 

82,472 
5,299 

83,942 
5,422 

(£50,365) 
(£3,685) 

The  exportation  is  mainly  from  the  works  at  Padua,  which  is  under  contract  to  send 
its  whole  output  to  a  German  factory.  In  order  to  withstand  competition  better,  the 
artificial  silk  factory  at  Pa  via  began  in  1911  to  use  the  ammoniacal  copper  oxide  process 
instead  of  that  with  nitrocellulose  which  had  been  previously  employed. 

Artificial  silk,  which  was  sold  at  28s.  to  32,9.  per  kilo  in  1903  and  1904,  could  be  bought 
at  20s.  in  1905,  while  the  price  fell  to  16s.  in  1906,  13s.  6d.  in  1908,  and  12s.  in  1910,  the 
poorer  qualities  being  sold  at  6s.  to  8-9.  per  kilo. 

When  artificial  silk  can  be  placed  on  the  market  at  8s.  to  10s.  per  kilo — and  this  would 
appear  likely  at  no  distant  date,  owing  to  the  early  lapse  of  the  principal  patents — a  new 
era.  of  activity  for  this  industry  will  begin,  as  it  will  become  possible  to  displace  not  only 
tussah  silk  but  also  all  the  heavily  loaded  silks  of  the  fabrics  commonly  used  more  especially 
as  train  silk. 

The  most  authoritative  information  indicates  that  the  cost  of  manufacture  of  Char- 
donnet silk  should  not  now  exceed  9s.  6rf.  per  ki!o,  allowing  for  the  recovery  of  most  of  the 
alcohol  and  ether  (this  seems  to  be  effected  successfully  by  passing  the  air  containing 
them  through  higher  alcohols  such  as  butyl  or  amyl,  or  by  washing  the  fresh  fibre  on  spools 
with  water  ;  see  also  Note,  p.  700).  while  that  of  the  Glanzstoff  (Elberfeld)  artificial  silk 
should  ultimately  fall  to  6s.  to  7s.  per  kilo,  and  that  of  viscose  silk  to  5s.  to  6s. 

These  figures  explain  the  almost  fantastic  profits  realised  by  the  principal  factories, 
which  have  sold  concessions  and  rapidly  redeemed  the  cost  of  their  plant  and  are  now 
enabled  to  pay  dividends  of  50  per  cent.,  100  per  cent.,  or  even  more. 


CHEMICAL  TESTS  FOR  RECOGNISING  DIFFERENT 
TEXTILE  FIBRES 

The  commonest  test  for  distinguishing  animal  from  vegetable  fibres  consists  in  burning 
a  thread  ;  the  former  burn  slowly,  giving  an  odour  of  burnt  nails  and  forming  a  round 
granule  of  carbon  at  the  point  of  the  thread  where  combustion  ceases,  while  vegetable 
lihres  burn  more  rapidly,  are  converted  into  ash  and  give  but  little  smell,  which  'recalls 
that  of  burnt  paper.  Other  reactions  are  as  follow : 

Boiling  10  per  cent,  caustic  potash :  Hemp,  jute,  flax,  cotton,  and  artificial  silk  are 
insoluble  and  are  not  coloured  (excepting  jute,  which  becomes  yellow)  ;  wool,  silk,  and 
artificial  gelatine  silk  dissolve  after  a  few  minutes. 

Cold  cone,  sulphuric  acid  (after  2  hours) :  Hemp,  flax,  jute,  cotton,  unweighted  silk, 
and  artificial  silk  are  soluble  or  almost  so,  hemp  being  coloured  brownish  yellow,  jute 


704  ORGANIC    CHEMISTRY 

brownish  black,  and  mercerised  cotton  yellowish,  while  the  rest  remain  colourless.  Wool 
and  weighted  silk  do  not  dissolve. 

Boiling  zinc  chloride  (60°  Be.)  :  Flax,  hemp,  jute,  and  cotton  are  insoluble,  jute  alone 
being  coloured  a  faint  brown.  Wool,  silk,  and  artificial  silk  are  soluble. 

Schweitzer's  reagent  (see  p.  503),  after  2  hours  in  the  cold,  dissolves  more  or  less  completely 
(better  if  freshly  prepared),  hemp,  flax,  jute.,  cotton,  unweighted  silk  (in  less  than  an  hour) 
and  artificial  silk.  Wool  is  insoluble. 

Milton's  reagent  (solution  of  mercury  in  an  equal  weight  of  nitric  acid  of  sp.  gr.  1-41, 
first  cold,  then  heated  gently,  diluted  with  double  the  volume  of  water  and  decanted  after 
standing) :  Cotton,  flax,  hemp,  and  Chardonnet-Lehner  artificial  silk  are  not  coloured  ; 
jute  is  turned  yellow,  wool  and  pure  silk  violet-red,  and  weighted  silk  and  tussah  silk 
ochre-red. 

Cone,  aqueous  fuchsine  (just  decolorised  with  NaOH) :  Wool  and  silk  arc  coloured  red, 
while  cotton  and  flax  remain  uncoloured. 

Silver  nitrate  solution  :  Wool  is  coloured  violet  to  black,  while  cotton  and  flax  are  not 
coloured. 

lodo-zinc  chloride  solution  (1  part  iodine  +  SKI  +  30  fused  ZnCL  +  14  water)  in  the 
cold  :  Flax,  hemp,  cotton,  and  artificial  silk  are  coloured  violet-brown  (mercerised  cotton 
almost  black)  :  jute,  wool,  and  tussah  silk  are  turned  yellowish  and  with  time  become 
colourless  ;  true  silk  is  not  coloured. 

Lowe's  reagent  (shake  10  grms.  copper  sulphate,  100  c.c.  of  water,  and  5  grins,  of  pure 
glycerine  and  add  caustic  potash  in  quantity  scarcely  sufficient  to  redissolve  the  precipitate 
formed)  in  the  cold  dissolves  only  natural  silk  and  is  used  for  the  quantitative  separation 
of  natural  from  artificial  silk. 

Diphenylamine  sulphate(l  grm.  in  100  c.c.  cone.  H2SO4)  in  the  cold  :  Hemp,  flax,  jute, 
and  tussah  silk  are  dissolved,  giving  more  or  less  intense  brown  colorations  (flax  dissolves 
less  easily  and  is  less  coloured)  ;  cotton  and  wool  dissolve  with  yellow  coloration  ;  silk 
dissolves,  giving  a  colourless  or  faintly  brown  solution  ;  artificial  silk  assumes  an  intense, 
characteristic  blue  colour. 

Molisch's  reagent  (obtained  by  dissolving  15  grms.  of  n-naphthol  in  100  c.c.  alcohol)  : 
the  fibre,  dyed  or  otherwise,  is  first  purified  by  boiling  with  2  per  cent,  sodium  carbonate 
solution  and  washing  thoroughly  with  water.  One  centigramme  of  the  fibre  is  treated 
with  1  c.c.  of  water,  2  drops  of  Molisch's  reagent,  and  1  c.c.  of  cone.  HaSOj  ;  all  the  vege- 
table fibres,  including  artificial  silk,  dissolve  with  a  violet-blue  coloration  ;  wool  is  insoluble 
and  is  coloured  reddish  ;  silk  is  dissolved,  giving  a  reddish  (or,  if  weighted,  an  intense  red) 
solution  ;  tussah  silk  dissolves,  yielding  a  yellowish  solution. 

Iodine  solution  (1  grm.  KI,  100  c.c.  H2O,  and  excess  of  iodine)  :  0-1  grm.  of  the  white 
fibre,  purified  as  above  with  sodium  carbonate,  is  treated  with  a  few  drops  of  iodine  solution, 
the  excess  being  removed  by  means  of  filter-paper  ;  hemp,  flax,  cotton,  and  artificial  silk 
are  coloured  blackish  brown  (flax  more  intensely  than  hemp  and  unmercerised  cotton 
reddish  brown)  ;  wool  and  silk  become  orange-yellow  and  jute  reddish  yellow. 


It  is  often  of  importance  for  trade  or  fiscal  purposes  to  determine  quantitatively  sub- 
stances extraneous  to  textile  fibres  in  order  to  ascertain  their  commercial  weight.  This 
is  determined  by  means  of  the  so-called  conditioning. 

In  conditioning,  which  is  now  carried  out  officially,  the  moisture  is  estimated  by  drying 
in  an  oven  with  automatic  regulation,  and  thus  determining  very  exactly  the  amount  of 
dry  fibre  (absolute  weight)  remaining  after  silk  has  been  heated  at  120°  or  wool  and  cotton 
at  105°  to  110°.  To  obtain  the  commercial  weight  the  absolute  weight  is  increased  by  the 
normal  moisture  which  the  hygroscopic  fibre  absorbs  from  the  air,  this  being  fixed  at 
12  per  cent,  for  flax  and  hemp,  13-75  per  cent,  for  /«£e,s8-5  per  cent,  for  cotton,  18-25  per 
cent,  for  combed  wool,  17  per  cent,  for  spun  and  carded  wool,  and  11  per  cent,  for  xilk 
(120°)  ;  also  the  amount  of  dressing  in  the  fibre  must  be  deducted.  It  is,  however,  to  be 
noted  that  usually  wool  has  only  11  per  cent.,  silk  8-5  per  cent.,  and  cotton  7-5  per  cent,  of 
moisture  when  in  ordinary  surroundings. 

Dressing  :   5  grms.  of  the  fabric  are  well  washed  with  water,  wrung  out,  boiled  for 


DYEING    AND    PRINTING    TESTS 

15  minutes  in  150  c.c.  of  0-1  per  cent,  sodium  carbonate  solution,  washed  in  water  and 
rubbed — all  the  fibres  being  grasped — heated  to  boiling  with  150  c.c.  of  1  per  cent.  HC1 
and  kept  on  the  steam-bath  for  15  minutes,  again  washed  and  rubbed,  boiled  for  15  minutes 
with  distilled  water,  washed  with  cold  water,  pressed  in  a  towel,  washed  two  or  three  times 
with  alcohol  and  two  or  three  times  with  ether,  dried  in  the  air  and  then  in  an  oven  to 
constant  weight. 

The  loss  in  weight,  after  allowing  for  the  moisture  (see  preceding  determination)  repre- 
sents the  dressing  and  colouring-matter  ;  the  latter  is  almost  always  a  negligible  quantity, 
but  in  the  case  of  black  may  be  taken  at  about  0-3  per  cent,  of  the  weight  of  the  pure 
fibre. 

Mixed  Cotton  and  Wool  Fabric.  After  the  moisture  and  dressing  have  been  determined, 
the  cotton  may  be  estimated  and  the  wool  deduced  by  difference  or  vice  versa.  The  cotton 
is  determined  by  boiling  3  grms.  of  yarn  or  fabric  with  100  c.c.  of  10  per  cent,  caustic 
potash  solution,  the  wool  quickly  dissolving  ;  the  residue  is  well  washed  with  water,  boiled 
for  15  minutes  with  distilled  water,  squeezed,  washed  with  alcohol  and  with  ether,  and 
finally  heated  at  100°  to  105°  until  of  constant  weight,  representing  the  dry  cotton.  In 
reducing  this  to  percentage,  account  is  taken  of  the  moisture  and  of  the  dressing.  If, 
however,  the  wool  is  to  be  determined  directly  and  the  cotton  by  difference,  3  grms.  of 
the  fabric  are  boiled  for  15  minutes  with  0-1  per  cent,  sodium  carbonate  solution,  rinsed 
in  water,  well  wrung  out  in  a  towel  and  left  for  two  hours  in  cold  sulphuric  acid  of  58? 
Be.  ;  it  is  then  washed  in  a  large  amount  of  water — care  being  taken  that  the  remaining 
wool  does  not  become  heated — boiled  for  15  minutes  in  distilled  water,  squeezed,  washed 
with  alcohol  and  with  ether,  and  dried  at  100°  to  105°  until  of  constant  weight,  which 
represents  the  dry  wool. 

Mixed  Cotton  and  Silk  Fabric.  After  the  moisture  and  dressing  have  been  determined 
(see  above),  the  same  piece  of  dried  fabric  is  immersed  for  a  minute  in  a  boiling  solution  of 
zinc  chloride  (60°  Be.)  and  washed  first  with  water  slightly  acidified  with  HNO3  and  then 
with  pure  water  until  the  wash  water  gives  no  zinc  precipitate  with  ammonium  sulphide, 
the  remaining  cotton  being  washed  with  alcohol  and  with  ether  and  dried  at  100°  to  105° 
until  of  constant  weight ;  the  silk  is  calculated  by  difference.  In  the  case  of  tussah  silk, 
the  action  of  the  zinc  chloride  is  prolonged  somewhat.  In  order  that  no  loss  may  occur 
with  a  heavily  weighted  silk,  the  dressing  is  eliminated  by  means  of  sodium  carbonate 
alone,  treatment  with  hydrochloric  acid  being  omitted. 

Mixed  Wool  and  Silk  Fabric.  The  silk  is  dissolved  in  zinc  chloride  and  the  residual 
wool  weighed,  the  silk  being  determined  by  difference  (see  above). 

Natural  and  Artificial  Silk  Fabric.  The  natural  silk  is  dissolved  in  Lowe's  reagent 
(see  above). 

Cotton  and  Linen  Fabric.  As  a  rule  the  different  fibres  can  be  separated  by  hand,  but 
when  this  is  not  possible  the  cotton  (after  the  moisture  and  dressing  have  been  deter- 
mined on  the  same  piece  of  fabric)  is  dissolved  by  immersing  the  tissue  for  1  to  2  minutes 
in  concentrated  sulphuric  acid  ;  the  fibre  is  washed  well  with  water — being  rubbed  mean- 
while— then  with  water  and  ammonia,  and  again  with  water,  the  linen  remaining  being 
dried  and  weighed.  The  cotton  is  obtained  by  difference. 

Different  Artificial  Silks.  Those  from  nitrocellulose  (de  Chardonnet,  Lehner,  &c.) 
contain  traces  of  nitro-derivatives  and  with  diphenylamine  and  sulphuric  acid  give  a  blue 
reaction,  which  is  not  shown  by  other  silks.  P.  Maschner  (1910)  distinguishes  different  silks 
by  treatment  with  concentrated  H2SO4  ;  that  from  nitrocellulose  colours  the  liquid  a  faint 
yellow  only  after  40  to  60  minutes  ;  amrnoniacal  copper  oxide  silk  is  coloured  yellow  or 
brownish  yellow  immediately,  while  the  liquid  becomes  brownish  yellow  after  40  to  60 
minutes  ;  viscose  is  at  once  coloured  carmine-red,  the  liquid  turning  brown  after  40  to 
60  minutes.  The  fibres  dissolve  after  about  20  minutes  and  then  carbonise. 

DYEING  AND  PRINTING  TESTS   ON  TEXTILE   FIBRES 

Of  some  importance  are  the  tests  which  admit  of  the  classification  of  colouring-matters 
according  to  their  basic,  acid,  neutral,  or  mordant  character.  To  this  end,  dyeing  or 
printing  tests  are  made  on  a  small  scale  with  wool  and  cotton  (see  also  p.  671  et  seq.).  Tests 
made  with  colorimeters,  which  compare  the.  intensities  of  coloration  of  solutions  in  tubes 
of  equal  lengths  or  vessels  of  equal  thickness,  are  of*little  practical  value.  Hence  to  ascertain 
II  45 


Fio.  444. 


706 

the  dyeing  power  of  any  commercial  product,  the  latter  is  compared  with  a  standard 
colouring-matter  by  weighing  out  equal  quantities  (0-1  to  1  grm.  per  litre  of  water)  of  the 
two,  and  dyeing  equal  weights  of  wool,  cotton,  or  silk  fabric  with  definite  volumes  of  the 
more  or  less  diluted  solutions.  The  quantity  of  dye  used  is  always  referred  to  the  weight 
of  the  fabric,  independently  of  the  dilution  of  the  bath  ;  this  is  especially  the  case  with 
wool  (0-1  per  cent,  of  the  dye  for  pale  colours  and  2  to  4  per  cent,  for  dark  colours).  The 
dyeing  tests  are  made  on  1  to  2  grms.  of  wool  or  cotton  yarn  or  tissue  in  glass  or  porcelain 
beakers  of  150  to  250  c.c.  capacity,  these  being  heated  in  a  bath  of  concentrated  sodium 
sulphate  solution  or  of  glycerine  giving  a  temperature  of  101°  to  102°  in  the  dye-bath  (see 
Fig.  444). 

If  the  bath  retains  much  colour  after  the  dyeing,  a  second  portion  of  the  textile  is  dyed 
without  adding  fresh  dye.  If  the  cotton  is  raw  it  must  first  be  boiled  for  an  hour  in  a 
0-5  per  cent,  caustic  soda  solution,  and  then  thoroughly  rinsed  with  water.  If  light 
colours  are  used,  the  cotton  is  also  bleached  in  calcium  hypochlorite  solution  (less  than 
1°  Be.)  at  25°  to  35°  for  an  hour,  washed  Avith  water,  immersed  in  a  1  per  cent,  sodium 

bisulphite  bath  (antichlor),  and  well 
rinsed  in  water.  Wool,  if  impure,  is 
heated  at  60°  for  10  minutes  with  a 
solution  containing  0-5  per  cent,  of  soap 
and  0-1  per  cent,  of  sodium  carbonate, 
and  then  well  rinsed  with  water.  Also 
silk,  if  not  already  discharged,  is  washed 
with  hot  soap  sohition. 

The  comparative  dyeing  tests  should 
be  made  on  equal  quantities  of  textile  fibre 
wetted  uniformly  before  introduction  into 
the  dyeing  bath.  Silk  is  dyed  like  wool,  but 

the  bath  is  made  less  acid  and  the  temperature  rather  lower.  W  ool  is  dj^ed  in  an  aqueous 
bath  containing  10  to  15  per  cent,  of  sodium  sulphate  and  5  per  cent,  of  sulphuric  acid 
(or  6  to  7  per  cent,  of  sodium  bisulphate  —  the  German  Weinsteinpreparat  —  in  place  of  the 
sulphuric  acid)  calculated  on  the  weight  of  fibre  ;  the  bath  is  stirred  continually  with  a 
glass  rod  and  heated  gently  to  boiling,  being  kept  slowly  boiling  for  20  to  30  minutes  ; 
the  wool  is  then  rinsed  and  dried  either  in  the  air  or  in  a  water-oven.  The  above  procedure 
is  followed  more  especially  for  acid  dyes  ;  with  basic  dyes,  one-quarter  of  the  amount  of 
sulphuric  acid  is  sufficient.  When  wool  is  dyed  with  acid  dyes,  it  is  not  merely  necessary 
to  add  to  the  dye-bath  the  quantity  of  sulphuric  acid  required  to  liberate  the  acid  residue 
of  the  dye  so  that  this  can  be  fixed  on  the  wool,  but  in  order  that  the  latter  may  be  dyed 
intensely  and  well,  20  to  30  times  the  theoretical  amount  of  sulphuric  acid  must  be  added 
(E.  Knecht,  1888).  With  mordant  dyes,  the  wool  is  mordanted  with  3  per  cent,  of  potassium 
dichromate  and  2-5  per  cent,  of  cream  of  tartar  (on  the  weight  of  wool)  and  about  100  times 
the  weight  of  water,  heating  gradually  to  boiling  and  maintaining  this  for  nearly  an  hour, 
the  water  evaporated  being  gradually  replaced  ;  the  wool  is  then  rinsed  and  dyed  in  the  dye- 
bath,  which  contains  a  little  acetic  acid(l  per  cent,  on  the  fibre),  and  is  mixed  continuously 
and  brought  slowly  to  the  boil,  boiling  being  maintained  for  about  an  hour. 

Knecht  and  Hibbert  (1903-1905)  determine  the  concentration  of  the  colouring-matters 
in  the  different  solutions  by  reduction  with  standard  titanium  trichloride  solution  ;  crystal 
violet,  for  example,  fixes  2H,  giving  the  colourless  leuco-derivative. 

Cotton  is  dyed  with  substantive  dyes  in  more  concentrated  baths  (50  of  water  to  1  of 
cotton)  containing  30  to  50  per  cent,  of  sodium  chloride  or  sulphate  and  1  to  2  per  cent. 
of  sodium  carbonate  (on  the  fibre)  ;  this  is  heated  slowly  and  kept  boiling  for  30  to  40 
minutes  ;  in  general  the  bath  is  not  exhausted  and  can  be  used  for  a  second  portion  of 
cotton.  In  the  case  of  sulphur  colours,  20  to  30  per  cent,  of  sodium  sulphide  are  added  to 
the  bath  and  in  some  cases  2  to  3  per  cent,  of  glucose,  and  during  the  dyeing  the  cotton 
is  kept  immersed  and  out  of  contact  with  the  air.  Wlfen  basic  colour  ing  -matters  are  used 
the  cotton  is  previously  mordanted  with  2  to  4  per  cent,  of  tannin  dissolved  in  water, 
being  left  in  contact  with  this  solution  for  6  to  7  hours  (overnight)  at  50°  to  60°  (the  tannin 
is  fixed  more  slowly  in  the  cold)  ;  the  cotton  is  then  wrung,  immersed  for  10  minutes  in  a 
bath  containing  2  per  cent,  of  tartar  emetic  (antimony  potassium  tartrate)  at  40°,  rinsed 
with  water  and  dyed  in  the  -tepid  (30°  to  40°)  dye-bath  for  20  to  30  minutes. 


FASTNESS    TESTS  707 

Dyeing  on  a  large  scale  is  carried  on  under  the  same  conditions,  but  the  calculations 
are  made  on  a  longer  time,  and  great  precautions  are  taken  in  the  moving  of  the  fibre  and 
in  raising  the  temperature,  so  as  to  obtain  uniformity.  For  dark  colours,  the  tannin  is 
fixed  with  ferric  nitrate  instead  of  with  tartar  emetic.  Industrial  dyeing  apparatus  is 
shown  more  in  detail  later  (p.  717). 

PRINTING  TESTS.  The  object  of  printing  is  to  colour  the  fabric  or  yarn  in  a  definite 
pattern  or  with  different  colours,  part  of  the  fibre  being  possibly  left  unaltered.  In  the 
first  rudimentary  printing  processes,  the  fabric  was  printed  with  resin  or  a  kind  of  cement, 
the  uncovered  parts  being  dyed  as  usual  and  the  preserving  substance  subsequently 
removed.  It  is  now  usually  regarded  as  preferable  to  stamp,  i.e.  to  print,  on  the  fabric 
or  yarn  the  colour  mixed  with  thickening  (gum,  dextrin,  gum  tragacanth,  &c.)  by  means 
of  metal  rolls  on  which  the  desired  pattern  is  engraved.  The  engraved  roll  is  coated  with 
the  pasty  colour  by  rotating  against  a  rubber  or  cloth  roller  (furnisher),  one-half  of  which 
dips  in  a  vessel  containing  the  thickened  colour  ;  a  knife  (doctor)  is  arranged  so  as  to 
scrape  the  excess  of  colour  from  the  metal  roll,  and  the  yarn  or  fabric  then  passes  over  the 
latter  under  pressure.  In  order  to  fix  the  colour  and  prevent  it  from  spreading,  the 
fibre  is  subjected  for  30  to  60  minutes  to  the  action  of  steam  at  about  105°  (see  p.  731). 
By  this  means  the  colour  is  fixed  without  immersing  the  printed  fibre.  The  latter  is 
subsequently  washed  with  an  abundance  of  cold  water  (or  with  tepid  soap  and  water), 
which  removes  all  excess  of  colour  and  thickening  agent.  In  other  cases  similar  effects 
are  obtained  by  dyeing  uniformly  in  the  ordinary  way  and  then  printing  on  the  dyed  fabric 
reagents  which  decolorise  (corrode)  the  dye  at  the  points  of  contact.  Sometimes  other 
colours  are  introduced  with  the  corroding  agent,  so  that  the  white  parts  are  dyed  a  lighter 
or  darker  shade  or  a  different  colour  from  the  foundation. 

A  kilo  of  thickened  colour  for  printing  wool  black — the  wool  having  been  previously 
subjected  to  slight  chlorination  to  make  it  take  up  the  colouring-matter  better  (by  immersion 
in  a  cold  calcium  hypochlorite  bath  at  0-5°  Be.  and  then  in  very  dilute  HC1,  washing,  and 
drying) — may  be  obtained  as  follows:  750  c.c.  of  water,  100  grms.  of  gum,  and  100  grms.  of 
British  gum  (dextrin)  are  heated  in  a  jacketed  vessel  by  means  of  indirect  steam  and  kept 
well  mixed,  60  grms.  of  anthracite  black  E  G  and  10  grms.  of  milling  yellow  O  (and,  in 
some  cases,  8  grms.  of  anthracene  acid  brown  R)  being  added.  When  the  paste  is  boiled 
uniform,  it  is  allowed  to  cool,  and  before  it  is  used  a  solution  containing  80  c.c. 
of  water,  120  c.c.  of  acetic  acid  (6°  Be.),  and  40  grms.  of  sodium  chlorate  is  well 
mixed  in. 

For  printing  cotton  textiles,  colours  are  used  which  form  insoluble  lakes  with  tannin 
or  metallic  oxides  ;  such  are  basic  and  mordant  colouring-matters  (alizarin,  &c.).  The 
former  are  dissolved  in  acetic  acid  and  tannin  (or  a  solution  of  50  parts  of  tannin,  50  of 
water,  and  5  of  tartaric  acid)  and  the  latter  (alizarin,  &c.)  in  chromium  (or  iron,  aluminium, 
&c.)  acetate,  dextrin,  gum,  &c.,  being  added  in  either  case.  Fabrics  treated  with  tannin, 
after  being  steamed  at  the  ordinary  pressure  and  before  being  washed,  are  passed  into 
a  bath  containing  5  to  10  grms.  of  tartar  emetic  per  litre  at  60°. 

FASTNESS  TESTS.  The  fastness  of  a  colour  is  only  relative  and  must  be  considered 
with  reference  to  the  purposes  for  which  the  dyed  fibre  is  required  ;  for  example,  it  would 
be  superfluous  to  require  fastness  against  light  in  dyed  fibres  or  fabrics  to  be  used  for 
stockings,  linings,  &c.  The  dyed  specimen  is  mixed  with  similar  undyed  fibre  and  subjected 
to  the  following  tests,  as  required.  Mordanted  colours  answer  all  these  tests  fairly  well, 
but  in  other  cases  more  or  less  of  the  colour  is  given  up. 

Fastness  against  Water.  The  sample  is  immersed  in  50  times  its  weight  of  cold  water 
for  12  hours  or  for  1  hour  in  water  at  60°  to  70°  (and  is  left  to  cool  in  the  bath)  and  is 
then  dried  in  the  oven.  Note  is  taken  of  the  colour  assumed  by  the  water  and  by  the 
white  fibre,  especially  where  the  latter  comes  into  contract  with  the  dyed  fibre. 

Fastness  against  Soap,  Alkali,  and  Washing.  The  skein  of  white  and  dyed  fibre  is 
immersed  in  50  times  its  weight  of  an  aqueous  solution  containing  10  grms.  of  Marseilles 
soap  and  10  grms.  of  soda  per  litre.  The  bath  is  heated  at  60°  for  30  minutes  and  allowed 
to  cool,  the  skein  being  then  removed,  well  rinsed,  and  dried.  The  changes  in  colour  of 
the  bath  and  the  white  and  dyed  fibres  are  observed. 

Fastness  against  Milling.  This  test  is  carried  out  with  a  soap  and  soda  solution,  of 
double  the  above  concentration,  at  40°,  the  skein  being  continually  rubbed  between  the 
hands  for  30  minutes,  and  then  well  washed  and  dried  in  the  overy  Colours  fast  to-  milling 


Y08  ORGANIC    CHEMISTRY 

should  not  soil  the  white  portion  of  the  skein  and  should  give  up  only  a  minimal  amount  of 
colour  to  the  bath. 

Fastness  against  Bleach.  If  the  colour  is  on  wool  or  silk  it  is  immersed  in  a  2  per  cent, 
sodium  bisulphite  bath  acidified  at  the  moment  of  using  with  a  few  drops  of  hydrochloric 
acid,  and,  after  30  minutes,  washed  and  dried.  When  the  colour  is  on  cotton,  the  test  is 
made  with  a  calcium  hypochlorite  bath  at  0-5°  Be.  for  half  an  hour. 

Fastness  against  Scouring.  Indigo,  Turkey-red,  and  all  basic  dyes  on  cotton  mordanted 
with  tannin,  even  when  dry,  give  up  a  little  colour  to  a  white  handkerchief  with  which 
they  are  scoured.  Other  dyes  should  not  soil  the  white. 

Fastness  against  Acid.  The  test  is  carried  out  for  an  hour  with  1  per  cent,  sulphuric 
acid  at  60°  to  70°. 

Fastness  against  Perspiration.  In  some  cases  this  test  is  made  with  a  1  per  cent,  acetic 
acid  solution  for  30  minutes  at  60°,  the  skein  being  dried  at  60°  under  slight  pressure, 
without  rinsing  and  after  thorough  rubbing.  In  others,  an  alkaline  test  is  made — as  in 
testing  fastness  against  washing — but  the  unrinsed  skein  is  subsequently  scrubbed  and 
dried  at  60°  under  slight  pressure. 

Fastness  against  Ironing.  The  dyed  tissue  or  yarn  is  ironed  with  a  very  hot  iron  (1 30° 
to  140°),  note  being  taken  whether,  after  cooling  and  exposure  to  the  air  for  15  minutes, 
the  fabric  resumes  its  original  colour.  Many  colours  are  changed  by  ironing  hot,  but  return 
to  their  initial  state  in  the  cold. 

Fastness  against  Steaming.  The  yarn  is  placed  in  a  glass  tube,  through  which  steam 
at  110°  is  passed  for  two  or  three  minutes. 

Fastness  against  Light.  One  half  of  a  skein  of  yarn  or  of  a  strip  of  fabric  is  tightly 
enclosed  between  two  pieces  of  card,  while  the  other  half  is  left  free  ;  the  whole  is  then 
hung  in  the  open  air  exposed  to  the  sun  and  weather.  For  pale  colours,  an  exposure 
of  at  least  two  days,  and  for  dark  colours,  one  of  at  least  four  days,  is  necessary  in  summer, 
while  in  winter  or  in  cloudy  or  rainy  weather  (the  skein  must  be  sheltered  from  rain), 
at  least  double  or  even  treble  these  exposures  are  necessary.  The  covered  and  uncovered 
portions  are  subsequently  compared. 

Fastness  of  the  Dressing  against  Rain.  A  few  drops  of  water  are  sprinkled  on  the  fabric, 
especially  finer  woollen  ones,  and  after  exposure  to  the  air  it  is  noted  whether  the  drops 
have  left  faint  spots;  In  some  cases  the  fabric  is  scratched  with  the  thumb-nail ;  a  paler 
streak  should  not  result.  This  test  is  not  applied  to  cotton  fabrics  strongly  dressed,  since 
the  nail  will  sometimes  detach  the  dressing  itself. 

THEORY  OF  DYEING.  The  phenomenon  of  dyeing  was  at  one  time  thought  to  be 
due  to  the  porosity  and  capillarity  of  fibres  which  were  thus  enabled  to  absorb,  and  become 
impregnated  with,  dyes.  The  possibility  of  chemical  combination  between  the  dye  and 
the  fibre  was  regarded  as  excluded,  it  being  asserted  that  in  such  case  the  fibre  would 
undergo  marked  change.  The  different  colouring  powers  of  substances  were  explained 
as  due  to  different  molecular  magnitudes.  Even  at  the  beginning  of  last  century,  in 
Chreveul's  time,  these  ideas  prevailed,  and  only  in  the  case  of  mordant  dyeing  was  any 
chemical  fixation  of  the  dyestuff  assumed.  Later  on,  Bergman,  J.  Persoz,  &c.,  arrived  at 
a  purely  chemical  conception  of  the  phenomenon  of  dyeing.  But  when  in  1885  substantive 
cotton  dyestuffs  of  almost  neutral  character  made  their  appearance,  the  chemical  theory, 
which  was  based  mainly  on  the  basic  or  acidic  nature  of  the  dyestuffs,  was  in  some  degree 
shaken.  Many  then  accepted  a  new  theory  in  harmony  with  the  osmotic  phenomena  of 
solutions,  the  more  readily  because  no  definite  and  constant  relation  between  the  amount 
of  fibre  and  that  of  dyestuff  combined  had  been  established.  The  chemical  theory  was, 
and  is  still,  however,  upheld  by  many  authorities  on  the  subject,  more  particularly  by 
Noelting,  by  Knecht,  and  by  Vignon,  who  have  pointed  out  that  alloys  form  well  charac- 
terised compounds  which  exhibit  no  definite  chemical  relations  between  the  components 
and  may  be  regarded  as  true-solid  solutions  of  one  substance  in  excess  of  the  other.  Further, 
they  were  able  to  show  that  silk  and  wool,  in  combining  with  colouring-matters,  set  free 
the  acid  united  with  the  base  of  the  dyestuff,  this  acid  being  found  in  the  dye-bath.  Also, 
with  certain  acid  dyestuffs  (e.g.  naphthol  yellow),  Knecht  and  Appleyard  found  a  constant 
relation  between  fibre  and  dyestuff. 

Jacquemin  asserts  that  if  there  were  no  question  of  chemical  combination,  the  dry 
dyed  tissue  should  have  the  colour  of  the  dry  colouring-matter,  whereas  it  has  the  same 


THEORYOFDYEING  709 

colour  as  the  dissolved  colouring-matter.  Nietzki  finds  that  with  certain  highly  basic 
colours  (e.g.  methyl  green),  wool  cannot  of  itself  displace  the  mineral  acid  of  the  colouring 
base,  the  addition  of  ammonia  being  necessary  ;  while,  with  the  same  colouring-matters  the 
more  markedly  acidic  silk  is  dyed  without  any  addition. 

An  interesting  fact,  which  supports  the  chemical  theory,  is  that  the  base  of  rosaniline 
is  colourless  and  becomes  red  (fuchsine)  only  when  converted  into  a  salt  with  HC1 ;  a 
similar  change  is  produced  if  wool  is  immersed  in  a  colourless  rosaniline  (base)  bath,  the 
wool  being  dyed  red  owing  to  the  formation  of  a  salt.  If  the  dyeing  is  effected  directly 
by  rosaniline  hydrochloride,  the  bath  ultimately  contains  the  hydrochloric  acid  which  is 
displaced  by  the  acid  of  the  wool  fibre  (Jacquemin  and  Knecht,  1888). 

Moreover  Richard  (1888),  Vignon  (1890),  and  Nietzki  (1890)  showed  that  silk  and  also 
wool  are  active  both  towards  acids  and  towards  bases,  so  that  in  chemical  characters 
they  are  comparable  with  the  amino-acids.  The  fibre  may  even  be  replaced  by  albumin, 
which  is  dyed  by  the  same  dyestuffs  as  wool,  &c. 

According  to  W.  Suida  (1907)  the  dyeing  of  wool  is  accompanied  by  liberation  of  the  base 
of  the  dyestutt'  which  combines  (or  forms  salts)  with  the  textile  fibre,  the  latter  function- 
ing as  a  polybasic  acid  in  virtue  of  its  guanidyl  and  irnidazole  groups.  Also  Vignon  showed 
that  when  wool  and  silk  are  dyed  with  basic  or  acid  colouring-matters  heat  is  developed, 
so  that  the  dyeing  may  be  regarded  as  a  true,  exothermic  chemical  reaction.  According 
to  Vignon  cotton  is  not  dyed  directly  by  basic  or  acid  dyestuffs  (which  are  usually  salts) 
since  it  has  not  the  reactive  force  to  decompose  them  ;  but  if  it  is  previously  oxidised 
or  animated,  it  fixes  these  dyestuffs  partially  with  development  of  heat.  Further,  the 
difference  in  fastness  against  light  of  the  same  colouring-matter  (e.g.  methylene  blue) 
fixed  on  cotton  (with  tannin)  and  on  wool  or  silk  would  appear  to  favour  the  chemical 
hypothesis  of  the  phenomenon  of  dyeing. 

In  1889  O.  N".  Witt  advanced  a  new  theory,  which  explains  also  the  dyeing  of  cotton 
with  substantive  and  mordant  dyes.  According  to  Witt,  dyeing  consists  merely  of  a 
solution  of  the  colouring-matter  in  the  fibre,  analogous  to  that  of  solution  of  coloured 
metallic  oxides  in  glass.  So  that  the  colouring-matter  passes  from  a  liquid  solvent  (dye- 
bath)  to  a  solid  one — the  fibre  itself — just  as  occurs  with  alloys  or  in  the  extraction  with 
ether  of  a  substance  dissolved  in  another  solvent  in  which  it  is  less  soluble  than  in  ether — 
assuming  that  the  two  solvents  are  mutually  insoluble. 

Dyeing  on  mordants  is  similarly  explained  as  due  to  the  solvent  properties  of  the  fibres 
for  the  metallic  salts,  these  then  fixing  the  colouring-: Batter  from  the  dye-bath.  The 
dyeing  of  cotton  with  substantive  dyestuffs  is  regarded  as  the  result  of  the  marked  solvent 
power  of  cotton  (cellulose)  for  these  dyes.  In  support  of  his  theory,  Witt  cites  the  fact 
that  silk  dyed  with  fuchsine  gives  up  its  colour  to  alcohol,  which  is  a  better  solvent  for 
fuchsine  than  is  silk,  while  if  the  alcohol  is  then  diluted  with  water,  the  colour  is  again 
fixed  by  the  silk. 

To  this  observation  Knecht  (1902)  made  the  reply  that,  with  substantive  colouring- 
matters,  lanuginic  and  sericinic  acids  form  insoluble  lakes,  i.e.  true  compounds,  while 
with  fuchsine  they  form  lakes  soluble  in  alcohol  ;  it  is  therefore  to  be  supposed  that  the 
fuchsine  extracted  by  Witt  with  alcohol  is  in  reality  the  soluble  lake  formed  by  the  fuchsine 
with  the  components  of  the  fibre.  Rosenstiehl  (1894),  Reisse  (1896),  and  Gillet  (1898), 
after  various  quantitative  dyeing  tests,  decided  in  favour  of  the  chemical  hypothesis. 

In  1894-1895  Georgievics  advanced  a  number  of  arguments  in  favour  of  a  purely 
mechanical  theory  of  dyeing  (his  predecessors  of  a  century  earlier  being  Hellot  and  Le 
Pileur  d'Apligny,  and  those  of  more  recent  times  Walter  Crum,  Spohn,  and  Hwass).  Com- 
paring the  latter  with  occlusion  of  gases  by  solids  or  with  the  mechanical  fixation  of  dyes 
on  sand  or  on  powdered  charcoal,  &c.,  he  maintained  that  colouring-matters  fixed  on  fibres 
have  the  same  properties  as  those  not  so  fixed,  and  that  there  can  hence  be  no  question 
of  a  chemical  reaction  (but  see  above,  Knecht's  experiment),  since  some  dyestuffs  fixed  on 
fibres  can  be  separated  by  mere  sublimation,  while  in  other  cases  (with  methylene  blue 
and  indigo  carmine)  the  coefficient  of  distribution  of  the  colouring- matter  in  the  fibre  and 
in  the  solution  is  constant.  According  to  Krafft  (1899),  dyeing  generally  consists  in  a 
deposition,  on  or  in  the  fibre,  of  adhesive  and  resistant  colouring  salts  in  the  colloidal 
state. 

Biltz  (1905)  has  succeeded  in  producing  true  dyeing  phenomena  by  replacing  the  textile 
fibre  (cotton)  by  aluminium  hydroxide  or  other  hydroxides  which  behave  as  hydrogels 


710  ORGANIC    CHEMISTRY 

(see  vol.  i,  p.  102)  towards  the  colouring-matter,  which  is  regarded  as  a  colloid  (ben/o- 
purpurin  and  sulphur  dyes).  Freundlich  and  Losev  (1907)  have  shown  that  carbon  not 
only  fixes  colouring -matters  but  decomposes  basic  colouring-matters,  fixing  the  coloured 
base  in  the  colloidal  state  and  leaving  the  acid  in  solution,  in  the  same  way  as  happens 
with  wool  or  silk.  Knecht  has  recently  (1909)  found  that  the  amount  of  colouring-matter 
fixed  by  charcoal  is  related  to  the  quantity  of  nitrogenous  matter  remaining  in  the  charcoal 
even  after  ignition,  so  that  here  a  true  chemical  reaction  occurs  ;  this  investigator  has  ako 
shown  that  colouring-matters  cannot  be  regarded  as  colloids,  since  'they  are  electrolytes 
and  diffuse  through  membranes. 

In  1909  Dreaper  and  Davis  demonstrated  that  basic  colouring-matters  are  fixed  in 
constant  quantity  on  calcined  sand,  and  in  increased  quantity  if  the  dye  solution  contains 
sodium  chloride.  Rosenstiehl  assumes  that  the  phenomenon  of  dyeing  is  explainable 
by  the  cohesive  force  between  the  colouring-matter  and  the  textile  fibre,  this  force  varying 
with  the  liquid  or  gaseous  medium  in  which  the  dyeing  takes  place  and  depending  on  or 
being  produced  by  the  osmotic  pressure  of  this  medium. 

According  to  Miiller  and  Slassarski  (1909)  dyeing  may  be  regarded  as  a  phenomenon 
of  adsorption  of  the  colouring- matter  by  the  colloid,  i.e.  the  textile  fibre.  There  is  hence 
not  chemical  combination,  but  fixation,  under  definite  conditions  (of  moisture  and  tem- 
perature). 

Mercerised  cotton  fixes  colouring-matter  on  account  of  its  more  marked  colloidal 
character.  The  process  of  fixation  or  adsorption  may  also  be  reversible  and  all  the  pheno- 
mena of  direct  dyeing  depend  on  the  relative  coefficient  of  adsorption  of  the  colloid  (fibre) 
for  the  colouring-matter.  Freundlich  and  Losev  and  Pelet-Jolivet  attribute  dyeing  to 
adsorption  because  the  fixation  of  the  colouring-matter  from  solution  by  any  textile  fibre 

or  x 

obeys  the  formula, —  =  K-C—  (where  —  denotes  the  ratio  between  the  quantity  of  colour 
m  n  v  m 

absorbed  and  the  weight  of  the  textile  fibre,  K  and  —  are  constants,  and  C  indicates  the 

n 

•final  concentration  of  the  colouring-matter),  which  also  regulates  the  adsorption  of  gases 
by  solid  substances  and  that  of  various  dissolved  substances  by  animal  charcoal.  It 
cannot,  however,  be  denied  that  certain  limited  chemical  processes  also  correspond  with 
this  formula,  and  that  many  phenomena  accompanying  dyeing  are  most  simply  explained 
chemically. 

Indeed,  W.  .1.  Miiller  and  Slassarski  (1910),  by  means  of  experiments  on  the  dyeirg 
of  "artificial  silk,  show  that  the  absorbed  colour  varies  in  quantity  with  the  chemical  pro- 
perties of  the  cellulose  (raw,  oxycellulose,  hydrocellulose). 

Every  hypothesis  is  supported  by  some  experimental  fact,  and  it  would  seem  that, 
according  to  the  nature  of  the  fibre,  of  the  colouring-matter,  and  of  the  dyeing  process, 
the  phenomenon  is  explainable  either  on  purely  physical  or  on  purely  chemical  grounds, 
but  more  generally  on  both. 

O.  Weber  (1891,  1899)  and  Gnehm  (1898)  explain  the  various  phenomena  of  dyeing 
in  the  following  way  :  (1)  Dyeing  on  mordanted  cotton  is  due  to  the  formation  of  lakes 
between  the  colouring-matter  and  the  mordant  precipitated  mechanically  on  the  cotton. 
(2)  Azo-  colouring-matters  formed  directly  on  the  fibre  (see  p.  658)  or  pigments  held  by  it, 
ultramarine,  cinnabar,  ochre,  Guinea  green,  &c.)  are  merely  precipitates  deposited  mechani- 
cally in  the  pores  of  the  fibre.  (3)  The  direct  dyeing  of  cotton  with  substantive  dyes 
consists  in  solution  of  the  colouring  salt  in  the  cell  juice,  and  the  marked  fastness  against 
washing  of  these  colours  on  cotton  is  due  to  their  slow  diffusion  with  the  juice  (Miiller- 
Jacobs  and  Weber).  (4)  Dyeing  of  tannin-mordanted  cotton  with  basic  or  indigo  colours 
is  a  true  mechanical  occlusion.  (5)  Direct  dyeing  of  wool  and  silk  and  other  animal 
fibres  with  basic  or  acid  colouring-matters  is  due  partly  to  mechanical  absorption,  and  partly 
to  chemical  combination,  of  the  colouring-matter  by  the  fibre.  (6)  The  dyeing  of  mordanted 
animal  fibres  is  explained  by  the  formation  of  insoluble  lakes,  partly  by  the  mordant 
fixed  chemically  by  the  fibre,  and  partly  by  that  fixed  mechanically  within  the  fibre,  but 
is  never  caused  by  combination  of  the  unchanged  fibre  with  the  colouring-matter. 

As  regards  the  mordanting  of  wool,  it  has  been  shown  that  when  this  is  boiled  with 
metallic  salts,  it  fixes  not  only  the  basic  part  but  also,  the  acid  part  of  the  salt  (only  of 
unstable  salts,  e.g.  sulphate  of  Al,  Cr,  Cu,  or  Fe,  and  not  sodium  sulphate  or  chloride);  the 
latter  part  is  eliminated  to  some  extent  by  water,  but  the  basic  part  is  fixed  more  stably. 


TEXTILE    MACHINERY 


FIG.  445. 


MACHINERY  USED   IN  DYEING  AND  FINISHING 
TEXTILE  FIBRES 

The  limits  of  this  treatise  do  not  allow  of  the  inclusion  of  a  complete  description  of  all 

the  machinery  used  in  works  where  textile  fibres  are  dyed  and  finished.     We  shall  hence 

confine  ourselves  to  illustrating  some  of  the  principal  washing,  dyeing,  and  dressing 

machines. 

WASHING  AND  PREPARATION.     At  the  dye-house,  textile  fibres  arrive  either  raw 

(cotton  and  wool  in  flock)  or  combed  (wool  in  skeins  or  tops)  or  spun  in  skeins  or  on  bobbins 
„»     (wool,  cotton,  silk),  or  more  commonly  woven  in  "pieces 
30  to  100  metres  long  and  60  to  140  cm.  wide  (woollen, 
cotton,  silk,  or  mixed  fabrics). 

Wool  is  sometimes  supplied  free  from  its  natural  fat 
(see  p.  681)  but,  whether  as  fabric  or  as  yarn,  contains 
the  fat  or  dressing  used  in  weaving  or  spinning. 

Cotton  is  still  in  the  raw  state,  and,  in  order  that  the 
colouring-matter  may  be  fixed  well,  it  is  subjected  to 
energetic  boiling  under  slight  pressure  with  water  and 
with  soda.  With  either  flock  or  skein  cotton,  this  treat- 
ment is  carried  out  in  large,  closed,  iron  or  copper  boilers 
(Fig.  445),  provided  with  pumps  or  steam-injectors  for 
circulating  the  liquid,  the  textile  material  not  being 
moved  as  it  might  be  damaged.  As  a  rule  the  boiler  is 
either  evacuated  or  freed  from  air  by  a  current  of  steam, 
since  air  damages  the  fibre  owing  to  formation  of  oxy- 
cellulose,  and  also  gives  dark  lye  ;  along  with  the  caustic 
soda,  vigorously  frothing  soap  (from  castor  oil,  for  example) 
is  introduced. 
The  washing  of  cotton  goods  to  rid  them  of  the  starch  with  which  the  weft  was  charged 

for  weaving  purposes  was  at  one  time  carried  out  by  heating  them  with  milk  of  lime,  but 

better  results   are  obtained  by  heating  with 

dilute  caustic  soda  solution  in  an  autoclave 

under  steam-pressure.     Nowadays  the  goods 

are  often  passed  through  a  lukewarm  bath  of 

diamalt    or    diastofor  (malt  extracts  rich    in 

diastase)   and  left   in    heaps   overnight,   the- 

starch   being  thus  transformed  into   soluble 

dextrin   and  maltose.      The   latter  products 

are   removed   by  thorough  rinsing  in  water : 

the  material  passes  between  the  two  rollers 

A  and  B  (Fig.  446)  into  the  water,  round  the 

roller  C,  up  between  A  and  B,  down  again  and 

so  on  until  it  reaches  the  middle,  where  it  is 

removed,  together  with  a  similar  piece  intro- 
duced at  the  other  end  of  the  machine  ;  the 

pieces  of  material  are  tied  end   to  end  and 

passed  through  this  washer  in  a  continuous 

length  ;  an  abundant  supply  of  water  enters 

the  vessel    at    D  and  is  drawn  off  through 

another  pipe. 

When  washed  the  goods  are  soured  with  a 

solution  of  sulphuric  acid  (0-5°  Be\),  either 

cold  or  tepid  (with  the  latter  the  action  is  very  rapid,  even  with  more  dilute  acid)  ;   the 

pieces   may  be  tied  together  in  cords  and  passed  through  this  solution  (*ee  Fig.  446). 

Bleaching  is  then  effected  in  a  clear  chloride  of  lime  bath  (0-5  to  0-75°  Be)  :  this  occupies 

some  hours  in  the  cold,  or,  if  the  liquid  is  lukewarm,  the  material  may  be  passed  continuously 

through   it   as   before.     Then   follows   rinsing    and   treatment   with   antichlor   (sodium 

bisulphite). 

Skeins  of  cotton  yarn  may  also  be  bleached  with  chloride  of  lime  in  an  apparatus  jvith 


Fia.'r446. 


712  ORGANIC    CHEMISTRY 

automatic  circulation  of  the  liquid,  as  is  shown  in  Fig.  445,  while  the  rinsing  may  be 
effected  in  rotating  machines  (Fig.  447),  where  each  skein  rotates  on  a  reel  and  all  the 
reels  rotate  horizontally  in  a  circulation  vessel,  a  water-spray  being  used  meanwhile. 

According  to  Pick  and  Erban  cotton  may  be  bleached  in  the  cold,  without  preliminary 
boiling  with  alkali,  by  means  of  sodium  hypochlorite  solution  mixed  with  sulphoricinate  ; 
in  this  way,  the  resistance  of  the 
fibre  is  retained  better,  while  time 
is  saved  (Ger.  Pat.  176,609  of 
1 906).  Cotton  or  cotton  and  wool 


FIG.  447. 


FIG.  448. 


fabrics  may  be  bleached  by  passing  them  repeatedly  into  a  sodium  permanganate  bath 
(0-6  to  0-7  per  cent,  of  the  permanganate  on  the  weight  of  ftbre)  until  the  bath  is  almost 
decolorised  and  the  fibre  turned  brown,  then  into  a  sodium  sulphite  or  sodium  nitrite  bath 
(0-6  to  0-7  per  cent,  on  the  fibre)  and  finally  into  sulphuric  acid  (4  per  cent,  on  the  fibre). 
The  Washing  of  skeins  of  wool  yarn  in  a  tepid  bath  (50°  to  60°)  is  carried  out  by  passing 

the  skein  for  a  minute  between  two  rolls  (Fig. 

448),     then    twisting     the     skein     and    again 


FIG.  449. 


FIG.  450. 


squeezing  it.  Subsequent  thorough  washing  with  water— in  the  vessel  shown  in  Fig.  447, 
for  example— renders  the  skein  of  wool  ready  for  dyeing.  In  all  these  operations  and  in 
those  which  follow,  woollen  yarns  are  treated  with  greater  care  than  cotton  ones,  it  being 
necessary  to  manipulate,  press,  and  rub  them  as  little  as.  possible  and  only  very  slowly 
in  order  to  avoid  felting. 

Bleaching  of  washed  woollen  yarns  or  fabrics  (wrung  out  uniformly  by  means  of  centri- 
fuges :  see  p.  468)  by  sulphuring  is  effected  by  stretching  them  out  on  rods  in  tightly 
closed  chambers  in  which  sulphur  has  been  previously  burnt  in  a  cup  situate  in  an  angle 
heated  by  a  furnace  outside.  Here  the  wool  is  left  overnight,  and  in  the  morning  the  windows 


BLEACHING,    WASHING 


713 


are  opened  and  the  wool  dried  and  deodorised  in  the  air.     The  amount  of  sulphur  burnt 
is  2  to  3  per  cent,  on  the  weight  of  the  wool,  or  less  if  the  chamber  is  a  small  one  and  deficiency 
of  air  is  maintained  in  order  to  avoid  sub- 
limation of  the  sulphur  and  its  deposition 
as  a  yellow  powder  in  the  wool. 

Bleaching  with  Hydrogen  Peroxide  is 
carried  out  in  the  cold  or  at  a  gentle  heat,  and 
for  woollen  yarn,  paraffined  wooden  vessels, 
or,  better,  cement  troughs,  are  used.  Woollen 
or  silk  fabrics  are  wound  into  a  vessel  similar 
to  that  used  for  dyeing  (see  later),  or,  better, 
on  a  jigger  (see  later).  The  bath  is  prepared 
by  diluting  commercial  10  to  12  vol.  H2O2 
with  8  to  10  times  its  volume  of  water,  and 
rendering  it  slightly  alkaline  with  ammonia 
(see  vol.  i,  p.  235).  After  use  the  bath  is 
preserved  by  acidification  with  sulphuric 
acid.  More  economical  bleaching  is  obtained 
with  sodium  peroxide,  which,  however,  must 
be  used  with  great  caution  (see  vol.  i,  p.  440) ;  FIG.  451. 

better    results    are    obtained  with    sodium 

perborate  (see  vol.  i,  p.  480)  in  a  bath  containing,  say,  200  litres  of  water,  600  grms. 
of  sulphuric  acid  of  66°  Be.,  and  1-8  kilo  of  sodium  silicate  at  40°  Be. 


FIG.  452. 

Washing  of  Woollen  Fabrics  is  carried  out  in  various  ways.  A  number  of  the  pieces, 
the  two  ends  of  each  being  tied  together,  are  wound  round  in  a  trough  fitted  with  a  pair 
of  pressure  rollers,  A  and  B  (Figs.  449,  450),  and  containing  hot  soap  and  soda  solution. 
Beneath  the  rolls  is  a  wooden  channel,  G,  to  collect  the  expressed  liquid,  which  for  some 


4T©(D 


A 


\  P  & 


q  a  o  6  : 
?  •  <  •  •  r  *• 


a  a  Q  D 


Fio.^453. 

time  is  allowed  to  run  back  through  r,  but  when  dirty  is  run  off  outside.  Thorough  rinsing 
with  water  is  carried  out  in  the  same  vessel.  It  must  be  noted  that  almost  all  washing 
and  dyeing  machinery  is  fitted  with  arrangements  for  obtaining  different  velocities  of 
the  moving  parts,  with  pipes  for  water  and  steam,  &c. 

Very  heavy  woollen  fabrics  are  more  easily  washed  at  their  full  width  in  vessels  (Fig.  451 ) 
similar  to  the  preceding.     But  the  lighter  ones  are  most  conveniently  dealt  with  by  joining 


714 


ORGANIC    CHEMISTRY 


the  pieces  end  to  end  so  as  to  form  a  single  piece,  which  is  treated  in  the  machine  shown 
in  Fig.  452,  and,  in  diagrammatic  section,  in  Fig.  453.  This  is  furnished  with  three  pairs 
of  rolls,  A,  B,  and  C,  which  press  the  pieces  in  their  passage  from  one  vessel  to  the  next, 
while  a  slow  current  of  water  enters  at  R  and  takes  a  zigzag  course  through  the  succeeding 
vessels  ;  a  little  soap  and  soda  solution  is  gradually  added  in  vessels  1,  2,  and  3,  which  are 
heated  by  steam-pipes,  while  the  dirty  water  is  discharged  continuously  from  S. 


FIG.  454. 


FIG.  455. 


For  making  certain  articles,  woollens  must  be  subjected  to  Milling,  which  transforms 
them  into  more  or  less  close  cloth. 

When  the  pieces  are  rolled  up,  moistened  with  soap  solution,  and  then  continually 
compressed  and  rubbed  together,  the  wool  is  felted  and  cloth  formed  in  the  course  of  a 
few  hours.  The  milling  machine  in  which  this  is  effected  is  shown  in  Figs.  454  and  455. 
The  material  is  caught  between  the  three  wooden  rollers  A,  B,  and  C,  which  compress 

them  and  force  them  into  the  wooden 
channel  R  8,  where  the  pressure  of  the 
plate  R  may  be  increased  by  the  spring 
A  ;  the  expressed  liquid  collects  in  the 
channel  E  and  is  at  first  returned  but 
later  discharged.  If  any  knots  were 
formed  they  would  stick  at  P  and  raise 
a  spring,  T,  thus  stopping  the  driving- 
belt.  With  certain  heavy  fabrics  already 
soaked  with  oleine,  milling  is  carried  out 
with  addition  of  a  little  soda  solution, 
which  saponifies  the  oleic  acid.  In  some 
cases  dilute  sulphuric  acid  is  used,  but 
1  idler  results  are  apparently  obtained 
with  1  per  cent,  lactic  acid  solution,  the 
wool  then  retaining  greater  lustre  and  elas- 
ticity (G.  Ita,  Ger.  Pat.  236,153  of  1910). 
Some  fabrics  which  are  required  to  take  bright  designs  and  a  very  smooth  and  shiny 
surface  (satin,  &c.)  are  freed  from  the  down  always  accompanying  textile  fibres — especially 
after  washing,  &c.— by  passing  them,  quite  taut,  quickly  over  a  row  of  gas-jets  (or  over  a 
sheet  of  heated  copper  or  a  strip  of  metal  heated  electrically),  which  burn  the  hair  on  the 
face  and  sometimes  on  the  reverse  of  the  fabric  too  (see  Fig.  456,  where  the  gas-jets  run 
horizontally  from  A  and  B). 

The  removal  of  cotton  fibres  or  bits  of  vegetable  matter  (which  would  become  more 
noticeable  after  dyeing)  from  woollens  may  be  effected  by  hand,  but  is  more  commonly 
attained  by  Carbonisation.  In  this  the  fabric  is  impregnated  uniformly  with  sulphuric 


Fit;.  456. 


715 

acid  of  about  4°  Be.  (or  aluminium  chloride  solution),  centrifuged  and  heated  at  125°  to  135° 
— being  passed  at  width  either  over  a  series  of  tinned  sheet-iron  or  copper  rollers  (similar 


FIG.  457. 

to  those  used  for  drying  woven  goods  after  dyeing)  through  which  steam  at  2  to  3  atmos.  is 
passed  (see  Fig.  481,  p.  724)  or  else  slowly  through  a  large  oven  heated  with  hot  air  or 
with  branched  pipes  fed  with  steam  under  pressure  (see  Fig.  457).  In  this  way  all  the 


FIG.  458. 


vegetable  fibres  are  incinerated  or  carbonised  and  are  eliminated  in  the  subsequent 
souring,  which  occupies  an  hour  and  is  effected  by  means  of  a  large  quantity  of  water 
in  the  washing  vessels  already  described  (Figs.  449,  450). 

I  As  has  been  mentioned,  woollen  fabrics  exhibit  a  tendency  to  felt  and  shrink,  and  these 
actions  may  become  very  pronounced  during  dyeing,  when  the  material  is  kept  moving 


716 


ORGANIC    CHEMISTRY 


in  boiling  baths  for  two  or  three  hours.  In  order  to  avoid  these  changes,  which  likewise 
often  spoil  the  design,  the  fabric  is  subjected  to  Fixing,  which  consists  in  heating  it  in  a 
stretched  condition  in  vigorously  boiling  water,  i.e.  at  a  temperature  rather  higher  than 
any  it  will  experience  in  subsequent  operations  ;  scalding  of  the  fibres  in  this  way  causes 


FIG.  459. 

partial  loss  of  their  elasticity  and  power  of  contraction,  and  the  fabric  shrinks  less  during 
dyeing.  Light  fabrics  are  fixed  in  the  so-called  revolver  machine  (Fig.  458),  in  which  the 
material  is  wound  in  compact  rolls  on  reels  dipping  into  a  vessel  of  water  kept  briskly 
boiling  ;  each  reel  may  have  six  rolls  and  one  reel  is  arranged  in  each  of  two  adjacent 
vessels.  The  axis  of  each  reel  revolves  during  the  winding,  and  when  the  first  reel  has 


FIG.  460. 

received  the  first  six  rolls,  the  first  roll  begins  to  unwind  to  form  another  on  the  second  reel, 
so  that  the  part  of  the  fabric  which  was  peripheral  on  the  first  roll  becomes  central  in  the 
roll  of  the  second  reel.  This  procedure  prevents  any  subsequent  irregularity  of  colouring 
owing  to  the  more  ready  and  more  intense  fixation  of  the  dye  on  the  parts  subjected  to 
the  most  prolonged  action  of  the  boiling  water.  Each  roll  may  contain  from  100  to  300 
metres  of  fabric,  which  is  fixed  in  about  an  hour. 

Certain  heavy  woollens  with  a  satin  surface  (and  also  mixed  wool  and  cotton  goods — 
unions — or  cotton  goods  with  a  satin  foundation)  are  fixed,  and  at  the  same  time  furnished 


DYEING 


717 


FIG.  401. 


with  a  lustre  which  persists  even  after  dyeing,  by  so-called  crabbing.  The  machine  in 
which  this  is  carried  out  consists  essentially  of  two  or  three  pairs  of  superposed  heavy  rolls 
of  solid  iron  (Figs.  459,  460).  One-half  of  the  lower  roll  of  each  pair  dips  into  a  long 
narrow  vessel  of  water  kept  boiling  by  direct  steam.  The  stretched,  smooth  cloth  is  wound 
in  compact  rolls  on  the  lower  roll,  and  is  then  allowed  to  revolve  for  30  to  40  minutes  in  the 

boiling  water,  being  pressed  by  the 
upper  roll,  which  revolves  freely  and 
can  be  weighted  by  means  of  levers. 
The  fabric  then  passes  to  the  lower 
roller  of  the  adjacent  vessel  and  so  on. 

DYEING.  Cotton  and  wool  in  flock 
were  at  one  time  dyed  by  immersing 
them — in  cloth  or  net — in  open  wooden 
vessels  containing  the  hot  dye-bath. 
Use  was  afterwards  made  of  mechanical 
apparatus  similar  to  that  shown  in 
Fig.  445,  where  the  material  remains 
stationary  on  a  false  bottom,  below 
which  the  liquid  is  drawn  off  and 
pumped  to  the  top. 

It  was,  however,  often  found  that 
the  liquid  did  not  pass  uniformly 
through  the  whole  of  the  fibre  but  went 
more  easily  through  that  which  was 

least  compressed  and  which  contained  channels,  thus  producing  irregular  dyeing. 
Almost  universal  use  is  now  made  of  mechanical  apparatus  similar  to  the  above,  but 
with  the  fibre  highly  compressed  (-see  Fig.  461).  In  this  case  the  pump,  which  must  be 
more  powerful,  causes  complete  penetration  of  the  liquid,  and  much  better  results  are 
obtained.  Skeins  of  yarn  can  also  be  dyed  in  this  apparatus  when  they  are  well  com- 
pressed. After  the  discharge  of  the  dye-bath  (kept,  if  required,  for  a  subsequent 
operation),  the  dyed  fibre  may  be  washed  in  the  same  vessel. 

To  dye  combed  wool  (tops)  wound  on  to  bobbins  by  suitable  machines  (Fig.  462),  very 
general  use  is  made  of  Obermaier  mechanical 
apparatus  of  the  revolver  type,  in  which  the 
bobbins  are  arranged  in  as  many  horizontal, 
cylindrical  cases  fitting  into  a  vertical  cylinder 
closed  at  the  top  and  communicating  below 
with  the  pipe  of  a  pump,  which  it  fits  exactly 
(Fig.  463)  ;  the  mode  of  action  is  shown 
clearly  by  the  figure.  A  more  simple  appa- 
ratus which  carries  larger  charges  and  is 
largely  used  also  for  yarn  on  bobbins  with 
crossed  thread,  is  that  of  Halle  shown  in 
Fig.  464,  where  may  be  seen  the  false  bottom 
supporting  the  bobbins,  the  pump  for  circu- 
lating the  dye  solution  and  the  perforated 
cover  pressed  down  by  vertical  screws.  In 
these  mechanical  apparatus  it ,  is  always 
possible  to  reverse  the  sense  in  which  the 
liquid  circulates,  homogeneous  dyeing  being 
thus  more  easily  obtained. 

With  skeins  of  spun  fibre,  various  methods  of  dyeing  are  in  use  :  in  the  old  method, 
still  largely  used,  the  skeins  are  threaded  on  smaoth  round  sticks  so  that  one-half  of  the 
skein  is  immersed  in  the  dye-bath,  the  skeins  being  turned  or  inverted  on  the  stick  from 
time  to  time  by  hand  (see  Fig.  465).  The  form  of  the  wooden  vessel  is  now  simpler,  as  is 
seen  from  Figs.  466  and  467,  which  show  the  perforated  false  bottom  below  which  are  the 
direct  or  indirect  steam-pipes  for  heating  the  bath,  and  the  perforated  wall,  P,  outside  of 
which  the  colour  is  gradually  added  so  that  it  may  not  come  into  immediate  contact  with 
the  neighbouring  skeins. 


FIG.  462. 


718 


ORGANIC    CHEMISTRY 


A  mechanical  apparatus  for  dyeing  skeins  is  shown  in  Fig.  468.  The  skeins  are  threaded 
on^rods  which  are  rotated  by  toothed  wheels,  while  the  whole  frame  can  be  raised  from  or 
lowered  into  the  bath  by  a  toothed  rack.  Still  better  is  the  Klauder-Weldon  revolving 
apparatus  shown  in  Figs.  469  and  470  :  on  a  large  bronze  wheel,  one-half  of  which  dips 


FIG.  463. 


into  a  trough  while  the  other  half  is  covered,  are  fixed  axial  and  peripheral  rods,  which 
keep  the  skeins  taut.  The  wheel  revolves  slowly  in  the  dye-bath,  and  the  pegs,  b,  at  the  ends 
of  the  peripheral  rods  knock  against  an  iron  striker  inside  the  trough,  so  that  the  rods 
revolve  slightly  each  time  ;  hence  the  skeins  threaded  on  them  are  moved  a  few  centi- 
metres. Two  workmen  suffice  for  the  charging  and  discharging  of  100  to  200  kilos  of  wool 


'. 

Fia.  464. 

or  cotton,  while  during  the  dyeing  one  man  can  look  after  three  or  four  of  these  machines, 
adding  the  necessary  colour  now  and  then  by  means  of  tjie  copper  funnel  A. 

The  steam  for  heating  the  bath  reaches  the  bottom  of  the  trough  by  the  tube  d.  At  e 
is  an  automatic  indicator  which  shows  when  any  particular  peripheral  rod  does  not  turn 
owing  to  the  skein  being  caught.  The  rapidity  of  revolution  may  be  altered,  but,  as  a  rule, 
the  movement  is  slow  in  order  that  the  wool  may  not  be  felted. 

In  recent  years  a  happy  solution  has  been  found  to  the  problem  of  dyeing  cotton  or 
woollen  yarn  while  still  wound  on  the  tubes  of  the  spinning  machine  as  spools  or  cops, 


DYEING    OF    SPOOLS    AND    SKEINS 


719 


thus  avoiding  the  winding  into  skeins  and  preserving  the  fibre  better.  At  first  the  per- 
forated tubes  of  the  bobbins  were  inserted  in  drums  which  rotated  in  the  bath  and  from 
the  interior  of  which  the  air  or  liquid  was  pumped,  the  bath  being  hence  circulated  from 

the  interior  to  the  exterior  of  every  bobbin  and  vice 
versa  (Figs.  471,  472).  There  are  various  other  arrange- 
ments, but  recently  a  good  reception  has  been  every- 
where accorded  to  an  apparatus  devised  by  De  Keuke- 
laeres  of  Brussels.  This  compresses  the  skeins  or  bobbins 
in  a  square  iron  or  copper  case  on  to  a  perforated  false 
bottom,  while,  before  the  case  is  covered  with  a  per- 
forated metal  plate,  the  yarn  is  covered  with  sea-sand, 
which  is  forced  into  all  the  pores  of  the  mass  not  occupied 
by  fibre  by  means  of  a  water-jet.  The  cover  is  then 
fitted  and  screwed  tight,  and  the  bath  circulated  through 
the  mass  of  yarn  by  means  of  a  pump  capable  of  develop- 
ing considerable  pressure  ;  the  liquid  may  circulate  from 
bottom  to  top  and  vice  versa  and,  finding  no  channels 
open,  is  obliged  to  traverse  the  fibre  uniformly.  When 
the  dyeing  is  finished,  it  suffices  to  place  the  bobbins  in  a  perforated  basket  and  to  shake 
this  in  a  vessel  of  water  to  separate  the  whole,  of  the  sand,  which  collects  at  the  bottom 
of  the  vessel  and  can  be  used  again. 


FIG.  466. 

For  dyeing  skeins  of  cotton  with  Turkey  red,  which  is  the  fastest  red  for  cotton,  the 
latter  must  be  prepared  and  mordanted.     It  is  not  bleached  with  chlorine  but  is  boiled 
for  a  long  time  with  a  caustic  soda  solution  (0-75°  Be.)  under  pressure  (2  atmos.)  for  4  to 
5   hours.      When   washed,    the   skeins  of 
cotton  are  passed  repeatedly  into  a  bath 
of   neutralised  ammonium  sulphoricinate 
(20  kilos  of  50  per  cent,  strength  per  100 
litres  of  water ;  see  p.  327) ;  this  operation 
is  readily  done  with  a  suitable  machine 
(Fig.  473),  which  is  fitted  with  ingenious 
contrivances   for  pressing,  wringing,    un- 
twisting, and  immersing  the  skeins  in  the 
sulphoricinate   bath  repeatedly  and  auto- 
matically.     When  thoroughly  soaked,  the  pIG   ^QJ 
skeins  are  dried  at  50°  to  60°,  then  steamed 

under  an  excess  pressure  of  0-5  atmos.  in  an  autoclave  for  an  hour,  and  afterwards  passed 
into  the  mordanting  bath,  consisting  of  a  basic  aluminium  sulphate  solution  (7°  Be.)  at 
45°  (with  an  iron  mordant,  a  violet  colour  is  obtained  instead  of  red  ;  with  one  of  tin  an 
orange  colour,  and  with  one  of  chromium  a  reddish  brown  colour ;  but  these  mordants 
are  rarely  used  in  practice)  ;  they  are  subsequently  dried  at  45°. 


720 


ORGANIC    CHEMISTRY 


Use  is  often  made  next  of  a  tepid  bath  consisting  either  of  a  little  chalk  suspended  in 
water  or  of  sodium  arsenate,  to  remove  any  sulphoricinate  not  stably  fixed,  and  hence  to 
give  subsequently  a  brighter  colour.  After  this  preparation,  the  skeins  are  passed  into  the 
dye-bath  (10  to  15  per  cent,  of  alizarin  paste,  calculated  on  the  weight  of  cotton)  contained 
in  wooden  vats  and  heated  by  tinned  copper  steam-coils  ;  the  temperature  is  first  kept  at 


FIG.  468. 

25°  for  an  hour  and  is  then  raised  in  30  minutes  to  65°  to  70°,  the  goods  being  manipulated 
for  an  hour.  The  dyed  skeins  are  dried  and  are  often  introduced,  without  washing,  into  a 
second  sulphoricinate  bath,  being  then  steamed  for  an  hour  in  an  autoclave  at  1  atmos.  ; 
the  colour  is  not  very  bright  but  is  made  so  by  immersing  the  material  for  half  an  hour 
in  a  0-5  per  cent,  soap  solution  heated  under  slight  pressure  (0-5  to  0-25  atmos.).  Thorough 


FIG.  469. 

washing  with  water  is  followed  by  drying  at  a  gentle  heat.  Although  Turkey  red  is  removed 
to  a  small  extent  if  the  material  is  scoured  with  a  white  fabric,  yet  it  is  the  fastest  red  against 
washing  and  light  now  prepared  on  cotton.  Kornfeld  (1910)  regards  the  fastness  of  Turkey 
red  as  due,  not  to  the  constitution  of  alizarin,  but  rather  to  the  formation  of  a  highly  resistant 
double  salt  of  aluminium  oleate  and  the  calcium  salt  of  alizarin,  and  still  more  to  the 
polymerisation  of  the  fatty  acid  molecules  under  the  action  of  steam. 

According  to  a  patent  by  Kornfeld,  Turkey  red  dyeing  may  be  carried  out  in  the  usual 
mechanical  apparatus  with  circulation  of  the  bath,  the  alizarin  being  rendered  soluble  by 
means  of  sucrate  of  lime. 


DYEING    OF    COTTONS    AND    WOOLLENS     721 

Cotton  Fabrics  are  sometimes  dyed  in  ropes  with  vessels  similar  to  those  used  for  wool 
(see  later),  but  more  usually  in  the  so-called  jigger  (Fig.  474),  which  is  a  rather  shallow 
wooden  trough  provided  with  two  outside  rollers  worked  alternately  by  gearing  so  as  to 
wind  or  unwind  the  pieces  (3-4)  ;  the  latter  are  sewn  end  to  end  and  are  kept  quite  taut, 
and  pass  below  two  small  rollers  close  to  the  bottom  of  the  trough.  The  dye  solution  in 
the  bath  may  be  heated  at  will  by  direct  or  indirect  steam.' 


FIG.  470. 


The  jigger  is  often  used  also  for  dyeing  unions,  i.e.  fabrics  composed  of  cotton  warp  and 
wool  weft,  since  these  do  not  cockle  or  wrinkle,  as  all-wool  goods  would  do,  when  passed 
under  tension  from  one  roll  to  another. 

Woollens  are  usually  dyed  in  wooden  vessels  provided  with  one  or  two  reels  which 
raise  the  goods  in  ropes  from  the  front  part  of  the  vessel  and  drop  them  into  the  bath, 
the  inclined  wall  at  the  back  forcing  them  in  folds  on  to  the  bottom  of  the  vessel  itself 
(Figs.  475,  476). 


FIG.  471. 


FIG.  472. 


In  some  cases  the  velocity  of  rotation  of  the  reels  can  be  varied  at  will,  being  accelerated 
at  the  moment  when  the  colour  is  introduced  into  the  perforated  compartment  which 
admits  of  its  gradual  passage  into  the  whole  of  the  bath.  The  perforated  steam-pipe 
also  passes  into  the  bottom  of  this  compartment  and  is  so  arranged  that  the  steam  does  not 
strike  against  the  pieces,  as  this  would  result  in  irregular  dyeing.  The  velocity  of  the  reel 
must  not  be  too  high  (20  to  50  cm.  per  second),  as  otherwise  the  wool  would  felt  and  the 
bath  cool  too  rapidly.  When  the  pieces  are  introduced  into  the  vessel,  one  end  is  thrown 
over  the  reel  and  then  stitched  with  twine  to  the  other  end  (see  Fig.  476).  In  some  cases 
the  materials  (e.g.  cashmeres)  are  twisted,  by  the  movement  in  the  trough,  into  very  thin 
cords,  into  which  penetration  of  the  colouring-matter  is  difficult  and  irregular ;  in  order 
ii  46 


722 


ORGANIC    CHEMISTRY 


to  avoid  these  disadvantages,  such  fabrics  arc  first  folded  in  two  lengthwise  and  the  selvedges 
then  stitched  together. 

During  the  dyeing  operation,  the  dyer  cuts  off  small  samples  of  the  fabric  from  time  to 
time,  washes  them,  dries  them  in  a  warm  towel  and  compares  them  with  a  specimen, 
so  that  fresh  addition  of  colour  may  be  made  where  necessary.  Such  fresh  colour  is  dissolved 
apart  in  a  wooden  bucket  in  a  few  litres  of  the  hot  dye-bath,  the  solution  being  always 


FIG.  473. 

passed  through  a  very  fine  hair-sieve  to  remove  granules  of  undissolved  dye,  which  would 
spot  the  material ;  the  steam-cock  is  closed  while  the  new  dye  is  being  gradually  added. 

The  dyeing  of  woollen  fabrics  is  commenced  with  a  bath  of  tepid  water  (40°  to  50°) 
with  the  addition  of  10  to  15  per  cent,  of  crystallised  sodium  sulphate  and  2-3  percent,  of 
concentrated  H.2SO4  (or  5  to  6  per  cent,  of  sodium  bisulphate)  (these  proportions  referring  to 
the  weight  of  the  fibre).  The  colouring-matter  (a  few  grammes  for  pale  colours  and  as 


FIG.  474. 

much  as  5  kilos  of  black  per  100  kilos  of  material)  is  added  in  several  portions  at  the  begin- 
ning of  the  operation,  the  goods  being  slowly  moved  meanwhile.  In  the  course  of  an  hour 
the  bath  is  brought  to  boiling  and  this  may  last  one  or  two  hours  before  the  dyeing  is  complete. 
Finally  the  steam-tap  is  shut  and  the  goods  discharged  into  a  vessel  of  cold  water. 

After  being  rinsed  and  folded  roughly  by  hand  they  are  left  to  drip  on  beams  for  some 
time,  a  further  part  of  their  water  being  removed  by  two  or  three  minutes'  centrifuging  (see 
p.  468).  The  goods  are  then  ready  to  be  dried  in  the  apparatus  described  later. 

When  very  delicate  wool  or  wool  and  silk  fabrics  (with  gathers  and  embroidery)  are 
t-o  be  dyed,  they  are  sometimes  wound  concentrically  on  hooks  fitted  to  a  frame  such  as 
that  shown  in  Fig.  477.  In  this  case  the  frame  is  only  moved  now  and  then,  so  that  the 
fabric  may  not  be  injured. 


DRYING    MACHINES 

Textile  Fibres  in  Flock  are  dried  in  a  series  of  superposed  chambers  with  perforated 
bases  on  which  the  moist,  centrifuged  fibre  is  spread  (Fig.  478, 1).  At  II  is  seen  a  counter- 
poised elevator  on  which  is  placed  the  charged  chamber  ready  to  be  introduced  into  its 
position  in  the  series  in  place  of  one  containing  fibre  already  dried.  The  air  used  for  the 
drying  is  forced  in  by  the  fan  A,  and  is  heated  in  the  tubular  steam  heater  B.  The  lower 
chambers  are  dried  first,  and  when  these  are  discharged,  the  remaining  ones  are  lowered 


FIG.  475. 


FIG.  476. 


automatically  and  fresh  ones  introduced  at  the  top.  Yarn  on  bobbins  or  spindles  can 
also  be  dried  in  these  chambers. 

Skeins  of  yarn  may  be  dried  by  threading  them,  after  centrifuging,  on  rods  and  fixing 
these  horizontally  in  frames  in  a  chamber  heated  by  branched  steam-pipes  on  its  base  ; 
the  moist  air  issues  from  vent-holes  fitted  to  the  ceiling.  In  some  cases  the  yarn  is  dried 
in  hot  chambers,  the  skeins  being  stretched  over  revolving  reels  furnished  with  central 
steam-pipes,  as  is  shown  in  Fig.  479. 

Good  results  are  also  obtained  with  the  continuous  drying  machine,  in  which  the  skeins 
are  placed  on  rods,  &c.,  carried  by  chains  moving  in  a  drying  chamber  (Fig.  480)  supplied 


FIG.  477. 


FIG.  478. 


at  A  with  hot,  dry  air.  The  dry  yarn  issues  continuously  at  Z,  while  the  moist  air  finds 
an  outlet  at  B. 

Fabrics  as  they  come  from  the  centrifuge  are  usually  dried  by  passing  them,  well 
stretched,  over  a  battery  of  seven  or  nine  copper  drums  F  (Fig.  481 ).  These  are  all  moved 
regularly  by  gearing,  the  rate  being  regulated  by  means  of  the  large  disc  B,  which  is  actuated 
at  a  point  more  or  less  distant  from  its  centre  by  the  friction  roller  C  ;  the  latter  is  turned 
by  the  pulley  A,  .joined  by  belting  to  the  general  system  of  power  transmission. 

The  dried  fabrics  are  then  examined  throughout  their  entire  length  and  breadth  before 
a  well-lighted  window  in  order  to  ascertain  if  there  are  any  defects  in  dyeing  or  otherwise, 
so  that  these  may  be  remedied  before  dressing. 


724 


ORGANIC    CHEMISTRY 


Dressing  of  Fabrics  is  effected  by  impregnating  them  with  solution  of  gum,  bone  glue, 
starch,  &c.  The  fabric  is  passed  beneath  a  roller  dipping  into  a  vessel  containing  the 
solution,  and  is  then  pressed  by  a  second  roller  superposed  to  the  first  in  a  kind  of  foulard 
like  that  shown  in  Fig.  482  ;  the  vessel 
may  have  the  section  shown  in  Fig.  483. 
The  gummed  fabrics  are  subjected  to 
mechanical  treatment  varying  according 
to  the  type  required.  Dressing  increases 
the  strength  and  weight  of  the  tissue, 
which  is  next  dried  and  at  the  same 
time  pulled  out  both  lengthwise  and 
breadthwise  in  order 


FIG.  479. 


as  nearly  as  possible  to  the  dimensions  they  possessed  before  dyeing.  This  is  effected 
by  means  of  the  so-called  tentering  frame,  into  which  the  tissue  passes,  fixed  laterally  by 
the  selvedges  on  two  chains  carrying  clips  or  needle-points  ;  the  distance  between  the  two 
chains  is  gradually  increased  to  the  desired  width,  which  is  shown  on  a  graduated  iron 


FIG.  481. 

bar,  A  (Fig.  484).  Fig.  485  shows  a  complete  frame  withsthe  gumming  machine  B  and  two 
operatives  fixing  the  selvedges  on  the  points  of  the  chains.  The  widened  cloth  is  dried 
throughout  its  whole  length  by  a  current  of  hot  air  blown  into  a  long  chamber  beneath, 
and  finally  by  a' heated  drum,  C.  These  frames  are  8  to  12  metres  long,  but  are  sometimes 
constructed  on  several  stories  in  order  to  save  length.  Fig.  486  gives  a  better  view  of  the 
frame  in  outline_:_the  gummed,  centrifuged,  and  folded  cloth  lies  ready  on  the  two  benches, 


CALENDARS 


725 


B ;  the  air  is  heated  at  T  and  the  fan  V  forces  the  hot  air  into  the  long  chamber,  R ;  the 
cloth  enters  at  jB  and  issues  at  G.  • 

Milled  fabrics  and  certain  others  which  are  required  to  present  a  hairy  surface  are 
passed  to  the  so-called  raising  gigs  (Fig.  487),  consisting  of  one  or  more  large  drums  carrying 
numbers  of  metallic  points  or  strings  of  the  spiny  capsular  heads  of  Dipsacus  fullonum 
(10  to  20  cm.  in  length,  Fig.  488)  on  spindles.  The  drums  or  spindles  revolve  so  that  the 


\ 


FIG.  482. 


FIG.  483. 


points  just  touch  the  stretched  surface  of  the  cloth  and  draw  from  it  fairly  long  hairs, 
which  are  then  rendered  uniform  by  passing  the  dry  cloth  to  the  cutting  and  brushing 
machines  furnished  with  cylindrical  brushes  and  with  drums  fitted  with  cutting  edges 
arranged  helically  (see  Fig.  489) ;  the  first  brush,  A,  raises  the  hair,  the  cutter,  B,  cuts  or 
crops  it  off  uniformly,  and  the  second  brush,  C,  sets  it  regularly  all  in  the  same  direction. 
A  similar  operation  is  carried  out  with  velvets,  which  are,  however,  woven  specially, 
and  often  in  two  superposed  pieces  attached  by  a  large  number  of  fibres,  which  are  then 
cut  exactly  in  two  so  as  to  give  two  separate  pieces  each  with  a  hairy  face. 


FIG.  484. 

When  the  fabrics  are  required  to  have  a  very  smooth,  shiny  surface,  they~are  passed 
after  gumming  to  the  so-called  calenders.  A  common  type  of  the  latter  for  wool  and 
unions,  which  require  but  little  pressure,  is  that  shown  in  Fig.  490  :  the  cloth  is  seized 
by  the  selvedges  by  two  discs  fitted  with  bands,  A  (called  a  palmer),  which  enlarge  the  cloth 
to  the  required  size  and  then  pass  it  on  to  a  continuous  felt,  C,  which  transfers  it  in  a  well- 
stretched  and  compressed  condition  on  to  a  copper  drum,  B,  heated  by  steam  under  slight 
pressure.  For  cotton  or  cotton  and  silk  fabrics,  use  is  made  of  calenders  with  several 
superposed  and  heated  cylinders  to  which  pressure  may  be  imparted  by  means  of  suitable 
levers  (Fig.  491 )  in  such  a  way  as  to  exert  a  kind  of  friction  on  the  cloth  passing  from  one 
cylinder  to  the  other.  When  a  very  high  finish  is  required  on  certain  satin  fabrics  of  cotton, 
they  are  passed  between  two  massive  steel  cylinders  which  are  under  very  high  pressure 


726 


ORGANIC    CHEMISTRY 


(hydraulic)  and  one  of  which  is  fluted  with  very  fine  striations  (as  many  as  10  to  25  per 
millimetre,  as  suggested  by  Schreiner)  ;  these  leave  their  stable  imprint  on  the  fabric 
like  so  many  minute,  shining  cylinders  like  silk  fibres,  which  reflect  light  under  any  angle  ; 


.;.r. 


FIG.  485. 

this  finish  is  known  as  silk  finish  (or  Schreiner  finish).     Similar  calenders  are  used  for 
obtaining  special  watered  effects  (moire).   • 

On  woollen  fabrics  calenders  generally  produce  a  so-called  false  finish  like  that  of  a 
bright  sheet  of  metal.     This  is  not  regarded  as  desirable  by  the  merchants,  and,  further, 


FIG.  486. 

such  a  finish  will  show  rain- drops,  even  after  drying.  In  order  to  avoid  this  inconvenience 
and  the  better  to  fix  the  material  in  both  directions,  so  that  it  will  not  shrink  when  worn, 
it  is  subjected  to  so-called  steaming,  i.e.  to  the  action  of  steam  under  a  pressure  of  2  to  3 
atmos.  (some  colours  will  not  withstand  this  operation).  The  fabric  is  well  stretched 


Fio.  487. 


FIG.  488. 


and  wound,  together  with  a  cloth,  round  a  perforated  cylinder  ;  the  roll  of  two  or  three 
pieces  thus  obtained  is  wrapped  in  cloth  fastened  by  strings,  the  cylinder  being  then  fixed 
vertically  on  a  steam-cock  (Fig.  492).  The  steam,  under  pressure,  is  obliged  to  traverse 
the  whole  of  the  roll  of  fabric,  and  when  it  issues  in  a  dense  cloud  (after  a  few  minutes) 
the  operation  is  at  an  end  ;  the  roll  is  then  removed,  but  is  allowed  to  cool  without  unrolling, 


PRESSING 


727 


since  in  that  way  it  acquires  a  better  and  more  resistant  lustre.  The  latter  is  also  found  to  be 
improved  by  carrying  out  the  steaming  in  a  vacuum,  the  rolls  G  H  (Fig.  493)  being  introduced 
into  a  kind  of  horizontal  jacketed  autoclave,  X,  previously  heated  by  passing  steam  through 


FIG.  489. 

the  jacket  ;  when  the  cover  L  has  been  tightly  closed,  the  autoclave  is  evacuated  by 
passing  steam  into  it  and  condensing  the  steam  by  a  water-spray  in  the  cylindrical  chamber 
W,  which  communicates  with  the  autoclave  by  means  of  the  tap  R.  After  this  the  steam 
is  passed  through  the  roll  of  fabric,  either  from  the  inside  to  the  outside  or  vice  versa,  by 
fixing  the  roll  in  a  suitable  manne^-to  the  steam-cock. 


FIG.  490. 

Of  the  various  other  operations  comprised  in  the  finishing  of  fabrics,  only  that  of 
pressing  between  hot  card  need  be  referred  to  ;  this  gives  lustre  to  cloths  which  are  not 
subjected  to  steaming  and  in  general  imparts  a  very  soft,  pleasant  feel,  more  particularly 
to  the  finer  woollens. 

In  this  operation,  which  is  the  last  of  importance,  the  best  effect  is  obtained  when 
10  to  15  per  cent,  of  moisture  is  present,  so  that  fabrics  which  are  too  dry  are  treated 
first  with  a  slight  steam- jet,  being  meanwhile  wrapped  on  drums  in  large  rolls  ;  after  some 


728  ORGANIC    CHEMISTRY 

hours  these  rolls  are  unwound  and  the  fabric  arranged  in  regular   folds,  between  each 
adjacent  pair  of  which  is  inserted  a  piece  of  hot,  smooth  card.      The  whole  is  then  left 


FIG.  491. 


under  pressure  in  a  hydraulic  press  (Fig.  494)  for  10  to  12  hours.  In  order  to  obtain  uniform 
heating  while  the  pressure  is  being  exerted,  presses  are  now  used  with  double  pillars  in  which 
steam  circulates  (Fig.  495)  ;  also  the  pillars  are  sometimes  heated  electrically. 


FIG   493. 
•  <\ 

For  the  folding  or  rolling  of  fabrics,  and  also  for  measuring,  simple  and  rapid  machines 
have  been  devised. 

For  the  Mercerisation  of  cotton  yarn  in  hanks  (see  p.  685)  a  machine  such  as  that  shown 
in  Fig.  496  is  used.  The  uniformly  moist  skeins,  as  they  come  from  the  centrifuge,  are 
stretched  in  a  thin  layer  between  the  two  cylinders,  A  and  B,  the  distance  between  which 


FIG.  494. 


Fia.  496. 


FIG.  495. 


730 


ORGANIC    CHEMISTRY 


can  be  increased  so  that  the  skeins  are  considerably  stretched.      Then,  when  the  rollers  are 
revolving,  a  lever  is  operated  to  raise  the  iron  vessel,  C,  containing  cold  caustic  soda  solution 
of  25°  to  30°  Be.,  one-half  of  each  cylinder  dipping  into  the  soda.      At  the  end  of  a  few 
minutes  the  imbibition  is  complete,  the  soda  solution  is  drawn 
off  into  a  tank  provided  with  a  pump,  while  a  copious  supply 
of  water  is  sprayed  on  to  the  skeins,  which  are  pressed  by  the 
roller  R.     When  washing  is  complete,  the  tension  is  relieved  and 
the  skein  removed. 

There  are  also  other  machines  for  mercerising  fabrics,  these 
being  kept  stretched  by  contrivances  similar  to  those  used  in 
the  tentering  frame  (see  Figs.  484  to  486),  while  the  caustic  soda 
is  removed  from  the  fabrics  by  means  of  suction  pumps.  The 
fabric  is  then  washed  with  a  little  hot  water  so  as  to  give  a 
moderately  strong  solution  of  caustic  soda,  which  may  be  used 
to  dissolve  solid  caustic  soda  or  may  with  advantage  be  con- 
centrated in  multiple-effect  evaporators  (see  vol.  i,  p.  442).  The 
caustic  soda  is  removed  completely  from  the  fabric  by  thorough 
washing  in  cold-water,  then  in  a  slightly  acid  bath  and  finally 
in  water. 
The  Printing  of  textiles,  as  indicated  on  p.  707,  is  carried  out  by  pressing,  with  a 


FIG.  497. 


FIG.  498. 

rubber  roller,  A  (Fig.  497),  the  fabric  or  yarn  against  a  copper  cylinder,  B,  on  which  the  design 
is  engraved.  The  copper  cylinder  receives  the  pasty  colour  from  a  roller,  /,  dipping  into  the 
vessel,  C,  containing  the  thickened  colour  solution,  a  blade, 
D,  then  scraping  away  the  excess  of  colour  so  that  only 
the  hollows  of  the  design  remained  filled.  Between  the 
rubber  cylinder  and  the  fabric,  T,  to  be  printed  runs  a 
continuous  band,  E,  which  is  kept  taut  by  the  con- 
trivance V.  The  arrangement  used,  with  the  adjacent 
drying  chamber,  o,  is  shown  in  Fig.  498  :  the  vessel  of 
colouring-matter  is  at  cd,  and  the  fabric  is  unwound 
from  g  together  with  the  accompanying  cloth  h,  and  the 
continuous  pressure  cloth  i  ;  the  dyed  and  dry  fabric  is 
collected  in  folds  at  I,  while  the  cloth  h  is  rewound  at  r, 
and  i  returns  constantly  to  the  printing  cylinder.  Wh>n 
several  colours  are  to  be  printed  on  one  and  the  same 
fabric,  a  number  of  rolls  and  colour  vessels  are  required,  ^IG  499 

as  is  shown  diagrammatically  in  Fig.  499. 

Fig.  500  shows  a  complex  machine  for  the  printing  of  textiles  in  twelve  colours  at  once  ; 
highly  skilled  workmen  are  required  to  regulate  its  working  with  accuracy. 


COLOUR-PRINTING    MACHINES 


7B1 


A  simple  arrangement  for  printing  yarn  in  skeins  by  hand  is  shown  in  Fig.  501.  The 
skeins  are  kept  taut  between  the  rods  A  and  B  and  the  printing  rollers,  which  are  not  very 
clear  in  the  figure,  are  below  A.  The  printed  skeins  are  hung  on  rods  fitted  to  a  framework, 
this  being  introduced  into  an  autoclave  to  be  treated  with  steam  under  pressure  (Fig.  502). 


FIG.  500. 


Printing  colours  are  boiled  with  the  thickening  agents  in  suitable  double-bottomed 
boilers,  heated  by  means  of  steam  and  furnished  with  stirrers.  Fig.  503  shows  a  battery 
of  such  colour-pans. 


Fra.  501. 


FIG.  502. 


When  mention  was  made  of  aniline  black  (p.  662),  it  was  stated  that  the  complete  develop- 
ment of  this  colour  is  obtained  in  an  oxidation  chamber  (Fig.  504).  In  the  case  of  yarn,  the 
method  of  continuous  drying  illustrated  in  Fig.  480  (p.  724)  gives  good  results.  But 
with  fabrics  use  is  generally  made  of  a  chamber  with  revolving  rollers,  where  the  fabric 


FIG.  503. 


FIG.  504. 


FIG.  505. 


PROTEINS  733 

traverses  slowly  a  very  long  path  and  isaues  completely  black  ;  a  hood  is  arranged  to  carry 
of?  acid  vapours.  Of  great  importance  in  this  operation  is  the  regulation  of  the  tem- 
perature, of  the  draught  and  of  the  velocity  with  which  the  fabric  passes  through  the 
chamber.  Unexpected  stoppages  are  dangerous,  as  they  may  lead  to  corrosion  of  the 
fabric  or  alteration  of  the  colour. 

To  polish  and  soften  silk,  the  skeins  are  stretched,  twisted,  and  rubbed  repeatedly  on  a 
smooth  rod  fixed  in  the  wall.  But  nowadays  this  is  done  by  machines  (Fig.  505),  which 
act  automatically  and  give  a  large  output. 

T.  PROTEINS  OR  ALBUMINOIDS 

These  are  fundamental  products  in  the  formation  and  constitution  of 
animal  and  vegetable  organisms.  The  protoplasm  of  vegetable  and  animal 
cells,  which  is  the  origin  of  the  metabolic  processes  and  hence  of  the  life  of  the 
organism,  consists  of  protein  substances,  which  are  also  indispensable  components 
of  foodstuffs. 

From  a  physiological  point  of  view  they  are  therefore  of  the  utmost  -sig- 
nificance, but  their  chemical  nature  is  very  complex  and  is  still  little  understood, 
although  the  investigations  of  Emil  Fischer  and  a  number  of  able  collaborators 
during  the  past  ten  years  have  to  some  extent  pierced  the  veil  surrounding 
this  most  important  group  of  organic  compounds,  which  had  been  previously 
studied,  as  regards  some  of  their  more  superficial  characters,  by  Ritthausen, 
Hoppe-Seyler,  Hammarsten,  Neumeister,  Pfliiger,  Hedin,  Kuster,  Nencki 
and  Sieber,  &c. 

The  numerous  substances  comprised  in  this  group  are  all  composed  of 
C,  H,  0,  N,  and  S,  with,  in  a  few  cases,  P  ;  their  percentage  compositions 
vary  between  the  following  limits  :  C,  50  to  55  ;  H,  6-9  to  7-3  ;  0,  19  to  24  ; 
N,  15  to  19;  S,  0-3  to  2-4. 

The  molecular  magnitudes  of  these  substances  cannot  be  established  with 
certainty,  since  it  is  not  easy  to  isolate  single  individuals,  only  very  few  of  them 
crystallise,  none  are  transformable  into  vapour,  and  in  no  case  are  true  solutions 
obtainable  capable  of  cryoscopic  or  ebullioscopic  measurement ;  their  solutions 
are  colloidal.  Direct  or  indirect  attempts  to  determine  their  molecular  weights 
have  given  numbers  varying  from  10,000  to  30,000. 

Both  the  sulphur  and  the  nitrogen  occur  in  two  groupings,  being  partly 
removed  by  hot  potash  and  partly  more  stably  combined. 

Absolute  alcohol  coagulates  proteins  and  precipitates  them  to  some  degree 
unchanged  from  their  aqueous  solutions.  They  are  also  precipitated  unaltered 
by  solutions  of  sodium  chloride,  magnesium  sulphate  or  ammonium  sulphate 
of  different  concentrations,  which  are  characteristic  of  the  various  proteins. 

Proteins  are  coagulated  and  precipitated  from  their  aqueous  solutions 
by  small  quantities  of  mineral  acids  (nitric  acid  may  be  in  excess).  They  have 
a  feeble  acid  character  and  form  salts  as  insoluble  precipitates  with  metallic 
salts,  e.g.  ferric  chloride,  acidified  mercuric  chloride,  copper  sulphate,  &c., 
and  they  dissolve  small  amounts  of  freshly  precipitated  ferric  hydroxide.  From 
these  metallic  precipitates  proteins  are  liberated  in  a  changed  form. 

Less  pronounced  is  their  basic  character  (like  the  amino-acids,  they  behave 
as  both  acids  and  bases  at  the  same  time),  although  egg-albumin  is  completely 
precipitated  by  weak  acids,  such  as  tannin,  phosphotungstic  acid,  and  picric 
acid. 

Aqueous  solutions  of  the  proteins^are  coagulated  on  heating  to  different 
characteristic  temperatures,  and  the  coagulated  proteins  dissolve  only  in  an 
excess  of  acid  or  alkali  in  the  hot,  their  constitution  being  modified  thereby 
and  H2S  and  NH3  sometimes  evolved  :  with  alkalis  they  form  albuminates 
and  with  acids,  Acid-Albumins  (syntonins,  see  p.  737),  both  insoluble  in  water 
and  reprecipitable  by  neutralisation.  By  the  protracted  action  of  these  two 


734  ORGANIC    CHEMISTRY 

reagents  (Hydrolysis,  seebelow)  or  by  the  action  of  pancreatic  juice,  which  contains 
Tryptase  (seep.  112),  they  yield  various  amino-  or  diamino-acids  :  glycocoll, 
alanine,  phenylalanine,  aspartic  acid,  glutaminic  acid,  leucine  (in  abundance), 
pyrrolidinecarboxylic  acids,  tyrosine,  serine,  triaminotrihydroxydodecanoic  acid, 
/3-indoleacetic  acid,  arginine,  lysine,  ornithine,  tryptophane,  cystine  (sulphur 
compound),  &c.,  all  of  them  optically  active  with  the  exception  of  glycocoll. 
When  a  piece  of  boiled  egg-albumin  is  heated  at  37°  with  gastric  juice,  it  rapidly 
dissolves  with  formation  of  Peptones  and  Albumoses.  The  peptones,  passing 
into  the  intestines,  undergo  further  hydrolysis,  and  as  final  products  yield 
amino-acids.  The  complete  hydrolysis  of  the  albumin  may  be  effected  more 
rapidly  by  means  of  a  concentrated  acid  (e.g.  HC1),  which  gives  amino-acids 
and  also  ammonia.  By  putrefaction  various  other  substances  are  formed  : 
Ptomaines,  such  as  cadaverine  (see  p.  214),  putrescine  or  tetramethylene- 
diamine,  &c. ;  glucosamine,  methylamine,  ammonia,  /3-indoleacetic  acid,  phenyl- 
acetic  acid,  carbonic  acid,  hydrogen  sulphide,  formic  to  caproic  acids,  partly  of 
normal  structure  and  partly  optically  active  (valeric  and  caproic),  &c.  ;  indole, 
skatole,  phenol,  cresol,  mercaptan,"  methane,  &c.,  all  of  these  being  oxidation 
or  reduction  products  of  the  original  compounds  obtained.  The  action  of 
pathogenic  bacteria  on  proteins  yields  poisonous  substances,  the  Toxalbumins, 
which  are  similar  in  composition  to  the  proteins  and  lose  their  toxicity  when 
their  aqueous  solutions  are  heated. 

The  following  reactions  are  characteristic  of  the  proteins  : 
Protein  solutions  give  a  violet  coloration  (like  biuret)  with  alkali  and  a 
few  drops  of  .2  per  cent,  copper  sulphate  solution  (biuret  reaction). 

With  nitric  acid  in  the  hot  and  even  in  excess  a  yellow  precipitate  is  formed 
(xanihoprotein  reaction). 

With  Millon's  reagent  (see  p.  704)  a  red  coagulum  is  formed  on  boiling. 
The  degradation  or  hydrolysis  of  proteins,  when  it  is  complete  and  takes 
account  of  all  the  more  or  less  complex  groups  composing  the  protein  molecule, 
will  permit  of  an  attempt,  with  probability  of  success,  to  synthesise  these 
substances  completely,  Such  more  or  less  gradual  decompositions  are  attained 
by  protracted  heating  (for  different  times  with  different  proteins  and  in  some 
cases  for  200  hours)  in  an  autoclave,  or  by  means  of  soda  or  baryta  (Schiitzen- 
berger),  or,  better,  25  per  cent,  solutions  of  hydrochloric  or  sulphuric  acid. 
But  even  under  these  conditions  some  of  the  intermediate  compounds  cannot 
be  detected,  the  hydrolysis  being  in  many  cases  too  rapid.  Hugounenq 
and  Morel  (International  Congress  of  Applied  Chemistry,  London,  1909) 
have  obtained  a  somewhat  more  gradual  hydrolysis  by  using  15  to  25  per 
cent,  hydrofluoric  acid  solutions  and  heating  for  100  to  150  hours. 

The  separation  of  the  numerous  amino-acids  resulting  from  the  hydrolysis 
of  the  proteins  constitutes  a  difficult  problem,  which  has  recently  been  solved 
by  E.  Fischer  for  the  amino-acids  and  by  Kossel  for  the  diamino- acids.  Fischer 
subjects  the  esters  of  the  amino-acids  to  fractional  distillation  in  vacuo  and 
thus  determines  their  separate  amounts. 

It  is  thought  that  the  amino-acids  occur  in  the  proteins  in  a  condensed 
form  similar  to  Glycylglycine,  NH2  -CH2  -CO  -NH  -CH2  -C02H.  Indeed  Fischer 
was  able  to  synthesise  the  so-called  Polypeptides,  which  contain  such  groups 
and  in  many  respects  resemble  the  natural  peptones  derived  from  proteins 
(see  later)  ;  the  esters  of  the  amino-acids  readily  give  up  alcohol  and  undergo 
ketonic  condensation  to  polyanhydrides,  and  tjiese,  under  the  influence  of 
alkali,  take  up  a  molecule  of  water,  giving  the  peptides  : 

2NH2-CH2-C02C2H5  =  2C2H5-OH  +  NH<^'C^>NH  (and  this  +  H20) 

Ethylglycocoll  Double  Anhydride  or  Dlketopiperazine 


ALBUMINS  735 

NH2  •  CH2  •  CO  •  NH  •  CH2  •  C02H. 

Dipeptidc  or  Glycylgylcine 

By  chlorinating  the  carboxyl  of  the  dipeptide  with  PC15  in  acetyl  chloride 
solution,  a  second  molecule  of  ethylglycocoll  may  be  caused  to  react  with 
formation  of  a  tripeptide,  and  so  on,  higher  polypeptides  similar  to  the  natural 
ones  being  ultimately  obtained, 

X---CO-C1  +  NH2-CH2-C02-C2H5  =  HC1  +  X-  •  -CO-NH-CH2-C02-C2H5  ; 

these  polypeptides  are  completely  hydrolysed  by  hot  concentrated  HC1,  are 
digested  by  tryptase,  withstand  cold  alkali,  are  soluble  in  water  and  insoluble 
in  alcohol,  and  give  the  reactions  of  the  proteins  (see  below).  These  syntheses, 
which  represent  the  first  small  step  towards  the  synthesis  of  the  proteins,  give 
an  idea  of  the  enormous  difficulties  to  be  overcome  before  the  natural  proteins 
can  be  reconstructed.  Indeed,  since  the  dipeptides  have  molecular  weights  of 
about  100,  while  with  the  proteins  the  molecular  weight  certainly  exceeds 
10,000,  at  least  100  of  these  groups  must  be  present.  Also,  as  several  of  the 
amino-acids  contain  one  or  more  asymmetric  carbon  atoms,  stereoisomerism 
is  possible,  and  so  likewise  is  tautomerism,  e.g. 

-HN-CO—  — N:C(OH)— 

The  investigations  of  Fischer  have  resulted  in  the  synthetical  preparation 
of  more  than  a  hundred  of  the  simpler  polypeptides,  the  highest  of  which  is  an 
octadecapeptide  ;  but  on  ascending  the  series  the  complications  and  difficulties 
increase  disproportionately.  This  problem  could  occupy  a  whole  generation 
of  chemists,  and  its  solution  would  be  a  glorious  triumph  for  the  twentieth 
century,  as  it  would  banish  for  ever  the  Malthusian  threat  that  one  day  humanity 
will  be  starved  owing  to  the  disproportion  between  the  population  and  the 
productive  capacity  of  the  earth.  Indeed,  while  it  is  not  possible  to  replace 
the  proteins  in  human  nutriment  by  fats  or  carbohydrates — these  alone  leading 
to  rapid  decay  of  the  organism  and  to  death — proteins  of  themselves  are 
able  to  supply  all  the  needs  of  the  organism.  So  that  the  insufficient  production 
of  proteins  in  nature  at  some  future  time  would  of  a  certainty  be  accompanied 
by  famine,  unless  a  method  of  synthesising  proteins  by  chemical  means  had 
previously  been  discovered.  Berthelot  imagined  that  one  day  the  air  would 
supply  the  oxygen  and  nitrogen,  and  water  the  hydrogen  for  this  synthesis. 
And  it  is  not  for  us  to  deny  that  the  dream  of  yesterday  may  become  the  reality 
of  to-morrow,  if  chemistry  learns  how  to  imitate  the  simplicity  and  economy 
of  the  natural  synthetical  processes  best  exemplified  in  plants,  which  from 
carbon  dioxide,  water,  and  nitrates  are  able  to  effect  continuous  production 
of  carbohydrates,  fats,  and  proteins.  Our  laboratory  synthetical  methods  are 
still  too  cumbersome,  too  indirect,  and  generally  too  costly.  Only  when  the 
action  of  catalysts  and  light  and  the  laws  of  colloids  have  been  more  closely 
studied  can  any  hope  be  entertained  of  a  more  rapid  progress  in  the  synthesis 
of  such  complex  organic  substances. 

The  numerous  different  proteins  are  usually  classified  in  the  following  groups  and  sub- 
groups : 

I.  NATURAL  PROTEINS 

(1)  ALBUMINS  (of  eggs  or  Egg-albumin,  of  blood  serum  or  serum-albumin,  of  milk 
or  lactalbumin,  of  muscles,  of  plants,  &c.). 

These  are  the  most  common  and  also  the  best  known  of  the  proteins,  since  they  can 
be  isolated  as  definite,  crystalline,  chemical  individuals.  They  are  soluble  in  water,  dilute 
acid  or  alkali,  or  neutral  solutions  of  NaCl,  MgSO4,  or  (NH4)2S04  (the  globulins  being 


736  ORGANIC    CHEMISTRY 

insoluble),  but  in  acid  solution  these  salts  precipitate  the  albumins.  In  the  hot  they 
are  coagulated. 

The  products  of  the  putrefaction  of  albumin  contain  also  p-Hydroxyphenylacetic  Acid, 
OH  •  C6H4  •  CH2  •  CO2H,  which  occurs  likewise  in  urine  (acicular  crystals  coloured  greenish 
by  ferric  chloride). 

There  exists  nowadays  a  considerable  trade  in  dry  albumin  obtained  from  the  egg  and 
from  blood.  In  various  countries,  egg-yolks  l  are  preserved  in  salt  and  employed  in  different 
industries  (for  tanning,  making  lecithin,  culinary  purposes,  &c.),  and  the  fresh  white  sepa- 
rated is  diluted  with  a  little  water,  beaten  until  it  forms  a  froth,  allowed  to  stand  until 
the  latter  is  destroyed,  filtered  through  woollen  bags,  and  evaporated  in  a  stream  of  air 
at  30°  to  40°  in  large  shallow  pans  ;  after  40  to  60  hours  there  remains  a  thin,  yellowish, 
transparent  pellicle,  which  is  completely  soluble  in  water  and  keeps  without  developing 
any  unpleasant  odour. 

From  fresh  blood  (from  the  butcher's)  pure  albumin  is  separated  with  greater  difficulty. 
The  blood  is  first  allowed  to  undergo  spontaneous  coagulation,  the  blood  globules  and  other 
impurities  thus  collecting  in  a  compact  mass  so  as  to  allow  of  the  ready  decantation  of 
the  faintly  coloured  liquid  serum  containing  the  albumin  ;  or,  after  coagulation,  the  blood 
may  be  introduced  immediately  into  a  centrifugal  separator  (see  p.  395).  The  centrifugcd 
or  decanted  liquid  is  beaten  (without  dilution),  filtered,  decolorised  with  charcoal,  and  dried 
as  above.  In  many  cases  decolorisation  is  difficult,  and  the  albumin  has  to  be  precipitated 
with  lead  acetate ;  the  decanted  precipitate  is  washed  and  suspended  in  water,  which  is 
then  saturated  with  carbon  dioxide,  the  lead  carbonate  being  allowed  to  settle.  The 
clear  albumin  solution  is  treated  with  a  little  hydrogen  sulphide,  which  removes  traces  of 
lead,  and  filtered,  and  the  pure  solution  evaporated  as  with  egg-albumin. 

According  to  Ger.  Pat.  143,042,  the  serum-albumin  is  coagulated  by  means  of 
salt,  dissolved  in  ammonia  and  treated  at  the  boiling-point  with  hydrogen  peroxide,  the 
excess  of  ammonia  being  subsequently  driven  off.  The  method  described  in  Eng.  Pat. 
10,227  (1905)  consists  in  treating  the  serum  successively  with  hydrosulphite,  acetic  acid, 
and  sodium  acetate,  the  liquid  being  then  neutralised  with  ammonia  and  evaporated  as 
usual. 

Albumin  is  used  in  various  industries  :  for  photographic  papers,  in  textile  printing, 
in  printing  titles  in  gold-leaf  on  books,  as  a  clarifying  agent  in  wine-making  (see  p.  156),  &c. 

Egg-albumin  costs,  according  to  its  degree  of  purity,  £24  to  £28  per  quintal.  Blackish 
blood-albumin  is  sold  at  48s.  to  60s.  per  quintal,  the  dark  at  88s.,  the  pale  at  £5  to  £8, 
and  the  pale  powdered  at  128s.  to  208s. 

(2)  GLOBULINS  (of  plants  or  Phytoglobulins,  Serum-globulin,  Lactoglobulin,  &c.) 
are  insoluble  in  water  but  soluble  in  dilute  acid  or  alkali.  At  30°  they  are  precipitated 

1  The  eggs  produced  by  different  breeds  of  hens  are  of  varying  size,  and  weight,  (from  45  to  65  grms.  ;  duck, 
goose,  and  turkey  eggs  weigh  from  twice  to  four  times  as  much)  and  are  composed  of  about  60  per  cent,  of  white, 
30  per  cent,  of  yolk,  and  10  per  cent,  of  shell  (mainly  calcium  carbonate) ;  the  white  contains  86  per  cent,  of  water 
and  13  per  cent,  of  albumin,  and  the  yolk  about  51-5  per  cent,  of  water,  28-5  per  cent,  of  fats,  15-8  per  cent,  of 
proteins  (principally  vitellin),  2  per  cent,  of  salts,  0-45  per  cent,  of  cholesterol,  1-2  per  cent,  of  phosphoglyceric 
acid,  and  0-4  per  cent,  of  extractive  substances.  As  regards  its  nutritive  value,  an  egg  weighing  60  grms.  is  equivalent 
to  50  grms.  of  meat,  while  its  heat  value  is  about  80  calories.  Continuous  evaporation  of  water  takes  place  thiough 
the  shell  of  the  egg,  and  the  volume  of  the  contents  diminishes,  leaving  a  free  air-space — varying  in  size  in  different 
eggs — which  may  be  observed  by  looking  through  the  egg  at  a  candle  flame  in  a  dark  chamber.  Fresh  eggs  are 
also  distinguishable  from  stale  ones  by  the  specific  gravity  :  fresh  eggs  sink  in  a  salt  solution  of  sp.  gr.  1-078,  those 
2  to  3  weeks  old  in  one  of  sp.  gr.  1-060,  those  3  to  5  weeks  old  in  one  of  T050,  and  rotten  eggs  in  one  of  sp.  gr. 
1-015.  It  has  also  been  observed  that  fresh  eggs  float  horizontally  on  a  denser  liquid,  those  4  to  6  days  old 
at  an  angle  of  20°,  those  8  to  10  days  old  at  an  angle  of  about  45°,  and  those  15  to  20  days  old  at  an  angle 
of  60°. 

The  preservation  of  eggs  is  of  considerable  importance,  since  in  summer  eggs  are  abundant  and  cheap,  while  in 
winter  they  are  scarce  and  cost  double  as  much.  A  common  means  of  preservation  formerly  employed  consisted 
in  immersing  the  eggs  in  water  saturated  with  lime  (which  partially  filled  up  the  pores  of  the  shell  with  calcium 
carbonate),  but  in  this  way  they  acquire  an  unpleasant  taste  ;  an  improvement  is  effected  by  adding  5  per  cent,  of 
sodium  chloride  to  the  lime  water.  Others  preserve  them  in  pounded  salt  or  in  salt  and  bran,  pointed  end  down, 
while  others  again  smear  them  with  wax,  vaseline,  and  oil  or  tallow.  Large  quantities  of  eggs  are  now  preserved 
for  some  months  (May  to  November)  by  placing  them  in  thin  layers  on  wooden  lattices  in  cold  chambers,  which 
are  kept  at  a  temperature  of  1°  to  2°  and  a  humidity  of  70°  to  80°,  and  afe  well  ventilated,  preferably  by  means  of 
an  apparatus  producing  ozonised  air.  In  certain  cases  good  results  are  obtained  by  preserving  the  eggs  in  10  per 
cent,  sodium  silicate  solution,  although  such  eggs  often  burst  during  subsequent  boiling.  A  mere  coating  of  the 
silicate  or  of  collodion  is  of  little  avail.  For  transport  eggs  are  arranged  in  layers,  with  alternate  layers  of  old 
straw,  in  wooden  boxes. 

It  is  estimated  that  Italy  produces  from  5,000,000,000  to  6,000,000,000  eggs  (about  60,000,000  being  hens' 
eggs)  and  the  exportation,  which  in  1905  exceeded  320,000  quintals,  worth  about  £1,800,000,  fell  to  228,500  quintals 
in  1907,  a  large  part  of  the  English  market  (to  which  France  sends  more  than  1,000,000,000  eggs)  and  also  of  the 
German  market  (captured  by  Ilussia  and  Denmark)  being  lost. 


PROTEIDS.  737 

unchanged,  completely  by  solutions   of   ammonium  or  magnesium  sulphate  and  partly 
by  sodium  chloride  solution.     Their  solutions  are  coagulated  by  heat. 

(3)  NUCLEO-ALBUMINS  (Vitellin,  Casein,  &c.)  are  acid  in  character  and  decompose 
carbonates  ;    they  are  slightly  soluble  in  water,  but  dissolve  with  formation  of  salts  ,in 
caustic  soda  or  ammonia  and  are  then  coagulated  neither  by  heat  nor  by  alcohol.     They 
contain   phosphorus  (0-85  per  cent,  in  casein)  but  are  distinct  from  the  nucleo-proteins, 
which  give  xanthine  bases  among  their  decomposition  products.     Casein  is  found  in  milk 
(see  p.  385)  and  is  coagulated  by  rennet  or  by  dilute  acids  at  50°  ;  it  is  soluble  in  borax  or 
potassium  carbonate  and  is  rendered  insoluble  by  formaldehyde.     Converted  into  salts 
in  various  ways,  it  is  placed  on  the  market  as  a  concentrated  and  readily  digestible  food 
(plasmon,  nutrose,  tropon,  &c.)  ;  it  is  mixed  with  mineral  colouring- matters  to  make  var- 
nishes.    The  hydrolysis  of  casein  yields  various  amino-acids  and  complex  tribasic  acids 
(Skraup).     Vegetable  caseins  are  also  known. 

To  obtain  pure  caseinin  the  laboratory,  diluted  skim-milk  to  which  0-5  per  cent,  of  acetic 
acid  has  been  added  is  heated  to  55°  to  60°  and  the  precipitated  casein  collected  on  cloth, 
washed  well  with  water,  redissolved  in  very  dilute  ammonia,  decanted  or  filtered  to  remove 
the  undissolved  fat  and  nuclein  and  then  reprecipitated  with  acetic  acid  as  at  first.  It  is 
again  collected  on  cloth,  washed  with  alcohol  and  then  with  ether,  and  dried  in  a  vacuum. 
Prepared  in  this  way,  it  is  free  from  fat,  leaves  less  than  0-5  per  cent,  of  ash  and  contains 
1 5-5  to  18  per  cent,  of  nitrogen.  From  ordinary  casein  a  modification  known  as  paracasein, 
containing  14-8  to  15  per  cent,  of  nitrogen,  may  apparently  be  separated.  Commercial 
casein  (see  p.  385)  contains  less  than  3  per  cent,  of  ash  and  less  than  0-1  per  cent,  of  fat, 
and  costs  64s.  to  80s.  per  quintal.  Riegel  (Ger.  Pat.  117,979  of  1900)  precipitates  it  in  a 
highly  pure  state  from  milk  by  means  of  ethylsulphuric  acid.  Casein  is  detected  on 
textiles  or  paper  by  Adamkiewicz's  reaction,  a  drop  of  a  mixture  of  glyoxylic  and  sulphuric 
acids  being  placed  on  the  surface,  which  is  then  gently  heated  over  a  flame  :  in  presence  of 
casein,  the  drop  of  liquid  assumes  a  transitory  violet-red  colour. 

(4)  PROTEINS  WHICH  COAGULATE  (Fibrinogen,  Myosin,  &c.)  are  distinguished 
by  exhibiting  a  first  coagulation  under  the  influence  of  certain  enzymes  and  a  further 
coagulation  by  heat  or  absolute  alcohol. 

(5)  HISTONES  (Globin,  Nucleo-histone,  &c.)  contain  sulphur  and  are  markedly  basic 
in  character  ;  they  are  precipitated  by  alkalis,  and  in  acid  solution  give  insoluble  compounds 
with  the  albumins.     Nucleo -histories  are  obtained  from  the  leucocytes  of  the  thymus 
gland  and  from  the  testes  of  certain  fish.     The  protein  part  of  the  haemoglobin  molecule 
of  the  red  blood  corpuscles  consists  of  a  histone,  globin.     The  histones  have  certain  pro- 
perties in  common  with  the  peptones  and  albumoses. 

(6)  PROT AMINES  (Salmin,  Clupein,  Sturin,  &c.)  do  not  contain  sulphur  but  contain 
up  to  25  per  cent,  of  nitrogen  and  are  composed  mainly  of  diamino-acids  (arginine)  ;  they 
are  obtained  from  the  spermatazoa  of  many  fishes  (salmon,  herring,  sturgeon,  &c.).     They 
and  the  histones  are  the  least  complex  proteins. 

They  are  still  more  basic  in  character  than  the  histones  and  readily  form  platinichlorides, 
sulphates,  and  picrates,  which  are  all  crystalline.  They  are  precipitated  by  dilute 
alkalis. 

II.  MODIFIED  PROTEINS 

(1)  ALBUMOSES  and  PEPTONES  are  derived  from  true  proteins  by  various  trans- 
formations.    The  albumoses  are  soluble  and  cannot  be  coagulated,  but  are  precipitable 
by  ammonium  sulphate  and  other  salts.  The  peptones  are  regarded  as  the  last  decomposition 
products  of  the  proteins  which  give  protein  reactions  (the  biuret  reaction) ;  on  decomposition 
they  give  amino-acids  without  intermediate  products. 

(2)  SALTS  OF  PROTEINS  (Syntonins  or  Acid-albumins,  Albuminates)  are  markedly 
acid  in  character. 

III.  CONJUGATED  PROTEINS  (PROTEIDS) 

These  represent  combinations  of  proteins  with  other  complex  substances,  and  are 
coagulable  by  alcohol. 

(1)  HAEMOGLOBIN  is  the  colouring-matter  of  red  blood  corpuscles  and  seems  to  be 
composed  of  a  protein  combined  with  a  colouring-matter  containing  iron,  as  it  can  be 
decomposed  into  albumin  and  Haematin,  Pe(C1GH32O2N2)<,,  the  latter  being  a  brown 
II  47 


738  ORGANIC  CHEMISTRY 

substance  containing  8  per  cent,  of  iron.  The  haemoglobin  of  venous  blood  is  of  considerable 
importance  in  respiration,  as  it  combines  very  readily  with  atmospheric  oxygen  (when  the 
blood  traverses  the  lungs)  forming  Oxyhaemoglobin,  which  is  found  in  arterial  blood  and 
carries  the  oxygen  to  the  tissues,  afterwards  returning  to  the  veins.  With  acetic  acid 
and  sodium  chloride  it  gives  hccmatin  hydrochloride  (hcemin)  in  characteristic,  microscopic 
crystals  in  the  form  of  reddish  brown  needles.  Blood-spots  (even  old  ones)  may  be  detected 
by  Teichmann's  test :  to  a  solution  of  the  spot  in  a  little  glacial  acetic  acid  are  added  a 
trace  of  sodium  chloride  and  then  a  small  quantity  of  pure  concentrated  acetic  acid,  the 
liquid  being  heated  to  boiling  on  a  watch-glass  and  one  or  two  drops  of  the  hot  solution 
placed  on  a  microscope  slide  and  allowed  to  evaporate  slowly  in  the  cold  ;  a  drop  of  water 
is  added,  a  cover-glass  applied,  and  the  slide  observed  under  the  microscope.  The  brown 
hsemin  crystals  resemble  barley-corns,  but  are  sometimes  rhombohedral  and  generally 
crossed  in  groups  (Fig.  506)  ;  viewed  in  polarised  light  between  crossed  hicols,  they  appear 
luminous  and  golden  on  a  dark  ground.  They  are  insoluble  in  water  or  cold  acetic  acid, 
but  dissolve  in  alkali. 

Blood-stains  may  also  be  identified  by  means  of  the  catalytic  action  of  the  haemoglobin, 
which  colours  alcoholic  guaiacol  tincture  or  alkaline  phenolphthalein  previously  decolorised 

by  zinc-dust  or,  better,  the   leuco-base  of  malachite  green 

(F-  Michel>  191 1).1 

T.  Gigli  (1910)  states  that  a  very  sensitive  reaction  is 
given  by  a  fresh  mixture  of  3  drops  of  benzidine  (5  per  cent, 
solution  in  acetic  acid)  and  2  drops  of  3  per  cent,  hydrogen 

_„„  TT  .  ,  peroxide  solution  ;  a  blue  coloration  is  given  immediately 

FIG.  506.— Hsemin  crystals  at  £  &  i 

different  magnifications.  by  a  trace  of  blood.  Bardach  and  Silberstem  (1910)  pro- 
pose the  use  of  guaiacum  resin  and  sodium  perborate. 

Oxyhaemoglobin  has  a  composition  differing  little  from  that  of  the  proteins,  but  it 
contains  0-4  per  cent,  of  iron  combined  in  the  ferric  state,  as  with  haemin  and  haematin, 
whilst  the  reduction  product  of  the  latter,  -i.e.  haemoglobin,  is  a  ferrous  compound 
(W.  Kiister,  1910).  In  a  vacuum  (or  under  the  action  of  ammonium  sulphide)  it  loses 
oxygen,  giving  haemoglobin. 

Haemoglobin  forms  a  red  crystalline  powder  soluble  in  water  and  reprecipi table  in 
the  crystalline  state  by  alcohol.  Both  haemoglobin  and  Oxyhaemoglobin  give  characteristic 
absorption  spectra. 

Haemoglobin  and  also  its  ash  exert  a  catalytic  action  in  certain  combustion  phenomena  ; 
e.g.  sugar  moistened  with  a  little  human  blood  burns  with  great  energy. 

When  a  current  of  carbonic  oxide  is  passed  into  a  solution  of  red  Oxyhaemoglobin 
(defibrinated  blood)  the  oxygen  isx  displaced  and  the  liquid  assumes  a  violet-red  colour, 
carboxyhcemoglobin — which  can  be  obtained  in  bluish  crystals — being  formed.  An  aqueous 
solution  of  this  compound  (blood  poisoned  with  carbonic  oxide)  gives  two  characteristic 
absorption  bands  between  the  D  and  E  lines  of  the  spectrum,  and  these  bands  do  not  unite 
or  disappear — as  happens  in  the  case  of  Oxyhaemoglobin — when  a  few  drops  of  ammonium 
sulphide  are  added  to  the  solution.  Haemoglobin  itself  gives  a  single  absorption  band 
between  the  D  and  E  lines. 

(2)  NUCLEOPROTEINS  or  Nucleins  have  a  pronounced  acid  character  and  are 
insoluble  in  water  and  acids,  but  soluble  in  alkali.  They  represent  compounds  of  proteins 

1  Blood-spots  may  also  be  detected  by  means  of  hydrogen  peroxide  :  it  is  sometimes  sufficient  to  press  a  piece 
of  moistened  filter-paper  on  the  dry  blood-spot  and  then  to  immerse  it  in  hydrogen  peroxide  solution,  to  obtain  a 
copious  evolution  of  oxygen. 

To  ascertain  from  what  animal  the  blood  comes,  and  in  general  to  discover  if  it  is  human  blood,  Uhlonhuth's 
test  (1909),  based  on  the  formation  of  different  antitoxins  in  different  animals  (see  p.115)  serves.  Tristovitch  and 
Bordet  (1899)  showed,  indeed,  that  if  an  extraneous  serum  (e.g.  human)  is  injected  in  several  doses  into  the  blood 
of  an  animal  (e.g.  a  guinea-pig),  the  serum  of  this  animal  (antiserum)  ultimately  acquires  the  property  of  precipitating 
(or  rendering  turbid  in  the  case  of  dilute  serum  or  dilute  blood)  the  blood  of  the  animal  which  furnished  the  injected 
serum  (e.g.  man).  If  even  a  very  dilute  solution  of  blood  (obtained,  for  instance,  by  extracting  a  dried  blood-spot 
with  a  little  water)  is  cleared  by  filtration  and  treated  separately  with  different  clear  antiserums  to  ascertain  with 
which  of  them  a  turbidity  is  produced,  it  can  be  stated  with  certainty  Wiat  the  blood-spot  was  derived  from  the 
animal  whose  serum,  when  injected  into  the  guinea-pig,  produced  the  antiserum  rendering  the  blood  solution  turbid. 
The  test  must  be  applied  very  carefully  and  with  parallel  control  experiments  ;  it  does  not  distinguish  between 
the  bloods  of  similar  animals,  e.g.  hens  and  pigeons,  sheep  and  goats,  apes  and  men.  The  difference  between 
various  species  becomes  more  evident  when  dilute  solutions  or,  better,  dilute  blood  and  a  little  concentrated  anti- 
serum  are  employed.  All  these  phenomena,  studied  by  Uhlenhuth,  and  subsequently  by  others,  are  based  on  the 
precipitation  of  the  albuminoid  substances  of  the  different  serums  (precipitins),  and  they  allow  of  the  determination 
of  the  character  of  blood-spots  sixty  years  old.  Clear  solutions  and  sterilised  vessels  are  always  used  for  the 
test. 


ALBUMINOIDS 

with  a  Nucleic  Acid,  which  is  phosphoric  acid  neutralised  partially  by  basic  organic  groups, 
such  as  xanthine,  guanine,  &c.  The  nucleins  contain  5-7  per  cent.  P,  41  per  cent.  C,  and 
31  per  cent.  O,  and  are  hence  sharply  distinguished  from  true  proteins  although  they  give 
the  same  colour  reactions.  They  form  the  fundamental  constituents  of  cell  nuclei. 

(3)  GLUCOPROTEINS  are  acid  in  character  and  are  formed  of  a  protein  combined 
with  a  sugar  derivative.  They  are  insohible  in  water  and  with  a  little  lime-water  give 
neutral,  frothy,  and  ropy  solutions  which  are  not  coagulated  by  heat  or  by  nitric  acid. 
When  hydrolysed  with  alkali  or  acid  they  yield  sugar,  peptones,  and  Syntonins. 

These  compounds,  which  are  poor  in  nitrogen  (11-7  to  12-3  per  cent.),  include  the 
Mucins. 

IV.  ALBUMINOIDS 

These  constitute  the  fundamental  parts  of  the  cartilaginous  tissues  and  epidermis  of 
animals  and  comprise : 

(1 )  ELASTIN,  which  forms  the  elastic  part  of  the  tendons  and  ligaments,  is  insoluble 
in  dilute  acid  or  alkali,  but  with  the  latter  loses  the  whole  of  its  sulphur. 

(2)  KERATIN  is  the  principal  constituent  of    the  nails,  horns,  feathers,  epidermis, 
hair,  &c.      It  is  insoluble  in  water,  but  when  heated  under  pressure,  best  in  presence  of 
alkali,  it  dissolves  with  partial  decomposition.      It  contains  4-5  per  cent,  of  sulphur,  which 
is  eliminated  to  some  extent  by  boiling  water. 

With  nitric  acid  it  gives  the  yellow  xanthoprotein  reaction  (see  above,  Blood-spots  on 
skin  treated  with  nitric  acid). 

(3)  The  COLLAGENS  are  abundant  in  bones,  hair,  tendons,  and    cartilage.     They 
combine  with  water  at  the  boiling-point  and  dissolve,  forming  ordinary  glue  or  gelatine, 
which  is  precipitated   by  tannin  or  by  mercuric  chloride  acidified  with  HC1  but  not  by 
mineral  acids.     They  contain  stably  combined  sulphur.      They  consist,  to  the  extent  of 
85  per  cent.,  of  amino-acids  (Skraup,    Biehler  and   Bottcher,  1909-1910),  and,  like  the 
protamines,  are  true  proteins  containing  methoxy-  and  azomethyl-groups.     Unlike  casein, 
they  give  little  glutamic  acid  on  hydrolysis.      On  hydrolysing  them  with  caustic  baryta, 
E.  Fischer  and  R.  Boehner  (1910)  obtained  Proline  [a-pyrrolidinecarboxylic  acid)  as  primary 
product ;  a -Amino-o-hydroxy  valeric  Acid,  which  is  obtained  from  gelatine,  does  not  give 
proline  with  baryta.      By  digesting  gelatine  with  trypsin,  Levene  (1910)  obtained  mainly 
Prolylglycocoll  Anhydride.     The  absorptive  power  of  the  collagens  for  carbon  disulphide, 
which  in  presence  of   alkali  leads  to  thiohydration,  allows  of  their  differentiation  from 
agglutinating    substances  (Sadikow,  1910)  ;    the  agglutination  of  gelatine  is  not  only  a 
disgregation  of  the  collagen  molecule,  but  also  a  condensation  of  the  side-chains.     Gelatine 
which  has  undergone  prolonged  exposure  to  light  loses  some  of  its  absorptive  power  for 
water  owing  to  the  formation  of  formaldehyde,  which  hardens  the  glue  (Meisling,  1909). 
On  hydrolytic  decomposition,  the  collagens  give  glycocoll  (while  the  albumins  give  tyrosine), 
leucine,  glutamic  acid,  and  asparagine.1     Very  dilute  solutions  of  glue  give,  with  boiling 
ammonium  molybdate  solutions,  a  characteristic  precipitate  and  coloured  solution,  which 
may  be  applied  to  quantitative  estimations  (E.  Schmidt,  1910). 

1  Manufacture  of  Glue  and  Gelatine.  The  prime  materials  are  bones  and  hide  waste,  generally  untanned 
and  preserved  with  lime.  From  bones  the  fat  is  first  extracted  (see  p.  392  and  also  vol.  i,  p.  508),  and  the  crushed 
bones  then  heated  for  a  couple  of  hours  in  a  large  autoclave  with  water  and  steam  under  pressure,  so  as  to  convert 
the  ossein  into  soluble  gelatine  ;  this  treatment  is  repeated  two  or  three  times,  the  final  more  dilute  solutions  being 
used  for  a  subsequent  operation.  In  some  cases,  however,  the  bones  and  hence  also  the  glue  are  freed  from  calcium 
phosphate  by  treatment  with  four  times  their  weight  of  6  to  7  per  cent,  hydrochloric  acid  (sp.  gr.  1-05)  until  complete 
softening  occurs  ;  the  calcium  phosphate  is  precipitated  from  the  solution  by  means  of  lime  and  calcium  carbonate, 
while  the  ossein,  placed  in  a  double-bottomed  vessel  heated  by  steam,  is  rapidly  converted  into  a  solution  of  glue. 
According  to  Ger.  Pat.  144,398,  the  calcium  phosphate  maybe  dissolved  by  aqueous  SO2  under  pressure  (only 
the  treatment  under  pressure  is  patented).  The  solution  obtained  by  either  of  these  methods,  with  a  concentration 
of  17°  to  18°  on  the  glue-densimeter  in  summer  and  12°  to  14°  in  winter,  can  be  partly  decolorised,  while  still  hot, 
by  a  current  of  sulphur  dioxide  ;  it  is  then  introduced  into  zinc  moulds  surrounded  by  cold  water  to  solidify.  The 
solidification  of  these  solutions  (and  even  more  dilute  ones)  is  now  hastened  by  refrigeration.  The  solid  blocks 
of  glue  are  then  cut  into  suitable  sizes  and  dried  on  wide-meshed  nets  arranged  on  trolleys,  which  are  placed  in 
chambers  through  which  air  at  25°  to  30°  is  circulated  by  means  of  fans.  If  the  air  is  above  this  temperature 
the  glue  will  melt,  while  if  it  is" too  dry  the  cakes  are  deformed.  On  this  account  and  also  because  it  would  readily 
putrefy,  glue  is  not  made  in  summer.  Dry  bone-glue  contains  15  to  20  per  cent,  of  water  and  costs  52».  to  68«. 
per  quintal. 

Skin-glue  (leather  glue)  is  prepared  from  hide-waste  and  also  other  waste  (nerves,  cartilage,  Ac.)  by  defatting 
with  carbon  disulphide  and  softening  or  swelling  in  water,  which  likewise  removes  impurities.  It  is  then  macerated 
for  three  weeks  in  a  series  of  vessels  containing  milk  of  lime,  which  is  frequently  renewed  to  eliminate  any  remaining 
fat,  blood,  &c.  It  is  then  thoroughly  washed  in  water  and  the  last  traces  of  lime  (which  would  make  the  glue 
turbid)  removed  by  means  of  dilute  hydrochloric  acid,  or,  better,  of  sulphur  dioxide  or  phosphoric  acid.  The 


740  ORGANIC    CHEMISTRY 

V.  VARIOUS   PROTEINS 

Spongin  enters  into  the  formation  of  sponges  ;  its  hydrolytic  products  approximate 
more  to  those  of  the  collagens  than  to  those  of  the  albumins,  but  they  are  more  resistant 
to  the  action  of  soda  and  baryta  than  collagens.  Cornein  constitutes  coral  and  gives 
leucine  on  hydrolysis.  Fibroin  and  Sericin  are  obtained  from  silk  (see  p.  692)  ;  fibroin 
dissolves  in  energetic  alkalis  with  elimination  of  ammonia  and  formation  of  Sericoin,  and 
when  completely  hydrolysed  it  yields  tyrosine  and  glycocoll  but  not  leucine. 

The  Enzymes  (see  p.  Ill)  belong  to  the  group  of  complex  albumins. 

GLUCOSIDES  AND  OTHER  SUBSTANCES  OF  UNCERTAIN 
OR  UNKNOWN  COMPOSITION 

Glucosides  have  been  denned  and  the  synthesis  of  artificial  glucosides  described  on 
pp.  432  and  437.  They  are  compounds  of  aromatic  or  aliphatic  compounds  with  carbo- 
hydrates. In  vegetable  organisms  these  glucosides  form,  according  to  Pfeffer,  difficultly 
dialysable  substances  which  serve  the  plants  as  reserve  material,  gradually  becoming 
utilisable  as  they  are  decomposed  by  the  various  enzymes  occurring  in  other  cells.  This 
was  well  shown  by  T.  Weevers  (1903  and  1908)  for  Salicin,  which  is  decomposed  (by  emulsin) 
into  glucose  and  saligenin  (hydroxy benzyl  alcohol),  the  latter  being  probably  further 
transformed  into  a  final  product  known  as  Catechol.  The  latter  is  a  phenol  found  throughout 
the  whole  plant  (e.g.  Salix  purpurea),  and  its  quantity  is  inversely  proportional  to  that  of 
the  salicin  present ;  it  is  possible  that  it  reacts  with  fresh  quantities  of  glucose  regenerating 
salicin.  While  the  sugars  are  gradually  utilised  in  the  growth  of  the  plant,  the  aromatic 
group  (which  serves  as  a  reserve  of  carbon  for  bacteria  but  not  for  enzymes)  is  used  in  the 
continuous  reconstruction  of  the  glucoside.  So  that  plants  are  able  to  prepare  reserve 
materials  in  different  ways  :  when  the  carbohydrates  are  not  utilised,  they  are  transformed 
into  insoluble  starch,  or  into  glycogen,  or  into  glucosides. 

AMYGDALIN,  already  mentioned  on  p.  113,  has  a  composition  corresponding  with 
C20H270UN  and  forms  colourless  crystals  which  are  soluble  in  water  and  melt  at  200°. 

waste  prepared  in  this  way  is  treated  with  hot  water  and  steam  in  wooden  vessels  with  false  bottoms  and  the  first 
solutions,  showing  densities  of  16°  to  20°  on  the  glue-densimeter,  are  solidified  in  moulds  as  above.  The  two 
or  three  succeeding  extracts,  which  are  more  dilute,  are  concentrated  to  20°  to  22°  in  a  single  or  multiple-effect 
vacuum  apparatus  (see  p.  461),  surmounted  by  a  column  with  perforated  discs  to  break  up  the  froth,  and  are  then 
allowed  to  set.  Good  results  are  now  obtained  with  Kestner  concentrators  (see  vol.  i,  p.  443).  The  waste  used 
gives  about  one-third  of  its  weight  of  dry  glue,  which  is  sold  at  96«.  to  128*.  per  quintal.  The  finer  qualities,  filtered, 
decolorised,  and  prepared  from  pure,  fresh,  raw  materials,  bear  the  name  of  gelatine  and  cost  £6  to  £12  per  quintal.t 

In  order  to  utilise  tanned  hides  in  the  manufacture  of  glue  it  is  necessary  to  untan  them  by  successive  treatment 
with  dilute  alkali  solution,  water,  and  lime ;  if  chrome  tanned,  they  are  treated  first  with  dilute  sulphuric  acid, 
then  with  an  abundant  supply  of  water  and  finally  with  lime.  In  either  case,  the  remaining  traces  of  lime  arc 
removed  by  means  of  dilute  HC1,  the  latter  being  eliminated  by  treatment  with  alkali  and  washing  with  water 
(Eng.  Pat.  22,738  of  1902). 

Fish-glue  is  obtained  from  the  well-purified  swimming-bladders  of  various  species  of  Acipenser,  especially 
of  Acipenser  sturio  (sturgeon),  by  treatment  with  acid,  lime,  steam,  water,  <fcc.  According  to  Ger.  Pat. 
131,315,  the  blubber  of  whales  may  also  be  used.  Fish-glue  costs  double  or  treble  as  much  as  the  best  qualities 
of  other  glue. 

Liquid  glue  is  obtained  by  the  protracted  heating  of  glue  with  its  own  weight  of  water  and  one-fourth  or  one- 
third  of  its  weight  of  hydrochloric,  acetic,  or  nitric  acid  (the  last  at  35°  Be. ;  the  nitrous  fumes  must  be  carried 
away  by  a  good  draught).  F.  Supf  (Ger.  Pat.  212,346  of  1908)  obtains  liquid  glue  by  treating,  say,  450  kilos  of 
glue  with  120  kilos  of  sodium  naphthalenesulphonate. 

Glue  is  analysed  by  determining  the  ash  (2  to  3  per  cent.)  and  the  increase  in  weight  caused  by  immersion  for 
12  hours  in  cold  water  (in  which  it  should  not  dissolve),  the  best  qualities  absorbing  most  water  and  swelling. 
The  ash  of  bone-glue  has  an  almost  neutral  reaction,  and  chlorides  and  phosphates  are  found  in  its  nitric  acid  solution. 
The  ash  of  hide-glue  does  not  melt,  has  an  alkaline  reaction,  and  contains  little  or  no  phosphoric  acid.  The  aqueous 
solution  of  pure  glue  has  a  neutral  or  very  faintly  acid  reaction,  while  those  of  the  more  impure  kinds  are  sometimes 
alkaline.  Glue  should  be  completely  soluble  in  hot  water,  any  undissolved  part  representing  impurity.  The 
moisture  content  of  dry  glue  should  not  exceed  15  to  18  per  cent,  (lost  at  105°).  The  best  qualities  melt  at  the 
highest  temperatures  and  the  dropping-point  may  be  determined  by  Ubbclohde's  apparatus  (see  p.  6),  using  a  larger 
vessel.  The  relative  adhesive  powers  of  different  glues  may  be  estimated  by  preparing  tepid  solutions  of  equal 
concentrations,  immersing  pieces  of  cotton  or  woollen  fabric  (of  equal  weights  and  areas)  in  them  for  two  or  three 
minutes,  centrifuging  the  fabrics  at  the  same  time  in  the  same  centrifuge,  ironing  them  slightly  with  a  hot  iron, 
drying  completely  in  an  oven  at  100"  and  then  noting  which  of  the  fabrics  adheres  best  and  longest  to  the  fingers. 

Statistics.  Italy  has  a  protective  duty  of  38<i.  per  quintal  on  glue  and  12s.  per  quintal  on  fish-glue.  In  1904 
the  exports  were  11,000  quintals  of  glue  (11,700  in  1902)  and  the  imports  10,600  (more  than  one-half  from  Austria), 
besides  800  quintals  of  gelatine  and  41  of  fish-glue.  The  industry  in  Italy  is  injured  by  the  competition  of  the 
Austrians,  who  have  a  protective  duty  of  8s.  per  quintal  on  glue  and  purchase  nearly  all  the  bones  in  Italy  (16,600 
quintals  in  1903  ;  29,400  in  1904  ;  50,000  in  1905).  Austria  competes  also  with  Germany. 

In  1905  Germany  exported  63,300  quintals  of  glue  and  gelatine  at  an  average  price  of  52s.  per  quintal  and 
imported  45,000  quintals  at  44s.  per  quintal. 


GLUCOSIDES,    ETC.  741 

It  is  found  in  the  stones  of  various  fruits  (cherries,  peaches,  bitter  almonds,  &c.)  and  in 
the  leaves  of  the  cherry-laurel.  When  hydrolysed  by  acids  or  enzymes  (see  pp.  Ill  and 
112),  it  yields  dextrose,  prussic  acid,  and  benzaldehyde. 

SAPONIN,  C32H52O17,  is  obtained  from  Saponaria  root,  quilaya  bark,  and  the  Indian 
chestnut.  It  is  used  for  washing  garments  in  place  of  soap,  and  is  also  employed  to  produce 
a  persistent  froth  (e.g.  to  give  a  head  to  beer).  It  is  soluble  in  water,  has  an  irritating 
taste  and  smell,  and  dissolves  red  blood  corpuscles  (is  hence  poisonous).  It  is  extracted 
in  various  ways  according  to  Ger.  Pats.  116,591,  144,760,  and  156,954.  The  crude  product 
costs  9s.  Qd.  per  kilo  ;  the  purified,  20s.,  and  the  puriss.,  40s. 

DIGITALIN,  C35H56O14  (?)  ;  DIGITONIN,  C27H46O14,  and  DIGITOXIN,  C31H54OU, 
are  the  most  important  constituents  of  the  foxglove  (Digitalis  purpurea)  and  are  used  in 
medicine,  especially  for  diseases  of  the  heart.  Pure  digitalin  costs  Wd.  per  gramme,  and 
crystallised  digitoxin  20s.  per  gramme. 

SALICIN,  C13H18O7  (see  p.  574),  is  contained  in  several  varieties  of  Salix,  and  on 
hydrolysis  gives  glucose  and  saligenin  (see  pp.  574,  582)  ;  with  nitrous  acid  it  forms  Helicin, 
C13H16O7  +  H2O,  which  can  also  be  obtained  synthetically  from  glucose  and  salicylic 
aldehyde. 

jESCULIN,  C15H,  6O9,    is    obtained  from  horse-chestnut  bark,  and  is  the  glucoside 

,CH  :  CH      . 
of  ^ESCULETIN  (aDihydroxycoumarin),  C6H2(OH)2\  |    ,  which  is  isomeric  with 

XO—  CO 
daphnetin. 

POPULIN,  C20H22O8  +  2H2O,  is  a  Benzoylsalicin,  and  is  obtained  synthetically  from 
salicin  and  benzoyl  chloride  ;  it  occurs  naturally  in  Populus. 

HESPERIDIN,  C22H26O12,  occurs  abundantly  in  the  bitter  orange,  and  on  decom- 
position gives  phloroglucinol,  glucose,  and  Ferulic  Acid,  which  is  the  monomethyl  ether  of 
OH_ 

Caffeic  Acid,  HO/         X>—  CH  :  CH  •  C02H. 


PHLORETIN,  C15H14O5,  and  its  glucoside,  PHLORIDZIN,  C21H24O10,  are  found  in 
plants,  and  in  cases  of  glycosuria  in  animals. 

IRIDIN,  C24H26O13,  is  found  in  the  roots  of  the  Florentine  iris  and  yields  Irigeninand 
glucose  on  hydrolysis. 

ARBUTIN,  C12H]6O7,  occurs  in  the  leaves  of  the  bear-berry  and  gives  glucose  and 
hydroquinone  on  hydrolysis.  Methylarbutin  gives  glucose  and  methylhydroquinone. 

CONIFERIN,  C16H22O8  +  2H2O,  is  hydrolysed  to  glucose  and  Coniferyl  Alcohol, 
which  gives  vanillin  on  oxidation.  It  is  found  in  the  sap  of  Coniferce. 

SINIGRIN  (Myronic  Acid),  C10H17O9NS2  ;  hydrolysis  of  its  potassium  salt,  which 
occurs  in  black  mustard  seed,  gives  glucose,  potassium  bisulphate,  and  allyl  mustard 
oil. 

SANTONIN,  C15H18O3  ;  its  constitution  has  been  studied  more  especially  by  Canniz- 
zaro  and  his  pupils.  It  is  a  naphthalene  derivative  and  is  found  in  worm-seed  (santonica). 

ALOIN,  C17H1807,  an  anthracene  derivative,  occurs  in  aloes  and  is  a  strong  pur- 
gative. 

LECITHIN  (composition,  see  p.  374)  is  a  characteristic  component  of  egg-yolk  and  of 
brain  and  nerve  matter  and  is  a  crystalline  waxy  substance,  which  dissolves  in  alcohol 
or  ether  and  with  water  forms  an  opalescent  liquid.  When  hydrolysed  it  yields  glycero- 
phosphoric,  oleic,  and  palmitic  acids,  together  with  choline.,  and  it  may  therefore  be 
regarded  as  a  glyceride  (see  pp.  183,  372). 

Considerable  use  has  been  made  of  it  (and  also  of  bromo-  and  iodo-lecithin)  in  recent 
years  as  a  medicine.  Lecithin  is  extracted  on  the  large  scale  from  egg-yolk,  and  new 
processes  are  described  in  Fr.  Pats.  371,391  and  406,634  of  1908.  Pure  lecithin  costs  up 
to  £8  per  kilo. 

CEREBRIN,  C17H:!3O3N,  occurs  in  the  nerves. 

IODOTHYRIN  (see  vol.  i,  p.  151)  is  the  iodine  compound  of  the  thyroid  gland. 

Bile  Compounds  include  TAUROCHOLIC  ACID,  C26H45O7NS,  and  GLYCOCHOLIC 
ACID,C26H43O6N,  as  sodium  salts.  When  decomposed  by  alkali,  both  acids  yield  Cholic 
Acid,  OH-C2iH32(CH2-OH)2(CO2H),  glycine  and  taurine.  Bile  also  contains  colouring, 
matters  such  as  BILIVERDIN,  BILIFUCHSIN,  and  BILIRUBIN,  Ct«Hi,O4N,. 


ORGANIC    CHEMISTRY 

CANTHARIDIN,  C10H12O4,  occurring  in  cantharides,  causes  blistering  of  the  skin, 
and  sublimes  in  thin  scales. 

CHITIN  forms  the  skeletal  matter  of  crustaceans.  It  is  insoluble  in  alkali  (unlike 
keratin)  and  when  hydrolysed  by  acid  gives  a  glucosamine.  Fusion  with  potash  at  184° 
yields  acetic  acid  and  Chitosan,  which  also  forms  the  glucosamine  with  acid. 

CHOLESTEROL,  C27H460,  occurs  in  many  plants  and  animals  (that  of  plants  is  called 
Phytosterol),  generally  together  with  fats  and  oils  ;  certain  physical  differences  but  virtually 
no  differences  in  chemical  behaviour  are  observable  in  products  of  different  origin.  Its 
constitution  has  not  been  definitely  established,  but,  owing  more  especially  to  the  investi- 
gations of  A.  Windaus,  many  of  its  component  groups  have  been  ascertained.  A  doubt 
whether  the  complex  contained  one  or  two  double  linkings  formerly  existed,  but  the  addition 
of  ozone  (Molinari  and  Fenaroli,  1908)  shows  the  presence  of  two  such  linkings  in  both 
phytosterols  and  other  cholesterols. 

It  forms  shining  scales  melting  at  147°,  and  in  constitution  it  resembles  the  terpenes 
more  than  the  substances  of  any  other  group,  but  in  all  probability  it  does  not  contain 
benzene  groups.  Minimal  quantities  of  cholesterol  may  be  detected  by  Tschugajew's 
reaction,  which  consists  in  the  formation  of  a  more  or  less  intense  red  coloration  when  a 
small  quantity  of  a  substance  containing,  cholesterol  is  poured  into  fused  anhydrous  tri- 
chloroacetic  acid.  In  alcoholic  solution,  cholesterol  and  phytosterol  (but  not  their  ethers) 
form  an  insoluble  compound  with  Digitonin  ;  this  reaction  serves  for  the  estimation  of  these 
substances  and  for  their  separation  from  other  animal  and  vegetable  organic  compounds, 
such  as  hydrocarbons,  &c. 


INDEX 


ABRIN,  115 

Abrus  praecatorius,  115 

Accumulators,  Hydraulic,  393 

Acenaphthene,  614 

Acer  saccharinum  nigrum,  443 

Acetaldehyde,  208,  567 

Estimation,  209 
Acetals,  205,  437 
Acetamide,  198,  362 
Acetamidine,  357 
Acetamido -chloride,  356 
Acetanilide,  556,  560 
Acetates,  284-287 
Acetic  anhydride,  320 
Acetifiers,  283 
Acetimino-chloride,  356 
Acetiminothiomethyl  hydriodide,  357 
Acetins,  214,  223 
Acetoacetaldehyde,  334 
Acetobromamide,  352 
Acetochlorhexoses,  438 
Acetometers,  284 
Acetonamines,  210 
Acetone,  107,  211 
Acetonealcohol,  333 
Acetonitrile,  198,  199 
Acetonylacetone,  333,  334 
Acetophenone,  572 
Acetophenoneacetone,  572 
Acetoxime,  210 
Acetyl  chloride,  319 

iodide,  319 

number,  188,  189 
Acetylacetone,  334 
Acetylcarbinol,  333     • 
Acetylene,  92 

hydrocarbons,  90 
Acetylethylamine,  351 
Acetylglycocoll,  355 
Acetylhydrazides,  358 
Acetylides,  91,  301 
Acetyl-p-phenetidine,  564 
Acetylthiourea,  365 
Acetylourea,  364 
Achroodextrin,  116 
Acianilides,  556 
Acichlorides,  317 
Acid,  Abietic,  173,  596 

Acetaldehydedisulphonic,  213 

Acetic,  270 

Acetoacetic,  332 

Acetonediacetic,  345 

Acetonedicarboxylic,  344 

Acetonetricarboxylic,  351 

Acetonic,  326 

Aceturic,  323,  355 

Acetylenecarboxylic,  301 

Acetylenedicarboxylic,  315 

Acetylsalicylic,  582 

Aconitic,  315,  345 

Acridic,  636 

Acrylic,  294 

Adipic,  297,  302,  614 

Alkylphosphonic,  202 


743 


Acid,  Allanturic,  366 
Allocinnamic,  580 
Allocrotonic,  295 
Allophanic,  364 
Alloxanic,  366 
7-Allylbutyric,  297 
Allylsuccinic,  312 
Aminoacetic,  317,  322,  355 
o-Aminobenzoic,  578 
Aminoethylsulphonic,  214 
a-Aminoglutaric,  356 
a-Amino-/3-hydroxypropionic,  355 
a-Amino-5-hydroxyvaleric,  739 
a-Aminopropionic,  354 
Aminosuccinic,  355 
a-Amino-/3-thiolactic,  332 
Amylacetylenecarboxylic,  300 
Amylmalonic,  308 
Angelic,  296 
Anilidoacetic,  560 
Anisic,  577,  582 
Anthraflavinic,  616 
Anthranilic,  578,  643 
Arabonic,  328,  430 
Arachidic,  265,  398 
Aspartic,  355 
Atropic,  577 
Azelaic,  305,  311 
Azulmic,  359 
Barbituric,  366,  368 
Behenic,  265 
Behenolic,  300,  302 
Benzenecarboxylic,  575,  577 
Benzenehexacarboxylic,  575,  581 
Benzenehexamethanoic,  575 
Benzenemethanoic,  575 
Benzenestearosulphonic,  410 
Benzenesulphonic,  524,  538 
Benzhydroxamic,  578 
Benzilic,  606 
Benzoic,  525,  575,  576 
Benzoylacetic,  577 
Benzoylformic,  577 
Bornylenecarboxylic,  603 
Brassidic,  300 
Brassylic,  300,  305 
Bromosuccinic,  313 
Butylacetylenecarboxylic,  300 
Butylfumaric,  312 
Butylmaleic,  312 
Butylmalonic,  308 
Butylsuccinic,  310 
Butyric,  288 
Cacodylic,  202 
Caffeic,  584,  741 
Caffetannic,  369 
Camphoric,  602 
Camphoronic,  315,  602 
Capric,  289 
Caproic,  289 
Caprylic,  289 
Carbamic,  363 
Carbaminic,  363 
Carbolic,  541 


744 


INDEX 


Acid,  o-Carboxyhydrocinnamic,  614 
Carminic,  668 
Cerotic,  290,  373 
Cetylmalonic,  308 
Chelidonic,  626 
Chloroacetic,  317 
Chlorobenzoic,  578 
a-  (/3-  7-)  Chlorobutyric,  318 
Chlorocarbonic,  363 
a-  (^3-)  Chloropropionic,  318 
Cholic,  741 

Cinchomeronic,  626,  637 
Cinchonic,  636 
Cinnamic,  575,  576,  579 
Citraconic,  20,  312,  314 
Citramalic,  335 
Citric,  345 
Citronellic,  297 
Citrylideneacetic,  304 
Comanic,  626 
Coumalinic,  626 
Coumaric,  577,  583 
Coumarinic,  583 
Crotonic,  20,  295 
Cuminic,  577 
Cyanic,  359 
Cyanoacetic,  318 
Cyanuric,  359,  362 
Cyclogeranic,  303 
Decamethylenedicarboxylic,  305 
Decoic,  289 

Dehydroundecenoic,  300 
Desoxalic,  351 
Diacetosuccinic,  345 
Diacetylenedicarboxylic,  315 
Diacetylglutaric,  345 
Dialkylphosphonic,  202 
Diallylacetic,  303 
Dialuric,  366 
a6-Diaminovaleric,  328 
Diaterebinic,  335 
Diazobenzenesulphonic,  568 
Dibasic  quinolinic,  636 
Dibenzhydroxamic,  553 
^7-Dibromobutyric,  295 
/3/3-Dibromopro  picnic,  318 
Dicetylmalonic,  308 
Dichloracetic,  318 
aa-  (a/3-)Dichloropropionic,  318 
Diethylmaleic,  312 
Diethylmalonic,  308 

Digallic,  584 

Diglycollic,  322 

a/3-Dihydroxybutyric,  295 

Dihydroxymalonic,  344 

ajS-Dihydroxypropionic,  328 

Dihydroxystearic,  299,  328 

Dihydroxytartaric,  344 

Diisoamylmalonic,  308 

Diisobutylmalonic,  308 

Dimethylacetic,  288 

a/3-Dimethylacrylic,  296 

Dimethylarsenic,  202 

Dimethylfumaric,  312,  314 

aa-  (ay-,  77-)  Dimethylitaconic,  312 

Dimethylmaleic,  312,  314 

Dimethylmalonic,  308 

Dimcthyloxaminic,  200 

Dimethylparabanic,  367 

Dimethylpseudouric,  368 

Dimethylsuccinic,  310 

Dimethyltrihydroxycinnamic,  632 

Dinicotinic,  626 

Dioctylmalonic,  308 


Acid,  Diphenic,  606,  619 
Diphenylacetic,  606 
Diphenylcarboxylic,  572 
Dipicolinic,  626 
Dipropylmalonic,  308 
Dithiocarbamic,  365 
Dithiocarbonic,  364 
Dithiocarbonylic,  365 
Dodecamethylenedicarboxylic,  305 
Durenecarboxylic,  577 
Durylic,  577 
Elseostearic,  304 
Elaidjc,  298 
-      Erucic,  300 
Erythric,  328 
Ethanetricarboxylic,  345 
Ethanthiolic,  351 
Ethanthiolthiolic,  351 
Ethylacetylenecarboxylic,  300 
Ethylcarbonic,  363 
Ethyleneaminosulphonic,  356 
Ethylenelactic,  325 
Ethylenesuccinic,  310 
Ethylfumaric,  312 
Ethylhydroxamic,  358 
Ethylideneacetic,  295 
Ethylidenelactic,  323,  325 
Ethylidenepropionic,  296 
Ethylidenesuccinic,  311 
Ethylisopropylmalonic,  308 
a-  (7-)  Ethylitaconic,  312 
Ethylmaleic,  312 
Ethylmalonic,  308 
Ethylmethylacetic,  289 
Ethylnitric,  198 
Ethylsulphonic,  197 
Ethylsulphuric,  89,  197 
Ethylsulphurous,  197 
Euxanthinic,  668 
Ferulic,  584,  741 
Flaveanhydric,  359 
Formic,  268 

Formothiohydroxamic,  360 
Formylacetic,  326,  329 
Fulminic,  360 
Fumaric,  21,  312,  313 
Galactonic,  328,  437 
Gallic,  577,  583 
Gallolylgallic,  584 
Gallotannic,  584 
Geranic,  303 
Glucoheptonic,  329 
Gluconic,  328,  433,  438 
Glutaconic,  312,  314 
Glutamic,  356 
Glutaric,  305,  311 
Glyceric,  185,  328 
Glycerophosphoric,  214 
Glycocholic,  741 
Glycolglycollic,  322 
Glycollic,  322 
Glycolsulphuric,  213 
Glycoluric,  364 
Glycuronic,  329 
Glyoxylic,  329 
Gulonic,  328 
Hemcllitic,  577 
Hemirngllitic,  581 
Heptoic,  289 

Heptylacetylenecarboxylic,  300 
Heptylsuccinic,  310 
Hexahydrotetrahydroxybenzoic,  59 
Hexahydroxystearic,  304 
Hexantetroloic,  328 


INDEX 


745 


Acid,  Hexylacetylenecarboxylic,  300 
Hexylsuccinic,  310 
Hippuric,  355,  576,  578 
Homocamphoric,  603 
Hydantoic,  364 
Hydracrylic,  325 
Hydratropic,  577 
Hydrazoic,  366 
Hydrochelidonic,  345 
Hydrocinnamic,  577 
Hydrocyanic,  358 
Hydromellitic,  581 
Hydromucic,  312 
Hydro muconic,  315 
Hydroparacoumaric,  577 
Hydro xyacetic,  317,  322 
/3-Hydroxyacrylic,  326,  329 
Hydroxybenzoic,  577,  582 
a-  (/3-)  Hydroxybutyrio,  326 
a-Hydroxycaproic,  326 
o -Hydro xycinnamic,  583 
Hydroxycitric,  351 
Hydro xyethylsulphonic,  213 
Hydroxygallolylgallic,  584 
a-  (/3-)  Hydroxyglutaric,  335 
a-Hydroxyisobutyric,  326 
a-Hydroxyisovalcric,  326 
Hydroxymalonic,  334 
Hydroxymethylsulphonic,  213 
a-Hydroxymyristic,  326 
Hydroxyoleic,  326 
a-Hydroxypalmitic,  326 
/3-Hydroxypelargonic,  327 
p-Hydroxyphenylacetic,  583,  736 
a-Hydroxypropionic,  323 
/3-Hydroxypropionic,  325 
a-Hydroxystearic,  326 
Hydroxysuccinic,  335 
Hydroxytoluic,  577 
a-Hydroxyvaleric,  326 
Hypogseic,  291 
lehthyolsulphonic,  84 
Idonic,  328 

Iminodithiocarbamic,  365 
Iminodithiocarbonic,  365 
Iminothiocarbonic,  365 
Indoxylic,  638,  644 
/3-Iodopropionic,  318 
Isatic,  638 
Isatinic,  638 
Isethionic,  213 
Isoamylmalonic,  308 
Isoanthraflavinic,  616 
Lsobutylaticonic,  314 
Isobutylfumaric,  312 
Isobutylmaleic,  312 
Isobutylmalonic,  308 
Isobutyric,  288 
Isocinchomeronic,  626 
Isocinnamic,  580 
Isocrotonic,  21,  295 
Isocyanic,  359 
Isodurenecarboxylic,  577 
Isodurylic,  577 
Isoerucic,  300 
Isolinolenic,  304 
Isonicotinic,  625 
Iso-oleic,  299 
Isophthalic,  525,  581 
Isopropylacetylenecarboxylic,  300 
Isopropylfumaric,  312 
7-Isopropylitaconic,  312 
Isopropylmaleic,  312 
Isopropylmalonic,  308 


Acid,  Isopurpuric,  563 
Isosaccharinic,  328 
Isosuccinic,  311 
Isovaleric,  289 
Itaconic,  312,  313 
Itamalic,  335 
Jecorinic,  304 
/3-Ketobutyric,  332 
Lactic,  321,  323 
Lactobionic,  438 
Lanugic,  683 
Laurie,  265,  289,  302 
Leucinic,  326 
Levulinic,  326,  333,  431 
Lignic,  506 
Lignoceric,  265,  397 
Linolenic,  304 
Linolic,  303 
Lutidinic,  626 
Lyxonic,  328 
Malamic,  353 
Maleic,  21,  312,  313 
Malic,  335,  353 
Malonic,  3081  368 
Maltobionic,  438 
Mandelic,  577,  583 
d -Harmonic,  328,  436 
d.-Mannosaccharic,  436 
Margaric,  290,  415 
Meconic,  633 
Melissic,  290 
Mellitic,  535,  575,  581 
Mellophanic,  581 
Mesaconic,  21,  312,  314 
Mesitylenecarboxylic,  577 
Mesitylenic,  577 
Mesotartaric,  336 
Mesoxalic,  334,  344 
Metacrylic,  296 
Metasaccharinic,  328 
Methionic,  192,  213 
Methylacetylenecarboxylic,  300 
a-Methylacrylic,  296 
/3-Methylacrylic,  295 
0-Methyladipic,  311 
Methylbutylmalonic,  308 
l-Methylcyclohexylidenc-4-acetic,  19 
Methylenedisulphonic,  213 
7-Methylene-y-methylpyrotartaric,  312 
Methylenesuccinic,  313 
Methylethylglycollic,  326 
Methylethylitaconic,  312 
Methylethylmaleic,  312 
Methylethylmalonic,  308 
Methylfumaric,  314 
Methylisobutylmalonic,  308 
Methylisopropylmaleic,  312 
Methylisopropylmalonic,  308 
a-  (7-)  Methylitaconic,  312 
Methylmaleic,  314 
Methylmalonic,  308 
Methylmethyleneacetic,  296 
Methylpropiolic,  301 
Methylpropylmaleic,  312 
Methylpropylmalonic,  308 
Monochloroacetic,  317,  321 
Monothiocarbamic,  364 
Monothiocarbonic,  364 
Monothiocarbonylamic,  365 
Monothiocarbonylic,  365 
Mucic,  344,  437 
Muconic,  315 
Myristic,  289 
Myronic,  741 


746  INDEX 

Acid,  Naphthalic,  614 
Naphthionic,  613 
l-Naphthylamine-4-sulphonic,  613 
Nicotinic,  625 
m-Nitro benzole,  578 
o-Nitrocinnamic,  642 
Nitrohydroxylaminic,  206 
o-Nitrophenylacetic,  642 
o-Nitrophenylpropiolic,  642 
Nonoic,  289,  300 
Nonylacetylenecarboxylk',  300 
Nucleic,  739 
(Enanthic,  289 
Oleic,  298 
Aa/3-Oleic,  299 
Orsellinic,  577 
Oxalacetic,  344 
Oxalic,  306 
Oxaluric,  366 
Oxamic,  352 
Palmitic,  289 
Parabanic,  366 
Paralactic,  325 
Paratartaric,  336 
Pectic,  457 
Pectosinic,  457 
Pelargonic,  289 
Pentadecoic,  265 
Pentamethylbenzoic,  577 
Pentylmalonic,  308 
Perinaphthalenedicarboxylic,  612 
Perthiocyanic,  360 
(8-Phenanthrenecarboxylic,  619 
Phenylacetic,  575,  577,  579 
Phenylaminoacetic,  560 
a-Phenyl-o-nitrocinnamic,  618 
Phenylene-o-dicarboxylic,  580 
Phenylglycine-o-carboxylic,  643 
Phenylpropiolic,  535,  575,  577,  580 
Phenylsulphaminic,  560 
Phenylsulphuric,  542 
Phthalic,  580 
Picolinic,  625 
Picric,  245,  562,  655 
Pimaric,  596 
Pimelic,  305,  521 
Pinonic,  597 

Piperic  (piperinic),  584,  626 
Piperonylic,  583 
Pivalic,  289 

Prehnitinecarboxylic,  577 
Prehnitic,  581 
Prehnitylic,  577 
as.  Propanetricarboxylic,  345 
s.  Propanetricarboxylic,  315,  345 
Propargylic,  301 
Propinoic,  301 
Propiolic,  301 
Propionic,  288 

Propylacetylenecarboxylic,  300 
Propylfumaric,  312 
Propylitaconic,  312 
Propylmaleic,  312 
Propylmalonic,  308 
Propylsuccinic,  310 
Protalbinic,  641 
Protocatechuic,  577,  583 
Pseudouric,  368 
Purpuric,  367 
/3-Pyridinesulphonic,  625 
Pyrocinchonic,  312,  314 
Pyrogallic,  545 
Pyroligneous,  276 
Pyromeconic  .626 


Acid,  Pyromellitic,  581 
Pyromucic,  620 
Pyrotartaric,  311 
Pyroterebic,  297 
Pyrroglutamic,  622 
a-Pyrrolidinecarboxylic,  622,  739 
a'-Pyrrolidone-a-carboxylic,  622 
Pyruvic,  321,  331 
Quinic,  592,  636 
Quinolinecarboxylic,  636 
Quinoline-a  :  |3-dicarboxylic,  636 
Quinolinesulphonic,  636 
Quinolinic,  626 
Racemic,  20,  336 
Rhamnohexonic,    29 
Rhodanic,  360 
Rhodinic,  297 
Ribonic,  328 
Ricinelaidinic,  326 
Ricinoleic,  326 
Ricinoleinsulphonic,  3  7 
Roccellic,  305 
Rosolic,  608,  647,  660 
Rubeanhydric,  359 
Ruberythric,  617 
Rufigallic,  616 
.   Saccharic,  344 
d-Saccharic,  433 
Saccharinic,  328 
Salicylic,  179,  577,  582 
Santalic,  669 
Sarcolactic,  325 
Sativic,  304 
Sebacic,  298,  305 
Sinapic,  632 
Sorbic,  303 
Sozolic,  564 
Stearic,  290 
Stearolic,  302 
Suberic,  305,  521 
Succinamic,  353 
Succinic,  305,  310 
Sulphanilic,  538 
Sulpho-oleic,  407 
Talonic,  328 
Tannic,  584 
Tariric,  302 
Tartaric,  20,  335 
Tartronic,  185,  334 
Taurocholic,  214,  356,  741 
Telfairic,  304 
Teraconic,  312 
Teracrylic,  297 
Terebic,  297,  602 
Terebinic,  335,  597 
Terephthalic,  581,  597 
Terpenylic,  297 
Tetrabromostearic,  304 
Tetracetylenedicarboxylic,  315 
Tetrahydroxystearic,  304 
Tetrolic,  295,  301 
Thioacetic,  351 
Thiocyanic,  360 
Thiocyanuric,  360 
Tiglic,  296 
Toluic,  577 

Tricarballylic,  303,  315,  345 
Trichloroacetic,  318 
Trihydroxybenzoic,  583 
Trihydroxyglutaric,  343,  430 
Trihydroxyisobutyric,  428 
Trimellitic,  581 
Trimeeic,  329,  581 
Trimethylacetic,  289 


INDEX 


747 


Acid,  Trimethylenedicarboxylic,  520 

aa/3-Trimethyltricarballylic,  315 

Trithiocarbonic,  364,  365 

Tropic,  577,  631 

Umbellic,  584 

Undecoic,  289 

Undecolic,  302 

Uric,  368 

Valeric,  288 

Vanillic,  583 

Veratric,  583 

Vinylacetic,  294 

/3-Vinylacrylic,  303 

Violuric,  368 

Xanthic,  365 

Xanthonic,  365 

Xylic,  577 

Xylonic,  328,  430 
Acid-albumins,  733,  737 
Acidol,  355 
Acids,  Affinity  constants,  266 

Heat  of  neutralisation  of  organic,  2.~> 

Alkylsulphonic,  195 

Alkylsulphuric,  197 

Aminobenzoic,  578 

Anthracenecarboxylic,  616 

Anthracenesulphonic,  616 

Anthraquinonesulphonic,  616 

Aromatic,  575  et  seq. 

Azobenzoic,  578 

Benzenedicarboxylic,  575 

Benzenetetracarboxylic,  581 

Benzenetricarboxylic,  575 

Benzoylbenzoic,  607 

Diazobenzoic,  578 

Dibasic,  196 

Dihydroxybenzoic,  583 

Dihydroxycinnamic,  584 

Dihydroxystearic,  326 

Diolefinedicarboxylic,  315 

Diphenylcarboxylic,  606 

Diphenylsulphonic,  606 

Heptonic,  329 

Hexabromostearic,  304 

Hexahydroxystearic,  304 

Hexonic,  328,  427 

Homoaspartic,  356 

Hydrophthalic,  591 

Hydroxamic,  206,  358 

Hydroximic,  358 

Hydroxyolefinecarboxylic,  326 

Hydroxypyridinecarboxylic,  626 

a-Ketonic,  331 

j8-Ketonic,  330 

7-Ketonic,  331 

Ketonic  dibasic,  344 

Lactic,  19,  323 

Monobasic,  196 

Monobasic  aldehydic,  329 

Monobasic  ketonic,  330 

Naphthalenesulphonic,  613 

Naphthenic,  592 

Naphthoic,  614 

Naphtholsulphonic,  656 

Olefinecarboxylic,  291 

Olefinedicarboxylic,  312 

Phenolic,  576,  582 

Phenolsulphonic,  543,  564 

Phthalic,  575,  580 

Polybasic  aromatic,  580 

Polybasic  fatty,  304 

Pyridinecarboxylic,  625,  C2G 

Pyrotartaric,  311 

Quinolinebenzocarboxylic,  636 


Acids,  Quinolinecarboxylic,  636 
Saturated  dibasic,  304 
Saturated  monobasic  fatty,  264 
Succinic,  310 
Sulphobenzoic,  579 
Sulphonic,  538 

Tartaric,  18,  20,  335 

Tetrabasic,  316 

Toluic,  579 

Tribasic,  196,  315 

Unsaturated  dibasic,  312 

Unsaturated  monobasic  fatty,  291 

Unsaturated  monobasic,  of  the  series 
C«H2«-402,  300 

with  two  double  bonds,  302 

with  three  double  bonds,  304 

with  triple  linking,  300 

Xylic,  579 
Aconitine,  628 
Aconitum  napellus,  345 
Acridine,  647 
Acridines,  672 
Acrolein,  209 
Acroleinammonia,  209 
Acroleinaniline,  636 
'  Acrose,  329,  428 
Acrylic  aldehyde,  209 
Activators,.  410 
Adenine,  368,  369 
Adonitol,  431 
Adrenaline,  629 
Aesculetin,  584,  741 
Aesculin,.  584,  741 
Affinity  constants,  267 
Agglutinins,  115 
Agro  cotto,  347,  348 
Alanine,  325,  354 
Albumin,  Living,  114 
Albuminates,  737 
Albuminoids,  733,  739 
Albumins,  735 
Albumoses,  734,  737 
Alcohol,  Absolute,  109,  144 

Acetoisopropyl,  333 

Acetone,  333 

Allyl,  182 

Amyl,  105,  145,  181 

Anisic,  573 

Benzyl,  570 

Butyl,  104,  105,  180 

Caproyl,  181 

Capryl,  181 

Ceryl,  105,  181 

Cetyl,  181 

Coniferyl,  741 

Cumyl,  571 

Decyl,  105 

Denatured,  145,  149,  152 

Dodecyl,  105 

Ethyl,  108 

Fluorene,  572 

Furfuryl,  620 

Glycide,  214 

Heptyl,  105,  181 

Hexadecyl,  105,  181 

Hexyl,  181 

Hydroxy benzyl,  573 

Isobutyl,  105,  181 

Isohexyl,  181 

Isopropyl,  105,  181 

Melissyl,  181 

Methyl,  106-108,  142 

Monochloroethyl,  21 

Myricyl,  105,  181 


748 


INDEX 


Alcohol,  Nonyl,  105 

Octodecyl,  105 

Octyl,  105,  181 

Oenanthyl,  181 

of  crystallisation,  105 

Pentadecyl,  105 

Phthalic,  570 

Propargyl,  182 

Propyl,  105,  181 

Styryl,  571 

Tetradecyl,  105 

Tolylene,  571 

Tridecyl,  105 

Undecyl,  105 

Vanillic,  573 

Vinyl,  182 

Xylylene,  570 
Alcohol,  Amylo  process,  129 

Effront  process,  141 

Fiscal  regulations,  149 

from  fruit,  141 

from  lees,  143 

from  molasses,  140 

from  vinasse,  143 

from  wine,  143 

from  wood,  142 

Industrial  preparation,  116 

meters,  146 

Rectification,  138 

Solid,  109 

Statistics,  149 

Syntheses,  108 

Tests,  144,  146 

Windisch's  Table,  148 

Yield,  128 
Alcohols,  102 

Aldehydic,  329 

Aromatic  ketonic,  573 

Constitution,  103 

Derivatives  of  monohydric,  190 
of  polyhydric,  213 

Dihydric,  182 

Higher  monohydric,  180 

Ketonic,  330,  333 

Nomenclature,  104 

Polyhydric,  182,  188 

aldehydic,  or  ketonic,  426 

Primary,  103,  104 

Saturated  monohydric,  103,  105 

Secondary,  103,  104 

Tertiary,  103,  104 

Tetrahydric,  188 

Trihydric,  183 

Unsaturated,  182 
Alcoholene,  153 
Alcoholism,  150 
Alcoholometer,  Gay  Lussac,  146 

Tralles,  146 
Alcoholometry,  146 
Aldehyde -ammonias,  205 
Aldehydes,  96,  103,  204 

Aromatic,  570 

Determination  by  Strache's  method,  212 

Schiff's  reagent,  206 

with  unsaturatcd  radicals,  209 
Aldehydine,  624 
Aldehydo-catalase,  112 
Aldims,  574 
Aldine,  626 
Aldines,  572 
Aldohexoses,  427,  431 
Aldoketenes,  213 
Aldol,  329 
Aldols,  205 


Aldoses,  426 
Aldoximes,  206 
Alembics,  133 
Alga;,  60 

Alipine,  99,  629,  633 
Alizarin,  617,  654,  659 

astrol,  677 

cyanine,  663 

irisol,  677 

saphirol,  677 
Alkaloids,  626 

Synthesis,  627 

Table,  628 

Tests,  627 
Alkines,  625 
Alkoxides,  103 

Alkoxy-groups,  Estimation,  542 
Alkylanthrahydrides,  616 
Alkylenes,  87 
Alkylhydrazines,  202 
Alkylhydroanthranols,  616 
Alkylhydroxylamines,  202 
Alkyls,  29 
Alkyl  halides,  94,  95 

Estimation,  100 
Alkylisoureas,  364 
Allantoin,  367 
Allene,  90,  314 
Alloisomerism,  21,  22 
Alloxan,  366,  623 
Alloxantin,  367 
Allyl  bromide,  102 

chloride,  102 

iodide,  102 

isothiocyanate,  361 

mustard  oil,  361 

thiocyanate,  361 
Allylaniline,  636 
Allylene,  90,  314 

Almonds,  composition  of  sweet,  391 
Aloin,  741 
Amaranth,  656 
Amidases,  155 
Amides,  211,  351 

of  carbonic  acid,  363 

of  hydroxy-acids,  353 
Amidines,  199,  357 
Amido-chlorides,  356 
Amidol,  564 
Amidoximes,  358 
Amimides,  357 
Amines,  200 

Aromatic,  555 
Amino-acids,  351 

Derivatives,  354 
Aminoanisoles,  564 
Aminazobenzene,  569 
Aminoazobenzenes,  565 
Aminoazo-derivatives,  568 
Aminobenzene,  557 
Amino-derivatives  of  aromatic  hydrocarbons, 

554 

Aminoguanidine,  366 
Amino-oxindole.  642 
Aminophenols,  562,  563 
Aminothiazole,  623 
Aminothiophenols,  564 
Ammelide,  362 
Ammc  line,  362 
Ammonium  carbamate,  363 

cyanate,  359 

ichthyolsulphonate,  84 

thiocyanate,  361 
Amygdalin,  113,  740 


INDEX 


749 


Amyl  acetate,  371 
Amylacetylene,  334 
Amylase,  111,  112 
Amylbenzene,  527 
Amylene,  9J 

hydrate,  181 
Amylodextrin,  116 
Amyloids,  504 

Amylomyces  Rouxii,  130,  131 
Amylo  process,  129 
Anaesthesia,  94,  98,  029 
Anaesthesin,  633 
Anaesthesiophore,  633 
Anaesthetics,  98,  629 

Mild  local,  633 
Analgen,  637 
Analysis,  Elementary,  7 
Qualitative,  6 
Quantitative,  7 
Anethole,  543,  574 
Anhydrides,  319,  320 
Internal,  319 
Mixed,  319 
Anhydro-bases,  557 
Anilides,  560 
Aniline,  557,  566 

hydrochloride,  559,  567 
nitrate,  567 
platinichloride,  559 
salt,  559 
sulphate,  559 

Anisaldehyde,  574 

Anisidines,  564 

Anisole,  542 

Annatto,  388 

Anterea  mylitta,  696 

Anthracene,  615 

derivatives,  616 

Anthrachrysone,  616 

Anthraflavone,  665 

Anthragallol,  616 

Anthrahydroquinones,  616 

Anthramine,  616 

Anthranil,  578 

Anthranol,  616,  617 

Anthrapurpurine,  616 

Anthraquinones,  616,  647 

Anthrarufin,  616 

Anthrols,  616 

Anthrone,  616 

Antialdoximes,  210 

Anti-bodies,  115 

Antichlor,  706 

Antidiazo-p-chlorbenzene,  566 

Antidiazotates,  567 

Antifebrin,  560 

Antiketoximes,  211 

Antilactase,  115 

Antimorphine,  115 

Antipepsin,  115 

Antipyrine,  623 

Antique  purple,  664 

Antirennet,  115 

Antiricin,  115 

Antiseptics,  127,  541 

Antiserum,  738 

Antitoxins,  115 

Apigenin,  638 

Araban,  429 

Arabinose,  428,  429,  431 

benzylphenylhydrazone,  429 

Arabitol,  189,  427,  430 

Arachis  nuts,  391 
Arbutin,  741 


Archil,  544,  667 

Arginine,  328 

Aristol,  543 

Aromatic  compounds,  28,  521 

Arrack,  160 

Artificial  hair,  702 

Artificial  parthenogenesis,  115 

Ascomycetes,  111 

Aseptol,  564 

Asparagine,  19,  358 

Aspartamide,  356 

Aspergillus  oryzse,  130 

Asphalte,  59,  83 

mastic,  83 
Aspirin,  582 
Astatki,  67,  74 
Asymmetric  syntheses,  114 
Asymmetry,  Absolute,  22 

Relative,  22 
Atole,  160 

Atropa  belladonna,  631 
Atropine,  628,  631 
Attenuation  of  fermented  liquids,  12  \  13 

174 

Auramine,  660 
Aurin,  608,  660 
Auxochromes,  649 
Axite,  245 
Azides,  358 
Aziminobenzene,  557 
Azimino-compounds,  557 
Azines,  661 
Azobenzene,  565 
Azo  carmine,  Acid,  676 
Azo-derivatives,  565 
Azodicarbonamide,  366 
Azoflavine,  675 
Azofuchsines,  657 
Azolitmin,  668 
Azorubin  S,  656 
Azotoluene,  565 
Azoxazole,  623 
Azoxybenzene,  565 

BACILLUS  aceticus,  122,  280 

acidi  laevolactici,  325 

acidificans  longissimus,  128 

butylicus,  181 

Delbriickii,  126 

ethaceticus,  328 

saprogenes  vini,  339 
Bacteria,  Acetic,  122,  280 

Butyric,  122 

Chromogenic,  110 

Lactic,  122 

Pathogenic,  110 

Reproduction,  110 

Saprophytic,  110 

Zymogenic,  110 
Bagasse,  444 
Balling's  Table,  167 
Ballistite,  244 
Baphia  nitida,  669 
Barley,  161 
Barwood,  669 
Bases,  Aldehydo-,  557 

Aminic,  200 

Ammonium,  200 

Arsonium,  202 

Iminic,  200 

Nitrilic,  200 

Primary,  200 

Quaternary,  200,  556 

Secondary,  200 


750  INDEX 

Bases,  Tertiary,  200 
Vegetable,  626 

Beckmann  rearrangement,  211,  573 
Beer,  161 

Alcohol-free,  178 
Analysis,  178 
Attenuation,  178 
Cask  pitching,  176 
Composition,  178 
Detection  of  antiseptics,  179 
Fermentation,  171 
Mashing,  168 
Pasteurisation,  177 
Racking,  176 
Statistics,  179 
Beet,  445 

Cultivation,  446 
Production,  478 
Sugar-content,  446 
Treatment,  448 
Beet -pulp  press,  453 
Benzal  chloride,  538 
Benzalacetone,  572 
Benzalacetophenone,  572 
Benzalazine,  573 
Benzaldehyde,  571,  595 
homologues,  571 
phenylhydrazone,  573 
Benzaldoxime,  572 
Benzamide,  578 
Benzanilide,  560 
Benzanthrone,  665 
Benzene,  528,  533 
Artificial,  533 
Chloro -derivatives,  537 
Derivatives,  521 
Formation,  525 
Formulae,  522 
from  Naphtha,  75 
Haloid  derivatives,  537 
Homologues,  534 
Hydrogenated  derivatives,  591 
Isomeric  derivatives,  523 
Tests,  534 

Benzene  sulphochloride,  538 
Benzenesulphamides,  538 
Benzhydrazide,  578 
Benzhydrol,  572,  606 

Tetramethyldiamino-derivative,  606 
Benzidam,  557 
Benzidine,  566,  605,  650,  657 
Benzil,  609 
Benziminazoles,  557 
Benzine,  Crude,  73 

from  petroleum,  66 
Benzoazurin,  605,  660,  678 
blue,  678 
blue-black,  678 
browns,  679 
flavin,  663 
orange,  678 
purpurin,  605 
Benzoin,  609 
Benzonitrile,  568 
Benzophenone,  572,  606 

oxime,  673 
Benzopinacone,  572 
Benzoquinone,  547 
Benzotrichloride,  538 
Benzoyl,  14 

chloride,  578 
Benzoylacetone,  572 
Benzoylazoimide,  578 
Benzoylcarbinol,  574 


Benzoylsalicin,  741 
Benzoyltropine,  629 
Benzyl  bromide,  537 
chloride,  537,  553 
iodide,  537 
Benzylamine,  561 
Benzylaniline,  560 
Benzyldioximes,  609 
Benzylglucoside,  437 
Benzylhydrazine,  570 
Benzylphenylamine,  560 
Benzylphenylhydrazine,  570 
Berberine,  633 
Bergamot,  347 
Betaine,  323,  355 

hydrochloride,  355 
Betol,  613 

Bile  compounds,  741 
Bilifuchsin,  741 
Bilineurine,  214 
Bilirubin,  741 
Biliverdin,  741 
Biogen  theory,  114 
Bisazo -compounds,  565 
Bismuth  tribromophenoxide,  101 
Bisulphite  aldehyde  compounds,  205 
Bitumen,  83 
Biuret,  364 
Bixa  orellana,  388 
Black,  Acid  azo,  674 
Alizarin,  663 ' 
Aniline,  651,  662,  731 
Anthracene,  674 
Bone,  470 
Columbia,  677 
Diamine,  677 
Diamond,  657 
Fine,  663 
Immedial,  677 
Naphthazarin,  614 
Naphthol,  657 
Naphthylamine,  657 
Oxidation,  663 
Pluto,  677 
Sulphur,  671 
Vidal,  564,  677 
Zambesi,  677 
Blankite,  445 
Blastomycetes,  111 
Bleaching  of  textiles,  712 
Blood,  114 

stains,  Identification,  738 
Blue,  Algol,  665 
Alizarin,  663 
Alkali,  676 
Anthracene,  663 
Capri,  661 
Carmine,  660 
Ciba,  664 
Diaminogen,  678 
Immedial,  678 
Indanthrene,  665 
Indrone,  665 
Janos,  677 
Lanacyl,  677 
Meldola's,  673 
Methylene,  661,  673 
Naphthol,  661 
Nile,  661 
Oxamine,  678 
Sulphur,  678 
Victoria,  677 
Wool,  677 
Boghead  coal,  84 


INDEX 


751 


Bombyx  mori,  690 
Boot-polish,  475,  528 
Bordeaux,  Ciba,  664 

Indanthrene,  665 

S,  656 

Borneo!,  600,  602 
Bornesitol,  546 
Boudineuse,  231.  24.S 
Bradolytes,  608 
Brandy,  see.  Cognac 
Brazilein,  669 
Brazilin,  669 
British  gum,  501 
Bromobenzenes,  537 
4-Bromomethylfurfural,  430 
Bromonitrobenzenes,  553 
Bromostyrenes,  538 
Bronze,  Diamine,  679 
Brown,  Alizarin,  677 

Anthracene,  677 

Bismarck,  557,  658.  672.  677 

Cibanone,  665 

Diamine,  679 

Indanthrene,  665 

.lanos,  679 

Pluto,  679 

Pyrogen,  679 

Sulphur,  679 

Thiazine,  679 
Brucine,  628,  633   . 
Bulgarian  ferment,  440 
Butandiene,  90 
Butandiine,  94 
Butandione,  333 
Butanes,  91 
Butanolone,  333 
Butanols,  180 
Butanone,  212 
Butantetrol,  189 
Butenes,  80 
Butter,  385 

Analysis,  387 

Artificial,  387 

Cacao,  369 

Coco -nut,  402 

Renovated,  388 
Buttirol,  385 
Butyl  iodides,  97 
Butylbenzene,  527 
Butylenes,  80 
Butyroflavine,  383 
Butyrolactone,  322 
Butyrometer,  Gerber,  386 
Butyrorefractometer,  Zeiss,  375 
Butyryl  chlorides,  319 
Byssus,  698 

CACAO  butter,  369 
Cachou  de  Laval,  670 

Immedial,  679 

Sulphur,  (>79 
Cacodyl,  20,  202 

chloride,  202 

oxide,  202 
Cadaverine,  214 
Cadmium  bromoxylonate,  429 
Caffeine,  368,  369,  626 
Calcium  acetate,  285 

benzoate,  526 

butyrate,  288 

carbide,  92 

citrate,  346,  350 

cyanamidc,  362 

dilactate,  325 


Calcium  formate,  270 

lactate,  325 

oxalate,  307 

tartrate,  336 
Calendars,  725 

Calorimeter,  Junker's  gas,  54 
Campeachy,  666 
Camphane,  598 
Camphene,  597 
Campholide,  603 
Camphor,  600,  602 

Artificial,  597,  603 
Camphors,  600 
Camwood,  669 
Candles,  412 

Paraffin,  415 

Statistics,  415 

Stearine,  414 

Tallow,  413 
Cannel  coal,  84 
Cantharidin,  742 
Capillarimeter,  149 
Caps,  255 
Caramel,  433,  435 
Carane,  596 
Carbamide,  363 
Carbamidyl  chloride,  363 
Carbazide,  364 
Carbazole,  605,  615 
Carbenes,  83 
Carbinol,  104,  108 
Carbocyclic  compounds,  28 
Carbodiimide,  18,  362 
Carbodiphenylimide,  362 
Carbodynamite,  231 
Carbohydrates,  426 
Carbohydrazide,  364 
Carbolineum,  532 
Carbon,  Asymmetric,  18,  27 

chains,  16 

Estimation,  7 

sulphochloride,  365 

tetrachloride,  101 

Valency,  14 

Carbon  oxychloride,  see  Phosgene 
Carbonisation  of  textiles,  682,  714 
Carbonite,  231 
Carbonites,  246 
Carbostyril,  637 
Carboxyhsemoglobin,  738 
Carboxyl,  103 
Carbyl  sulphate,  213 
Carbylamines,  199,  556 
Carone,  596,  600 
Carotin,  692 
Cart-grease,  82,  424 
Carvacrol,  543,  600 
Carvacrylamine,  555 
Carvene,  593,  595 
Carvol,  601 
Carvomenthol,  600 
Carvomenthone,  600 
Carvone,  601 
Caryophyllene,  598 
Casein,  385,  702,  737 

Vegetable,  737 
Castor  oil,  326,  393 
Catalases,  112 
Catalysts,  Inorganic,  113 

Organic,  113 
Catechol,  543 
Catechu,  585,  669 
Cedrene,  598 
Cellase,  112 


752 

Cellite  films,  504 
Cellobiose,  504 
Cellose,  504 
Celluloid,  604,  611 
Cellulose,  503 

acetate   504 

formate,  504 

hydrate,  505 

Wood,  511 

Centrifuges,  385,  468 
Cerasin,  61,  81,  85,  86,  597 
Cereals,  Starch-content,  117,  118 
Cerebrin,  741 
Cerotene,  90 
Cerotin,  181 
Ceryl  cerotate,  181,  372 
Cevadine,  632 
Cetyl  palmitate,  372 
Cetylbenzene,  527 
Chalkone,  572 
Chamberland  flasks,  123 
Chamoising,  588 
Champy  drums,  253 
Chappe  (silk),  692 
Charcoal,  Animal,  470 

Wood,  106 
Chartreuse,  160 
Cheddite,  255 
Cheese,  385 

Filled,  385 

Margarine,  382 
Chica,  160 
Chinovose,  431 
Chitin,  742     - 
Chitosan,  742 

Chlamydomucor  oryzae,  130 
Chloracetanilide,  560 
Chloral,  209 

hydrate,  209 
Chloralamide,  352 
Chloramides,  199 
Chloranhydrides,  317 
Chloranil,  547 
Chlorhydrins,  87,  214 
Chlorobenzenes,  537 
Chlorocruorin,  114 
Chloroethane,  97 
Chloroform,  98 

Pictet,  99 

Tests,  100 
Chloromethane,  96 
Chloronitrobenzenes,  553 
Chlorophyll,  111,  669 
Chlorophyllase,  669 
Chloropicrin,  198 
et-Chloropropylene,  102 
Chocolate,  368 
Cholesterol,  742 
Cholestrophane,  367 
Choline,  214 
Chromogens,  647 
Chromone,  637 

Chromophores,  595,  647  ft  seq. 
Chromotrop,  676 
Chronograph,  le  Boulenge's,  262 
Chrysamine  R,  678 
Chrysazin,  616 
Chrysazol,  616 
Chrysene,  619 
Chrysin,  638 
Chrysoidin,  557 
Chrysoidines,  565 
Chrysoin,  656 
Chrysophenin,  678 


INDEX 


Cider,  159 

Cinchona  alkaloids,  633 
Cinchonidine,  634 
Cinchonine,  628,  634 
Cinene,  594 
Cineol,  602 
Cinnamaldehyde,  572 
Citral,  182,  209 
Citrene,  593,  595 
Citromyces  citricus,  346 

Pfefferianus  and  Glaber,  34  '. 
Citronellal,  210,  297 
Citronellol,  182 
Citrus  bergamica,  347 

industry,  347 

limetta,  347 

limonium,  347 

Classification  of  organic  substances,  28 
Clovene,  598 
Clupein,  737 

Coagulation,  Enzymic,  112 
Coal,  Cannel,  84 

for  gas,  36,  37 
Coal-gas,  36 
Coal-tar,  83 
Cocaine,  99,  633 
Cocci,  110 
Coccus  cacti,  668 
Cochineal,  668 
Cocoa,  368 
Coco-nut,  Composition.  391 

oil  (or  butter),  378,  402 
Cocoons,  690 

Production,  695 

Waste,  692 
Codamine,  632 
Codeine,  627,  628,  632 
Ccerulein,  650,  651 
Ccerulignone,  606 
Coffee,  369 
Cognac,  144,  160 
Colchicine-,  628 
Collagens,  739 
Collidines,  625 
Collodion,  700 

cotton,  232,  239,  700 
Colophene,  598 
Colophony,  420,  596 
Colorimeters,  705 
Colouring-matters,  646 

Aci-aminoanthraquinone,  665 

Acid,  650,  655,  673 

Acridine,  663 

Adjective,  651 

Aminoazo,  656 

Azo,  655,  673 

Basic,  650,  655,  673 

Benzidine,  657 

Benzo,  657 

Chromotrop,  657 

Classification  of,  654 

Coumarin,  663 

Diamine,  657 

Dianil,  657 

Diphenylmethane,  660 

Fastness  of,  707 

Flavone,  663 

Hydrazone,  658 

Hydroxyazo,  656 

Immedial,  670 

Indanthrene,  664,  665 

Ingrain,  658 

Insoluble,  655 

Jan  os,  658 


INDEX 


753 


Colouring-matters,  Kathigenic,  670 

Kriogenic,  670 

Manufacture  of,  652 

Monoazo,  656 

Mordant,  655,  659 

Natural,  651 

Neutral,  650 

Nitro,  655 

Oxyketone,  663 

Phenolic,  673 

Polyazo,  656 

Pyrazolone,  658 

Quinoline,  663 

Quinonimide,  661,  665 

Quinone,  659 

Statistics,  653 

Substantive,  650,  651,  655,  673 

Sulphur,  670 

Tests,  671,  680 

Theory  of,  646,  708 

Thiazole,  663 

Triphenylmethane,  660 

Vat,  664 

Water-soluble,  671 

Xanthone,  663 

Concentrators,  Multiple  effect,  463,  464 
Condensation,  Aldehyde,  205 

Aldol,  205 

Condenser,  Liebig's,  2 
Conditioning  of  textiles,  704 
Conductivity,  Electrical,  27 
Conidia,  111 
Coniferin,  574,  741 
Coniine,  19,  90,  625,  629 
Conylene,  90 
Coolers,  Wort,  170 
Copellidine,  626 
Copper  aceto-arsenite,  287 
Copra,  402 
Cops,  718 
Coralline,  660 
Corchorus  capsularis,  689 
Cordite,  244 
Corium,  586 
Cornein,  740 
Cotarnine,  633 
Cotton,  684 

Bleaching,  711 

Mercerisation,  506,  685 

Production,  685 

seed,  391 
Coumalin,  626 
Coumarin,  576,  583,  595 
Coumarins,  663 
Count  of  yarn,  683 
Crabbing,  717 
Cracking  of  oils,  74 
Cream  of  tartar,  336,  337 
Creatine,  366 
Creatinine,  366 
Creoline,  543 
Creosol,  544 
Creosote,  83 

oils,  531 
Cresols,  543 
Croceine,  656 
Crotonaldehyde,  209 
Crotonylene,  90 
Crushers,  220,  261 
Cryptopine,  632 
Crystalline,  557 
Crystallisation,  2 
Crystallose,  579 
Crystals,  Hemihedral,  18 
II 


Crystals,  Liquid,  116 

Mixed,  23 
Cudbear,  668 
Cumene,  535 
Cumidine,  535 
Cuminaldehyde,  572 
Cuminol,  572 
Cunerol,  385 
Curagao,  160 
Curarine,  627,  633 
Cutch,  585,  669 
Cyamelide,  359 
Cyanamide,  18,  362 
Cyanamines,  661 
Cyanates,  359 
Cyanides,  Alkyl,  198 
Cyano-acids,  317 
Cyanogen,  358 

chloride,  359 

compounds,  358 
of  coal-gas,  47 

sulphide,  360 

trichloride,  359 
Cyanohydrins,  199 
Cyanole,  676 
Cyanoquinolines,  636 
Cyanurtriamide,  362 
Cyclic  compounds,  87,  520 
Cycloheptanone,  297 
Cyclohexane,  63 
Cyclo-olefines,  28,  520 
Cycloparaffins,  28,  520 
Cyclopentadiene,  521 
Cyclopentane,  63 
Cyclopentanone,  521 
Cyclopropane,  87 
Cymene,  209,  535 
Cymogen,  35 
Cynarase,  115 
Cysteine,  332,  356 
Cystine,  332,  356 
Cytase,  112 

DAMBONITOL,  546 
Daphnetin,  584,  741 
Daphnin,  584 
Datura  stramonium,  631 
Decahydroquinoline,  637 
Decane,  31 
Degragene,  389 
Degras,  389,  588 

Artificial,  389 
Degree  of  dissociation,  267 

fermentation,  129 
(apparent),  129 
(real),  129 

mercerisation,  686 

rancidity,  375 

viscosity,  79 
Degrees  Brix,  129,  481 
Dehusker,  121 
Delphinin,  627 
Denaturants,  152 
Denatured  alcohol,  152 
Densimeter,  Brix,  447,  481 

Legal,  174 

Dephlegmators,  67,  133,  139 
Derricks,  58,  65 
Desiohthyol,  84 
Desmo  bacteria,  110 
Desmotropy,  17 
Desoxybenzoin,  609 
Detonation,  215 
Detonators,  265 


754 

Developers,  Photographic,  564 
Dextrase,  123 
Dextrin,  501 

in  glucose,  433 
Dextrinase,  112,  171 
Dextrose,  433 
Diacetamide,  352 
Diacetanilide,  560 
Diacethydrazide,  358 
Diacetyl,  332,  333 
Diacetylene,  94 
Diacetylglycol,  182 
Dialdehydes,  329 
Diallyl,  90 
Diamalt,  500,  711 
Diamines,  Aromatic,  556 
Diamino-acids,  356 
Diaminoazobenzenes,  565 
Diaminobenzenes,  556 
p  :  p-Diaminodiphenyl,  605 
p-Diaminodiphenylmethane,  606 
Diaminogen,  678 
Diaminophenol,  564 
p-Diaminostilbene,  609 
Dianisidine,  605 

Dianthraquinonedihydroazine,  665 
Diastase,  111,  112,  116 
Diastofor,  500,  695,  711 
m-Diazine,  626 
Diazoaminobenzene,  569 
Diazoamino-«ompounds,  556,  565,  569 
Diazoanisole  cyanide,  567 
Diazobenzene  bromide,  568 
chloride,  568 
nitrate,  568 
perbromide,  568 
sulphate,  568 
Diazo  black,  677 
blue,  678 
brown,  679 
compounds,  202,  556,  565,  566 

Diazoguanidine,  366 

Diazomethane,  202 

Diazonium  platinichloride,  567 
salts,  566 

Diazotisation,  658 

Dibenzyl,  609 

derivatives,  609 

Dibromopyranthrene,  665 

Dicetyl,  31 

Dichlorhydrin,  214 

Dichlorethane,  98 

Dichloromethane,  98 

Dichloronaphthalene,  614 

Dickol,  400 

Dicrucin,  372 

Dicyanodiamide,  362 

Dieline,  102 

Diethylacetylurea,  629 

Diethylamine,  201 

Diethylcarbinol,  105,  203 

Diethylcyanamide,  362 

Diethylenediamine,  214 

Diethylmalonylurea,  629 

Diethylsulphone,  196 

Diffusors,  451,  452 

Digits  lin,  628,  741 

Digi^onin,  741,  742 

Digitoxin,  741 

Diglycerol,  184 

Diglycollamides,  353 

Diglycollimide,  353 

Dihydrazides,  358 

Dihydric  phenols,  543 


INDEX 


Dihydroanthracene,  616 
Dihydrocymene,  593,  596 
Dihydropyridines,  626 
Dihydropyrrole,  62 
Dihydroxyacetonase,  123 
Dihydroxyacetone,  123,  333 
Dihydroxyanthraquinone,  617 
o-Dihydroxybenzophenone,  606 
Dihydroxycoumarin,  584,  741 
Dihydroxydiaminoarsenobenzene,  564 
Dihydroxydiethylamine,  213 
Dihydroxydiphen3'ls,  606 
p-Dihydroxyhexamethylene,  592 
Dihydroxynaphthaquinone,  659 
Dihydroxytoluene,  544 
Diketobutane,  333 
p-Diketohexamethylene,  592 
Diketohexane,  334 
Diketonamines,  210 
Diketones,  333 
Diketopiperazine,  734 
Dimethylacetamide,  351 
Dimethylacetol,  333 
Dimethylamine,  201 
Dimethylaniline,  559 
Dimethylanthracene,  616 
Dimethylarsenic  acid,  202 

chloride,  202 
Dimethylarsine,  202 
Dimethylbenzenes,  534 
Dimethylbutadiene,  599 
Dimethylcarbinol,  180 
Dimethylethylcarbinol,  105,  181 
Dimethylfulvene,  521 
Dimethylmethane,  35 
Dimethyloxamide,  200 
Dimethylphenylpyrazolone,  623 
Dimethylpyridines,  625 
Dimethylthiophene,  620 
Dimorphism,  24 
Dinaphthol,  613 
Dinaphthyl,  614 
Dinitroacetylglycerine,  223 
Dinitroanthracenes,  616 
Dinitrobenzenes,  550 

Dinitrodurene,  548 

Dinitroformylglycerine,  223 

Dinitroglycerine,  222 

Dinitroisodurene,  548 

Dinitromesitylene,  548 

Dinitromonochlorhydrin,  223 

Dinitroprehnitene,  548 

7-Dinitrotolylphenylamine,  553 

/3-Dinitrotoluidine,  553 

Dinitroxylenes,  548 

Diolefines,  90 

Dionine,  627 

Dioxyindole,  638 

Dioxynaphthaquinones,  614 

Dipentene  dihydrochloricles,  595 

Dipeptides,  734 

Diphenyl,  568,  605 
derivatives,  605 

Diphenylacetamide,  560 

Diphenylacetylene,  609 

Diphenylamine,  559 

Diphenylcarbinol,  606 

Diphenyleneketone,  573 

Diphenylenemethane,  607 

as.  Diphenylethane,  606,  609 

Diphenylethylene,  609 

Diphenylhydrazine,  570 

Diphenyl  ketone,  572 

Diphenylmethane,  604 


INDEX 


755 


Diphenylnitrosamine,  570 
Diplococci,  110 
Dipropargyl,  94 
Dipsacus  fullonum,  725 
Dipyridine,  625 
7-Dipyridyl,  625 
Diquinoline,  637 
Diquinolyl,  637 
Disinfectants,  541 
Distillation,  Fractional,  2,  66 

of  fermented  liquids,  132 

Theory,  3 

Vacuum,  4 

Wood,  272 

Distillery  residues,  Utilisation,  153 
Disulphides,  195 
Disulphoxides,  195 
Dithioglycol  chloride,  213 
Dithiourethane,  365 
Diureides,  367 
Docosane,  31 
Dodecane,  31 
Dormiol,  99,  629 
Dotriacontane,  31 
Dryers  for  oils,  400 
Drying  ovens  for  explosives,  239,  253 

textiles,  723 

Drying  power  of  oils,  399 
Dulcitol,  190 
Durene,  535 
Durra,  117,  151,  154 
Dyeing,  Theory,  708 
Dyestuffs,  see  Colouring-matters 
Dyewoods,  666 
Dynamites,  229 

Analysis,  259 

Gelatine,  241 

Gelatinised,  242 

Gum,  241 

Manufacture,  230 

Non-congealing,  551 

Properties,  231 

Safety,  231 

with  active  bases,  231 

with  inert  bases,  230 

EBONITE,  598,  702 
Ebullioscope,  147 
Ecgonine,  633 
Echinochrom,  114 
Ecrasite,  563 

Effusiometer,  Bunsen's,  55 
Eggs,  736 

Preservation,  736 
Ehrlich's  side-chain  theory,  114 
Eicosane,  31 
Eikonogen,  613 
Elastin,  739 
Emeraldine,  662 
Emulsin,  112,  113 
Emulsor,  Kuhlmann,  226 
Emulsor-centrifuge,  394 
Enantiomorphism,  19,  24 
Enantiotropy,  108 
Encaustic,  377 
Engenhos,  444 
Enzymes,  22,  112,  740 

Equilibrated  action,  113 

Glycolytic,  429 

Synthetic  action,  113 
Eosin,  581 
Eosins,  661 
Epichlorhydrin,  214 
Equilibrium  in  saponification,  370 


Erica  B,  679 
Eriocyanine,  677 
Erythrene,  90 
Erythrin,  189 
Erythritol,  90,  189 
Erythrodextrin,  116 
Erythrolein,  668 
Erythrolitmin,  668 
Erythroxylon  coca,  633 
Ester ificat ion,  Laws,  370 
Esters,  103 
Ethanal,  208 
Ethanamide,  352 
Ethanamidine,  357 
Ethandial,  329 
Ethandiol,  183 
Ethane,  17,  23,  34 

Polychloro-derivatives,  101 
Ethanol,  108 
Ethene,  29,  89 
Ethenol,  182 

Ethenylethylenediamine,  623 
Ether,  192 

Petroleum,  35,  66 
Ethers,  190 
Ethine,  29,  92 
Ethyl,  29 

acetate,  331,  371 

acetoacetate,  331,  332,  372 

benzoate,  578 

bromide,  95 

bromopropionate,  309 

butyrate,  372 

carbonate,  363 

chloride,  95,  97 

chloroacetoacetate,  333 

chlorocarbonate,  363 

chloroformate,  363 

cyanurate,  359 

diacetylsuccinate,  333 

diazoacetate,  323,  356 

dichloroacetoacetate,  333 

dihydrocollidinedicarboxylate,  624 

diketoapocamphorate,  602 

diketocamphorate,  602 

/3  /3-dimethylglutarate,  602 

dimethylmalonate,  372 

fluoride,  95,  97 

formate,  331,  371 

hydroxycrotonate,  330 

iodide,  95,  97 

isocyanate,  359 

isocyanurate,  359 

malonate,  308 

methyl  ketone,  212 

mustard  oil,  361 

nitrate,  197 

nitrite,  197 

oxalate,  200 

peroxide,  194 
hydrate,  194 

phosphate,  197 

sodioacetoacetate,  331,  332 

sodiomalonate,  309 

sodiomethylmalonate,  309 

sulphate,  197 

sulphite,  197 

thioacetate,  351 

thiocyanate,  361 
Ethylacetamide,  351 
Ethylacetamido-chloride,  356 
Ethylacetimino-chloride,  356 
Ethylacetylene,  90 
Ethylamine,  199,  201 


756 

Ethylamine  ethyldithiocarbamate,  365 

hydrochloride,  351 
Ethylbenzene,  527,  534 
Ethylcarbinol,  180 
Ethylcyanamide,  362 
Ethylene,  87,  89 

bromide,  98,  182 

chloride,  98 

cyanide,  213 

iodide,  98 

monothiohydrate,  213 

oxide,  213 

Polychloro -derivatives,  102 
Ethylenecyanohydrin,  213 
Ethylenediamine,  213 
Ethylenic  compounds,  98 
Ethylglycocoll,  734 
Ethylhydrazine,  206 
Ethylideneacetone,  333 
Ethylidene  chloride,  98 
Ethylidenecyanohydrin,  199,  213,  221 
Ethylidenic  compounds,  98 
Ethylmagnesium  bromide,  203 
Ethylmercaptan,  196 
Ethylsulphone,  196 
Ethyltoluene,  525 
Ethylurethane,  363 
Etiline,  102 
Eucaine,  99,  627 
Eugenol,  544 
Euquinine,  627 
Eurodines,  661 
Euxanthine,  668 
Euxanthone,  668 
Exalgin,  560 
Excelsior  mill,  168,  250 
Exhausters,  48 
Exploders,  258 
Explosion,  215 

by  influence,  221 

Determination  of,  220 

Heat  of,  216 

Pressure  of  gases,  218 

Velocity  of  combustion,  219 
projectiles,  262 
reaction,  219 

wave,  219 

Volume  of  gases,  217 
Explosive,  Favier's,  220 
Explasives,  Abel's  test  for,  260 

Analysis  of,  259 

Charging  density  of,  218 

Classification  of,  222 

Destruction  of  waste,  258 

Non-congealing,  223 

Progressive,  219 

Safety,  33,  246 

Sensitiveness  of,  261 

Shattering,  219 

Sprengel's,  245 

Stabilisation  of,  228 
"  Statistics  of,  263 

Storage  of,  258 

Theory  of,  215 

Uses  of,  263 
Extractor,  Merz  universal,  393 

Pallenberg,  393 

Soxhlet,  374 

Wegelin  and  Hubner,  393 

FACTIS,  599 

Fat,  Bone,  378,  388 

Crude,  390 

Goose,  378 


INDEX 


Fat,  Hog's,  388 

Horse,  378 

Ox,  378 

Wool,  389 
Fats,  372 

Acid  number  of,  375 

Animal,  379 

Chemical  and  physical  constants  of,  378 

Dropping-point  of,  6,  375 

Estimation  of,  374 

Industrial  treatment  of,  405  et  seq. 

Rancidity  of,  375 

Saponification  of,  377 
Fehling's  solution,  212,  486 
Felt,  681 
Fenchene,  598 
Fenchone,  602 
Fermentation,  Alcoholic,  110,  121,  171 

Lactic,  324 
Ferrugine,  694 
Fibres,  see  Textile  fibres 
Fibrinogen,  114,  737 
Fibroin,  692,  740 
Filite,  244 

Films  for  cinematographs,  504 
Filter-presses,  459 
Filters,  Charcoal,  470 

Mechanical,  461 
Firedamp,  33,  246 
Fishery  statistics,  60 
Flavanthrene,  665 
Flavin,  638,  668 
Flavol,  616 
Flavone,  637,  663 
Flavopurpurin,  616,  663 
Flax,  687 

Autumn,  687 

March,  687 
Fleece,  681 
Floricin,  399 
Floss  (silk),  691 
Flour,  Wheat,  497 
Fluoranthrene,  619 
Fluorene,  607 
Fluorescein,  581,  660 
Fodder,  Molassic,  140 

Nutritive  value  of,  153 
Forcite,  242 
Forests,  519 
Formaldehyde,  206 
Formalin  (Formol),  Analysis  of,  207 
Formamide,  352 
Formates,  270 
Formhydrazide,  358 
Formins,  214 
Formose,  428 
Formula,  Constitutional,  14 

Empirical,  12 

Fleischmann's,  386 

Structural,  14 
Formulae,  Rational,  17 

Unitary,  14 
Formyl  chloride,  317 
Formyloxime  chloride,  358 
Fractionator,  136 
Fructose,  435 

Specific  Rotation  of,  485 
Fruit  essences,  Artificial,  289,  371 
Fuchsine,  608,  660 
Fucose,  431 
Fulgurite,  231,  245 
Fuller's-earth,  77,  395 
Fulminate  of  mercury,  255 

Analysis  of,  256 


INDEX 


757 


Fulvene,  521 

Fumaria  officinalis,  313 

Furan,  619,  620 

Furazan,  623 

Furazole,  623 

Furfuraldehyde  (Furfural),  145,  430,  620 

Furnace,  Combustion,  7 

Gas,  41 

Fusel  oil,  90,  122,  144 
Fuses,  255 

Bickford,  257 

Electric,  257 

GALACTOSE,  430,  437 
Galalith,  386 
Galazin,  160 
Galbanum,  544 
Gallocyanine,  661,  673 
Gambier,  669 
Gas,  Air,  53 

Blue,  52 

Illuminating,  36  et  seq. 

Marsh,  32 

Oil,  57,  82 

Producer,  53 

Riche,  53 

Suction,  53 

Water,  52,  82 
Gases,  Permanent,  33 
Gasogen,  42 
Gasolene,  35,  66 
Gasometers,  48 

Suspended,  49 

Telescopic,  48 

Gaultheria  procumbens,  106 
Gelatine,  739 

Blasting,  241 

dynamites,  241,  242 
Geranial,  209 
Geranine,  679 
Geraniol,  182,  209,  601 
Gin,  160 
Globin,  737 
Globulins,  736 
Glucoproteins,  739 
Glucosamine,  427,  432 
Glucose,  433,  437 

Detection  of,  434 

Estimation  of,  433,  486 

Granulated,  434 

Hydrated,  434 

Manufacture  of,  434 
Glucosides,  432,  437,  740 
Glucosone,  436 
Glucosoxime,  432 
Glue,  739 

Analysis  of,  740 

Manufacture  of,  739 
Glutarimide,  354 
Gluten,  497 
Glyceraldehyde,  329 
Glycerides,  183,  370,  372 

Synthesis  of,  373 
Glycerol  (Glycerine),  35,  122,  183 

Qualities  of,  188 

Refractive  index,  184 

Statistics,  188 

Tests  for,  188 
Glycerose,  329 

Glycine  (Glycocoll),  317,  322,  355 
Glycocyamidine,  366 
Glycocyamine,  366 
Glycogen,  114,  503 
Glycol,  183 


Glycol  acetates,  213 

chlorohydrin,  213 

dinitrate,  213 

Ethyl  ethers  of,  213 

mercaptan,  213 
Glycollamide,  353 
Glycollic  aldehyde,  329,  428 
Glycollide,  322 
Glycols,  88,  182 

Higher,  183 

Propylene,  183 
Glycosine,  329 
Glycylglycine,  734 
Glyoxal,  329 
Glyoxaline,  329,  623 
Glyoxiline,  231 
Gnoscopine,  633 
Gommeline,  501 
"  Grains,"  169 
Grape -must,  155 
Greek  fire,  248 
Green  naphtha,  84 

oil,  84 

starch,  495 
Green,  Algol,  665 

Alizarin,  663 

Brilliant,  675 

Diamine,  678 

Diamond,  675 

Fast,  for  cotton,  659 

Indanthrene,  665 

Italian,  678 

Janos,  675 

Malachite,  607,  660 

Methylene,  661 

Naphthol,  659 

Pyrogen,  678 

Schweinfurth's,  287 

Sulphur,  678 
Grisounite,  247 
Guaiacol,  544 
Guanamines,  365 
Guanidine,  365 

Amino-derivative  of,  366 

nitrate,  366 

Nitro -derivative  of,  366 
Guanine,  368,  369 
Gum,  502 

arabic,  502 

Artificial,  501 

British,  501 

dynamites,  241 

Starch,  501 

tragacanth,  502 
Guncotton,  232 

Compression  of,  238 

Manufacture  of,  234 

Properties  of,  233 

Pulping  of,  237 

Stabilisation  of,  237 

Thomson  and  Nathan's  process  for,  236 

Uses  of,  238 
Guttapercha,  599 

H^IMATEIN,  666 
Haematin,  737 

hydrochloride,  738 
Haematoxylin,  666 
Hsemin,  738 
Hsemocyanin,  114 
Haemoerythrin,  114 
Haemoglobin,  113.  114,  737 
Hair,  Artificial,  702 
Half-stuff,  509 


758  INDEX 

Halides,  Acid,  316,  317 
Halogens,  Detection  of,  7 

Estimation  of,  11 

Hansena  fermentation  vessels,  175 
Hardened  glass,  80 
Heat  of  combustion,  25 

explosion,  216 

formation,  25 

of  explosives,  216 

neutralisation,  25 
Heaters  for  sugar-juice,  452,  461 
Hedonal,  99,  629 
Helicin,  741 
Heliotrope,  Ciba,  664 
Heliotropin,  574 
Hemicellulose,  503 
Hemimellithene,  527 
Hemiterpene,  598 
Hemp,  688 

seeds,  391 
Heneicosane,  31 
Hentriacontane,  31,  36 
Heptachloropropane,  101 
Heptacosane,  31,  36 
Heptadecane,  31 
Heptaldehyde,  209 
Heptane,  31,  36 
Heptoses,  437 
Heptylbenzene,  106 
Heracleum  giganteum,  106,  181 

spondylium,  181 
Hesperidene,  595 
Hesperidin,  741 

Heterocyclic  compounds,  28,  520,  619 
Hexabenzylethane,  610 
Hexabioses,  438 
Hexabromobenzene,  537 
Hexacetylmannitol,  189 
Hexachlorobenzene,  537 
Hexachlorohexahydrobenzene,  538 
Hexacontane,  31,  36 
Hexacosane,  31 
Hexadecane,  31 
Hexadione,  334 
Hexaethylbenzene,  527 
Hexahydrobenzene,  592 
Hexahydrocymene,  593,  596 
Hexahydrophenol,  592 
Hexahydropyridine,  626 
Hexahydroxybenzene,  546 
Hexahydroxybenzophenone,  584 
Hexahydroxycyclohexane,  546 
Hexahydroxydiphenyl,  606 
Hexamethyl benzene,  91,  527,  535 
Hexamethylene,  87,  592 
Hexamethylenetetramine,  157,  205,  207 
Hexandiine,  94 
Hexanes,  31,  35 
Hexanhexol,  189 
Hexanol,  181 
Hexaphenylethane,  608 
Hexapropylbenzene,  527 
Hexine,  90 
Hexitols,  427,  433 
Hexosaccharinc,  432 
Hexoses,  431 

Constitution  of,  432 
Hides,  Dyeing  of,  591 

Finishing  of,  590 

Graining  of,  590 

Tanning  of,  586 
Histones,  737 
Hollanders,  508,  513 
Holocaine,  99,  629 


Homoasparagincs,  356 
Homocamphoric  nitrile,  603 
Homologues  of  aniline,  560 

benzaldehyde,  571 

phenol,  543 

succinic  acid,  310,  311 

terpenes,  598 
Homology,  23 
Homophthalimide,  637 
Homopyrocatechol,  544 
Honey,  435 
Hops,  162 

Decoction  of,  170     ' 
Humic  substances,  432 
Humulus  lupulus,  162 
Hydantoin,  364 
Hydracellulose,  505 
Hydramine,  213 
Hydrastine,  632 
Hydrastinine,  632 
Hydraulic  accumulators,  393 

gas  main,  43 

press,  251,  392 
Hydrazides,  358,  570 
Hydrazines,  565,  569 
Hydrazobenzene,  566 
Hydrazodicarbonamide,  366 
Hydrazones,  206,  427 
Hydroanthracene,  615 
Hydroanthranols,  616 
Hydrobenzamide,  571 
Hydrobenzoin,  609 
Hydrocarbons,  28,  30 

Aromatic,  526 

of  petroleum,  62 

of  the  C«H2«  2  series,  90 

of  the  C«H2«  4  and  C«H2«-6  series,  94 

Saturated,  28,  30,  31 

Unsaturated,  28,  87,  96 

with  triple  linkings,  90 

with  unsaturated  side-chains,  535 
Hydrocellulose,  503,  504 
Hydrocinchonidine,  634 
Hydrocotarnine,  633 
Hydrocyanocarbodiphenylimide,  644 
Hydrogen,  Estimation  of,  7 

Nascent,  32 

Typical  alcoholic,  106 
Hydrolysis,  104,  438 

Enzymic,  112 
Hydronaphthalene,  612 
Hydropyridines,  626 
Hydroquinine,  634 
Hydroquinone,  544 
Hydroxy-acids,  Aromatic,  582 

Higher,  326 

polybasic,  351 

Polyvalent  dibasic,  334 
monobasic,  328 
tribasic,  345 

Saturated  monobasic,  326 

Unsaturated  monobasic,  320 
Hydroxy-alcohols,  573 
Hydroxy-aldehydes,  Aromatic,  573 
Hydro xyanthranol,  617 
Hydroxyanthraquinones,  616 
Hydroxyazo-compounds,  565 
Hydroxybenzaldehydes,  574 
jS-Hydroxybutyraldehyde,  205 
Hydroxyethylamine,  213 
Hydroxyethyltrimethylammonium  hydroxide, 

214 

Hydroxyhydroquinone,  545 
Hydroxylamine,  167 


INDEX 


759 


Hydroxylamine  derivatives  of  acids,  358 
Hydroxylinolein,  400 
Hydroxymethyleneacetone,  331,  334 
Hydroxymethyleneketones,  334 
Hydroxymethylfurfural,  430 
Hydroxynitriles,  199 
Hydroxypyridines,  625 
2-Hydroxyquinoline,  637 
Hydroxytoluenes,  543 
Hyoscyamine,  632 
Hyphomycetes,  111,  130 
Hypnone,  572 
Hypnotics,  98,  629 
Hypoxanthine,  368 


ICHTHYOFORM,  84 

Ichthyol,  84 
Ichthyolsulphonates,  84 
Iditol,  190 
Illuminating  gas,  36 

Analysis  of,  53 

Calorific  value  of,  38,  54,  55 

Composition,  of ,  38 

History  of,  36 

Lighting  power  of,  55 

Meters,  50 

Physical  and  chemical  testing  of,  53 

Price  of,  51 

Properties  of,  '.  8 

Purification  of,  43,  46 

Separation  of  naphthalene  from,  44 

Statistics  of,  52 

Yield  of,  51 
Imidazole,  623 
Imides,  353 
Iminocarbamide,  365 
Iminocarbamideazide,  366 
Iminochlorides,  356 
Iminoethers,  352,  353 
Iminothioethers,  357 
Iminourea,  365 
Impermeable  fabrics,  286 
Indamine,  647,  661 
Indanthrene,  471,  665 
Indazin,  676 
Indazole,  639 
Indene,  614 

Index  of  refraction,  26,  375 
Indican,  640 

of  urine,  638 
Indigo,  639,  663 

Analysis  of,  640 

blue,  640 

carmine,  641 

Colloidal,  641 

extract,  676 

Properties  of,  641 

Statistics  of,  645 
artificial,  645 

Syntheses  of,  642 
Indigofera  erecta,  640 

leptostachya,  640 

tinctoria,  639 
Indigoids,  663 
Indigolignoids,  665 
Indigotin,  640 
Indirubin,  664 
Indoin,  656 
Indole,  638 
Indolignone,  665 
Indonaphthalene,  665 
Indophenin,  620,  621 
Indoxyl,  638,  640,  644 


Indrene,  615 

Indulins,  661 

Infusorial  earth,  223,  229 

Injectors,  Korting,  48 

Ink,  583 

Inositol,  546,  592 

Inulin,  435,  436 

Inversion,  433,  441 

Invert  sugar,  433,  485 

Invertase  (Invertin),  111,  112,  441 

lodobenzene,  536,  537 

lodobutane,  97 

lodoform,  100 

Tests  for,  101 
lodol,  621 
lodopropane,  97 
lodosobenzene,  536 

chloride,  536 
lodourethane,  363 
lodylbenzene,  536 
lonene,  599 

Ionic  concentration,  441 
lonone,  595,  599 
Irene,  599 
Iridin,  741 
Irigenin,  741 
Irone,  599 
Isatin,  638,  642 

chloride,  642 
a-Isatinanilide,  644 
Isatis  tinctoria,  639 
Isatoxime,  642 
Isoamyl  valerate,  372 
Isoamylbenzene,  527 
Isobutane,  35 
Isobutyl  iodide,  97 
Isobutylbenzene,  527 
Isobutylcarbinol,  105,  122 
Isocyanates,  359 
Isocyanides,  199 
Isocyclic  compounds,  28 
Isocymene,  535 
Isodulcitol,  431,  668 
Isodurenes,  527,  535 
Isoduridine,  555 
Isoeugenol,  544,  57 
Isolactose,  438 
Isology,  23 
Isomaltose,  113,  438 
Isomelamine,  362 
Isomerides,  16 

Boiling-points  of,  24 

Melting-points  of,  24 

Metameric,  17 

Optical,  18 

Racemic,  19 
Isomerism,  14,  16 

Cis-  and  trans-,  21 

Space,  18 

Isonitriles,  199,  358 
Isonitrosoketones,  211,  333 
Iso-oxazole,  623 
Isopentane,  35 
Isoprene,  90,  598 
Isopropyl  iodide,  96,  97 
Isopropylacetylene,  90 
Isopropylbenzaldehyde,  572 
Isopropylbenzene,  527,  535 
Isoquinoline,  637 
Isorhamnose,  431 
Isovaleryl  chloride,  319 
Isoviolanthrene,  665 
Isuret,  358 
Ivory,  Artificial,  290 


760 


INDEX 


JIGGERS,  721 
Jute,  689 

KEFIR,  115,  160 

Keratin,  683,  739 

Kerosene,  63 

Keto -aldehydes,  330,  334 

Keto-arabinose,  428 

Ketoheptamethylene,  521 

Ketohexamethylene,  521,  592 

Ketohexoses,  427,  431 

Ketoketenes,  213 

Ketones,  96,  103,  203,  204,  210 

Aromatic,  572 

Strache's  estimation  of,  212 
Ketonimides,  203 
Ketopentamethylene,  521 
Ketoses,  427,  435 
Ketoximes,  210,  572 

Beckmann's  transposition  of,  210,  573 
Khaki,  669 
Kieselguhr,  223,  229 

Kneading  machine,  Werner-Pfleiden  r,  384 
Koji,  130 
Koumis,  160 
Kunerol,  385 
Kwan,  58 
Kyanol,  557 

LACCASE,  112 

Lacs,  400 

Lactalbumin,  735 

Lactams,  355 

Lactases,  112 

Lactic  acid  bacillus,  323 

Lactides,  321 

Lactite,  386 

Lactoglobulin,  736 

Lactone,  Bromobutyric,  295 

Isocaproic,  297 
Lactones,  295,  322,  428 
Lactose,  438,  486 

Testing  of,  440 
Lactyl  chloride,  325 
Lager  beer,  170,  172 
Lakes,  650 
Lamp,  Carcel,  56 

Hefner,  Alteneck,  56 
Lampblack,  528 
Lanite,  244 
Lard,  388 
Laudamine,  632 
Laudanidine,  632 
Laudanosine,  632 
Laurene,  596 
Lautopine,  633 
Law  of  Dalton,  5 

esterification,  370 

Hess-Berthelot,  25 

refraction,  26 
Leather,  586 
Lecanora  tartarea,  668 
Lecithin,  374 
Lecithins,  215 
Lees,  Wine,  143,  337,  341 
Lemons,  Cultivation  of,  347 

Treatment  of,  347 
Leucine,  19,  355,  734 
Leu co -bases,  607,  647 
Leucocytes,  115 
Leucotannin,  584 
Levulose,  435,  485 
Life,  Origin  of,  114 
Light  Polarised,  26,  330 


Light,  Sources  of,  57 

Standards  of,  55 
Lignin,  505,  512 

Estimation  of,  509 
Ligroin,  66 

Limonene,  593,  595,  596 
Linoleum,  400 
Linseed,  Composition  of,  391 

oil,  399 

Linum  usitatissimum,  399,  687 
Lipase,  112,  409 
Lipoids,  629 
Lippich  polariser,  484 
Liqueurs,  159 

Liquids,  Specific  gravity  of,  (i 
Lithoclastitc,  231 
Lithographers'  varnish,  400 
Litmus,  668 
Lupetidine,  626 
Lupulin,  170,  173 
Luteolin,  638 
Lutidines,  625 
Lyddite,  245,  503 
Lysidine,  623 
Lysi  e,  328,  356 
Lysins,  115 
Lysoform,  208 
Lysol,  543 
Lyxose,  431 

MACLURIN,  668 

Madder,  617 

Magnesia,  Effervescent,  346 

Maize,  119,  162 

Composition  of,  391 

oil,  403 
Malamide,  353 
Malaria,  635 
Malt,  112,  116 

Cleaning  of,  168 

Dias^atic  power  of,  107 

Evaluation  of,  167 

Green,  164 

Grinding  of,  168 

Kilning  of,  166 

Mashing  of,  168 
Maltase,  111,  112,  117,  438 
Malting,  164 

Maltodextrinase,  112,  171 
Maltol,  505,  582 
Maltose,  113,  167,  438,  486 
Mammoth  pump,  226 
Manna,  189 
Mannide,  190 
Mannitan,  190 
Mannitol,  189,  428 

Hexacetyl-derivative  of,  189 
Mannose,  436 
Mannotetrose,  489 
Mannotriose,  190 
Margarine,  382,  383 

cheese,  382 

Statistics  of,  384 
Margol,  383 
Marsala,  159 
Mashing  apparatus,  169 
Massecuite,  468 
Masut,  67,  74 
Meconidine,  632 
Melam,  362 
Melamine,  362 
Melene,  90 
Melibiase,  112 
Melibiose,  438,  442 


INDEX 


761 


Melinite,  245,  563 
Melissyl  palmitate,  372 
Mellite,  581 
Mellithene,  535 
Menthane,  596 
Menthene,  596 
Menthol,  600 
Menthone,  600 
Mercaptan,  196 
Mercaptans,  195 
Mercaptide,  Mercuric,  196 

Sodium,  196 
Mercaptides,  195 
Mercaptol,  210 
Mercerisation,  506,  686,  728 
Mercury  fulminate,  255 
Mesidine,  555 
Mesitol,  540 
Mesityl  oxide,  212 
Mesitylene,  91,  535 
Metacymene,  527 
Metadiamines,  557 
Metaformaldehyde,  207 
Metaldehyde,  208 
Metalepsy,  15 
Metamerism,  17,  192 
Metastyrene,  535 
Meters,  Alcohol,  146 

Automatic  gas,  51 

Dry  gas,  51 

Gas,  50 
Methanal,  206 
Methanamide,  352 
Methanamidoxime,  358 
Methane,  23,  32 

Derivatives  of,  30 

Industrial  uses  of,  34 

Preparation  of,  34 

Properties  of,  33 
Methanol,  106 
Methanthiol,  196 
Methene,  89 

Methenylamidoxime,  358 
Methoxymethane,  192 
Methoxypyridine,  625 
Methyl,  29 

acetate,  371 

chloride,  96 

cyanide,  198,  199 

iodide,  97 

isothiocyanate,  361 

mustard  oil,  361 

nonyl  ketone,  332 

sulphide,  196 
Methylacetanilide,  560 
Methylacetylurea,  352 
Methylal,  209 
Methylamine,  201 

hydrochloride,  97,  201 

sulphate,  201 
Methylaniline,  559 
Methylanthracene,  616 
Methylarbutin,  741 
Methylbenzene,  534 
Methylbutanol,  181 
Methylcyanamide,  362 
Methyldihydroimidazole,  623 
Methylene,  89 

bromide,  95,  98 

chloride,  95,  98 

iodide,  95,  98 
Methylethylacetylene,  90 
Methylethylcarbinol,  181 
Methylglyoxal,  334 


Methylheptanone,  303 
p-Methylisopropylbenzene,  535 
Methylisopropylcarbinol,  105 
Methylnaphthalenes,  614 
Methylpentoses,  431 
Methylpropane,  29,  35 
Methylpropanol,  181 
Methylpseudoisatin,  638 
Methylpyridine,  625 
Methylpyridone,  625 
a-Methylquinoline,  637 
Methylsulphonal,  629 
Methyluracyl,  367 
Methylurethane,  358 
Metol,  564  , 
Microbes,  110 
Micrococci,  110 
Micron,  110 
Milk,  112,  385 

Analysis  of,  386 

C  jco-nut,  402 

Fermented,  160 

Skim,  385 
Milling,  714 
Moellon,  389 
Molasses,  469,  473 

Beet-sugar,  140 

Lactose,  440 

Recovery  of  sugar  from,  474-476 

Utilisation  of,  473 
Monoacetin,  214 
Monoacylhydrazides,  358 
Monoazo -compounds,  656 
Monochlorhydrin,  214 
Mononitroglycerine,  222 
Mononitrotoluenes,  550 
Monosaccharides,  426 
Monoses,  426 

Formation  of,  427 
Mordanting,  651,  706,  710 
Mordants,  650 
Morin,  638 

Morphine,  115,  628,  632 
Morpholine,  626 
Morphotropy,  24 
Morus  tinctoria,  668 
Motochemistry,  523 
Moulds,  111 
Mucins,  739 

Mucors,  111,  130,  131,  346 
Murexide,  367,  368 
Muscarine,  214 
Mustard,  Black,  361 

seed,  391 

Muta-rotation,  27,  430,  485 
Mycoderma  aceti,  280,  281 

vini,  281 
Myosin,  737 
Myristin,  289 

NAPHTHA,  58 
Naphthalene,  531,  610,  643 

derivatives,  610 

from  coal-gas,  44 

tetrachloride,  614 
a-Naphthaquinone,  613 
/3-Naphthaquinone,  614 
Naphthazarin,  659 
Naphthenes,  63,  592     ' 
Naphthindigo,  664 
Naphthols,  613 

a-  (and  £-)  Naphthylamine,  613 
Narceine,  628,  632 
Narcotine,  628,  632,  633 


762 


INDEX 


Natron,  415 
Neroline,  613 
Neurine,  214 
Nic"ol  prism,  483 
Nicotine,  628,  629 
Nicotyrine,  630 
Nitracetanilides,  560,  562 
Nitriles,  198,  575 

Constitution  of,  199 
Nitroacetins,  224 
Nitroanilines,  561 
Nitroanthracenes,  616 
Nitrobenzaldehyde,  572,  643 
Nitrobenzene,  549,  566 
Nitrocellulose,  232 

constitution  of,  232 
Nitrochlorhydrin,  223 
Nitrocymene,  548 
Nitro-derivatives,  Aromatic,  197,  547,  548 

Electrolytic  reduction  of,  566 
Nitrodimethylaniline,  559 
Nitroethane,  198 
Nitroform,  198 
Nitroformins,  224 
Nitrogen,  Detection  of,  6 

Estimation  by  Dumas'  method,  10 
Kjeldahl's  method,  10 
Will  and  Varrentrapp's  method,  11 
Stereoisomerism  of,  22 
Nitroglycerine,  223 
Filtration  of,  228 
Manufacture  of,  225 
Stabilisation  of,  228 
Uses  of,  229 
Nitroguanidine,  366 
Nitrohexane,  198 
Nitromesitylene,  548 
Nitron,  563 

Nitronaphthalenes,  612 
.Nitrophenols,  562 
Nitrophenoxides,  562 
p-Nitrophenylhydrazine,  570 
Nitroprehnitene,  548 
sec.  Nitropropane,  198 
Nitro.amines,  201,  556,  567 
Nitrosites,  593 
Nitrosochlorides,  593 
p-Nitrosodimethylaniline,  559 
Nitrosodipentene,  594 
Nitrosophenol,  559 
Nitrosopyrroles,  622 
Nitrotoluenes,  550 
Nitrourea,  364 
Nitrourethane,  363 
Nitroxylenes,  548 
Nomenclature,  Official,  28 
Nonane,  31 
Nonodecane,  31 
Nonoses,  437 
Non-sugar,  447,  473 
Nonyl  aldehyde,  209 
Nuclei,  Condensed  benzene,  605 
Nucleins,  738 
Nucleo-albumins,  737 
Nucleo-histone,  737 
Nucleoproteins,  738 
Number,  Acetyl,  188,  189 
Acetyl  acid,  189 
Acetyl  saponification,  189 
Arid,  86,  375 
Butter,  387 
Ester,  377 
Hehner,  373 
Iodine,  375 


Number,  Kottstorf,  379 

Maumene,  376 

Polenske,  387 

Reichert-Meissl-Wollny,  373,  387 

Saponification,  379 
Nutrose,  386,  737 
Nux  vornica,  633 


OCTADECAPEPTIDE,  735 

Octadecylbenzene,  527 
Octadiene,  90 
Octane,  31 
Octocosane,  31 
Octodecane,  31 
Octoses,  437 
Octylbenzene,  527 
(Enanthaldehydo,  209 
(Enoxydase,  112 
Oil,  Acetone,  212 

Allyl  mustard,  361 

Almond,  378 

Aniline,  558,  559 

Anise,  543 

Anthracene,  530,  532 

Arachis,  378,  397,  404 

Bitter  almond,  571 

Boiled  linseed,  399 

Bone,  620 

Camphor,  604 

Castor,  326,  378,  398 

Clove,  544 

Coco-nut,  378,  402 

Colz.i,  378 

Cotton-seed,  378,  403 

Chinese  bean,  404 

Cod-liver,  378,  389,  400 

Dippel  animal,  620 

Ethyl  mustard,  361 

Fish,  389 

for  gas,  82 

Gelatinised  vaseline,  80 

Gingdly,  404 

Grape  seed,  405 

Hempseed,  378 

Linseed,  378,  399 

Maize,  378,  403 

Methyl  mustard,  361 

Oleo,  384 

Olive,  373,  378,  395 

Palm,  378,  401 

Palm-nut  (Palm-kernel),  378,  401,  402 

Paraffin,  66,  81,  82 

Poppy-seed,  378,  400 

Propyl  mustard,  361 

Resin,  78,  596 

Sanse,  397 

Sesame,  378,  404 

Soja-bean,  378,  404 

Solar,  63,  82 

Sperm,  389 

Stillingia,  403 

Sulphocarbon,  396 

Teel,  404 

Tomato-seed,  405 

Turkey-red,  327,  395 

Turpentine,  593,  596,  597 

Walnut,  400 

Wrashed  olive,  396 

Whale,  378,  389 

Wool,  390 
Oil-cake,  391,  405 
Oil-gas,  57 
Oils,  Animr.l,  378,  379 


INDEX 


763 


Oils,  Bleaching  of,  395 
Blown,  375 
Creosote,  531 
Deodorisation  of,  395 
Drying,  374 
Engine,  78 
for  gas,  82 
Flash-point  of,  79 
Heavy,  66 

Mineral  lubricating,  63,  74 
Mustard,  361 
Oxidised,  375 
Refining  of,  394 
Spindle,  78 
Thickened,  400 
Vegetable,  378,  390 
Viscosity  of,  72,  79 
Olease,  395 
Olefines,  28,  87 

Constitution  of,  89 
Nomenclature  of,  87 
Preparation  of,  88 
Table  of,  87 
Oleine,  298,  407 
Catalytic,  419 
Distilled,  408,  419 
Saponification,  419 
Transformation  into  stearme,  41 
Wool,  390 
Oleomargarine,  382 
Olive,  Composition  of,  391 

oil,  395 
Opium,  632  . 

Estimation  of  morphine  in,  <o6t 

Opsonins,  115 

Optical  activity,  19,  61 

antipodes,  22 
Orange,  Alizarin,  675 

Croceine,  656 

G,  656 

Indanthrene  golden,  665 

II,  656 
IV,  656 
Orceine,  544 
Orcinol,  544 

Organo-metallic  compounds,  M6 
Origanum  hirtum,  543 
Ornithine,  328,  356 
Orthobromobenzyl  bromide,  bib 
Ortho-diamines,  557 
Ortho -ethers,  268 
Orthoform,  99,  629 
Osamines,  427 
Osazones,  427,  435,  661 
Osmophores,  595 
Osones,  436 
Osotriazole,  623 
Ossein,  739 
Oxalates,  307 
Oxamide,  353 
Oxamines,  661 
Oxidation,  Enzymic,  11-J 
Oxidation  chamber,  731 
Oximes,  Aromatic,  572 
Oximide,  353 
Oxindole,  638 

Synthesis  of,  642 
Oxy-acetylene  blowpipe,  93 
Oxycellulose,  505,  506 
Oxydases,  112 
Oxygenases,  112 
Oxyhaemoglobin,  738 
Oxynarcotine,  632 
Ozoform,  208 


Ozokerite,  30,  80,  85 
Ozonides,  299 

PALM  fruit,  391 

oil,  401 
Palmer,  725 
Palm -kernel,  391 

oil,  378,  401,  402 
Palmitates,  290 
Palmitin,  290 
Panclastite,  245 
Papaver  somniferum,  MZ 
Papaveramine,  633 
Papaverine,  632 
Paper,  506 

Bisulphite  process,  51-i 
Boiling,  508 
Colouring,  515 
Electric  process,  513 
Loading,  515 
Microscopical  testing,  51b 
Paraffined,  506 
Parchment,  506 
Sizing,  514 
Statistics,  517 
Testing,  516 
Vulcanised,  506 
Para-anthracene,  615 
Paracasein,  737 
Paracyanogen.  359 
Paradiamines,  557 
Paraffin  wax,  80 
Analysis,  86 
Estimation,  86 
Statistics,  85 
Paraffins,  28,  30 
Paraformaldehydc,  207 
Paraglobulin,  114 
Paraldehyde,  206 
Paraleucanilin  ,  607 
Pararosaniline,  607 
.    Parchment,  Artificial,  oOb 
Parthenogenesis,  Artificial,  115 
Partial  pressures,  5 
Pasteur  flasks,  124 
Pasteurisation,  156,  177 
Pastinaca  sativa,  108 
Patent  blue,  660 
Penicillium  glaucum,  22 
Pentachloroanisole,  543 
Pentacosane,  31 
Pentadecane,  31 
Pentaerythritol,  189 
Pentaethylbenzene,  527 
Pentahydroxycyclohexane   o46 
Pentahydroxypentane,  1* 

Pcntaline,  102 
Pentamethylbenzene,  527 
Pentamethylene,  521 
Pentamethylenediamme,  M* 
Pentamethylpararosamlmc,  bl 
Pentanediine,  90 
Pentanes,  35 
Pentanol,  181 
Pentaphenyle thane,  609 
Pentatricontane,  31 
Pentenes,  90 
Pentitols,  427 

Pentosans,  430 

Estimation  of,  430 

Pentoses,  429 

Estimation  of,  430 

Pentosuria,  431 

Peptase,  112 


764 

Peptones,  734,  737 
Perfumes,  593 
Pergamin,  506 
Peroxydases,  112 
Peroxyozonides,  296 
Perseo,  668 
Petrinage,  243 
Petrolene,  83 
Petroleum,  58 

American,  70 

Composition  of,  62 

Crude,  62 

Desulphurising  of,  69 

Distillation  of,  66,  67 

ether,  66 

Extraction  of,  64 

Flash-point  of,  73 

fountains,  64 

History,  58 

Illuminating  power  of,  72,  73 

Italian,  64 

Optical  activity  of,  61 

Origin  of,  59 

Pipe-lines  for,  65 

Properties  of,  62 

Purification  of,  68 

Refining  of,  66 

residues,  74 

Russian,  63,  70 

Specific  gravity  of,  62 

Statistics  of,  70 

tanks,  69 

Tests  for  lighting,  72 

Uses  of,  70 

Viscosity  of,  72 
Petroline,  66 
Phaeophytin,  670 
Pharaoh's  serpents,  361 
Phellandrene,  596 
Phenacetin,  564 
Phenanthraquinone,  619 
Phenanthrene,  88,  618 
Phenazine,  647,  661 
Phenetidines,  564 
Phenetole,  542,  564 
Phenol,  541 

Acid  derivatives  of,  542 

Homologues  of,  543 

Pure  synthetic,  541 

Testing  of,  541 
Phenolphthalein,  581,  660 
Phenols,  530,  539 

Dihydric,  543 

Monohydric,  539 

Polyhydric,  546 

Table  of,  540 

Trihydric,  545 
Phenoxazine,  647 
Phenoxides,  539,  541 
Phenyl  disulphide,  564 

hydrosulphide,  564 

salicylate,  582 

sulphide,  564 
Phenylacetanilide,  560 
Phenylacetylene,  535 
Phenylamine,  557 
Phenylanthracene,  616 
Phenylanthranol,  616 
Phenylbenzamide,  560 
Phenylchloracetamide,  560 
Phenyldiazonium  chloride,  567,  568 
hydroxide,  568 
nitrate,  567,  568 
Phenyldinitrotoluidine,  553 


INDEX 


Phenylcncdiamines,  550,  561 
Phenylglycerol,  570 
Phenylglycocoll,  560 
Phenylglyoxal,  574 
Phenylhydrazine,  570 

hydrochloride,  569 
Phenylhydroxylamine,  565,  566,  570 
as.  Phenylmethylhydrazine,  570 
Phenylnitromethane,  553,  567 
Phenylsuccinimide,  354 
Phlegm,  133 
Phlobaphenes,  587 
Phloretin,  741 
Phloridzin,  741 
Phloroglucinol,  545 
Phosgene,  98,  99,  363 
Phosphine,  663 
Phosphines,  202 
Phosphorus,  Detection  of,  7 

Estimation  of,  12 
Photogen,  82 

Photographic  developers,  564 
Photometer,  Bunsen's,  56 

Lummer  and  Brodhun's,  57 
Phthaleins,  581,  608 
Phthalide,  580 
Phthalideine,  616 
Phthalidine,  616 
Phthalimide,  581,  643 
Phthalophenone,  580,  608 
Phthalyl  chloride,  580 
Physostigmine,  628 
Phytochlorin,  670 
Phytoglobulins,  736 

Phytol,  670 

Phytorodin,  670 

Phytosterol,  742 

Piazthiol,  670 

Picene,  619 

Picoline,  209,  625 

a-Picolylalkine,  625 

Picramide,  562 

Picrotoxin,  628 

Pierrite,  255 

Pigments,  655 

Pimpinella  anisum,  543 

Pinacoline,  183 

Pinacones,  182 

Pinane,  596 

Pinene,  T.96 

hydrochloride,  597 

Pinitol,  546 

Pink  salt,  693 

Pinnoglobin,  114 

Pipecoline,  626 

Piperazine,  214 

Piperidine,  90,  626 

Piperidines,  626 

Piperine,  626 

Piperonal,  574 

Pitch,  83,  532 
Coal,  83 
Mineral,  83 
Stearine,  508 

Pittacal,  660 

Plasmon,  386,  737 

Plastering  oi  wines,  156,  157 

Plastrotyl,  553 

Platinichlorides,  13 

Pluszucker,  442 

Polarimeters,  27,  483 

Polarimetry,  484 

Polarisation  of  light,  26 

Polyazo -compounds,  656 


INDEX 


705 


Polyglycerides,  184 

Polymer  ism,  14 

Polymethylenes,  520 

Polymorphism,  24 

Polynitro  benzenes,  549 

Polypeptides,  734 

Polysaccharides,  426 

Ponceau,  656 

Poppy,  Composition  of,  391 

Populin,  741 

Potatoes,  Dry  matter  in,  490 

Starch-content  of,  117,  490 
Precipitins,  115 
Prehnidine,  555 
Prehnitene,  527 
Pressed  yeast,  125 
Primuline,  564,  663 
Printing  of  fibres,  707 

textiles,  707,  730 

yarns,  707 
Proline,  739 
Propaldehyde,  209 
Propane,  35 
Propanol,  180 
Propanone,  211 
Propantriol,  183 
Propargyl  aldehyde,  210 
Propene,  89 
Propenol,  182 
Propine,  90 
Propinol,  182 
Propionyl  chloride,  319 
Propyl  iodide,  95 
Propylacetylene,  90 
Propylbenzene,  527,  535 
Propylcarbinol,  180 
Propylene,  89 
a-Propylpiperidine,  625 
Propylpseudonitrole,  198 
Protamines,  737 
Proteins,  733 

Coagulable,  737 

Conjugated,  737 

Hydrolysis  of,  734 

Modified,  737 

Natural,  735 

Salts  of,  737 

Various,  740 
Proteolytic  action.  111 
Protocatechuic  aldehyde,  573 
Protococcus  vulgaris,  189 
Protopine,  632 
Protoplasm,  110,  114 
Pseudo-acids,  553,  567 
Pseudocumene,  527,  535 
Pseudocumidine,  555 
Pseudoindoxyl,  638 
Pseudoisatin,  638 
Pseudoisomerism,  17,  330 
Pseudomorphine,  632 
Pseudo-tanning,  587 
Ptomaines,  214 
Ptyalin,  112 
Pulegone,  601 
Pulp,  Chemical  wood,  507,  511 

Mechanical  wood,  507,  509 
Purgatol,  591 

Purification  by  physical  methods,  2 
Purine,  367 
Purple,  Antique,  664 
Purpurin,  616 
Purpuroxanthin,  616 
Putrescine,  214 
Pyranthrene,  665 


Pyrazine,  626 
Pyrazole,  622 
Pyrazoline,  622 
Pyrazolone,  622 
Pyrene,  619 
Pyridines,  623,  625 
Pyridones,  625 
Pyridylpyr roles,  630 
Pyrimidine,  626 
Pyrocatechol,  543 
Pyrocoll,  622 
Pyrocomane,  626 
Pyrogallol,  545 
Pyrolignite  of  iron,  285 
Pyrone,  626 
Pyronine,  660 
Pyropissite,  81 
Pyroxyline,  232,  504 
Pyrrole,  620 

Hydrogenated  derivatives  of,  622 
Pyrrolidine,  354,  622 
Pyrrolilene,  90 
Pyrroline,  622 
Pyrrothiazole,  623 
Pyruvic  aldehyde,  334 

QUEBRACHITOL,  546 

Quercetin,  638,  668 
Quercitol,  546 
Quercitrin,  638,  668 
Quercitron,  668 
Quercus  nigra,  668 

tinctoria,  668 
Quinaldine,  637 
Quinhydrone,  547 
Quinidine,  634 
Quinine,  628,  633 

bisulphate,  634 

hydrochloride,  634 

Statistics  of,  635 

sulphate,  634 
Quinitol,  592 
Quinizarin,  616 
Quinol,  544 
Quinoline,  635,  647 
Quinonediimides,  547 
Quinonedioxime,  547 
Quinoneimides,  547 
Quinonemonoxime,  547 
Quinones,  546 
Quinoxaline,  557,  662 

RACEMISATION,  22 

Radicals,  Theory  of,  14 

Raffmose,  442 

Rags,  507 

Rancidity  of  fats  and  oils,  374 

Rapeseed,  Composition  of,  391 

Rasp  for  beet,  447 

potatoes,  492 

Ravison  seed.  Composition  of,  391 
Reaction,  Adamkiewicz's,  737 

Amphoteric,  385 

Baeyer's,  88 

Baudouin's,  384 

Becchi's,  397 

Belliez's,  397 

Biuret,  734 

Blank  and  Finkenbeiner's,  207 

Bohn-Schmidt,  617 

Deniges',  346 

Grignard's,  32,  203 

Halphen's,  381,  396 

Kamarowsky's,  144 


.766 


INDEX 


Reaction,  Korner  and  Menozzi's,  314,  354 

Lichen's,  101,  107,  109 

Liebermann's,  539,  559 

Melsen's,  279 

Perkin's,  291,  576 

Rimini's,  109,  144 

Romijn's,  427 

Sabatier  and  Senderens',  34,  59,  103 

Sandmeyer's,  568,  575 

Schiff's,  206 

Scudder  and  Riggs',  107 

Tschuga Jew's,  742 

Uffelmann's,  323 

Varrentrapp's,  290 

Wallach's,  297 

Xanthoprotein,  734 

Reactions  of  aromatic  o-dihydroxy-compounds, 
544 

of  pyrroles,  621 

Reversible,  115 

en/ymic,  113 
Reagent,  Barfoed's,  434 

Deniges',  346 

Erdmann's,  627 

Fehling's,  486 

Frohde's,  627 

Lafou's,  627 

Lowe's,  704 

Mandelin's,  627 

Marquis's,  627 

Millon's,  704 

Molisch's,  704 

Schardinger's,  112 

Schiff's,  144 

Schweitzer's,  503 

Soldaini's,  487 

Twitchell's,  410 
Rectification,  3,  133 

of  alcohol,  138 
Rectifier,  Herapel,  3 

Perrier,  137 

Savalle,  135 
Red,  Algol,  665 

Ciba,  664 

Congo,  657,  672 

Diamine,  679 

Indanthrene,  665 

Janos,  679 

p-Nitraniline,  679,  680 

Pyrrole,  621 

Quinoline,  663 

Thiazine,  679 

Thioindigo,  664 

Turkey,  327,  719 
Reductases,  112 
Refraction  constant,  26 
Refractometer,  72 

Zeiss,  375 
Refrigerator  for  wort,  171 

Hentschel's,  120 
Rennet,  112,  115 
Residues,  Aromatic,  536 

Aryl,  536 

Resins,  Artificial,  597 
Resit,  541 
Resorcinol,  544 
Resorufin,  647,  661 
Retene,  619 
Rhamnose,  431 
Rhigolene,  35 

Rhizoporus  oligosporus,  131 
Rhodamine,  676 
Rhodamines,  660 
Rhodinol,  297 


Ribose,  431 
Rice,  162,  498 

Composition  of,  490 

Production  of,  498 

starch,  498 
Ricin,  115 

Ricinus  seeds,  Composition  of,  391 
Robin,  115 

Robinia  pseudacacia,  115 
Roburite,  246,  247 
Roccella  tinctoria,  667 
Rochelle  salt,  336 
Rodinal,  564 
Rope,  689 
Rosamine,  660 
Rosaniline,  608,  647,  649 
Rosanthrene,  679 
Rose,  Diamine,  679 
Rosin,  596 

Gallipot,  596 
Rubber,  598 

Chemical  constitution  of,  598 

substitutes,  599 
Rufanthrene,  665 
Rufiopin,  616 
Rufol,  616 
Rum,  445 
Rusma,  589 

SACCHARIMETERS,  27,  483 
Saccharin,  579 
Saccharometer,  Balling,  129 
Saccharomyces  cerevisise.  111,  112,  114,  121 

155 

Saccharomycetes,  111 
Saccharone,  344 
Saccharose,  440 
Saccharum  officinarum,  443 
Safranines,  661 
Salicin,  437,  574,  582,  741 
Salicylaldehyde,  574 
Saligenin,  437,  574,  582 
Salin,  155 
Salmin,  737 
Salol,  582 
Salt,  Kalle's,  643 

of  sorrel,  307 

Rochelle,  336 
Salvarsan,  564 
Sanguemelassa,  140 
Sanse,  396 
Santalin,  669 
Santaline,  633 
Santonin,  741 
Saponification,  104 
Saponin,  115,  741 
Sarcosine,  323,  355,  366 
Sawdust,  Utilisation  of,  274 
Scarlet,  Biebrich's,  566,  657 

Ciba,  664 

Cochineal,  657 

Indanthrene,  665 

Palatine,  657 

Thioindigo,  664 
Scheelisation,  185 
Schists,  Bituminous,  83,  84 
Schizomycetes,  110 
Schizosaccharomyces  Pombe,  171 
Scrubbers,  44" 
Sealing-wax,  597 

Artificial,  541 
Securite,  247 

Seeds,  Composition  of  oily,  391 
Semicarbazide,  206,  364 


INDEX 


rer 


Semicarbazones,  206,  364 
Separators,  Centrifugal,  395 

Naphthalene,  44 

Spray,  462 

Tar,  43 

Sericin,  690,  692,  740 
Sericoin,  740 
Series,  Aliphatic,  28 

Ethylene,  87 

Fatty,  28 

Homologous,  23 

Isologous,  23 

Paraffin,  30 
Sorine,  355 

Sero -therapy,  115.  629 
Serum,  Physiological,  115 
Serum-albumin,  114,  735 
Serum-globulin,  736 
Serum-lipase,  374 
Sesame  seeds,  Composition  of,  391 
Sesamin,  404 
Sesamol,  404 
Shale,  84 
Shalonka,  65 
Shoddy,  682 
Silk,  690 

Artificial,  698 

Composition  of,  692 

Crackle  (Scroop)  of,  693 

Dyeing  of,  692 

Sea,  698 

Statistics  of,  695 
artificial,  703 

Tussah,  691,  696 

Waste,  692 

Weighting  of,  693,  694 

Wild,  691,  696 
Silk  finish,  726 
Silkworm  culture,  690 
Sinapine,  632 
Sinigrin,  741 
Sitosterol,  404 
Skatole,  638 
Soap,  298,  415 

Analysis  of,  425 

barring  machine,  423 

boiling,  418 

Eschweg,  422 

Finishing  of,  417 

Marseilles,  419 

Mottled,  421 

Oleine,  419 

Resin,  420 

Seasoning  of,  424 

Soft,  422 

Statistics  of,  424 

Transparent,  422 
Sodiocellulose,  506 
Sodium  acetonebisulphite,  210 
Solanine,  115 

Solubility  of  organic  compounds,  24 
Solvents,  Non-inflammable,  101 
Sorbitol,  190,  433 
Sorbose  bacterium,  190 
Sorrel,  Salt  of,  307 
Spartcine,  632 
Specific  refraction,  26 

rotation,  27 
Spent  wash,  132,  133 
Spermaceti,  389 
Sphsero  bacteria,  110 
Spirilla,  110 
Spiro  bacteria,  110 
Spirit,  Crude  wood,  107 


Spirit,  Denatured,  145,  149,  152 

of  sweet  wine,  97 

of  wine,  108 

Purification  of,  144 

Wood,  106 

Spiritus  setheris  nitrosi,  97 
Spitzenzucker,  442 
Spongin,  740 
Spores,  111 
Stachyose,  190 
Staphylococcus,  110,  127 
Standard  scrubber,  45 
Standol,  400 
Starch,  116,  489 

Adhesive  power  of,  500 

Analysis  of,  500 

Animal,  503 

Bleaching  of,  496 

Estimation  of,  118 

Green,  495 

gum,  501 

Maize,  500 

Microscopy  of,  491 

Rice,  498 

Saccharification  of,  119 

Soluble,  500 

Statistics  of,  500 
Steam,  Superheated,  4,  67 
Stearine,  290,  407 

Distillation,  408 

Wool,  390 
Steirolactone,  409 
Stenolytes,  608 
Stereoisomerism,  18 

of  nitrogen,  22,  210 
Stibines,  203 
Stilbene,  609 
Stillingia  sebifera,  403 
Stovaine,  629,  633 
Streptococci,  110 
String,  689 
Strychnine,  633 
Sturin,  737 
Styracin,  571 
Styrene,  535 
Suberone,  521 
Sublimation,  2 
Succinamide,  353 
Succinanil,  354 
Succinates,  306,  311 
Succindialdehyde,  620 
Succindialdoxime,  621 
Succinimide,  306,  353,  367 
Sucrase,  112,  441 
Sucrates,  441 
Sucrose,  440 
Sugar,  Acorn,  546 

Beet,  442,  445 

Cane,  440,  443 

Fruit,  435 

Grape,  433 

Invert,  433,  485 

Maple,  443 

Milk,  438 

Muscle,  546 

of  lead,  286 

Starch,  433 

Wood,  431 
Sugar  (sucrose),  Alkalinity,  488 

Ash,  488 

Beet-pulp,  453 

boiling,  466 

Centrifugation  of  massecuite,  468 

Chemical  determination,  447,  486 


768 


INDEX 


Sugar,  Clearing  (covering),  469 

Colouring,  435 

Concentration,  461  / 

Crushed,  472 

Defecation,  467 

Diffusion  process,  450 

Estimation,  481 

Fiscal  regulations,  477 

from  molasses,  473 

History,  448 

Output,  478 

Pile,  472 

Powdered,  473 

Prices,  480 

Quotient  of  purity,  487 

Refining,  470 

Rendement,  470 

Saccharimetry,  483 

Specific  gravity  and  degrees  Brix,  482 

Statistics  of  production,  477 

Steffen  process,  456 
Sugars,  Analysis  of  mixed,  487 
Sulphamides,  538 
Sulphobenzide,  538 
Sulphocyanine,  676 
Sulphohydantoin,  365 
Sulphonal,  99,  196,  210 
Sulphones,  195 
Sulphonium  compounds,  195 
Sulphoricinate,  327 

Analysis  of,  327 
Sulphur,  Detection  of,  7 

Estimation  of,  12 
Sumac,  584 

Superheated  steam,  4,  67 
Sylvestrene,  596 
Syntheses,  Asymmetric,  114 
Syn-diazobenzene  hydroxide,  568 
Syn-diazo-compounds,  566 
Syntonins,  733,  737 

TALITOL,  190 
Tallow,  380 

Chinese,  403 

tree,  403 

Vegetable,  403 
Tamping,  221 
Tanks,  Macdonald,  61 

Weiss,  61 
Tannin,  584 
Tanning  of  hides,  586 

substances,  585 

Theory  of,  586 
Tar,  Asphalte,  83 

Benzene  from,  531 

Coal,  83 

Distillation  of,  76,  82,  83 

Lignite,  81 

Mineral,  59 

oils,  530 

Statistics  of,  83 

Statistics  of  lignite,  85 

Wood,  83,  106 
Tartar,  143,  337 

Analysis  of,  337 

Cantori's  process,  340 

Cream  of,  336 

emetic,  336 

Goldenberg's  process,  338 

industry,  337 

Statistics  of,  340 

Tarulli's  method,  338 
Tartrates,  336 
Tartrazine,  345 


Tartrazins,  659 
Taurine,  214,  356 
Tautomerism,  17,  330,  648 
Tea,  369 

Tension  theory  of  valency,  88 
Tentering  frame,  724 
Terebenthene,  596 
Terpadienes,  593 
Terpane,  593,  600 
Terpanol,  600 
Terpanone,  600 
Terpenes,  593 

Complex,  596 
Homologous,  598 
Terpenol,  601 
Terpin,  601 

hydrate,  601 
Terpinene,  596 
Terpineol,  601 
Terpinolene,  596 
Test,  Geitel's,  379 

Liebermann-Storch-Morawski,  379 
Renard's,  404 
Riche-Halphen,  72 

Teichmann,  738 

Uhlenhuth,  738 
Tetanolysin,  115 
Tetrabromofluorescein,  581 
Tetrabromoindirubin,  664 
Tetrachloroanisole,  543 
Tetrachloroethane,  102 
Tetrachloromethane,  101 
Tetracosane,  31 
Tetradecane,  31 
Tetrahydronaphthylamine,  614 
Tetrahydropyridines,  626 
Tetrahydropyrrole,  622 
Tetrahydroquinoline,  637 
Tetrahydroxyanthraquinones,  616 
Tetrahydroxybenzene,  546 
Tetrahydroxyflavonol,  668 
Tetrahydroxyrufenol,  666 
Tetraline,  102 

Tetralkylphosphonium  hydroxide,  202 
Tetramethylarsonium  compounds,  202 
Tetramethylbenzenes,  535 
Tetramethyldiaminotriphenylcarbinol,  607 
Tetramethyldiaminotriphenylmethane,  607 
Tetramethylene,  521 
Tetramethylenediamine,  214 
Tetramethylmethane,  35 
Tetramines,  Aromatic,  556 
Tetranitrodiglycerine,  184,  223 
Tetranitromethane,  198 
Tetrazo -compounds,  565 
Tetrazole,  623 
Tetroses,  429,  489 
Textile  fibres,  681 

Analysis  of  mixed,  704 

Chemical  identification  of,  703 

Commercial  weight  of,  704 

Conditioning  of,  704 

Drying  of,  723 

Dyeing  of,  717 

Dyeing  tests  on,  705 

Printing  of,  730 

Printing  tests  on,  707 

Tenacity  of,  701 
Textiles,  Dressing  of,  724 

Dyeing  of,  717,  721 

Fixing  of,  716 

Mercerisation  of,  728 
Thalline,  637 
Thebaine,  632 


INDEX 


769 


Theine,  369 
Theobromine,  368,  628 
Theophylline,  368 
Theory  of  dyeing,  708 

explosives,  215 

fractional  distillation,  3 

radicals,  14 

substitution,  15 

tanning,  586 

transposition,  648 

types,  14 

valency  ;  Baeyer's  tension,  88,  306,  521 
Thermo -oleometer,  Tortelli's,  376 
Thiazimes,  661 
Thiazine,  670 
Thiazole,  623 
Thiazones,  661 
Thioacetamide,  199,  357 
Thioacids,  361 
Thioalcohols,  195 
Thioaldehydes,  206 
Thioamides,  357,  359,  644 
Thioanhydrides,  351 
Thiobenzanilide,  560 
Thiocarbamide,  365 
Thiocarmine,  673 
Thiodiphenylamine,  647 
Thioethers,  195 
Thioflavin,  663 
Thioindigo,  664 
Thioketones,  210 
Thiols,  195 
Thionine,  647,  661 
Thiophene,  620 
Thiophenol,  538,  564 
Thiophosgene,  364 
Thioserine,  356 
Thiourea,  365 
Thiourethane,  365 
Thioxene,  620 
Thymenamine,  555 
Thymene,  593 
Thymol,  643 
Thymoquinone,  547 
Thyol,  84 
Thyroidin,  629 
Tintarron,  645 
Tobacco,  630 
Tolane,  609 
o-Tolidine,  605 
Toluene,  534 
Toluidines,  560 
Tolylenediamines,  561 
Tolyl  phenyl  ketones,  607 
Tolylphenylmethane,  606 
Tops,  683,  711,  717 
Tournesol,  668 
Tow,  687 
Toxalbumins,  734 
Toxins,  115 

Velocity  of  reaction  of,  116 
Trauzl's  lead  block,  262 
Triacetanilide,  560 
Trialkylphosphine  oxide,  202 
Trialkylphosphonium  hydroxide,  202 
Trianunes,  Aromatic,  556 
Triaminoazobenzene,  656 
Triaminotriphenylcarbincl,  607 
Triazoformoxime,  360 
Triazole,  623 
Tribromophenol,  543 
Tribromoresorcinol,  544 
Trichloroacetone,  98 
Trlchloromethane,  98 
II 


Trichlorophenol,  543 
Trichloropurine,  367 
Tricosane,  31 
Tridecane,  31 
Triethylamine,  202 
Triethylenediamine,  214 
Triethylsulphonium  hydroxide,  195 

iodide,  195 
Triformin,  373 
Triformol,  207 
Trihydroxybenzenes,  545 
Trihydroxybenzophenone,  606 
Trihydroxytriethylamine,  214 
Tri-iodomethane,  100 
Triketonamines,  210 
Trimethylacetyl  chloride,  319 
Trimethylamine,  97,  201 

hydrochloride,  97 
Trimethylbenzene,  91 
Trimethylbenzenes,  535 
Trimethylcarbinol,  181 
Trimethylcetylbenzene,  527 
Trimethylene,  87,  520 
Trimethylmethane,  35 

Trimethylphenylammonium  hydroxide,  556 
Trimethylpyridines,  625 
Trimethylsulphonium  iodide,  196 
Trinitrobenzene,  550 
Trinitrocellulose,  232 
Trinitroglycerine,  215,  223 
Trinitrohemellitheue,  548 
Trinitromesitylene,  548 
Trinitrophenol,  245,  562,  655 
Trinitropseudocumene,  548 
Trinitrotert.butyltoluene,  548 
Trinitrotert.butylxylene,  553 
Trinitrotoluenes,  551,  552 
Trinitroxylenes,  548 
Triolein,  298,  372 
Trional,  99,  629 
Trioses,  442 
Trioxymethylene,  207 
Tripalmitin,  372 
Triphenylamine,  560 
Triphenylmethane,  571,  607 
Triphenylmethyl,  608 
Tristearin,  185,  372 
Trithioketones,  210 
Tritopine,  632 
Tropacocaine,  629 
Tropseolins,  565,  656 
Tropanol,  632 
Tropene,  632 
Tropidine,  632 
Tropine,  631 
Tropinone,  632 
Tropon,  386,  737 
Tryptase,  112,  734 
Tumelina,  140 
Turmeric,  645 
Turpentine,  596 
Tussah  silk,  691,  696 
Tyndall  phenomenon,  01 
Types,  Multiple,  15 

Theory  of,  14 
Tyrosinase,  112 

UMBELLIFERONE,  584 
Undecane,  31 
Uramil,  368 
Urea,  1,  363 

Alkyl-derivatives  of,  364 

nitrate,  364 

Nitro-derivative  of,  364 

49 


INDEX 


Urease,  115 
Ureides,  364,  366 
Urethane,  363 
Uroacids,  366 
Urotropine,  157 

VALENCY,  Partial,  623 

Tension  theory  of,  88 
Valeraldehyde,  209 
Vanilla,  574 
Vanillin,  674 

Vaporimeter,  Geissler,  147 
Varnish,  374,  400 

Cold,  400 

Lithographers',  400 
Vaseline,  80 
Velocity  of  esterification,  22 

inversion,  441 
Veratrine,  628,  632 
Verdigris,  287 
Vermouth,  159J 
Veronal,  99,  629 
Vesuvine,  656 
Vigorite,  248 
Vinasse,  133,  157 
Vinegar,  280 

Adulteration  of,  284 

Analysis  of,  284 

Artificial,  284 

German  process,  282 

Luxemburg  process,  282 

Malt,  284 

Michaelis  process,  282 

mite,  281 

Wine,  284 

worms,  281 
Violamine,  674 
Violanthrene,  665 
Violet,  Acid,  674 

Alkali,  674 

Chrome,  660 

Ciba,  664 

Pormyl,  660 

Indanthrene,  665 

Lauth's,  661 

Methyl,  608,  660 

Victoria,  674 
Viscosimeter,  Engler's,  79 
Vitellin,  737 
Vulcanised  paper,  506 

WAGON-STILL,  66 
Wax,  Algse,  60 

Chinese,  181 

Japanese  vegetable,  290 

Mineral,  81,  85 

Montan,  81 
Waxes,  376 

Hydrolysis  of,  377 
Westphalite,  246 
Wetterdinamit,  231,  247 
Wheat,  162 

Composition  of,  490 
Wine,  155 

Alcohol-free,  150 

Analysis  of,  157 

Statistics  of,  157 
VVoad,  639 


Wood,  Bar,  669 

Brazil,  669 

Cam,  669 

Cuba,  668 

Log,  666 

Preservation  of,  532 

Red,  669 

Sandal,  669 

Yellow,  668 
Wood-pulp,  Chemical,  507,  511 

Mechanical,  507,  509 
Wool,  681 

Bleaching  of,  712 

Carbonisation  of,  682 

Carded,  681 

Chemical  properties  of,  683 

Combing,  681 

Dyeing  of,  717 

from  different  sheep,  681 

Statistics  of,  682 

XANTHINE,  368,  369 
Xanthogenamide,  365 
Xanthone,  606,  663 
Xeroform,  101 
Xylans,  429 
Xylenes,  527,  534 
Xylidines,  561 
Xylitol,  189,  428 
Xyloidin,  232 
Xyloquinone,'  547 
Xylose,  429,  431 

YEAST,  116,  121,  125,  171,  172 

Acclimatised,  127 
Frohberg,  171 
Logos,  171 
Pressed,  125 
Saaz,  171 
Wild,  171 
Yellow,  Acid,  656 
Acridine,  663 

Alizarin,  606,  657,  063,  072 
Anthracene,  663 
Carbazole,  672 
Ciba,  664 
Cibanone,  665 
Cuba,  668 
Diamine,  678 
Diamond,  657,  673 
Fast,  656 
Helindone,  665 
Indanthrene,  665 
Indian,  656,  663,  668 
Indigo,  664 
Metanil,  672 
Milling,  675 
Naphthol,  655 
Quinoline,  637,  663 
Sulphur  extra,  678 
Thiazole,  678 
Victoria,  655 

ZINC  alkyls,  32,  203 

lactate,  325 

Zymase,  111,  115,  116,  123 
Zymogen,  172 


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